clang  8.0.0svn
ExprConstant.cpp
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1 //===--- ExprConstant.cpp - Expression Constant Evaluator -----------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements the Expr constant evaluator.
11 //
12 // Constant expression evaluation produces four main results:
13 //
14 // * A success/failure flag indicating whether constant folding was successful.
15 // This is the 'bool' return value used by most of the code in this file. A
16 // 'false' return value indicates that constant folding has failed, and any
17 // appropriate diagnostic has already been produced.
18 //
19 // * An evaluated result, valid only if constant folding has not failed.
20 //
21 // * A flag indicating if evaluation encountered (unevaluated) side-effects.
22 // These arise in cases such as (sideEffect(), 0) and (sideEffect() || 1),
23 // where it is possible to determine the evaluated result regardless.
24 //
25 // * A set of notes indicating why the evaluation was not a constant expression
26 // (under the C++11 / C++1y rules only, at the moment), or, if folding failed
27 // too, why the expression could not be folded.
28 //
29 // If we are checking for a potential constant expression, failure to constant
30 // fold a potential constant sub-expression will be indicated by a 'false'
31 // return value (the expression could not be folded) and no diagnostic (the
32 // expression is not necessarily non-constant).
33 //
34 //===----------------------------------------------------------------------===//
35 
36 #include "clang/AST/APValue.h"
37 #include "clang/AST/ASTContext.h"
39 #include "clang/AST/ASTLambda.h"
40 #include "clang/AST/CharUnits.h"
41 #include "clang/AST/Expr.h"
42 #include "clang/AST/RecordLayout.h"
43 #include "clang/AST/StmtVisitor.h"
44 #include "clang/AST/TypeLoc.h"
45 #include "clang/Basic/Builtins.h"
46 #include "clang/Basic/TargetInfo.h"
47 #include "llvm/Support/raw_ostream.h"
48 #include <cstring>
49 #include <functional>
50 
51 #define DEBUG_TYPE "exprconstant"
52 
53 using namespace clang;
54 using llvm::APSInt;
55 using llvm::APFloat;
56 
57 static bool IsGlobalLValue(APValue::LValueBase B);
58 
59 namespace {
60  struct LValue;
61  struct CallStackFrame;
62  struct EvalInfo;
63 
64  static QualType getType(APValue::LValueBase B) {
65  if (!B) return QualType();
66  if (const ValueDecl *D = B.dyn_cast<const ValueDecl*>()) {
67  // FIXME: It's unclear where we're supposed to take the type from, and
68  // this actually matters for arrays of unknown bound. Eg:
69  //
70  // extern int arr[]; void f() { extern int arr[3]; };
71  // constexpr int *p = &arr[1]; // valid?
72  //
73  // For now, we take the array bound from the most recent declaration.
74  for (auto *Redecl = cast<ValueDecl>(D->getMostRecentDecl()); Redecl;
75  Redecl = cast_or_null<ValueDecl>(Redecl->getPreviousDecl())) {
76  QualType T = Redecl->getType();
77  if (!T->isIncompleteArrayType())
78  return T;
79  }
80  return D->getType();
81  }
82 
83  const Expr *Base = B.get<const Expr*>();
84 
85  // For a materialized temporary, the type of the temporary we materialized
86  // may not be the type of the expression.
87  if (const MaterializeTemporaryExpr *MTE =
88  dyn_cast<MaterializeTemporaryExpr>(Base)) {
91  const Expr *Temp = MTE->GetTemporaryExpr();
92  const Expr *Inner = Temp->skipRValueSubobjectAdjustments(CommaLHSs,
93  Adjustments);
94  // Keep any cv-qualifiers from the reference if we generated a temporary
95  // for it directly. Otherwise use the type after adjustment.
96  if (!Adjustments.empty())
97  return Inner->getType();
98  }
99 
100  return Base->getType();
101  }
102 
103  /// Get an LValue path entry, which is known to not be an array index, as a
104  /// field or base class.
105  static
108  Value.setFromOpaqueValue(E.BaseOrMember);
109  return Value;
110  }
111 
112  /// Get an LValue path entry, which is known to not be an array index, as a
113  /// field declaration.
114  static const FieldDecl *getAsField(APValue::LValuePathEntry E) {
115  return dyn_cast<FieldDecl>(getAsBaseOrMember(E).getPointer());
116  }
117  /// Get an LValue path entry, which is known to not be an array index, as a
118  /// base class declaration.
119  static const CXXRecordDecl *getAsBaseClass(APValue::LValuePathEntry E) {
120  return dyn_cast<CXXRecordDecl>(getAsBaseOrMember(E).getPointer());
121  }
122  /// Determine whether this LValue path entry for a base class names a virtual
123  /// base class.
124  static bool isVirtualBaseClass(APValue::LValuePathEntry E) {
125  return getAsBaseOrMember(E).getInt();
126  }
127 
128  /// Given a CallExpr, try to get the alloc_size attribute. May return null.
129  static const AllocSizeAttr *getAllocSizeAttr(const CallExpr *CE) {
130  const FunctionDecl *Callee = CE->getDirectCallee();
131  return Callee ? Callee->getAttr<AllocSizeAttr>() : nullptr;
132  }
133 
134  /// Attempts to unwrap a CallExpr (with an alloc_size attribute) from an Expr.
135  /// This will look through a single cast.
136  ///
137  /// Returns null if we couldn't unwrap a function with alloc_size.
138  static const CallExpr *tryUnwrapAllocSizeCall(const Expr *E) {
139  if (!E->getType()->isPointerType())
140  return nullptr;
141 
142  E = E->IgnoreParens();
143  // If we're doing a variable assignment from e.g. malloc(N), there will
144  // probably be a cast of some kind. In exotic cases, we might also see a
145  // top-level ExprWithCleanups. Ignore them either way.
146  if (const auto *EC = dyn_cast<ExprWithCleanups>(E))
147  E = EC->getSubExpr()->IgnoreParens();
148 
149  if (const auto *Cast = dyn_cast<CastExpr>(E))
150  E = Cast->getSubExpr()->IgnoreParens();
151 
152  if (const auto *CE = dyn_cast<CallExpr>(E))
153  return getAllocSizeAttr(CE) ? CE : nullptr;
154  return nullptr;
155  }
156 
157  /// Determines whether or not the given Base contains a call to a function
158  /// with the alloc_size attribute.
159  static bool isBaseAnAllocSizeCall(APValue::LValueBase Base) {
160  const auto *E = Base.dyn_cast<const Expr *>();
161  return E && E->getType()->isPointerType() && tryUnwrapAllocSizeCall(E);
162  }
163 
164  /// The bound to claim that an array of unknown bound has.
165  /// The value in MostDerivedArraySize is undefined in this case. So, set it
166  /// to an arbitrary value that's likely to loudly break things if it's used.
167  static const uint64_t AssumedSizeForUnsizedArray =
169 
170  /// Determines if an LValue with the given LValueBase will have an unsized
171  /// array in its designator.
172  /// Find the path length and type of the most-derived subobject in the given
173  /// path, and find the size of the containing array, if any.
174  static unsigned
175  findMostDerivedSubobject(ASTContext &Ctx, APValue::LValueBase Base,
177  uint64_t &ArraySize, QualType &Type, bool &IsArray,
178  bool &FirstEntryIsUnsizedArray) {
179  // This only accepts LValueBases from APValues, and APValues don't support
180  // arrays that lack size info.
181  assert(!isBaseAnAllocSizeCall(Base) &&
182  "Unsized arrays shouldn't appear here");
183  unsigned MostDerivedLength = 0;
184  Type = getType(Base);
185 
186  for (unsigned I = 0, N = Path.size(); I != N; ++I) {
187  if (Type->isArrayType()) {
188  const ArrayType *AT = Ctx.getAsArrayType(Type);
189  Type = AT->getElementType();
190  MostDerivedLength = I + 1;
191  IsArray = true;
192 
193  if (auto *CAT = dyn_cast<ConstantArrayType>(AT)) {
194  ArraySize = CAT->getSize().getZExtValue();
195  } else {
196  assert(I == 0 && "unexpected unsized array designator");
197  FirstEntryIsUnsizedArray = true;
198  ArraySize = AssumedSizeForUnsizedArray;
199  }
200  } else if (Type->isAnyComplexType()) {
201  const ComplexType *CT = Type->castAs<ComplexType>();
202  Type = CT->getElementType();
203  ArraySize = 2;
204  MostDerivedLength = I + 1;
205  IsArray = true;
206  } else if (const FieldDecl *FD = getAsField(Path[I])) {
207  Type = FD->getType();
208  ArraySize = 0;
209  MostDerivedLength = I + 1;
210  IsArray = false;
211  } else {
212  // Path[I] describes a base class.
213  ArraySize = 0;
214  IsArray = false;
215  }
216  }
217  return MostDerivedLength;
218  }
219 
220  // The order of this enum is important for diagnostics.
222  CSK_Base, CSK_Derived, CSK_Field, CSK_ArrayToPointer, CSK_ArrayIndex,
223  CSK_This, CSK_Real, CSK_Imag
224  };
225 
226  /// A path from a glvalue to a subobject of that glvalue.
227  struct SubobjectDesignator {
228  /// True if the subobject was named in a manner not supported by C++11. Such
229  /// lvalues can still be folded, but they are not core constant expressions
230  /// and we cannot perform lvalue-to-rvalue conversions on them.
231  unsigned Invalid : 1;
232 
233  /// Is this a pointer one past the end of an object?
234  unsigned IsOnePastTheEnd : 1;
235 
236  /// Indicator of whether the first entry is an unsized array.
237  unsigned FirstEntryIsAnUnsizedArray : 1;
238 
239  /// Indicator of whether the most-derived object is an array element.
240  unsigned MostDerivedIsArrayElement : 1;
241 
242  /// The length of the path to the most-derived object of which this is a
243  /// subobject.
244  unsigned MostDerivedPathLength : 28;
245 
246  /// The size of the array of which the most-derived object is an element.
247  /// This will always be 0 if the most-derived object is not an array
248  /// element. 0 is not an indicator of whether or not the most-derived object
249  /// is an array, however, because 0-length arrays are allowed.
250  ///
251  /// If the current array is an unsized array, the value of this is
252  /// undefined.
253  uint64_t MostDerivedArraySize;
254 
255  /// The type of the most derived object referred to by this address.
256  QualType MostDerivedType;
257 
258  typedef APValue::LValuePathEntry PathEntry;
259 
260  /// The entries on the path from the glvalue to the designated subobject.
262 
263  SubobjectDesignator() : Invalid(true) {}
264 
265  explicit SubobjectDesignator(QualType T)
266  : Invalid(false), IsOnePastTheEnd(false),
267  FirstEntryIsAnUnsizedArray(false), MostDerivedIsArrayElement(false),
268  MostDerivedPathLength(0), MostDerivedArraySize(0),
269  MostDerivedType(T) {}
270 
271  SubobjectDesignator(ASTContext &Ctx, const APValue &V)
272  : Invalid(!V.isLValue() || !V.hasLValuePath()), IsOnePastTheEnd(false),
273  FirstEntryIsAnUnsizedArray(false), MostDerivedIsArrayElement(false),
274  MostDerivedPathLength(0), MostDerivedArraySize(0) {
275  assert(V.isLValue() && "Non-LValue used to make an LValue designator?");
276  if (!Invalid) {
277  IsOnePastTheEnd = V.isLValueOnePastTheEnd();
278  ArrayRef<PathEntry> VEntries = V.getLValuePath();
279  Entries.insert(Entries.end(), VEntries.begin(), VEntries.end());
280  if (V.getLValueBase()) {
281  bool IsArray = false;
282  bool FirstIsUnsizedArray = false;
283  MostDerivedPathLength = findMostDerivedSubobject(
284  Ctx, V.getLValueBase(), V.getLValuePath(), MostDerivedArraySize,
285  MostDerivedType, IsArray, FirstIsUnsizedArray);
286  MostDerivedIsArrayElement = IsArray;
287  FirstEntryIsAnUnsizedArray = FirstIsUnsizedArray;
288  }
289  }
290  }
291 
292  void setInvalid() {
293  Invalid = true;
294  Entries.clear();
295  }
296 
297  /// Determine whether the most derived subobject is an array without a
298  /// known bound.
299  bool isMostDerivedAnUnsizedArray() const {
300  assert(!Invalid && "Calling this makes no sense on invalid designators");
301  return Entries.size() == 1 && FirstEntryIsAnUnsizedArray;
302  }
303 
304  /// Determine what the most derived array's size is. Results in an assertion
305  /// failure if the most derived array lacks a size.
306  uint64_t getMostDerivedArraySize() const {
307  assert(!isMostDerivedAnUnsizedArray() && "Unsized array has no size");
308  return MostDerivedArraySize;
309  }
310 
311  /// Determine whether this is a one-past-the-end pointer.
312  bool isOnePastTheEnd() const {
313  assert(!Invalid);
314  if (IsOnePastTheEnd)
315  return true;
316  if (!isMostDerivedAnUnsizedArray() && MostDerivedIsArrayElement &&
317  Entries[MostDerivedPathLength - 1].ArrayIndex == MostDerivedArraySize)
318  return true;
319  return false;
320  }
321 
322  /// Get the range of valid index adjustments in the form
323  /// {maximum value that can be subtracted from this pointer,
324  /// maximum value that can be added to this pointer}
325  std::pair<uint64_t, uint64_t> validIndexAdjustments() {
326  if (Invalid || isMostDerivedAnUnsizedArray())
327  return {0, 0};
328 
329  // [expr.add]p4: For the purposes of these operators, a pointer to a
330  // nonarray object behaves the same as a pointer to the first element of
331  // an array of length one with the type of the object as its element type.
332  bool IsArray = MostDerivedPathLength == Entries.size() &&
333  MostDerivedIsArrayElement;
334  uint64_t ArrayIndex =
335  IsArray ? Entries.back().ArrayIndex : (uint64_t)IsOnePastTheEnd;
336  uint64_t ArraySize =
337  IsArray ? getMostDerivedArraySize() : (uint64_t)1;
338  return {ArrayIndex, ArraySize - ArrayIndex};
339  }
340 
341  /// Check that this refers to a valid subobject.
342  bool isValidSubobject() const {
343  if (Invalid)
344  return false;
345  return !isOnePastTheEnd();
346  }
347  /// Check that this refers to a valid subobject, and if not, produce a
348  /// relevant diagnostic and set the designator as invalid.
349  bool checkSubobject(EvalInfo &Info, const Expr *E, CheckSubobjectKind CSK);
350 
351  /// Get the type of the designated object.
352  QualType getType(ASTContext &Ctx) const {
353  assert(!Invalid && "invalid designator has no subobject type");
354  return MostDerivedPathLength == Entries.size()
355  ? MostDerivedType
356  : Ctx.getRecordType(getAsBaseClass(Entries.back()));
357  }
358 
359  /// Update this designator to refer to the first element within this array.
360  void addArrayUnchecked(const ConstantArrayType *CAT) {
361  PathEntry Entry;
362  Entry.ArrayIndex = 0;
363  Entries.push_back(Entry);
364 
365  // This is a most-derived object.
366  MostDerivedType = CAT->getElementType();
367  MostDerivedIsArrayElement = true;
368  MostDerivedArraySize = CAT->getSize().getZExtValue();
369  MostDerivedPathLength = Entries.size();
370  }
371  /// Update this designator to refer to the first element within the array of
372  /// elements of type T. This is an array of unknown size.
373  void addUnsizedArrayUnchecked(QualType ElemTy) {
374  PathEntry Entry;
375  Entry.ArrayIndex = 0;
376  Entries.push_back(Entry);
377 
378  MostDerivedType = ElemTy;
379  MostDerivedIsArrayElement = true;
380  // The value in MostDerivedArraySize is undefined in this case. So, set it
381  // to an arbitrary value that's likely to loudly break things if it's
382  // used.
383  MostDerivedArraySize = AssumedSizeForUnsizedArray;
384  MostDerivedPathLength = Entries.size();
385  }
386  /// Update this designator to refer to the given base or member of this
387  /// object.
388  void addDeclUnchecked(const Decl *D, bool Virtual = false) {
389  PathEntry Entry;
390  APValue::BaseOrMemberType Value(D, Virtual);
391  Entry.BaseOrMember = Value.getOpaqueValue();
392  Entries.push_back(Entry);
393 
394  // If this isn't a base class, it's a new most-derived object.
395  if (const FieldDecl *FD = dyn_cast<FieldDecl>(D)) {
396  MostDerivedType = FD->getType();
397  MostDerivedIsArrayElement = false;
398  MostDerivedArraySize = 0;
399  MostDerivedPathLength = Entries.size();
400  }
401  }
402  /// Update this designator to refer to the given complex component.
403  void addComplexUnchecked(QualType EltTy, bool Imag) {
404  PathEntry Entry;
405  Entry.ArrayIndex = Imag;
406  Entries.push_back(Entry);
407 
408  // This is technically a most-derived object, though in practice this
409  // is unlikely to matter.
410  MostDerivedType = EltTy;
411  MostDerivedIsArrayElement = true;
412  MostDerivedArraySize = 2;
413  MostDerivedPathLength = Entries.size();
414  }
415  void diagnoseUnsizedArrayPointerArithmetic(EvalInfo &Info, const Expr *E);
416  void diagnosePointerArithmetic(EvalInfo &Info, const Expr *E,
417  const APSInt &N);
418  /// Add N to the address of this subobject.
419  void adjustIndex(EvalInfo &Info, const Expr *E, APSInt N) {
420  if (Invalid || !N) return;
421  uint64_t TruncatedN = N.extOrTrunc(64).getZExtValue();
422  if (isMostDerivedAnUnsizedArray()) {
423  diagnoseUnsizedArrayPointerArithmetic(Info, E);
424  // Can't verify -- trust that the user is doing the right thing (or if
425  // not, trust that the caller will catch the bad behavior).
426  // FIXME: Should we reject if this overflows, at least?
427  Entries.back().ArrayIndex += TruncatedN;
428  return;
429  }
430 
431  // [expr.add]p4: For the purposes of these operators, a pointer to a
432  // nonarray object behaves the same as a pointer to the first element of
433  // an array of length one with the type of the object as its element type.
434  bool IsArray = MostDerivedPathLength == Entries.size() &&
435  MostDerivedIsArrayElement;
436  uint64_t ArrayIndex =
437  IsArray ? Entries.back().ArrayIndex : (uint64_t)IsOnePastTheEnd;
438  uint64_t ArraySize =
439  IsArray ? getMostDerivedArraySize() : (uint64_t)1;
440 
441  if (N < -(int64_t)ArrayIndex || N > ArraySize - ArrayIndex) {
442  // Calculate the actual index in a wide enough type, so we can include
443  // it in the note.
444  N = N.extend(std::max<unsigned>(N.getBitWidth() + 1, 65));
445  (llvm::APInt&)N += ArrayIndex;
446  assert(N.ugt(ArraySize) && "bounds check failed for in-bounds index");
447  diagnosePointerArithmetic(Info, E, N);
448  setInvalid();
449  return;
450  }
451 
452  ArrayIndex += TruncatedN;
453  assert(ArrayIndex <= ArraySize &&
454  "bounds check succeeded for out-of-bounds index");
455 
456  if (IsArray)
457  Entries.back().ArrayIndex = ArrayIndex;
458  else
459  IsOnePastTheEnd = (ArrayIndex != 0);
460  }
461  };
462 
463  /// A stack frame in the constexpr call stack.
464  struct CallStackFrame {
465  EvalInfo &Info;
466 
467  /// Parent - The caller of this stack frame.
468  CallStackFrame *Caller;
469 
470  /// Callee - The function which was called.
471  const FunctionDecl *Callee;
472 
473  /// This - The binding for the this pointer in this call, if any.
474  const LValue *This;
475 
476  /// Arguments - Parameter bindings for this function call, indexed by
477  /// parameters' function scope indices.
478  APValue *Arguments;
479 
480  // Note that we intentionally use std::map here so that references to
481  // values are stable.
482  typedef std::pair<const void *, unsigned> MapKeyTy;
483  typedef std::map<MapKeyTy, APValue> MapTy;
484  /// Temporaries - Temporary lvalues materialized within this stack frame.
485  MapTy Temporaries;
486 
487  /// CallLoc - The location of the call expression for this call.
488  SourceLocation CallLoc;
489 
490  /// Index - The call index of this call.
491  unsigned Index;
492 
493  /// The stack of integers for tracking version numbers for temporaries.
494  SmallVector<unsigned, 2> TempVersionStack = {1};
495  unsigned CurTempVersion = TempVersionStack.back();
496 
497  unsigned getTempVersion() const { return TempVersionStack.back(); }
498 
499  void pushTempVersion() {
500  TempVersionStack.push_back(++CurTempVersion);
501  }
502 
503  void popTempVersion() {
504  TempVersionStack.pop_back();
505  }
506 
507  // FIXME: Adding this to every 'CallStackFrame' may have a nontrivial impact
508  // on the overall stack usage of deeply-recursing constexpr evaluataions.
509  // (We should cache this map rather than recomputing it repeatedly.)
510  // But let's try this and see how it goes; we can look into caching the map
511  // as a later change.
512 
513  /// LambdaCaptureFields - Mapping from captured variables/this to
514  /// corresponding data members in the closure class.
515  llvm::DenseMap<const VarDecl *, FieldDecl *> LambdaCaptureFields;
516  FieldDecl *LambdaThisCaptureField;
517 
518  CallStackFrame(EvalInfo &Info, SourceLocation CallLoc,
519  const FunctionDecl *Callee, const LValue *This,
520  APValue *Arguments);
521  ~CallStackFrame();
522 
523  // Return the temporary for Key whose version number is Version.
524  APValue *getTemporary(const void *Key, unsigned Version) {
525  MapKeyTy KV(Key, Version);
526  auto LB = Temporaries.lower_bound(KV);
527  if (LB != Temporaries.end() && LB->first == KV)
528  return &LB->second;
529  // Pair (Key,Version) wasn't found in the map. Check that no elements
530  // in the map have 'Key' as their key.
531  assert((LB == Temporaries.end() || LB->first.first != Key) &&
532  (LB == Temporaries.begin() || std::prev(LB)->first.first != Key) &&
533  "Element with key 'Key' found in map");
534  return nullptr;
535  }
536 
537  // Return the current temporary for Key in the map.
538  APValue *getCurrentTemporary(const void *Key) {
539  auto UB = Temporaries.upper_bound(MapKeyTy(Key, UINT_MAX));
540  if (UB != Temporaries.begin() && std::prev(UB)->first.first == Key)
541  return &std::prev(UB)->second;
542  return nullptr;
543  }
544 
545  // Return the version number of the current temporary for Key.
546  unsigned getCurrentTemporaryVersion(const void *Key) const {
547  auto UB = Temporaries.upper_bound(MapKeyTy(Key, UINT_MAX));
548  if (UB != Temporaries.begin() && std::prev(UB)->first.first == Key)
549  return std::prev(UB)->first.second;
550  return 0;
551  }
552 
553  APValue &createTemporary(const void *Key, bool IsLifetimeExtended);
554  };
555 
556  /// Temporarily override 'this'.
557  class ThisOverrideRAII {
558  public:
559  ThisOverrideRAII(CallStackFrame &Frame, const LValue *NewThis, bool Enable)
560  : Frame(Frame), OldThis(Frame.This) {
561  if (Enable)
562  Frame.This = NewThis;
563  }
564  ~ThisOverrideRAII() {
565  Frame.This = OldThis;
566  }
567  private:
568  CallStackFrame &Frame;
569  const LValue *OldThis;
570  };
571 
572  /// A partial diagnostic which we might know in advance that we are not going
573  /// to emit.
574  class OptionalDiagnostic {
576 
577  public:
578  explicit OptionalDiagnostic(PartialDiagnostic *Diag = nullptr)
579  : Diag(Diag) {}
580 
581  template<typename T>
582  OptionalDiagnostic &operator<<(const T &v) {
583  if (Diag)
584  *Diag << v;
585  return *this;
586  }
587 
588  OptionalDiagnostic &operator<<(const APSInt &I) {
589  if (Diag) {
590  SmallVector<char, 32> Buffer;
591  I.toString(Buffer);
592  *Diag << StringRef(Buffer.data(), Buffer.size());
593  }
594  return *this;
595  }
596 
597  OptionalDiagnostic &operator<<(const APFloat &F) {
598  if (Diag) {
599  // FIXME: Force the precision of the source value down so we don't
600  // print digits which are usually useless (we don't really care here if
601  // we truncate a digit by accident in edge cases). Ideally,
602  // APFloat::toString would automatically print the shortest
603  // representation which rounds to the correct value, but it's a bit
604  // tricky to implement.
605  unsigned precision =
606  llvm::APFloat::semanticsPrecision(F.getSemantics());
607  precision = (precision * 59 + 195) / 196;
608  SmallVector<char, 32> Buffer;
609  F.toString(Buffer, precision);
610  *Diag << StringRef(Buffer.data(), Buffer.size());
611  }
612  return *this;
613  }
614  };
615 
616  /// A cleanup, and a flag indicating whether it is lifetime-extended.
617  class Cleanup {
618  llvm::PointerIntPair<APValue*, 1, bool> Value;
619 
620  public:
621  Cleanup(APValue *Val, bool IsLifetimeExtended)
622  : Value(Val, IsLifetimeExtended) {}
623 
624  bool isLifetimeExtended() const { return Value.getInt(); }
625  void endLifetime() {
626  *Value.getPointer() = APValue();
627  }
628  };
629 
630  /// EvalInfo - This is a private struct used by the evaluator to capture
631  /// information about a subexpression as it is folded. It retains information
632  /// about the AST context, but also maintains information about the folded
633  /// expression.
634  ///
635  /// If an expression could be evaluated, it is still possible it is not a C
636  /// "integer constant expression" or constant expression. If not, this struct
637  /// captures information about how and why not.
638  ///
639  /// One bit of information passed *into* the request for constant folding
640  /// indicates whether the subexpression is "evaluated" or not according to C
641  /// rules. For example, the RHS of (0 && foo()) is not evaluated. We can
642  /// evaluate the expression regardless of what the RHS is, but C only allows
643  /// certain things in certain situations.
644  struct EvalInfo {
645  ASTContext &Ctx;
646 
647  /// EvalStatus - Contains information about the evaluation.
648  Expr::EvalStatus &EvalStatus;
649 
650  /// CurrentCall - The top of the constexpr call stack.
651  CallStackFrame *CurrentCall;
652 
653  /// CallStackDepth - The number of calls in the call stack right now.
654  unsigned CallStackDepth;
655 
656  /// NextCallIndex - The next call index to assign.
657  unsigned NextCallIndex;
658 
659  /// StepsLeft - The remaining number of evaluation steps we're permitted
660  /// to perform. This is essentially a limit for the number of statements
661  /// we will evaluate.
662  unsigned StepsLeft;
663 
664  /// BottomFrame - The frame in which evaluation started. This must be
665  /// initialized after CurrentCall and CallStackDepth.
666  CallStackFrame BottomFrame;
667 
668  /// A stack of values whose lifetimes end at the end of some surrounding
669  /// evaluation frame.
670  llvm::SmallVector<Cleanup, 16> CleanupStack;
671 
672  /// EvaluatingDecl - This is the declaration whose initializer is being
673  /// evaluated, if any.
674  APValue::LValueBase EvaluatingDecl;
675 
676  /// EvaluatingDeclValue - This is the value being constructed for the
677  /// declaration whose initializer is being evaluated, if any.
678  APValue *EvaluatingDeclValue;
679 
680  /// EvaluatingObject - Pair of the AST node that an lvalue represents and
681  /// the call index that that lvalue was allocated in.
682  typedef std::pair<APValue::LValueBase, std::pair<unsigned, unsigned>>
683  EvaluatingObject;
684 
685  /// EvaluatingConstructors - Set of objects that are currently being
686  /// constructed.
687  llvm::DenseSet<EvaluatingObject> EvaluatingConstructors;
688 
689  struct EvaluatingConstructorRAII {
690  EvalInfo &EI;
691  EvaluatingObject Object;
692  bool DidInsert;
693  EvaluatingConstructorRAII(EvalInfo &EI, EvaluatingObject Object)
694  : EI(EI), Object(Object) {
695  DidInsert = EI.EvaluatingConstructors.insert(Object).second;
696  }
697  ~EvaluatingConstructorRAII() {
698  if (DidInsert) EI.EvaluatingConstructors.erase(Object);
699  }
700  };
701 
702  bool isEvaluatingConstructor(APValue::LValueBase Decl, unsigned CallIndex,
703  unsigned Version) {
704  return EvaluatingConstructors.count(
705  EvaluatingObject(Decl, {CallIndex, Version}));
706  }
707 
708  /// The current array initialization index, if we're performing array
709  /// initialization.
710  uint64_t ArrayInitIndex = -1;
711 
712  /// HasActiveDiagnostic - Was the previous diagnostic stored? If so, further
713  /// notes attached to it will also be stored, otherwise they will not be.
714  bool HasActiveDiagnostic;
715 
716  /// Have we emitted a diagnostic explaining why we couldn't constant
717  /// fold (not just why it's not strictly a constant expression)?
718  bool HasFoldFailureDiagnostic;
719 
720  /// Whether or not we're currently speculatively evaluating.
721  bool IsSpeculativelyEvaluating;
722 
723  enum EvaluationMode {
724  /// Evaluate as a constant expression. Stop if we find that the expression
725  /// is not a constant expression.
726  EM_ConstantExpression,
727 
728  /// Evaluate as a potential constant expression. Keep going if we hit a
729  /// construct that we can't evaluate yet (because we don't yet know the
730  /// value of something) but stop if we hit something that could never be
731  /// a constant expression.
732  EM_PotentialConstantExpression,
733 
734  /// Fold the expression to a constant. Stop if we hit a side-effect that
735  /// we can't model.
736  EM_ConstantFold,
737 
738  /// Evaluate the expression looking for integer overflow and similar
739  /// issues. Don't worry about side-effects, and try to visit all
740  /// subexpressions.
741  EM_EvaluateForOverflow,
742 
743  /// Evaluate in any way we know how. Don't worry about side-effects that
744  /// can't be modeled.
745  EM_IgnoreSideEffects,
746 
747  /// Evaluate as a constant expression. Stop if we find that the expression
748  /// is not a constant expression. Some expressions can be retried in the
749  /// optimizer if we don't constant fold them here, but in an unevaluated
750  /// context we try to fold them immediately since the optimizer never
751  /// gets a chance to look at it.
752  EM_ConstantExpressionUnevaluated,
753 
754  /// Evaluate as a potential constant expression. Keep going if we hit a
755  /// construct that we can't evaluate yet (because we don't yet know the
756  /// value of something) but stop if we hit something that could never be
757  /// a constant expression. Some expressions can be retried in the
758  /// optimizer if we don't constant fold them here, but in an unevaluated
759  /// context we try to fold them immediately since the optimizer never
760  /// gets a chance to look at it.
761  EM_PotentialConstantExpressionUnevaluated,
762 
763  /// Evaluate as a constant expression. In certain scenarios, if:
764  /// - we find a MemberExpr with a base that can't be evaluated, or
765  /// - we find a variable initialized with a call to a function that has
766  /// the alloc_size attribute on it
767  /// then we may consider evaluation to have succeeded.
768  ///
769  /// In either case, the LValue returned shall have an invalid base; in the
770  /// former, the base will be the invalid MemberExpr, in the latter, the
771  /// base will be either the alloc_size CallExpr or a CastExpr wrapping
772  /// said CallExpr.
773  EM_OffsetFold,
774  } EvalMode;
775 
776  /// Are we checking whether the expression is a potential constant
777  /// expression?
