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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  /// Check that this refers to a valid subobject.
323  bool isValidSubobject() const {
324  if (Invalid)
325  return false;
326  return !isOnePastTheEnd();
327  }
328  /// Check that this refers to a valid subobject, and if not, produce a
329  /// relevant diagnostic and set the designator as invalid.
330  bool checkSubobject(EvalInfo &Info, const Expr *E, CheckSubobjectKind CSK);
331 
332  /// Update this designator to refer to the first element within this array.
333  void addArrayUnchecked(const ConstantArrayType *CAT) {
334  PathEntry Entry;
335  Entry.ArrayIndex = 0;
336  Entries.push_back(Entry);
337 
338  // This is a most-derived object.
339  MostDerivedType = CAT->getElementType();
340  MostDerivedIsArrayElement = true;
341  MostDerivedArraySize = CAT->getSize().getZExtValue();
342  MostDerivedPathLength = Entries.size();
343  }
344  /// Update this designator to refer to the first element within the array of
345  /// elements of type T. This is an array of unknown size.
346  void addUnsizedArrayUnchecked(QualType ElemTy) {
347  PathEntry Entry;
348  Entry.ArrayIndex = 0;
349  Entries.push_back(Entry);
350 
351  MostDerivedType = ElemTy;
352  MostDerivedIsArrayElement = true;
353  // The value in MostDerivedArraySize is undefined in this case. So, set it
354  // to an arbitrary value that's likely to loudly break things if it's
355  // used.
356  MostDerivedArraySize = AssumedSizeForUnsizedArray;
357  MostDerivedPathLength = Entries.size();
358  }
359  /// Update this designator to refer to the given base or member of this
360  /// object.
361  void addDeclUnchecked(const Decl *D, bool Virtual = false) {
362  PathEntry Entry;
363  APValue::BaseOrMemberType Value(D, Virtual);
364  Entry.BaseOrMember = Value.getOpaqueValue();
365  Entries.push_back(Entry);
366 
367  // If this isn't a base class, it's a new most-derived object.
368  if (const FieldDecl *FD = dyn_cast<FieldDecl>(D)) {
369  MostDerivedType = FD->getType();
370  MostDerivedIsArrayElement = false;
371  MostDerivedArraySize = 0;
372  MostDerivedPathLength = Entries.size();
373  }
374  }
375  /// Update this designator to refer to the given complex component.
376  void addComplexUnchecked(QualType EltTy, bool Imag) {
377  PathEntry Entry;
378  Entry.ArrayIndex = Imag;
379  Entries.push_back(Entry);
380 
381  // This is technically a most-derived object, though in practice this
382  // is unlikely to matter.
383  MostDerivedType = EltTy;
384  MostDerivedIsArrayElement = true;
385  MostDerivedArraySize = 2;
386  MostDerivedPathLength = Entries.size();
387  }
388  void diagnoseUnsizedArrayPointerArithmetic(EvalInfo &Info, const Expr *E);
389  void diagnosePointerArithmetic(EvalInfo &Info, const Expr *E,
390  const APSInt &N);
391  /// Add N to the address of this subobject.
392  void adjustIndex(EvalInfo &Info, const Expr *E, APSInt N) {
393  if (Invalid || !N) return;
394  uint64_t TruncatedN = N.extOrTrunc(64).getZExtValue();
395  if (isMostDerivedAnUnsizedArray()) {
396  diagnoseUnsizedArrayPointerArithmetic(Info, E);
397  // Can't verify -- trust that the user is doing the right thing (or if
398  // not, trust that the caller will catch the bad behavior).
399  // FIXME: Should we reject if this overflows, at least?
400  Entries.back().ArrayIndex += TruncatedN;
401  return;
402  }
403 
404  // [expr.add]p4: For the purposes of these operators, a pointer to a
405  // nonarray object behaves the same as a pointer to the first element of
406  // an array of length one with the type of the object as its element type.
407  bool IsArray = MostDerivedPathLength == Entries.size() &&
408  MostDerivedIsArrayElement;
409  uint64_t ArrayIndex =
410  IsArray ? Entries.back().ArrayIndex : (uint64_t)IsOnePastTheEnd;
411  uint64_t ArraySize =
412  IsArray ? getMostDerivedArraySize() : (uint64_t)1;
413 
414  if (N < -(int64_t)ArrayIndex || N > ArraySize - ArrayIndex) {
415  // Calculate the actual index in a wide enough type, so we can include
416  // it in the note.
417  N = N.extend(std::max<unsigned>(N.getBitWidth() + 1, 65));
418  (llvm::APInt&)N += ArrayIndex;
419  assert(N.ugt(ArraySize) && "bounds check failed for in-bounds index");
420  diagnosePointerArithmetic(Info, E, N);
421  setInvalid();
422  return;
423  }
424 
425  ArrayIndex += TruncatedN;
426  assert(ArrayIndex <= ArraySize &&
427  "bounds check succeeded for out-of-bounds index");
428 
429  if (IsArray)
430  Entries.back().ArrayIndex = ArrayIndex;
431  else
432  IsOnePastTheEnd = (ArrayIndex != 0);
433  }
434  };
435 
436  /// A stack frame in the constexpr call stack.
437  struct CallStackFrame {
438  EvalInfo &Info;
439 
440  /// Parent - The caller of this stack frame.
441  CallStackFrame *Caller;
442 
443  /// Callee - The function which was called.
444  const FunctionDecl *Callee;
445 
446  /// This - The binding for the this pointer in this call, if any.
447  const LValue *This;
448 
449  /// Arguments - Parameter bindings for this function call, indexed by
450  /// parameters' function scope indices.
451  APValue *Arguments;
452 
453  // Note that we intentionally use std::map here so that references to
454  // values are stable.
455  typedef std::pair<const void *, unsigned> MapKeyTy;
456  typedef std::map<MapKeyTy, APValue> MapTy;
457  /// Temporaries - Temporary lvalues materialized within this stack frame.
458  MapTy Temporaries;
459 
460  /// CallLoc - The location of the call expression for this call.
461  SourceLocation CallLoc;
462 
463  /// Index - The call index of this call.
464  unsigned Index;
465 
466  /// The stack of integers for tracking version numbers for temporaries.
467  SmallVector<unsigned, 2> TempVersionStack = {1};
468  unsigned CurTempVersion = TempVersionStack.back();
469 
470  unsigned getTempVersion() const { return TempVersionStack.back(); }
471 
472  void pushTempVersion() {
473  TempVersionStack.push_back(++CurTempVersion);
474  }
475 
476  void popTempVersion() {
477  TempVersionStack.pop_back();
478  }
479 
480  // FIXME: Adding this to every 'CallStackFrame' may have a nontrivial impact
481  // on the overall stack usage of deeply-recursing constexpr evaluataions.
482  // (We should cache this map rather than recomputing it repeatedly.)
483  // But let's try this and see how it goes; we can look into caching the map
484  // as a later change.
485 
486  /// LambdaCaptureFields - Mapping from captured variables/this to
487  /// corresponding data members in the closure class.
488  llvm::DenseMap<const VarDecl *, FieldDecl *> LambdaCaptureFields;
489  FieldDecl *LambdaThisCaptureField;
490 
491  CallStackFrame(EvalInfo &Info, SourceLocation CallLoc,
492  const FunctionDecl *Callee, const LValue *This,
493  APValue *Arguments);
494  ~CallStackFrame();
495 
496  // Return the temporary for Key whose version number is Version.
497  APValue *getTemporary(const void *Key, unsigned Version) {
498  MapKeyTy KV(Key, Version);
499  auto LB = Temporaries.lower_bound(KV);
500  if (LB != Temporaries.end() && LB->first == KV)
501  return &LB->second;
502  // Pair (Key,Version) wasn't found in the map. Check that no elements
503  // in the map have 'Key' as their key.
504  assert((LB == Temporaries.end() || LB->first.first != Key) &&
505  (LB == Temporaries.begin() || std::prev(LB)->first.first != Key) &&
506  "Element with key 'Key' found in map");
507  return nullptr;
508  }
509 
510  // Return the current temporary for Key in the map.
511  APValue *getCurrentTemporary(const void *Key) {
512  auto UB = Temporaries.upper_bound(MapKeyTy(Key, UINT_MAX));
513  if (UB != Temporaries.begin() && std::prev(UB)->first.first == Key)
514  return &std::prev(UB)->second;
515  return nullptr;
516  }
517 
518  // Return the version number of the current temporary for Key.
519  unsigned getCurrentTemporaryVersion(const void *Key) const {
520  auto UB = Temporaries.upper_bound(MapKeyTy(Key, UINT_MAX));
521  if (UB != Temporaries.begin() && std::prev(UB)->first.first == Key)
522  return std::prev(UB)->first.second;
523  return 0;
524  }
525 
526  APValue &createTemporary(const void *Key, bool IsLifetimeExtended);
527  };
528 
529  /// Temporarily override 'this'.
530  class ThisOverrideRAII {
531  public:
532  ThisOverrideRAII(CallStackFrame &Frame, const LValue *NewThis, bool Enable)
533  : Frame(Frame), OldThis(Frame.This) {
534  if (Enable)
535  Frame.This = NewThis;
536  }
537  ~ThisOverrideRAII() {
538  Frame.This = OldThis;
539  }
540  private:
541  CallStackFrame &Frame;
542  const LValue *OldThis;
543  };
544 
545  /// A partial diagnostic which we might know in advance that we are not going
546  /// to emit.
547  class OptionalDiagnostic {
549 
550  public:
551  explicit OptionalDiagnostic(PartialDiagnostic *Diag = nullptr)
552  : Diag(Diag) {}
553 
554  template<typename T>
555  OptionalDiagnostic &operator<<(const T &v) {
556  if (Diag)
557  *Diag << v;
558  return *this;
559  }
560 
561  OptionalDiagnostic &operator<<(const APSInt &I) {
562  if (Diag) {
563  SmallVector<char, 32> Buffer;
564  I.toString(Buffer);
565  *Diag << StringRef(Buffer.data(), Buffer.size());
566  }
567  return *this;
568  }
569 
570  OptionalDiagnostic &operator<<(const APFloat &F) {
571  if (Diag) {
572  // FIXME: Force the precision of the source value down so we don't
573  // print digits which are usually useless (we don't really care here if
574  // we truncate a digit by accident in edge cases). Ideally,
575  // APFloat::toString would automatically print the shortest
576  // representation which rounds to the correct value, but it's a bit
577  // tricky to implement.
578  unsigned precision =
579  llvm::APFloat::semanticsPrecision(F.getSemantics());
580  precision = (precision * 59 + 195) / 196;
581  SmallVector<char, 32> Buffer;
582  F.toString(Buffer, precision);
583  *Diag << StringRef(Buffer.data(), Buffer.size());
584  }
585  return *this;
586  }
587  };
588 
589  /// A cleanup, and a flag indicating whether it is lifetime-extended.
590  class Cleanup {
591  llvm::PointerIntPair<APValue*, 1, bool> Value;
592 
593  public:
594  Cleanup(APValue *Val, bool IsLifetimeExtended)
595  : Value(Val, IsLifetimeExtended) {}
596 
597  bool isLifetimeExtended() const { return Value.getInt(); }
598  void endLifetime() {
599  *Value.getPointer() = APValue();
600  }
601  };
602 
603  /// EvalInfo - This is a private struct used by the evaluator to capture
604  /// information about a subexpression as it is folded. It retains information
605  /// about the AST context, but also maintains information about the folded
606  /// expression.
607  ///
608  /// If an expression could be evaluated, it is still possible it is not a C
609  /// "integer constant expression" or constant expression. If not, this struct
610  /// captures information about how and why not.
611  ///
612  /// One bit of information passed *into* the request for constant folding
613  /// indicates whether the subexpression is "evaluated" or not according to C
614  /// rules. For example, the RHS of (0 && foo()) is not evaluated. We can
615  /// evaluate the expression regardless of what the RHS is, but C only allows
616  /// certain things in certain situations.
617  struct EvalInfo {
618  ASTContext &Ctx;
619 
620  /// EvalStatus - Contains information about the evaluation.
621  Expr::EvalStatus &EvalStatus;
622 
623  /// CurrentCall - The top of the constexpr call stack.
624  CallStackFrame *CurrentCall;
625 
626  /// CallStackDepth - The number of calls in the call stack right now.
627  unsigned CallStackDepth;
628 
629  /// NextCallIndex - The next call index to assign.
630  unsigned NextCallIndex;
631 
632  /// StepsLeft - The remaining number of evaluation steps we're permitted
633  /// to perform. This is essentially a limit for the number of statements
634  /// we will evaluate.
635  unsigned StepsLeft;
636 
637  /// BottomFrame - The frame in which evaluation started. This must be
638  /// initialized after CurrentCall and CallStackDepth.
639  CallStackFrame BottomFrame;
640 
641  /// A stack of values whose lifetimes end at the end of some surrounding
642  /// evaluation frame.
643  llvm::SmallVector<Cleanup, 16> CleanupStack;
644 
645  /// EvaluatingDecl - This is the declaration whose initializer is being
646  /// evaluated, if any.
647  APValue::LValueBase EvaluatingDecl;
648 
649  /// EvaluatingDeclValue - This is the value being constructed for the
650  /// declaration whose initializer is being evaluated, if any.
651  APValue *EvaluatingDeclValue;
652 
653  /// EvaluatingObject - Pair of the AST node that an lvalue represents and
654  /// the call index that that lvalue was allocated in.
655  typedef std::pair<APValue::LValueBase, std::pair<unsigned, unsigned>>
656  EvaluatingObject;
657 
658  /// EvaluatingConstructors - Set of objects that are currently being
659  /// constructed.
660  llvm::DenseSet<EvaluatingObject> EvaluatingConstructors;
661 
662  struct EvaluatingConstructorRAII {
663  EvalInfo &EI;
664  EvaluatingObject Object;
665  bool DidInsert;
666  EvaluatingConstructorRAII(EvalInfo &EI, EvaluatingObject Object)
667  : EI(EI), Object(Object) {
668  DidInsert = EI.EvaluatingConstructors.insert(Object).second;
669  }
670  ~EvaluatingConstructorRAII() {
671  if (DidInsert) EI.EvaluatingConstructors.erase(Object);
672  }
673  };
674 
675  bool isEvaluatingConstructor(APValue::LValueBase Decl, unsigned CallIndex,
676  unsigned Version) {
677  return EvaluatingConstructors.count(
678  EvaluatingObject(Decl, {CallIndex, Version}));
679  }
680 
681  /// The current array initialization index, if we're performing array
682  /// initialization.
683  uint64_t ArrayInitIndex = -1;
684 
685  /// HasActiveDiagnostic - Was the previous diagnostic stored? If so, further
686  /// notes attached to it will also be stored, otherwise they will not be.
687  bool HasActiveDiagnostic;
688 
689  /// Have we emitted a diagnostic explaining why we couldn't constant
690  /// fold (not just why it's not strictly a constant expression)?
691  bool HasFoldFailureDiagnostic;
692 
693  /// Whether or not we're currently speculatively evaluating.
694  bool IsSpeculativelyEvaluating;
695 
696  enum EvaluationMode {
697  /// Evaluate as a constant expression. Stop if we find that the expression
698  /// is not a constant expression.
699  EM_ConstantExpression,
700 
701  /// Evaluate as a potential constant expression. Keep going if we hit a
702  /// construct that we can't evaluate yet (because we don't yet know the
703  /// value of something) but stop if we hit something that could never be
704  /// a constant expression.
705  EM_PotentialConstantExpression,
706 
707  /// Fold the expression to a constant. Stop if we hit a side-effect that
708  /// we can't model.
709  EM_ConstantFold,
710 
711  /// Evaluate the expression looking for integer overflow and similar
712  /// issues. Don't worry about side-effects, and try to visit all
713  /// subexpressions.
714  EM_EvaluateForOverflow,
715 
716  /// Evaluate in any way we know how. Don't worry about side-effects that
717  /// can't be modeled.
718  EM_IgnoreSideEffects,
719 
720  /// Evaluate as a constant expression. Stop if we find that the expression
721  /// is not a constant expression. Some expressions can be retried in the
722  /// optimizer if we don't constant fold them here, but in an unevaluated
723  /// context we try to fold them immediately since the optimizer never
724  /// gets a chance to look at it.
725  EM_ConstantExpressionUnevaluated,
726 
727  /// Evaluate as a potential constant expression. Keep going if we hit a
728  /// construct that we can't evaluate yet (because we don't yet know the
729  /// value of something) but stop if we hit something that could never be
730  /// a constant expression. Some expressions can be retried in the
731  /// optimizer if we don't constant fold them here, but in an unevaluated
732  /// context we try to fold them immediately since the optimizer never
733  /// gets a chance to look at it.
734  EM_PotentialConstantExpressionUnevaluated,
735 
736  /// Evaluate as a constant expression. In certain scenarios, if:
737  /// - we find a MemberExpr with a base that can't be evaluated, or
738  /// - we find a variable initialized with a call to a function that has
739  /// the alloc_size attribute on it
740  /// then we may consider evaluation to have succeeded.
741  ///
742  /// In either case, the LValue returned shall have an invalid base; in the
743  /// former, the base will be the invalid MemberExpr, in the latter, the
744  /// base will be either the alloc_size CallExpr or a CastExpr wrapping
745  /// said CallExpr.
746  EM_OffsetFold,
747  } EvalMode;
748 
749  /// Are we checking whether the expression is a potential constant
750  /// expression?
751  bool checkingPotentialConstantExpression() const {
752  return EvalMode == EM_PotentialConstantExpression ||
753  EvalMode == EM_PotentialConstantExpressionUnevaluated;
754  }
755 
756  /// Are we checking an expression for overflow?
757  // FIXME: We should check for any kind of undefined or suspicious behavior
758  // in such constructs, not just overflow.
759  bool checkingForOverflow() { return EvalMode == EM_EvaluateForOverflow; }
760 
761  EvalInfo(const ASTContext &C, Expr::EvalStatus &S, EvaluationMode Mode)
762  : Ctx(const_cast<ASTContext &>(C)), EvalStatus(S), CurrentCall(nullptr),
763  CallStackDepth(0), NextCallIndex(1),
764  StepsLeft(getLangOpts().ConstexprStepLimit),
765  BottomFrame(*this, SourceLocation(), nullptr, nullptr, nullptr),
766  EvaluatingDecl((const ValueDecl *)nullptr),
767  EvaluatingDeclValue(nullptr), HasActiveDiagnostic(false),
768  HasFoldFailureDiagnostic(false), IsSpeculativelyEvaluating(false),
769  EvalMode(Mode) {}
770 
771  void setEvaluatingDecl(APValue::LValueBase Base, APValue &Value) {
772  EvaluatingDecl = Base;
773  EvaluatingDeclValue = &Value;
774  EvaluatingConstructors.insert({Base, {0, 0}});
775  }
776 
777  const LangOptions &getLangOpts() const { return Ctx.getLangOpts(); }
778 
779  bool CheckCallLimit(SourceLocation Loc) {
780  // Don't perform any constexpr calls (other than the call we're checking)
781  // when checking a potential constant expression.
782  if (checkingPotentialConstantExpression() && CallStackDepth > 1)
783  return false;
784  if (NextCallIndex == 0) {
785  // NextCallIndex has wrapped around.
786  FFDiag(Loc, diag::note_constexpr_call_limit_exceeded);
787  return false;
788  }
789  if (CallStackDepth <= getLangOpts().ConstexprCallDepth)
790  return true;
791  FFDiag(Loc, diag::note_constexpr_depth_limit_exceeded)
792  << getLangOpts().ConstexprCallDepth;
793  return false;
794  }
795 
796  CallStackFrame *getCallFrame(unsigned CallIndex) {
797  assert(CallIndex && "no call index in getCallFrame");
798  // We will eventually hit BottomFrame, which has Index 1, so Frame can't
799  // be null in this loop.
800  CallStackFrame *Frame = CurrentCall;
801  while (Frame->Index > CallIndex)
802  Frame = Frame->Caller;
803  return (Frame->Index == CallIndex) ? Frame : nullptr;
804  }
805 
806  bool nextStep(const Stmt *S) {
807  if (!StepsLeft) {
808  FFDiag(S->getLocStart(), diag::note_constexpr_step_limit_exceeded);
809  return false;
810  }
811  --StepsLeft;
812  return true;
813  }
814 
815  private:
816  /// Add a diagnostic to the diagnostics list.
817  PartialDiagnostic &addDiag(SourceLocation Loc, diag::kind DiagId) {
818  PartialDiagnostic PD(DiagId, Ctx.getDiagAllocator());
819  EvalStatus.Diag->push_back(std::make_pair(Loc, PD));
820  return EvalStatus.Diag->back().second;
821  }
822 
823  /// Add notes containing a call stack to the current point of evaluation.
824  void addCallStack(unsigned Limit);
825 
826  private:
827  OptionalDiagnostic Diag(SourceLocation Loc, diag::kind DiagId,
828  unsigned ExtraNotes, bool IsCCEDiag) {
829 
830  if (EvalStatus.Diag) {
831  // If we have a prior diagnostic, it will be noting that the expression
832  // isn't a constant expression. This diagnostic is more important,
833  // unless we require this evaluation to produce a constant expression.
834  //
835  // FIXME: We might want to show both diagnostics to the user in
836  // EM_ConstantFold mode.
837  if (!EvalStatus.Diag->empty()) {
838  switch (EvalMode) {
839  case EM_ConstantFold:
840  case EM_IgnoreSideEffects:
841  case EM_EvaluateForOverflow:
842  if (!HasFoldFailureDiagnostic)
843  break;
844  // We've already failed to fold something. Keep that diagnostic.
845  LLVM_FALLTHROUGH;
846  case EM_ConstantExpression:
847  case EM_PotentialConstantExpression:
848  case EM_ConstantExpressionUnevaluated:
849  case EM_PotentialConstantExpressionUnevaluated:
850  case EM_OffsetFold:
851  HasActiveDiagnostic = false;
852  return OptionalDiagnostic();
853  }
854  }
855 
856  unsigned CallStackNotes = CallStackDepth - 1;
857  unsigned Limit = Ctx.getDiagnostics().getConstexprBacktraceLimit();
858  if (Limit)
859  CallStackNotes = std::min(CallStackNotes, Limit + 1);
860  if (checkingPotentialConstantExpression())
861  CallStackNotes = 0;
862 
863  HasActiveDiagnostic = true;
864  HasFoldFailureDiagnostic = !IsCCEDiag;
865  EvalStatus.Diag->clear();
866  EvalStatus.Diag->reserve(1 + ExtraNotes + CallStackNotes);
867  addDiag(Loc, DiagId);
868  if (!checkingPotentialConstantExpression())
869  addCallStack(Limit);
870  return OptionalDiagnostic(&(*EvalStatus.Diag)[0].second);
871  }
872  HasActiveDiagnostic = false;
873  return OptionalDiagnostic();
874  }
875  public:
876  // Diagnose that the evaluation could not be folded (FF => FoldFailure)
877  OptionalDiagnostic
878  FFDiag(SourceLocation Loc,
879  diag::kind DiagId = diag::note_invalid_subexpr_in_const_expr,
880  unsigned ExtraNotes = 0) {
881  return Diag(Loc, DiagId, ExtraNotes, false);
882  }
883 
884  OptionalDiagnostic FFDiag(const Expr *E, diag::kind DiagId
885  = diag::note_invalid_subexpr_in_const_expr,
886  unsigned ExtraNotes = 0) {
887  if (EvalStatus.Diag)
888  return Diag(E->getExprLoc(), DiagId, ExtraNotes, /*IsCCEDiag*/false);
889  HasActiveDiagnostic = false;
890  return OptionalDiagnostic();
891  }
892 
893  /// Diagnose that the evaluation does not produce a C++11 core constant
894  /// expression.
895  ///
896  /// FIXME: Stop evaluating if we're in EM_ConstantExpression or
897  /// EM_PotentialConstantExpression mode and we produce one of these.
898  OptionalDiagnostic CCEDiag(SourceLocation Loc, diag::kind DiagId
899  = diag::note_invalid_subexpr_in_const_expr,
900  unsigned ExtraNotes = 0) {
901  // Don't override a previous diagnostic. Don't bother collecting
902  // diagnostics if we're evaluating for overflow.
903  if (!EvalStatus.Diag || !EvalStatus.Diag->empty()) {
904  HasActiveDiagnostic = false;
905  return OptionalDiagnostic();
906  }
907  return Diag(Loc, DiagId, ExtraNotes, true);
908  }
909  OptionalDiagnostic CCEDiag(const Expr *E, diag::kind DiagId
910  = diag::note_invalid_subexpr_in_const_expr,
911  unsigned ExtraNotes = 0) {
912  return CCEDiag(E->getExprLoc(), DiagId, ExtraNotes);
913  }
914  /// Add a note to a prior diagnostic.
915  OptionalDiagnostic Note(SourceLocation Loc, diag::kind DiagId) {
916  if (!HasActiveDiagnostic)
917  return OptionalDiagnostic();
918  return OptionalDiagnostic(&addDiag(Loc, DiagId));
919  }
920 
921  /// Add a stack of notes to a prior diagnostic.
922  void addNotes(ArrayRef<PartialDiagnosticAt> Diags) {
923  if (HasActiveDiagnostic) {
924  EvalStatus.Diag->insert(EvalStatus.Diag->end(),
925  Diags.begin(), Diags.end());
926  }
927  }
928 
929  /// Should we continue evaluation after encountering a side-effect that we
930  /// couldn't model?