778  bool checkingPotentialConstantExpression() const {
779  return EvalMode == EM_PotentialConstantExpression ||
780  EvalMode == EM_PotentialConstantExpressionUnevaluated;
781  }
782 
783  /// Are we checking an expression for overflow?
784  // FIXME: We should check for any kind of undefined or suspicious behavior
785  // in such constructs, not just overflow.
786  bool checkingForOverflow() { return EvalMode == EM_EvaluateForOverflow; }
787 
788  EvalInfo(const ASTContext &C, Expr::EvalStatus &S, EvaluationMode Mode)
789  : Ctx(const_cast<ASTContext &>(C)), EvalStatus(S), CurrentCall(nullptr),
790  CallStackDepth(0), NextCallIndex(1),
791  StepsLeft(getLangOpts().ConstexprStepLimit),
792  BottomFrame(*this, SourceLocation(), nullptr, nullptr, nullptr),
793  EvaluatingDecl((const ValueDecl *)nullptr),
794  EvaluatingDeclValue(nullptr), HasActiveDiagnostic(false),
795  HasFoldFailureDiagnostic(false), IsSpeculativelyEvaluating(false),
796  EvalMode(Mode) {}
797 
798  void setEvaluatingDecl(APValue::LValueBase Base, APValue &Value) {
799  EvaluatingDecl = Base;
800  EvaluatingDeclValue = &Value;
801  EvaluatingConstructors.insert({Base, {0, 0}});
802  }
803 
804  const LangOptions &getLangOpts() const { return Ctx.getLangOpts(); }
805 
806  bool CheckCallLimit(SourceLocation Loc) {
807  // Don't perform any constexpr calls (other than the call we're checking)
808  // when checking a potential constant expression.
809  if (checkingPotentialConstantExpression() && CallStackDepth > 1)
810  return false;
811  if (NextCallIndex == 0) {
812  // NextCallIndex has wrapped around.
813  FFDiag(Loc, diag::note_constexpr_call_limit_exceeded);
814  return false;
815  }
816  if (CallStackDepth <= getLangOpts().ConstexprCallDepth)
817  return true;
818  FFDiag(Loc, diag::note_constexpr_depth_limit_exceeded)
819  << getLangOpts().ConstexprCallDepth;
820  return false;
821  }
822 
823  CallStackFrame *getCallFrame(unsigned CallIndex) {
824  assert(CallIndex && "no call index in getCallFrame");
825  // We will eventually hit BottomFrame, which has Index 1, so Frame can't
826  // be null in this loop.
827  CallStackFrame *Frame = CurrentCall;
828  while (Frame->Index > CallIndex)
829  Frame = Frame->Caller;
830  return (Frame->Index == CallIndex) ? Frame : nullptr;
831  }
832 
833  bool nextStep(const Stmt *S) {
834  if (!StepsLeft) {
835  FFDiag(S->getBeginLoc(), diag::note_constexpr_step_limit_exceeded);
836  return false;
837  }
838  --StepsLeft;
839  return true;
840  }
841 
842  private:
843  /// Add a diagnostic to the diagnostics list.
844  PartialDiagnostic &addDiag(SourceLocation Loc, diag::kind DiagId) {
845  PartialDiagnostic PD(DiagId, Ctx.getDiagAllocator());
846  EvalStatus.Diag->push_back(std::make_pair(Loc, PD));
847  return EvalStatus.Diag->back().second;
848  }
849 
850  /// Add notes containing a call stack to the current point of evaluation.
851  void addCallStack(unsigned Limit);
852 
853  private:
854  OptionalDiagnostic Diag(SourceLocation Loc, diag::kind DiagId,
855  unsigned ExtraNotes, bool IsCCEDiag) {
856 
857  if (EvalStatus.Diag) {
858  // If we have a prior diagnostic, it will be noting that the expression
859  // isn't a constant expression. This diagnostic is more important,
860  // unless we require this evaluation to produce a constant expression.
861  //
862  // FIXME: We might want to show both diagnostics to the user in
863  // EM_ConstantFold mode.
864  if (!EvalStatus.Diag->empty()) {
865  switch (EvalMode) {
866  case EM_ConstantFold:
867  case EM_IgnoreSideEffects:
868  case EM_EvaluateForOverflow:
869  if (!HasFoldFailureDiagnostic)
870  break;
871  // We've already failed to fold something. Keep that diagnostic.
872  LLVM_FALLTHROUGH;
873  case EM_ConstantExpression:
874  case EM_PotentialConstantExpression:
875  case EM_ConstantExpressionUnevaluated:
876  case EM_PotentialConstantExpressionUnevaluated:
877  case EM_OffsetFold:
878  HasActiveDiagnostic = false;
879  return OptionalDiagnostic();
880  }
881  }
882 
883  unsigned CallStackNotes = CallStackDepth - 1;
884  unsigned Limit = Ctx.getDiagnostics().getConstexprBacktraceLimit();
885  if (Limit)
886  CallStackNotes = std::min(CallStackNotes, Limit + 1);
887  if (checkingPotentialConstantExpression())
888  CallStackNotes = 0;
889 
890  HasActiveDiagnostic = true;
891  HasFoldFailureDiagnostic = !IsCCEDiag;
892  EvalStatus.Diag->clear();
893  EvalStatus.Diag->reserve(1 + ExtraNotes + CallStackNotes);
894  addDiag(Loc, DiagId);
895  if (!checkingPotentialConstantExpression())
896  addCallStack(Limit);
897  return OptionalDiagnostic(&(*EvalStatus.Diag)[0].second);
898  }
899  HasActiveDiagnostic = false;
900  return OptionalDiagnostic();
901  }
902  public:
903  // Diagnose that the evaluation could not be folded (FF => FoldFailure)
904  OptionalDiagnostic
905  FFDiag(SourceLocation Loc,
906  diag::kind DiagId = diag::note_invalid_subexpr_in_const_expr,
907  unsigned ExtraNotes = 0) {
908  return Diag(Loc, DiagId, ExtraNotes, false);
909  }
910 
911  OptionalDiagnostic FFDiag(const Expr *E, diag::kind DiagId
912  = diag::note_invalid_subexpr_in_const_expr,
913  unsigned ExtraNotes = 0) {
914  if (EvalStatus.Diag)
915  return Diag(E->getExprLoc(), DiagId, ExtraNotes, /*IsCCEDiag*/false);
916  HasActiveDiagnostic = false;
917  return OptionalDiagnostic();
918  }
919 
920  /// Diagnose that the evaluation does not produce a C++11 core constant
921  /// expression.
922  ///
923  /// FIXME: Stop evaluating if we're in EM_ConstantExpression or
924  /// EM_PotentialConstantExpression mode and we produce one of these.
925  OptionalDiagnostic CCEDiag(SourceLocation Loc, diag::kind DiagId
926  = diag::note_invalid_subexpr_in_const_expr,
927  unsigned ExtraNotes = 0) {
928  // Don't override a previous diagnostic. Don't bother collecting
929  // diagnostics if we're evaluating for overflow.
930  if (!EvalStatus.Diag || !EvalStatus.Diag->empty()) {
931  HasActiveDiagnostic = false;
932  return OptionalDiagnostic();
933  }
934  return Diag(Loc, DiagId, ExtraNotes, true);
935  }
936  OptionalDiagnostic CCEDiag(const Expr *E, diag::kind DiagId
937  = diag::note_invalid_subexpr_in_const_expr,
938  unsigned ExtraNotes = 0) {
939  return CCEDiag(E->getExprLoc(), DiagId, ExtraNotes);
940  }
941  /// Add a note to a prior diagnostic.
942  OptionalDiagnostic Note(SourceLocation Loc, diag::kind DiagId) {
943  if (!HasActiveDiagnostic)
944  return OptionalDiagnostic();
945  return OptionalDiagnostic(&addDiag(Loc, DiagId));
946  }
947 
948  /// Add a stack of notes to a prior diagnostic.
949  void addNotes(ArrayRef<PartialDiagnosticAt> Diags) {
950  if (HasActiveDiagnostic) {
951  EvalStatus.Diag->insert(EvalStatus.Diag->end(),
952  Diags.begin(), Diags.end());
953  }
954  }
955 
956  /// Should we continue evaluation after encountering a side-effect that we
957  /// couldn't model?
958  bool keepEvaluatingAfterSideEffect() {
959  switch (EvalMode) {
960  case EM_PotentialConstantExpression:
961  case EM_PotentialConstantExpressionUnevaluated:
962  case EM_EvaluateForOverflow:
963  case EM_IgnoreSideEffects:
964  return true;
965 
966  case EM_ConstantExpression:
967  case EM_ConstantExpressionUnevaluated:
968  case EM_ConstantFold:
969  case EM_OffsetFold:
970  return false;
971  }
972  llvm_unreachable("Missed EvalMode case");
973  }
974 
975  /// Note that we have had a side-effect, and determine whether we should
976  /// keep evaluating.
977  bool noteSideEffect() {
978  EvalStatus.HasSideEffects = true;
979  return keepEvaluatingAfterSideEffect();
980  }
981 
982  /// Should we continue evaluation after encountering undefined behavior?
983  bool keepEvaluatingAfterUndefinedBehavior() {
984  switch (EvalMode) {
985  case EM_EvaluateForOverflow:
986  case EM_IgnoreSideEffects:
987  case EM_ConstantFold:
988  case EM_OffsetFold:
989  return true;
990 
991  case EM_PotentialConstantExpression:
992  case EM_PotentialConstantExpressionUnevaluated:
993  case EM_ConstantExpression:
994  case EM_ConstantExpressionUnevaluated:
995  return false;
996  }
997  llvm_unreachable("Missed EvalMode case");
998  }
999 
1000  /// Note that we hit something that was technically undefined behavior, but
1001  /// that we can evaluate past it (such as signed overflow or floating-point
1002  /// division by zero.)
1003  bool noteUndefinedBehavior() {
1004  EvalStatus.HasUndefinedBehavior = true;
1005  return keepEvaluatingAfterUndefinedBehavior();
1006  }
1007 
1008  /// Should we continue evaluation as much as possible after encountering a
1009  /// construct which can't be reduced to a value?
1010  bool keepEvaluatingAfterFailure() {
1011  if (!StepsLeft)
1012  return false;
1013 
1014  switch (EvalMode) {
1015  case EM_PotentialConstantExpression:
1016  case EM_PotentialConstantExpressionUnevaluated:
1017  case EM_EvaluateForOverflow:
1018  return true;
1019 
1020  case EM_ConstantExpression:
1021  case EM_ConstantExpressionUnevaluated:
1022  case EM_ConstantFold:
1023  case EM_IgnoreSideEffects:
1024  case EM_OffsetFold:
1025  return false;
1026  }
1027  llvm_unreachable("Missed EvalMode case");
1028  }
1029 
1030  /// Notes that we failed to evaluate an expression that other expressions
1031  /// directly depend on, and determine if we should keep evaluating. This
1032  /// should only be called if we actually intend to keep evaluating.
1033  ///
1034  /// Call noteSideEffect() instead if we may be able to ignore the value that
1035  /// we failed to evaluate, e.g. if we failed to evaluate Foo() in:
1036  ///
1037  /// (Foo(), 1) // use noteSideEffect
1038  /// (Foo() || true) // use noteSideEffect
1039  /// Foo() + 1 // use noteFailure
1040  LLVM_NODISCARD bool noteFailure() {
1041  // Failure when evaluating some expression often means there is some
1042  // subexpression whose evaluation was skipped. Therefore, (because we
1043  // don't track whether we skipped an expression when unwinding after an
1044  // evaluation failure) every evaluation failure that bubbles up from a
1045  // subexpression implies that a side-effect has potentially happened. We
1046  // skip setting the HasSideEffects flag to true until we decide to
1047  // continue evaluating after that point, which happens here.
1048  bool KeepGoing = keepEvaluatingAfterFailure();
1049  EvalStatus.HasSideEffects |= KeepGoing;
1050  return KeepGoing;
1051  }
1052 
1053  class ArrayInitLoopIndex {
1054  EvalInfo &Info;
1055  uint64_t OuterIndex;
1056 
1057  public:
1058  ArrayInitLoopIndex(EvalInfo &Info)
1059  : Info(Info), OuterIndex(Info.ArrayInitIndex) {
1060  Info.ArrayInitIndex = 0;
1061  }
1062  ~ArrayInitLoopIndex() { Info.ArrayInitIndex = OuterIndex; }
1063 
1064  operator uint64_t&() { return Info.ArrayInitIndex; }
1065  };
1066  };
1067 
1068  /// Object used to treat all foldable expressions as constant expressions.
1069  struct FoldConstant {
1070  EvalInfo &Info;
1071  bool Enabled;
1072  bool HadNoPriorDiags;
1073  EvalInfo::EvaluationMode OldMode;
1074 
1075  explicit FoldConstant(EvalInfo &Info, bool Enabled)
1076  : Info(Info),
1077  Enabled(Enabled),
1078  HadNoPriorDiags(Info.EvalStatus.Diag &&
1079  Info.EvalStatus.Diag->empty() &&
1080  !Info.EvalStatus.HasSideEffects),
1081  OldMode(Info.EvalMode) {
1082  if (Enabled &&
1083  (Info.EvalMode == EvalInfo::EM_ConstantExpression ||
1084  Info.EvalMode == EvalInfo::EM_ConstantExpressionUnevaluated))
1085  Info.EvalMode = EvalInfo::EM_ConstantFold;
1086  }
1087  void keepDiagnostics() { Enabled = false; }
1088  ~FoldConstant() {
1089  if (Enabled && HadNoPriorDiags && !Info.EvalStatus.Diag->empty() &&
1090  !Info.EvalStatus.HasSideEffects)
1091  Info.EvalStatus.Diag->clear();
1092  Info.EvalMode = OldMode;
1093  }
1094  };
1095 
1096  /// RAII object used to treat the current evaluation as the correct pointer
1097  /// offset fold for the current EvalMode
1098  struct FoldOffsetRAII {
1099  EvalInfo &Info;
1100  EvalInfo::EvaluationMode OldMode;
1101  explicit FoldOffsetRAII(EvalInfo &Info)
1102  : Info(Info), OldMode(Info.EvalMode) {
1103  if (!Info.checkingPotentialConstantExpression())
1104  Info.EvalMode = EvalInfo::EM_OffsetFold;
1105  }
1106 
1107  ~FoldOffsetRAII() { Info.EvalMode = OldMode; }
1108  };
1109 
1110  /// RAII object used to optionally suppress diagnostics and side-effects from
1111  /// a speculative evaluation.
1112  class SpeculativeEvaluationRAII {
1113  EvalInfo *Info = nullptr;
1114  Expr::EvalStatus OldStatus;
1115  bool OldIsSpeculativelyEvaluating;
1116 
1117  void moveFromAndCancel(SpeculativeEvaluationRAII &&Other) {
1118  Info = Other.Info;
1119  OldStatus = Other.OldStatus;
1120  OldIsSpeculativelyEvaluating = Other.OldIsSpeculativelyEvaluating;
1121  Other.Info = nullptr;
1122  }
1123 
1124  void maybeRestoreState() {
1125  if (!Info)
1126  return;
1127 
1128  Info->EvalStatus = OldStatus;
1129  Info->IsSpeculativelyEvaluating = OldIsSpeculativelyEvaluating;
1130  }
1131 
1132  public:
1133  SpeculativeEvaluationRAII() = default;
1134 
1135  SpeculativeEvaluationRAII(
1136  EvalInfo &Info, SmallVectorImpl<PartialDiagnosticAt> *NewDiag = nullptr)
1137  : Info(&Info), OldStatus(Info.EvalStatus),
1138  OldIsSpeculativelyEvaluating(Info.IsSpeculativelyEvaluating) {
1139  Info.EvalStatus.Diag = NewDiag;
1140  Info.IsSpeculativelyEvaluating = true;
1141  }
1142 
1143  SpeculativeEvaluationRAII(const SpeculativeEvaluationRAII &Other) = delete;
1144  SpeculativeEvaluationRAII(SpeculativeEvaluationRAII &&Other) {
1145  moveFromAndCancel(std::move(Other));
1146  }
1147 
1148  SpeculativeEvaluationRAII &operator=(SpeculativeEvaluationRAII &&Other) {
1149  maybeRestoreState();
1150  moveFromAndCancel(std::move(Other));
1151  return *this;
1152  }
1153 
1154  ~SpeculativeEvaluationRAII() { maybeRestoreState(); }
1155  };
1156 
1157  /// RAII object wrapping a full-expression or block scope, and handling
1158  /// the ending of the lifetime of temporaries created within it.
1159  template<bool IsFullExpression>
1160  class ScopeRAII {
1161  EvalInfo &Info;
1162  unsigned OldStackSize;
1163  public:
1164  ScopeRAII(EvalInfo &Info)
1165  : Info(Info), OldStackSize(Info.CleanupStack.size()) {
1166  // Push a new temporary version. This is needed to distinguish between
1167  // temporaries created in different iterations of a loop.
1168  Info.CurrentCall->pushTempVersion();
1169  }
1170  ~ScopeRAII() {
1171  // Body moved to a static method to encourage the compiler to inline away
1172  // instances of this class.
1173  cleanup(Info, OldStackSize);
1174  Info.CurrentCall->popTempVersion();
1175  }
1176  private:
1177  static void cleanup(EvalInfo &Info, unsigned OldStackSize) {
1178  unsigned NewEnd = OldStackSize;
1179  for (unsigned I = OldStackSize, N = Info.CleanupStack.size();
1180  I != N; ++I) {
1181  if (IsFullExpression && Info.CleanupStack[I].isLifetimeExtended()) {
1182  // Full-expression cleanup of a lifetime-extended temporary: nothing
1183  // to do, just move this cleanup to the right place in the stack.
1184  std::swap(Info.CleanupStack[I], Info.CleanupStack[NewEnd]);
1185  ++NewEnd;
1186  } else {
1187  // End the lifetime of the object.
1188  Info.CleanupStack[I].endLifetime();
1189  }
1190  }
1191  Info.CleanupStack.erase(Info.CleanupStack.begin() + NewEnd,
1192  Info.CleanupStack.end());
1193  }
1194  };
1195  typedef ScopeRAII<false> BlockScopeRAII;
1196  typedef ScopeRAII<true> FullExpressionRAII;
1197 }
1198 
1199 bool SubobjectDesignator::checkSubobject(EvalInfo &Info, const Expr *E,
1200  CheckSubobjectKind CSK) {
1201  if (Invalid)
1202  return false;
1203  if (isOnePastTheEnd()) {
1204  Info.CCEDiag(E, diag::note_constexpr_past_end_subobject)
1205  << CSK;
1206  setInvalid();
1207  return false;
1208  }
1209  // Note, we do not diagnose if isMostDerivedAnUnsizedArray(), because there
1210  // must actually be at least one array element; even a VLA cannot have a
1211  // bound of zero. And if our index is nonzero, we already had a CCEDiag.
1212  return true;
1213 }
1214 
1215 void SubobjectDesignator::diagnoseUnsizedArrayPointerArithmetic(EvalInfo &Info,
1216  const Expr *E) {
1217  Info.CCEDiag(E, diag::note_constexpr_unsized_array_indexed);
1218  // Do not set the designator as invalid: we can represent this situation,
1219  // and correct handling of __builtin_object_size requires us to do so.
1220 }
1221 
1222 void SubobjectDesignator::diagnosePointerArithmetic(EvalInfo &Info,
1223  const Expr *E,
1224  const APSInt &N) {
1225  // If we're complaining, we must be able to statically determine the size of
1226  // the most derived array.
1227  if (MostDerivedPathLength == Entries.size() && MostDerivedIsArrayElement)
1228  Info.CCEDiag(E, diag::note_constexpr_array_index)
1229  << N << /*array*/ 0
1230  << static_cast<unsigned>(getMostDerivedArraySize());
1231  else
1232  Info.CCEDiag(E, diag::note_constexpr_array_index)
1233  << N << /*non-array*/ 1;
1234  setInvalid();
1235 }
1236 
1237 CallStackFrame::CallStackFrame(EvalInfo &Info, SourceLocation CallLoc,
1238  const FunctionDecl *Callee, const LValue *This,
1239  APValue *Arguments)
1240  : Info(Info), Caller(Info.CurrentCall), Callee(Callee), This(This),
1241  Arguments(Arguments), CallLoc(CallLoc), Index(Info.NextCallIndex++) {
1242  Info.CurrentCall = this;
1243  ++Info.CallStackDepth;
1244 }
1245 
1246 CallStackFrame::~CallStackFrame() {
1247  assert(Info.CurrentCall == this && "calls retired out of order");
1248  --Info.CallStackDepth;
1249  Info.CurrentCall = Caller;
1250 }
1251 
1252 APValue &CallStackFrame::createTemporary(const void *Key,
1253  bool IsLifetimeExtended) {
1254  unsigned Version = Info.CurrentCall->getTempVersion();
1255  APValue &Result = Temporaries[MapKeyTy(Key, Version)];
1256  assert(Result.isUninit() && "temporary created multiple times");
1257  Info.CleanupStack.push_back(Cleanup(&Result, IsLifetimeExtended));
1258  return Result;
1259 }
1260 
1261 static void describeCall(CallStackFrame *Frame, raw_ostream &Out);
1262 
1263 void EvalInfo::addCallStack(unsigned Limit) {
1264  // Determine which calls to skip, if any.
1265  unsigned ActiveCalls = CallStackDepth - 1;
1266  unsigned SkipStart = ActiveCalls, SkipEnd = SkipStart;
1267  if (Limit && Limit < ActiveCalls) {
1268  SkipStart = Limit / 2 + Limit % 2;
1269  SkipEnd = ActiveCalls - Limit / 2;
1270  }
1271 
1272  // Walk the call stack and add the diagnostics.
1273  unsigned CallIdx = 0;
1274  for (CallStackFrame *Frame = CurrentCall; Frame != &BottomFrame;
1275  Frame = Frame->Caller, ++CallIdx) {
1276  // Skip this call?
1277  if (CallIdx >= SkipStart && CallIdx < SkipEnd) {
1278  if (CallIdx == SkipStart) {
1279  // Note that we're skipping calls.
1280  addDiag(Frame->CallLoc, diag::note_constexpr_calls_suppressed)
1281  << unsigned(ActiveCalls - Limit);
1282  }
1283  continue;
1284  }
1285 
1286  // Use a different note for an inheriting constructor, because from the
1287  // user's perspective it's not really a function at all.
1288  if (auto *CD = dyn_cast_or_null<CXXConstructorDecl>(Frame->Callee)) {
1289  if (CD->isInheritingConstructor()) {
1290  addDiag(Frame->CallLoc, diag::note_constexpr_inherited_ctor_call_here)
1291  << CD->getParent();
1292  continue;
1293  }
1294  }
1295 
1296  SmallVector<char, 128> Buffer;
1297  llvm::raw_svector_ostream Out(Buffer);
1298  describeCall(Frame, Out);
1299  addDiag(Frame->CallLoc, diag::note_constexpr_call_here) << Out.str();
1300  }
1301 }
1302 
1303 namespace {
1304  struct ComplexValue {
1305  private:
1306  bool IsInt;
1307 
1308  public:
1309  APSInt IntReal, IntImag;
1310  APFloat FloatReal, FloatImag;
1311 
1312  ComplexValue() : FloatReal(APFloat::Bogus()), FloatImag(APFloat::Bogus()) {}
1313 
1314  void makeComplexFloat() { IsInt = false; }
1315  bool isComplexFloat() const { return !IsInt; }
1316  APFloat &getComplexFloatReal() { return FloatReal; }
1317  APFloat &getComplexFloatImag() { return FloatImag; }
1318 
1319  void makeComplexInt() { IsInt = true; }
1320  bool isComplexInt() const { return IsInt; }
1321  APSInt &getComplexIntReal() { return IntReal; }
1322  APSInt &getComplexIntImag() { return IntImag; }
1323 
1324  void moveInto(APValue &v) const {
1325  if (isComplexFloat())
1326  v = APValue(FloatReal, FloatImag);
1327  else
1328  v = APValue(IntReal, IntImag);
1329  }
1330  void setFrom(const APValue &v) {
1331  assert(v.isComplexFloat() || v.isComplexInt());
1332  if (v.isComplexFloat()) {
1333  makeComplexFloat();
1334  FloatReal = v.getComplexFloatReal();
1335  FloatImag = v.getComplexFloatImag();
1336  } else {
1337  makeComplexInt();
1338  IntReal = v.getComplexIntReal();
1339  IntImag = v.getComplexIntImag();
1340  }
1341  }
1342  };
1343 
1344  struct LValue {
1345  APValue::LValueBase Base;
1346  CharUnits Offset;
1347  SubobjectDesignator Designator;
1348  bool IsNullPtr : 1;
1349  bool InvalidBase : 1;
1350 
1351  const APValue::LValueBase getLValueBase() const { return Base; }
1352  CharUnits &getLValueOffset() { return Offset; }
1353  const CharUnits &getLValueOffset() const { return Offset; }
1354  SubobjectDesignator &getLValueDesignator() { return Designator; }
1355  const SubobjectDesignator &getLValueDesignator() const { return Designator;}
1356  bool isNullPointer() const { return IsNullPtr;}
1357 
1358  unsigned getLValueCallIndex() const { return Base.getCallIndex(); }
1359  unsigned getLValueVersion() const { return Base.getVersion(); }
1360 
1361  void moveInto(APValue &V) const {
1362  if (Designator.Invalid)
1363  V = APValue(Base, Offset, APValue::NoLValuePath(), IsNullPtr);
1364  else {
1365  assert(!InvalidBase && "APValues can't handle invalid LValue bases");
1366  V = APValue(Base, Offset, Designator.Entries,
1367  Designator.IsOnePastTheEnd, IsNullPtr);
1368  }
1369  }
1370  void setFrom(ASTContext &Ctx, const APValue &V) {
1371  assert(V.isLValue() && "Setting LValue from a non-LValue?");
1372  Base = V.getLValueBase();
1373  Offset = V.getLValueOffset();
1374  InvalidBase = false;
1375  Designator = SubobjectDesignator(Ctx, V);
1376  IsNullPtr = V.isNullPointer();
1377  }
1378 
1379  void set(APValue::LValueBase B, bool BInvalid = false) {
1380 #ifndef NDEBUG
1381  // We only allow a few types of invalid bases. Enforce that here.
1382  if (BInvalid) {
1383  const auto *E = B.get<const Expr *>();
1384  assert((isa<MemberExpr>(E) || tryUnwrapAllocSizeCall(E)) &&
1385  "Unexpected type of invalid base");
1386  }
1387 #endif
1388 
1389  Base = B;
1390  Offset = CharUnits::fromQuantity(0);
1391  InvalidBase = BInvalid;
1392  Designator = SubobjectDesignator(getType(B));
1393  IsNullPtr = false;
1394  }
1395 
1396  void setNull(QualType PointerTy, uint64_t TargetVal) {
1397  Base = (Expr *)nullptr;
1398  Offset = CharUnits::fromQuantity(TargetVal);
1399  InvalidBase = false;
1400  Designator = SubobjectDesignator(PointerTy->getPointeeType());
1401  IsNullPtr = true;
1402  }
1403 
1404  void setInvalid(APValue::LValueBase B, unsigned I = 0) {
1405  set(B, true);
1406  }
1407 
1408  // Check that this LValue is not based on a null pointer. If it is, produce
1409  // a diagnostic and mark the designator as invalid.
1410  bool checkNullPointer(EvalInfo &Info, const Expr *E,
1411  CheckSubobjectKind CSK) {
1412  if (Designator.Invalid)
1413  return false;
1414  if (IsNullPtr) {
1415  Info.CCEDiag(E, diag::note_constexpr_null_subobject)
1416  << CSK;
1417  Designator.setInvalid();
1418  return false;
1419  }
1420  return true;
1421  }
1422 
1423  // Check this LValue refers to an object. If not, set the designator to be
1424  // invalid and emit a diagnostic.
1425  bool checkSubobject(EvalInfo &Info, const Expr *E, CheckSubobjectKind CSK) {
1426  return (CSK == CSK_ArrayToPointer || checkNullPointer(Info, E, CSK)) &&
1427  Designator.checkSubobject(Info, E, CSK);
1428  }
1429 
1430  void addDecl(EvalInfo &Info, const Expr *E,
1431  const Decl *D, bool Virtual = false) {
1432  if (checkSubobject(Info, E, isa<FieldDecl>(D) ? CSK_Field : CSK_Base))
1433  Designator.addDeclUnchecked(D, Virtual);
1434  }
1435  void addUnsizedArray(EvalInfo &Info, const Expr *E, QualType ElemTy) {
1436  if (!Designator.Entries.empty()) {
1437  Info.CCEDiag(E, diag::note_constexpr_unsupported_unsized_array);
1438  Designator.setInvalid();
1439  return;
1440  }
1441  if (checkSubobject(Info, E, CSK_ArrayToPointer)) {
1442  assert(getType(Base)->isPointerType() || getType(Base)->isArrayType());
1443  Designator.FirstEntryIsAnUnsizedArray = true;
1444  Designator.addUnsizedArrayUnchecked(ElemTy);
1445  }
1446  }
1447  void addArray(EvalInfo &Info, const Expr *E, const ConstantArrayType *CAT) {
1448  if (checkSubobject(Info, E, CSK_ArrayToPointer))
1449  Designator.addArrayUnchecked(CAT);
1450  }
1451  void addComplex(EvalInfo &Info, const Expr *E, QualType EltTy, bool Imag) {
1452  if (checkSubobject(Info, E, Imag ? CSK_Imag : CSK_Real))
1453  Designator.addComplexUnchecked(EltTy, Imag);
1454  }
1455  void clearIsNullPointer() {
1456  IsNullPtr = false;
1457  }
1458  void adjustOffsetAndIndex(EvalInfo &Info, const Expr *E,
1459  const APSInt &Index, CharUnits ElementSize) {
1460  // An index of 0 has no effect. (In C, adding 0 to a null pointer is UB,
1461  // but we're not required to diagnose it and it's valid in C++.)
1462  if (!Index)
1463  return;
1464 
1465  // Compute the new offset in the appropriate width, wrapping at 64 bits.
1466  // FIXME: When compiling for a 32-bit target, we should use 32-bit
1467  // offsets.
1468  uint64_t Offset64 = Offset.getQuantity();
1469  uint64_t ElemSize64 = ElementSize.getQuantity();
1470  uint64_t Index64 = Index.extOrTrunc(64).getZExtValue();
1471  Offset = CharUnits::fromQuantity(Offset64 + ElemSize64 * Index64);
1472 
1473  if (checkNullPointer(Info, E, CSK_ArrayIndex))
1474  Designator.adjustIndex(Info, E, Index);
1475  clearIsNullPointer();
1476  }
1477  void adjustOffset(CharUnits N) {
1478  Offset += N;
1479  if (N.getQuantity())
1480  clearIsNullPointer();
1481  }
1482  };
1483 
1484  struct MemberPtr {
1485  MemberPtr() {}
1486  explicit MemberPtr(const ValueDecl *Decl) :
1487  DeclAndIsDerivedMember(Decl, false), Path() {}
1488 
1489  /// The member or (direct or indirect) field referred to by this member
1490  /// pointer, or 0 if this is a null member pointer.
1491  const ValueDecl *getDecl() const {
1492  return DeclAndIsDerivedMember.getPointer();
1493  }
1494  /// Is this actually a member of some type derived from the relevant class?
1495  bool isDerivedMember() const {
1496  return DeclAndIsDerivedMember.getInt();
1497  }
1498  /// Get the class which the declaration actually lives in.