931  bool keepEvaluatingAfterSideEffect() {
932  switch (EvalMode) {
933  case EM_PotentialConstantExpression:
934  case EM_PotentialConstantExpressionUnevaluated:
935  case EM_EvaluateForOverflow:
936  case EM_IgnoreSideEffects:
937  return true;
938 
939  case EM_ConstantExpression:
940  case EM_ConstantExpressionUnevaluated:
941  case EM_ConstantFold:
942  case EM_OffsetFold:
943  return false;
944  }
945  llvm_unreachable("Missed EvalMode case");
946  }
947 
948  /// Note that we have had a side-effect, and determine whether we should
949  /// keep evaluating.
950  bool noteSideEffect() {
951  EvalStatus.HasSideEffects = true;
952  return keepEvaluatingAfterSideEffect();
953  }
954 
955  /// Should we continue evaluation after encountering undefined behavior?
956  bool keepEvaluatingAfterUndefinedBehavior() {
957  switch (EvalMode) {
958  case EM_EvaluateForOverflow:
959  case EM_IgnoreSideEffects:
960  case EM_ConstantFold:
961  case EM_OffsetFold:
962  return true;
963 
964  case EM_PotentialConstantExpression:
965  case EM_PotentialConstantExpressionUnevaluated:
966  case EM_ConstantExpression:
967  case EM_ConstantExpressionUnevaluated:
968  return false;
969  }
970  llvm_unreachable("Missed EvalMode case");
971  }
972 
973  /// Note that we hit something that was technically undefined behavior, but
974  /// that we can evaluate past it (such as signed overflow or floating-point
975  /// division by zero.)
976  bool noteUndefinedBehavior() {
977  EvalStatus.HasUndefinedBehavior = true;
978  return keepEvaluatingAfterUndefinedBehavior();
979  }
980 
981  /// Should we continue evaluation as much as possible after encountering a
982  /// construct which can't be reduced to a value?
983  bool keepEvaluatingAfterFailure() {
984  if (!StepsLeft)
985  return false;
986 
987  switch (EvalMode) {
988  case EM_PotentialConstantExpression:
989  case EM_PotentialConstantExpressionUnevaluated:
990  case EM_EvaluateForOverflow:
991  return true;
992 
993  case EM_ConstantExpression:
994  case EM_ConstantExpressionUnevaluated:
995  case EM_ConstantFold:
996  case EM_IgnoreSideEffects:
997  case EM_OffsetFold:
998  return false;
999  }
1000  llvm_unreachable("Missed EvalMode case");
1001  }
1002 
1003  /// Notes that we failed to evaluate an expression that other expressions
1004  /// directly depend on, and determine if we should keep evaluating. This
1005  /// should only be called if we actually intend to keep evaluating.
1006  ///
1007  /// Call noteSideEffect() instead if we may be able to ignore the value that
1008  /// we failed to evaluate, e.g. if we failed to evaluate Foo() in:
1009  ///
1010  /// (Foo(), 1) // use noteSideEffect
1011  /// (Foo() || true) // use noteSideEffect
1012  /// Foo() + 1 // use noteFailure
1013  LLVM_NODISCARD bool noteFailure() {
1014  // Failure when evaluating some expression often means there is some
1015  // subexpression whose evaluation was skipped. Therefore, (because we
1016  // don't track whether we skipped an expression when unwinding after an
1017  // evaluation failure) every evaluation failure that bubbles up from a
1018  // subexpression implies that a side-effect has potentially happened. We
1019  // skip setting the HasSideEffects flag to true until we decide to
1020  // continue evaluating after that point, which happens here.
1021  bool KeepGoing = keepEvaluatingAfterFailure();
1022  EvalStatus.HasSideEffects |= KeepGoing;
1023  return KeepGoing;
1024  }
1025 
1026  class ArrayInitLoopIndex {
1027  EvalInfo &Info;
1028  uint64_t OuterIndex;
1029 
1030  public:
1031  ArrayInitLoopIndex(EvalInfo &Info)
1032  : Info(Info), OuterIndex(Info.ArrayInitIndex) {
1033  Info.ArrayInitIndex = 0;
1034  }
1035  ~ArrayInitLoopIndex() { Info.ArrayInitIndex = OuterIndex; }
1036 
1037  operator uint64_t&() { return Info.ArrayInitIndex; }
1038  };
1039  };
1040 
1041  /// Object used to treat all foldable expressions as constant expressions.
1042  struct FoldConstant {
1043  EvalInfo &Info;
1044  bool Enabled;
1045  bool HadNoPriorDiags;
1046  EvalInfo::EvaluationMode OldMode;
1047 
1048  explicit FoldConstant(EvalInfo &Info, bool Enabled)
1049  : Info(Info),
1050  Enabled(Enabled),
1051  HadNoPriorDiags(Info.EvalStatus.Diag &&
1052  Info.EvalStatus.Diag->empty() &&
1053  !Info.EvalStatus.HasSideEffects),
1054  OldMode(Info.EvalMode) {
1055  if (Enabled &&
1056  (Info.EvalMode == EvalInfo::EM_ConstantExpression ||
1057  Info.EvalMode == EvalInfo::EM_ConstantExpressionUnevaluated))
1058  Info.EvalMode = EvalInfo::EM_ConstantFold;
1059  }
1060  void keepDiagnostics() { Enabled = false; }
1061  ~FoldConstant() {
1062  if (Enabled && HadNoPriorDiags && !Info.EvalStatus.Diag->empty() &&
1063  !Info.EvalStatus.HasSideEffects)
1064  Info.EvalStatus.Diag->clear();
1065  Info.EvalMode = OldMode;
1066  }
1067  };
1068 
1069  /// RAII object used to treat the current evaluation as the correct pointer
1070  /// offset fold for the current EvalMode
1071  struct FoldOffsetRAII {
1072  EvalInfo &Info;
1073  EvalInfo::EvaluationMode OldMode;
1074  explicit FoldOffsetRAII(EvalInfo &Info)
1075  : Info(Info), OldMode(Info.EvalMode) {
1076  if (!Info.checkingPotentialConstantExpression())
1077  Info.EvalMode = EvalInfo::EM_OffsetFold;
1078  }
1079 
1080  ~FoldOffsetRAII() { Info.EvalMode = OldMode; }
1081  };
1082 
1083  /// RAII object used to optionally suppress diagnostics and side-effects from
1084  /// a speculative evaluation.
1085  class SpeculativeEvaluationRAII {
1086  EvalInfo *Info = nullptr;
1087  Expr::EvalStatus OldStatus;
1088  bool OldIsSpeculativelyEvaluating;
1089 
1090  void moveFromAndCancel(SpeculativeEvaluationRAII &&Other) {
1091  Info = Other.Info;
1092  OldStatus = Other.OldStatus;
1093  OldIsSpeculativelyEvaluating = Other.OldIsSpeculativelyEvaluating;
1094  Other.Info = nullptr;
1095  }
1096 
1097  void maybeRestoreState() {
1098  if (!Info)
1099  return;
1100 
1101  Info->EvalStatus = OldStatus;
1102  Info->IsSpeculativelyEvaluating = OldIsSpeculativelyEvaluating;
1103  }
1104 
1105  public:
1106  SpeculativeEvaluationRAII() = default;
1107 
1108  SpeculativeEvaluationRAII(
1109  EvalInfo &Info, SmallVectorImpl<PartialDiagnosticAt> *NewDiag = nullptr)
1110  : Info(&Info), OldStatus(Info.EvalStatus),
1111  OldIsSpeculativelyEvaluating(Info.IsSpeculativelyEvaluating) {
1112  Info.EvalStatus.Diag = NewDiag;
1113  Info.IsSpeculativelyEvaluating = true;
1114  }
1115 
1116  SpeculativeEvaluationRAII(const SpeculativeEvaluationRAII &Other) = delete;
1117  SpeculativeEvaluationRAII(SpeculativeEvaluationRAII &&Other) {
1118  moveFromAndCancel(std::move(Other));
1119  }
1120 
1121  SpeculativeEvaluationRAII &operator=(SpeculativeEvaluationRAII &&Other) {
1122  maybeRestoreState();
1123  moveFromAndCancel(std::move(Other));
1124  return *this;
1125  }
1126 
1127  ~SpeculativeEvaluationRAII() { maybeRestoreState(); }
1128  };
1129 
1130  /// RAII object wrapping a full-expression or block scope, and handling
1131  /// the ending of the lifetime of temporaries created within it.
1132  template<bool IsFullExpression>
1133  class ScopeRAII {
1134  EvalInfo &Info;
1135  unsigned OldStackSize;
1136  public:
1137  ScopeRAII(EvalInfo &Info)
1138  : Info(Info), OldStackSize(Info.CleanupStack.size()) {
1139  // Push a new temporary version. This is needed to distinguish between
1140  // temporaries created in different iterations of a loop.
1141  Info.CurrentCall->pushTempVersion();
1142  }
1143  ~ScopeRAII() {
1144  // Body moved to a static method to encourage the compiler to inline away
1145  // instances of this class.
1146  cleanup(Info, OldStackSize);
1147  Info.CurrentCall->popTempVersion();
1148  }
1149  private:
1150  static void cleanup(EvalInfo &Info, unsigned OldStackSize) {
1151  unsigned NewEnd = OldStackSize;
1152  for (unsigned I = OldStackSize, N = Info.CleanupStack.size();
1153  I != N; ++I) {
1154  if (IsFullExpression && Info.CleanupStack[I].isLifetimeExtended()) {
1155  // Full-expression cleanup of a lifetime-extended temporary: nothing
1156  // to do, just move this cleanup to the right place in the stack.
1157  std::swap(Info.CleanupStack[I], Info.CleanupStack[NewEnd]);
1158  ++NewEnd;
1159  } else {
1160  // End the lifetime of the object.
1161  Info.CleanupStack[I].endLifetime();
1162  }
1163  }
1164  Info.CleanupStack.erase(Info.CleanupStack.begin() + NewEnd,
1165  Info.CleanupStack.end());
1166  }
1167  };
1168  typedef ScopeRAII<false> BlockScopeRAII;
1169  typedef ScopeRAII<true> FullExpressionRAII;
1170 }
1171 
1172 bool SubobjectDesignator::checkSubobject(EvalInfo &Info, const Expr *E,
1173  CheckSubobjectKind CSK) {
1174  if (Invalid)
1175  return false;
1176  if (isOnePastTheEnd()) {
1177  Info.CCEDiag(E, diag::note_constexpr_past_end_subobject)
1178  << CSK;
1179  setInvalid();
1180  return false;
1181  }
1182  // Note, we do not diagnose if isMostDerivedAnUnsizedArray(), because there
1183  // must actually be at least one array element; even a VLA cannot have a
1184  // bound of zero. And if our index is nonzero, we already had a CCEDiag.
1185  return true;
1186 }
1187 
1188 void SubobjectDesignator::diagnoseUnsizedArrayPointerArithmetic(EvalInfo &Info,
1189  const Expr *E) {
1190  Info.CCEDiag(E, diag::note_constexpr_unsized_array_indexed);
1191  // Do not set the designator as invalid: we can represent this situation,
1192  // and correct handling of __builtin_object_size requires us to do so.
1193 }
1194 
1195 void SubobjectDesignator::diagnosePointerArithmetic(EvalInfo &Info,
1196  const Expr *E,
1197  const APSInt &N) {
1198  // If we're complaining, we must be able to statically determine the size of
1199  // the most derived array.
1200  if (MostDerivedPathLength == Entries.size() && MostDerivedIsArrayElement)
1201  Info.CCEDiag(E, diag::note_constexpr_array_index)
1202  << N << /*array*/ 0
1203  << static_cast<unsigned>(getMostDerivedArraySize());
1204  else
1205  Info.CCEDiag(E, diag::note_constexpr_array_index)
1206  << N << /*non-array*/ 1;
1207  setInvalid();
1208 }
1209 
1210 CallStackFrame::CallStackFrame(EvalInfo &Info, SourceLocation CallLoc,
1211  const FunctionDecl *Callee, const LValue *This,
1212  APValue *Arguments)
1213  : Info(Info), Caller(Info.CurrentCall), Callee(Callee), This(This),
1214  Arguments(Arguments), CallLoc(CallLoc), Index(Info.NextCallIndex++) {
1215  Info.CurrentCall = this;
1216  ++Info.CallStackDepth;
1217 }
1218 
1219 CallStackFrame::~CallStackFrame() {
1220  assert(Info.CurrentCall == this && "calls retired out of order");
1221  --Info.CallStackDepth;
1222  Info.CurrentCall = Caller;
1223 }
1224 
1225 APValue &CallStackFrame::createTemporary(const void *Key,
1226  bool IsLifetimeExtended) {
1227  unsigned Version = Info.CurrentCall->getTempVersion();
1228  APValue &Result = Temporaries[MapKeyTy(Key, Version)];
1229  assert(Result.isUninit() && "temporary created multiple times");
1230  Info.CleanupStack.push_back(Cleanup(&Result, IsLifetimeExtended));
1231  return Result;
1232 }
1233 
1234 static void describeCall(CallStackFrame *Frame, raw_ostream &Out);
1235 
1236 void EvalInfo::addCallStack(unsigned Limit) {
1237  // Determine which calls to skip, if any.
1238  unsigned ActiveCalls = CallStackDepth - 1;
1239  unsigned SkipStart = ActiveCalls, SkipEnd = SkipStart;
1240  if (Limit && Limit < ActiveCalls) {
1241  SkipStart = Limit / 2 + Limit % 2;
1242  SkipEnd = ActiveCalls - Limit / 2;
1243  }
1244 
1245  // Walk the call stack and add the diagnostics.
1246  unsigned CallIdx = 0;
1247  for (CallStackFrame *Frame = CurrentCall; Frame != &BottomFrame;
1248  Frame = Frame->Caller, ++CallIdx) {
1249  // Skip this call?
1250  if (CallIdx >= SkipStart && CallIdx < SkipEnd) {
1251  if (CallIdx == SkipStart) {
1252  // Note that we're skipping calls.
1253  addDiag(Frame->CallLoc, diag::note_constexpr_calls_suppressed)
1254  << unsigned(ActiveCalls - Limit);
1255  }
1256  continue;
1257  }
1258 
1259  // Use a different note for an inheriting constructor, because from the
1260  // user's perspective it's not really a function at all.
1261  if (auto *CD = dyn_cast_or_null<CXXConstructorDecl>(Frame->Callee)) {
1262  if (CD->isInheritingConstructor()) {
1263  addDiag(Frame->CallLoc, diag::note_constexpr_inherited_ctor_call_here)
1264  << CD->getParent();
1265  continue;
1266  }
1267  }
1268 
1269  SmallVector<char, 128> Buffer;
1270  llvm::raw_svector_ostream Out(Buffer);
1271  describeCall(Frame, Out);
1272  addDiag(Frame->CallLoc, diag::note_constexpr_call_here) << Out.str();
1273  }
1274 }
1275 
1276 namespace {
1277  struct ComplexValue {
1278  private:
1279  bool IsInt;
1280 
1281  public:
1282  APSInt IntReal, IntImag;
1283  APFloat FloatReal, FloatImag;
1284 
1285  ComplexValue() : FloatReal(APFloat::Bogus()), FloatImag(APFloat::Bogus()) {}
1286 
1287  void makeComplexFloat() { IsInt = false; }
1288  bool isComplexFloat() const { return !IsInt; }
1289  APFloat &getComplexFloatReal() { return FloatReal; }
1290  APFloat &getComplexFloatImag() { return FloatImag; }
1291 
1292  void makeComplexInt() { IsInt = true; }
1293  bool isComplexInt() const { return IsInt; }
1294  APSInt &getComplexIntReal() { return IntReal; }
1295  APSInt &getComplexIntImag() { return IntImag; }
1296 
1297  void moveInto(APValue &v) const {
1298  if (isComplexFloat())
1299  v = APValue(FloatReal, FloatImag);
1300  else
1301  v = APValue(IntReal, IntImag);
1302  }
1303  void setFrom(const APValue &v) {
1304  assert(v.isComplexFloat() || v.isComplexInt());
1305  if (v.isComplexFloat()) {
1306  makeComplexFloat();
1307  FloatReal = v.getComplexFloatReal();
1308  FloatImag = v.getComplexFloatImag();
1309  } else {
1310  makeComplexInt();
1311  IntReal = v.getComplexIntReal();
1312  IntImag = v.getComplexIntImag();
1313  }
1314  }
1315  };
1316 
1317  struct LValue {
1318  APValue::LValueBase Base;
1319  CharUnits Offset;
1320  SubobjectDesignator Designator;
1321  bool IsNullPtr : 1;
1322  bool InvalidBase : 1;
1323 
1324  const APValue::LValueBase getLValueBase() const { return Base; }
1325  CharUnits &getLValueOffset() { return Offset; }
1326  const CharUnits &getLValueOffset() const { return Offset; }
1327  SubobjectDesignator &getLValueDesignator() { return Designator; }
1328  const SubobjectDesignator &getLValueDesignator() const { return Designator;}
1329  bool isNullPointer() const { return IsNullPtr;}
1330 
1331  unsigned getLValueCallIndex() const { return Base.getCallIndex(); }
1332  unsigned getLValueVersion() const { return Base.getVersion(); }
1333 
1334  void moveInto(APValue &V) const {
1335  if (Designator.Invalid)
1336  V = APValue(Base, Offset, APValue::NoLValuePath(), IsNullPtr);
1337  else {
1338  assert(!InvalidBase && "APValues can't handle invalid LValue bases");
1339  V = APValue(Base, Offset, Designator.Entries,
1340  Designator.IsOnePastTheEnd, IsNullPtr);
1341  }
1342  }
1343  void setFrom(ASTContext &Ctx, const APValue &V) {
1344  assert(V.isLValue() && "Setting LValue from a non-LValue?");
1345  Base = V.getLValueBase();
1346  Offset = V.getLValueOffset();
1347  InvalidBase = false;
1348  Designator = SubobjectDesignator(Ctx, V);
1349  IsNullPtr = V.isNullPointer();
1350  }
1351 
1352  void set(APValue::LValueBase B, bool BInvalid = false) {
1353 #ifndef NDEBUG
1354  // We only allow a few types of invalid bases. Enforce that here.
1355  if (BInvalid) {
1356  const auto *E = B.get<const Expr *>();
1357  assert((isa<MemberExpr>(E) || tryUnwrapAllocSizeCall(E)) &&
1358  "Unexpected type of invalid base");
1359  }
1360 #endif
1361 
1362  Base = B;
1363  Offset = CharUnits::fromQuantity(0);
1364  InvalidBase = BInvalid;
1365  Designator = SubobjectDesignator(getType(B));
1366  IsNullPtr = false;
1367  }
1368 
1369  void setNull(QualType PointerTy, uint64_t TargetVal) {
1370  Base = (Expr *)nullptr;
1371  Offset = CharUnits::fromQuantity(TargetVal);
1372  InvalidBase = false;
1373  Designator = SubobjectDesignator(PointerTy->getPointeeType());
1374  IsNullPtr = true;
1375  }
1376 
1377  void setInvalid(APValue::LValueBase B, unsigned I = 0) {
1378  set(B, true);
1379  }
1380 
1381  // Check that this LValue is not based on a null pointer. If it is, produce
1382  // a diagnostic and mark the designator as invalid.
1383  bool checkNullPointer(EvalInfo &Info, const Expr *E,
1384  CheckSubobjectKind CSK) {
1385  if (Designator.Invalid)
1386  return false;
1387  if (IsNullPtr) {
1388  Info.CCEDiag(E, diag::note_constexpr_null_subobject)
1389  << CSK;
1390  Designator.setInvalid();
1391  return false;
1392  }
1393  return true;
1394  }
1395 
1396  // Check this LValue refers to an object. If not, set the designator to be
1397  // invalid and emit a diagnostic.
1398  bool checkSubobject(EvalInfo &Info, const Expr *E, CheckSubobjectKind CSK) {
1399  return (CSK == CSK_ArrayToPointer || checkNullPointer(Info, E, CSK)) &&
1400  Designator.checkSubobject(Info, E, CSK);
1401  }
1402 
1403  void addDecl(EvalInfo &Info, const Expr *E,
1404  const Decl *D, bool Virtual = false) {
1405  if (checkSubobject(Info, E, isa<FieldDecl>(D) ? CSK_Field : CSK_Base))
1406  Designator.addDeclUnchecked(D, Virtual);
1407  }
1408  void addUnsizedArray(EvalInfo &Info, const Expr *E, QualType ElemTy) {
1409  if (!Designator.Entries.empty()) {
1410  Info.CCEDiag(E, diag::note_constexpr_unsupported_unsized_array);
1411  Designator.setInvalid();
1412  return;
1413  }
1414  if (checkSubobject(Info, E, CSK_ArrayToPointer)) {
1415  assert(getType(Base)->isPointerType() || getType(Base)->isArrayType());
1416  Designator.FirstEntryIsAnUnsizedArray = true;
1417  Designator.addUnsizedArrayUnchecked(ElemTy);
1418  }
1419  }
1420  void addArray(EvalInfo &Info, const Expr *E, const ConstantArrayType *CAT) {
1421  if (checkSubobject(Info, E, CSK_ArrayToPointer))
1422  Designator.addArrayUnchecked(CAT);
1423  }
1424  void addComplex(EvalInfo &Info, const Expr *E, QualType EltTy, bool Imag) {
1425  if (checkSubobject(Info, E, Imag ? CSK_Imag : CSK_Real))
1426  Designator.addComplexUnchecked(EltTy, Imag);
1427  }
1428  void clearIsNullPointer() {
1429  IsNullPtr = false;
1430  }
1431  void adjustOffsetAndIndex(EvalInfo &Info, const Expr *E,
1432  const APSInt &Index, CharUnits ElementSize) {
1433  // An index of 0 has no effect. (In C, adding 0 to a null pointer is UB,
1434  // but we're not required to diagnose it and it's valid in C++.)
1435  if (!Index)
1436  return;
1437 
1438  // Compute the new offset in the appropriate width, wrapping at 64 bits.
1439  // FIXME: When compiling for a 32-bit target, we should use 32-bit
1440  // offsets.
1441  uint64_t Offset64 = Offset.getQuantity();
1442  uint64_t ElemSize64 = ElementSize.getQuantity();
1443  uint64_t Index64 = Index.extOrTrunc(64).getZExtValue();
1444  Offset = CharUnits::fromQuantity(Offset64 + ElemSize64 * Index64);
1445 
1446  if (checkNullPointer(Info, E, CSK_ArrayIndex))
1447  Designator.adjustIndex(Info, E, Index);
1448  clearIsNullPointer();
1449  }
1450  void adjustOffset(CharUnits N) {
1451  Offset += N;
1452  if (N.getQuantity())
1453  clearIsNullPointer();
1454  }
1455  };
1456 
1457  struct MemberPtr {
1458  MemberPtr() {}
1459  explicit MemberPtr(const ValueDecl *Decl) :
1460  DeclAndIsDerivedMember(Decl, false), Path() {}
1461 
1462  /// The member or (direct or indirect) field referred to by this member
1463  /// pointer, or 0 if this is a null member pointer.
1464  const ValueDecl *getDecl() const {
1465  return DeclAndIsDerivedMember.getPointer();
1466  }
1467  /// Is this actually a member of some type derived from the relevant class?
1468  bool isDerivedMember() const {
1469  return DeclAndIsDerivedMember.getInt();
1470  }
1471  /// Get the class which the declaration actually lives in.
1472  const CXXRecordDecl *getContainingRecord() const {
1473  return cast<CXXRecordDecl>(
1474  DeclAndIsDerivedMember.getPointer()->getDeclContext());
1475  }
1476 
1477  void moveInto(APValue &V) const {
1478  V = APValue(getDecl(), isDerivedMember(), Path);
1479  }
1480  void setFrom(const APValue &V) {
1481  assert(V.isMemberPointer());
1482  DeclAndIsDerivedMember.setPointer(V.getMemberPointerDecl());
1483  DeclAndIsDerivedMember.setInt(V.isMemberPointerToDerivedMember());
1484  Path.clear();
1486  Path.insert(Path.end(), P.begin(), P.end());
1487  }
1488 
1489  /// DeclAndIsDerivedMember - The member declaration, and a flag indicating
1490  /// whether the member is a member of some class derived from the class type
1491  /// of the member pointer.
1492  llvm::PointerIntPair<const ValueDecl*, 1, bool> DeclAndIsDerivedMember;
1493  /// Path - The path of base/derived classes from the member declaration's
1494  /// class (exclusive) to the class type of the member pointer (inclusive).
1496 
1497  /// Perform a cast towards the class of the Decl (either up or down the
1498  /// hierarchy).
1499  bool castBack(const CXXRecordDecl *Class) {
1500  assert(!Path.empty());
1501  const CXXRecordDecl *Expected;
1502  if (Path.size() >= 2)
1503  Expected = Path[Path.size() - 2];
1504  else
1505  Expected = getContainingRecord();
1506  if (Expected->getCanonicalDecl() != Class->getCanonicalDecl()) {
1507  // C++11 [expr.static.cast]p12: In a conversion from (D::*) to (B::*),
1508  // if B does not contain the original member and is not a base or
1509  // derived class of the class containing the original member, the result
1510  // of the cast is undefined.
1511  // C++11 [conv.mem]p2 does not cover this case for a cast from (B::*) to
1512  // (D::*). We consider that to be a language defect.
1513  return false;
1514  }
1515  Path.pop_back();
1516  return true;
1517  }
1518  /// Perform a base-to-derived member pointer cast.