1499  const CXXRecordDecl *getContainingRecord() const {
1500  return cast<CXXRecordDecl>(
1501  DeclAndIsDerivedMember.getPointer()->getDeclContext());
1502  }
1503 
1504  void moveInto(APValue &V) const {
1505  V = APValue(getDecl(), isDerivedMember(), Path);
1506  }
1507  void setFrom(const APValue &V) {
1508  assert(V.isMemberPointer());
1509  DeclAndIsDerivedMember.setPointer(V.getMemberPointerDecl());
1510  DeclAndIsDerivedMember.setInt(V.isMemberPointerToDerivedMember());
1511  Path.clear();
1513  Path.insert(Path.end(), P.begin(), P.end());
1514  }
1515 
1516  /// DeclAndIsDerivedMember - The member declaration, and a flag indicating
1517  /// whether the member is a member of some class derived from the class type
1518  /// of the member pointer.
1519  llvm::PointerIntPair<const ValueDecl*, 1, bool> DeclAndIsDerivedMember;
1520  /// Path - The path of base/derived classes from the member declaration's
1521  /// class (exclusive) to the class type of the member pointer (inclusive).
1523 
1524  /// Perform a cast towards the class of the Decl (either up or down the
1525  /// hierarchy).
1526  bool castBack(const CXXRecordDecl *Class) {
1527  assert(!Path.empty());
1528  const CXXRecordDecl *Expected;
1529  if (Path.size() >= 2)
1530  Expected = Path[Path.size() - 2];
1531  else
1532  Expected = getContainingRecord();
1533  if (Expected->getCanonicalDecl() != Class->getCanonicalDecl()) {
1534  // C++11 [expr.static.cast]p12: In a conversion from (D::*) to (B::*),
1535  // if B does not contain the original member and is not a base or
1536  // derived class of the class containing the original member, the result
1537  // of the cast is undefined.
1538  // C++11 [conv.mem]p2 does not cover this case for a cast from (B::*) to
1539  // (D::*). We consider that to be a language defect.
1540  return false;
1541  }
1542  Path.pop_back();
1543  return true;
1544  }
1545  /// Perform a base-to-derived member pointer cast.
1546  bool castToDerived(const CXXRecordDecl *Derived) {
1547  if (!getDecl())
1548  return true;
1549  if (!isDerivedMember()) {
1550  Path.push_back(Derived);
1551  return true;
1552  }
1553  if (!castBack(Derived))
1554  return false;
1555  if (Path.empty())
1556  DeclAndIsDerivedMember.setInt(false);
1557  return true;
1558  }
1559  /// Perform a derived-to-base member pointer cast.
1560  bool castToBase(const CXXRecordDecl *Base) {
1561  if (!getDecl())
1562  return true;
1563  if (Path.empty())
1564  DeclAndIsDerivedMember.setInt(true);
1565  if (isDerivedMember()) {
1566  Path.push_back(Base);
1567  return true;
1568  }
1569  return castBack(Base);
1570  }
1571  };
1572 
1573  /// Compare two member pointers, which are assumed to be of the same type.
1574  static bool operator==(const MemberPtr &LHS, const MemberPtr &RHS) {
1575  if (!LHS.getDecl() || !RHS.getDecl())
1576  return !LHS.getDecl() && !RHS.getDecl();
1577  if (LHS.getDecl()->getCanonicalDecl() != RHS.getDecl()->getCanonicalDecl())
1578  return false;
1579  return LHS.Path == RHS.Path;
1580  }
1581 }
1582 
1583 static bool Evaluate(APValue &Result, EvalInfo &Info, const Expr *E);
1584 static bool EvaluateInPlace(APValue &Result, EvalInfo &Info,
1585  const LValue &This, const Expr *E,
1586  bool AllowNonLiteralTypes = false);
1587 static bool EvaluateLValue(const Expr *E, LValue &Result, EvalInfo &Info,
1588  bool InvalidBaseOK = false);
1589 static bool EvaluatePointer(const Expr *E, LValue &Result, EvalInfo &Info,
1590  bool InvalidBaseOK = false);
1591 static bool EvaluateMemberPointer(const Expr *E, MemberPtr &Result,
1592  EvalInfo &Info);
1593 static bool EvaluateTemporary(const Expr *E, LValue &Result, EvalInfo &Info);
1594 static bool EvaluateInteger(const Expr *E, APSInt &Result, EvalInfo &Info);
1595 static bool EvaluateIntegerOrLValue(const Expr *E, APValue &Result,
1596  EvalInfo &Info);
1597 static bool EvaluateFloat(const Expr *E, APFloat &Result, EvalInfo &Info);
1598 static bool EvaluateComplex(const Expr *E, ComplexValue &Res, EvalInfo &Info);
1599 static bool EvaluateAtomic(const Expr *E, const LValue *This, APValue &Result,
1600  EvalInfo &Info);
1601 static bool EvaluateAsRValue(EvalInfo &Info, const Expr *E, APValue &Result);
1602 
1603 //===----------------------------------------------------------------------===//
1604 // Misc utilities
1605 //===----------------------------------------------------------------------===//
1606 
1607 /// A helper function to create a temporary and set an LValue.
1608 template <class KeyTy>
1609 static APValue &createTemporary(const KeyTy *Key, bool IsLifetimeExtended,
1610  LValue &LV, CallStackFrame &Frame) {
1611  LV.set({Key, Frame.Info.CurrentCall->Index,
1612  Frame.Info.CurrentCall->getTempVersion()});
1613  return Frame.createTemporary(Key, IsLifetimeExtended);
1614 }
1615 
1616 /// Negate an APSInt in place, converting it to a signed form if necessary, and
1617 /// preserving its value (by extending by up to one bit as needed).
1618 static void negateAsSigned(APSInt &Int) {
1619  if (Int.isUnsigned() || Int.isMinSignedValue()) {
1620  Int = Int.extend(Int.getBitWidth() + 1);
1621  Int.setIsSigned(true);
1622  }
1623  Int = -Int;
1624 }
1625 
1626 /// Produce a string describing the given constexpr call.
1627 static void describeCall(CallStackFrame *Frame, raw_ostream &Out) {
1628  unsigned ArgIndex = 0;
1629  bool IsMemberCall = isa<CXXMethodDecl>(Frame->Callee) &&
1630  !isa<CXXConstructorDecl>(Frame->Callee) &&
1631  cast<CXXMethodDecl>(Frame->Callee)->isInstance();
1632 
1633  if (!IsMemberCall)
1634  Out << *Frame->Callee << '(';
1635 
1636  if (Frame->This && IsMemberCall) {
1637  APValue Val;
1638  Frame->This->moveInto(Val);
1639  Val.printPretty(Out, Frame->Info.Ctx,
1640  Frame->This->Designator.MostDerivedType);
1641  // FIXME: Add parens around Val if needed.
1642  Out << "->" << *Frame->Callee << '(';
1643  IsMemberCall = false;
1644  }
1645 
1646  for (FunctionDecl::param_const_iterator I = Frame->Callee->param_begin(),
1647  E = Frame->Callee->param_end(); I != E; ++I, ++ArgIndex) {
1648  if (ArgIndex > (unsigned)IsMemberCall)
1649  Out << ", ";
1650 
1651  const ParmVarDecl *Param = *I;
1652  const APValue &Arg = Frame->Arguments[ArgIndex];
1653  Arg.printPretty(Out, Frame->Info.Ctx, Param->getType());
1654 
1655  if (ArgIndex == 0 && IsMemberCall)
1656  Out << "->" << *Frame->Callee << '(';
1657  }
1658 
1659  Out << ')';
1660 }
1661 
1662 /// Evaluate an expression to see if it had side-effects, and discard its
1663 /// result.
1664 /// \return \c true if the caller should keep evaluating.
1665 static bool EvaluateIgnoredValue(EvalInfo &Info, const Expr *E) {
1666  APValue Scratch;
1667  if (!Evaluate(Scratch, Info, E))
1668  // We don't need the value, but we might have skipped a side effect here.
1669  return Info.noteSideEffect();
1670  return true;
1671 }
1672 
1673 /// Should this call expression be treated as a string literal?
1674 static bool IsStringLiteralCall(const CallExpr *E) {
1675  unsigned Builtin = E->getBuiltinCallee();
1676  return (Builtin == Builtin::BI__builtin___CFStringMakeConstantString ||
1677  Builtin == Builtin::BI__builtin___NSStringMakeConstantString);
1678 }
1679 
1681  // C++11 [expr.const]p3 An address constant expression is a prvalue core
1682  // constant expression of pointer type that evaluates to...
1683 
1684  // ... a null pointer value, or a prvalue core constant expression of type
1685  // std::nullptr_t.
1686  if (!B) return true;
1687 
1688  if (const ValueDecl *D = B.dyn_cast<const ValueDecl*>()) {
1689  // ... the address of an object with static storage duration,
1690  if (const VarDecl *VD = dyn_cast<VarDecl>(D))
1691  return VD->hasGlobalStorage();
1692  // ... the address of a function,
1693  return isa<FunctionDecl>(D);
1694  }
1695 
1696  const Expr *E = B.get<const Expr*>();
1697  switch (E->getStmtClass()) {
1698  default:
1699  return false;
1700  case Expr::CompoundLiteralExprClass: {
1701  const CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
1702  return CLE->isFileScope() && CLE->isLValue();
1703  }
1704  case Expr::MaterializeTemporaryExprClass:
1705  // A materialized temporary might have been lifetime-extended to static
1706  // storage duration.
1707  return cast<MaterializeTemporaryExpr>(E)->getStorageDuration() == SD_Static;
1708  // A string literal has static storage duration.
1709  case Expr::StringLiteralClass:
1710  case Expr::PredefinedExprClass:
1711  case Expr::ObjCStringLiteralClass:
1712  case Expr::ObjCEncodeExprClass:
1713  case Expr::CXXTypeidExprClass:
1714  case Expr::CXXUuidofExprClass:
1715  return true;
1716  case Expr::CallExprClass:
1717  return IsStringLiteralCall(cast<CallExpr>(E));
1718  // For GCC compatibility, &&label has static storage duration.
1719  case Expr::AddrLabelExprClass:
1720  return true;
1721  // A Block literal expression may be used as the initialization value for
1722  // Block variables at global or local static scope.
1723  case Expr::BlockExprClass:
1724  return !cast<BlockExpr>(E)->getBlockDecl()->hasCaptures();
1725  case Expr::ImplicitValueInitExprClass:
1726  // FIXME:
1727  // We can never form an lvalue with an implicit value initialization as its
1728  // base through expression evaluation, so these only appear in one case: the
1729  // implicit variable declaration we invent when checking whether a constexpr
1730  // constructor can produce a constant expression. We must assume that such
1731  // an expression might be a global lvalue.
1732  return true;
1733  }
1734 }
1735 
1736 static const ValueDecl *GetLValueBaseDecl(const LValue &LVal) {
1737  return LVal.Base.dyn_cast<const ValueDecl*>();
1738 }
1739 
1740 static bool IsLiteralLValue(const LValue &Value) {
1741  if (Value.getLValueCallIndex())
1742  return false;
1743  const Expr *E = Value.Base.dyn_cast<const Expr*>();
1744  return E && !isa<MaterializeTemporaryExpr>(E);
1745 }
1746 
1747 static bool IsWeakLValue(const LValue &Value) {
1748  const ValueDecl *Decl = GetLValueBaseDecl(Value);
1749  return Decl && Decl->isWeak();
1750 }
1751 
1752 static bool isZeroSized(const LValue &Value) {
1753  const ValueDecl *Decl = GetLValueBaseDecl(Value);
1754  if (Decl && isa<VarDecl>(Decl)) {
1755  QualType Ty = Decl->getType();
1756  if (Ty->isArrayType())
1757  return Ty->isIncompleteType() ||
1758  Decl->getASTContext().getTypeSize(Ty) == 0;
1759  }
1760  return false;
1761 }
1762 
1763 static bool HasSameBase(const LValue &A, const LValue &B) {
1764  if (!A.getLValueBase())
1765  return !B.getLValueBase();
1766  if (!B.getLValueBase())
1767  return false;
1768 
1769  if (A.getLValueBase().getOpaqueValue() !=
1770  B.getLValueBase().getOpaqueValue()) {
1771  const Decl *ADecl = GetLValueBaseDecl(A);
1772  if (!ADecl)
1773  return false;
1774  const Decl *BDecl = GetLValueBaseDecl(B);
1775  if (!BDecl || ADecl->getCanonicalDecl() != BDecl->getCanonicalDecl())
1776  return false;
1777  }
1778 
1779  return IsGlobalLValue(A.getLValueBase()) ||
1780  (A.getLValueCallIndex() == B.getLValueCallIndex() &&
1781  A.getLValueVersion() == B.getLValueVersion());
1782 }
1783 
1784 static void NoteLValueLocation(EvalInfo &Info, APValue::LValueBase Base) {
1785  assert(Base && "no location for a null lvalue");
1786  const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
1787  if (VD)
1788  Info.Note(VD->getLocation(), diag::note_declared_at);
1789  else
1790  Info.Note(Base.get<const Expr*>()->getExprLoc(),
1791  diag::note_constexpr_temporary_here);
1792 }
1793 
1794 /// Check that this reference or pointer core constant expression is a valid
1795 /// value for an address or reference constant expression. Return true if we
1796 /// can fold this expression, whether or not it's a constant expression.
1797 static bool CheckLValueConstantExpression(EvalInfo &Info, SourceLocation Loc,
1798  QualType Type, const LValue &LVal,
1799  Expr::ConstExprUsage Usage) {
1800  bool IsReferenceType = Type->isReferenceType();
1801 
1802  APValue::LValueBase Base = LVal.getLValueBase();
1803  const SubobjectDesignator &Designator = LVal.getLValueDesignator();
1804 
1805  // Check that the object is a global. Note that the fake 'this' object we
1806  // manufacture when checking potential constant expressions is conservatively
1807  // assumed to be global here.
1808  if (!IsGlobalLValue(Base)) {
1809  if (Info.getLangOpts().CPlusPlus11) {
1810  const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
1811  Info.FFDiag(Loc, diag::note_constexpr_non_global, 1)
1812  << IsReferenceType << !Designator.Entries.empty()
1813  << !!VD << VD;
1814  NoteLValueLocation(Info, Base);
1815  } else {
1816  Info.FFDiag(Loc);
1817  }
1818  // Don't allow references to temporaries to escape.
1819  return false;
1820  }
1821  assert((Info.checkingPotentialConstantExpression() ||
1822  LVal.getLValueCallIndex() == 0) &&
1823  "have call index for global lvalue");
1824 
1825  if (const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>()) {
1826  if (const VarDecl *Var = dyn_cast<const VarDecl>(VD)) {
1827  // Check if this is a thread-local variable.
1828  if (Var->getTLSKind())
1829  return false;
1830 
1831  // A dllimport variable never acts like a constant.
1832  if (Usage == Expr::EvaluateForCodeGen && Var->hasAttr<DLLImportAttr>())
1833  return false;
1834  }
1835  if (const auto *FD = dyn_cast<const FunctionDecl>(VD)) {
1836  // __declspec(dllimport) must be handled very carefully:
1837  // We must never initialize an expression with the thunk in C++.
1838  // Doing otherwise would allow the same id-expression to yield
1839  // different addresses for the same function in different translation
1840  // units. However, this means that we must dynamically initialize the
1841  // expression with the contents of the import address table at runtime.
1842  //
1843  // The C language has no notion of ODR; furthermore, it has no notion of
1844  // dynamic initialization. This means that we are permitted to
1845  // perform initialization with the address of the thunk.
1846  if (Info.getLangOpts().CPlusPlus && Usage == Expr::EvaluateForCodeGen &&
1847  FD->hasAttr<DLLImportAttr>())
1848  return false;
1849  }
1850  }
1851 
1852  // Allow address constant expressions to be past-the-end pointers. This is
1853  // an extension: the standard requires them to point to an object.
1854  if (!IsReferenceType)
1855  return true;
1856 
1857  // A reference constant expression must refer to an object.
1858  if (!Base) {
1859  // FIXME: diagnostic
1860  Info.CCEDiag(Loc);
1861  return true;
1862  }
1863 
1864  // Does this refer one past the end of some object?
1865  if (!Designator.Invalid && Designator.isOnePastTheEnd()) {
1866  const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
1867  Info.FFDiag(Loc, diag::note_constexpr_past_end, 1)
1868  << !Designator.Entries.empty() << !!VD << VD;
1869  NoteLValueLocation(Info, Base);
1870  }
1871 
1872  return true;
1873 }
1874 
1875 /// Member pointers are constant expressions unless they point to a
1876 /// non-virtual dllimport member function.
1877 static bool CheckMemberPointerConstantExpression(EvalInfo &Info,
1878  SourceLocation Loc,
1879  QualType Type,
1880  const APValue &Value,
1881  Expr::ConstExprUsage Usage) {
1882  const ValueDecl *Member = Value.getMemberPointerDecl();
1883  const auto *FD = dyn_cast_or_null<CXXMethodDecl>(Member);
1884  if (!FD)
1885  return true;
1886  return Usage == Expr::EvaluateForMangling || FD->isVirtual() ||
1887  !FD->hasAttr<DLLImportAttr>();
1888 }
1889 
1890 /// Check that this core constant expression is of literal type, and if not,
1891 /// produce an appropriate diagnostic.
1892 static bool CheckLiteralType(EvalInfo &Info, const Expr *E,
1893  const LValue *This = nullptr) {
1894  if (!E->isRValue() || E->getType()->isLiteralType(Info.Ctx))
1895  return true;
1896 
1897  // C++1y: A constant initializer for an object o [...] may also invoke
1898  // constexpr constructors for o and its subobjects even if those objects
1899  // are of non-literal class types.
1900  //
1901  // C++11 missed this detail for aggregates, so classes like this:
1902  // struct foo_t { union { int i; volatile int j; } u; };
1903  // are not (obviously) initializable like so:
1904  // __attribute__((__require_constant_initialization__))
1905  // static const foo_t x = {{0}};
1906  // because "i" is a subobject with non-literal initialization (due to the
1907  // volatile member of the union). See:
1908  // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1677
1909  // Therefore, we use the C++1y behavior.
1910  if (This && Info.EvaluatingDecl == This->getLValueBase())
1911  return true;
1912 
1913  // Prvalue constant expressions must be of literal types.
1914  if (Info.getLangOpts().CPlusPlus11)
1915  Info.FFDiag(E, diag::note_constexpr_nonliteral)
1916  << E->getType();
1917  else
1918  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
1919  return false;
1920 }
1921 
1922 /// Check that this core constant expression value is a valid value for a
1923 /// constant expression. If not, report an appropriate diagnostic. Does not
1924 /// check that the expression is of literal type.
1925 static bool
1926 CheckConstantExpression(EvalInfo &Info, SourceLocation DiagLoc, QualType Type,
1927  const APValue &Value,
1929  if (Value.isUninit()) {
1930  Info.FFDiag(DiagLoc, diag::note_constexpr_uninitialized)
1931  << true << Type;
1932  return false;
1933  }
1934 
1935  // We allow _Atomic(T) to be initialized from anything that T can be
1936  // initialized from.
1937  if (const AtomicType *AT = Type->getAs<AtomicType>())
1938  Type = AT->getValueType();
1939 
1940  // Core issue 1454: For a literal constant expression of array or class type,
1941  // each subobject of its value shall have been initialized by a constant
1942  // expression.
1943  if (Value.isArray()) {
1944  QualType EltTy = Type->castAsArrayTypeUnsafe()->getElementType();
1945  for (unsigned I = 0, N = Value.getArrayInitializedElts(); I != N; ++I) {
1946  if (!CheckConstantExpression(Info, DiagLoc, EltTy,
1947  Value.getArrayInitializedElt(I), Usage))
1948  return false;
1949  }
1950  if (!Value.hasArrayFiller())
1951  return true;
1952  return CheckConstantExpression(Info, DiagLoc, EltTy, Value.getArrayFiller(),
1953  Usage);
1954  }
1955  if (Value.isUnion() && Value.getUnionField()) {
1956  return CheckConstantExpression(Info, DiagLoc,
1957  Value.getUnionField()->getType(),
1958  Value.getUnionValue(), Usage);
1959  }
1960  if (Value.isStruct()) {
1961  RecordDecl *RD = Type->castAs<RecordType>()->getDecl();
1962  if (const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD)) {
1963  unsigned BaseIndex = 0;
1964  for (const CXXBaseSpecifier &BS : CD->bases()) {
1965  if (!CheckConstantExpression(Info, DiagLoc, BS.getType(),
1966  Value.getStructBase(BaseIndex), Usage))
1967  return false;
1968  ++BaseIndex;
1969  }
1970  }
1971  for (const auto *I : RD->fields()) {
1972  if (I->isUnnamedBitfield())
1973  continue;
1974 
1975  if (!CheckConstantExpression(Info, DiagLoc, I->getType(),
1976  Value.getStructField(I->getFieldIndex()),
1977  Usage))
1978  return false;
1979  }
1980  }
1981 
1982  if (Value.isLValue()) {
1983  LValue LVal;
1984  LVal.setFrom(Info.Ctx, Value);
1985  return CheckLValueConstantExpression(Info, DiagLoc, Type, LVal, Usage);
1986  }
1987 
1988  if (Value.isMemberPointer())
1989  return CheckMemberPointerConstantExpression(Info, DiagLoc, Type, Value, Usage);
1990 
1991  // Everything else is fine.
1992  return true;
1993 }
1994 
1995 static bool EvalPointerValueAsBool(const APValue &Value, bool &Result) {
1996  // A null base expression indicates a null pointer. These are always
1997  // evaluatable, and they are false unless the offset is zero.
1998  if (!Value.getLValueBase()) {
1999  Result = !Value.getLValueOffset().isZero();
2000  return true;
2001  }
2002 
2003  // We have a non-null base. These are generally known to be true, but if it's
2004  // a weak declaration it can be null at runtime.
2005  Result = true;
2006  const ValueDecl *Decl = Value.getLValueBase().dyn_cast<const ValueDecl*>();
2007  return !Decl || !Decl->isWeak();
2008 }
2009 
2010 static bool HandleConversionToBool(const APValue &Val, bool &Result) {
2011  switch (Val.getKind()) {
2013  return false;
2014  case APValue::Int:
2015  Result = Val.getInt().getBoolValue();
2016  return true;
2017  case APValue::Float:
2018  Result = !Val.getFloat().isZero();
2019  return true;
2020  case APValue::ComplexInt:
2021  Result = Val.getComplexIntReal().getBoolValue() ||
2022  Val.getComplexIntImag().getBoolValue();
2023  return true;
2024  case APValue::ComplexFloat:
2025  Result = !Val.getComplexFloatReal().isZero() ||
2026  !Val.getComplexFloatImag().isZero();
2027  return true;
2028  case APValue::LValue:
2029  return EvalPointerValueAsBool(Val, Result);
2031  Result = Val.getMemberPointerDecl();
2032  return true;
2033  case APValue::Vector:
2034  case APValue::Array:
2035  case APValue::Struct:
2036  case APValue::Union:
2038  return false;
2039  }
2040 
2041  llvm_unreachable("unknown APValue kind");
2042 }
2043 
2044 static bool EvaluateAsBooleanCondition(const Expr *E, bool &Result,
2045  EvalInfo &Info) {
2046  assert(E->isRValue() && "missing lvalue-to-rvalue conv in bool condition");
2047  APValue Val;
2048  if (!Evaluate(Val, Info, E))
2049  return false;
2050  return HandleConversionToBool(Val, Result);
2051 }
2052 
2053 template<typename T>
2054 static bool HandleOverflow(EvalInfo &Info, const Expr *E,
2055  const T &SrcValue, QualType DestType) {
2056  Info.CCEDiag(E, diag::note_constexpr_overflow)
2057  << SrcValue << DestType;
2058  return Info.noteUndefinedBehavior();
2059 }
2060 
2061 static bool HandleFloatToIntCast(EvalInfo &Info, const Expr *E,
2062  QualType SrcType, const APFloat &Value,
2063  QualType DestType, APSInt &Result) {
2064  unsigned DestWidth = Info.Ctx.getIntWidth(DestType);
2065  // Determine whether we are converting to unsigned or signed.
2066  bool DestSigned = DestType->isSignedIntegerOrEnumerationType();
2067 
2068  Result = APSInt(DestWidth, !DestSigned);
2069  bool ignored;
2070  if (Value.convertToInteger(Result, llvm::APFloat::rmTowardZero, &ignored)
2071  & APFloat::opInvalidOp)
2072  return HandleOverflow(Info, E, Value, DestType);
2073  return true;
2074 }
2075 
2076 static bool HandleFloatToFloatCast(EvalInfo &Info, const Expr *E,
2077  QualType SrcType, QualType DestType,
2078  APFloat &Result) {
2079  APFloat Value = Result;
2080  bool ignored;
2081  if (Result.convert(Info.Ctx.getFloatTypeSemantics(DestType),
2082  APFloat::rmNearestTiesToEven, &ignored)
2083  & APFloat::opOverflow)
2084  return HandleOverflow(Info, E, Value, DestType);
2085  return true;
2086 }
2087 
2088 static APSInt HandleIntToIntCast(EvalInfo &Info, const Expr *E,
2089  QualType DestType, QualType SrcType,
2090  const APSInt &Value) {
2091  unsigned DestWidth = Info.Ctx.getIntWidth(DestType);
2092  APSInt Result = Value;
2093  // Figure out if this is a truncate, extend or noop cast.
2094  // If the input is signed, do a sign extend, noop, or truncate.
2095  Result = Result.extOrTrunc(DestWidth);
2096  Result.setIsUnsigned(DestType->isUnsignedIntegerOrEnumerationType());
2097  return Result;
2098 }
2099 
2100 static bool HandleIntToFloatCast(EvalInfo &Info, const Expr *E,
2101  QualType SrcType, const APSInt &Value,
2102  QualType DestType, APFloat &Result) {
2103  Result = APFloat(Info.Ctx.getFloatTypeSemantics(DestType), 1);
2104  if (Result.convertFromAPInt(Value, Value.isSigned(),
2105  APFloat::rmNearestTiesToEven)
2106  & APFloat::opOverflow)
2107  return HandleOverflow(Info, E, Value, DestType);
2108  return true;
2109 }
2110 
2111 static bool truncateBitfieldValue(EvalInfo &Info, const Expr *E,
2112  APValue &Value, const FieldDecl *FD) {
2113  assert(FD->isBitField() && "truncateBitfieldValue on non-bitfield");
2114 
2115  if (!Value.isInt()) {
2116  // Trying to store a pointer-cast-to-integer into a bitfield.
2117  // FIXME: In this case, we should provide the diagnostic for casting
2118  // a pointer to an integer.
2119  assert(Value.isLValue() && "integral value neither int nor lvalue?");
2120  Info.FFDiag(E);
2121  return false;
2122  }
2123 
2124  APSInt &Int = Value.getInt();
2125  unsigned OldBitWidth = Int.getBitWidth();
2126  unsigned NewBitWidth = FD->getBitWidthValue(Info.Ctx);
2127  if (NewBitWidth < OldBitWidth)
2128  Int = Int.trunc(NewBitWidth).extend(OldBitWidth);
2129  return true;
2130 }
2131 
2132 static bool EvalAndBitcastToAPInt(EvalInfo &Info, const Expr *E,
2133  llvm::APInt &Res) {
2134  APValue SVal;
2135  if (!Evaluate(SVal, Info, E))
2136  return false;
2137  if (SVal.isInt()) {
2138  Res = SVal.getInt();
2139  return true;
2140  }
2141  if (SVal.isFloat()) {
2142  Res = SVal.getFloat().bitcastToAPInt();
2143  return true;
2144  }
2145  if (SVal.isVector()) {
2146  QualType VecTy = E->getType();
2147  unsigned VecSize = Info.Ctx.getTypeSize(VecTy);
2148  QualType EltTy = VecTy->castAs<VectorType>()->getElementType();
2149  unsigned EltSize = Info.Ctx.getTypeSize(EltTy);
2150  bool BigEndian = Info.Ctx.getTargetInfo().isBigEndian();
2151  Res = llvm::APInt::getNullValue(VecSize);
2152  for (unsigned i = 0; i < SVal.getVectorLength(); i++) {
2153  APValue &Elt = SVal.getVectorElt(i);
2154  llvm::APInt EltAsInt;
2155  if (Elt.isInt()) {
2156  EltAsInt = Elt.getInt();
2157  } else if (Elt.isFloat()) {
2158  EltAsInt = Elt.getFloat().bitcastToAPInt();
2159  } else {
2160  // Don't try to handle vectors of anything other than int or float
2161  // (not sure if it's possible to hit this case).
2162  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2163  return false;
2164  }
2165  unsigned BaseEltSize = EltAsInt.getBitWidth();
2166  if (BigEndian)
2167  Res |= EltAsInt.zextOrTrunc(VecSize).rotr(i*EltSize+BaseEltSize);
2168  else
2169  Res |= EltAsInt.zextOrTrunc(VecSize).rotl(i*EltSize);
2170  }
2171  return true;
2172  }
2173  // Give up if the input isn't an int, float, or vector. For example, we
2174  // reject "(v4i16)(intptr_t)&a".
2175  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2176  return false;
2177 }
2178 
2179 /// Perform the given integer operation, which is known to need at most BitWidth
2180 /// bits, and check for overflow in the original type (if that type was not an
2181 /// unsigned type).
2182 template<typename Operation>
2183 static bool CheckedIntArithmetic(EvalInfo &Info, const Expr *E,
2184  const APSInt &LHS, const APSInt &RHS,
2185  unsigned BitWidth, Operation Op,
2186  APSInt &Result) {
2187  if (LHS.isUnsigned()) {
2188  Result = Op(LHS, RHS);
2189  return true;
2190  }
2191 
2192  APSInt Value(Op(LHS.extend(BitWidth), RHS.extend(BitWidth)), false);
2193  Result = Value.trunc(LHS.getBitWidth());
2194  if (Result.extend(BitWidth) != Value) {
2195  if (Info.checkingForOverflow())
2196  Info.Ctx.getDiagnostics().Report(E->getExprLoc(),
2197  diag::warn_integer_constant_overflow)
2198  << Result.toString(10) << E->getType();
2199  else
2200  return HandleOverflow(Info, E, Value, E->getType());
2201  }
2202  return true;
2203 }
2204 
2205 /// Perform the given binary integer operation.
2206 static bool handleIntIntBinOp(EvalInfo &Info, const Expr *E, const APSInt &LHS,
2207  BinaryOperatorKind Opcode, APSInt RHS,
2208  APSInt &Result) {
2209  switch (Opcode) {
2210  default:
2211  Info.FFDiag(E);
2212  return false;
2213  case BO_Mul:
2214  return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() * 2,
2215  std::multiplies<APSInt>(), Result);
2216  case BO_Add:
2217  return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() + 1,
2218  std::plus<APSInt>(), Result);
2219  case BO_Sub:
2220  return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() + 1,
2221  std::minus<APSInt>(), Result);
2222  case BO_And: Result = LHS & RHS; return true;
2223  case BO_Xor: Result = LHS ^ RHS; return true;
2224  case BO_Or: Result = LHS | RHS; return true;
2225  case BO_Div:
2226  case BO_Rem:
2227  if (RHS == 0) {
2228  Info.FFDiag(E, diag::note_expr_divide_by_zero);
2229  return false;
2230  }
2231  Result = (Opcode == BO_Rem ? LHS % RHS : LHS / RHS);
2232  // Check for overflow case: INT_MIN / -1 or INT_MIN % -1. APSInt supports
2233  // this operation and gives the two's complement result.
2234  if (RHS.isNegative() && RHS.isAllOnesValue() &&
2235  LHS.isSigned() && LHS.isMinSignedValue())
2236  return HandleOverflow(Info, E, -LHS.extend(LHS.getBitWidth() + 1),
2237  E->getType());
2238  return true;
2239  case BO_Shl: {
2240  if (Info.getLangOpts().OpenCL)
2241  // OpenCL 6.3j: shift values are effectively % word size of LHS.