1519  bool castToDerived(const CXXRecordDecl *Derived) {
1520  if (!getDecl())
1521  return true;
1522  if (!isDerivedMember()) {
1523  Path.push_back(Derived);
1524  return true;
1525  }
1526  if (!castBack(Derived))
1527  return false;
1528  if (Path.empty())
1529  DeclAndIsDerivedMember.setInt(false);
1530  return true;
1531  }
1532  /// Perform a derived-to-base member pointer cast.
1533  bool castToBase(const CXXRecordDecl *Base) {
1534  if (!getDecl())
1535  return true;
1536  if (Path.empty())
1537  DeclAndIsDerivedMember.setInt(true);
1538  if (isDerivedMember()) {
1539  Path.push_back(Base);
1540  return true;
1541  }
1542  return castBack(Base);
1543  }
1544  };
1545 
1546  /// Compare two member pointers, which are assumed to be of the same type.
1547  static bool operator==(const MemberPtr &LHS, const MemberPtr &RHS) {
1548  if (!LHS.getDecl() || !RHS.getDecl())
1549  return !LHS.getDecl() && !RHS.getDecl();
1550  if (LHS.getDecl()->getCanonicalDecl() != RHS.getDecl()->getCanonicalDecl())
1551  return false;
1552  return LHS.Path == RHS.Path;
1553  }
1554 }
1555 
1556 static bool Evaluate(APValue &Result, EvalInfo &Info, const Expr *E);
1557 static bool EvaluateInPlace(APValue &Result, EvalInfo &Info,
1558  const LValue &This, const Expr *E,
1559  bool AllowNonLiteralTypes = false);
1560 static bool EvaluateLValue(const Expr *E, LValue &Result, EvalInfo &Info,
1561  bool InvalidBaseOK = false);
1562 static bool EvaluatePointer(const Expr *E, LValue &Result, EvalInfo &Info,
1563  bool InvalidBaseOK = false);
1564 static bool EvaluateMemberPointer(const Expr *E, MemberPtr &Result,
1565  EvalInfo &Info);
1566 static bool EvaluateTemporary(const Expr *E, LValue &Result, EvalInfo &Info);
1567 static bool EvaluateInteger(const Expr *E, APSInt &Result, EvalInfo &Info);
1568 static bool EvaluateIntegerOrLValue(const Expr *E, APValue &Result,
1569  EvalInfo &Info);
1570 static bool EvaluateFloat(const Expr *E, APFloat &Result, EvalInfo &Info);
1571 static bool EvaluateComplex(const Expr *E, ComplexValue &Res, EvalInfo &Info);
1572 static bool EvaluateAtomic(const Expr *E, const LValue *This, APValue &Result,
1573  EvalInfo &Info);
1574 static bool EvaluateAsRValue(EvalInfo &Info, const Expr *E, APValue &Result);
1575 
1576 //===----------------------------------------------------------------------===//
1577 // Misc utilities
1578 //===----------------------------------------------------------------------===//
1579 
1580 /// A helper function to create a temporary and set an LValue.
1581 template <class KeyTy>
1582 static APValue &createTemporary(const KeyTy *Key, bool IsLifetimeExtended,
1583  LValue &LV, CallStackFrame &Frame) {
1584  LV.set({Key, Frame.Info.CurrentCall->Index,
1585  Frame.Info.CurrentCall->getTempVersion()});
1586  return Frame.createTemporary(Key, IsLifetimeExtended);
1587 }
1588 
1589 /// Negate an APSInt in place, converting it to a signed form if necessary, and
1590 /// preserving its value (by extending by up to one bit as needed).
1591 static void negateAsSigned(APSInt &Int) {
1592  if (Int.isUnsigned() || Int.isMinSignedValue()) {
1593  Int = Int.extend(Int.getBitWidth() + 1);
1594  Int.setIsSigned(true);
1595  }
1596  Int = -Int;
1597 }
1598 
1599 /// Produce a string describing the given constexpr call.
1600 static void describeCall(CallStackFrame *Frame, raw_ostream &Out) {
1601  unsigned ArgIndex = 0;
1602  bool IsMemberCall = isa<CXXMethodDecl>(Frame->Callee) &&
1603  !isa<CXXConstructorDecl>(Frame->Callee) &&
1604  cast<CXXMethodDecl>(Frame->Callee)->isInstance();
1605 
1606  if (!IsMemberCall)
1607  Out << *Frame->Callee << '(';
1608 
1609  if (Frame->This && IsMemberCall) {
1610  APValue Val;
1611  Frame->This->moveInto(Val);
1612  Val.printPretty(Out, Frame->Info.Ctx,
1613  Frame->This->Designator.MostDerivedType);
1614  // FIXME: Add parens around Val if needed.
1615  Out << "->" << *Frame->Callee << '(';
1616  IsMemberCall = false;
1617  }
1618 
1619  for (FunctionDecl::param_const_iterator I = Frame->Callee->param_begin(),
1620  E = Frame->Callee->param_end(); I != E; ++I, ++ArgIndex) {
1621  if (ArgIndex > (unsigned)IsMemberCall)
1622  Out << ", ";
1623 
1624  const ParmVarDecl *Param = *I;
1625  const APValue &Arg = Frame->Arguments[ArgIndex];
1626  Arg.printPretty(Out, Frame->Info.Ctx, Param->getType());
1627 
1628  if (ArgIndex == 0 && IsMemberCall)
1629  Out << "->" << *Frame->Callee << '(';
1630  }
1631 
1632  Out << ')';
1633 }
1634 
1635 /// Evaluate an expression to see if it had side-effects, and discard its
1636 /// result.
1637 /// \return \c true if the caller should keep evaluating.
1638 static bool EvaluateIgnoredValue(EvalInfo &Info, const Expr *E) {
1639  APValue Scratch;
1640  if (!Evaluate(Scratch, Info, E))
1641  // We don't need the value, but we might have skipped a side effect here.
1642  return Info.noteSideEffect();
1643  return true;
1644 }
1645 
1646 /// Should this call expression be treated as a string literal?
1647 static bool IsStringLiteralCall(const CallExpr *E) {
1648  unsigned Builtin = E->getBuiltinCallee();
1649  return (Builtin == Builtin::BI__builtin___CFStringMakeConstantString ||
1650  Builtin == Builtin::BI__builtin___NSStringMakeConstantString);
1651 }
1652 
1654  // C++11 [expr.const]p3 An address constant expression is a prvalue core
1655  // constant expression of pointer type that evaluates to...
1656 
1657  // ... a null pointer value, or a prvalue core constant expression of type
1658  // std::nullptr_t.
1659  if (!B) return true;
1660 
1661  if (const ValueDecl *D = B.dyn_cast<const ValueDecl*>()) {
1662  // ... the address of an object with static storage duration,
1663  if (const VarDecl *VD = dyn_cast<VarDecl>(D))
1664  return VD->hasGlobalStorage();
1665  // ... the address of a function,
1666  return isa<FunctionDecl>(D);
1667  }
1668 
1669  const Expr *E = B.get<const Expr*>();
1670  switch (E->getStmtClass()) {
1671  default:
1672  return false;
1673  case Expr::CompoundLiteralExprClass: {
1674  const CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
1675  return CLE->isFileScope() && CLE->isLValue();
1676  }
1677  case Expr::MaterializeTemporaryExprClass:
1678  // A materialized temporary might have been lifetime-extended to static
1679  // storage duration.
1680  return cast<MaterializeTemporaryExpr>(E)->getStorageDuration() == SD_Static;
1681  // A string literal has static storage duration.
1682  case Expr::StringLiteralClass:
1683  case Expr::PredefinedExprClass:
1684  case Expr::ObjCStringLiteralClass:
1685  case Expr::ObjCEncodeExprClass:
1686  case Expr::CXXTypeidExprClass:
1687  case Expr::CXXUuidofExprClass:
1688  return true;
1689  case Expr::CallExprClass:
1690  return IsStringLiteralCall(cast<CallExpr>(E));
1691  // For GCC compatibility, &&label has static storage duration.
1692  case Expr::AddrLabelExprClass:
1693  return true;
1694  // A Block literal expression may be used as the initialization value for
1695  // Block variables at global or local static scope.
1696  case Expr::BlockExprClass:
1697  return !cast<BlockExpr>(E)->getBlockDecl()->hasCaptures();
1698  case Expr::ImplicitValueInitExprClass:
1699  // FIXME:
1700  // We can never form an lvalue with an implicit value initialization as its
1701  // base through expression evaluation, so these only appear in one case: the
1702  // implicit variable declaration we invent when checking whether a constexpr
1703  // constructor can produce a constant expression. We must assume that such
1704  // an expression might be a global lvalue.
1705  return true;
1706  }
1707 }
1708 
1709 static void NoteLValueLocation(EvalInfo &Info, APValue::LValueBase Base) {
1710  assert(Base && "no location for a null lvalue");
1711  const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
1712  if (VD)
1713  Info.Note(VD->getLocation(), diag::note_declared_at);
1714  else
1715  Info.Note(Base.get<const Expr*>()->getExprLoc(),
1716  diag::note_constexpr_temporary_here);
1717 }
1718 
1719 /// Check that this reference or pointer core constant expression is a valid
1720 /// value for an address or reference constant expression. Return true if we
1721 /// can fold this expression, whether or not it's a constant expression.
1722 static bool CheckLValueConstantExpression(EvalInfo &Info, SourceLocation Loc,
1723  QualType Type, const LValue &LVal,
1724  Expr::ConstExprUsage Usage) {
1725  bool IsReferenceType = Type->isReferenceType();
1726 
1727  APValue::LValueBase Base = LVal.getLValueBase();
1728  const SubobjectDesignator &Designator = LVal.getLValueDesignator();
1729 
1730  // Check that the object is a global. Note that the fake 'this' object we
1731  // manufacture when checking potential constant expressions is conservatively
1732  // assumed to be global here.
1733  if (!IsGlobalLValue(Base)) {
1734  if (Info.getLangOpts().CPlusPlus11) {
1735  const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
1736  Info.FFDiag(Loc, diag::note_constexpr_non_global, 1)
1737  << IsReferenceType << !Designator.Entries.empty()
1738  << !!VD << VD;
1739  NoteLValueLocation(Info, Base);
1740  } else {
1741  Info.FFDiag(Loc);
1742  }
1743  // Don't allow references to temporaries to escape.
1744  return false;
1745  }
1746  assert((Info.checkingPotentialConstantExpression() ||
1747  LVal.getLValueCallIndex() == 0) &&
1748  "have call index for global lvalue");
1749 
1750  if (const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>()) {
1751  if (const VarDecl *Var = dyn_cast<const VarDecl>(VD)) {
1752  // Check if this is a thread-local variable.
1753  if (Var->getTLSKind())
1754  return false;
1755 
1756  // A dllimport variable never acts like a constant.
1757  if (Usage == Expr::EvaluateForCodeGen && Var->hasAttr<DLLImportAttr>())
1758  return false;
1759  }
1760  if (const auto *FD = dyn_cast<const FunctionDecl>(VD)) {
1761  // __declspec(dllimport) must be handled very carefully:
1762  // We must never initialize an expression with the thunk in C++.
1763  // Doing otherwise would allow the same id-expression to yield
1764  // different addresses for the same function in different translation
1765  // units. However, this means that we must dynamically initialize the
1766  // expression with the contents of the import address table at runtime.
1767  //
1768  // The C language has no notion of ODR; furthermore, it has no notion of
1769  // dynamic initialization. This means that we are permitted to
1770  // perform initialization with the address of the thunk.
1771  if (Info.getLangOpts().CPlusPlus && Usage == Expr::EvaluateForCodeGen &&
1772  FD->hasAttr<DLLImportAttr>())
1773  return false;
1774  }
1775  }
1776 
1777  // Allow address constant expressions to be past-the-end pointers. This is
1778  // an extension: the standard requires them to point to an object.
1779  if (!IsReferenceType)
1780  return true;
1781 
1782  // A reference constant expression must refer to an object.
1783  if (!Base) {
1784  // FIXME: diagnostic
1785  Info.CCEDiag(Loc);
1786  return true;
1787  }
1788 
1789  // Does this refer one past the end of some object?
1790  if (!Designator.Invalid && Designator.isOnePastTheEnd()) {
1791  const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
1792  Info.FFDiag(Loc, diag::note_constexpr_past_end, 1)
1793  << !Designator.Entries.empty() << !!VD << VD;
1794  NoteLValueLocation(Info, Base);
1795  }
1796 
1797  return true;
1798 }
1799 
1800 /// Member pointers are constant expressions unless they point to a
1801 /// non-virtual dllimport member function.
1802 static bool CheckMemberPointerConstantExpression(EvalInfo &Info,
1803  SourceLocation Loc,
1804  QualType Type,
1805  const APValue &Value,
1806  Expr::ConstExprUsage Usage) {
1807  const ValueDecl *Member = Value.getMemberPointerDecl();
1808  const auto *FD = dyn_cast_or_null<CXXMethodDecl>(Member);
1809  if (!FD)
1810  return true;
1811  return Usage == Expr::EvaluateForMangling || FD->isVirtual() ||
1812  !FD->hasAttr<DLLImportAttr>();
1813 }
1814 
1815 /// Check that this core constant expression is of literal type, and if not,
1816 /// produce an appropriate diagnostic.
1817 static bool CheckLiteralType(EvalInfo &Info, const Expr *E,
1818  const LValue *This = nullptr) {
1819  if (!E->isRValue() || E->getType()->isLiteralType(Info.Ctx))
1820  return true;
1821 
1822  // C++1y: A constant initializer for an object o [...] may also invoke
1823  // constexpr constructors for o and its subobjects even if those objects
1824  // are of non-literal class types.
1825  //
1826  // C++11 missed this detail for aggregates, so classes like this:
1827  // struct foo_t { union { int i; volatile int j; } u; };
1828  // are not (obviously) initializable like so:
1829  // __attribute__((__require_constant_initialization__))
1830  // static const foo_t x = {{0}};
1831  // because "i" is a subobject with non-literal initialization (due to the
1832  // volatile member of the union). See:
1833  // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1677
1834  // Therefore, we use the C++1y behavior.
1835  if (This && Info.EvaluatingDecl == This->getLValueBase())
1836  return true;
1837 
1838  // Prvalue constant expressions must be of literal types.
1839  if (Info.getLangOpts().CPlusPlus11)
1840  Info.FFDiag(E, diag::note_constexpr_nonliteral)
1841  << E->getType();
1842  else
1843  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
1844  return false;
1845 }
1846 
1847 /// Check that this core constant expression value is a valid value for a
1848 /// constant expression. If not, report an appropriate diagnostic. Does not
1849 /// check that the expression is of literal type.
1850 static bool
1851 CheckConstantExpression(EvalInfo &Info, SourceLocation DiagLoc, QualType Type,
1852  const APValue &Value,
1854  if (Value.isUninit()) {
1855  Info.FFDiag(DiagLoc, diag::note_constexpr_uninitialized)
1856  << true << Type;
1857  return false;
1858  }
1859 
1860  // We allow _Atomic(T) to be initialized from anything that T can be
1861  // initialized from.
1862  if (const AtomicType *AT = Type->getAs<AtomicType>())
1863  Type = AT->getValueType();
1864 
1865  // Core issue 1454: For a literal constant expression of array or class type,
1866  // each subobject of its value shall have been initialized by a constant
1867  // expression.
1868  if (Value.isArray()) {
1869  QualType EltTy = Type->castAsArrayTypeUnsafe()->getElementType();
1870  for (unsigned I = 0, N = Value.getArrayInitializedElts(); I != N; ++I) {
1871  if (!CheckConstantExpression(Info, DiagLoc, EltTy,
1872  Value.getArrayInitializedElt(I), Usage))
1873  return false;
1874  }
1875  if (!Value.hasArrayFiller())
1876  return true;
1877  return CheckConstantExpression(Info, DiagLoc, EltTy, Value.getArrayFiller(),
1878  Usage);
1879  }
1880  if (Value.isUnion() && Value.getUnionField()) {
1881  return CheckConstantExpression(Info, DiagLoc,
1882  Value.getUnionField()->getType(),
1883  Value.getUnionValue(), Usage);
1884  }
1885  if (Value.isStruct()) {
1886  RecordDecl *RD = Type->castAs<RecordType>()->getDecl();
1887  if (const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD)) {
1888  unsigned BaseIndex = 0;
1889  for (const CXXBaseSpecifier &BS : CD->bases()) {
1890  if (!CheckConstantExpression(Info, DiagLoc, BS.getType(),
1891  Value.getStructBase(BaseIndex), Usage))
1892  return false;
1893  ++BaseIndex;
1894  }
1895  }
1896  for (const auto *I : RD->fields()) {
1897  if (I->isUnnamedBitfield())
1898  continue;
1899 
1900  if (!CheckConstantExpression(Info, DiagLoc, I->getType(),
1901  Value.getStructField(I->getFieldIndex()),
1902  Usage))
1903  return false;
1904  }
1905  }
1906 
1907  if (Value.isLValue()) {
1908  LValue LVal;
1909  LVal.setFrom(Info.Ctx, Value);
1910  return CheckLValueConstantExpression(Info, DiagLoc, Type, LVal, Usage);
1911  }
1912 
1913  if (Value.isMemberPointer())
1914  return CheckMemberPointerConstantExpression(Info, DiagLoc, Type, Value, Usage);
1915 
1916  // Everything else is fine.
1917  return true;
1918 }
1919 
1920 static const ValueDecl *GetLValueBaseDecl(const LValue &LVal) {
1921  return LVal.Base.dyn_cast<const ValueDecl*>();
1922 }
1923 
1924 static bool IsLiteralLValue(const LValue &Value) {
1925  if (Value.getLValueCallIndex())
1926  return false;
1927  const Expr *E = Value.Base.dyn_cast<const Expr*>();
1928  return E && !isa<MaterializeTemporaryExpr>(E);
1929 }
1930 
1931 static bool IsWeakLValue(const LValue &Value) {
1932  const ValueDecl *Decl = GetLValueBaseDecl(Value);
1933  return Decl && Decl->isWeak();
1934 }
1935 
1936 static bool isZeroSized(const LValue &Value) {
1937  const ValueDecl *Decl = GetLValueBaseDecl(Value);
1938  if (Decl && isa<VarDecl>(Decl)) {
1939  QualType Ty = Decl->getType();
1940  if (Ty->isArrayType())
1941  return Ty->isIncompleteType() ||
1942  Decl->getASTContext().getTypeSize(Ty) == 0;
1943  }
1944  return false;
1945 }
1946 
1947 static bool EvalPointerValueAsBool(const APValue &Value, bool &Result) {
1948  // A null base expression indicates a null pointer. These are always
1949  // evaluatable, and they are false unless the offset is zero.
1950  if (!Value.getLValueBase()) {
1951  Result = !Value.getLValueOffset().isZero();
1952  return true;
1953  }
1954 
1955  // We have a non-null base. These are generally known to be true, but if it's
1956  // a weak declaration it can be null at runtime.
1957  Result = true;
1958  const ValueDecl *Decl = Value.getLValueBase().dyn_cast<const ValueDecl*>();
1959  return !Decl || !Decl->isWeak();
1960 }
1961 
1962 static bool HandleConversionToBool(const APValue &Val, bool &Result) {
1963  switch (Val.getKind()) {
1965  return false;
1966  case APValue::Int:
1967  Result = Val.getInt().getBoolValue();
1968  return true;
1969  case APValue::Float:
1970  Result = !Val.getFloat().isZero();
1971  return true;
1972  case APValue::ComplexInt:
1973  Result = Val.getComplexIntReal().getBoolValue() ||
1974  Val.getComplexIntImag().getBoolValue();
1975  return true;
1976  case APValue::ComplexFloat:
1977  Result = !Val.getComplexFloatReal().isZero() ||
1978  !Val.getComplexFloatImag().isZero();
1979  return true;
1980  case APValue::LValue:
1981  return EvalPointerValueAsBool(Val, Result);
1983  Result = Val.getMemberPointerDecl();
1984  return true;
1985  case APValue::Vector:
1986  case APValue::Array:
1987  case APValue::Struct:
1988  case APValue::Union:
1990  return false;
1991  }
1992 
1993  llvm_unreachable("unknown APValue kind");
1994 }
1995 
1996 static bool EvaluateAsBooleanCondition(const Expr *E, bool &Result,
1997  EvalInfo &Info) {
1998  assert(E->isRValue() && "missing lvalue-to-rvalue conv in bool condition");
1999  APValue Val;
2000  if (!Evaluate(Val, Info, E))
2001  return false;
2002  return HandleConversionToBool(Val, Result);
2003 }
2004 
2005 template<typename T>
2006 static bool HandleOverflow(EvalInfo &Info, const Expr *E,
2007  const T &SrcValue, QualType DestType) {
2008  Info.CCEDiag(E, diag::note_constexpr_overflow)
2009  << SrcValue << DestType;
2010  return Info.noteUndefinedBehavior();
2011 }
2012 
2013 static bool HandleFloatToIntCast(EvalInfo &Info, const Expr *E,
2014  QualType SrcType, const APFloat &Value,
2015  QualType DestType, APSInt &Result) {
2016  unsigned DestWidth = Info.Ctx.getIntWidth(DestType);
2017  // Determine whether we are converting to unsigned or signed.
2018  bool DestSigned = DestType->isSignedIntegerOrEnumerationType();
2019 
2020  Result = APSInt(DestWidth, !DestSigned);
2021  bool ignored;
2022  if (Value.convertToInteger(Result, llvm::APFloat::rmTowardZero, &ignored)
2023  & APFloat::opInvalidOp)
2024  return HandleOverflow(Info, E, Value, DestType);
2025  return true;
2026 }
2027 
2028 static bool HandleFloatToFloatCast(EvalInfo &Info, const Expr *E,
2029  QualType SrcType, QualType DestType,
2030  APFloat &Result) {
2031  APFloat Value = Result;
2032  bool ignored;
2033  if (Result.convert(Info.Ctx.getFloatTypeSemantics(DestType),
2034  APFloat::rmNearestTiesToEven, &ignored)
2035  & APFloat::opOverflow)
2036  return HandleOverflow(Info, E, Value, DestType);
2037  return true;
2038 }
2039 
2040 static APSInt HandleIntToIntCast(EvalInfo &Info, const Expr *E,
2041  QualType DestType, QualType SrcType,
2042  const APSInt &Value) {
2043  unsigned DestWidth = Info.Ctx.getIntWidth(DestType);
2044  APSInt Result = Value;
2045  // Figure out if this is a truncate, extend or noop cast.
2046  // If the input is signed, do a sign extend, noop, or truncate.
2047  Result = Result.extOrTrunc(DestWidth);
2048  Result.setIsUnsigned(DestType->isUnsignedIntegerOrEnumerationType());
2049  return Result;
2050 }
2051 
2052 static bool HandleIntToFloatCast(EvalInfo &Info, const Expr *E,
2053  QualType SrcType, const APSInt &Value,
2054  QualType DestType, APFloat &Result) {
2055  Result = APFloat(Info.Ctx.getFloatTypeSemantics(DestType), 1);
2056  if (Result.convertFromAPInt(Value, Value.isSigned(),
2057  APFloat::rmNearestTiesToEven)
2058  & APFloat::opOverflow)
2059  return HandleOverflow(Info, E, Value, DestType);
2060  return true;
2061 }
2062 
2063 static bool truncateBitfieldValue(EvalInfo &Info, const Expr *E,
2064  APValue &Value, const FieldDecl *FD) {
2065  assert(FD->isBitField() && "truncateBitfieldValue on non-bitfield");
2066 
2067  if (!Value.isInt()) {
2068  // Trying to store a pointer-cast-to-integer into a bitfield.
2069  // FIXME: In this case, we should provide the diagnostic for casting
2070  // a pointer to an integer.
2071  assert(Value.isLValue() && "integral value neither int nor lvalue?");
2072  Info.FFDiag(E);
2073  return false;
2074  }
2075 
2076  APSInt &Int = Value.getInt();
2077  unsigned OldBitWidth = Int.getBitWidth();
2078  unsigned NewBitWidth = FD->getBitWidthValue(Info.Ctx);
2079  if (NewBitWidth < OldBitWidth)
2080  Int = Int.trunc(NewBitWidth).extend(OldBitWidth);
2081  return true;
2082 }
2083 
2084 static bool EvalAndBitcastToAPInt(EvalInfo &Info, const Expr *E,
2085  llvm::APInt &Res) {
2086  APValue SVal;
2087  if (!Evaluate(SVal, Info, E))
2088  return false;
2089  if (SVal.isInt()) {
2090  Res = SVal.getInt();
2091  return true;
2092  }
2093  if (SVal.isFloat()) {
2094  Res = SVal.getFloat().bitcastToAPInt();
2095  return true;
2096  }
2097  if (SVal.isVector()) {
2098  QualType VecTy = E->getType();
2099  unsigned VecSize = Info.Ctx.getTypeSize(VecTy);
2100  QualType EltTy = VecTy->castAs<VectorType>()->getElementType();
2101  unsigned EltSize = Info.Ctx.getTypeSize(EltTy);
2102  bool BigEndian = Info.Ctx.getTargetInfo().isBigEndian();
2103  Res = llvm::APInt::getNullValue(VecSize);
2104  for (unsigned i = 0; i < SVal.getVectorLength(); i++) {
2105  APValue &Elt = SVal.getVectorElt(i);
2106  llvm::APInt EltAsInt;
2107  if (Elt.isInt()) {
2108  EltAsInt = Elt.getInt();
2109  } else if (Elt.isFloat()) {
2110  EltAsInt = Elt.getFloat().bitcastToAPInt();
2111  } else {
2112  // Don't try to handle vectors of anything other than int or float
2113  // (not sure if it's possible to hit this case).