2242  RHS &= APSInt(llvm::APInt(RHS.getBitWidth(),
2243  static_cast<uint64_t>(LHS.getBitWidth() - 1)),
2244  RHS.isUnsigned());
2245  else if (RHS.isSigned() && RHS.isNegative()) {
2246  // During constant-folding, a negative shift is an opposite shift. Such
2247  // a shift is not a constant expression.
2248  Info.CCEDiag(E, diag::note_constexpr_negative_shift) << RHS;
2249  RHS = -RHS;
2250  goto shift_right;
2251  }
2252  shift_left:
2253  // C++11 [expr.shift]p1: Shift width must be less than the bit width of
2254  // the shifted type.
2255  unsigned SA = (unsigned) RHS.getLimitedValue(LHS.getBitWidth()-1);
2256  if (SA != RHS) {
2257  Info.CCEDiag(E, diag::note_constexpr_large_shift)
2258  << RHS << E->getType() << LHS.getBitWidth();
2259  } else if (LHS.isSigned()) {
2260  // C++11 [expr.shift]p2: A signed left shift must have a non-negative
2261  // operand, and must not overflow the corresponding unsigned type.
2262  if (LHS.isNegative())
2263  Info.CCEDiag(E, diag::note_constexpr_lshift_of_negative) << LHS;
2264  else if (LHS.countLeadingZeros() < SA)
2265  Info.CCEDiag(E, diag::note_constexpr_lshift_discards);
2266  }
2267  Result = LHS << SA;
2268  return true;
2269  }
2270  case BO_Shr: {
2271  if (Info.getLangOpts().OpenCL)
2272  // OpenCL 6.3j: shift values are effectively % word size of LHS.
2273  RHS &= APSInt(llvm::APInt(RHS.getBitWidth(),
2274  static_cast<uint64_t>(LHS.getBitWidth() - 1)),
2275  RHS.isUnsigned());
2276  else if (RHS.isSigned() && RHS.isNegative()) {
2277  // During constant-folding, a negative shift is an opposite shift. Such a
2278  // shift is not a constant expression.
2279  Info.CCEDiag(E, diag::note_constexpr_negative_shift) << RHS;
2280  RHS = -RHS;
2281  goto shift_left;
2282  }
2283  shift_right:
2284  // C++11 [expr.shift]p1: Shift width must be less than the bit width of the
2285  // shifted type.
2286  unsigned SA = (unsigned) RHS.getLimitedValue(LHS.getBitWidth()-1);
2287  if (SA != RHS)
2288  Info.CCEDiag(E, diag::note_constexpr_large_shift)
2289  << RHS << E->getType() << LHS.getBitWidth();
2290  Result = LHS >> SA;
2291  return true;
2292  }
2293 
2294  case BO_LT: Result = LHS < RHS; return true;
2295  case BO_GT: Result = LHS > RHS; return true;
2296  case BO_LE: Result = LHS <= RHS; return true;
2297  case BO_GE: Result = LHS >= RHS; return true;
2298  case BO_EQ: Result = LHS == RHS; return true;
2299  case BO_NE: Result = LHS != RHS; return true;
2300  case BO_Cmp:
2301  llvm_unreachable("BO_Cmp should be handled elsewhere");
2302  }
2303 }
2304 
2305 /// Perform the given binary floating-point operation, in-place, on LHS.
2306 static bool handleFloatFloatBinOp(EvalInfo &Info, const Expr *E,
2307  APFloat &LHS, BinaryOperatorKind Opcode,
2308  const APFloat &RHS) {
2309  switch (Opcode) {
2310  default:
2311  Info.FFDiag(E);
2312  return false;
2313  case BO_Mul:
2314  LHS.multiply(RHS, APFloat::rmNearestTiesToEven);
2315  break;
2316  case BO_Add:
2317  LHS.add(RHS, APFloat::rmNearestTiesToEven);
2318  break;
2319  case BO_Sub:
2320  LHS.subtract(RHS, APFloat::rmNearestTiesToEven);
2321  break;
2322  case BO_Div:
2323  LHS.divide(RHS, APFloat::rmNearestTiesToEven);
2324  break;
2325  }
2326 
2327  if (LHS.isInfinity() || LHS.isNaN()) {
2328  Info.CCEDiag(E, diag::note_constexpr_float_arithmetic) << LHS.isNaN();
2329  return Info.noteUndefinedBehavior();
2330  }
2331  return true;
2332 }
2333 
2334 /// Cast an lvalue referring to a base subobject to a derived class, by
2335 /// truncating the lvalue's path to the given length.
2336 static bool CastToDerivedClass(EvalInfo &Info, const Expr *E, LValue &Result,
2337  const RecordDecl *TruncatedType,
2338  unsigned TruncatedElements) {
2339  SubobjectDesignator &D = Result.Designator;
2340 
2341  // Check we actually point to a derived class object.
2342  if (TruncatedElements == D.Entries.size())
2343  return true;
2344  assert(TruncatedElements >= D.MostDerivedPathLength &&
2345  "not casting to a derived class");
2346  if (!Result.checkSubobject(Info, E, CSK_Derived))
2347  return false;
2348 
2349  // Truncate the path to the subobject, and remove any derived-to-base offsets.
2350  const RecordDecl *RD = TruncatedType;
2351  for (unsigned I = TruncatedElements, N = D.Entries.size(); I != N; ++I) {
2352  if (RD->isInvalidDecl()) return false;
2353  const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
2354  const CXXRecordDecl *Base = getAsBaseClass(D.Entries[I]);
2355  if (isVirtualBaseClass(D.Entries[I]))
2356  Result.Offset -= Layout.getVBaseClassOffset(Base);
2357  else
2358  Result.Offset -= Layout.getBaseClassOffset(Base);
2359  RD = Base;
2360  }
2361  D.Entries.resize(TruncatedElements);
2362  return true;
2363 }
2364 
2365 static bool HandleLValueDirectBase(EvalInfo &Info, const Expr *E, LValue &Obj,
2366  const CXXRecordDecl *Derived,
2367  const CXXRecordDecl *Base,
2368  const ASTRecordLayout *RL = nullptr) {
2369  if (!RL) {
2370  if (Derived->isInvalidDecl()) return false;
2371  RL = &Info.Ctx.getASTRecordLayout(Derived);
2372  }
2373 
2374  Obj.getLValueOffset() += RL->getBaseClassOffset(Base);
2375  Obj.addDecl(Info, E, Base, /*Virtual*/ false);
2376  return true;
2377 }
2378 
2379 static bool HandleLValueBase(EvalInfo &Info, const Expr *E, LValue &Obj,
2380  const CXXRecordDecl *DerivedDecl,
2381  const CXXBaseSpecifier *Base) {
2382  const CXXRecordDecl *BaseDecl = Base->getType()->getAsCXXRecordDecl();
2383 
2384  if (!Base->isVirtual())
2385  return HandleLValueDirectBase(Info, E, Obj, DerivedDecl, BaseDecl);
2386 
2387  SubobjectDesignator &D = Obj.Designator;
2388  if (D.Invalid)
2389  return false;
2390 
2391  // Extract most-derived object and corresponding type.
2392  DerivedDecl = D.MostDerivedType->getAsCXXRecordDecl();
2393  if (!CastToDerivedClass(Info, E, Obj, DerivedDecl, D.MostDerivedPathLength))
2394  return false;
2395 
2396  // Find the virtual base class.
2397  if (DerivedDecl->isInvalidDecl()) return false;
2398  const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(DerivedDecl);
2399  Obj.getLValueOffset() += Layout.getVBaseClassOffset(BaseDecl);
2400  Obj.addDecl(Info, E, BaseDecl, /*Virtual*/ true);
2401  return true;
2402 }
2403 
2404 static bool HandleLValueBasePath(EvalInfo &Info, const CastExpr *E,
2405  QualType Type, LValue &Result) {
2406  for (CastExpr::path_const_iterator PathI = E->path_begin(),
2407  PathE = E->path_end();
2408  PathI != PathE; ++PathI) {
2409  if (!HandleLValueBase(Info, E, Result, Type->getAsCXXRecordDecl(),
2410  *PathI))
2411  return false;
2412  Type = (*PathI)->getType();
2413  }
2414  return true;
2415 }
2416 
2417 /// Update LVal to refer to the given field, which must be a member of the type
2418 /// currently described by LVal.
2419 static bool HandleLValueMember(EvalInfo &Info, const Expr *E, LValue &LVal,
2420  const FieldDecl *FD,
2421  const ASTRecordLayout *RL = nullptr) {
2422  if (!RL) {
2423  if (FD->getParent()->isInvalidDecl()) return false;
2424  RL = &Info.Ctx.getASTRecordLayout(FD->getParent());
2425  }
2426 
2427  unsigned I = FD->getFieldIndex();
2428  LVal.adjustOffset(Info.Ctx.toCharUnitsFromBits(RL->getFieldOffset(I)));
2429  LVal.addDecl(Info, E, FD);
2430  return true;
2431 }
2432 
2433 /// Update LVal to refer to the given indirect field.
2434 static bool HandleLValueIndirectMember(EvalInfo &Info, const Expr *E,
2435  LValue &LVal,
2436  const IndirectFieldDecl *IFD) {
2437  for (const auto *C : IFD->chain())
2438  if (!HandleLValueMember(Info, E, LVal, cast<FieldDecl>(C)))
2439  return false;
2440  return true;
2441 }
2442 
2443 /// Get the size of the given type in char units.
2444 static bool HandleSizeof(EvalInfo &Info, SourceLocation Loc,
2445  QualType Type, CharUnits &Size) {
2446  // sizeof(void), __alignof__(void), sizeof(function) = 1 as a gcc
2447  // extension.
2448  if (Type->isVoidType() || Type->isFunctionType()) {
2449  Size = CharUnits::One();
2450  return true;
2451  }
2452 
2453  if (Type->isDependentType()) {
2454  Info.FFDiag(Loc);
2455  return false;
2456  }
2457 
2458  if (!Type->isConstantSizeType()) {
2459  // sizeof(vla) is not a constantexpr: C99 6.5.3.4p2.
2460  // FIXME: Better diagnostic.
2461  Info.FFDiag(Loc);
2462  return false;
2463  }
2464 
2465  Size = Info.Ctx.getTypeSizeInChars(Type);
2466  return true;
2467 }
2468 
2469 /// Update a pointer value to model pointer arithmetic.
2470 /// \param Info - Information about the ongoing evaluation.
2471 /// \param E - The expression being evaluated, for diagnostic purposes.
2472 /// \param LVal - The pointer value to be updated.
2473 /// \param EltTy - The pointee type represented by LVal.
2474 /// \param Adjustment - The adjustment, in objects of type EltTy, to add.
2475 static bool HandleLValueArrayAdjustment(EvalInfo &Info, const Expr *E,
2476  LValue &LVal, QualType EltTy,
2477  APSInt Adjustment) {
2478  CharUnits SizeOfPointee;
2479  if (!HandleSizeof(Info, E->getExprLoc(), EltTy, SizeOfPointee))
2480  return false;
2481 
2482  LVal.adjustOffsetAndIndex(Info, E, Adjustment, SizeOfPointee);
2483  return true;
2484 }
2485 
2486 static bool HandleLValueArrayAdjustment(EvalInfo &Info, const Expr *E,
2487  LValue &LVal, QualType EltTy,
2488  int64_t Adjustment) {
2489  return HandleLValueArrayAdjustment(Info, E, LVal, EltTy,
2490  APSInt::get(Adjustment));
2491 }
2492 
2493 /// Update an lvalue to refer to a component of a complex number.
2494 /// \param Info - Information about the ongoing evaluation.
2495 /// \param LVal - The lvalue to be updated.
2496 /// \param EltTy - The complex number's component type.
2497 /// \param Imag - False for the real component, true for the imaginary.
2498 static bool HandleLValueComplexElement(EvalInfo &Info, const Expr *E,
2499  LValue &LVal, QualType EltTy,
2500  bool Imag) {
2501  if (Imag) {
2502  CharUnits SizeOfComponent;
2503  if (!HandleSizeof(Info, E->getExprLoc(), EltTy, SizeOfComponent))
2504  return false;
2505  LVal.Offset += SizeOfComponent;
2506  }
2507  LVal.addComplex(Info, E, EltTy, Imag);
2508  return true;
2509 }
2510 
2511 static bool handleLValueToRValueConversion(EvalInfo &Info, const Expr *Conv,
2512  QualType Type, const LValue &LVal,
2513  APValue &RVal);
2514 
2515 /// Try to evaluate the initializer for a variable declaration.
2516 ///
2517 /// \param Info Information about the ongoing evaluation.
2518 /// \param E An expression to be used when printing diagnostics.
2519 /// \param VD The variable whose initializer should be obtained.
2520 /// \param Frame The frame in which the variable was created. Must be null
2521 /// if this variable is not local to the evaluation.
2522 /// \param Result Filled in with a pointer to the value of the variable.
2523 static bool evaluateVarDeclInit(EvalInfo &Info, const Expr *E,
2524  const VarDecl *VD, CallStackFrame *Frame,
2525  APValue *&Result, const LValue *LVal) {
2526 
2527  // If this is a parameter to an active constexpr function call, perform
2528  // argument substitution.
2529  if (const ParmVarDecl *PVD = dyn_cast<ParmVarDecl>(VD)) {
2530  // Assume arguments of a potential constant expression are unknown
2531  // constant expressions.
2532  if (Info.checkingPotentialConstantExpression())
2533  return false;
2534  if (!Frame || !Frame->Arguments) {
2535  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2536  return false;
2537  }
2538  Result = &Frame->Arguments[PVD->getFunctionScopeIndex()];
2539  return true;
2540  }
2541 
2542  // If this is a local variable, dig out its value.
2543  if (Frame) {
2544  Result = LVal ? Frame->getTemporary(VD, LVal->getLValueVersion())
2545  : Frame->getCurrentTemporary(VD);
2546  if (!Result) {
2547  // Assume variables referenced within a lambda's call operator that were
2548  // not declared within the call operator are captures and during checking
2549  // of a potential constant expression, assume they are unknown constant
2550  // expressions.
2551  assert(isLambdaCallOperator(Frame->Callee) &&
2552  (VD->getDeclContext() != Frame->Callee || VD->isInitCapture()) &&
2553  "missing value for local variable");
2554  if (Info.checkingPotentialConstantExpression())
2555  return false;
2556  // FIXME: implement capture evaluation during constant expr evaluation.
2557  Info.FFDiag(E->getBeginLoc(),
2558  diag::note_unimplemented_constexpr_lambda_feature_ast)
2559  << "captures not currently allowed";
2560  return false;
2561  }
2562  return true;
2563  }
2564 
2565  // Dig out the initializer, and use the declaration which it's attached to.
2566  const Expr *Init = VD->getAnyInitializer(VD);
2567  if (!Init || Init->isValueDependent()) {
2568  // If we're checking a potential constant expression, the variable could be
2569  // initialized later.
2570  if (!Info.checkingPotentialConstantExpression())
2571  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2572  return false;
2573  }
2574 
2575  // If we're currently evaluating the initializer of this declaration, use that
2576  // in-flight value.
2577  if (Info.EvaluatingDecl.dyn_cast<const ValueDecl*>() == VD) {
2578  Result = Info.EvaluatingDeclValue;
2579  return true;
2580  }
2581 
2582  // Never evaluate the initializer of a weak variable. We can't be sure that
2583  // this is the definition which will be used.
2584  if (VD->isWeak()) {
2585  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2586  return false;
2587  }
2588 
2589  // Check that we can fold the initializer. In C++, we will have already done
2590  // this in the cases where it matters for conformance.
2592  if (!VD->evaluateValue(Notes)) {
2593  Info.FFDiag(E, diag::note_constexpr_var_init_non_constant,
2594  Notes.size() + 1) << VD;
2595  Info.Note(VD->getLocation(), diag::note_declared_at);
2596  Info.addNotes(Notes);
2597  return false;
2598  } else if (!VD->checkInitIsICE()) {
2599  Info.CCEDiag(E, diag::note_constexpr_var_init_non_constant,
2600  Notes.size() + 1) << VD;
2601  Info.Note(VD->getLocation(), diag::note_declared_at);
2602  Info.addNotes(Notes);
2603  }
2604 
2605  Result = VD->getEvaluatedValue();
2606  return true;
2607 }
2608 
2610  Qualifiers Quals = T.getQualifiers();
2611  return Quals.hasConst() && !Quals.hasVolatile();
2612 }
2613 
2614 /// Get the base index of the given base class within an APValue representing
2615 /// the given derived class.
2616 static unsigned getBaseIndex(const CXXRecordDecl *Derived,
2617  const CXXRecordDecl *Base) {
2618  Base = Base->getCanonicalDecl();
2619  unsigned Index = 0;
2621  E = Derived->bases_end(); I != E; ++I, ++Index) {
2622  if (I->getType()->getAsCXXRecordDecl()->getCanonicalDecl() == Base)
2623  return Index;
2624  }
2625 
2626  llvm_unreachable("base class missing from derived class's bases list");
2627 }
2628 
2629 /// Extract the value of a character from a string literal.
2630 static APSInt extractStringLiteralCharacter(EvalInfo &Info, const Expr *Lit,
2631  uint64_t Index) {
2632  // FIXME: Support MakeStringConstant
2633  if (const auto *ObjCEnc = dyn_cast<ObjCEncodeExpr>(Lit)) {
2634  std::string Str;
2635  Info.Ctx.getObjCEncodingForType(ObjCEnc->getEncodedType(), Str);
2636  assert(Index <= Str.size() && "Index too large");
2637  return APSInt::getUnsigned(Str.c_str()[Index]);
2638  }
2639 
2640  if (auto PE = dyn_cast<PredefinedExpr>(Lit))
2641  Lit = PE->getFunctionName();
2642  const StringLiteral *S = cast<StringLiteral>(Lit);
2643  const ConstantArrayType *CAT =
2644  Info.Ctx.getAsConstantArrayType(S->getType());
2645  assert(CAT && "string literal isn't an array");
2646  QualType CharType = CAT->getElementType();
2647  assert(CharType->isIntegerType() && "unexpected character type");
2648 
2649  APSInt Value(S->getCharByteWidth() * Info.Ctx.getCharWidth(),
2650  CharType->isUnsignedIntegerType());
2651  if (Index < S->getLength())
2652  Value = S->getCodeUnit(Index);
2653  return Value;
2654 }
2655 
2656 // Expand a string literal into an array of characters.
2657 static void expandStringLiteral(EvalInfo &Info, const Expr *Lit,
2658  APValue &Result) {
2659  const StringLiteral *S = cast<StringLiteral>(Lit);
2660  const ConstantArrayType *CAT =
2661  Info.Ctx.getAsConstantArrayType(S->getType());
2662  assert(CAT && "string literal isn't an array");
2663  QualType CharType = CAT->getElementType();
2664  assert(CharType->isIntegerType() && "unexpected character type");
2665 
2666  unsigned Elts = CAT->getSize().getZExtValue();
2667  Result = APValue(APValue::UninitArray(),
2668  std::min(S->getLength(), Elts), Elts);
2669  APSInt Value(S->getCharByteWidth() * Info.Ctx.getCharWidth(),
2670  CharType->isUnsignedIntegerType());
2671  if (Result.hasArrayFiller())
2672  Result.getArrayFiller() = APValue(Value);
2673  for (unsigned I = 0, N = Result.getArrayInitializedElts(); I != N; ++I) {
2674  Value = S->getCodeUnit(I);
2675  Result.getArrayInitializedElt(I) = APValue(Value);
2676  }
2677 }
2678 
2679 // Expand an array so that it has more than Index filled elements.
2680 static void expandArray(APValue &Array, unsigned Index) {
2681  unsigned Size = Array.getArraySize();
2682  assert(Index < Size);
2683 
2684  // Always at least double the number of elements for which we store a value.
2685  unsigned OldElts = Array.getArrayInitializedElts();
2686  unsigned NewElts = std::max(Index+1, OldElts * 2);
2687  NewElts = std::min(Size, std::max(NewElts, 8u));
2688 
2689  // Copy the data across.
2690  APValue NewValue(APValue::UninitArray(), NewElts, Size);
2691  for (unsigned I = 0; I != OldElts; ++I)
2692  NewValue.getArrayInitializedElt(I).swap(Array.getArrayInitializedElt(I));
2693  for (unsigned I = OldElts; I != NewElts; ++I)
2694  NewValue.getArrayInitializedElt(I) = Array.getArrayFiller();
2695  if (NewValue.hasArrayFiller())
2696  NewValue.getArrayFiller() = Array.getArrayFiller();
2697  Array.swap(NewValue);
2698 }
2699 
2700 /// Determine whether a type would actually be read by an lvalue-to-rvalue
2701 /// conversion. If it's of class type, we may assume that the copy operation
2702 /// is trivial. Note that this is never true for a union type with fields
2703 /// (because the copy always "reads" the active member) and always true for
2704 /// a non-class type.
2707  if (!RD || (RD->isUnion() && !RD->field_empty()))
2708  return true;
2709  if (RD->isEmpty())
2710  return false;
2711 
2712  for (auto *Field : RD->fields())
2713  if (isReadByLvalueToRvalueConversion(Field->getType()))
2714  return true;
2715 
2716  for (auto &BaseSpec : RD->bases())
2717  if (isReadByLvalueToRvalueConversion(BaseSpec.getType()))
2718  return true;
2719 
2720  return false;
2721 }
2722 
2723 /// Diagnose an attempt to read from any unreadable field within the specified
2724 /// type, which might be a class type.
2725 static bool diagnoseUnreadableFields(EvalInfo &Info, const Expr *E,
2726  QualType T) {
2728  if (!RD)
2729  return false;
2730 
2731  if (!RD->hasMutableFields())
2732  return false;
2733 
2734  for (auto *Field : RD->fields()) {
2735  // If we're actually going to read this field in some way, then it can't
2736  // be mutable. If we're in a union, then assigning to a mutable field
2737  // (even an empty one) can change the active member, so that's not OK.
2738  // FIXME: Add core issue number for the union case.
2739  if (Field->isMutable() &&
2740  (RD->isUnion() || isReadByLvalueToRvalueConversion(Field->getType()))) {
2741  Info.FFDiag(E, diag::note_constexpr_ltor_mutable, 1) << Field;
2742  Info.Note(Field->getLocation(), diag::note_declared_at);
2743  return true;
2744  }
2745 
2746  if (diagnoseUnreadableFields(Info, E, Field->getType()))
2747  return true;
2748  }
2749 
2750  for (auto &BaseSpec : RD->bases())
2751  if (diagnoseUnreadableFields(Info, E, BaseSpec.getType()))
2752  return true;
2753 
2754  // All mutable fields were empty, and thus not actually read.
2755  return false;
2756 }
2757 
2758 /// Kinds of access we can perform on an object, for diagnostics.
2764 };
2765 
2766 namespace {
2767 /// A handle to a complete object (an object that is not a subobject of
2768 /// another object).
2769 struct CompleteObject {
2770  /// The value of the complete object.
2771  APValue *Value;
2772  /// The type of the complete object.
2773  QualType Type;
2774  bool LifetimeStartedInEvaluation;
2775 
2776  CompleteObject() : Value(nullptr) {}
2777  CompleteObject(APValue *Value, QualType Type,
2778  bool LifetimeStartedInEvaluation)
2779  : Value(Value), Type(Type),
2780  LifetimeStartedInEvaluation(LifetimeStartedInEvaluation) {
2781  assert(Value && "missing value for complete object");
2782  }
2783 
2784  explicit operator bool() const { return Value; }
2785 };
2786 } // end anonymous namespace
2787 
2788 /// Find the designated sub-object of an rvalue.
2789 template<typename SubobjectHandler>
2790 typename SubobjectHandler::result_type
2791 findSubobject(EvalInfo &Info, const Expr *E, const CompleteObject &Obj,
2792  const SubobjectDesignator &Sub, SubobjectHandler &handler) {
2793  if (Sub.Invalid)
2794  // A diagnostic will have already been produced.
2795  return handler.failed();
2796  if (Sub.isOnePastTheEnd() || Sub.isMostDerivedAnUnsizedArray()) {
2797  if (Info.getLangOpts().CPlusPlus11)
2798  Info.FFDiag(E, Sub.isOnePastTheEnd()
2799  ? diag::note_constexpr_access_past_end
2800  : diag::note_constexpr_access_unsized_array)
2801  << handler.AccessKind;
2802  else
2803  Info.FFDiag(E);
2804  return handler.failed();
2805  }
2806 
2807  APValue *O = Obj.Value;
2808  QualType ObjType = Obj.Type;
2809  const FieldDecl *LastField = nullptr;
2810  const bool MayReadMutableMembers =
2811  Obj.LifetimeStartedInEvaluation && Info.getLangOpts().CPlusPlus14;
2812 
2813  // Walk the designator's path to find the subobject.
2814  for (unsigned I = 0, N = Sub.Entries.size(); /**/; ++I) {
2815  if (O->isUninit()) {
2816  if (!Info.checkingPotentialConstantExpression())
2817  Info.FFDiag(E, diag::note_constexpr_access_uninit) << handler.AccessKind;
2818  return handler.failed();
2819  }
2820 
2821  if (I == N) {
2822  // If we are reading an object of class type, there may still be more
2823  // things we need to check: if there are any mutable subobjects, we
2824  // cannot perform this read. (This only happens when performing a trivial
2825  // copy or assignment.)
2826  if (ObjType->isRecordType() && handler.AccessKind == AK_Read &&
2827  !MayReadMutableMembers && diagnoseUnreadableFields(Info, E, ObjType))
2828  return handler.failed();
2829 
2830  if (!handler.found(*O, ObjType))
2831  return false;
2832 
2833  // If we modified a bit-field, truncate it to the right width.
2834  if (handler.AccessKind != AK_Read &&
2835  LastField && LastField->isBitField() &&
2836  !truncateBitfieldValue(Info, E, *O, LastField))
2837  return false;
2838 
2839  return true;
2840  }
2841 
2842  LastField = nullptr;
2843  if (ObjType->isArrayType()) {
2844  // Next subobject is an array element.
2845  const ConstantArrayType *CAT = Info.Ctx.getAsConstantArrayType(ObjType);
2846  assert(CAT && "vla in literal type?");
2847  uint64_t Index = Sub.Entries[I].ArrayIndex;
2848  if (CAT->getSize().ule(Index)) {
2849  // Note, it should not be possible to form a pointer with a valid
2850  // designator which points more than one past the end of the array.
2851  if (Info.getLangOpts().CPlusPlus11)
2852  Info.FFDiag(E, diag::note_constexpr_access_past_end)
2853  << handler.AccessKind;
2854  else
2855  Info.FFDiag(E);
2856  return handler.failed();
2857  }
2858 
2859  ObjType = CAT->getElementType();
2860 
2861  // An array object is represented as either an Array APValue or as an
2862  // LValue which refers to a string literal.
2863  if (O->isLValue()) {
2864  assert(I == N - 1 && "extracting subobject of character?");
2865  assert(!O->hasLValuePath() || O->getLValuePath().empty());
2866  if (handler.AccessKind != AK_Read)
2867  expandStringLiteral(Info, O->getLValueBase().get<const Expr *>(),
2868  *O);
2869  else
2870  return handler.foundString(*O, ObjType, Index);
2871  }
2872 
2873  if (O->getArrayInitializedElts() > Index)
2874  O = &O->getArrayInitializedElt(Index);
2875  else if (handler.AccessKind != AK_Read) {
2876  expandArray(*O, Index);
2877  O = &O->getArrayInitializedElt(Index);
2878  } else
2879  O = &O->getArrayFiller();
2880  } else if (ObjType->isAnyComplexType()) {
2881  // Next subobject is a complex number.
2882  uint64_t Index = Sub.Entries[I].ArrayIndex;
2883  if (Index > 1) {
2884  if (Info.getLangOpts().CPlusPlus11)
2885  Info.FFDiag(E, diag::note_constexpr_access_past_end)
2886  << handler.AccessKind;
2887  else
2888  Info.FFDiag(E);
2889  return handler.failed();
2890  }
2891 
2892  bool WasConstQualified = ObjType.isConstQualified();
2893  ObjType = ObjType->castAs<ComplexType>()->getElementType();
2894  if (WasConstQualified)
2895  ObjType.addConst();
2896 
2897  assert(I == N - 1 && "extracting subobject of scalar?");
2898  if (O->isComplexInt()) {
2899  return handler.found(Index ? O->getComplexIntImag()
2900  : O->getComplexIntReal(), ObjType);
2901  } else {
2902  assert(O->isComplexFloat());
2903  return handler.found(Index ? O->getComplexFloatImag()
2904  : O->getComplexFloatReal(), ObjType);
2905  }
2906  } else if (const FieldDecl *Field = getAsField(Sub.Entries[I])) {
2907  // In C++14 onwards, it is permitted to read a mutable member whose
2908  // lifetime began within the evaluation.
2909  // FIXME: Should we also allow this in C++11?
2910  if (Field->isMutable() && handler.AccessKind == AK_Read &&
2911  !MayReadMutableMembers) {
2912  Info.FFDiag(E, diag::note_constexpr_ltor_mutable, 1)
2913  << Field;
2914  Info.Note(Field->getLocation(), diag::note_declared_at);
2915  return handler.failed();
2916  }
2917 
2918  // Next subobject is a class, struct or union field.
2919  RecordDecl *RD = ObjType->castAs<RecordType>()->getDecl();
2920  if (RD->isUnion()) {
2921  const FieldDecl *UnionField = O->getUnionField();
2922  if (!UnionField ||
2923  UnionField->getCanonicalDecl() != Field->getCanonicalDecl()) {
2924  Info.FFDiag(E, diag::note_constexpr_access_inactive_union_member)
2925  << handler.AccessKind << Field << !UnionField << UnionField;
2926  return handler.failed();
2927  }
2928  O = &O->getUnionValue();
2929  } else
2930  O = &O->getStructField(Field->getFieldIndex());
2931 
2932  bool WasConstQualified = ObjType.isConstQualified();
2933  ObjType = Field->getType();
2934  if (WasConstQualified && !Field->isMutable())
2935  ObjType.addConst();
2936 
2937  if (ObjType.isVolatileQualified()) {
2938  if (Info.getLangOpts().CPlusPlus) {
2939  // FIXME: Include a description of the path to the volatile subobject.
2940  Info.FFDiag(E, diag::note_constexpr_access_volatile_obj, 1)
2941  << handler.AccessKind << 2 << Field;
2942  Info.Note(Field->getLocation(), diag::note_declared_at);
2943  } else {
2944  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2945  }
2946  return handler.failed();
2947  }
2948 
2949  LastField = Field;
2950  } else {
2951  // Next subobject is a base class.
2952  const CXXRecordDecl *Derived = ObjType->getAsCXXRecordDecl();
2953  const CXXRecordDecl *Base = getAsBaseClass(Sub.Entries[I]);
2954  O = &O->getStructBase(getBaseIndex(Derived, Base));
2955 
2956  bool WasConstQualified = ObjType.isConstQualified();
2957  ObjType = Info.Ctx.getRecordType(Base);
2958  if (WasConstQualified)
2959  ObjType.addConst();
2960  }
2961  }
2962 }
2963 
2964 namespace {
2965 struct ExtractSubobjectHandler {
2966  EvalInfo &Info;
2967  APValue &Result;
2968 
2969  static const AccessKinds AccessKind = AK_Read;
2970 
2971  typedef bool result_type;
2972  bool failed() { return false; }
2973  bool found(APValue &Subobj, QualType SubobjType) {
2974  Result = Subobj;
2975  return true;
2976  }
2977  bool found(APSInt &Value, QualType SubobjType) {
2978  Result = APValue(Value);
2979  return true;
2980  }
2981  bool found(APFloat &Value, QualType SubobjType) {
2982  Result = APValue(Value);
2983  return true;
2984  }
2985  bool foundString(APValue &Subobj, QualType SubobjType, uint64_t Character) {
2987  Info, Subobj.getLValueBase().get<const Expr *>(), Character));
2988  return true;
2989  }
2990 };
2991 } // end anonymous namespace
2992 
2994 
2995 /// Extract the designated sub-object of an rvalue.