2114  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2115  return false;
2116  }
2117  unsigned BaseEltSize = EltAsInt.getBitWidth();
2118  if (BigEndian)
2119  Res |= EltAsInt.zextOrTrunc(VecSize).rotr(i*EltSize+BaseEltSize);
2120  else
2121  Res |= EltAsInt.zextOrTrunc(VecSize).rotl(i*EltSize);
2122  }
2123  return true;
2124  }
2125  // Give up if the input isn't an int, float, or vector. For example, we
2126  // reject "(v4i16)(intptr_t)&a".
2127  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2128  return false;
2129 }
2130 
2131 /// Perform the given integer operation, which is known to need at most BitWidth
2132 /// bits, and check for overflow in the original type (if that type was not an
2133 /// unsigned type).
2134 template<typename Operation>
2135 static bool CheckedIntArithmetic(EvalInfo &Info, const Expr *E,
2136  const APSInt &LHS, const APSInt &RHS,
2137  unsigned BitWidth, Operation Op,
2138  APSInt &Result) {
2139  if (LHS.isUnsigned()) {
2140  Result = Op(LHS, RHS);
2141  return true;
2142  }
2143 
2144  APSInt Value(Op(LHS.extend(BitWidth), RHS.extend(BitWidth)), false);
2145  Result = Value.trunc(LHS.getBitWidth());
2146  if (Result.extend(BitWidth) != Value) {
2147  if (Info.checkingForOverflow())
2148  Info.Ctx.getDiagnostics().Report(E->getExprLoc(),
2149  diag::warn_integer_constant_overflow)
2150  << Result.toString(10) << E->getType();
2151  else
2152  return HandleOverflow(Info, E, Value, E->getType());
2153  }
2154  return true;
2155 }
2156 
2157 /// Perform the given binary integer operation.
2158 static bool handleIntIntBinOp(EvalInfo &Info, const Expr *E, const APSInt &LHS,
2159  BinaryOperatorKind Opcode, APSInt RHS,
2160  APSInt &Result) {
2161  switch (Opcode) {
2162  default:
2163  Info.FFDiag(E);
2164  return false;
2165  case BO_Mul:
2166  return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() * 2,
2167  std::multiplies<APSInt>(), Result);
2168  case BO_Add:
2169  return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() + 1,
2170  std::plus<APSInt>(), Result);
2171  case BO_Sub:
2172  return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() + 1,
2173  std::minus<APSInt>(), Result);
2174  case BO_And: Result = LHS & RHS; return true;
2175  case BO_Xor: Result = LHS ^ RHS; return true;
2176  case BO_Or: Result = LHS | RHS; return true;
2177  case BO_Div:
2178  case BO_Rem:
2179  if (RHS == 0) {
2180  Info.FFDiag(E, diag::note_expr_divide_by_zero);
2181  return false;
2182  }
2183  Result = (Opcode == BO_Rem ? LHS % RHS : LHS / RHS);
2184  // Check for overflow case: INT_MIN / -1 or INT_MIN % -1. APSInt supports
2185  // this operation and gives the two's complement result.
2186  if (RHS.isNegative() && RHS.isAllOnesValue() &&
2187  LHS.isSigned() && LHS.isMinSignedValue())
2188  return HandleOverflow(Info, E, -LHS.extend(LHS.getBitWidth() + 1),
2189  E->getType());
2190  return true;
2191  case BO_Shl: {
2192  if (Info.getLangOpts().OpenCL)
2193  // OpenCL 6.3j: shift values are effectively % word size of LHS.
2194  RHS &= APSInt(llvm::APInt(RHS.getBitWidth(),
2195  static_cast<uint64_t>(LHS.getBitWidth() - 1)),
2196  RHS.isUnsigned());
2197  else if (RHS.isSigned() && RHS.isNegative()) {
2198  // During constant-folding, a negative shift is an opposite shift. Such
2199  // a shift is not a constant expression.
2200  Info.CCEDiag(E, diag::note_constexpr_negative_shift) << RHS;
2201  RHS = -RHS;
2202  goto shift_right;
2203  }
2204  shift_left:
2205  // C++11 [expr.shift]p1: Shift width must be less than the bit width of
2206  // the shifted type.
2207  unsigned SA = (unsigned) RHS.getLimitedValue(LHS.getBitWidth()-1);
2208  if (SA != RHS) {
2209  Info.CCEDiag(E, diag::note_constexpr_large_shift)
2210  << RHS << E->getType() << LHS.getBitWidth();
2211  } else if (LHS.isSigned()) {
2212  // C++11 [expr.shift]p2: A signed left shift must have a non-negative
2213  // operand, and must not overflow the corresponding unsigned type.
2214  if (LHS.isNegative())
2215  Info.CCEDiag(E, diag::note_constexpr_lshift_of_negative) << LHS;
2216  else if (LHS.countLeadingZeros() < SA)
2217  Info.CCEDiag(E, diag::note_constexpr_lshift_discards);
2218  }
2219  Result = LHS << SA;
2220  return true;
2221  }
2222  case BO_Shr: {
2223  if (Info.getLangOpts().OpenCL)
2224  // OpenCL 6.3j: shift values are effectively % word size of LHS.
2225  RHS &= APSInt(llvm::APInt(RHS.getBitWidth(),
2226  static_cast<uint64_t>(LHS.getBitWidth() - 1)),
2227  RHS.isUnsigned());
2228  else if (RHS.isSigned() && RHS.isNegative()) {
2229  // During constant-folding, a negative shift is an opposite shift. Such a
2230  // shift is not a constant expression.
2231  Info.CCEDiag(E, diag::note_constexpr_negative_shift) << RHS;
2232  RHS = -RHS;
2233  goto shift_left;
2234  }
2235  shift_right:
2236  // C++11 [expr.shift]p1: Shift width must be less than the bit width of the
2237  // shifted type.
2238  unsigned SA = (unsigned) RHS.getLimitedValue(LHS.getBitWidth()-1);
2239  if (SA != RHS)
2240  Info.CCEDiag(E, diag::note_constexpr_large_shift)
2241  << RHS << E->getType() << LHS.getBitWidth();
2242  Result = LHS >> SA;
2243  return true;
2244  }
2245 
2246  case BO_LT: Result = LHS < RHS; return true;
2247  case BO_GT: Result = LHS > RHS; return true;
2248  case BO_LE: Result = LHS <= RHS; return true;
2249  case BO_GE: Result = LHS >= RHS; return true;
2250  case BO_EQ: Result = LHS == RHS; return true;
2251  case BO_NE: Result = LHS != RHS; return true;
2252  case BO_Cmp:
2253  llvm_unreachable("BO_Cmp should be handled elsewhere");
2254  }
2255 }
2256 
2257 /// Perform the given binary floating-point operation, in-place, on LHS.
2258 static bool handleFloatFloatBinOp(EvalInfo &Info, const Expr *E,
2259  APFloat &LHS, BinaryOperatorKind Opcode,
2260  const APFloat &RHS) {
2261  switch (Opcode) {
2262  default:
2263  Info.FFDiag(E);
2264  return false;
2265  case BO_Mul:
2266  LHS.multiply(RHS, APFloat::rmNearestTiesToEven);
2267  break;
2268  case BO_Add:
2269  LHS.add(RHS, APFloat::rmNearestTiesToEven);
2270  break;
2271  case BO_Sub:
2272  LHS.subtract(RHS, APFloat::rmNearestTiesToEven);
2273  break;
2274  case BO_Div:
2275  LHS.divide(RHS, APFloat::rmNearestTiesToEven);
2276  break;
2277  }
2278 
2279  if (LHS.isInfinity() || LHS.isNaN()) {
2280  Info.CCEDiag(E, diag::note_constexpr_float_arithmetic) << LHS.isNaN();
2281  return Info.noteUndefinedBehavior();
2282  }
2283  return true;
2284 }
2285 
2286 /// Cast an lvalue referring to a base subobject to a derived class, by
2287 /// truncating the lvalue's path to the given length.
2288 static bool CastToDerivedClass(EvalInfo &Info, const Expr *E, LValue &Result,
2289  const RecordDecl *TruncatedType,
2290  unsigned TruncatedElements) {
2291  SubobjectDesignator &D = Result.Designator;
2292 
2293  // Check we actually point to a derived class object.
2294  if (TruncatedElements == D.Entries.size())
2295  return true;
2296  assert(TruncatedElements >= D.MostDerivedPathLength &&
2297  "not casting to a derived class");
2298  if (!Result.checkSubobject(Info, E, CSK_Derived))
2299  return false;
2300 
2301  // Truncate the path to the subobject, and remove any derived-to-base offsets.
2302  const RecordDecl *RD = TruncatedType;
2303  for (unsigned I = TruncatedElements, N = D.Entries.size(); I != N; ++I) {
2304  if (RD->isInvalidDecl()) return false;
2305  const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
2306  const CXXRecordDecl *Base = getAsBaseClass(D.Entries[I]);
2307  if (isVirtualBaseClass(D.Entries[I]))
2308  Result.Offset -= Layout.getVBaseClassOffset(Base);
2309  else
2310  Result.Offset -= Layout.getBaseClassOffset(Base);
2311  RD = Base;
2312  }
2313  D.Entries.resize(TruncatedElements);
2314  return true;
2315 }
2316 
2317 static bool HandleLValueDirectBase(EvalInfo &Info, const Expr *E, LValue &Obj,
2318  const CXXRecordDecl *Derived,
2319  const CXXRecordDecl *Base,
2320  const ASTRecordLayout *RL = nullptr) {
2321  if (!RL) {
2322  if (Derived->isInvalidDecl()) return false;
2323  RL = &Info.Ctx.getASTRecordLayout(Derived);
2324  }
2325 
2326  Obj.getLValueOffset() += RL->getBaseClassOffset(Base);
2327  Obj.addDecl(Info, E, Base, /*Virtual*/ false);
2328  return true;
2329 }
2330 
2331 static bool HandleLValueBase(EvalInfo &Info, const Expr *E, LValue &Obj,
2332  const CXXRecordDecl *DerivedDecl,
2333  const CXXBaseSpecifier *Base) {
2334  const CXXRecordDecl *BaseDecl = Base->getType()->getAsCXXRecordDecl();
2335 
2336  if (!Base->isVirtual())
2337  return HandleLValueDirectBase(Info, E, Obj, DerivedDecl, BaseDecl);
2338 
2339  SubobjectDesignator &D = Obj.Designator;
2340  if (D.Invalid)
2341  return false;
2342 
2343  // Extract most-derived object and corresponding type.
2344  DerivedDecl = D.MostDerivedType->getAsCXXRecordDecl();
2345  if (!CastToDerivedClass(Info, E, Obj, DerivedDecl, D.MostDerivedPathLength))
2346  return false;
2347 
2348  // Find the virtual base class.
2349  if (DerivedDecl->isInvalidDecl()) return false;
2350  const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(DerivedDecl);
2351  Obj.getLValueOffset() += Layout.getVBaseClassOffset(BaseDecl);
2352  Obj.addDecl(Info, E, BaseDecl, /*Virtual*/ true);
2353  return true;
2354 }
2355 
2356 static bool HandleLValueBasePath(EvalInfo &Info, const CastExpr *E,
2357  QualType Type, LValue &Result) {
2358  for (CastExpr::path_const_iterator PathI = E->path_begin(),
2359  PathE = E->path_end();
2360  PathI != PathE; ++PathI) {
2361  if (!HandleLValueBase(Info, E, Result, Type->getAsCXXRecordDecl(),
2362  *PathI))
2363  return false;
2364  Type = (*PathI)->getType();
2365  }
2366  return true;
2367 }
2368 
2369 /// Update LVal to refer to the given field, which must be a member of the type
2370 /// currently described by LVal.
2371 static bool HandleLValueMember(EvalInfo &Info, const Expr *E, LValue &LVal,
2372  const FieldDecl *FD,
2373  const ASTRecordLayout *RL = nullptr) {
2374  if (!RL) {
2375  if (FD->getParent()->isInvalidDecl()) return false;
2376  RL = &Info.Ctx.getASTRecordLayout(FD->getParent());
2377  }
2378 
2379  unsigned I = FD->getFieldIndex();
2380  LVal.adjustOffset(Info.Ctx.toCharUnitsFromBits(RL->getFieldOffset(I)));
2381  LVal.addDecl(Info, E, FD);
2382  return true;
2383 }
2384 
2385 /// Update LVal to refer to the given indirect field.
2386 static bool HandleLValueIndirectMember(EvalInfo &Info, const Expr *E,
2387  LValue &LVal,
2388  const IndirectFieldDecl *IFD) {
2389  for (const auto *C : IFD->chain())
2390  if (!HandleLValueMember(Info, E, LVal, cast<FieldDecl>(C)))
2391  return false;
2392  return true;
2393 }
2394 
2395 /// Get the size of the given type in char units.
2396 static bool HandleSizeof(EvalInfo &Info, SourceLocation Loc,
2397  QualType Type, CharUnits &Size) {
2398  // sizeof(void), __alignof__(void), sizeof(function) = 1 as a gcc
2399  // extension.
2400  if (Type->isVoidType() || Type->isFunctionType()) {
2401  Size = CharUnits::One();
2402  return true;
2403  }
2404 
2405  if (Type->isDependentType()) {
2406  Info.FFDiag(Loc);
2407  return false;
2408  }
2409 
2410  if (!Type->isConstantSizeType()) {
2411  // sizeof(vla) is not a constantexpr: C99 6.5.3.4p2.
2412  // FIXME: Better diagnostic.
2413  Info.FFDiag(Loc);
2414  return false;
2415  }
2416 
2417  Size = Info.Ctx.getTypeSizeInChars(Type);
2418  return true;
2419 }
2420 
2421 /// Update a pointer value to model pointer arithmetic.
2422 /// \param Info - Information about the ongoing evaluation.
2423 /// \param E - The expression being evaluated, for diagnostic purposes.
2424 /// \param LVal - The pointer value to be updated.
2425 /// \param EltTy - The pointee type represented by LVal.
2426 /// \param Adjustment - The adjustment, in objects of type EltTy, to add.
2427 static bool HandleLValueArrayAdjustment(EvalInfo &Info, const Expr *E,
2428  LValue &LVal, QualType EltTy,
2429  APSInt Adjustment) {
2430  CharUnits SizeOfPointee;
2431  if (!HandleSizeof(Info, E->getExprLoc(), EltTy, SizeOfPointee))
2432  return false;
2433 
2434  LVal.adjustOffsetAndIndex(Info, E, Adjustment, SizeOfPointee);
2435  return true;
2436 }
2437 
2438 static bool HandleLValueArrayAdjustment(EvalInfo &Info, const Expr *E,
2439  LValue &LVal, QualType EltTy,
2440  int64_t Adjustment) {
2441  return HandleLValueArrayAdjustment(Info, E, LVal, EltTy,
2442  APSInt::get(Adjustment));
2443 }
2444 
2445 /// Update an lvalue to refer to a component of a complex number.
2446 /// \param Info - Information about the ongoing evaluation.
2447 /// \param LVal - The lvalue to be updated.
2448 /// \param EltTy - The complex number's component type.
2449 /// \param Imag - False for the real component, true for the imaginary.
2450 static bool HandleLValueComplexElement(EvalInfo &Info, const Expr *E,
2451  LValue &LVal, QualType EltTy,
2452  bool Imag) {
2453  if (Imag) {
2454  CharUnits SizeOfComponent;
2455  if (!HandleSizeof(Info, E->getExprLoc(), EltTy, SizeOfComponent))
2456  return false;
2457  LVal.Offset += SizeOfComponent;
2458  }
2459  LVal.addComplex(Info, E, EltTy, Imag);
2460  return true;
2461 }
2462 
2463 static bool handleLValueToRValueConversion(EvalInfo &Info, const Expr *Conv,
2464  QualType Type, const LValue &LVal,
2465  APValue &RVal);
2466 
2467 /// Try to evaluate the initializer for a variable declaration.
2468 ///
2469 /// \param Info Information about the ongoing evaluation.
2470 /// \param E An expression to be used when printing diagnostics.
2471 /// \param VD The variable whose initializer should be obtained.
2472 /// \param Frame The frame in which the variable was created. Must be null
2473 /// if this variable is not local to the evaluation.
2474 /// \param Result Filled in with a pointer to the value of the variable.
2475 static bool evaluateVarDeclInit(EvalInfo &Info, const Expr *E,
2476  const VarDecl *VD, CallStackFrame *Frame,
2477  APValue *&Result, const LValue *LVal) {
2478 
2479  // If this is a parameter to an active constexpr function call, perform
2480  // argument substitution.
2481  if (const ParmVarDecl *PVD = dyn_cast<ParmVarDecl>(VD)) {
2482  // Assume arguments of a potential constant expression are unknown
2483  // constant expressions.
2484  if (Info.checkingPotentialConstantExpression())
2485  return false;
2486  if (!Frame || !Frame->Arguments) {
2487  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2488  return false;
2489  }
2490  Result = &Frame->Arguments[PVD->getFunctionScopeIndex()];
2491  return true;
2492  }
2493 
2494  // If this is a local variable, dig out its value.
2495  if (Frame) {
2496  Result = LVal ? Frame->getTemporary(VD, LVal->getLValueVersion())
2497  : Frame->getCurrentTemporary(VD);
2498  if (!Result) {
2499  // Assume variables referenced within a lambda's call operator that were
2500  // not declared within the call operator are captures and during checking
2501  // of a potential constant expression, assume they are unknown constant
2502  // expressions.
2503  assert(isLambdaCallOperator(Frame->Callee) &&
2504  (VD->getDeclContext() != Frame->Callee || VD->isInitCapture()) &&
2505  "missing value for local variable");
2506  if (Info.checkingPotentialConstantExpression())
2507  return false;
2508  // FIXME: implement capture evaluation during constant expr evaluation.
2509  Info.FFDiag(E->getLocStart(),
2510  diag::note_unimplemented_constexpr_lambda_feature_ast)
2511  << "captures not currently allowed";
2512  return false;
2513  }
2514  return true;
2515  }
2516 
2517  // Dig out the initializer, and use the declaration which it's attached to.
2518  const Expr *Init = VD->getAnyInitializer(VD);
2519  if (!Init || Init->isValueDependent()) {
2520  // If we're checking a potential constant expression, the variable could be
2521  // initialized later.
2522  if (!Info.checkingPotentialConstantExpression())
2523  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2524  return false;
2525  }
2526 
2527  // If we're currently evaluating the initializer of this declaration, use that
2528  // in-flight value.
2529  if (Info.EvaluatingDecl.dyn_cast<const ValueDecl*>() == VD) {
2530  Result = Info.EvaluatingDeclValue;
2531  return true;
2532  }
2533 
2534  // Never evaluate the initializer of a weak variable. We can't be sure that
2535  // this is the definition which will be used.
2536  if (VD->isWeak()) {
2537  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2538  return false;
2539  }
2540 
2541  // Check that we can fold the initializer. In C++, we will have already done
2542  // this in the cases where it matters for conformance.
2544  if (!VD->evaluateValue(Notes)) {
2545  Info.FFDiag(E, diag::note_constexpr_var_init_non_constant,
2546  Notes.size() + 1) << VD;
2547  Info.Note(VD->getLocation(), diag::note_declared_at);
2548  Info.addNotes(Notes);
2549  return false;
2550  } else if (!VD->checkInitIsICE()) {
2551  Info.CCEDiag(E, diag::note_constexpr_var_init_non_constant,
2552  Notes.size() + 1) << VD;
2553  Info.Note(VD->getLocation(), diag::note_declared_at);
2554  Info.addNotes(Notes);
2555  }
2556 
2557  Result = VD->getEvaluatedValue();
2558  return true;
2559 }
2560 
2562  Qualifiers Quals = T.getQualifiers();
2563  return Quals.hasConst() && !Quals.hasVolatile();
2564 }
2565 
2566 /// Get the base index of the given base class within an APValue representing
2567 /// the given derived class.
2568 static unsigned getBaseIndex(const CXXRecordDecl *Derived,
2569  const CXXRecordDecl *Base) {
2570  Base = Base->getCanonicalDecl();
2571  unsigned Index = 0;
2573  E = Derived->bases_end(); I != E; ++I, ++Index) {
2574  if (I->getType()->getAsCXXRecordDecl()->getCanonicalDecl() == Base)
2575  return Index;
2576  }
2577 
2578  llvm_unreachable("base class missing from derived class's bases list");
2579 }
2580 
2581 /// Extract the value of a character from a string literal.
2582 static APSInt extractStringLiteralCharacter(EvalInfo &Info, const Expr *Lit,
2583  uint64_t Index) {
2584  // FIXME: Support MakeStringConstant
2585  if (const auto *ObjCEnc = dyn_cast<ObjCEncodeExpr>(Lit)) {
2586  std::string Str;
2587  Info.Ctx.getObjCEncodingForType(ObjCEnc->getEncodedType(), Str);
2588  assert(Index <= Str.size() && "Index too large");
2589  return APSInt::getUnsigned(Str.c_str()[Index]);
2590  }
2591 
2592  if (auto PE = dyn_cast<PredefinedExpr>(Lit))
2593  Lit = PE->getFunctionName();
2594  const StringLiteral *S = cast<StringLiteral>(Lit);
2595  const ConstantArrayType *CAT =
2596  Info.Ctx.getAsConstantArrayType(S->getType());
2597  assert(CAT && "string literal isn't an array");
2598  QualType CharType = CAT->getElementType();
2599  assert(CharType->isIntegerType() && "unexpected character type");
2600 
2601  APSInt Value(S->getCharByteWidth() * Info.Ctx.getCharWidth(),
2602  CharType->isUnsignedIntegerType());
2603  if (Index < S->getLength())
2604  Value = S->getCodeUnit(Index);
2605  return Value;
2606 }
2607 
2608 // Expand a string literal into an array of characters.
2609 static void expandStringLiteral(EvalInfo &Info, const Expr *Lit,
2610  APValue &Result) {
2611  const StringLiteral *S = cast<StringLiteral>(Lit);
2612  const ConstantArrayType *CAT =
2613  Info.Ctx.getAsConstantArrayType(S->getType());
2614  assert(CAT && "string literal isn't an array");
2615  QualType CharType = CAT->getElementType();
2616  assert(CharType->isIntegerType() && "unexpected character type");
2617 
2618  unsigned Elts = CAT->getSize().getZExtValue();
2619  Result = APValue(APValue::UninitArray(),
2620  std::min(S->getLength(), Elts), Elts);
2621  APSInt Value(S->getCharByteWidth() * Info.Ctx.getCharWidth(),
2622  CharType->isUnsignedIntegerType());
2623  if (Result.hasArrayFiller())
2624  Result.getArrayFiller() = APValue(Value);
2625  for (unsigned I = 0, N = Result.getArrayInitializedElts(); I != N; ++I) {
2626  Value = S->getCodeUnit(I);
2627  Result.getArrayInitializedElt(I) = APValue(Value);
2628  }
2629 }
2630 
2631 // Expand an array so that it has more than Index filled elements.
2632 static void expandArray(APValue &Array, unsigned Index) {
2633  unsigned Size = Array.getArraySize();
2634  assert(Index < Size);
2635 
2636  // Always at least double the number of elements for which we store a value.
2637  unsigned OldElts = Array.getArrayInitializedElts();
2638  unsigned NewElts = std::max(Index+1, OldElts * 2);
2639  NewElts = std::min(Size, std::max(NewElts, 8u));
2640 
2641  // Copy the data across.
2642  APValue NewValue(APValue::UninitArray(), NewElts, Size);
2643  for (unsigned I = 0; I != OldElts; ++I)
2644  NewValue.getArrayInitializedElt(I).swap(Array.getArrayInitializedElt(I));
2645  for (unsigned I = OldElts; I != NewElts; ++I)
2646  NewValue.getArrayInitializedElt(I) = Array.getArrayFiller();
2647  if (NewValue.hasArrayFiller())
2648  NewValue.getArrayFiller() = Array.getArrayFiller();
2649  Array.swap(NewValue);
2650 }
2651 
2652 /// Determine whether a type would actually be read by an lvalue-to-rvalue
2653 /// conversion. If it's of class type, we may assume that the copy operation
2654 /// is trivial. Note that this is never true for a union type with fields
2655 /// (because the copy always "reads" the active member) and always true for
2656 /// a non-class type.
2659  if (!RD || (RD->isUnion() && !RD->field_empty()))
2660  return true;
2661  if (RD->isEmpty())
2662  return false;
2663 
2664  for (auto *Field : RD->fields())
2665  if (isReadByLvalueToRvalueConversion(Field->getType()))
2666  return true;
2667 
2668  for (auto &BaseSpec : RD->bases())
2669  if (isReadByLvalueToRvalueConversion(BaseSpec.getType()))
2670  return true;
2671 
2672  return false;
2673 }
2674 
2675 /// Diagnose an attempt to read from any unreadable field within the specified
2676 /// type, which might be a class type.
2677 static bool diagnoseUnreadableFields(EvalInfo &Info, const Expr *E,
2678  QualType T) {
2680  if (!RD)
2681  return false;
2682 
2683  if (!RD->hasMutableFields())
2684  return false;
2685 
2686  for (auto *Field : RD->fields()) {
2687  // If we're actually going to read this field in some way, then it can't
2688  // be mutable. If we're in a union, then assigning to a mutable field
2689  // (even an empty one) can change the active member, so that's not OK.
2690  // FIXME: Add core issue number for the union case.
2691  if (Field->isMutable() &&
2692  (RD->isUnion() || isReadByLvalueToRvalueConversion(Field->getType()))) {
2693  Info.FFDiag(E, diag::note_constexpr_ltor_mutable, 1) << Field;
2694  Info.Note(Field->getLocation(), diag::note_declared_at);
2695  return true;
2696  }
2697 
2698  if (diagnoseUnreadableFields(Info, E, Field->getType()))
2699  return true;
2700  }
2701 
2702  for (auto &BaseSpec : RD->bases())
2703  if (diagnoseUnreadableFields(Info, E, BaseSpec.getType()))
2704  return true;
2705 
2706  // All mutable fields were empty, and thus not actually read.
2707  return false;
2708 }
2709 
2710 /// Kinds of access we can perform on an object, for diagnostics.
2716 };
2717 
2718 namespace {
2719 /// A handle to a complete object (an object that is not a subobject of
2720 /// another object).
2721 struct CompleteObject {
2722  /// The value of the complete object.
2723  APValue *Value;
2724  /// The type of the complete object.
2725  QualType Type;
2726  bool LifetimeStartedInEvaluation;
2727 
2728  CompleteObject() : Value(nullptr) {}
2729  CompleteObject(APValue *Value, QualType Type,
2730  bool LifetimeStartedInEvaluation)
2731  : Value(Value), Type(Type),
2732  LifetimeStartedInEvaluation(LifetimeStartedInEvaluation) {
2733  assert(Value && "missing value for complete object");
2734  }
2735 
2736  explicit operator bool() const { return Value; }
2737 };
2738 } // end anonymous namespace
2739 
2740 /// Find the designated sub-object of an rvalue.
2741 template<typename SubobjectHandler>
2742 typename SubobjectHandler::result_type
2743 findSubobject(EvalInfo &Info, const Expr *E, const CompleteObject &Obj,
2744  const SubobjectDesignator &Sub, SubobjectHandler &handler) {
2745  if (Sub.Invalid)
2746  // A diagnostic will have already been produced.
2747  return handler.failed();
2748  if (Sub.isOnePastTheEnd() || Sub.isMostDerivedAnUnsizedArray()) {
2749  if (Info.getLangOpts().CPlusPlus11)
2750  Info.FFDiag(E, Sub.isOnePastTheEnd()
2751  ? diag::note_constexpr_access_past_end
2752  : diag::note_constexpr_access_unsized_array)
2753  << handler.AccessKind;
2754  else
2755  Info.FFDiag(E);
2756  return handler.failed();
2757  }
2758 
2759  APValue *O = Obj.Value;
2760  QualType ObjType = Obj.Type;
2761  const FieldDecl *LastField = nullptr;
2762  const bool MayReadMutableMembers =
2763  Obj.LifetimeStartedInEvaluation && Info.getLangOpts().CPlusPlus14;
2764 
2765  // Walk the designator's path to find the subobject.
2766  for (unsigned I = 0, N = Sub.Entries.size(); /**/; ++I) {
2767  if (O->isUninit()) {
2768  if (!Info.checkingPotentialConstantExpression())
2769  Info.FFDiag(E, diag::note_constexpr_access_uninit) << handler.AccessKind;
2770  return handler.failed();
2771  }
2772 
2773  if (I == N) {
2774  // If we are reading an object of class type, there may still be more
2775  // things we need to check: if there are any mutable subobjects, we
2776  // cannot perform this read. (This only happens when performing a trivial
2777  // copy or assignment.)
2778  if (ObjType->isRecordType() && handler.AccessKind == AK_Read &&
2779  !MayReadMutableMembers && diagnoseUnreadableFields(Info, E, ObjType))
2780  return handler.failed();
2781 
2782  if (!handler.found(*O, ObjType))
2783  return false;
2784 
2785  // If we modified a bit-field, truncate it to the right width.
2786  if (handler.AccessKind != AK_Read &&
2787  LastField && LastField->isBitField() &&
2788  !truncateBitfieldValue(Info, E, *O, LastField))
2789  return false;
2790 
2791  return true;
2792  }
2793 
2794  LastField = nullptr;
2795  if (ObjType->isArrayType()) {
2796  // Next subobject is an array element.
2797  const ConstantArrayType *CAT = Info.Ctx.getAsConstantArrayType(ObjType);
2798  assert(CAT && "vla in literal type?");
2799  uint64_t Index = Sub.Entries[I].ArrayIndex;
2800  if (CAT->getSize().ule(Index)) {
2801  // Note, it should not be possible to form a pointer with a valid
2802  // designator which points more than one past the end of the array.
2803  if (Info.getLangOpts().CPlusPlus11)
2804  Info.FFDiag(E, diag::note_constexpr_access_past_end)
2805  << handler.AccessKind;
2806  else
2807  Info.FFDiag(E);
2808  return handler.failed();
2809  }
2810 
2811  ObjType = CAT->getElementType();
2812 
2813  // An array object is represented as either an Array APValue or as an
2814  // LValue which refers to a string literal.
2815  if (O->isLValue()) {
2816  assert(I == N - 1 && "extracting subobject of character?");
2817  assert(!O->hasLValuePath() || O->getLValuePath().empty());
2818  if (handler.AccessKind != AK_Read)
2819  expandStringLiteral(Info, O->getLValueBase().get<const Expr *>(),
2820  *O);
2821  else
2822  return handler.foundString(*O, ObjType, Index);
2823  }
2824 
2825  if (O->getArrayInitializedElts() > Index)
2826  O = &O->getArrayInitializedElt(Index);
2827  else if (handler.AccessKind != AK_Read) {
2828  expandArray(*O, Index);
2829  O = &O->getArrayInitializedElt(Index);
2830  } else
2831  O = &O->getArrayFiller();
2832  } else if (ObjType->isAnyComplexType()) {
2833  // Next subobject is a complex number.
2834  uint64_t Index = Sub.Entries[I].ArrayIndex;
2835  if (Index > 1) {
2836  if (Info.getLangOpts().CPlusPlus11)
2837  Info.FFDiag(E, diag::note_constexpr_access_past_end)
2838  << handler.AccessKind;
2839  else
2840  Info.FFDiag(E);
2841  return handler.failed();
2842  }
2843 
2844  bool WasConstQualified = ObjType.isConstQualified();
2845  ObjType = ObjType->castAs<ComplexType>()->getElementType();
2846  if (WasConstQualified)
2847  ObjType.addConst();
2848 
2849  assert(I == N - 1 && "extracting subobject of scalar?");
2850  if (O->isComplexInt()) {
2851  return handler.found(Index ? O->getComplexIntImag()
2852  : O->getComplexIntReal(), ObjType);
2853  } else {
2854  assert(O->isComplexFloat());
2855  return handler.found(Index ? O->getComplexFloatImag()
2856  : O->getComplexFloatReal(), ObjType);
2857  }
2858  } else if (const FieldDecl *Field = getAsField(Sub.Entries[I])) {
2859  // In C++14 onwards, it is permitted to read a mutable member whose
2860  // lifetime began within the evaluation.
2861  // FIXME: Should we also allow this in C++11?
2862  if (Field->isMutable() && handler.AccessKind == AK_Read &&
2863  !MayReadMutableMembers) {
2864  Info.FFDiag(E, diag::note_constexpr_ltor_mutable, 1)
2865  << Field;
2866  Info.Note(Field->getLocation(), diag::note_declared_at);
2867  return handler.failed();
2868  }
2869 
2870  // Next subobject is a class, struct or union field.
2871  RecordDecl *RD = ObjType->castAs<RecordType>()->getDecl();
2872  if (RD->isUnion()) {
2873  const FieldDecl *UnionField = O->getUnionField();
2874  if (!UnionField ||
2875  UnionField->getCanonicalDecl() != Field->getCanonicalDecl()) {
2876  Info.FFDiag(E, diag::note_constexpr_access_inactive_union_member)
2877  << handler.AccessKind << Field << !UnionField << UnionField;
2878  return handler.failed();
2879  }
2880  O = &O->getUnionValue();
2881  } else
2882  O = &O->getStructField(Field->getFieldIndex());
2883 
2884  bool WasConstQualified = ObjType.isConstQualified();
2885  ObjType = Field->getType();
2886  if (WasConstQualified && !Field->isMutable())
2887  ObjType.addConst();
2888 
2889  if (ObjType.isVolatileQualified()) {
2890  if (Info.getLangOpts().CPlusPlus) {
2891  // FIXME: Include a description of the path to the volatile subobject.
2892  Info.FFDiag(E, diag::note_constexpr_access_volatile_obj, 1)
2893  << handler.AccessKind << 2 << Field;
2894  Info.Note(Field->getLocation(), diag::note_declared_at);
2895  } else {
2896  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2897  }
2898  return handler.failed();
2899  }
2900 
2901  LastField = Field;
2902  } else {
2903  // Next subobject is a base class.
2904  const CXXRecordDecl *Derived = ObjType->getAsCXXRecordDecl();
2905  const CXXRecordDecl *Base = getAsBaseClass(Sub.Entries[I]);
2906  O = &O->getStructBase(getBaseIndex(Derived, Base));
2907 
2908  bool WasConstQualified = ObjType.isConstQualified();
2909  ObjType = Info.Ctx.getRecordType(Base);
2910  if (WasConstQualified)
2911  ObjType.addConst();
2912  }
2913  }
2914 }
2915 
2916 namespace {
2917 struct ExtractSubobjectHandler {
2918  EvalInfo &Info;
2919  APValue &Result;
2920 
2921  static const AccessKinds AccessKind = AK_Read;
2922 
2923  typedef bool result_type;
2924  bool failed() { return false; }
2925  bool found(APValue &Subobj, QualType SubobjType) {
2926  Result = Subobj;
2927  return true;
2928  }
2929  bool found(APSInt &Value, QualType SubobjType) {
2930  Result = APValue(Value);
2931  return true;
2932  }
2933  bool found(APFloat &Value, QualType SubobjType) {
2934  Result = APValue(Value);
2935  return true;
2936  }
2937  bool foundString(APValue &Subobj, QualType SubobjType, uint64_t Character) {
2939  Info, Subobj.getLValueBase().get<const Expr *>(), Character));
2940  return true;
2941  }
2942 };
2943 } // end anonymous namespace
2944 
2946 
2947 /// Extract the designated sub-object of an rvalue.
2948 static bool extractSubobject(EvalInfo &Info, const Expr *E,
2949  const CompleteObject &Obj,
2950  const SubobjectDesignator &Sub,
2951  APValue &Result) {
2952  ExtractSubobjectHandler Handler = { Info, Result };
2953  return findSubobject(Info, E, Obj, Sub, Handler);
2954 }
2955 
2956 namespace {
2957 struct ModifySubobjectHandler {
2958  EvalInfo &Info;
2959  APValue &NewVal;
2960  const Expr *E;
2961 
2962  typedef bool result_type;
2963  static const AccessKinds AccessKind = AK_Assign;
2964 
2965  bool checkConst(QualType QT) {
2966  // Assigning to a const object has undefined behavior.
2967  if (QT.isConstQualified()) {
2968  Info.FFDiag(E, diag::note_constexpr_modify_const_type) << QT;
2969  return false;
2970  }
2971  return true;
2972  }
2973 
2974  bool failed() { return false; }
2975  bool found(APValue &Subobj, QualType SubobjType) {
2976  if (!checkConst(SubobjType))
2977  return false;
2978  // We've been given ownership of NewVal, so just swap it in.
2979  Subobj.swap(NewVal);
2980  return true;
2981  }
2982  bool found(APSInt &Value, QualType SubobjType) {
2983  if (!checkConst(SubobjType))
2984  return false;
2985  if (!NewVal.isInt()) {
2986  // Maybe trying to write a cast pointer value into a complex?
2987  Info.FFDiag(E);
2988  return false;
2989  }
2990  Value = NewVal.getInt();
2991  return true;
2992  }
2993  bool found(APFloat &Value, QualType SubobjType) {
2994  if (!checkConst(SubobjType))
2995  return false;
2996  Value = NewVal.getFloat();
2997  return true;
2998  }
2999  bool foundString(APValue &Subobj, QualType SubobjType, uint64_t Character) {
3000  llvm_unreachable("shouldn't encounter string elements with ExpandArrays");
3001  }
3002 };
3003 } // end anonymous namespace
3004 
3006 
3007 /// Update the designated sub-object of an rvalue to the given value.
3008 static bool modifySubobject(EvalInfo &Info, const Expr *E,
3009  const CompleteObject &Obj,
3010  const SubobjectDesignator &Sub,
3011  APValue &NewVal) {
3012  ModifySubobjectHandler Handler = { Info, NewVal, E };
3013  return findSubobject(Info, E, Obj, Sub, Handler);
3014 }
3015 
3016 /// Find the position where two subobject designators diverge, or equivalently
3017 /// the length of the common initial subsequence.
3018 static unsigned FindDesignatorMismatch(QualType ObjType,
3019  const SubobjectDesignator &A,
3020  const SubobjectDesignator &B,
3021  bool &WasArrayIndex) {
3022  unsigned I = 0, N = std::min(A.Entries.size(), B.Entries.size());
3023  for (/**/; I != N; ++I) {
3024  if (!ObjType.isNull() &&
3025  (ObjType->isArrayType() || ObjType->isAnyComplexType())) {
3026  // Next subobject is an array element.
3027  if (A.Entries[I].ArrayIndex != B.Entries[I].ArrayIndex) {
3028  WasArrayIndex = true;
3029  return I;
3030  }
3031  if (ObjType->isAnyComplexType())
3032  ObjType = ObjType->castAs<ComplexType>()->getElementType();
3033  else
3034  ObjType = ObjType->castAsArrayTypeUnsafe()->getElementType();
3035  } else {
3036  if (A.Entries[I].BaseOrMember != B.Entries[I].BaseOrMember) {
3037  WasArrayIndex = false;
3038  return I;
3039  }
3040  if (const FieldDecl *FD = getAsField(A.Entries[I]))
3041  // Next subobject is a field.
3042  ObjType = FD->getType();
3043  else
3044  // Next subobject is a base class.
3045  ObjType = QualType();
3046  }
3047  }
3048  WasArrayIndex = false;
3049  return I;
3050 }
3051 
3052 /// Determine whether the given subobject designators refer to elements of the
3053 /// same array object.
3054 static bool AreElementsOfSameArray(QualType ObjType,
3055  const SubobjectDesignator &A,
3056  const SubobjectDesignator &B) {
3057  if (A.Entries.size() != B.Entries.size())
3058  return false;
3059 
3060  bool IsArray = A.MostDerivedIsArrayElement;
3061  if (IsArray && A.MostDerivedPathLength != A.Entries.size())
3062  // A is a subobject of the array element.
3063  return false;
3064 
3065  // If A (and B) designates an array element, the last entry will be the array
3066  // index. That doesn't have to match. Otherwise, we're in the 'implicit array
3067  // of length 1' case, and the entire path must match.
3068  bool WasArrayIndex;
3069  unsigned CommonLength = FindDesignatorMismatch(ObjType, A, B, WasArrayIndex);
3070  return CommonLength >= A.Entries.size() - IsArray;
3071 }
3072 
3073 /// Find the complete object to which an LValue refers.
3074 static CompleteObject findCompleteObject(EvalInfo &Info, const Expr *E,
3075  AccessKinds AK, const LValue &LVal,
3076  QualType LValType) {
3077  if (!LVal.Base) {
3078  Info.FFDiag(E, diag::note_constexpr_access_null) << AK;
3079  return CompleteObject();
3080  }
3081 
3082  CallStackFrame *Frame = nullptr;
3083  if (LVal.getLValueCallIndex()) {
3084  Frame = Info.getCallFrame(LVal.getLValueCallIndex());
3085  if (!Frame) {
3086  Info.FFDiag(E, diag::note_constexpr_lifetime_ended, 1)
3087  << AK << LVal.Base.is<const ValueDecl*>();
3088  NoteLValueLocation(Info, LVal.Base);
3089  return CompleteObject();
3090  }
3091  }
3092 
3093  // C++11 DR1311: An lvalue-to-rvalue conversion on a volatile-qualified type
3094  // is not a constant expression (even if the object is non-volatile). We also
3095  // apply this rule to C++98, in order to conform to the expected 'volatile'
3096  // semantics.
3097  if (LValType.isVolatileQualified()) {
3098  if (Info.getLangOpts().CPlusPlus)
3099  Info.FFDiag(E, diag::note_constexpr_access_volatile_type)
3100  << AK << LValType;
3101  else
3102  Info.FFDiag(E);
3103  return CompleteObject();
3104  }
3105 
3106  // Compute value storage location and type of base object.
3107  APValue *BaseVal = nullptr;
3108  QualType BaseType = getType(LVal.Base);
3109  bool LifetimeStartedInEvaluation = Frame;
3110 
3111  if (const ValueDecl *D = LVal.Base.dyn_cast<const ValueDecl*>()) {
3112  // In C++98, const, non-volatile integers initialized with ICEs are ICEs.
3113  // In C++11, constexpr, non-volatile variables initialized with constant
3114  // expressions are constant expressions too. Inside constexpr functions,
3115  // parameters are constant expressions even if they're non-const.
3116  // In C++1y, objects local to a constant expression (those with a Frame) are
3117  // both readable and writable inside constant expressions.
3118  // In C, such things can also be folded, although they are not ICEs.
3119  const VarDecl *VD = dyn_cast<VarDecl>(D);
3120  if (VD) {
3121  if (const VarDecl *VDef = VD->getDefinition(Info.Ctx))
3122  VD = VDef;
3123  }
3124  if (!VD || VD->isInvalidDecl()) {
3125  Info.FFDiag(E);
3126  return CompleteObject();
3127  }
3128 
3129  // Accesses of volatile-qualified objects are not allowed.
3130  if (BaseType.isVolatileQualified()) {
3131  if (Info.getLangOpts().CPlusPlus) {
3132  Info.FFDiag(E, diag::note_constexpr_access_volatile_obj, 1)
3133  << AK << 1 << VD;
3134  Info.Note(VD->getLocation(), diag::note_declared_at);
3135  } else {
3136  Info.FFDiag(E);
3137  }
3138  return CompleteObject();
3139  }
3140 
3141  // Unless we're looking at a local variable or argument in a constexpr call,
3142  // the variable we're reading must be const.
3143  if (!Frame) {
3144  if (Info.getLangOpts().CPlusPlus14 &&
3145  VD == Info.EvaluatingDecl.dyn_cast<const ValueDecl *>()) {
3146  // OK, we can read and modify an object if we're in the process of
3147  // evaluating its initializer, because its lifetime began in this
3148  // evaluation.
3149  } else if (AK != AK_Read) {
3150  // All the remaining cases only permit reading.
3151  Info.FFDiag(E, diag::note_constexpr_modify_global);
3152  return CompleteObject();
3153  } else if (VD->isConstexpr()) {
3154  // OK, we can read this variable.
3155  } else if (BaseType->isIntegralOrEnumerationType()) {
3156  // In OpenCL if a variable is in constant address space it is a const value.
3157  if (!(BaseType.isConstQualified() ||
3158  (Info.getLangOpts().OpenCL &&
3159  BaseType.getAddressSpace() == LangAS::opencl_constant))) {
3160  if (Info.getLangOpts().CPlusPlus) {
3161  Info.FFDiag(E, diag::note_constexpr_ltor_non_const_int, 1) << VD;
3162  Info.Note(VD->getLocation(), diag::note_declared_at);
3163  } else {
3164  Info.FFDiag(E);
3165  }
3166  return CompleteObject();
3167  }
3168  } else if (BaseType->isFloatingType() && BaseType.isConstQualified()) {
3169  // We support folding of const floating-point types, in order to make
3170  // static const data members of such types (supported as an extension)
3171  // more useful.
3172  if (Info.getLangOpts().CPlusPlus11) {
3173  Info.CCEDiag(E, diag::note_constexpr_ltor_non_constexpr, 1) << VD;
3174  Info.Note(VD->getLocation(), diag::note_declared_at);
3175  } else {
3176  Info.CCEDiag(E);
3177  }
3178  } else if (BaseType.isConstQualified() && VD->hasDefinition(Info.Ctx)) {
3179  Info.CCEDiag(E, diag::note_constexpr_ltor_non_constexpr) << VD;
3180  // Keep evaluating to see what we can do.
3181  } else {
3182  // FIXME: Allow folding of values of any literal type in all languages.
3183  if (Info.checkingPotentialConstantExpression() &&
3184  VD->getType().isConstQualified() && !VD->hasDefinition(Info.Ctx)) {
3185  // The definition of this variable could be constexpr. We can't
3186  // access it right now, but may be able to in future.
3187  } else if (Info.getLangOpts().CPlusPlus11) {
3188  Info.FFDiag(E, diag::note_constexpr_ltor_non_constexpr, 1) << VD;
3189  Info.Note(VD->getLocation(), diag::note_declared_at);
3190  } else {
3191  Info.FFDiag(E);
3192  }
3193  return CompleteObject();
3194  }
3195  }
3196 
3197  if (!evaluateVarDeclInit(Info, E, VD, Frame, BaseVal, &LVal))
3198  return CompleteObject();
3199  } else {
3200  const Expr *Base = LVal.Base.dyn_cast<const Expr*>();
3201 
3202  if (!Frame) {
3203  if (const MaterializeTemporaryExpr *MTE =
3204  dyn_cast<MaterializeTemporaryExpr>(Base)) {
3205  assert(MTE->getStorageDuration() == SD_Static &&
3206  "should have a frame for a non-global materialized temporary");
3207 
3208  // Per C++1y [expr.const]p2:
3209  // an lvalue-to-rvalue conversion [is not allowed unless it applies to]
3210  // - a [...] glvalue of integral or enumeration type that refers to
3211  // a non-volatile const object [...]
3212  // [...]
3213  // - a [...] glvalue of literal type that refers to a non-volatile
3214  // object whose lifetime began within the evaluation of e.
3215  //
3216  // C++11 misses the 'began within the evaluation of e' check and
3217  // instead allows all temporaries, including things like:
3218  // int &&r = 1;
3219  // int x = ++r;
3220  // constexpr int k = r;
3221  // Therefore we use the C++14 rules in C++11 too.
3222  const ValueDecl *VD = Info.EvaluatingDecl.dyn_cast<const ValueDecl*>();
3223  const ValueDecl *ED = MTE->getExtendingDecl();
3224  if (!(BaseType.isConstQualified() &&
3225  BaseType->isIntegralOrEnumerationType()) &&
3226  !(VD && VD->getCanonicalDecl() == ED->getCanonicalDecl())) {
3227  Info.FFDiag(E, diag::note_constexpr_access_static_temporary, 1) << AK;
3228  Info.Note(MTE->getExprLoc(), diag::note_constexpr_temporary_here);
3229  return CompleteObject();
3230  }
3231 
3232  BaseVal = Info.Ctx.getMaterializedTemporaryValue(MTE, false);
3233  assert(BaseVal && "got reference to unevaluated temporary");
3234  LifetimeStartedInEvaluation = true;
3235  } else {
3236  Info.FFDiag(E);
3237  return CompleteObject();
3238  }
3239  } else {
3240  BaseVal = Frame->getTemporary(Base, LVal.Base.getVersion());
3241  assert(BaseVal && "missing value for temporary");
3242  }
3243 
3244  // Volatile temporary objects cannot be accessed in constant expressions.
3245  if (BaseType.isVolatileQualified()) {
3246  if (Info.getLangOpts().CPlusPlus) {
3247  Info.FFDiag(E, diag::note_constexpr_access_volatile_obj, 1)
3248  << AK << 0;
3249  Info.Note(Base->getExprLoc(), diag::note_constexpr_temporary_here);
3250  } else {
3251  Info.FFDiag(E);
3252  }
3253  return CompleteObject();
3254  }
3255  }
3256 
3257  // During the construction of an object, it is not yet 'const'.
3258  // FIXME: This doesn't do quite the right thing for const subobjects of the
3259  // object under construction.
3260  if (Info.isEvaluatingConstructor(LVal.getLValueBase(),
3261  LVal.getLValueCallIndex(),
3262  LVal.getLValueVersion())) {
3263  BaseType = Info.Ctx.getCanonicalType(BaseType);
3264  BaseType.removeLocalConst();
3265  LifetimeStartedInEvaluation = true;
3266  }
3267 
3268  // In C++14, we can't safely access any mutable state when we might be
3269  // evaluating after an unmodeled side effect.
3270  //
3271  // FIXME: Not all local state is mutable. Allow local constant subobjects
3272  // to be read here (but take care with 'mutable' fields).
3273  if ((Frame && Info.getLangOpts().CPlusPlus14 &&
3274  Info.EvalStatus.HasSideEffects) ||
3275  (AK != AK_Read && Info.IsSpeculativelyEvaluating))
3276  return CompleteObject();
3277 
3278  return CompleteObject(BaseVal, BaseType, LifetimeStartedInEvaluation);
3279 }
3280 
3281 /// Perform an lvalue-to-rvalue conversion on the given glvalue. This
3282 /// can also be used for 'lvalue-to-lvalue' conversions for looking up the
3283 /// glvalue referred to by an entity of reference type.
3284 ///
3285 /// \param Info - Information about the ongoing evaluation.
3286 /// \param Conv - The expression for which we are performing the conversion.
3287 /// Used for diagnostics.
3288 /// \param Type - The type of the glvalue (before stripping cv-qualifiers in the
3289 /// case of a non-class type).
3290 /// \param LVal - The glvalue on which we are attempting to perform this action.
3291 /// \param RVal - The produced value will be placed here.