2996 static bool extractSubobject(EvalInfo &Info, const Expr *E,
2997  const CompleteObject &Obj,
2998  const SubobjectDesignator &Sub,
2999  APValue &Result) {
3000  ExtractSubobjectHandler Handler = { Info, Result };
3001  return findSubobject(Info, E, Obj, Sub, Handler);
3002 }
3003 
3004 namespace {
3005 struct ModifySubobjectHandler {
3006  EvalInfo &Info;
3007  APValue &NewVal;
3008  const Expr *E;
3009 
3010  typedef bool result_type;
3011  static const AccessKinds AccessKind = AK_Assign;
3012 
3013  bool checkConst(QualType QT) {
3014  // Assigning to a const object has undefined behavior.
3015  if (QT.isConstQualified()) {
3016  Info.FFDiag(E, diag::note_constexpr_modify_const_type) << QT;
3017  return false;
3018  }
3019  return true;
3020  }
3021 
3022  bool failed() { return false; }
3023  bool found(APValue &Subobj, QualType SubobjType) {
3024  if (!checkConst(SubobjType))
3025  return false;
3026  // We've been given ownership of NewVal, so just swap it in.
3027  Subobj.swap(NewVal);
3028  return true;
3029  }
3030  bool found(APSInt &Value, QualType SubobjType) {
3031  if (!checkConst(SubobjType))
3032  return false;
3033  if (!NewVal.isInt()) {
3034  // Maybe trying to write a cast pointer value into a complex?
3035  Info.FFDiag(E);
3036  return false;
3037  }
3038  Value = NewVal.getInt();
3039  return true;
3040  }
3041  bool found(APFloat &Value, QualType SubobjType) {
3042  if (!checkConst(SubobjType))
3043  return false;
3044  Value = NewVal.getFloat();
3045  return true;
3046  }
3047  bool foundString(APValue &Subobj, QualType SubobjType, uint64_t Character) {
3048  llvm_unreachable("shouldn't encounter string elements with ExpandArrays");
3049  }
3050 };
3051 } // end anonymous namespace
3052 
3054 
3055 /// Update the designated sub-object of an rvalue to the given value.
3056 static bool modifySubobject(EvalInfo &Info, const Expr *E,
3057  const CompleteObject &Obj,
3058  const SubobjectDesignator &Sub,
3059  APValue &NewVal) {
3060  ModifySubobjectHandler Handler = { Info, NewVal, E };
3061  return findSubobject(Info, E, Obj, Sub, Handler);
3062 }
3063 
3064 /// Find the position where two subobject designators diverge, or equivalently
3065 /// the length of the common initial subsequence.
3066 static unsigned FindDesignatorMismatch(QualType ObjType,
3067  const SubobjectDesignator &A,
3068  const SubobjectDesignator &B,
3069  bool &WasArrayIndex) {
3070  unsigned I = 0, N = std::min(A.Entries.size(), B.Entries.size());
3071  for (/**/; I != N; ++I) {
3072  if (!ObjType.isNull() &&
3073  (ObjType->isArrayType() || ObjType->isAnyComplexType())) {
3074  // Next subobject is an array element.
3075  if (A.Entries[I].ArrayIndex != B.Entries[I].ArrayIndex) {
3076  WasArrayIndex = true;
3077  return I;
3078  }
3079  if (ObjType->isAnyComplexType())
3080  ObjType = ObjType->castAs<ComplexType>()->getElementType();
3081  else
3082  ObjType = ObjType->castAsArrayTypeUnsafe()->getElementType();
3083  } else {
3084  if (A.Entries[I].BaseOrMember != B.Entries[I].BaseOrMember) {
3085  WasArrayIndex = false;
3086  return I;
3087  }
3088  if (const FieldDecl *FD = getAsField(A.Entries[I]))
3089  // Next subobject is a field.
3090  ObjType = FD->getType();
3091  else
3092  // Next subobject is a base class.
3093  ObjType = QualType();
3094  }
3095  }
3096  WasArrayIndex = false;
3097  return I;
3098 }
3099 
3100 /// Determine whether the given subobject designators refer to elements of the
3101 /// same array object.
3102 static bool AreElementsOfSameArray(QualType ObjType,
3103  const SubobjectDesignator &A,
3104  const SubobjectDesignator &B) {
3105  if (A.Entries.size() != B.Entries.size())
3106  return false;
3107 
3108  bool IsArray = A.MostDerivedIsArrayElement;
3109  if (IsArray && A.MostDerivedPathLength != A.Entries.size())
3110  // A is a subobject of the array element.
3111  return false;
3112 
3113  // If A (and B) designates an array element, the last entry will be the array
3114  // index. That doesn't have to match. Otherwise, we're in the 'implicit array
3115  // of length 1' case, and the entire path must match.
3116  bool WasArrayIndex;
3117  unsigned CommonLength = FindDesignatorMismatch(ObjType, A, B, WasArrayIndex);
3118  return CommonLength >= A.Entries.size() - IsArray;
3119 }
3120 
3121 /// Find the complete object to which an LValue refers.
3122 static CompleteObject findCompleteObject(EvalInfo &Info, const Expr *E,
3123  AccessKinds AK, const LValue &LVal,
3124  QualType LValType) {
3125  if (!LVal.Base) {
3126  Info.FFDiag(E, diag::note_constexpr_access_null) << AK;
3127  return CompleteObject();
3128  }
3129 
3130  CallStackFrame *Frame = nullptr;
3131  if (LVal.getLValueCallIndex()) {
3132  Frame = Info.getCallFrame(LVal.getLValueCallIndex());
3133  if (!Frame) {
3134  Info.FFDiag(E, diag::note_constexpr_lifetime_ended, 1)
3135  << AK << LVal.Base.is<const ValueDecl*>();
3136  NoteLValueLocation(Info, LVal.Base);
3137  return CompleteObject();
3138  }
3139  }
3140 
3141  // C++11 DR1311: An lvalue-to-rvalue conversion on a volatile-qualified type
3142  // is not a constant expression (even if the object is non-volatile). We also
3143  // apply this rule to C++98, in order to conform to the expected 'volatile'
3144  // semantics.
3145  if (LValType.isVolatileQualified()) {
3146  if (Info.getLangOpts().CPlusPlus)
3147  Info.FFDiag(E, diag::note_constexpr_access_volatile_type)
3148  << AK << LValType;
3149  else
3150  Info.FFDiag(E);
3151  return CompleteObject();
3152  }
3153 
3154  // Compute value storage location and type of base object.
3155  APValue *BaseVal = nullptr;
3156  QualType BaseType = getType(LVal.Base);
3157  bool LifetimeStartedInEvaluation = Frame;
3158 
3159  if (const ValueDecl *D = LVal.Base.dyn_cast<const ValueDecl*>()) {
3160  // In C++98, const, non-volatile integers initialized with ICEs are ICEs.
3161  // In C++11, constexpr, non-volatile variables initialized with constant
3162  // expressions are constant expressions too. Inside constexpr functions,
3163  // parameters are constant expressions even if they're non-const.
3164  // In C++1y, objects local to a constant expression (those with a Frame) are
3165  // both readable and writable inside constant expressions.
3166  // In C, such things can also be folded, although they are not ICEs.
3167  const VarDecl *VD = dyn_cast<VarDecl>(D);
3168  if (VD) {
3169  if (const VarDecl *VDef = VD->getDefinition(Info.Ctx))
3170  VD = VDef;
3171  }
3172  if (!VD || VD->isInvalidDecl()) {
3173  Info.FFDiag(E);
3174  return CompleteObject();
3175  }
3176 
3177  // Accesses of volatile-qualified objects are not allowed.
3178  if (BaseType.isVolatileQualified()) {
3179  if (Info.getLangOpts().CPlusPlus) {
3180  Info.FFDiag(E, diag::note_constexpr_access_volatile_obj, 1)
3181  << AK << 1 << VD;
3182  Info.Note(VD->getLocation(), diag::note_declared_at);
3183  } else {
3184  Info.FFDiag(E);
3185  }
3186  return CompleteObject();
3187  }
3188 
3189  // Unless we're looking at a local variable or argument in a constexpr call,
3190  // the variable we're reading must be const.
3191  if (!Frame) {
3192  if (Info.getLangOpts().CPlusPlus14 &&
3193  VD == Info.EvaluatingDecl.dyn_cast<const ValueDecl *>()) {
3194  // OK, we can read and modify an object if we're in the process of
3195  // evaluating its initializer, because its lifetime began in this
3196  // evaluation.
3197  } else if (AK != AK_Read) {
3198  // All the remaining cases only permit reading.
3199  Info.FFDiag(E, diag::note_constexpr_modify_global);
3200  return CompleteObject();
3201  } else if (VD->isConstexpr()) {
3202  // OK, we can read this variable.
3203  } else if (BaseType->isIntegralOrEnumerationType()) {
3204  // In OpenCL if a variable is in constant address space it is a const value.
3205  if (!(BaseType.isConstQualified() ||
3206  (Info.getLangOpts().OpenCL &&
3207  BaseType.getAddressSpace() == LangAS::opencl_constant))) {
3208  if (Info.getLangOpts().CPlusPlus) {
3209  Info.FFDiag(E, diag::note_constexpr_ltor_non_const_int, 1) << VD;
3210  Info.Note(VD->getLocation(), diag::note_declared_at);
3211  } else {
3212  Info.FFDiag(E);
3213  }
3214  return CompleteObject();
3215  }
3216  } else if (BaseType->isFloatingType() && BaseType.isConstQualified()) {
3217  // We support folding of const floating-point types, in order to make
3218  // static const data members of such types (supported as an extension)
3219  // more useful.
3220  if (Info.getLangOpts().CPlusPlus11) {
3221  Info.CCEDiag(E, diag::note_constexpr_ltor_non_constexpr, 1) << VD;
3222  Info.Note(VD->getLocation(), diag::note_declared_at);
3223  } else {
3224  Info.CCEDiag(E);
3225  }
3226  } else if (BaseType.isConstQualified() && VD->hasDefinition(Info.Ctx)) {
3227  Info.CCEDiag(E, diag::note_constexpr_ltor_non_constexpr) << VD;
3228  // Keep evaluating to see what we can do.
3229  } else {
3230  // FIXME: Allow folding of values of any literal type in all languages.
3231  if (Info.checkingPotentialConstantExpression() &&
3232  VD->getType().isConstQualified() && !VD->hasDefinition(Info.Ctx)) {
3233  // The definition of this variable could be constexpr. We can't
3234  // access it right now, but may be able to in future.
3235  } else if (Info.getLangOpts().CPlusPlus11) {
3236  Info.FFDiag(E, diag::note_constexpr_ltor_non_constexpr, 1) << VD;
3237  Info.Note(VD->getLocation(), diag::note_declared_at);
3238  } else {
3239  Info.FFDiag(E);
3240  }
3241  return CompleteObject();
3242  }
3243  }
3244 
3245  if (!evaluateVarDeclInit(Info, E, VD, Frame, BaseVal, &LVal))
3246  return CompleteObject();
3247  } else {
3248  const Expr *Base = LVal.Base.dyn_cast<const Expr*>();
3249 
3250  if (!Frame) {
3251  if (const MaterializeTemporaryExpr *MTE =
3252  dyn_cast<MaterializeTemporaryExpr>(Base)) {
3253  assert(MTE->getStorageDuration() == SD_Static &&
3254  "should have a frame for a non-global materialized temporary");
3255 
3256  // Per C++1y [expr.const]p2:
3257  // an lvalue-to-rvalue conversion [is not allowed unless it applies to]
3258  // - a [...] glvalue of integral or enumeration type that refers to
3259  // a non-volatile const object [...]
3260  // [...]
3261  // - a [...] glvalue of literal type that refers to a non-volatile
3262  // object whose lifetime began within the evaluation of e.
3263  //
3264  // C++11 misses the 'began within the evaluation of e' check and
3265  // instead allows all temporaries, including things like:
3266  // int &&r = 1;
3267  // int x = ++r;
3268  // constexpr int k = r;
3269  // Therefore we use the C++14 rules in C++11 too.
3270  const ValueDecl *VD = Info.EvaluatingDecl.dyn_cast<const ValueDecl*>();
3271  const ValueDecl *ED = MTE->getExtendingDecl();
3272  if (!(BaseType.isConstQualified() &&
3273  BaseType->isIntegralOrEnumerationType()) &&
3274  !(VD && VD->getCanonicalDecl() == ED->getCanonicalDecl())) {
3275  Info.FFDiag(E, diag::note_constexpr_access_static_temporary, 1) << AK;
3276  Info.Note(MTE->getExprLoc(), diag::note_constexpr_temporary_here);
3277  return CompleteObject();
3278  }
3279 
3280  BaseVal = Info.Ctx.getMaterializedTemporaryValue(MTE, false);
3281  assert(BaseVal && "got reference to unevaluated temporary");
3282  LifetimeStartedInEvaluation = true;
3283  } else {
3284  Info.FFDiag(E);
3285  return CompleteObject();
3286  }
3287  } else {
3288  BaseVal = Frame->getTemporary(Base, LVal.Base.getVersion());
3289  assert(BaseVal && "missing value for temporary");
3290  }
3291 
3292  // Volatile temporary objects cannot be accessed in constant expressions.
3293  if (BaseType.isVolatileQualified()) {
3294  if (Info.getLangOpts().CPlusPlus) {
3295  Info.FFDiag(E, diag::note_constexpr_access_volatile_obj, 1)
3296  << AK << 0;
3297  Info.Note(Base->getExprLoc(), diag::note_constexpr_temporary_here);
3298  } else {
3299  Info.FFDiag(E);
3300  }
3301  return CompleteObject();
3302  }
3303  }
3304 
3305  // During the construction of an object, it is not yet 'const'.
3306  // FIXME: This doesn't do quite the right thing for const subobjects of the
3307  // object under construction.
3308  if (Info.isEvaluatingConstructor(LVal.getLValueBase(),
3309  LVal.getLValueCallIndex(),
3310  LVal.getLValueVersion())) {
3311  BaseType = Info.Ctx.getCanonicalType(BaseType);
3312  BaseType.removeLocalConst();
3313  LifetimeStartedInEvaluation = true;
3314  }
3315 
3316  // In C++14, we can't safely access any mutable state when we might be
3317  // evaluating after an unmodeled side effect.
3318  //
3319  // FIXME: Not all local state is mutable. Allow local constant subobjects
3320  // to be read here (but take care with 'mutable' fields).
3321  if ((Frame && Info.getLangOpts().CPlusPlus14 &&
3322  Info.EvalStatus.HasSideEffects) ||
3323  (AK != AK_Read && Info.IsSpeculativelyEvaluating))
3324  return CompleteObject();
3325 
3326  return CompleteObject(BaseVal, BaseType, LifetimeStartedInEvaluation);
3327 }
3328 
3329 /// Perform an lvalue-to-rvalue conversion on the given glvalue. This
3330 /// can also be used for 'lvalue-to-lvalue' conversions for looking up the
3331 /// glvalue referred to by an entity of reference type.
3332 ///
3333 /// \param Info - Information about the ongoing evaluation.
3334 /// \param Conv - The expression for which we are performing the conversion.
3335 /// Used for diagnostics.
3336 /// \param Type - The type of the glvalue (before stripping cv-qualifiers in the
3337 /// case of a non-class type).
3338 /// \param LVal - The glvalue on which we are attempting to perform this action.
3339 /// \param RVal - The produced value will be placed here.
3340 static bool handleLValueToRValueConversion(EvalInfo &Info, const Expr *Conv,
3341  QualType Type,
3342  const LValue &LVal, APValue &RVal) {
3343  if (LVal.Designator.Invalid)
3344  return false;
3345 
3346  // Check for special cases where there is no existing APValue to look at.
3347  const Expr *Base = LVal.Base.dyn_cast<const Expr*>();
3348  if (Base && !LVal.getLValueCallIndex() && !Type.isVolatileQualified()) {
3349  if (const CompoundLiteralExpr *CLE = dyn_cast<CompoundLiteralExpr>(Base)) {
3350  // In C99, a CompoundLiteralExpr is an lvalue, and we defer evaluating the
3351  // initializer until now for such expressions. Such an expression can't be
3352  // an ICE in C, so this only matters for fold.
3353  if (Type.isVolatileQualified()) {
3354  Info.FFDiag(Conv);
3355  return false;
3356  }
3357  APValue Lit;
3358  if (!Evaluate(Lit, Info, CLE->getInitializer()))
3359  return false;
3360  CompleteObject LitObj(&Lit, Base->getType(), false);
3361  return extractSubobject(Info, Conv, LitObj, LVal.Designator, RVal);
3362  } else if (isa<StringLiteral>(Base) || isa<PredefinedExpr>(Base)) {
3363  // We represent a string literal array as an lvalue pointing at the
3364  // corresponding expression, rather than building an array of chars.
3365  // FIXME: Support ObjCEncodeExpr, MakeStringConstant
3366  APValue Str(Base, CharUnits::Zero(), APValue::NoLValuePath(), 0);
3367  CompleteObject StrObj(&Str, Base->getType(), false);
3368  return extractSubobject(Info, Conv, StrObj, LVal.Designator, RVal);
3369  }
3370  }
3371 
3372  CompleteObject Obj = findCompleteObject(Info, Conv, AK_Read, LVal, Type);
3373  return Obj && extractSubobject(Info, Conv, Obj, LVal.Designator, RVal);
3374 }
3375 
3376 /// Perform an assignment of Val to LVal. Takes ownership of Val.
3377 static bool handleAssignment(EvalInfo &Info, const Expr *E, const LValue &LVal,
3378  QualType LValType, APValue &Val) {
3379  if (LVal.Designator.Invalid)
3380  return false;
3381 
3382  if (!Info.getLangOpts().CPlusPlus14) {
3383  Info.FFDiag(E);
3384  return false;
3385  }
3386 
3387  CompleteObject Obj = findCompleteObject(Info, E, AK_Assign, LVal, LValType);
3388  return Obj && modifySubobject(Info, E, Obj, LVal.Designator, Val);
3389 }
3390 
3391 namespace {
3392 struct CompoundAssignSubobjectHandler {
3393  EvalInfo &Info;
3394  const Expr *E;
3395  QualType PromotedLHSType;
3396  BinaryOperatorKind Opcode;
3397  const APValue &RHS;
3398 
3399  static const AccessKinds AccessKind = AK_Assign;
3400 
3401  typedef bool result_type;
3402 
3403  bool checkConst(QualType QT) {
3404  // Assigning to a const object has undefined behavior.
3405  if (QT.isConstQualified()) {
3406  Info.FFDiag(E, diag::note_constexpr_modify_const_type) << QT;
3407  return false;
3408  }
3409  return true;
3410  }
3411 
3412  bool failed() { return false; }
3413  bool found(APValue &Subobj, QualType SubobjType) {
3414  switch (Subobj.getKind()) {
3415  case APValue::Int:
3416  return found(Subobj.getInt(), SubobjType);
3417  case APValue::Float:
3418  return found(Subobj.getFloat(), SubobjType);
3419  case APValue::ComplexInt:
3420  case APValue::ComplexFloat:
3421  // FIXME: Implement complex compound assignment.
3422  Info.FFDiag(E);
3423  return false;
3424  case APValue::LValue:
3425  return foundPointer(Subobj, SubobjType);
3426  default:
3427  // FIXME: can this happen?
3428  Info.FFDiag(E);
3429  return false;
3430  }
3431  }
3432  bool found(APSInt &Value, QualType SubobjType) {
3433  if (!checkConst(SubobjType))
3434  return false;
3435 
3436  if (!SubobjType->isIntegerType() || !RHS.isInt()) {
3437  // We don't support compound assignment on integer-cast-to-pointer
3438  // values.
3439  Info.FFDiag(E);
3440  return false;
3441  }
3442 
3443  APSInt LHS = HandleIntToIntCast(Info, E, PromotedLHSType,
3444  SubobjType, Value);
3445  if (!handleIntIntBinOp(Info, E, LHS, Opcode, RHS.getInt(), LHS))
3446  return false;
3447  Value = HandleIntToIntCast(Info, E, SubobjType, PromotedLHSType, LHS);
3448  return true;
3449  }
3450  bool found(APFloat &Value, QualType SubobjType) {
3451  return checkConst(SubobjType) &&
3452  HandleFloatToFloatCast(Info, E, SubobjType, PromotedLHSType,
3453  Value) &&
3454  handleFloatFloatBinOp(Info, E, Value, Opcode, RHS.getFloat()) &&
3455  HandleFloatToFloatCast(Info, E, PromotedLHSType, SubobjType, Value);
3456  }
3457  bool foundPointer(APValue &Subobj, QualType SubobjType) {
3458  if (!checkConst(SubobjType))
3459  return false;
3460 
3461  QualType PointeeType;
3462  if (const PointerType *PT = SubobjType->getAs<PointerType>())
3463  PointeeType = PT->getPointeeType();
3464 
3465  if (PointeeType.isNull() || !RHS.isInt() ||
3466  (Opcode != BO_Add && Opcode != BO_Sub)) {
3467  Info.FFDiag(E);
3468  return false;
3469  }
3470 
3471  APSInt Offset = RHS.getInt();
3472  if (Opcode == BO_Sub)
3473  negateAsSigned(Offset);
3474 
3475  LValue LVal;
3476  LVal.setFrom(Info.Ctx, Subobj);
3477  if (!HandleLValueArrayAdjustment(Info, E, LVal, PointeeType, Offset))
3478  return false;
3479  LVal.moveInto(Subobj);
3480  return true;
3481  }
3482  bool foundString(APValue &Subobj, QualType SubobjType, uint64_t Character) {
3483  llvm_unreachable("shouldn't encounter string elements here");
3484  }
3485 };
3486 } // end anonymous namespace
3487 
3489 
3490 /// Perform a compound assignment of LVal <op>= RVal.
3492  EvalInfo &Info, const Expr *E,
3493  const LValue &LVal, QualType LValType, QualType PromotedLValType,
3494  BinaryOperatorKind Opcode, const APValue &RVal) {
3495  if (LVal.Designator.Invalid)
3496  return false;
3497 
3498  if (!Info.getLangOpts().CPlusPlus14) {
3499  Info.FFDiag(E);
3500  return false;
3501  }
3502 
3503  CompleteObject Obj = findCompleteObject(Info, E, AK_Assign, LVal, LValType);
3504  CompoundAssignSubobjectHandler Handler = { Info, E, PromotedLValType, Opcode,
3505  RVal };
3506  return Obj && findSubobject(Info, E, Obj, LVal.Designator, Handler);
3507 }
3508 
3509 namespace {
3510 struct IncDecSubobjectHandler {
3511  EvalInfo &Info;
3512  const UnaryOperator *E;
3514  APValue *Old;
3515 
3516  typedef bool result_type;
3517 
3518  bool checkConst(QualType QT) {
3519  // Assigning to a const object has undefined behavior.
3520  if (QT.isConstQualified()) {
3521  Info.FFDiag(E, diag::note_constexpr_modify_const_type) << QT;
3522  return false;
3523  }
3524  return true;
3525  }
3526 
3527  bool failed() { return false; }
3528  bool found(APValue &Subobj, QualType SubobjType) {
3529  // Stash the old value. Also clear Old, so we don't clobber it later
3530  // if we're post-incrementing a complex.
3531  if (Old) {
3532  *Old = Subobj;
3533  Old = nullptr;
3534  }
3535 
3536  switch (Subobj.getKind()) {
3537  case APValue::Int:
3538  return found(Subobj.getInt(), SubobjType);
3539  case APValue::Float:
3540  return found(Subobj.getFloat(), SubobjType);
3541  case APValue::ComplexInt:
3542  return found(Subobj.getComplexIntReal(),
3543  SubobjType->castAs<ComplexType>()->getElementType()
3544  .withCVRQualifiers(SubobjType.getCVRQualifiers()));
3545  case APValue::ComplexFloat:
3546  return found(Subobj.getComplexFloatReal(),
3547  SubobjType->castAs<ComplexType>()->getElementType()
3548  .withCVRQualifiers(SubobjType.getCVRQualifiers()));
3549  case APValue::LValue:
3550  return foundPointer(Subobj, SubobjType);
3551  default:
3552  // FIXME: can this happen?
3553  Info.FFDiag(E);
3554  return false;
3555  }
3556  }
3557  bool found(APSInt &Value, QualType SubobjType) {
3558  if (!checkConst(SubobjType))
3559  return false;
3560 
3561  if (!SubobjType->isIntegerType()) {
3562  // We don't support increment / decrement on integer-cast-to-pointer
3563  // values.
3564  Info.FFDiag(E);
3565  return false;
3566  }
3567 
3568  if (Old) *Old = APValue(Value);
3569 
3570  // bool arithmetic promotes to int, and the conversion back to bool
3571  // doesn't reduce mod 2^n, so special-case it.
3572  if (SubobjType->isBooleanType()) {
3573  if (AccessKind == AK_Increment)
3574  Value = 1;
3575  else
3576  Value = !Value;
3577  return true;
3578  }
3579 
3580  bool WasNegative = Value.isNegative();
3581  if (AccessKind == AK_Increment) {
3582  ++Value;
3583 
3584  if (!WasNegative && Value.isNegative() && E->canOverflow()) {
3585  APSInt ActualValue(Value, /*IsUnsigned*/true);
3586  return HandleOverflow(Info, E, ActualValue, SubobjType);
3587  }
3588  } else {
3589  --Value;
3590 
3591  if (WasNegative && !Value.isNegative() && E->canOverflow()) {
3592  unsigned BitWidth = Value.getBitWidth();
3593  APSInt ActualValue(Value.sext(BitWidth + 1), /*IsUnsigned*/false);
3594  ActualValue.setBit(BitWidth);
3595  return HandleOverflow(Info, E, ActualValue, SubobjType);
3596  }
3597  }
3598  return true;
3599  }
3600  bool found(APFloat &Value, QualType SubobjType) {
3601  if (!checkConst(SubobjType))
3602  return false;
3603 
3604  if (Old) *Old = APValue(Value);
3605 
3606  APFloat One(Value.getSemantics(), 1);
3607  if (AccessKind == AK_Increment)
3608  Value.add(One, APFloat::rmNearestTiesToEven);
3609  else
3610  Value.subtract(One, APFloat::rmNearestTiesToEven);
3611  return true;
3612  }
3613  bool foundPointer(APValue &Subobj, QualType SubobjType) {
3614  if (!checkConst(SubobjType))
3615  return false;
3616 
3617  QualType PointeeType;
3618  if (const PointerType *PT = SubobjType->getAs<PointerType>())
3619  PointeeType = PT->getPointeeType();
3620  else {
3621  Info.FFDiag(E);
3622  return false;
3623  }
3624 
3625  LValue LVal;
3626  LVal.setFrom(Info.Ctx, Subobj);
3627  if (!HandleLValueArrayAdjustment(Info, E, LVal, PointeeType,
3628  AccessKind == AK_Increment ? 1 : -1))
3629  return false;
3630  LVal.moveInto(Subobj);
3631  return true;
3632  }
3633  bool foundString(APValue &Subobj, QualType SubobjType, uint64_t Character) {
3634  llvm_unreachable("shouldn't encounter string elements here");
3635  }
3636 };
3637 } // end anonymous namespace
3638 
3639 /// Perform an increment or decrement on LVal.
3640 static bool handleIncDec(EvalInfo &Info, const Expr *E, const LValue &LVal,
3641  QualType LValType, bool IsIncrement, APValue *Old) {
3642  if (LVal.Designator.Invalid)
3643  return false;
3644 
3645  if (!Info.getLangOpts().CPlusPlus14) {
3646  Info.FFDiag(E);
3647  return false;
3648  }
3649 
3650  AccessKinds AK = IsIncrement ? AK_Increment : AK_Decrement;
3651  CompleteObject Obj = findCompleteObject(Info, E, AK, LVal, LValType);
3652  IncDecSubobjectHandler Handler = {Info, cast<UnaryOperator>(E), AK, Old};
3653  return Obj && findSubobject(Info, E, Obj, LVal.Designator, Handler);
3654 }
3655 
3656 /// Build an lvalue for the object argument of a member function call.
3657 static bool EvaluateObjectArgument(EvalInfo &Info, const Expr *Object,
3658  LValue &This) {
3659  if (Object->getType()->isPointerType())
3660  return EvaluatePointer(Object, This, Info);
3661 
3662  if (Object->isGLValue())
3663  return EvaluateLValue(Object, This, Info);
3664 
3665  if (Object->getType()->isLiteralType(Info.Ctx))
3666  return EvaluateTemporary(Object, This, Info);
3667 
3668  Info.FFDiag(Object, diag::note_constexpr_nonliteral) << Object->getType();
3669  return false;
3670 }
3671 
3672 /// HandleMemberPointerAccess - Evaluate a member access operation and build an
3673 /// lvalue referring to the result.
3674 ///
3675 /// \param Info - Information about the ongoing evaluation.
3676 /// \param LV - An lvalue referring to the base of the member pointer.
3677 /// \param RHS - The member pointer expression.
3678 /// \param IncludeMember - Specifies whether the member itself is included in
3679 /// the resulting LValue subobject designator. This is not possible when
3680 /// creating a bound member function.
3681 /// \return The field or method declaration to which the member pointer refers,
3682 /// or 0 if evaluation fails.
3683 static const ValueDecl *HandleMemberPointerAccess(EvalInfo &Info,
3684  QualType LVType,
3685  LValue &LV,
3686  const Expr *RHS,
3687  bool IncludeMember = true) {
3688  MemberPtr MemPtr;
3689  if (!EvaluateMemberPointer(RHS, MemPtr, Info))
3690  return nullptr;
3691 
3692  // C++11 [expr.mptr.oper]p6: If the second operand is the null pointer to
3693  // member value, the behavior is undefined.
3694  if (!MemPtr.getDecl()) {
3695  // FIXME: Specific diagnostic.
3696  Info.FFDiag(RHS);
3697  return nullptr;
3698  }
3699 
3700  if (MemPtr.isDerivedMember()) {
3701  // This is a member of some derived class. Truncate LV appropriately.
3702  // The end of the derived-to-base path for the base object must match the
3703  // derived-to-base path for the member pointer.
3704  if (LV.Designator.MostDerivedPathLength + MemPtr.Path.size() >
3705  LV.Designator.Entries.size()) {
3706  Info.FFDiag(RHS);
3707  return nullptr;
3708  }
3709  unsigned PathLengthToMember =
3710  LV.Designator.Entries.size() - MemPtr.Path.size();
3711  for (unsigned I = 0, N = MemPtr.Path.size(); I != N; ++I) {
3712  const CXXRecordDecl *LVDecl = getAsBaseClass(
3713  LV.Designator.Entries[PathLengthToMember + I]);
3714  const CXXRecordDecl *MPDecl = MemPtr.Path[I];
3715  if (LVDecl->getCanonicalDecl() != MPDecl->getCanonicalDecl()) {
3716  Info.FFDiag(RHS);
3717  return nullptr;
3718  }
3719  }
3720 
3721  // Truncate the lvalue to the appropriate derived class.
3722  if (!CastToDerivedClass(Info, RHS, LV, MemPtr.getContainingRecord(),
3723  PathLengthToMember))
3724  return nullptr;
3725  } else if (!MemPtr.Path.empty()) {
3726  // Extend the LValue path with the member pointer's path.