3292 static bool handleLValueToRValueConversion(EvalInfo &Info, const Expr *Conv,
3293  QualType Type,
3294  const LValue &LVal, APValue &RVal) {
3295  if (LVal.Designator.Invalid)
3296  return false;
3297 
3298  // Check for special cases where there is no existing APValue to look at.
3299  const Expr *Base = LVal.Base.dyn_cast<const Expr*>();
3300  if (Base && !LVal.getLValueCallIndex() && !Type.isVolatileQualified()) {
3301  if (const CompoundLiteralExpr *CLE = dyn_cast<CompoundLiteralExpr>(Base)) {
3302  // In C99, a CompoundLiteralExpr is an lvalue, and we defer evaluating the
3303  // initializer until now for such expressions. Such an expression can't be
3304  // an ICE in C, so this only matters for fold.
3305  if (Type.isVolatileQualified()) {
3306  Info.FFDiag(Conv);
3307  return false;
3308  }
3309  APValue Lit;
3310  if (!Evaluate(Lit, Info, CLE->getInitializer()))
3311  return false;
3312  CompleteObject LitObj(&Lit, Base->getType(), false);
3313  return extractSubobject(Info, Conv, LitObj, LVal.Designator, RVal);
3314  } else if (isa<StringLiteral>(Base) || isa<PredefinedExpr>(Base)) {
3315  // We represent a string literal array as an lvalue pointing at the
3316  // corresponding expression, rather than building an array of chars.
3317  // FIXME: Support ObjCEncodeExpr, MakeStringConstant
3318  APValue Str(Base, CharUnits::Zero(), APValue::NoLValuePath(), 0);
3319  CompleteObject StrObj(&Str, Base->getType(), false);
3320  return extractSubobject(Info, Conv, StrObj, LVal.Designator, RVal);
3321  }
3322  }
3323 
3324  CompleteObject Obj = findCompleteObject(Info, Conv, AK_Read, LVal, Type);
3325  return Obj && extractSubobject(Info, Conv, Obj, LVal.Designator, RVal);
3326 }
3327 
3328 /// Perform an assignment of Val to LVal. Takes ownership of Val.
3329 static bool handleAssignment(EvalInfo &Info, const Expr *E, const LValue &LVal,
3330  QualType LValType, APValue &Val) {
3331  if (LVal.Designator.Invalid)
3332  return false;
3333 
3334  if (!Info.getLangOpts().CPlusPlus14) {
3335  Info.FFDiag(E);
3336  return false;
3337  }
3338 
3339  CompleteObject Obj = findCompleteObject(Info, E, AK_Assign, LVal, LValType);
3340  return Obj && modifySubobject(Info, E, Obj, LVal.Designator, Val);
3341 }
3342 
3343 namespace {
3344 struct CompoundAssignSubobjectHandler {
3345  EvalInfo &Info;
3346  const Expr *E;
3347  QualType PromotedLHSType;
3348  BinaryOperatorKind Opcode;
3349  const APValue &RHS;
3350 
3351  static const AccessKinds AccessKind = AK_Assign;
3352 
3353  typedef bool result_type;
3354 
3355  bool checkConst(QualType QT) {
3356  // Assigning to a const object has undefined behavior.
3357  if (QT.isConstQualified()) {
3358  Info.FFDiag(E, diag::note_constexpr_modify_const_type) << QT;
3359  return false;
3360  }
3361  return true;
3362  }
3363 
3364  bool failed() { return false; }
3365  bool found(APValue &Subobj, QualType SubobjType) {
3366  switch (Subobj.getKind()) {
3367  case APValue::Int:
3368  return found(Subobj.getInt(), SubobjType);
3369  case APValue::Float:
3370  return found(Subobj.getFloat(), SubobjType);
3371  case APValue::ComplexInt:
3372  case APValue::ComplexFloat:
3373  // FIXME: Implement complex compound assignment.
3374  Info.FFDiag(E);
3375  return false;
3376  case APValue::LValue:
3377  return foundPointer(Subobj, SubobjType);
3378  default:
3379  // FIXME: can this happen?
3380  Info.FFDiag(E);
3381  return false;
3382  }
3383  }
3384  bool found(APSInt &Value, QualType SubobjType) {
3385  if (!checkConst(SubobjType))
3386  return false;
3387 
3388  if (!SubobjType->isIntegerType() || !RHS.isInt()) {
3389  // We don't support compound assignment on integer-cast-to-pointer
3390  // values.
3391  Info.FFDiag(E);
3392  return false;
3393  }
3394 
3395  APSInt LHS = HandleIntToIntCast(Info, E, PromotedLHSType,
3396  SubobjType, Value);
3397  if (!handleIntIntBinOp(Info, E, LHS, Opcode, RHS.getInt(), LHS))
3398  return false;
3399  Value = HandleIntToIntCast(Info, E, SubobjType, PromotedLHSType, LHS);
3400  return true;
3401  }
3402  bool found(APFloat &Value, QualType SubobjType) {
3403  return checkConst(SubobjType) &&
3404  HandleFloatToFloatCast(Info, E, SubobjType, PromotedLHSType,
3405  Value) &&
3406  handleFloatFloatBinOp(Info, E, Value, Opcode, RHS.getFloat()) &&
3407  HandleFloatToFloatCast(Info, E, PromotedLHSType, SubobjType, Value);
3408  }
3409  bool foundPointer(APValue &Subobj, QualType SubobjType) {
3410  if (!checkConst(SubobjType))
3411  return false;
3412 
3413  QualType PointeeType;
3414  if (const PointerType *PT = SubobjType->getAs<PointerType>())
3415  PointeeType = PT->getPointeeType();
3416 
3417  if (PointeeType.isNull() || !RHS.isInt() ||
3418  (Opcode != BO_Add && Opcode != BO_Sub)) {
3419  Info.FFDiag(E);
3420  return false;
3421  }
3422 
3423  APSInt Offset = RHS.getInt();
3424  if (Opcode == BO_Sub)
3425  negateAsSigned(Offset);
3426 
3427  LValue LVal;
3428  LVal.setFrom(Info.Ctx, Subobj);
3429  if (!HandleLValueArrayAdjustment(Info, E, LVal, PointeeType, Offset))
3430  return false;
3431  LVal.moveInto(Subobj);
3432  return true;
3433  }
3434  bool foundString(APValue &Subobj, QualType SubobjType, uint64_t Character) {
3435  llvm_unreachable("shouldn't encounter string elements here");
3436  }
3437 };
3438 } // end anonymous namespace
3439 
3441 
3442 /// Perform a compound assignment of LVal <op>= RVal.
3444  EvalInfo &Info, const Expr *E,
3445  const LValue &LVal, QualType LValType, QualType PromotedLValType,
3446  BinaryOperatorKind Opcode, const APValue &RVal) {
3447  if (LVal.Designator.Invalid)
3448  return false;
3449 
3450  if (!Info.getLangOpts().CPlusPlus14) {
3451  Info.FFDiag(E);
3452  return false;
3453  }
3454 
3455  CompleteObject Obj = findCompleteObject(Info, E, AK_Assign, LVal, LValType);
3456  CompoundAssignSubobjectHandler Handler = { Info, E, PromotedLValType, Opcode,
3457  RVal };
3458  return Obj && findSubobject(Info, E, Obj, LVal.Designator, Handler);
3459 }
3460 
3461 namespace {
3462 struct IncDecSubobjectHandler {
3463  EvalInfo &Info;
3464  const UnaryOperator *E;
3466  APValue *Old;
3467 
3468  typedef bool result_type;
3469 
3470  bool checkConst(QualType QT) {
3471  // Assigning to a const object has undefined behavior.
3472  if (QT.isConstQualified()) {
3473  Info.FFDiag(E, diag::note_constexpr_modify_const_type) << QT;
3474  return false;
3475  }
3476  return true;
3477  }
3478 
3479  bool failed() { return false; }
3480  bool found(APValue &Subobj, QualType SubobjType) {
3481  // Stash the old value. Also clear Old, so we don't clobber it later
3482  // if we're post-incrementing a complex.
3483  if (Old) {
3484  *Old = Subobj;
3485  Old = nullptr;
3486  }
3487 
3488  switch (Subobj.getKind()) {
3489  case APValue::Int:
3490  return found(Subobj.getInt(), SubobjType);
3491  case APValue::Float:
3492  return found(Subobj.getFloat(), SubobjType);
3493  case APValue::ComplexInt:
3494  return found(Subobj.getComplexIntReal(),
3495  SubobjType->castAs<ComplexType>()->getElementType()
3496  .withCVRQualifiers(SubobjType.getCVRQualifiers()));
3497  case APValue::ComplexFloat:
3498  return found(Subobj.getComplexFloatReal(),
3499  SubobjType->castAs<ComplexType>()->getElementType()
3500  .withCVRQualifiers(SubobjType.getCVRQualifiers()));
3501  case APValue::LValue:
3502  return foundPointer(Subobj, SubobjType);
3503  default:
3504  // FIXME: can this happen?
3505  Info.FFDiag(E);
3506  return false;
3507  }
3508  }
3509  bool found(APSInt &Value, QualType SubobjType) {
3510  if (!checkConst(SubobjType))
3511  return false;
3512 
3513  if (!SubobjType->isIntegerType()) {
3514  // We don't support increment / decrement on integer-cast-to-pointer
3515  // values.
3516  Info.FFDiag(E);
3517  return false;
3518  }
3519 
3520  if (Old) *Old = APValue(Value);
3521 
3522  // bool arithmetic promotes to int, and the conversion back to bool
3523  // doesn't reduce mod 2^n, so special-case it.
3524  if (SubobjType->isBooleanType()) {
3525  if (AccessKind == AK_Increment)
3526  Value = 1;
3527  else
3528  Value = !Value;
3529  return true;
3530  }
3531 
3532  bool WasNegative = Value.isNegative();
3533  if (AccessKind == AK_Increment) {
3534  ++Value;
3535 
3536  if (!WasNegative && Value.isNegative() && E->canOverflow()) {
3537  APSInt ActualValue(Value, /*IsUnsigned*/true);
3538  return HandleOverflow(Info, E, ActualValue, SubobjType);
3539  }
3540  } else {
3541  --Value;
3542 
3543  if (WasNegative && !Value.isNegative() && E->canOverflow()) {
3544  unsigned BitWidth = Value.getBitWidth();
3545  APSInt ActualValue(Value.sext(BitWidth + 1), /*IsUnsigned*/false);
3546  ActualValue.setBit(BitWidth);
3547  return HandleOverflow(Info, E, ActualValue, SubobjType);
3548  }
3549  }
3550  return true;
3551  }
3552  bool found(APFloat &Value, QualType SubobjType) {
3553  if (!checkConst(SubobjType))
3554  return false;
3555 
3556  if (Old) *Old = APValue(Value);
3557 
3558  APFloat One(Value.getSemantics(), 1);
3559  if (AccessKind == AK_Increment)
3560  Value.add(One, APFloat::rmNearestTiesToEven);
3561  else
3562  Value.subtract(One, APFloat::rmNearestTiesToEven);
3563  return true;
3564  }
3565  bool foundPointer(APValue &Subobj, QualType SubobjType) {
3566  if (!checkConst(SubobjType))
3567  return false;
3568 
3569  QualType PointeeType;
3570  if (const PointerType *PT = SubobjType->getAs<PointerType>())
3571  PointeeType = PT->getPointeeType();
3572  else {
3573  Info.FFDiag(E);
3574  return false;
3575  }
3576 
3577  LValue LVal;
3578  LVal.setFrom(Info.Ctx, Subobj);
3579  if (!HandleLValueArrayAdjustment(Info, E, LVal, PointeeType,
3580  AccessKind == AK_Increment ? 1 : -1))
3581  return false;
3582  LVal.moveInto(Subobj);
3583  return true;
3584  }
3585  bool foundString(APValue &Subobj, QualType SubobjType, uint64_t Character) {
3586  llvm_unreachable("shouldn't encounter string elements here");
3587  }
3588 };
3589 } // end anonymous namespace
3590 
3591 /// Perform an increment or decrement on LVal.
3592 static bool handleIncDec(EvalInfo &Info, const Expr *E, const LValue &LVal,
3593  QualType LValType, bool IsIncrement, APValue *Old) {
3594  if (LVal.Designator.Invalid)
3595  return false;
3596 
3597  if (!Info.getLangOpts().CPlusPlus14) {
3598  Info.FFDiag(E);
3599  return false;
3600  }
3601 
3602  AccessKinds AK = IsIncrement ? AK_Increment : AK_Decrement;
3603  CompleteObject Obj = findCompleteObject(Info, E, AK, LVal, LValType);
3604  IncDecSubobjectHandler Handler = {Info, cast<UnaryOperator>(E), AK, Old};
3605  return Obj && findSubobject(Info, E, Obj, LVal.Designator, Handler);
3606 }
3607 
3608 /// Build an lvalue for the object argument of a member function call.
3609 static bool EvaluateObjectArgument(EvalInfo &Info, const Expr *Object,
3610  LValue &This) {
3611  if (Object->getType()->isPointerType())
3612  return EvaluatePointer(Object, This, Info);
3613 
3614  if (Object->isGLValue())
3615  return EvaluateLValue(Object, This, Info);
3616 
3617  if (Object->getType()->isLiteralType(Info.Ctx))
3618  return EvaluateTemporary(Object, This, Info);
3619 
3620  Info.FFDiag(Object, diag::note_constexpr_nonliteral) << Object->getType();
3621  return false;
3622 }
3623 
3624 /// HandleMemberPointerAccess - Evaluate a member access operation and build an
3625 /// lvalue referring to the result.
3626 ///
3627 /// \param Info - Information about the ongoing evaluation.
3628 /// \param LV - An lvalue referring to the base of the member pointer.
3629 /// \param RHS - The member pointer expression.
3630 /// \param IncludeMember - Specifies whether the member itself is included in
3631 /// the resulting LValue subobject designator. This is not possible when
3632 /// creating a bound member function.
3633 /// \return The field or method declaration to which the member pointer refers,
3634 /// or 0 if evaluation fails.
3635 static const ValueDecl *HandleMemberPointerAccess(EvalInfo &Info,
3636  QualType LVType,
3637  LValue &LV,
3638  const Expr *RHS,
3639  bool IncludeMember = true) {
3640  MemberPtr MemPtr;
3641  if (!EvaluateMemberPointer(RHS, MemPtr, Info))
3642  return nullptr;
3643 
3644  // C++11 [expr.mptr.oper]p6: If the second operand is the null pointer to
3645  // member value, the behavior is undefined.
3646  if (!MemPtr.getDecl()) {
3647  // FIXME: Specific diagnostic.
3648  Info.FFDiag(RHS);
3649  return nullptr;
3650  }
3651 
3652  if (MemPtr.isDerivedMember()) {
3653  // This is a member of some derived class. Truncate LV appropriately.
3654  // The end of the derived-to-base path for the base object must match the
3655  // derived-to-base path for the member pointer.
3656  if (LV.Designator.MostDerivedPathLength + MemPtr.Path.size() >
3657  LV.Designator.Entries.size()) {
3658  Info.FFDiag(RHS);
3659  return nullptr;
3660  }
3661  unsigned PathLengthToMember =
3662  LV.Designator.Entries.size() - MemPtr.Path.size();
3663  for (unsigned I = 0, N = MemPtr.Path.size(); I != N; ++I) {
3664  const CXXRecordDecl *LVDecl = getAsBaseClass(
3665  LV.Designator.Entries[PathLengthToMember + I]);
3666  const CXXRecordDecl *MPDecl = MemPtr.Path[I];
3667  if (LVDecl->getCanonicalDecl() != MPDecl->getCanonicalDecl()) {
3668  Info.FFDiag(RHS);
3669  return nullptr;
3670  }
3671  }
3672 
3673  // Truncate the lvalue to the appropriate derived class.
3674  if (!CastToDerivedClass(Info, RHS, LV, MemPtr.getContainingRecord(),
3675  PathLengthToMember))
3676  return nullptr;
3677  } else if (!MemPtr.Path.empty()) {
3678  // Extend the LValue path with the member pointer's path.
3679  LV.Designator.Entries.reserve(LV.Designator.Entries.size() +
3680  MemPtr.Path.size() + IncludeMember);
3681 
3682  // Walk down to the appropriate base class.
3683  if (const PointerType *PT = LVType->getAs<PointerType>())
3684  LVType = PT->getPointeeType();
3685  const CXXRecordDecl *RD = LVType->getAsCXXRecordDecl();
3686  assert(RD && "member pointer access on non-class-type expression");
3687  // The first class in the path is that of the lvalue.
3688  for (unsigned I = 1, N = MemPtr.Path.size(); I != N; ++I) {
3689  const CXXRecordDecl *Base = MemPtr.Path[N - I - 1];
3690  if (!HandleLValueDirectBase(Info, RHS, LV, RD, Base))
3691  return nullptr;
3692  RD = Base;
3693  }
3694  // Finally cast to the class containing the member.
3695  if (!HandleLValueDirectBase(Info, RHS, LV, RD,
3696  MemPtr.getContainingRecord()))
3697  return nullptr;
3698  }
3699 
3700  // Add the member. Note that we cannot build bound member functions here.
3701  if (IncludeMember) {
3702  if (const FieldDecl *FD = dyn_cast<FieldDecl>(MemPtr.getDecl())) {
3703  if (!HandleLValueMember(Info, RHS, LV, FD))
3704  return nullptr;
3705  } else if (const IndirectFieldDecl *IFD =
3706  dyn_cast<IndirectFieldDecl>(MemPtr.getDecl())) {
3707  if (!HandleLValueIndirectMember(Info, RHS, LV, IFD))
3708  return nullptr;
3709  } else {
3710  llvm_unreachable("can't construct reference to bound member function");
3711  }
3712  }
3713 
3714  return MemPtr.getDecl();
3715 }
3716 
3717 static const ValueDecl *HandleMemberPointerAccess(EvalInfo &Info,
3718  const BinaryOperator *BO,
3719  LValue &LV,
3720  bool IncludeMember = true) {
3721  assert(BO->getOpcode() == BO_PtrMemD || BO->getOpcode() == BO_PtrMemI);
3722 
3723  if (!EvaluateObjectArgument(Info, BO->getLHS(), LV)) {
3724  if (Info.noteFailure()) {
3725  MemberPtr MemPtr;
3726  EvaluateMemberPointer(BO->getRHS(), MemPtr, Info);
3727  }
3728  return nullptr;
3729  }
3730 
3731  return HandleMemberPointerAccess(Info, BO->getLHS()->getType(), LV,
3732  BO->getRHS(), IncludeMember);
3733 }
3734 
3735 /// HandleBaseToDerivedCast - Apply the given base-to-derived cast operation on
3736 /// the provided lvalue, which currently refers to the base object.
3737 static bool HandleBaseToDerivedCast(EvalInfo &Info, const CastExpr *E,
3738  LValue &Result) {
3739  SubobjectDesignator &D = Result.Designator;
3740  if (D.Invalid || !Result.checkNullPointer(Info, E, CSK_Derived))
3741  return false;
3742 
3743  QualType TargetQT = E->getType();
3744  if (const PointerType *PT = TargetQT->getAs<PointerType>())
3745  TargetQT = PT->getPointeeType();
3746 
3747  // Check this cast lands within the final derived-to-base subobject path.
3748  if (D.MostDerivedPathLength + E->path_size() > D.Entries.size()) {
3749  Info.CCEDiag(E, diag::note_constexpr_invalid_downcast)
3750  << D.MostDerivedType << TargetQT;
3751  return false;
3752  }
3753 
3754  // Check the type of the final cast. We don't need to check the path,
3755  // since a cast can only be formed if the path is unique.
3756  unsigned NewEntriesSize = D.Entries.size() - E->path_size();
3757  const CXXRecordDecl *TargetType = TargetQT->getAsCXXRecordDecl();
3758  const CXXRecordDecl *FinalType;
3759  if (NewEntriesSize == D.MostDerivedPathLength)
3760  FinalType = D.MostDerivedType->getAsCXXRecordDecl();
3761  else
3762  FinalType = getAsBaseClass(D.Entries[NewEntriesSize - 1]);
3763  if (FinalType->getCanonicalDecl() != TargetType->getCanonicalDecl()) {
3764  Info.CCEDiag(E, diag::note_constexpr_invalid_downcast)
3765  << D.MostDerivedType << TargetQT;
3766  return false;
3767  }
3768 
3769  // Truncate the lvalue to the appropriate derived class.
3770  return CastToDerivedClass(Info, E, Result, TargetType, NewEntriesSize);
3771 }
3772 
3773 namespace {
3775  /// Evaluation failed.
3776  ESR_Failed,
3777  /// Hit a 'return' statement.
3778  ESR_Returned,
3779  /// Evaluation succeeded.
3780  ESR_Succeeded,
3781  /// Hit a 'continue' statement.
3782  ESR_Continue,
3783  /// Hit a 'break' statement.
3784  ESR_Break,
3785  /// Still scanning for 'case' or 'default' statement.
3786  ESR_CaseNotFound
3787 };
3788 }
3789 
3790 static bool EvaluateVarDecl(EvalInfo &Info, const VarDecl *VD) {
3791  // We don't need to evaluate the initializer for a static local.
3792  if (!VD->hasLocalStorage())
3793  return true;
3794 
3795  LValue Result;
3796  APValue &Val = createTemporary(VD, true, Result, *Info.CurrentCall);
3797 
3798  const Expr *InitE = VD->getInit();
3799  if (!InitE) {
3800  Info.FFDiag(VD->getLocStart(), diag::note_constexpr_uninitialized)
3801  << false << VD->getType();
3802  Val = APValue();
3803  return false;
3804  }
3805 
3806  if (InitE->isValueDependent())
3807  return false;
3808 
3809  if (!EvaluateInPlace(Val, Info, Result, InitE)) {
3810  // Wipe out any partially-computed value, to allow tracking that this
3811  // evaluation failed.
3812  Val = APValue();
3813  return false;
3814  }
3815 
3816  return true;
3817 }
3818 
3819 static bool EvaluateDecl(EvalInfo &Info, const Decl *D) {
3820  bool OK = true;
3821 
3822  if (const VarDecl *VD = dyn_cast<VarDecl>(D))
3823  OK &= EvaluateVarDecl(Info, VD);
3824 
3825  if (const DecompositionDecl *DD = dyn_cast<DecompositionDecl>(D))
3826  for (auto *BD : DD->bindings())
3827  if (auto *VD = BD->getHoldingVar())
3828  OK &= EvaluateDecl(Info, VD);
3829 
3830  return OK;
3831 }
3832 
3833 
3834 /// Evaluate a condition (either a variable declaration or an expression).
3835 static bool EvaluateCond(EvalInfo &Info, const VarDecl *CondDecl,
3836  const Expr *Cond, bool &Result) {
3837  FullExpressionRAII Scope(Info);
3838  if (CondDecl && !EvaluateDecl(Info, CondDecl))
3839  return false;
3840  return EvaluateAsBooleanCondition(Cond, Result, Info);
3841 }
3842 
3843 namespace {
3844 /// A location where the result (returned value) of evaluating a
3845 /// statement should be stored.
3846 struct StmtResult {
3847  /// The APValue that should be filled in with the returned value.
3848  APValue &Value;
3849  /// The location containing the result, if any (used to support RVO).
3850  const LValue *Slot;
3851 };
3852 
3853 struct TempVersionRAII {
3854  CallStackFrame &Frame;
3855 
3856  TempVersionRAII(CallStackFrame &Frame) : Frame(Frame) {
3857  Frame.pushTempVersion();
3858  }
3859 
3860  ~TempVersionRAII() {
3861  Frame.popTempVersion();
3862  }
3863 };
3864 
3865 }
3866 
3867 static EvalStmtResult EvaluateStmt(StmtResult &Result, EvalInfo &Info,
3868  const Stmt *S,
3869  const SwitchCase *SC = nullptr);
3870 
3871 /// Evaluate the body of a loop, and translate the result as appropriate.
3872 static EvalStmtResult EvaluateLoopBody(StmtResult &Result, EvalInfo &Info,
3873  const Stmt *Body,
3874  const SwitchCase *Case = nullptr) {
3875  BlockScopeRAII Scope(Info);
3876  switch (EvalStmtResult ESR = EvaluateStmt(Result, Info, Body, Case)) {
3877  case ESR_Break:
3878  return ESR_Succeeded;
3879  case ESR_Succeeded:
3880  case ESR_Continue:
3881  return ESR_Continue;
3882  case ESR_Failed:
3883  case ESR_Returned:
3884  case ESR_CaseNotFound:
3885  return ESR;
3886  }
3887  llvm_unreachable("Invalid EvalStmtResult!");
3888 }
3889 
3890 /// Evaluate a switch statement.
3891 static EvalStmtResult EvaluateSwitch(StmtResult &Result, EvalInfo &Info,
3892  const SwitchStmt *SS) {
3893  BlockScopeRAII Scope(Info);
3894 
3895  // Evaluate the switch condition.
3896  APSInt Value;
3897  {
3898  FullExpressionRAII Scope(Info);
3899  if (const Stmt *Init = SS->getInit()) {
3900  EvalStmtResult ESR = EvaluateStmt(Result, Info, Init);
3901  if (ESR != ESR_Succeeded)
3902  return ESR;
3903  }
3904  if (SS->getConditionVariable() &&
3905  !EvaluateDecl(Info, SS->getConditionVariable()))
3906  return ESR_Failed;
3907  if (!EvaluateInteger(SS->getCond(), Value, Info))
3908  return ESR_Failed;
3909  }
3910 
3911  // Find the switch case corresponding to the value of the condition.
3912  // FIXME: Cache this lookup.
3913  const SwitchCase *Found = nullptr;
3914  for (const SwitchCase *SC = SS->getSwitchCaseList(); SC;
3915  SC = SC->getNextSwitchCase()) {
3916  if (isa<DefaultStmt>(SC)) {
3917  Found = SC;
3918  continue;
3919  }
3920 
3921  const CaseStmt *CS = cast<CaseStmt>(SC);
3922  APSInt LHS = CS->getLHS()->EvaluateKnownConstInt(Info.Ctx);
3923  APSInt RHS = CS->getRHS() ? CS->getRHS()->EvaluateKnownConstInt(Info.Ctx)
3924  : LHS;
3925  if (LHS <= Value && Value <= RHS) {
3926  Found = SC;
3927  break;
3928  }
3929  }
3930 
3931  if (!Found)
3932  return ESR_Succeeded;
3933 
3934  // Search the switch body for the switch case and evaluate it from there.
3935  switch (EvalStmtResult ESR = EvaluateStmt(Result, Info, SS->getBody(), Found)) {
3936  case ESR_Break:
3937  return ESR_Succeeded;
3938  case ESR_Succeeded:
3939  case ESR_Continue:
3940  case ESR_Failed:
3941  case ESR_Returned:
3942  return ESR;
3943  case ESR_CaseNotFound:
3944  // This can only happen if the switch case is nested within a statement
3945  // expression. We have no intention of supporting that.
3946  Info.FFDiag(Found->getLocStart(), diag::note_constexpr_stmt_expr_unsupported);
3947  return ESR_Failed;
3948  }
3949  llvm_unreachable("Invalid EvalStmtResult!");
3950 }
3951 
3952 // Evaluate a statement.
3953 static EvalStmtResult EvaluateStmt(StmtResult &Result, EvalInfo &Info,
3954  const Stmt *S, const SwitchCase *Case) {
3955  if (!Info.nextStep(S))
3956  return ESR_Failed;
3957 
3958  // If we're hunting down a 'case' or 'default' label, recurse through
3959  // substatements until we hit the label.
3960  if (Case) {
3961  // FIXME: We don't start the lifetime of objects whose initialization we
3962  // jump over. However, such objects must be of class type with a trivial
3963  // default constructor that initialize all subobjects, so must be empty,
3964  // so this almost never matters.
3965  switch (S->getStmtClass()) {
3966  case Stmt::CompoundStmtClass:
3967  // FIXME: Precompute which substatement of a compound statement we
3968  // would jump to, and go straight there rather than performing a
3969  // linear scan each time.
3970  case Stmt::LabelStmtClass:
3971  case Stmt::AttributedStmtClass:
3972  case Stmt::DoStmtClass:
3973  break;
3974 
3975  case Stmt::CaseStmtClass:
3976  case Stmt::DefaultStmtClass:
3977  if (Case == S)
3978  Case = nullptr;
3979  break;
3980 
3981  case Stmt::IfStmtClass: {
3982  // FIXME: Precompute which side of an 'if' we would jump to, and go
3983  // straight there rather than scanning both sides.
3984  const IfStmt *IS = cast<IfStmt>(S);
3985 
3986  // Wrap the evaluation in a block scope, in case it's a DeclStmt
3987  // preceded by our switch label.
3988  BlockScopeRAII Scope(Info);
3989 
3990  EvalStmtResult ESR = EvaluateStmt(Result, Info, IS->getThen(), Case);
3991  if (ESR != ESR_CaseNotFound || !IS->getElse())
3992  return ESR;
3993  return EvaluateStmt(Result, Info, IS->getElse(), Case);
3994  }
3995 
3996  case Stmt::WhileStmtClass: {
3997  EvalStmtResult ESR =
3998  EvaluateLoopBody(Result, Info, cast<WhileStmt>(S)->getBody(), Case);
3999  if (ESR != ESR_Continue)
4000  return ESR;
4001  break;
4002  }
4003 
4004  case Stmt::ForStmtClass: {
4005  const ForStmt *FS = cast<ForStmt>(S);
4006  EvalStmtResult ESR =
4007  EvaluateLoopBody(Result, Info, FS->getBody(), Case);
4008  if (ESR != ESR_Continue)
4009  return ESR;
4010  if (FS->getInc()) {
4011  FullExpressionRAII IncScope(Info);
4012  if (!EvaluateIgnoredValue(Info, FS->getInc()))
4013  return ESR_Failed;
4014  }
4015  break;
4016  }
4017 
4018  case Stmt::DeclStmtClass:
4019  // FIXME: If the variable has initialization that can't be jumped over,
4020  // bail out of any immediately-surrounding compound-statement too.
4021  default:
4022  return ESR_CaseNotFound;
4023  }
4024  }
4025 
4026  switch (S->getStmtClass()) {
4027  default:
4028  if (const Expr *E = dyn_cast<Expr>(S)) {
4029  // Don't bother evaluating beyond an expression-statement which couldn't
4030  // be evaluated.
4031  FullExpressionRAII Scope(Info);
4032  if (!EvaluateIgnoredValue(Info, E))
4033  return ESR_Failed;
4034  return ESR_Succeeded;
4035  }
4036 
4037  Info.FFDiag(S->getLocStart());
4038  return ESR_Failed;
4039 
4040  case Stmt::NullStmtClass:
4041  return ESR_Succeeded;
4042 
4043  case Stmt::DeclStmtClass: {
4044  const DeclStmt *DS = cast<DeclStmt>(S);
4045  for (const auto *DclIt : DS->decls()) {
4046  // Each declaration initialization is its own full-expression.
4047  // FIXME: This isn't quite right; if we're performing aggregate
4048  // initialization, each braced subexpression is its own full-expression.
4049  FullExpressionRAII Scope(Info);
4050  if (!EvaluateDecl(Info, DclIt) && !Info.noteFailure())
4051  return ESR_Failed;
4052  }
4053  return ESR_Succeeded;
4054  }
4055 
4056  case Stmt::ReturnStmtClass: {
4057  const Expr *RetExpr = cast<ReturnStmt>(S)->getRetValue();
4058  FullExpressionRAII Scope(Info);
4059  if (RetExpr &&
4060  !(Result.Slot
4061  ? EvaluateInPlace(Result.Value, Info, *Result.Slot, RetExpr)
4062  : Evaluate(Result.Value, Info, RetExpr)))
4063  return ESR_Failed;
4064  return ESR_Returned;
4065  }
4066 
4067  case Stmt::CompoundStmtClass: {
4068  BlockScopeRAII Scope(Info);
4069 
4070  const CompoundStmt *CS = cast<CompoundStmt>(S);
4071  for (const auto *BI : CS->body()) {
4072  EvalStmtResult ESR = EvaluateStmt(Result, Info, BI, Case);
4073  if (ESR == ESR_Succeeded)
4074  Case = nullptr;
4075  else if (ESR != ESR_CaseNotFound)
4076  return ESR;
4077  }
4078  return Case ? ESR_CaseNotFound : ESR_Succeeded;
4079  }
4080 
4081  case Stmt::IfStmtClass: {
4082  const IfStmt *IS = cast<IfStmt>(S);
4083 
4084  // Evaluate the condition, as either a var decl or as an expression.
4085  BlockScopeRAII Scope(Info);
4086  if (const Stmt *Init = IS->getInit()) {
4087  EvalStmtResult ESR = EvaluateStmt(Result, Info, Init);
4088  if (ESR != ESR_Succeeded)
4089  return ESR;
4090  }
4091  bool Cond;
4092  if (!EvaluateCond(Info, IS->getConditionVariable(), IS->getCond(), Cond))
4093  return ESR_Failed;
4094 
4095  if (const Stmt *SubStmt = Cond ? IS->getThen() : IS->getElse()) {
4096  EvalStmtResult ESR = EvaluateStmt(Result, Info, SubStmt);
4097  if (ESR != ESR_Succeeded)
4098  return ESR;
4099  }
4100  return ESR_Succeeded;
4101  }
4102 
4103  case Stmt::WhileStmtClass: {
4104  const WhileStmt *WS = cast<WhileStmt>(S);
4105  while (true) {
4106  BlockScopeRAII Scope(Info);
4107  bool Continue;
4108  if (!EvaluateCond(Info, WS->getConditionVariable(), WS->getCond(),
4109  Continue))
4110  return ESR_Failed;
4111  if (!Continue)
4112  break;
4113 
4114  EvalStmtResult ESR = EvaluateLoopBody(Result, Info, WS->getBody());
4115  if (ESR != ESR_Continue)
4116  return ESR;
4117  }
4118  return ESR_Succeeded;
4119  }
4120 
4121  case Stmt::DoStmtClass: {
4122  const DoStmt *DS = cast<DoStmt>(S);
4123  bool Continue;
4124  do {
4125  EvalStmtResult ESR = EvaluateLoopBody(Result, Info, DS->getBody(), Case);
4126  if (ESR != ESR_Continue)
4127  return ESR;
4128  Case = nullptr;
4129 
4130  FullExpressionRAII CondScope(Info);
4131  if (!EvaluateAsBooleanCondition(DS->getCond(), Continue, Info))
4132  return ESR_Failed;
4133  } while (Continue);
4134  return ESR_Succeeded;
4135  }
4136 
4137  case Stmt::ForStmtClass: {
4138  const ForStmt *FS = cast<ForStmt>(S);
4139  BlockScopeRAII Scope(Info);
4140  if (FS->getInit()) {
4141  EvalStmtResult ESR = EvaluateStmt(Result, Info, FS->getInit());
4142  if (ESR != ESR_Succeeded)
4143  return ESR;
4144  }
4145  while (true) {
4146  BlockScopeRAII Scope(Info);
4147  bool Continue = true;
4148  if (FS->getCond() && !EvaluateCond(Info, FS->getConditionVariable(),
4149  FS->getCond(), Continue))
4150  return ESR_Failed;
4151  if (!Continue)
4152  break;
4153 
4154  EvalStmtResult ESR = EvaluateLoopBody(Result, Info, FS->getBody());
4155  if (ESR != ESR_Continue)
4156  return ESR;
4157 
4158  if (FS->getInc()) {
4159  FullExpressionRAII IncScope(Info);
4160  if (!EvaluateIgnoredValue(Info, FS->getInc()))
4161  return ESR_Failed;
4162  }
4163  }
4164  return ESR_Succeeded;
4165  }
4166 
4167  case Stmt::CXXForRangeStmtClass: {
4168  const CXXForRangeStmt *FS = cast<CXXForRangeStmt>(S);
4169  BlockScopeRAII Scope(Info);
4170 
4171  // Initialize the __range variable.
4172  EvalStmtResult ESR = EvaluateStmt(Result, Info, FS->getRangeStmt());
4173  if (ESR != ESR_Succeeded)
4174  return ESR;
4175 
4176  // Create the __begin and __end iterators.
4177  ESR = EvaluateStmt(Result, Info, FS->getBeginStmt());
4178  if (ESR != ESR_Succeeded)
4179  return ESR;
4180  ESR = EvaluateStmt(Result, Info, FS->getEndStmt());
4181  if (ESR != ESR_Succeeded)
4182  return ESR;
4183 
4184  while (true) {
4185  // Condition: __begin != __end.
4186  {
4187  bool Continue = true;
4188  FullExpressionRAII CondExpr(Info);
4189  if (!EvaluateAsBooleanCondition(FS->getCond(), Continue, Info))
4190  return ESR_Failed;
4191  if (!Continue)
4192  break;
4193  }
4194 
4195  // User's variable declaration, initialized by *__begin.
4196  BlockScopeRAII InnerScope(Info);
4197  ESR = EvaluateStmt(Result, Info, FS->getLoopVarStmt());
4198  if (ESR != ESR_Succeeded)
4199  return ESR;
4200 
4201  // Loop body.
4202  ESR = EvaluateLoopBody(Result, Info, FS->getBody());
4203  if (ESR != ESR_Continue)
4204  return ESR;
4205 
4206  // Increment: ++__begin
4207  if (!EvaluateIgnoredValue(Info, FS->getInc()))
4208  return ESR_Failed;
4209  }
4210 
4211  return ESR_Succeeded;
4212  }
4213 
4214  case Stmt::SwitchStmtClass:
4215  return EvaluateSwitch(Result, Info, cast<SwitchStmt>(S));
4216 
4217  case Stmt::ContinueStmtClass:
4218  return ESR_Continue;
4219 
4220  case Stmt::BreakStmtClass:
4221  return ESR_Break;
4222 
4223  case Stmt::LabelStmtClass:
4224  return EvaluateStmt(Result, Info, cast<LabelStmt>(S)->getSubStmt(), Case);
4225 
4226  case Stmt::AttributedStmtClass:
4227  // As a general principle, C++11 attributes can be ignored without
4228  // any semantic impact.
4229  return EvaluateStmt(Result, Info, cast<AttributedStmt>(S)->getSubStmt(),
4230  Case);
4231 
4232  case Stmt::CaseStmtClass:
4233  case Stmt::DefaultStmtClass:
4234  return EvaluateStmt(Result, Info, cast<SwitchCase>(S)->getSubStmt(), Case);
4235  }
4236 }
4237 
4238 /// CheckTrivialDefaultConstructor - Check whether a constructor is a trivial
4239 /// default constructor. If so, we'll fold it whether or not it's marked as
4240 /// constexpr. If it is marked as constexpr, we will never implicitly define it,
4241 /// so we need special handling.
4242 static bool CheckTrivialDefaultConstructor(EvalInfo &Info, SourceLocation Loc,
4243  const CXXConstructorDecl *CD,
4244  bool IsValueInitialization) {
4245  if (!CD->isTrivial() || !CD->isDefaultConstructor())
4246  return false;
4247 
4248  // Value-initialization does not call a trivial default constructor, so such a
4249  // call is a core constant expression whether or not the constructor is
4250  // constexpr.
4251  if (!CD->isConstexpr() && !IsValueInitialization) {
4252  if (Info.getLangOpts().CPlusPlus11) {
4253  // FIXME: If DiagDecl is an implicitly-declared special member function,
4254  // we should be much more explicit about why it's not constexpr.
4255  Info.CCEDiag(Loc, diag::note_constexpr_invalid_function, 1)
4256  << /*IsConstexpr*/0 << /*IsConstructor*/1 << CD;
4257  Info.Note(CD->getLocation(), diag::note_declared_at);
4258  } else {
4259  Info.CCEDiag(Loc, diag::note_invalid_subexpr_in_const_expr);
4260  }
4261  }
4262  return true;
4263 }
4264 
4265 /// CheckConstexprFunction - Check that a function can be called in a constant
4266 /// expression.
4267 static bool CheckConstexprFunction(EvalInfo &Info, SourceLocation CallLoc,
4268  const FunctionDecl *Declaration,
4269  const FunctionDecl *Definition,
4270  const Stmt *Body) {
4271  // Potential constant expressions can contain calls to declared, but not yet
4272  // defined, constexpr functions.
4273  if (Info.checkingPotentialConstantExpression() && !Definition &&
4274  Declaration->isConstexpr())
4275  return false;
4276 
4277  // Bail out with no diagnostic if the function declaration itself is invalid.
4278  // We will have produced a relevant diagnostic while parsing it.
4279  if (Declaration->isInvalidDecl())
4280  return false;
4281 
4282  // Can we evaluate this function call?
4283  if (Definition && Definition->isConstexpr() &&
4284  !Definition->isInvalidDecl() && Body)
4285  return true;
4286 
4287  if (Info.getLangOpts().CPlusPlus11) {
4288  const FunctionDecl *DiagDecl = Definition ? Definition : Declaration;
4289 
4290  // If this function is not constexpr because it is an inherited
4291  // non-constexpr constructor, diagnose that directly.
4292  auto *CD = dyn_cast<CXXConstructorDecl>(DiagDecl);
4293  if (CD && CD->isInheritingConstructor()) {
4294  auto *Inherited = CD->getInheritedConstructor().getConstructor();
4295  if (!Inherited->isConstexpr())
4296  DiagDecl = CD = Inherited;
4297  }
4298 
4299  // FIXME: If DiagDecl is an implicitly-declared special member function
4300  // or an inheriting constructor, we should be much more explicit about why
4301  // it's not constexpr.
4302  if (CD && CD->isInheritingConstructor())
4303  Info.FFDiag(CallLoc, diag::note_constexpr_invalid_inhctor, 1)
4304  << CD->getInheritedConstructor().getConstructor()->getParent();
4305  else
4306  Info.FFDiag(CallLoc, diag::note_constexpr_invalid_function, 1)
4307  << DiagDecl->isConstexpr() << (bool)CD << DiagDecl;
4308  Info.Note(DiagDecl->getLocation(), diag::note_declared_at);
4309  } else {
4310  Info.FFDiag(CallLoc, diag::note_invalid_subexpr_in_const_expr);
4311  }
4312  return false;
4313 }
4314 
4315 /// Determine if a class has any fields that might need to be copied by a
4316 /// trivial copy or move operation.
4317 static bool hasFields(const CXXRecordDecl *RD) {
4318  if (!RD || RD->isEmpty())
4319  return false;
4320  for (auto *FD : RD->fields()) {
4321  if (FD->isUnnamedBitfield())
4322  continue;
4323  return true;
4324  }
4325  for (auto &Base : RD->bases())
4326  if (hasFields(Base.getType()->getAsCXXRecordDecl()))
4327  return true;
4328  return false;
4329 }
4330 
4331 namespace {
4332 typedef SmallVector<APValue, 8> ArgVector;
4333 }
4334 
4335 /// EvaluateArgs - Evaluate the arguments to a function call.
4336 static bool EvaluateArgs(ArrayRef<const Expr*> Args, ArgVector &ArgValues,
4337  EvalInfo &Info) {
4338  bool Success = true;
4339  for (ArrayRef<const Expr*>::iterator I = Args.begin(), E = Args.end();
4340  I != E; ++I) {
4341  if (!Evaluate(ArgValues[I - Args.begin()], Info, *I)) {
4342  // If we're checking for a potential constant expression, evaluate all
4343  // initializers even if some of them fail.
4344  if (!Info.noteFailure())
4345  return false;
4346  Success = false;
4347  }
4348  }
4349  return Success;
4350 }
4351 
4352 /// Evaluate a function call.
4354  const FunctionDecl *Callee, const LValue *This,
4355  ArrayRef<const Expr*> Args, const Stmt *Body,
4356  EvalInfo &Info, APValue &Result,
4357  const LValue *ResultSlot) {
4358  ArgVector ArgValues(Args.size());
4359  if (!EvaluateArgs(Args, ArgValues, Info))
4360  return false;
4361 
4362  if (!Info.CheckCallLimit(CallLoc))
4363  return false;
4364 
4365  CallStackFrame Frame(Info, CallLoc, Callee, This, ArgValues.data());
4366 
4367  // For a trivial copy or move assignment, perform an APValue copy. This is
4368  // essential for unions, where the operations performed by the assignment
4369  // operator cannot be represented as statements.
4370  //
4371  // Skip this for non-union classes with no fields; in that case, the defaulted
4372  // copy/move does not actually read the object.
4373  const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(Callee);
4374  if (MD && MD->isDefaulted() &&
4375  (MD->getParent()->isUnion() ||
4376  (MD->isTrivial() && hasFields(MD->getParent())))) {
4377  assert(This &&
4378  (MD->isCopyAssignmentOperator() || MD->isMoveAssignmentOperator()));
4379  LValue RHS;
4380  RHS.setFrom(Info.Ctx, ArgValues[0]);
4381  APValue RHSValue;
4382  if (!handleLValueToRValueConversion(Info, Args[0], Args[0]->getType(),
4383  RHS, RHSValue))
4384  return false;
4385  if (!handleAssignment(Info, Args[0], *This, MD->getThisType(Info.Ctx),
4386  RHSValue))
4387  return false;
4388  This->moveInto(Result);
4389  return true;
4390  } else if (MD && isLambdaCallOperator(MD)) {
4391  // We're in a lambda; determine the lambda capture field maps unless we're
4392  // just constexpr checking a lambda's call operator. constexpr checking is
4393  // done before the captures have been added to the closure object (unless
4394  // we're inferring constexpr-ness), so we don't have access to them in this
4395  // case. But since we don't need the captures to constexpr check, we can
4396  // just ignore them.
4397  if (!Info.checkingPotentialConstantExpression())
4398  MD->getParent()->getCaptureFields(Frame.LambdaCaptureFields,
4399  Frame.LambdaThisCaptureField);
4400  }
4401 
4402  StmtResult Ret = {Result, ResultSlot};
4403  EvalStmtResult ESR = EvaluateStmt(Ret, Info, Body);
4404  if (ESR == ESR_Succeeded) {
4405  if (Callee->getReturnType()->isVoidType())
4406  return true;
4407  Info.FFDiag(Callee->getLocEnd(), diag::note_constexpr_no_return);
4408  }
4409  return ESR == ESR_Returned;
4410 }
4411 
4412 /// Evaluate a constructor call.
4413 static bool HandleConstructorCall(const Expr *E, const LValue &This,
4414  APValue *ArgValues,
4415  const CXXConstructorDecl *Definition,
4416  EvalInfo &Info, APValue &Result) {
4417  SourceLocation CallLoc = E->getExprLoc();
4418  if (!Info.CheckCallLimit(CallLoc))
4419  return false;
4420 
4421  const CXXRecordDecl *RD = Definition->getParent();
4422  if (RD->getNumVBases()) {
4423  Info.FFDiag(CallLoc, diag::note_constexpr_virtual_base) << RD;
4424  return false;
4425  }
4426 
4427  EvalInfo::EvaluatingConstructorRAII EvalObj(
4428  Info, {This.getLValueBase(),
4429  {This.getLValueCallIndex(), This.getLValueVersion()}});
4430  CallStackFrame Frame(Info, CallLoc, Definition, &This, ArgValues);
4431 
4432  // FIXME: Creating an APValue just to hold a nonexistent return value is
4433  // wasteful.
4434  APValue RetVal;
4435  StmtResult Ret = {RetVal, nullptr};
4436 
4437  // If it's a delegating constructor, delegate.
4438  if (Definition->isDelegatingConstructor()) {
4440  {
4441  FullExpressionRAII InitScope(Info);
4442  if (!EvaluateInPlace(Result, Info, This, (*I)->getInit()))
4443  return false;
4444  }
4445  return EvaluateStmt(Ret, Info, Definition->getBody()) != ESR_Failed;
4446  }
4447 
4448  // For a trivial copy or move constructor, perform an APValue copy. This is
4449  // essential for unions (or classes with anonymous union members), where the
4450  // operations performed by the constructor cannot be represented by
4451  // ctor-initializers.
4452  //
4453  // Skip this for empty non-union classes; we should not perform an
4454  // lvalue-to-rvalue conversion on them because their copy constructor does not
4455  // actually read them.
4456  if (Definition->isDefaulted() && Definition->isCopyOrMoveConstructor() &&
4457  (Definition->getParent()->isUnion() ||
4458  (Definition->isTrivial() && hasFields(Definition->getParent())))) {
4459  LValue RHS;
4460  RHS.setFrom(Info.Ctx, ArgValues[0]);
4462  Info, E, Definition->getParamDecl(0)->getType().getNonReferenceType(),
4463  RHS, Result);
4464  }
4465 
4466  // Reserve space for the struct members.
4467  if (!RD->isUnion() && Result.isUninit())
4468  Result = APValue(APValue::UninitStruct(), RD->getNumBases(),
4469  std::distance(RD->field_begin(), RD->field_end()));
4470 
4471  if (RD->isInvalidDecl()) return false;
4472  const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
4473 
4474  // A scope for temporaries lifetime-extended by reference members.
4475  BlockScopeRAII LifetimeExtendedScope(Info);
4476 
4477  bool Success = true;
4478  unsigned BasesSeen = 0;
4479 #ifndef NDEBUG
4481 #endif
4482  for (const auto *I : Definition->inits()) {
4483  LValue Subobject = This;
4484  LValue SubobjectParent = This;
4485  APValue *Value = &Result;
4486 
4487  // Determine the subobject to initialize.
4488  FieldDecl *FD = nullptr;
4489  if (I->isBaseInitializer()) {
4490  QualType BaseType(I->getBaseClass(), 0);
4491 #ifndef NDEBUG
4492  // Non-virtual base classes are initialized in the order in the class
4493  // definition. We have already checked for virtual base classes.
4494  assert(!BaseIt->isVirtual() && "virtual base for literal type");
4495  assert(Info.Ctx.hasSameType(BaseIt->getType(), BaseType) &&
4496  "base class initializers not in expected order");
4497  ++BaseIt;
4498 #endif
4499  if (!HandleLValueDirectBase(Info, I->getInit(), Subobject, RD,
4500  BaseType->getAsCXXRecordDecl(), &Layout))
4501  return false;
4502  Value = &Result.getStructBase(BasesSeen++);
4503  } else if ((FD = I->getMember())) {
4504  if (!HandleLValueMember(Info, I->getInit(), Subobject, FD, &Layout))
4505  return false;
4506  if (RD->isUnion()) {
4507  Result = APValue(FD);
4508  Value = &Result.getUnionValue();
4509  } else {
4510  Value = &Result.getStructField(FD->getFieldIndex());
4511  }
4512  } else if (IndirectFieldDecl *IFD = I->getIndirectMember()) {
4513  // Walk the indirect field decl's chain to find the object to initialize,
4514  // and make sure we've initialized every step along it.
4515  auto IndirectFieldChain = IFD->chain();
4516  for (auto *C : IndirectFieldChain) {
4517  FD = cast<FieldDecl>(C);
4518  CXXRecordDecl *CD = cast<CXXRecordDecl>(FD->getParent());
4519  // Switch the union field if it differs. This happens if we had
4520  // preceding zero-initialization, and we're now initializing a union
4521  // subobject other than the first.