3727  LV.Designator.Entries.reserve(LV.Designator.Entries.size() +
3728  MemPtr.Path.size() + IncludeMember);
3729 
3730  // Walk down to the appropriate base class.
3731  if (const PointerType *PT = LVType->getAs<PointerType>())
3732  LVType = PT->getPointeeType();
3733  const CXXRecordDecl *RD = LVType->getAsCXXRecordDecl();
3734  assert(RD && "member pointer access on non-class-type expression");
3735  // The first class in the path is that of the lvalue.
3736  for (unsigned I = 1, N = MemPtr.Path.size(); I != N; ++I) {
3737  const CXXRecordDecl *Base = MemPtr.Path[N - I - 1];
3738  if (!HandleLValueDirectBase(Info, RHS, LV, RD, Base))
3739  return nullptr;
3740  RD = Base;
3741  }
3742  // Finally cast to the class containing the member.
3743  if (!HandleLValueDirectBase(Info, RHS, LV, RD,
3744  MemPtr.getContainingRecord()))
3745  return nullptr;
3746  }
3747 
3748  // Add the member. Note that we cannot build bound member functions here.
3749  if (IncludeMember) {
3750  if (const FieldDecl *FD = dyn_cast<FieldDecl>(MemPtr.getDecl())) {
3751  if (!HandleLValueMember(Info, RHS, LV, FD))
3752  return nullptr;
3753  } else if (const IndirectFieldDecl *IFD =
3754  dyn_cast<IndirectFieldDecl>(MemPtr.getDecl())) {
3755  if (!HandleLValueIndirectMember(Info, RHS, LV, IFD))
3756  return nullptr;
3757  } else {
3758  llvm_unreachable("can't construct reference to bound member function");
3759  }
3760  }
3761 
3762  return MemPtr.getDecl();
3763 }
3764 
3765 static const ValueDecl *HandleMemberPointerAccess(EvalInfo &Info,
3766  const BinaryOperator *BO,
3767  LValue &LV,
3768  bool IncludeMember = true) {
3769  assert(BO->getOpcode() == BO_PtrMemD || BO->getOpcode() == BO_PtrMemI);
3770 
3771  if (!EvaluateObjectArgument(Info, BO->getLHS(), LV)) {
3772  if (Info.noteFailure()) {
3773  MemberPtr MemPtr;
3774  EvaluateMemberPointer(BO->getRHS(), MemPtr, Info);
3775  }
3776  return nullptr;
3777  }
3778 
3779  return HandleMemberPointerAccess(Info, BO->getLHS()->getType(), LV,
3780  BO->getRHS(), IncludeMember);
3781 }
3782 
3783 /// HandleBaseToDerivedCast - Apply the given base-to-derived cast operation on
3784 /// the provided lvalue, which currently refers to the base object.
3785 static bool HandleBaseToDerivedCast(EvalInfo &Info, const CastExpr *E,
3786  LValue &Result) {
3787  SubobjectDesignator &D = Result.Designator;
3788  if (D.Invalid || !Result.checkNullPointer(Info, E, CSK_Derived))
3789  return false;
3790 
3791  QualType TargetQT = E->getType();
3792  if (const PointerType *PT = TargetQT->getAs<PointerType>())
3793  TargetQT = PT->getPointeeType();
3794 
3795  // Check this cast lands within the final derived-to-base subobject path.
3796  if (D.MostDerivedPathLength + E->path_size() > D.Entries.size()) {
3797  Info.CCEDiag(E, diag::note_constexpr_invalid_downcast)
3798  << D.MostDerivedType << TargetQT;
3799  return false;
3800  }
3801 
3802  // Check the type of the final cast. We don't need to check the path,
3803  // since a cast can only be formed if the path is unique.
3804  unsigned NewEntriesSize = D.Entries.size() - E->path_size();
3805  const CXXRecordDecl *TargetType = TargetQT->getAsCXXRecordDecl();
3806  const CXXRecordDecl *FinalType;
3807  if (NewEntriesSize == D.MostDerivedPathLength)
3808  FinalType = D.MostDerivedType->getAsCXXRecordDecl();
3809  else
3810  FinalType = getAsBaseClass(D.Entries[NewEntriesSize - 1]);
3811  if (FinalType->getCanonicalDecl() != TargetType->getCanonicalDecl()) {
3812  Info.CCEDiag(E, diag::note_constexpr_invalid_downcast)
3813  << D.MostDerivedType << TargetQT;
3814  return false;
3815  }
3816 
3817  // Truncate the lvalue to the appropriate derived class.
3818  return CastToDerivedClass(Info, E, Result, TargetType, NewEntriesSize);
3819 }
3820 
3821 namespace {
3823  /// Evaluation failed.
3824  ESR_Failed,
3825  /// Hit a 'return' statement.
3826  ESR_Returned,
3827  /// Evaluation succeeded.
3828  ESR_Succeeded,
3829  /// Hit a 'continue' statement.
3830  ESR_Continue,
3831  /// Hit a 'break' statement.
3832  ESR_Break,
3833  /// Still scanning for 'case' or 'default' statement.
3834  ESR_CaseNotFound
3835 };
3836 }
3837 
3838 static bool EvaluateVarDecl(EvalInfo &Info, const VarDecl *VD) {
3839  // We don't need to evaluate the initializer for a static local.
3840  if (!VD->hasLocalStorage())
3841  return true;
3842 
3843  LValue Result;
3844  APValue &Val = createTemporary(VD, true, Result, *Info.CurrentCall);
3845 
3846  const Expr *InitE = VD->getInit();
3847  if (!InitE) {
3848  Info.FFDiag(VD->getBeginLoc(), diag::note_constexpr_uninitialized)
3849  << false << VD->getType();
3850  Val = APValue();
3851  return false;
3852  }
3853 
3854  if (InitE->isValueDependent())
3855  return false;
3856 
3857  if (!EvaluateInPlace(Val, Info, Result, InitE)) {
3858  // Wipe out any partially-computed value, to allow tracking that this
3859  // evaluation failed.
3860  Val = APValue();
3861  return false;
3862  }
3863 
3864  return true;
3865 }
3866 
3867 static bool EvaluateDecl(EvalInfo &Info, const Decl *D) {
3868  bool OK = true;
3869 
3870  if (const VarDecl *VD = dyn_cast<VarDecl>(D))
3871  OK &= EvaluateVarDecl(Info, VD);
3872 
3873  if (const DecompositionDecl *DD = dyn_cast<DecompositionDecl>(D))
3874  for (auto *BD : DD->bindings())
3875  if (auto *VD = BD->getHoldingVar())
3876  OK &= EvaluateDecl(Info, VD);
3877 
3878  return OK;
3879 }
3880 
3881 
3882 /// Evaluate a condition (either a variable declaration or an expression).
3883 static bool EvaluateCond(EvalInfo &Info, const VarDecl *CondDecl,
3884  const Expr *Cond, bool &Result) {
3885  FullExpressionRAII Scope(Info);
3886  if (CondDecl && !EvaluateDecl(Info, CondDecl))
3887  return false;
3888  return EvaluateAsBooleanCondition(Cond, Result, Info);
3889 }
3890 
3891 namespace {
3892 /// A location where the result (returned value) of evaluating a
3893 /// statement should be stored.
3894 struct StmtResult {
3895  /// The APValue that should be filled in with the returned value.
3896  APValue &Value;
3897  /// The location containing the result, if any (used to support RVO).
3898  const LValue *Slot;
3899 };
3900 
3901 struct TempVersionRAII {
3902  CallStackFrame &Frame;
3903 
3904  TempVersionRAII(CallStackFrame &Frame) : Frame(Frame) {
3905  Frame.pushTempVersion();
3906  }
3907 
3908  ~TempVersionRAII() {
3909  Frame.popTempVersion();
3910  }
3911 };
3912 
3913 }
3914 
3915 static EvalStmtResult EvaluateStmt(StmtResult &Result, EvalInfo &Info,
3916  const Stmt *S,
3917  const SwitchCase *SC = nullptr);
3918 
3919 /// Evaluate the body of a loop, and translate the result as appropriate.
3920 static EvalStmtResult EvaluateLoopBody(StmtResult &Result, EvalInfo &Info,
3921  const Stmt *Body,
3922  const SwitchCase *Case = nullptr) {
3923  BlockScopeRAII Scope(Info);
3924  switch (EvalStmtResult ESR = EvaluateStmt(Result, Info, Body, Case)) {
3925  case ESR_Break:
3926  return ESR_Succeeded;
3927  case ESR_Succeeded:
3928  case ESR_Continue:
3929  return ESR_Continue;
3930  case ESR_Failed:
3931  case ESR_Returned:
3932  case ESR_CaseNotFound:
3933  return ESR;
3934  }
3935  llvm_unreachable("Invalid EvalStmtResult!");
3936 }
3937 
3938 /// Evaluate a switch statement.
3939 static EvalStmtResult EvaluateSwitch(StmtResult &Result, EvalInfo &Info,
3940  const SwitchStmt *SS) {
3941  BlockScopeRAII Scope(Info);
3942 
3943  // Evaluate the switch condition.
3944  APSInt Value;
3945  {
3946  FullExpressionRAII Scope(Info);
3947  if (const Stmt *Init = SS->getInit()) {
3948  EvalStmtResult ESR = EvaluateStmt(Result, Info, Init);
3949  if (ESR != ESR_Succeeded)
3950  return ESR;
3951  }
3952  if (SS->getConditionVariable() &&
3953  !EvaluateDecl(Info, SS->getConditionVariable()))
3954  return ESR_Failed;
3955  if (!EvaluateInteger(SS->getCond(), Value, Info))
3956  return ESR_Failed;
3957  }
3958 
3959  // Find the switch case corresponding to the value of the condition.
3960  // FIXME: Cache this lookup.
3961  const SwitchCase *Found = nullptr;
3962  for (const SwitchCase *SC = SS->getSwitchCaseList(); SC;
3963  SC = SC->getNextSwitchCase()) {
3964  if (isa<DefaultStmt>(SC)) {
3965  Found = SC;
3966  continue;
3967  }
3968 
3969  const CaseStmt *CS = cast<CaseStmt>(SC);
3970  APSInt LHS = CS->getLHS()->EvaluateKnownConstInt(Info.Ctx);
3971  APSInt RHS = CS->getRHS() ? CS->getRHS()->EvaluateKnownConstInt(Info.Ctx)
3972  : LHS;
3973  if (LHS <= Value && Value <= RHS) {
3974  Found = SC;
3975  break;
3976  }
3977  }
3978 
3979  if (!Found)
3980  return ESR_Succeeded;
3981 
3982  // Search the switch body for the switch case and evaluate it from there.
3983  switch (EvalStmtResult ESR = EvaluateStmt(Result, Info, SS->getBody(), Found)) {
3984  case ESR_Break:
3985  return ESR_Succeeded;
3986  case ESR_Succeeded:
3987  case ESR_Continue:
3988  case ESR_Failed:
3989  case ESR_Returned:
3990  return ESR;
3991  case ESR_CaseNotFound:
3992  // This can only happen if the switch case is nested within a statement
3993  // expression. We have no intention of supporting that.
3994  Info.FFDiag(Found->getBeginLoc(),
3995  diag::note_constexpr_stmt_expr_unsupported);
3996  return ESR_Failed;
3997  }
3998  llvm_unreachable("Invalid EvalStmtResult!");
3999 }
4000 
4001 // Evaluate a statement.
4002 static EvalStmtResult EvaluateStmt(StmtResult &Result, EvalInfo &Info,
4003  const Stmt *S, const SwitchCase *Case) {
4004  if (!Info.nextStep(S))
4005  return ESR_Failed;
4006 
4007  // If we're hunting down a 'case' or 'default' label, recurse through
4008  // substatements until we hit the label.
4009  if (Case) {
4010  // FIXME: We don't start the lifetime of objects whose initialization we
4011  // jump over. However, such objects must be of class type with a trivial
4012  // default constructor that initialize all subobjects, so must be empty,
4013  // so this almost never matters.
4014  switch (S->getStmtClass()) {
4015  case Stmt::CompoundStmtClass:
4016  // FIXME: Precompute which substatement of a compound statement we
4017  // would jump to, and go straight there rather than performing a
4018  // linear scan each time.
4019  case Stmt::LabelStmtClass:
4020  case Stmt::AttributedStmtClass:
4021  case Stmt::DoStmtClass:
4022  break;
4023 
4024  case Stmt::CaseStmtClass:
4025  case Stmt::DefaultStmtClass:
4026  if (Case == S)
4027  Case = nullptr;
4028  break;
4029 
4030  case Stmt::IfStmtClass: {
4031  // FIXME: Precompute which side of an 'if' we would jump to, and go
4032  // straight there rather than scanning both sides.
4033  const IfStmt *IS = cast<IfStmt>(S);
4034 
4035  // Wrap the evaluation in a block scope, in case it's a DeclStmt
4036  // preceded by our switch label.
4037  BlockScopeRAII Scope(Info);
4038 
4039  EvalStmtResult ESR = EvaluateStmt(Result, Info, IS->getThen(), Case);
4040  if (ESR != ESR_CaseNotFound || !IS->getElse())
4041  return ESR;
4042  return EvaluateStmt(Result, Info, IS->getElse(), Case);
4043  }
4044 
4045  case Stmt::WhileStmtClass: {
4046  EvalStmtResult ESR =
4047  EvaluateLoopBody(Result, Info, cast<WhileStmt>(S)->getBody(), Case);
4048  if (ESR != ESR_Continue)
4049  return ESR;
4050  break;
4051  }
4052 
4053  case Stmt::ForStmtClass: {
4054  const ForStmt *FS = cast<ForStmt>(S);
4055  EvalStmtResult ESR =
4056  EvaluateLoopBody(Result, Info, FS->getBody(), Case);
4057  if (ESR != ESR_Continue)
4058  return ESR;
4059  if (FS->getInc()) {
4060  FullExpressionRAII IncScope(Info);
4061  if (!EvaluateIgnoredValue(Info, FS->getInc()))
4062  return ESR_Failed;
4063  }
4064  break;
4065  }
4066 
4067  case Stmt::DeclStmtClass:
4068  // FIXME: If the variable has initialization that can't be jumped over,
4069  // bail out of any immediately-surrounding compound-statement too.
4070  default:
4071  return ESR_CaseNotFound;
4072  }
4073  }
4074 
4075  switch (S->getStmtClass()) {
4076  default:
4077  if (const Expr *E = dyn_cast<Expr>(S)) {
4078  // Don't bother evaluating beyond an expression-statement which couldn't
4079  // be evaluated.
4080  FullExpressionRAII Scope(Info);
4081  if (!EvaluateIgnoredValue(Info, E))
4082  return ESR_Failed;
4083  return ESR_Succeeded;
4084  }
4085 
4086  Info.FFDiag(S->getBeginLoc());
4087  return ESR_Failed;
4088 
4089  case Stmt::NullStmtClass:
4090  return ESR_Succeeded;
4091 
4092  case Stmt::DeclStmtClass: {
4093  const DeclStmt *DS = cast<DeclStmt>(S);
4094  for (const auto *DclIt : DS->decls()) {
4095  // Each declaration initialization is its own full-expression.
4096  // FIXME: This isn't quite right; if we're performing aggregate
4097  // initialization, each braced subexpression is its own full-expression.
4098  FullExpressionRAII Scope(Info);
4099  if (!EvaluateDecl(Info, DclIt) && !Info.noteFailure())
4100  return ESR_Failed;
4101  }
4102  return ESR_Succeeded;
4103  }
4104 
4105  case Stmt::ReturnStmtClass: {
4106  const Expr *RetExpr = cast<ReturnStmt>(S)->getRetValue();
4107  FullExpressionRAII Scope(Info);
4108  if (RetExpr &&
4109  !(Result.Slot
4110  ? EvaluateInPlace(Result.Value, Info, *Result.Slot, RetExpr)
4111  : Evaluate(Result.Value, Info, RetExpr)))
4112  return ESR_Failed;
4113  return ESR_Returned;
4114  }
4115 
4116  case Stmt::CompoundStmtClass: {
4117  BlockScopeRAII Scope(Info);
4118 
4119  const CompoundStmt *CS = cast<CompoundStmt>(S);
4120  for (const auto *BI : CS->body()) {
4121  EvalStmtResult ESR = EvaluateStmt(Result, Info, BI, Case);
4122  if (ESR == ESR_Succeeded)
4123  Case = nullptr;
4124  else if (ESR != ESR_CaseNotFound)
4125  return ESR;
4126  }
4127  return Case ? ESR_CaseNotFound : ESR_Succeeded;
4128  }
4129 
4130  case Stmt::IfStmtClass: {
4131  const IfStmt *IS = cast<IfStmt>(S);
4132 
4133  // Evaluate the condition, as either a var decl or as an expression.
4134  BlockScopeRAII Scope(Info);
4135  if (const Stmt *Init = IS->getInit()) {
4136  EvalStmtResult ESR = EvaluateStmt(Result, Info, Init);
4137  if (ESR != ESR_Succeeded)
4138  return ESR;
4139  }
4140  bool Cond;
4141  if (!EvaluateCond(Info, IS->getConditionVariable(), IS->getCond(), Cond))
4142  return ESR_Failed;
4143 
4144  if (const Stmt *SubStmt = Cond ? IS->getThen() : IS->getElse()) {
4145  EvalStmtResult ESR = EvaluateStmt(Result, Info, SubStmt);
4146  if (ESR != ESR_Succeeded)
4147  return ESR;
4148  }
4149  return ESR_Succeeded;
4150  }
4151 
4152  case Stmt::WhileStmtClass: {
4153  const WhileStmt *WS = cast<WhileStmt>(S);
4154  while (true) {
4155  BlockScopeRAII Scope(Info);
4156  bool Continue;
4157  if (!EvaluateCond(Info, WS->getConditionVariable(), WS->getCond(),
4158  Continue))
4159  return ESR_Failed;
4160  if (!Continue)
4161  break;
4162 
4163  EvalStmtResult ESR = EvaluateLoopBody(Result, Info, WS->getBody());
4164  if (ESR != ESR_Continue)
4165  return ESR;
4166  }
4167  return ESR_Succeeded;
4168  }
4169 
4170  case Stmt::DoStmtClass: {
4171  const DoStmt *DS = cast<DoStmt>(S);
4172  bool Continue;
4173  do {
4174  EvalStmtResult ESR = EvaluateLoopBody(Result, Info, DS->getBody(), Case);
4175  if (ESR != ESR_Continue)
4176  return ESR;
4177  Case = nullptr;
4178 
4179  FullExpressionRAII CondScope(Info);
4180  if (!EvaluateAsBooleanCondition(DS->getCond(), Continue, Info))
4181  return ESR_Failed;
4182  } while (Continue);
4183  return ESR_Succeeded;
4184  }
4185 
4186  case Stmt::ForStmtClass: {
4187  const ForStmt *FS = cast<ForStmt>(S);
4188  BlockScopeRAII Scope(Info);
4189  if (FS->getInit()) {
4190  EvalStmtResult ESR = EvaluateStmt(Result, Info, FS->getInit());
4191  if (ESR != ESR_Succeeded)
4192  return ESR;
4193  }
4194  while (true) {
4195  BlockScopeRAII Scope(Info);
4196  bool Continue = true;
4197  if (FS->getCond() && !EvaluateCond(Info, FS->getConditionVariable(),
4198  FS->getCond(), Continue))
4199  return ESR_Failed;
4200  if (!Continue)
4201  break;
4202 
4203  EvalStmtResult ESR = EvaluateLoopBody(Result, Info, FS->getBody());
4204  if (ESR != ESR_Continue)
4205  return ESR;
4206 
4207  if (FS->getInc()) {
4208  FullExpressionRAII IncScope(Info);
4209  if (!EvaluateIgnoredValue(Info, FS->getInc()))
4210  return ESR_Failed;
4211  }
4212  }
4213  return ESR_Succeeded;
4214  }
4215 
4216  case Stmt::CXXForRangeStmtClass: {
4217  const CXXForRangeStmt *FS = cast<CXXForRangeStmt>(S);
4218  BlockScopeRAII Scope(Info);
4219 
4220  // Initialize the __range variable.
4221  EvalStmtResult ESR = EvaluateStmt(Result, Info, FS->getRangeStmt());
4222  if (ESR != ESR_Succeeded)
4223  return ESR;
4224 
4225  // Create the __begin and __end iterators.
4226  ESR = EvaluateStmt(Result, Info, FS->getBeginStmt());
4227  if (ESR != ESR_Succeeded)
4228  return ESR;
4229  ESR = EvaluateStmt(Result, Info, FS->getEndStmt());
4230  if (ESR != ESR_Succeeded)
4231  return ESR;
4232 
4233  while (true) {
4234  // Condition: __begin != __end.
4235  {
4236  bool Continue = true;
4237  FullExpressionRAII CondExpr(Info);
4238  if (!EvaluateAsBooleanCondition(FS->getCond(), Continue, Info))
4239  return ESR_Failed;
4240  if (!Continue)
4241  break;
4242  }
4243 
4244  // User's variable declaration, initialized by *__begin.
4245  BlockScopeRAII InnerScope(Info);
4246  ESR = EvaluateStmt(Result, Info, FS->getLoopVarStmt());
4247  if (ESR != ESR_Succeeded)
4248  return ESR;
4249 
4250  // Loop body.
4251  ESR = EvaluateLoopBody(Result, Info, FS->getBody());
4252  if (ESR != ESR_Continue)
4253  return ESR;
4254 
4255  // Increment: ++__begin
4256  if (!EvaluateIgnoredValue(Info, FS->getInc()))
4257  return ESR_Failed;
4258  }
4259 
4260  return ESR_Succeeded;
4261  }
4262 
4263  case Stmt::SwitchStmtClass:
4264  return EvaluateSwitch(Result, Info, cast<SwitchStmt>(S));
4265 
4266  case Stmt::ContinueStmtClass:
4267  return ESR_Continue;
4268 
4269  case Stmt::BreakStmtClass:
4270  return ESR_Break;
4271 
4272  case Stmt::LabelStmtClass:
4273  return EvaluateStmt(Result, Info, cast<LabelStmt>(S)->getSubStmt(), Case);
4274 
4275  case Stmt::AttributedStmtClass:
4276  // As a general principle, C++11 attributes can be ignored without
4277  // any semantic impact.
4278  return EvaluateStmt(Result, Info, cast<AttributedStmt>(S)->getSubStmt(),
4279  Case);
4280 
4281  case Stmt::CaseStmtClass:
4282  case Stmt::DefaultStmtClass:
4283  return EvaluateStmt(Result, Info, cast<SwitchCase>(S)->getSubStmt(), Case);
4284  }
4285 }
4286 
4287 /// CheckTrivialDefaultConstructor - Check whether a constructor is a trivial
4288 /// default constructor. If so, we'll fold it whether or not it's marked as
4289 /// constexpr. If it is marked as constexpr, we will never implicitly define it,
4290 /// so we need special handling.
4291 static bool CheckTrivialDefaultConstructor(EvalInfo &Info, SourceLocation Loc,
4292  const CXXConstructorDecl *CD,
4293  bool IsValueInitialization) {
4294  if (!CD->isTrivial() || !CD->isDefaultConstructor())
4295  return false;
4296 
4297  // Value-initialization does not call a trivial default constructor, so such a
4298  // call is a core constant expression whether or not the constructor is
4299  // constexpr.
4300  if (!CD->isConstexpr() && !IsValueInitialization) {
4301  if (Info.getLangOpts().CPlusPlus11) {
4302  // FIXME: If DiagDecl is an implicitly-declared special member function,
4303  // we should be much more explicit about why it's not constexpr.
4304  Info.CCEDiag(Loc, diag::note_constexpr_invalid_function, 1)
4305  << /*IsConstexpr*/0 << /*IsConstructor*/1 << CD;
4306  Info.Note(CD->getLocation(), diag::note_declared_at);
4307  } else {
4308  Info.CCEDiag(Loc, diag::note_invalid_subexpr_in_const_expr);
4309  }
4310  }
4311  return true;
4312 }
4313 
4314 /// CheckConstexprFunction - Check that a function can be called in a constant
4315 /// expression.
4316 static bool CheckConstexprFunction(EvalInfo &Info, SourceLocation CallLoc,
4317  const FunctionDecl *Declaration,
4318  const FunctionDecl *Definition,
4319  const Stmt *Body) {
4320  // Potential constant expressions can contain calls to declared, but not yet
4321  // defined, constexpr functions.
4322  if (Info.checkingPotentialConstantExpression() && !Definition &&
4323  Declaration->isConstexpr())
4324  return false;
4325 
4326  // Bail out with no diagnostic if the function declaration itself is invalid.
4327  // We will have produced a relevant diagnostic while parsing it.
4328  if (Declaration->isInvalidDecl())
4329  return false;
4330 
4331  // Can we evaluate this function call?
4332  if (Definition && Definition->isConstexpr() &&
4333  !Definition->isInvalidDecl() && Body)
4334  return true;
4335 
4336  if (Info.getLangOpts().CPlusPlus11) {
4337  const FunctionDecl *DiagDecl = Definition ? Definition : Declaration;
4338 
4339  // If this function is not constexpr because it is an inherited
4340  // non-constexpr constructor, diagnose that directly.
4341  auto *CD = dyn_cast<CXXConstructorDecl>(DiagDecl);
4342  if (CD && CD->isInheritingConstructor()) {
4343  auto *Inherited = CD->getInheritedConstructor().getConstructor();
4344  if (!Inherited->isConstexpr())
4345  DiagDecl = CD = Inherited;
4346  }
4347 
4348  // FIXME: If DiagDecl is an implicitly-declared special member function
4349  // or an inheriting constructor, we should be much more explicit about why
4350  // it's not constexpr.
4351  if (CD && CD->isInheritingConstructor())
4352  Info.FFDiag(CallLoc, diag::note_constexpr_invalid_inhctor, 1)
4353  << CD->getInheritedConstructor().getConstructor()->getParent();
4354  else
4355  Info.FFDiag(CallLoc, diag::note_constexpr_invalid_function, 1)
4356  << DiagDecl->isConstexpr() << (bool)CD << DiagDecl;
4357  Info.Note(DiagDecl->getLocation(), diag::note_declared_at);
4358  } else {
4359  Info.FFDiag(CallLoc, diag::note_invalid_subexpr_in_const_expr);
4360  }
4361  return false;
4362 }
4363 
4364 /// Determine if a class has any fields that might need to be copied by a
4365 /// trivial copy or move operation.
4366 static bool hasFields(const CXXRecordDecl *RD) {
4367  if (!RD || RD->isEmpty())
4368  return false;
4369  for (auto *FD : RD->fields()) {
4370  if (FD->isUnnamedBitfield())
4371  continue;
4372  return true;
4373  }
4374  for (auto &Base : RD->bases())
4375  if (hasFields(Base.getType()->getAsCXXRecordDecl()))
4376  return true;
4377  return false;
4378 }
4379 
4380 namespace {
4381 typedef SmallVector<APValue, 8> ArgVector;
4382 }
4383 
4384 /// EvaluateArgs - Evaluate the arguments to a function call.
4385 static bool EvaluateArgs(ArrayRef<const Expr*> Args, ArgVector &ArgValues,
4386  EvalInfo &Info) {
4387  bool Success = true;
4388  for (ArrayRef<const Expr*>::iterator I = Args.begin(), E = Args.end();
4389  I != E; ++I) {
4390  if (!Evaluate(ArgValues[I - Args.begin()], Info, *I)) {
4391  // If we're checking for a potential constant expression, evaluate all
4392  // initializers even if some of them fail.
4393  if (!Info.noteFailure())
4394  return false;
4395  Success = false;
4396  }
4397  }
4398  return Success;
4399 }
4400 
4401 /// Evaluate a function call.
4403  const FunctionDecl *Callee, const LValue *This,
4404  ArrayRef<const Expr*> Args, const Stmt *Body,
4405  EvalInfo &Info, APValue &Result,
4406  const LValue *ResultSlot) {
4407  ArgVector ArgValues(Args.size());
4408  if (!EvaluateArgs(Args, ArgValues, Info))
4409  return false;
4410 
4411  if (!Info.CheckCallLimit(CallLoc))
4412  return false;
4413 
4414  CallStackFrame Frame(Info, CallLoc, Callee, This, ArgValues.data());
4415 
4416  // For a trivial copy or move assignment, perform an APValue copy. This is
4417  // essential for unions, where the operations performed by the assignment
4418  // operator cannot be represented as statements.
4419  //
4420  // Skip this for non-union classes with no fields; in that case, the defaulted
4421  // copy/move does not actually read the object.
4422  const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(Callee);
4423  if (MD && MD->isDefaulted() &&
4424  (MD->getParent()->isUnion() ||
4425  (MD->isTrivial() && hasFields(MD->getParent())))) {
4426  assert(This &&
4427  (MD->isCopyAssignmentOperator() || MD->isMoveAssignmentOperator()));
4428  LValue RHS;
4429  RHS.setFrom(Info.Ctx, ArgValues[0]);
4430  APValue RHSValue;
4431  if (!handleLValueToRValueConversion(Info, Args[0], Args[0]->getType(),
4432  RHS, RHSValue))
4433  return false;
4434  if (!handleAssignment(Info, Args[0], *This, MD->getThisType(Info.Ctx),
4435  RHSValue))
4436  return false;
4437  This->moveInto(Result);
4438  return true;
4439  } else if (MD && isLambdaCallOperator(MD)) {
4440  // We're in a lambda; determine the lambda capture field maps unless we're
4441  // just constexpr checking a lambda's call operator. constexpr checking is
4442  // done before the captures have been added to the closure object (unless
4443  // we're inferring constexpr-ness), so we don't have access to them in this
4444  // case. But since we don't need the captures to constexpr check, we can
4445  // just ignore them.
4446  if (!Info.checkingPotentialConstantExpression())
4447  MD->getParent()->getCaptureFields(Frame.LambdaCaptureFields,
4448  Frame.LambdaThisCaptureField);
4449  }
4450 
4451  StmtResult Ret = {Result, ResultSlot};
4452  EvalStmtResult ESR = EvaluateStmt(Ret, Info, Body);
4453  if (ESR == ESR_Succeeded) {
4454  if (Callee->getReturnType()->isVoidType())
4455  return true;
4456  Info.FFDiag(Callee->getEndLoc(), diag::note_constexpr_no_return);
4457  }
4458  return ESR == ESR_Returned;
4459 }
4460 
4461 /// Evaluate a constructor call.
4462 static bool HandleConstructorCall(const Expr *E, const LValue &This,
4463  APValue *ArgValues,
4464  const CXXConstructorDecl *Definition,
4465  EvalInfo &Info, APValue &Result) {
4466  SourceLocation CallLoc = E->getExprLoc();
4467  if (!Info.CheckCallLimit(CallLoc))
4468  return false;
4469 
4470  const CXXRecordDecl *RD = Definition->getParent();
4471  if (RD->getNumVBases()) {
4472  Info.FFDiag(CallLoc, diag::note_constexpr_virtual_base) << RD;
4473  return false;
4474  }
4475 
4476  EvalInfo::EvaluatingConstructorRAII EvalObj(
4477  Info, {This.getLValueBase(),
4478  {This.getLValueCallIndex(), This.getLValueVersion()}});
4479  CallStackFrame Frame(Info, CallLoc, Definition, &This, ArgValues);
4480 
4481  // FIXME: Creating an APValue just to hold a nonexistent return value is
4482  // wasteful.
4483  APValue RetVal;
4484  StmtResult Ret = {RetVal, nullptr};
4485 
4486  // If it's a delegating constructor, delegate.
4487  if (Definition->isDelegatingConstructor()) {
4489  {
4490  FullExpressionRAII InitScope(Info);
4491  if (!EvaluateInPlace(Result, Info, This, (*I)->getInit()))
4492  return false;
4493  }
4494  return EvaluateStmt(Ret, Info, Definition->getBody()) != ESR_Failed;
4495  }
4496 
4497  // For a trivial copy or move constructor, perform an APValue copy. This is
4498  // essential for unions (or classes with anonymous union members), where the
4499  // operations performed by the constructor cannot be represented by
4500  // ctor-initializers.
4501  //
4502  // Skip this for empty non-union classes; we should not perform an
4503  // lvalue-to-rvalue conversion on them because their copy constructor does not
4504  // actually read them.
4505  if (Definition->isDefaulted() && Definition->isCopyOrMoveConstructor() &&
4506  (Definition->getParent()->isUnion() ||
4507  (Definition->isTrivial() && hasFields(Definition->getParent())))) {
4508  LValue RHS;
4509  RHS.setFrom(Info.Ctx, ArgValues[0]);
4511  Info, E, Definition->getParamDecl(0)->getType().getNonReferenceType(),
4512  RHS, Result);
4513  }
4514 
4515  // Reserve space for the struct members.
4516  if (!RD->isUnion() && Result.isUninit())
4517  Result = APValue(APValue::UninitStruct(), RD->getNumBases(),
4518  std::distance(RD->field_begin(), RD->field_end()));
4519 
4520  if (RD->isInvalidDecl()) return false;
4521  const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
4522 
4523  // A scope for temporaries lifetime-extended by reference members.
4524  BlockScopeRAII LifetimeExtendedScope(Info);
4525 
4526  bool Success = true;
4527  unsigned BasesSeen = 0;
4528 #ifndef NDEBUG
4530 #endif
4531  for (const auto *I : Definition->inits()) {
4532  LValue Subobject = This;
4533  LValue SubobjectParent = This;
4534  APValue *Value = &Result;
4535 
4536  // Determine the subobject to initialize.
4537  FieldDecl *FD = nullptr;
4538  if (I->isBaseInitializer()) {
4539  QualType BaseType(I->getBaseClass(), 0);
4540 #ifndef NDEBUG
4541  // Non-virtual base classes are initialized in the order in the class
4542  // definition. We have already checked for virtual base classes.
4543  assert(!BaseIt->isVirtual() && "virtual base for literal type");
4544  assert(Info.Ctx.hasSameType(BaseIt->getType(), BaseType) &&
4545  "base class initializers not in expected order");
4546  ++BaseIt;
4547 #endif
4548  if (!HandleLValueDirectBase(Info, I->getInit(), Subobject, RD,
4549  BaseType->getAsCXXRecordDecl(), &Layout))
4550  return false;
4551  Value = &Result.getStructBase(BasesSeen++);
4552  } else if ((FD = I->getMember())) {
4553  if (!HandleLValueMember(Info, I->getInit(), Subobject, FD, &Layout))
4554  return false;
4555  if (RD->isUnion()) {
4556  Result = APValue(FD);
4557  Value = &Result.getUnionValue();
4558  } else {
4559  Value = &Result.getStructField(FD->getFieldIndex());
4560  }
4561  } else if (IndirectFieldDecl *IFD = I->getIndirectMember()) {
4562  // Walk the indirect field decl's chain to find the object to initialize,
4563  // and make sure we've initialized every step along it.
4564  auto IndirectFieldChain = IFD->chain();
4565  for (auto *C : IndirectFieldChain) {
4566  FD = cast<FieldDecl>(C);
4567  CXXRecordDecl *CD = cast<CXXRecordDecl>(FD->getParent());
4568  // Switch the union field if it differs. This happens if we had
4569  // preceding zero-initialization, and we're now initializing a union
4570  // subobject other than the first.
4571  // FIXME: In this case, the values of the other subobjects are
4572  // specified, since zero-initialization sets all padding bits to zero.
4573  if (Value->isUninit() ||
4574  (Value->isUnion() && Value->getUnionField() != FD)) {
4575  if (CD->isUnion())
4576  *Value = APValue(FD);
4577  else
4578  *Value = APValue(APValue::UninitStruct(), CD->getNumBases(),
4579  std::distance(CD->field_begin(), CD->field_end()));
4580  }
4581  // Store Subobject as its parent before updating it for the last element
4582  // in the chain.
4583  if (C == IndirectFieldChain.back())
4584  SubobjectParent = Subobject;
4585  if (!HandleLValueMember(Info, I->getInit(), Subobject, FD))
4586  return false;
4587  if (CD->isUnion())
4588  Value = &Value->getUnionValue();
4589  else
4590  Value = &Value->getStructField(FD->getFieldIndex());
4591  }
4592  } else {
4593  llvm_unreachable("unknown base initializer kind");
4594  }
4595 
4596  // Need to override This for implicit field initializers as in this case
4597  // This refers to innermost anonymous struct/union containing initializer,
4598  // not to currently constructed class.
4599  const Expr *Init = I->getInit();
4600  ThisOverrideRAII ThisOverride(*Info.CurrentCall, &SubobjectParent,
4601  isa<CXXDefaultInitExpr>(Init));
4602  FullExpressionRAII InitScope(Info);
4603  if (!EvaluateInPlace(*Value, Info, Subobject, Init) ||
4604  (FD && FD->isBitField() &&
4605  !truncateBitfieldValue(Info, Init, *Value, FD))) {
4606  // If we're checking for a potential constant expression, evaluate all
4607  // initializers even if some of them fail.
4608  if (!Info.noteFailure())
4609  return false;
4610  Success = false;
4611  }
4612  }
4613 
4614  return Success &&
4615  EvaluateStmt(Ret, Info, Definition->getBody()) != ESR_Failed;
4616 }
4617 
4618 static bool HandleConstructorCall(const Expr *E, const LValue &This,
4619  ArrayRef<const Expr*> Args,
4620  const CXXConstructorDecl *Definition,
4621  EvalInfo &Info, APValue &Result) {
4622  ArgVector ArgValues(Args.size());
4623  if (!EvaluateArgs(Args, ArgValues, Info))
4624  return false;
4625 
4626  return HandleConstructorCall(E, This, ArgValues.data(), Definition,
4627  Info, Result);
4628 }
4629 
4630 //===----------------------------------------------------------------------===//
4631 // Generic Evaluation
4632 //===----------------------------------------------------------------------===//
4633 namespace {
4634 
4635 template <class Derived>
4636 class ExprEvaluatorBase
4637  : public ConstStmtVisitor<Derived, bool> {
4638 private:
4639  Derived &getDerived() { return static_cast<Derived&>(*this); }
4640  bool DerivedSuccess(const APValue &V, const Expr *E) {
4641  return getDerived().Success(V, E);
4642  }
4643  bool DerivedZeroInitialization(const Expr *E) {
4644  return getDerived().ZeroInitialization(E);
4645  }
4646 
4647  // Check whether a conditional operator with a non-constant condition is a
4648  // potential constant expression. If neither arm is a potential constant
4649  // expression, then the conditional operator is not either.
4650  template<typename ConditionalOperator>
4651  void CheckPotentialConstantConditional(const ConditionalOperator *E) {
4652  assert(Info.checkingPotentialConstantExpression());
4653 
4654  // Speculatively evaluate both arms.
4656  {
4657  SpeculativeEvaluationRAII Speculate(Info, &Diag);
4658  StmtVisitorTy::Visit(E->getFalseExpr());
4659  if (Diag.empty())
4660  return;
4661  }
4662 
4663  {
4664  SpeculativeEvaluationRAII Speculate(Info, &Diag);
4665  Diag.clear();
4666  StmtVisitorTy::Visit(E->getTrueExpr());
4667  if (Diag.empty())
4668  return;
4669  }
4670 
4671  Error(E, diag::note_constexpr_conditional_never_const);
4672  }
4673 
4674 
4675  template<typename ConditionalOperator>
4676  bool HandleConditionalOperator(const ConditionalOperator *E) {
4677  bool BoolResult;
4678  if (!EvaluateAsBooleanCondition(E->getCond(), BoolResult, Info)) {
4679  if (Info.checkingPotentialConstantExpression() && Info.noteFailure()) {
4680  CheckPotentialConstantConditional(E);
4681  return false;
4682  }
4683  if (Info.noteFailure()) {
4684  StmtVisitorTy::Visit(E->getTrueExpr());
4685  StmtVisitorTy::Visit(E->getFalseExpr());
4686  }
4687  return false;
4688  }
4689 
4690  Expr *EvalExpr = BoolResult ? E->getTrueExpr() : E->getFalseExpr();
4691  return StmtVisitorTy::Visit(EvalExpr);
4692  }
4693 
4694 protected:
4695  EvalInfo &Info;
4696  typedef ConstStmtVisitor<Derived, bool> StmtVisitorTy;
4697  typedef ExprEvaluatorBase ExprEvaluatorBaseTy;
4698 
4699  OptionalDiagnostic CCEDiag(const Expr *E, diag::kind D) {
4700  return Info.CCEDiag(E, D);
4701  }
4702 
4703  bool ZeroInitialization(const Expr *E) { return Error(E); }
4704 
4705 public:
4706  ExprEvaluatorBase(EvalInfo &Info) : Info(Info) {}
4707 
4708  EvalInfo &getEvalInfo() { return Info; }
4709 
4710  /// Report an evaluation error. This should only be called when an error is
4711  /// first discovered. When propagating an error, just return false.
4712  bool Error(const Expr *E, diag::kind D) {
4713  Info.FFDiag(E, D);
4714  return false;
4715  }
4716  bool Error(const Expr *E) {
4717  return Error(E, diag::note_invalid_subexpr_in_const_expr);
4718  }
4719 
4720  bool VisitStmt(const Stmt *) {
4721  llvm_unreachable("Expression evaluator should not be called on stmts");
4722  }
4723  bool VisitExpr(const Expr *E) {
4724  return Error(E);
4725  }
4726 
4727  bool VisitParenExpr(const ParenExpr *E)
4728  { return StmtVisitorTy::Visit(E->getSubExpr()); }
4729  bool VisitUnaryExtension(const UnaryOperator *E)
4730  { return StmtVisitorTy::Visit(E->getSubExpr()); }
4731  bool VisitUnaryPlus(const UnaryOperator *E)
4732  { return StmtVisitorTy::Visit(E->getSubExpr()); }
4733  bool VisitChooseExpr(const ChooseExpr *E)
4734  { return StmtVisitorTy::Visit(E->getChosenSubExpr()); }
4735  bool VisitGenericSelectionExpr(const GenericSelectionExpr *E)
4736  { return StmtVisitorTy::Visit(E->getResultExpr()); }
4737  bool VisitSubstNonTypeTemplateParmExpr(const SubstNonTypeTemplateParmExpr *E)
4738  { return StmtVisitorTy::Visit(E->getReplacement()); }
4739  bool VisitCXXDefaultArgExpr(const CXXDefaultArgExpr *E) {
4740  TempVersionRAII RAII(*Info.CurrentCall);
4741  return StmtVisitorTy::Visit(E->getExpr());
4742  }
4743  bool VisitCXXDefaultInitExpr(const CXXDefaultInitExpr *E) {
4744  TempVersionRAII RAII(*Info.CurrentCall);
4745  // The initializer may not have been parsed yet, or might be erroneous.
4746  if (!E->getExpr())
4747  return Error(E);
4748  return StmtVisitorTy::Visit(E->getExpr());
4749  }
4750  // We cannot create any objects for which cleanups are required, so there is
4751  // nothing to do here; all cleanups must come from unevaluated subexpressions.
4752  bool VisitExprWithCleanups(const ExprWithCleanups *E)
4753  { return StmtVisitorTy::Visit(E->getSubExpr()); }
4754 
4755  bool VisitCXXReinterpretCastExpr(const CXXReinterpretCastExpr *E) {
4756  CCEDiag(E, diag::note_constexpr_invalid_cast) << 0;
4757  return static_cast<Derived*>(this)->VisitCastExpr(E);
4758  }
4759  bool VisitCXXDynamicCastExpr(const CXXDynamicCastExpr *E) {
4760  CCEDiag(E, diag::note_constexpr_invalid_cast) << 1;
4761  return static_cast<Derived*>(this)->VisitCastExpr(E);
4762  }
4763 
4764  bool VisitBinaryOperator(const BinaryOperator *E) {
4765  switch (E->getOpcode()) {
4766  default:
4767  return Error(E);
4768 
4769  case BO_Comma:
4770  VisitIgnoredValue(E->getLHS());
4771  return StmtVisitorTy::Visit(E->getRHS());
4772 
4773  case BO_PtrMemD:
4774  case BO_PtrMemI: {
4775  LValue Obj;
4776  if (!HandleMemberPointerAccess(Info, E, Obj))
4777  return false;
4778  APValue Result;
4779  if (!handleLValueToRValueConversion(Info, E, E->getType(), Obj, Result))
4780  return false;
4781  return DerivedSuccess(Result, E);
4782  }
4783  }
4784  }
4785 
4786  bool VisitBinaryConditionalOperator(const BinaryConditionalOperator *E) {
4787  // Evaluate and cache the common expression. We treat it as a temporary,
4788  // even though it's not quite the same thing.
4789  if (!Evaluate(Info.CurrentCall->createTemporary(E->getOpaqueValue(), false),
4790  Info, E->getCommon()))
4791  return false;
4792 
4793  return HandleConditionalOperator(E);
4794  }
4795 
4796  bool VisitConditionalOperator(const ConditionalOperator *E) {
4797  bool IsBcpCall = false;
4798  // If the condition (ignoring parens) is a __builtin_constant_p call,
4799  // the result is a constant expression if it can be folded without
4800  // side-effects. This is an important GNU extension. See GCC PR38377
4801  // for discussion.
4802  if (const CallExpr *CallCE =
4803  dyn_cast<CallExpr>(E->getCond()->IgnoreParenCasts()))
4804  if (CallCE->getBuiltinCallee() == Builtin::BI__builtin_constant_p)
4805  IsBcpCall = true;
4806 
4807  // Always assume __builtin_constant_p(...) ? ... : ... is a potential
4808  // constant expression; we can't check whether it's potentially foldable.
4809  if (Info.checkingPotentialConstantExpression() && IsBcpCall)
4810  return false;
4811 
4812  FoldConstant Fold(Info, IsBcpCall);
4813  if (!HandleConditionalOperator(E)) {
4814  Fold.keepDiagnostics();
4815  return false;
4816  }
4817 
4818  return true;
4819  }
4820 
4821  bool VisitOpaqueValueExpr(const OpaqueValueExpr *E) {
4822  if (APValue *Value = Info.CurrentCall->getCurrentTemporary(E))
4823  return DerivedSuccess(*Value, E);
4824 
4825  const Expr *Source = E->getSourceExpr();
4826  if (!Source)
4827  return Error(E);
4828  if (Source == E) { // sanity checking.
4829  assert(0 && "OpaqueValueExpr recursively refers to itself");
4830  return Error(E);
4831  }
4832  return StmtVisitorTy::Visit(Source);
4833  }
4834 
4835  bool VisitCallExpr(const CallExpr *E) {
4836  APValue Result;
4837  if (!handleCallExpr(E, Result, nullptr))
4838  return false;
4839  return DerivedSuccess(Result, E);
4840  }
4841 
4842  bool handleCallExpr(const CallExpr *E, APValue &Result,
4843  const LValue *ResultSlot) {
4844  const Expr *Callee = E->getCallee()->IgnoreParens();
4845  QualType CalleeType = Callee->getType();
4846 
4847  const FunctionDecl *FD = nullptr;
4848  LValue *This = nullptr, ThisVal;
4849  auto Args = llvm::makeArrayRef(E->getArgs(), E->getNumArgs());
4850  bool HasQualifier = false;
4851 
4852  // Extract function decl and 'this' pointer from the callee.
4853  if (CalleeType->isSpecificBuiltinType(BuiltinType::BoundMember)) {
4854  const ValueDecl *Member = nullptr;
4855  if (const MemberExpr *ME = dyn_cast<MemberExpr>(Callee)) {
4856  // Explicit bound member calls, such as x.f() or p->g();
4857  if (!EvaluateObjectArgument(Info, ME->getBase(), ThisVal))
4858  return false;
4859  Member = ME->getMemberDecl();
4860  This = &ThisVal;
4861  HasQualifier = ME->hasQualifier();
4862  } else if (const BinaryOperator *BE = dyn_cast<BinaryOperator>(Callee)) {
4863  // Indirect bound member calls ('.*' or '->*').
4864  Member = HandleMemberPointerAccess(Info, BE, ThisVal, false);
4865  if (!Member) return false;
4866  This = &ThisVal;
4867  } else
4868  return Error(Callee);
4869 
4870  FD = dyn_cast<FunctionDecl>(Member);
4871  if (!FD)
4872  return Error(Callee);
4873  } else if (CalleeType->isFunctionPointerType()) {
4874  LValue Call;
4875  if (!EvaluatePointer(Callee, Call, Info))
4876  return false;
4877 
4878  if (!Call.getLValueOffset().isZero())
4879  return Error(Callee);
4880  FD = dyn_cast_or_null<FunctionDecl>(
4881  Call.getLValueBase().dyn_cast<const ValueDecl*>());
4882  if (!FD)
4883  return Error(Callee);
4884  // Don't call function pointers which have been cast to some other type.
4885  // Per DR (no number yet), the caller and callee can differ in noexcept.
4886  if (!Info.Ctx.hasSameFunctionTypeIgnoringExceptionSpec(
4887  CalleeType->getPointeeType(), FD->getType())) {
4888  return Error(E);
4889  }
4890 
4891  // Overloaded operator calls to member functions are represented as normal
4892  // calls with '*this' as the first argument.
4893  const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD);
4894  if (MD && !MD->isStatic()) {
4895  // FIXME: When selecting an implicit conversion for an overloaded
4896  // operator delete, we sometimes try to evaluate calls to conversion
4897  // operators without a 'this' parameter!
4898  if (Args.empty())
4899  return Error(E);
4900 
4901  if (!EvaluateObjectArgument(Info, Args[0], ThisVal))
4902  return false;
4903  This = &ThisVal;
4904  Args = Args.slice(1);
4905  } else if (MD && MD->isLambdaStaticInvoker()) {
4906  // Map the static invoker for the lambda back to the call operator.
4907  // Conveniently, we don't have to slice out the 'this' argument (as is
4908  // being done for the non-static case), since a static member function
4909  // doesn't have an implicit argument passed in.
4910  const CXXRecordDecl *ClosureClass = MD->getParent();
4911  assert(
4912  ClosureClass->captures_begin() == ClosureClass->captures_end() &&
4913  "Number of captures must be zero for conversion to function-ptr");
4914 
4915  const CXXMethodDecl *LambdaCallOp =
4916  ClosureClass->getLambdaCallOperator();
4917 
4918  // Set 'FD', the function that will be called below, to the call
4919  // operator. If the closure object represents a generic lambda, find
4920  // the corresponding specialization of the call operator.
4921 
4922  if (ClosureClass->isGenericLambda()) {
4923  assert(MD->isFunctionTemplateSpecialization() &&
4924  "A generic lambda's static-invoker function must be a "
4925  "template specialization");
4927  FunctionTemplateDecl *CallOpTemplate =
4928  LambdaCallOp->getDescribedFunctionTemplate();
4929  void *InsertPos = nullptr;
4930  FunctionDecl *CorrespondingCallOpSpecialization =
4931  CallOpTemplate->findSpecialization(TAL->asArray(), InsertPos);
4932  assert(CorrespondingCallOpSpecialization &&
4933  "We must always have a function call operator specialization "
4934  "that corresponds to our static invoker specialization");
4935  FD = cast<CXXMethodDecl>(CorrespondingCallOpSpecialization);
4936  } else
4937  FD = LambdaCallOp;
4938  }
4939 
4940 
4941  } else
4942  return Error(E);
4943 
4944  if (This && !This->checkSubobject(Info, E, CSK_This))
4945  return false;
4946 
4947  // DR1358 allows virtual constexpr functions in some cases. Don't allow
4948  // calls to such functions in constant expressions.
4949  if (This && !HasQualifier &&
4950  isa<CXXMethodDecl>(FD) && cast<CXXMethodDecl>(FD)->isVirtual())
4951  return Error(E, diag::note_constexpr_virtual_call);
4952 
4953  const FunctionDecl *Definition = nullptr;
4954  Stmt *Body = FD->getBody(Definition);
4955 
4956  if (!CheckConstexprFunction(Info, E->getExprLoc(), FD, Definition, Body) ||
4957  !HandleFunctionCall(E->getExprLoc(), Definition, This, Args, Body, Info,
4958  Result, ResultSlot))
4959  return false;
4960 
4961  return true;
4962  }
4963 
4964  bool VisitCompoundLiteralExpr(const CompoundLiteralExpr *E) {
4965  return StmtVisitorTy::Visit(E->getInitializer());
4966  }
4967  bool VisitInitListExpr(const InitListExpr *E) {
4968  if (E->getNumInits() == 0)
4969  return DerivedZeroInitialization(E);
4970  if (E->getNumInits() == 1)
4971  return StmtVisitorTy::Visit(E->getInit(0));
4972  return Error(E);
4973  }
4974  bool VisitImplicitValueInitExpr(const ImplicitValueInitExpr *E) {
4975  return DerivedZeroInitialization(E);
4976  }
4977  bool VisitCXXScalarValueInitExpr(const CXXScalarValueInitExpr *E) {
4978  return DerivedZeroInitialization(E);
4979  }
4980  bool VisitCXXNullPtrLiteralExpr(const CXXNullPtrLiteralExpr *E) {
4981  return DerivedZeroInitialization(E);
4982  }
4983 
4984  /// A member expression where the object is a prvalue is itself a prvalue.
4985  bool VisitMemberExpr(const MemberExpr *E) {
4986  assert(!E->isArrow() && "missing call to bound member function?");
4987 
4988  APValue Val;
4989  if (!Evaluate(Val, Info, E->getBase()))
4990  return false;
4991 
4992  QualType BaseTy = E->getBase()->getType();
4993 
4994  const FieldDecl *FD = dyn_cast<FieldDecl>(E->getMemberDecl());
4995  if (!FD) return Error(E);
4996  assert(!FD->getType()->isReferenceType() && "prvalue reference?");
4997  assert(BaseTy->castAs<RecordType>()->getDecl()->getCanonicalDecl() ==
4998  FD->getParent()->getCanonicalDecl() && "record / field mismatch");
4999 
5000  CompleteObject Obj(&Val, BaseTy, true);
5001  SubobjectDesignator Designator(BaseTy);
5002  Designator.addDeclUnchecked(FD);
5003 
5004  APValue Result;
5005  return extractSubobject(Info, E, Obj, Designator, Result) &&
5006  DerivedSuccess(Result, E);
5007  }
5008 
5009  bool VisitCastExpr(const CastExpr *E) {
5010  switch (E->getCastKind()) {
5011  default:
5012  break;
5013 
5014  case CK_AtomicToNonAtomic: {
5015  APValue AtomicVal;
5016  // This does not need to be done in place even for class/array types:
5017  // atomic-to-non-atomic conversion implies copying the object
5018  // representation.
5019  if (!Evaluate(AtomicVal, Info, E->getSubExpr()))
5020  return false;
5021  return DerivedSuccess(AtomicVal, E);
5022  }
5023 
5024  case CK_NoOp:
5025  case CK_UserDefinedConversion:
5026  return StmtVisitorTy::Visit(E->getSubExpr());
5027 
5028  case CK_LValueToRValue: {
5029  LValue LVal;
5030  if (!EvaluateLValue(E->getSubExpr(), LVal, Info))
5031  return false;
5032  APValue RVal;
5033  // Note, we use the subexpression's type in order to retain cv-qualifiers.
5034  if (!handleLValueToRValueConversion(Info, E, E->getSubExpr()->getType(),
5035  LVal, RVal))
5036  return false;
5037  return DerivedSuccess(RVal, E);
5038  }
5039  }
5040 
5041  return Error(E);
5042  }
5043 
5044  bool VisitUnaryPostInc(const UnaryOperator *UO) {
5045  return VisitUnaryPostIncDec(UO);
5046  }
5047  bool VisitUnaryPostDec(const UnaryOperator *UO) {
5048  return VisitUnaryPostIncDec(UO);
5049  }
5050  bool VisitUnaryPostIncDec(const UnaryOperator *UO) {
5051  if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
5052  return Error(UO);
5053 
5054  LValue LVal;
5055  if (!EvaluateLValue(UO->getSubExpr(), LVal, Info))
5056  return false;
5057  APValue RVal;
5058  if (!handleIncDec(this->Info, UO, LVal, UO->getSubExpr()->getType(),
5059  UO->isIncrementOp(), &RVal))
5060  return false;
5061  return DerivedSuccess(RVal, UO);
5062  }
5063 
5064  bool VisitStmtExpr(const StmtExpr *E) {
5065  // We will have checked the full-expressions inside the statement expression
5066  // when they were completed, and don't need to check them again now.
5067  if (Info.checkingForOverflow())
5068  return Error(E);
5069 
5070  BlockScopeRAII Scope(Info);
5071  const CompoundStmt *CS = E->getSubStmt();
5072  if (CS->body_empty())
5073  return true;
5074 
5076  BE = CS->body_end();
5077  /**/; ++BI) {
5078  if (BI + 1 == BE) {
5079  const Expr *FinalExpr = dyn_cast<Expr>(*BI);
5080  if (!FinalExpr) {
5081  Info.FFDiag((*BI)->getBeginLoc(),
5082  diag::note_constexpr_stmt_expr_unsupported);
5083  return false;
5084  }
5085  return this->Visit(FinalExpr);
5086  }
5087 
5088  APValue ReturnValue;
5089  StmtResult Result = { ReturnValue, nullptr };
5090  EvalStmtResult ESR = EvaluateStmt(Result, Info, *BI);
5091  if (ESR != ESR_Succeeded) {
5092  // FIXME: If the statement-expression terminated due to 'return',
5093  // 'break', or 'continue', it would be nice to propagate that to
5094  // the outer statement evaluation rather than bailing out.
5095  if (ESR != ESR_Failed)
5096  Info.FFDiag((*BI)->getBeginLoc(),
5097  diag::note_constexpr_stmt_expr_unsupported);
5098  return false;
5099  }
5100  }
5101 
5102  llvm_unreachable("Return from function from the loop above.");
5103  }
5104 
5105  /// Visit a value which is evaluated, but whose value is ignored.
5106  void VisitIgnoredValue(const Expr *E) {
5107  EvaluateIgnoredValue(Info, E);
5108  }
5109 
5110  /// Potentially visit a MemberExpr's base expression.
5111  void VisitIgnoredBaseExpression(const Expr *E) {
5112  // While MSVC doesn't evaluate the base expression, it does diagnose the
5113  // presence of side-effecting behavior.
5114  if (Info.getLangOpts().MSVCCompat && !E->HasSideEffects(Info.Ctx))
5115  return;
5116  VisitIgnoredValue(E);
5117  }
5118 };
5119 
5120 } // namespace
5121 
5122 //===----------------------------------------------------------------------===//
5123 // Common base class for lvalue and temporary evaluation.
5124 //===----------------------------------------------------------------------===//
5125 namespace {
5126 template<class Derived>
5127 class LValueExprEvaluatorBase
5128  : public ExprEvaluatorBase<Derived> {
5129 protected:
5130  LValue &Result;
5131  bool InvalidBaseOK;
5132  typedef LValueExprEvaluatorBase LValueExprEvaluatorBaseTy;
5133  typedef ExprEvaluatorBase<Derived> ExprEvaluatorBaseTy;
5134 
5135  bool Success(APValue::LValueBase B) {
5136  Result.set(B);
5137  return true;
5138  }
5139 
5140  bool evaluatePointer(const Expr *E, LValue &Result) {
5141  return EvaluatePointer(E, Result, this->Info, InvalidBaseOK);
5142  }
5143 
5144 public:
5145  LValueExprEvaluatorBase(EvalInfo &Info, LValue &Result, bool InvalidBaseOK)
5146  : ExprEvaluatorBaseTy(Info), Result(Result),
5147  InvalidBaseOK(InvalidBaseOK) {}
5148 
5149  bool Success(const APValue &V, const Expr *E) {
5150  Result.setFrom(this->Info.Ctx, V);
5151  return true;
5152  }
5153 
5154  bool VisitMemberExpr(const MemberExpr *E) {
5155  // Handle non-static data members.
5156  QualType BaseTy;
5157  bool EvalOK;
5158  if (E->isArrow()) {
5159  EvalOK = evaluatePointer(E->getBase(), Result);
5160  BaseTy = E->getBase()->getType()->castAs<PointerType>()->getPointeeType();
5161  } else if (E->getBase()->isRValue()) {
5162  assert(E->getBase()->getType()->isRecordType());
5163  EvalOK = EvaluateTemporary(E->getBase(), Result, this->Info);
5164  BaseTy = E->getBase()->getType();
5165  } else {
5166  EvalOK = this->Visit(E->getBase());
5167  BaseTy = E->getBase()->getType();
5168  }
5169  if (!EvalOK) {
5170  if (!InvalidBaseOK)
5171  return false;
5172  Result.setInvalid(E);
5173  return true;
5174  }
5175 
5176  const ValueDecl *MD = E->getMemberDecl();
5177  if (const FieldDecl *FD = dyn_cast<FieldDecl>(E->getMemberDecl())) {
5178  assert(BaseTy->getAs<RecordType>()->getDecl()->getCanonicalDecl() ==
5179  FD->getParent()->getCanonicalDecl() && "record / field mismatch");
5180  (void)BaseTy;
5181  if (!HandleLValueMember(this->Info, E, Result, FD))
5182  return false;
5183  } else if (const IndirectFieldDecl *IFD = dyn_cast<IndirectFieldDecl>(MD)) {
5184  if (!HandleLValueIndirectMember(this->Info, E, Result, IFD))
5185  return false;
5186  } else
5187  return this->Error(E);
5188 
5189  if (MD->getType()->isReferenceType()) {
5190  APValue RefValue;
5191  if (!handleLValueToRValueConversion(this->Info, E, MD->getType(), Result,
5192  RefValue))
5193  return false;
5194  return Success(RefValue, E);
5195  }
5196  return true;
5197  }
5198 
5199  bool VisitBinaryOperator(const BinaryOperator *E) {
5200  switch (E->getOpcode()) {
5201  default:
5202  return ExprEvaluatorBaseTy::VisitBinaryOperator(E);
5203 
5204  case BO_PtrMemD:
5205  case BO_PtrMemI:
5206  return HandleMemberPointerAccess(this->Info, E, Result);
5207  }
5208  }
5209 
5210  bool VisitCastExpr(const CastExpr *E) {
5211  switch (E->getCastKind()) {
5212  default:
5213  return ExprEvaluatorBaseTy::VisitCastExpr(E);
5214 
5215  case CK_DerivedToBase:
5216  case CK_UncheckedDerivedToBase:
5217  if (!this->Visit(E->getSubExpr()))
5218  return false;
5219 
5220  // Now figure out the necessary offset to add to the base LV to get from
5221  // the derived class to the base class.
5222  return HandleLValueBasePath(this->Info, E, E->getSubExpr()->getType(),
5223  Result);
5224  }
5225  }
5226 };
5227 }
5228 
5229 //===----------------------------------------------------------------------===//
5230 // LValue Evaluation
5231 //
5232 // This is used for evaluating lvalues (in C and C++), xvalues (in C++11),
5233 // function designators (in C), decl references to void objects (in C), and
5234 // temporaries (if building with -Wno-address-of-temporary).
5235 //
5236 // LValue evaluation produces values comprising a base expression of one of the
5237 // following types:
5238 // - Declarations
5239 // * VarDecl
5240 // * FunctionDecl
5241 // - Literals
5242 // * CompoundLiteralExpr in C (and in global scope in C++)
5243 // * StringLiteral
5244 // * CXXTypeidExpr
5245 // * PredefinedExpr
5246 // * ObjCStringLiteralExpr
5247 // * ObjCEncodeExpr
5248 // * AddrLabelExpr
5249 // * BlockExpr
5250 // * CallExpr for a MakeStringConstant builtin
5251 // - Locals and temporaries
5252 // * MaterializeTemporaryExpr
5253 // * Any Expr, with a CallIndex indicating the function in which the temporary
5254 // was evaluated, for cases where the MaterializeTemporaryExpr is missing
5255 // from the AST (FIXME).
5256 // * A MaterializeTemporaryExpr that has static storage duration, with no
5257 // CallIndex, for a lifetime-extended temporary.
5258 // plus an offset in bytes.
5259 //===----------------------------------------------------------------------===//
5260 namespace {
5261 class LValueExprEvaluator
5262  : public LValueExprEvaluatorBase<LValueExprEvaluator> {
5263 public:
5264  LValueExprEvaluator(EvalInfo &Info, LValue &Result, bool InvalidBaseOK) :
5265  LValueExprEvaluatorBaseTy(Info, Result, InvalidBaseOK) {}
5266 
5267  bool VisitVarDecl(const Expr *E, const VarDecl *VD);
5268  bool VisitUnaryPreIncDec(const UnaryOperator *UO);
5269 
5270  bool VisitDeclRefExpr(const DeclRefExpr *E);
5271  bool VisitPredefinedExpr(const PredefinedExpr *E) { return Success(E); }
5272  bool VisitMaterializeTemporaryExpr(const MaterializeTemporaryExpr *E);
5273  bool VisitCompoundLiteralExpr(const CompoundLiteralExpr *E);
5274  bool VisitMemberExpr(const MemberExpr *E);
5275  bool VisitStringLiteral(const StringLiteral *E) { return Success(E); }
5276  bool VisitObjCEncodeExpr(const ObjCEncodeExpr *E) { return Success(E); }
5277  bool VisitCXXTypeidExpr(const CXXTypeidExpr *E);
5278  bool VisitCXXUuidofExpr(const CXXUuidofExpr *E);
5279  bool VisitArraySubscriptExpr(const ArraySubscriptExpr *E);
5280  bool VisitUnaryDeref(const UnaryOperator *E);
5281  bool VisitUnaryReal(const UnaryOperator *E);
5282  bool VisitUnaryImag(const UnaryOperator *E);
5283  bool VisitUnaryPreInc(const UnaryOperator *UO) {
5284  return VisitUnaryPreIncDec(UO);
5285  }
5286  bool VisitUnaryPreDec(const UnaryOperator *UO) {
5287  return VisitUnaryPreIncDec(UO);
5288  }
5289  bool VisitBinAssign(const BinaryOperator *BO);
5290  bool VisitCompoundAssignOperator(const CompoundAssignOperator *CAO);
5291 
5292  bool VisitCastExpr(const CastExpr *E) {
5293  switch (E->getCastKind()) {
5294  default:
5295  return LValueExprEvaluatorBaseTy::VisitCastExpr(E);
5296 
5297  case CK_LValueBitCast:
5298  this->CCEDiag(E, diag::note_constexpr_invalid_cast) << 2;
5299  if (!Visit(E->getSubExpr()))
5300  return false;
5301  Result.Designator.setInvalid();
5302  return true;
5303 
5304  case CK_BaseToDerived:
5305  if (!Visit(E->getSubExpr()))
5306  return false;
5307  return HandleBaseToDerivedCast(Info, E, Result);
5308  }
5309  }
5310 };
5311 } // end anonymous namespace
5312 
5313 /// Evaluate an expression as an lvalue. This can be legitimately called on
5314 /// expressions which are not glvalues, in three cases:
5315 /// * function designators in C, and
5316 /// * "extern void" objects
5317 /// * @selector() expressions in Objective-C
5318 static bool EvaluateLValue(const Expr *E, LValue &Result, EvalInfo &Info,
5319  bool InvalidBaseOK) {
5320  assert(E->isGLValue() || E->getType()->isFunctionType() ||
5321  E->getType()->isVoidType() || isa<ObjCSelectorExpr>(E));
5322  return LValueExprEvaluator(Info, Result, InvalidBaseOK).Visit(E);
5323 }
5324 
5325 bool LValueExprEvaluator::VisitDeclRefExpr(const DeclRefExpr *E) {
5326  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(E->getDecl()))
5327  return Success(FD);
5328  if (const VarDecl *VD = dyn_cast<VarDecl>(E->getDecl()))
5329  return VisitVarDecl(E, VD);
5330  if (const BindingDecl *BD = dyn_cast<BindingDecl>(E->getDecl()))
5331  return Visit(BD->getBinding());
5332  return Error(E);
5333 }
5334 
5335 
5336 bool LValueExprEvaluator::VisitVarDecl(const Expr *E, const VarDecl *VD) {
5337 
5338  // If we are within a lambda's call operator, check whether the 'VD' referred
5339  // to within 'E' actually represents a lambda-capture that maps to a
5340  // data-member/field within the closure object, and if so, evaluate to the
5341  // field or what the field refers to.
5342  if (Info.CurrentCall && isLambdaCallOperator(Info.CurrentCall->Callee) &&
5343  isa<DeclRefExpr>(E) &&
5344  cast<DeclRefExpr>(E)->refersToEnclosingVariableOrCapture()) {
5345  // We don't always have a complete capture-map when checking or inferring if
5346  // the function call operator meets the requirements of a constexpr function
5347  // - but we don't need to evaluate the captures to determine constexprness
5348  // (dcl.constexpr C++17).
5349  if (Info.checkingPotentialConstantExpression())
5350  return false;
5351 
5352  if (auto *FD = Info.CurrentCall->LambdaCaptureFields.lookup(VD)) {
5353  // Start with 'Result' referring to the complete closure object...
5354  Result = *Info.CurrentCall->This;
5355  // ... then update it to refer to the field of the closure object
5356  // that represents the capture.
5357  if (!HandleLValueMember(Info, E, Result, FD))
5358  return false;
5359  // And if the field is of reference type, update 'Result' to refer to what
5360  // the field refers to.
5361  if (FD->getType()->isReferenceType()) {
5362  APValue RVal;
5363  if (!handleLValueToRValueConversion(Info, E, FD->getType(), Result,
5364  RVal))
5365  return false;
5366  Result.setFrom(Info.Ctx, RVal);
5367  }
5368  return true;
5369  }
5370  }
5371  CallStackFrame *Frame = nullptr;
5372  if (VD->hasLocalStorage() && Info.CurrentCall->Index > 1) {
5373  // Only if a local variable was declared in the function currently being
5374  // evaluated, do we expect to be able to find its value in the current
5375  // frame. (Otherwise it was likely declared in an enclosing context and
5376  // could either have a valid evaluatable value (for e.g. a constexpr
5377  // variable) or be ill-formed (and trigger an appropriate evaluation
5378  // diagnostic)).
5379  if (Info.CurrentCall->Callee &&
5380  Info.CurrentCall->Callee->Equals(VD->getDeclContext())) {
5381  Frame = Info.CurrentCall;
5382  }
5383  }
5384 
5385  if (!VD->getType()->isReferenceType()) {
5386  if (Frame) {
5387  Result.set({VD, Frame->Index,
5388  Info.CurrentCall->getCurrentTemporaryVersion(VD)});
5389  return true;
5390  }
5391  return Success(VD);
5392  }
5393 
5394  APValue *V;
5395  if (!evaluateVarDeclInit(Info, E, VD, Frame, V, nullptr))
5396  return false;
5397  if (V->isUninit()) {
5398  if (!Info.checkingPotentialConstantExpression())
5399  Info.FFDiag(E, diag::note_constexpr_use_uninit_reference);
5400  return false;
5401  }
5402  return Success(*V, E);
5403 }
5404 
5405 bool LValueExprEvaluator::VisitMaterializeTemporaryExpr(
5406  const MaterializeTemporaryExpr *E) {
5407  // Walk through the expression to find the materialized temporary itself.
5408  SmallVector<const Expr *, 2> CommaLHSs;
5410  const Expr *Inner = E->GetTemporaryExpr()->
5411  skipRValueSubobjectAdjustments(CommaLHSs, Adjustments);
5412 
5413  // If we passed any comma operators, evaluate their LHSs.
5414  for (unsigned I = 0, N = CommaLHSs.size(); I != N; ++I)
5415  if (!EvaluateIgnoredValue(Info, CommaLHSs[I]))
5416  return false;
5417 
5418  // A materialized temporary with static storage duration can appear within the
5419  // result of a constant expression evaluation, so we need to preserve its
5420  // value for use outside this evaluation.
5421  APValue *Value;
5422  if (E->getStorageDuration() == SD_Static) {
5423  Value = Info.Ctx.getMaterializedTemporaryValue(E, true);
5424  *Value = APValue();
5425  Result.set(E);
5426  } else {
5428  *Info.CurrentCall);
5429  }
5430 
5431  QualType Type = Inner->getType();
5432 
5433  // Materialize the temporary itself.
5434  if (!EvaluateInPlace(*Value, Info, Result, Inner) ||
5435  (E->getStorageDuration() == SD_Static &&
5436  !CheckConstantExpression(Info, E->getExprLoc(), Type, *Value))) {
5437  *Value = APValue();
5438  return false;
5439  }
5440 
5441  // Adjust our lvalue to refer to the desired subobject.
5442  for (unsigned I = Adjustments.size(); I != 0; /**/) {
5443  --I;
5444  switch (Adjustments[I].Kind) {
5446  if (!HandleLValueBasePath(Info, Adjustments[I].DerivedToBase.BasePath,
5447  Type, Result))
5448  return false;
5449  Type = Adjustments[I].DerivedToBase.BasePath->getType();
5450  break;
5451 
5453  if (!HandleLValueMember(Info, E, Result, Adjustments[I].Field))
5454  return false;
5455  Type = Adjustments[I].Field->getType();
5456  break;
5457 
5459  if (!HandleMemberPointerAccess(this->Info, Type, Result,
5460  Adjustments[I].Ptr.RHS))
5461  return false;
5462  Type = Adjustments[I].Ptr.MPT->getPointeeType();
5463  break;
5464  }
5465  }
5466 
5467  return true;
5468 }
5469 
5470 bool
5471 LValueExprEvaluator::VisitCompoundLiteralExpr(const CompoundLiteralExpr *E) {
5472  assert((!Info.getLangOpts().CPlusPlus || E->isFileScope()) &&
5473  "lvalue compound literal in c++?");
5474  // Defer visiting the literal until the lvalue-to-rvalue conversion. We can
5475  // only see this when folding in C, so there's no standard to follow here.
5476  return Success(E);
5477 }
5478 
5479 bool LValueExprEvaluator::VisitCXXTypeidExpr(const CXXTypeidExpr *E) {
5480  if (!E->isPotentiallyEvaluated())
5481  return Success(E);
5482 
5483  Info.FFDiag(E, diag::note_constexpr_typeid_polymorphic)
5484  << E->getExprOperand()->getType()
5485  << E->getExprOperand()->getSourceRange();
5486  return false;
5487 }
5488 
5489 bool LValueExprEvaluator::VisitCXXUuidofExpr(const CXXUuidofExpr *E) {
5490  return Success(E);
5491 }
5492 
5493 bool LValueExprEvaluator::VisitMemberExpr(const MemberExpr *E) {
5494  // Handle static data members.
5495  if (const VarDecl *VD = dyn_cast<VarDecl>(E->getMemberDecl())) {
5496  VisitIgnoredBaseExpression(E->getBase());
5497  return VisitVarDecl(E, VD);
5498  }
5499 
5500  // Handle static member functions.
5501  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(E->getMemberDecl())) {
5502  if (MD->isStatic()) {
5503  VisitIgnoredBaseExpression(E->getBase());
5504  return Success(MD);
5505  }
5506  }
5507 
5508  // Handle non-static data members.
5509  return LValueExprEvaluatorBaseTy::VisitMemberExpr(E);
5510 }
5511 
5512 bool LValueExprEvaluator::VisitArraySubscriptExpr(const ArraySubscriptExpr *E) {
5513  // FIXME: Deal with vectors as array subscript bases.
5514  if (E->getBase()->getType()->isVectorType())
5515  return Error(E);
5516 
5517  bool Success = true;
5518  if (!evaluatePointer(E->getBase(), Result)) {
5519  if (!Info.noteFailure())
5520  return false;
5521  Success = false;
5522  }
5523 
5524  APSInt Index;
5525  if (!EvaluateInteger(E->getIdx(), Index, Info))
5526  return false;
5527 
5528  return Success &&
5529  HandleLValueArrayAdjustment(Info, E, Result, E->getType(), Index);
5530 }
5531 
5532 bool LValueExprEvaluator::VisitUnaryDeref(const UnaryOperator *E) {
5533  return evaluatePointer(E->getSubExpr(), Result);
5534 }
5535 
5536 bool LValueExprEvaluator::VisitUnaryReal(const UnaryOperator *E) {
5537  if (!Visit(E->getSubExpr()))
5538  return false;
5539  // __real is a no-op on scalar lvalues.
5540  if (E->getSubExpr()->getType()->isAnyComplexType())
5541  HandleLValueComplexElement(Info, E, Result, E->getType(), false);
5542  return true;
5543 }
5544 
5545 bool LValueExprEvaluator::VisitUnaryImag(const UnaryOperator *E) {
5546  assert(E->getSubExpr()->getType()->isAnyComplexType() &&
5547  "lvalue __imag__ on scalar?");
5548  if (!Visit(E->getSubExpr()))
5549  return false;
5550  HandleLValueComplexElement(Info, E, Result, E->getType(), true);
5551  return true;
5552 }
5553 
5554 bool LValueExprEvaluator::VisitUnaryPreIncDec(const UnaryOperator *UO) {
5555  if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
5556  return Error(UO);
5557 
5558  if (!this->Visit(UO->getSubExpr()))
5559  return false;
5560 
5561  return handleIncDec(
5562  this->Info, UO, Result, UO->getSubExpr()->getType(),
5563  UO->isIncrementOp(), nullptr);
5564 }
5565 
5566 bool LValueExprEvaluator::VisitCompoundAssignOperator(
5567  const CompoundAssignOperator *CAO) {
5568  if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
5569  return Error(CAO);
5570 
5571  APValue RHS;
5572 
5573  // The overall lvalue result is the result of evaluating the LHS.
5574  if (!this->Visit(CAO->getLHS())) {
5575  if (Info.noteFailure())
5576  Evaluate(RHS, this->Info, CAO->getRHS());
5577  return false;
5578  }
5579 
5580  if (!Evaluate(RHS, this->Info, CAO->getRHS()))
5581  return false;
5582 
5583  return handleCompoundAssignment(
5584  this->Info, CAO,
5585  Result, CAO->getLHS()->getType(), CAO->getComputationLHSType(),
5586  CAO->getOpForCompoundAssignment(CAO->getOpcode()), RHS);
5587 }
5588 
5589 bool LValueExprEvaluator::VisitBinAssign(const BinaryOperator *E) {
5590  if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
5591  return Error(E);
5592 
5593  APValue NewVal;
5594 
5595  if (!this->Visit(E->getLHS())) {
5596  if (Info.noteFailure())
5597  Evaluate(NewVal, this->Info, E->getRHS());
5598  return false;
5599  }
5600 
5601  if (!Evaluate(NewVal, this->Info, E->getRHS()))
5602  return false;
5603 
5604  return handleAssignment(this->Info, E, Result, E->getLHS()->getType(),
5605  NewVal);
5606 }
5607 
5608 //===----------------------------------------------------------------------===//
5609 // Pointer Evaluation
5610 //===----------------------------------------------------------------------===//
5611 
5612 /// Attempts to compute the number of bytes available at the pointer
5613 /// returned by a function with the alloc_size attribute. Returns true if we
5614 /// were successful. Places an unsigned number into `Result`.
5615 ///
5616 /// This expects the given CallExpr to be a call to a function with an
5617 /// alloc_size attribute.
5619  const CallExpr *Call,
5620  llvm::APInt &Result) {
5621  const AllocSizeAttr *AllocSize = getAllocSizeAttr(Call);
5622 
5623  assert(AllocSize && AllocSize->getElemSizeParam().isValid());
5624  unsigned SizeArgNo = AllocSize->getElemSizeParam().getASTIndex();
5625  unsigned BitsInSizeT = Ctx.getTypeSize(Ctx.getSizeType());
5626  if (Call->getNumArgs() <= SizeArgNo)
5627  return false;
5628 
5629  auto EvaluateAsSizeT = [&](const Expr *E, APSInt &Into) {
5630  if (!E->EvaluateAsInt(Into, Ctx, Expr::SE_AllowSideEffects))
5631  return false;
5632  if (Into.isNegative() || !Into.isIntN(BitsInSizeT))
5633  return false;
5634  Into = Into.zextOrSelf(BitsInSizeT);
5635  return true;
5636  };
5637 
5638  APSInt SizeOfElem;
5639  if (!EvaluateAsSizeT(Call->getArg(SizeArgNo), SizeOfElem))
5640  return false;
5641 
5642  if (!AllocSize->getNumElemsParam().isValid()) {
5643  Result = std::move(SizeOfElem);
5644  return true;
5645  }
5646 
5647  APSInt NumberOfElems;
5648  unsigned NumArgNo = AllocSize->getNumElemsParam().getASTIndex();
5649  if (!EvaluateAsSizeT(Call->getArg(NumArgNo), NumberOfElems))
5650  return false;
5651 
5652  bool Overflow;
5653  llvm::APInt BytesAvailable = SizeOfElem.umul_ov(NumberOfElems, Overflow);
5654  if (Overflow)
5655  return false;
5656 
5657  Result = std::move(BytesAvailable);
5658  return true;
5659 }
5660 
5661 /// Convenience function. LVal's base must be a call to an alloc_size
5662 /// function.
5664  const LValue &LVal,
5665  llvm::APInt &Result) {
5666  assert(isBaseAnAllocSizeCall(LVal.getLValueBase()) &&
5667  "Can't get the size of a non alloc_size function");
5668  const auto *Base = LVal.getLValueBase().get<const Expr *>();
5669  const CallExpr *CE = tryUnwrapAllocSizeCall(Base);
5670  return getBytesReturnedByAllocSizeCall(Ctx, CE, Result);
5671 }
5672 
5673 /// Attempts to evaluate the given LValueBase as the result of a call to
5674 /// a function with the alloc_size attribute. If it was possible to do so, this
5675 /// function will return true, make Result's Base point to said function call,
5676 /// and mark Result's Base as invalid.
5677 static bool evaluateLValueAsAllocSize(EvalInfo &Info, APValue::LValueBase Base,
5678  LValue &Result) {
5679  if (Base.isNull())
5680  return false;
5681 
5682  // Because we do no form of static analysis, we only support const variables.
5683  //
5684  // Additionally, we can't support parameters, nor can we support static
5685  // variables (in the latter case, use-before-assign isn't UB; in the former,
5686  // we have no clue what they'll be assigned to).
5687  const auto *VD =
5688  dyn_cast_or_null<VarDecl>(Base.dyn_cast<const ValueDecl *>());
5689  if (!VD || !VD->isLocalVarDecl() || !VD->getType().isConstQualified())
5690  return false;
5691 
5692  const Expr *Init = VD->getAnyInitializer();
5693  if (!Init)
5694  return false;
5695 
5696  const Expr *E = Init->IgnoreParens();
5697  if (!tryUnwrapAllocSizeCall(E))
5698  return false;
5699 
5700  // Store E instead of E unwrapped so that the type of the LValue's base is
5701  // what the user wanted.
5702  Result.setInvalid(E);
5703 
5704  QualType Pointee = E->getType()->castAs<PointerType>()->getPointeeType();
5705  Result.addUnsizedArray(Info, E, Pointee);
5706  return true;
5707 }
5708 
5709 namespace {
5710 class PointerExprEvaluator
5711  : public ExprEvaluatorBase<PointerExprEvaluator> {
5712  LValue &Result;
5713  bool InvalidBaseOK;
5714 
5715  bool Success(const Expr *E) {
5716  Result.set(E);
5717  return true;
5718  }
5719 
5720  bool evaluateLValue(const Expr *E, LValue &Result) {
5721  return EvaluateLValue(E, Result, Info, InvalidBaseOK);
5722  }
5723 
5724  bool evaluatePointer(const Expr *E, LValue &Result) {
5725  return EvaluatePointer(E, Result, Info, InvalidBaseOK);
5726  }
5727 
5728  bool visitNonBuiltinCallExpr(const CallExpr *E);
5729 public:
5730 
5731  PointerExprEvaluator(EvalInfo &info, LValue &Result, bool InvalidBaseOK)
5732  : ExprEvaluatorBaseTy(info), Result(Result),
5733  InvalidBaseOK(InvalidBaseOK) {}
5734 
5735  bool Success(const APValue &V, const Expr *E) {
5736  Result.setFrom(Info.Ctx, V);
5737  return true;
5738  }
5739  bool ZeroInitialization(const Expr *E) {
5740  auto TargetVal = Info.Ctx.getTargetNullPointerValue(E->getType());
5741  Result.setNull(E->getType(), TargetVal);
5742  return true;
5743  }
5744 
5745  bool VisitBinaryOperator(const BinaryOperator *E);
5746  bool VisitCastExpr(const CastExpr* E);
5747  bool VisitUnaryAddrOf(const UnaryOperator *E);
5748  bool VisitObjCStringLiteral(const ObjCStringLiteral *E)
5749  { return Success(E); }
5750  bool VisitObjCBoxedExpr(const ObjCBoxedExpr *E) {
5751  if (Info.noteFailure())
5752  EvaluateIgnoredValue(Info, E->getSubExpr());
5753  return Error(E);
5754  }
5755  bool VisitAddrLabelExpr(const AddrLabelExpr *E)
5756  { return Success(E); }
5757  bool VisitCallExpr(const CallExpr *E);
5758  bool VisitBuiltinCallExpr(const CallExpr *E, unsigned BuiltinOp);
5759  bool VisitBlockExpr(const BlockExpr *E) {
5760  if (!E->getBlockDecl()->hasCaptures())
5761  return Success(E);
5762  return Error(E);
5763  }
5764  bool VisitCXXThisExpr(const CXXThisExpr *E) {
5765  // Can't look at 'this' when checking a potential constant expression.
5766  if (Info.checkingPotentialConstantExpression())
5767  return false;
5768  if (!Info.CurrentCall->This) {
5769  if (Info.getLangOpts().CPlusPlus11)
5770  Info.FFDiag(E, diag::note_constexpr_this) << E->isImplicit();
5771  else
5772  Info.FFDiag(E);
5773  return false;
5774  }
5775  Result = *Info.CurrentCall->This;
5776  // If we are inside a lambda's call operator, the 'this' expression refers
5777  // to the enclosing '*this' object (either by value or reference) which is
5778  // either copied into the closure object's field that represents the '*this'
5779  // or refers to '*this'.
5780  if (isLambdaCallOperator(Info.CurrentCall->Callee)) {
5781  // Update 'Result' to refer to the data member/field of the closure object
5782  // that represents the '*this' capture.
5783  if (!HandleLValueMember(Info, E, Result,
5784  Info.CurrentCall->LambdaThisCaptureField))
5785  return false;
5786  // If we captured '*this' by reference, replace the field with its referent.
5787  if (Info.CurrentCall->LambdaThisCaptureField->getType()
5788  ->isPointerType()) {
5789  APValue RVal;
5790  if (!handleLValueToRValueConversion(Info, E, E->getType(), Result,
5791  RVal))
5792  return false;
5793 
5794  Result.setFrom(Info.Ctx, RVal);
5795  }
5796  }
5797  return true;
5798  }
5799 
5800  // FIXME: Missing: @protocol, @selector
5801 };
5802 } // end anonymous namespace
5803 
5804 static bool EvaluatePointer(const Expr* E, LValue& Result, EvalInfo &Info,
5805  bool InvalidBaseOK) {
5806  assert(E->isRValue() && E->getType()->hasPointerRepresentation());
5807  return PointerExprEvaluator(Info, Result, InvalidBaseOK).Visit(E);
5808 }
5809 
5810 bool PointerExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
5811  if (E->getOpcode() != BO_Add &&
5812  E->getOpcode() != BO_Sub)
5813  return ExprEvaluatorBaseTy::VisitBinaryOperator(E);
5814 
5815  const Expr *PExp = E->getLHS();
5816  const Expr *IExp = E->getRHS();
5817  if (IExp->getType()->isPointerType())
5818  std::swap(PExp, IExp);
5819 
5820  bool EvalPtrOK = evaluatePointer(PExp, Result);
5821  if (!EvalPtrOK && !Info.noteFailure())
5822  return false;
5823 
5824  llvm::APSInt Offset;
5825  if (!EvaluateInteger(IExp, Offset, Info) || !EvalPtrOK)
5826  return false;
5827 
5828  if (E->getOpcode() == BO_Sub)
5829  negateAsSigned(Offset);
5830 
5831  QualType Pointee = PExp->getType()->castAs<PointerType>()->getPointeeType();
5832  return HandleLValueArrayAdjustment(Info, E, Result, Pointee, Offset);
5833 }
5834 
5835 bool PointerExprEvaluator::VisitUnaryAddrOf(const UnaryOperator *E) {
5836  return evaluateLValue(E->getSubExpr(), Result);
5837 }
5838 
5839 bool PointerExprEvaluator::VisitCastExpr(const CastExpr *E) {
5840  const Expr *SubExpr = E->getSubExpr();
5841 
5842  switch (E->getCastKind()) {
5843  default:
5844  break;
5845 
5846  case CK_BitCast:
5847  case CK_CPointerToObjCPointerCast:
5848  case CK_BlockPointerToObjCPointerCast:
5849  case CK_AnyPointerToBlockPointerCast:
5850  case CK_AddressSpaceConversion:
5851  if (!Visit(SubExpr))
5852  return false;
5853  // Bitcasts to cv void* are static_casts, not reinterpret_casts, so are
5854  // permitted in constant expressions in C++11. Bitcasts from cv void* are
5855  // also static_casts, but we disallow them as a resolution to DR1312.
5856  if (!E->getType()->isVoidPointerType()) {
5857  // If we changed anything other than cvr-qualifiers, we can't use this
5858  // value for constant folding. FIXME: Qualification conversions should
5859  // always be CK_NoOp, but we get this wrong in C.
5860  if (!Info.Ctx.hasCvrSimilarType(E->getType(), E->getSubExpr()->getType()))
5861  Result.Designator.setInvalid();
5862  if (SubExpr->getType()->isVoidPointerType())
5863  CCEDiag(E, diag::note_constexpr_invalid_cast)
5864  << 3 << SubExpr->getType();
5865  else
5866  CCEDiag(E, diag::note_constexpr_invalid_cast) << 2;
5867  }
5868  if (E->getCastKind() == CK_AddressSpaceConversion && Result.IsNullPtr)
5869  ZeroInitialization(E);
5870  return true;
5871 
5872  case CK_DerivedToBase:
5873  case CK_UncheckedDerivedToBase:
5874  if (!evaluatePointer(E->getSubExpr(), Result))
5875  return false;
5876  if (!Result.Base && Result.Offset.isZero())
5877  return true;
5878 
5879  // Now figure out the necessary offset to add to the base LV to get from
5880  // the derived class to the base class.
5881  return HandleLValueBasePath(Info, E, E->getSubExpr()->getType()->
5882  castAs<PointerType>()->getPointeeType(),
5883  Result);
5884 
5885  case CK_BaseToDerived:
5886  if (!Visit(E->getSubExpr()))
5887  return false;
5888  if (!Result.Base && Result.Offset.isZero())
5889  return true;
5890  return HandleBaseToDerivedCast(Info, E, Result);
5891 
5892  case CK_NullToPointer:
5893  VisitIgnoredValue(E->getSubExpr());
5894  return ZeroInitialization(E);
5895 
5896  case CK_IntegralToPointer: {
5897  CCEDiag(E, diag::note_constexpr_invalid_cast) << 2;
5898 
5899  APValue Value;
5900  if (!EvaluateIntegerOrLValue(SubExpr, Value, Info))
5901  break;
5902 
5903  if (Value.isInt()) {
5904  unsigned Size = Info.Ctx.getTypeSize(E->getType());
5905  uint64_t N = Value.getInt().extOrTrunc(Size).getZExtValue();
5906  Result.Base = (Expr*)nullptr;
5907  Result.InvalidBase = false;
5908  Result.Offset = CharUnits::fromQuantity(N);
5909  Result.Designator.setInvalid();
5910  Result.IsNullPtr = false;
5911  return true;
5912  } else {
5913  // Cast is of an lvalue, no need to change value.
5914  Result.setFrom(Info.Ctx, Value);
5915  return true;
5916  }
5917  }
5918 
5919  case CK_ArrayToPointerDecay: {
5920  if (SubExpr->isGLValue()) {
5921  if (!evaluateLValue(SubExpr, Result))
5922  return false;
5923  } else {
5924  APValue &Value = createTemporary(SubExpr, false, Result,
5925  *Info.CurrentCall);
5926  if (!EvaluateInPlace(Value, Info, Result, SubExpr))
5927  return false;
5928  }
5929  // The result is a pointer to the first element of the array.
5930  auto *AT = Info.Ctx.getAsArrayType(SubExpr->getType());
5931  if (auto *CAT = dyn_cast<ConstantArrayType>(AT))
5932  Result.addArray(Info, E, CAT);
5933  else
5934  Result.addUnsizedArray(Info, E, AT->getElementType());
5935  return true;
5936  }
5937 
5938  case CK_FunctionToPointerDecay:
5939  return evaluateLValue(SubExpr, Result);
5940 
5941  case CK_LValueToRValue: {
5942  LValue LVal;
5943  if (!evaluateLValue(E->getSubExpr(), LVal))
5944  return false;
5945 
5946  APValue RVal;
5947  // Note, we use the subexpression's type in order to retain cv-qualifiers.
5948  if (!handleLValueToRValueConversion(Info, E, E->getSubExpr()->getType(),
5949  LVal, RVal))
5950  return InvalidBaseOK &&
5951  evaluateLValueAsAllocSize(Info, LVal.Base, Result);
5952  return Success(RVal, E);
5953  }
5954  }
5955 
5956  return ExprEvaluatorBaseTy::VisitCastExpr(E);
5957 }
5958 
5959 static CharUnits GetAlignOfType(EvalInfo &Info, QualType T) {
5960  // C++ [expr.alignof]p3:
5961  // When alignof is applied to a reference type, the result is the
5962  // alignment of the referenced type.
5963  if (const ReferenceType *Ref = T->getAs<ReferenceType>())
5964  T = Ref->getPointeeType();
5965 
5966  // __alignof is defined to return the preferred alignment.
5967  if (T.getQualifiers().hasUnaligned())
5968  return CharUnits::One();
5969  return Info.Ctx.toCharUnitsFromBits(
5970  Info.Ctx.getPreferredTypeAlign(T.getTypePtr()));
5971 }
5972 
5973 static CharUnits GetAlignOfExpr(EvalInfo &Info, const Expr *E) {
5974  E = E->IgnoreParens();
5975 
5976  // The kinds of expressions that we have special-case logic here for
5977  // should be kept up to date with the special checks for those
5978  // expressions in Sema.
5979 
5980  // alignof decl is always accepted, even if it doesn't make sense: we default
5981  // to 1 in those cases.
5982  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
5983  return Info.Ctx.getDeclAlign(DRE->getDecl(),
5984  /*RefAsPointee*/true