4522  // FIXME: In this case, the values of the other subobjects are
4523  // specified, since zero-initialization sets all padding bits to zero.
4524  if (Value->isUninit() ||
4525  (Value->isUnion() && Value->getUnionField() != FD)) {
4526  if (CD->isUnion())
4527  *Value = APValue(FD);
4528  else
4529  *Value = APValue(APValue::UninitStruct(), CD->getNumBases(),
4530  std::distance(CD->field_begin(), CD->field_end()));
4531  }
4532  // Store Subobject as its parent before updating it for the last element
4533  // in the chain.
4534  if (C == IndirectFieldChain.back())
4535  SubobjectParent = Subobject;
4536  if (!HandleLValueMember(Info, I->getInit(), Subobject, FD))
4537  return false;
4538  if (CD->isUnion())
4539  Value = &Value->getUnionValue();
4540  else
4541  Value = &Value->getStructField(FD->getFieldIndex());
4542  }
4543  } else {
4544  llvm_unreachable("unknown base initializer kind");
4545  }
4546 
4547  // Need to override This for implicit field initializers as in this case
4548  // This refers to innermost anonymous struct/union containing initializer,
4549  // not to currently constructed class.
4550  const Expr *Init = I->getInit();
4551  ThisOverrideRAII ThisOverride(*Info.CurrentCall, &SubobjectParent,
4552  isa<CXXDefaultInitExpr>(Init));
4553  FullExpressionRAII InitScope(Info);
4554  if (!EvaluateInPlace(*Value, Info, Subobject, Init) ||
4555  (FD && FD->isBitField() &&
4556  !truncateBitfieldValue(Info, Init, *Value, FD))) {
4557  // If we're checking for a potential constant expression, evaluate all
4558  // initializers even if some of them fail.
4559  if (!Info.noteFailure())
4560  return false;
4561  Success = false;
4562  }
4563  }
4564 
4565  return Success &&
4566  EvaluateStmt(Ret, Info, Definition->getBody()) != ESR_Failed;
4567 }
4568 
4569 static bool HandleConstructorCall(const Expr *E, const LValue &This,
4570  ArrayRef<const Expr*> Args,
4571  const CXXConstructorDecl *Definition,
4572  EvalInfo &Info, APValue &Result) {
4573  ArgVector ArgValues(Args.size());
4574  if (!EvaluateArgs(Args, ArgValues, Info))
4575  return false;
4576 
4577  return HandleConstructorCall(E, This, ArgValues.data(), Definition,
4578  Info, Result);
4579 }
4580 
4581 //===----------------------------------------------------------------------===//
4582 // Generic Evaluation
4583 //===----------------------------------------------------------------------===//
4584 namespace {
4585 
4586 template <class Derived>
4587 class ExprEvaluatorBase
4588  : public ConstStmtVisitor<Derived, bool> {
4589 private:
4590  Derived &getDerived() { return static_cast<Derived&>(*this); }
4591  bool DerivedSuccess(const APValue &V, const Expr *E) {
4592  return getDerived().Success(V, E);
4593  }
4594  bool DerivedZeroInitialization(const Expr *E) {
4595  return getDerived().ZeroInitialization(E);
4596  }
4597 
4598  // Check whether a conditional operator with a non-constant condition is a
4599  // potential constant expression. If neither arm is a potential constant
4600  // expression, then the conditional operator is not either.
4601  template<typename ConditionalOperator>
4602  void CheckPotentialConstantConditional(const ConditionalOperator *E) {
4603  assert(Info.checkingPotentialConstantExpression());
4604 
4605  // Speculatively evaluate both arms.
4607  {
4608  SpeculativeEvaluationRAII Speculate(Info, &Diag);
4609  StmtVisitorTy::Visit(E->getFalseExpr());
4610  if (Diag.empty())
4611  return;
4612  }
4613 
4614  {
4615  SpeculativeEvaluationRAII Speculate(Info, &Diag);
4616  Diag.clear();
4617  StmtVisitorTy::Visit(E->getTrueExpr());
4618  if (Diag.empty())
4619  return;
4620  }
4621 
4622  Error(E, diag::note_constexpr_conditional_never_const);
4623  }
4624 
4625 
4626  template<typename ConditionalOperator>
4627  bool HandleConditionalOperator(const ConditionalOperator *E) {
4628  bool BoolResult;
4629  if (!EvaluateAsBooleanCondition(E->getCond(), BoolResult, Info)) {
4630  if (Info.checkingPotentialConstantExpression() && Info.noteFailure()) {
4631  CheckPotentialConstantConditional(E);
4632  return false;
4633  }
4634  if (Info.noteFailure()) {
4635  StmtVisitorTy::Visit(E->getTrueExpr());
4636  StmtVisitorTy::Visit(E->getFalseExpr());
4637  }
4638  return false;
4639  }
4640 
4641  Expr *EvalExpr = BoolResult ? E->getTrueExpr() : E->getFalseExpr();
4642  return StmtVisitorTy::Visit(EvalExpr);
4643  }
4644 
4645 protected:
4646  EvalInfo &Info;
4647  typedef ConstStmtVisitor<Derived, bool> StmtVisitorTy;
4648  typedef ExprEvaluatorBase ExprEvaluatorBaseTy;
4649 
4650  OptionalDiagnostic CCEDiag(const Expr *E, diag::kind D) {
4651  return Info.CCEDiag(E, D);
4652  }
4653 
4654  bool ZeroInitialization(const Expr *E) { return Error(E); }
4655 
4656 public:
4657  ExprEvaluatorBase(EvalInfo &Info) : Info(Info) {}
4658 
4659  EvalInfo &getEvalInfo() { return Info; }
4660 
4661  /// Report an evaluation error. This should only be called when an error is
4662  /// first discovered. When propagating an error, just return false.
4663  bool Error(const Expr *E, diag::kind D) {
4664  Info.FFDiag(E, D);
4665  return false;
4666  }
4667  bool Error(const Expr *E) {
4668  return Error(E, diag::note_invalid_subexpr_in_const_expr);
4669  }
4670 
4671  bool VisitStmt(const Stmt *) {
4672  llvm_unreachable("Expression evaluator should not be called on stmts");
4673  }
4674  bool VisitExpr(const Expr *E) {
4675  return Error(E);
4676  }
4677 
4678  bool VisitParenExpr(const ParenExpr *E)
4679  { return StmtVisitorTy::Visit(E->getSubExpr()); }
4680  bool VisitUnaryExtension(const UnaryOperator *E)
4681  { return StmtVisitorTy::Visit(E->getSubExpr()); }
4682  bool VisitUnaryPlus(const UnaryOperator *E)
4683  { return StmtVisitorTy::Visit(E->getSubExpr()); }
4684  bool VisitChooseExpr(const ChooseExpr *E)
4685  { return StmtVisitorTy::Visit(E->getChosenSubExpr()); }
4686  bool VisitGenericSelectionExpr(const GenericSelectionExpr *E)
4687  { return StmtVisitorTy::Visit(E->getResultExpr()); }
4688  bool VisitSubstNonTypeTemplateParmExpr(const SubstNonTypeTemplateParmExpr *E)
4689  { return StmtVisitorTy::Visit(E->getReplacement()); }
4690  bool VisitCXXDefaultArgExpr(const CXXDefaultArgExpr *E) {
4691  TempVersionRAII RAII(*Info.CurrentCall);
4692  return StmtVisitorTy::Visit(E->getExpr());
4693  }
4694  bool VisitCXXDefaultInitExpr(const CXXDefaultInitExpr *E) {
4695  TempVersionRAII RAII(*Info.CurrentCall);
4696  // The initializer may not have been parsed yet, or might be erroneous.
4697  if (!E->getExpr())
4698  return Error(E);
4699  return StmtVisitorTy::Visit(E->getExpr());
4700  }
4701  // We cannot create any objects for which cleanups are required, so there is
4702  // nothing to do here; all cleanups must come from unevaluated subexpressions.
4703  bool VisitExprWithCleanups(const ExprWithCleanups *E)
4704  { return StmtVisitorTy::Visit(E->getSubExpr()); }
4705 
4706  bool VisitCXXReinterpretCastExpr(const CXXReinterpretCastExpr *E) {
4707  CCEDiag(E, diag::note_constexpr_invalid_cast) << 0;
4708  return static_cast<Derived*>(this)->VisitCastExpr(E);
4709  }
4710  bool VisitCXXDynamicCastExpr(const CXXDynamicCastExpr *E) {
4711  CCEDiag(E, diag::note_constexpr_invalid_cast) << 1;
4712  return static_cast<Derived*>(this)->VisitCastExpr(E);
4713  }
4714 
4715  bool VisitBinaryOperator(const BinaryOperator *E) {
4716  switch (E->getOpcode()) {
4717  default:
4718  return Error(E);
4719 
4720  case BO_Comma:
4721  VisitIgnoredValue(E->getLHS());
4722  return StmtVisitorTy::Visit(E->getRHS());
4723 
4724  case BO_PtrMemD:
4725  case BO_PtrMemI: {
4726  LValue Obj;
4727  if (!HandleMemberPointerAccess(Info, E, Obj))
4728  return false;
4729  APValue Result;
4730  if (!handleLValueToRValueConversion(Info, E, E->getType(), Obj, Result))
4731  return false;
4732  return DerivedSuccess(Result, E);
4733  }
4734  }
4735  }
4736 
4737  bool VisitBinaryConditionalOperator(const BinaryConditionalOperator *E) {
4738  // Evaluate and cache the common expression. We treat it as a temporary,
4739  // even though it's not quite the same thing.
4740  if (!Evaluate(Info.CurrentCall->createTemporary(E->getOpaqueValue(), false),
4741  Info, E->getCommon()))
4742  return false;
4743 
4744  return HandleConditionalOperator(E);
4745  }
4746 
4747  bool VisitConditionalOperator(const ConditionalOperator *E) {
4748  bool IsBcpCall = false;
4749  // If the condition (ignoring parens) is a __builtin_constant_p call,
4750  // the result is a constant expression if it can be folded without
4751  // side-effects. This is an important GNU extension. See GCC PR38377
4752  // for discussion.
4753  if (const CallExpr *CallCE =
4754  dyn_cast<CallExpr>(E->getCond()->IgnoreParenCasts()))
4755  if (CallCE->getBuiltinCallee() == Builtin::BI__builtin_constant_p)
4756  IsBcpCall = true;
4757 
4758  // Always assume __builtin_constant_p(...) ? ... : ... is a potential
4759  // constant expression; we can't check whether it's potentially foldable.
4760  if (Info.checkingPotentialConstantExpression() && IsBcpCall)
4761  return false;
4762 
4763  FoldConstant Fold(Info, IsBcpCall);
4764  if (!HandleConditionalOperator(E)) {
4765  Fold.keepDiagnostics();
4766  return false;
4767  }
4768 
4769  return true;
4770  }
4771 
4772  bool VisitOpaqueValueExpr(const OpaqueValueExpr *E) {
4773  if (APValue *Value = Info.CurrentCall->getCurrentTemporary(E))
4774  return DerivedSuccess(*Value, E);
4775 
4776  const Expr *Source = E->getSourceExpr();
4777  if (!Source)
4778  return Error(E);
4779  if (Source == E) { // sanity checking.
4780  assert(0 && "OpaqueValueExpr recursively refers to itself");
4781  return Error(E);
4782  }
4783  return StmtVisitorTy::Visit(Source);
4784  }
4785 
4786  bool VisitCallExpr(const CallExpr *E) {
4787  APValue Result;
4788  if (!handleCallExpr(E, Result, nullptr))
4789  return false;
4790  return DerivedSuccess(Result, E);
4791  }
4792 
4793  bool handleCallExpr(const CallExpr *E, APValue &Result,
4794  const LValue *ResultSlot) {
4795  const Expr *Callee = E->getCallee()->IgnoreParens();
4796  QualType CalleeType = Callee->getType();
4797 
4798  const FunctionDecl *FD = nullptr;
4799  LValue *This = nullptr, ThisVal;
4800  auto Args = llvm::makeArrayRef(E->getArgs(), E->getNumArgs());
4801  bool HasQualifier = false;
4802 
4803  // Extract function decl and 'this' pointer from the callee.
4804  if (CalleeType->isSpecificBuiltinType(BuiltinType::BoundMember)) {
4805  const ValueDecl *Member = nullptr;
4806  if (const MemberExpr *ME = dyn_cast<MemberExpr>(Callee)) {
4807  // Explicit bound member calls, such as x.f() or p->g();
4808  if (!EvaluateObjectArgument(Info, ME->getBase(), ThisVal))
4809  return false;
4810  Member = ME->getMemberDecl();
4811  This = &ThisVal;
4812  HasQualifier = ME->hasQualifier();
4813  } else if (const BinaryOperator *BE = dyn_cast<BinaryOperator>(Callee)) {
4814  // Indirect bound member calls ('.*' or '->*').
4815  Member = HandleMemberPointerAccess(Info, BE, ThisVal, false);
4816  if (!Member) return false;
4817  This = &ThisVal;
4818  } else
4819  return Error(Callee);
4820 
4821  FD = dyn_cast<FunctionDecl>(Member);
4822  if (!FD)
4823  return Error(Callee);
4824  } else if (CalleeType->isFunctionPointerType()) {
4825  LValue Call;
4826  if (!EvaluatePointer(Callee, Call, Info))
4827  return false;
4828 
4829  if (!Call.getLValueOffset().isZero())
4830  return Error(Callee);
4831  FD = dyn_cast_or_null<FunctionDecl>(
4832  Call.getLValueBase().dyn_cast<const ValueDecl*>());
4833  if (!FD)
4834  return Error(Callee);
4835  // Don't call function pointers which have been cast to some other type.
4836  // Per DR (no number yet), the caller and callee can differ in noexcept.
4837  if (!Info.Ctx.hasSameFunctionTypeIgnoringExceptionSpec(
4838  CalleeType->getPointeeType(), FD->getType())) {
4839  return Error(E);
4840  }
4841 
4842  // Overloaded operator calls to member functions are represented as normal
4843  // calls with '*this' as the first argument.
4844  const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD);
4845  if (MD && !MD->isStatic()) {
4846  // FIXME: When selecting an implicit conversion for an overloaded
4847  // operator delete, we sometimes try to evaluate calls to conversion
4848  // operators without a 'this' parameter!
4849  if (Args.empty())
4850  return Error(E);
4851 
4852  if (!EvaluateObjectArgument(Info, Args[0], ThisVal))
4853  return false;
4854  This = &ThisVal;
4855  Args = Args.slice(1);
4856  } else if (MD && MD->isLambdaStaticInvoker()) {
4857  // Map the static invoker for the lambda back to the call operator.
4858  // Conveniently, we don't have to slice out the 'this' argument (as is
4859  // being done for the non-static case), since a static member function
4860  // doesn't have an implicit argument passed in.
4861  const CXXRecordDecl *ClosureClass = MD->getParent();
4862  assert(
4863  ClosureClass->captures_begin() == ClosureClass->captures_end() &&
4864  "Number of captures must be zero for conversion to function-ptr");
4865 
4866  const CXXMethodDecl *LambdaCallOp =
4867  ClosureClass->getLambdaCallOperator();
4868 
4869  // Set 'FD', the function that will be called below, to the call
4870  // operator. If the closure object represents a generic lambda, find
4871  // the corresponding specialization of the call operator.
4872 
4873  if (ClosureClass->isGenericLambda()) {
4874  assert(MD->isFunctionTemplateSpecialization() &&
4875  "A generic lambda's static-invoker function must be a "
4876  "template specialization");
4878  FunctionTemplateDecl *CallOpTemplate =
4879  LambdaCallOp->getDescribedFunctionTemplate();
4880  void *InsertPos = nullptr;
4881  FunctionDecl *CorrespondingCallOpSpecialization =
4882  CallOpTemplate->findSpecialization(TAL->asArray(), InsertPos);
4883  assert(CorrespondingCallOpSpecialization &&
4884  "We must always have a function call operator specialization "
4885  "that corresponds to our static invoker specialization");
4886  FD = cast<CXXMethodDecl>(CorrespondingCallOpSpecialization);
4887  } else
4888  FD = LambdaCallOp;
4889  }
4890 
4891 
4892  } else
4893  return Error(E);
4894 
4895  if (This && !This->checkSubobject(Info, E, CSK_This))
4896  return false;
4897 
4898  // DR1358 allows virtual constexpr functions in some cases. Don't allow
4899  // calls to such functions in constant expressions.
4900  if (This && !HasQualifier &&
4901  isa<CXXMethodDecl>(FD) && cast<CXXMethodDecl>(FD)->isVirtual())
4902  return Error(E, diag::note_constexpr_virtual_call);
4903 
4904  const FunctionDecl *Definition = nullptr;
4905  Stmt *Body = FD->getBody(Definition);
4906 
4907  if (!CheckConstexprFunction(Info, E->getExprLoc(), FD, Definition, Body) ||
4908  !HandleFunctionCall(E->getExprLoc(), Definition, This, Args, Body, Info,
4909  Result, ResultSlot))
4910  return false;
4911 
4912  return true;
4913  }
4914 
4915  bool VisitCompoundLiteralExpr(const CompoundLiteralExpr *E) {
4916  return StmtVisitorTy::Visit(E->getInitializer());
4917  }
4918  bool VisitInitListExpr(const InitListExpr *E) {
4919  if (E->getNumInits() == 0)
4920  return DerivedZeroInitialization(E);
4921  if (E->getNumInits() == 1)
4922  return StmtVisitorTy::Visit(E->getInit(0));
4923  return Error(E);
4924  }
4925  bool VisitImplicitValueInitExpr(const ImplicitValueInitExpr *E) {
4926  return DerivedZeroInitialization(E);
4927  }
4928  bool VisitCXXScalarValueInitExpr(const CXXScalarValueInitExpr *E) {
4929  return DerivedZeroInitialization(E);
4930  }
4931  bool VisitCXXNullPtrLiteralExpr(const CXXNullPtrLiteralExpr *E) {
4932  return DerivedZeroInitialization(E);
4933  }
4934 
4935  /// A member expression where the object is a prvalue is itself a prvalue.
4936  bool VisitMemberExpr(const MemberExpr *E) {
4937  assert(!E->isArrow() && "missing call to bound member function?");
4938 
4939  APValue Val;
4940  if (!Evaluate(Val, Info, E->getBase()))
4941  return false;
4942 
4943  QualType BaseTy = E->getBase()->getType();
4944 
4945  const FieldDecl *FD = dyn_cast<FieldDecl>(E->getMemberDecl());
4946  if (!FD) return Error(E);
4947  assert(!FD->getType()->isReferenceType() && "prvalue reference?");
4948  assert(BaseTy->castAs<RecordType>()->getDecl()->getCanonicalDecl() ==
4949  FD->getParent()->getCanonicalDecl() && "record / field mismatch");
4950 
4951  CompleteObject Obj(&Val, BaseTy, true);
4952  SubobjectDesignator Designator(BaseTy);
4953  Designator.addDeclUnchecked(FD);
4954 
4955  APValue Result;
4956  return extractSubobject(Info, E, Obj, Designator, Result) &&
4957  DerivedSuccess(Result, E);
4958  }
4959 
4960  bool VisitCastExpr(const CastExpr *E) {
4961  switch (E->getCastKind()) {
4962  default:
4963  break;
4964 
4965  case CK_AtomicToNonAtomic: {
4966  APValue AtomicVal;
4967  // This does not need to be done in place even for class/array types:
4968  // atomic-to-non-atomic conversion implies copying the object
4969  // representation.
4970  if (!Evaluate(AtomicVal, Info, E->getSubExpr()))
4971  return false;
4972  return DerivedSuccess(AtomicVal, E);
4973  }
4974 
4975  case CK_NoOp:
4976  case CK_UserDefinedConversion:
4977  return StmtVisitorTy::Visit(E->getSubExpr());
4978 
4979  case CK_LValueToRValue: {
4980  LValue LVal;
4981  if (!EvaluateLValue(E->getSubExpr(), LVal, Info))
4982  return false;
4983  APValue RVal;
4984  // Note, we use the subexpression's type in order to retain cv-qualifiers.
4985  if (!handleLValueToRValueConversion(Info, E, E->getSubExpr()->getType(),
4986  LVal, RVal))
4987  return false;
4988  return DerivedSuccess(RVal, E);
4989  }
4990  }
4991 
4992  return Error(E);
4993  }
4994 
4995  bool VisitUnaryPostInc(const UnaryOperator *UO) {
4996  return VisitUnaryPostIncDec(UO);
4997  }
4998  bool VisitUnaryPostDec(const UnaryOperator *UO) {
4999  return VisitUnaryPostIncDec(UO);
5000  }
5001  bool VisitUnaryPostIncDec(const UnaryOperator *UO) {
5002  if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
5003  return Error(UO);
5004 
5005  LValue LVal;
5006  if (!EvaluateLValue(UO->getSubExpr(), LVal, Info))
5007  return false;
5008  APValue RVal;
5009  if (!handleIncDec(this->Info, UO, LVal, UO->getSubExpr()->getType(),
5010  UO->isIncrementOp(), &RVal))
5011  return false;
5012  return DerivedSuccess(RVal, UO);
5013  }
5014 
5015  bool VisitStmtExpr(const StmtExpr *E) {
5016  // We will have checked the full-expressions inside the statement expression
5017  // when they were completed, and don't need to check them again now.
5018  if (Info.checkingForOverflow())
5019  return Error(E);
5020 
5021  BlockScopeRAII Scope(Info);
5022  const CompoundStmt *CS = E->getSubStmt();
5023  if (CS->body_empty())
5024  return true;
5025 
5027  BE = CS->body_end();
5028  /**/; ++BI) {
5029  if (BI + 1 == BE) {
5030  const Expr *FinalExpr = dyn_cast<Expr>(*BI);
5031  if (!FinalExpr) {
5032  Info.FFDiag((*BI)->getLocStart(),
5033  diag::note_constexpr_stmt_expr_unsupported);
5034  return false;
5035  }
5036  return this->Visit(FinalExpr);
5037  }
5038 
5039  APValue ReturnValue;
5040  StmtResult Result = { ReturnValue, nullptr };
5041  EvalStmtResult ESR = EvaluateStmt(Result, Info, *BI);
5042  if (ESR != ESR_Succeeded) {
5043  // FIXME: If the statement-expression terminated due to 'return',
5044  // 'break', or 'continue', it would be nice to propagate that to
5045  // the outer statement evaluation rather than bailing out.
5046  if (ESR != ESR_Failed)
5047  Info.FFDiag((*BI)->getLocStart(),
5048  diag::note_constexpr_stmt_expr_unsupported);
5049  return false;
5050  }
5051  }
5052 
5053  llvm_unreachable("Return from function from the loop above.");
5054  }
5055 
5056  /// Visit a value which is evaluated, but whose value is ignored.
5057  void VisitIgnoredValue(const Expr *E) {
5058  EvaluateIgnoredValue(Info, E);
5059  }
5060 
5061  /// Potentially visit a MemberExpr's base expression.
5062  void VisitIgnoredBaseExpression(const Expr *E) {
5063  // While MSVC doesn't evaluate the base expression, it does diagnose the
5064  // presence of side-effecting behavior.
5065  if (Info.getLangOpts().MSVCCompat && !E->HasSideEffects(Info.Ctx))
5066  return;
5067  VisitIgnoredValue(E);
5068  }
5069 };
5070 
5071 } // namespace
5072 
5073 //===----------------------------------------------------------------------===//
5074 // Common base class for lvalue and temporary evaluation.
5075 //===----------------------------------------------------------------------===//
5076 namespace {
5077 template<class Derived>
5078 class LValueExprEvaluatorBase
5079  : public ExprEvaluatorBase<Derived> {
5080 protected:
5081  LValue &Result;
5082  bool InvalidBaseOK;
5083  typedef LValueExprEvaluatorBase LValueExprEvaluatorBaseTy;
5084  typedef ExprEvaluatorBase<Derived> ExprEvaluatorBaseTy;
5085 
5086  bool Success(APValue::LValueBase B) {
5087  Result.set(B);
5088  return true;
5089  }
5090 
5091  bool evaluatePointer(const Expr *E, LValue &Result) {
5092  return EvaluatePointer(E, Result, this->Info, InvalidBaseOK);
5093  }
5094 
5095 public:
5096  LValueExprEvaluatorBase(EvalInfo &Info, LValue &Result, bool InvalidBaseOK)
5097  : ExprEvaluatorBaseTy(Info), Result(Result),
5098  InvalidBaseOK(InvalidBaseOK) {}
5099 
5100  bool Success(const APValue &V, const Expr *E) {
5101  Result.setFrom(this->Info.Ctx, V);
5102  return true;
5103  }
5104 
5105  bool VisitMemberExpr(const MemberExpr *E) {
5106  // Handle non-static data members.
5107  QualType BaseTy;
5108  bool EvalOK;
5109  if (E->isArrow()) {
5110  EvalOK = evaluatePointer(E->getBase(), Result);
5111  BaseTy = E->getBase()->getType()->castAs<PointerType>()->getPointeeType();
5112  } else if (E->getBase()->isRValue()) {
5113  assert(E->getBase()->getType()->isRecordType());
5114  EvalOK = EvaluateTemporary(E->getBase(), Result, this->Info);
5115  BaseTy = E->getBase()->getType();
5116  } else {
5117  EvalOK = this->Visit(E->getBase());
5118  BaseTy = E->getBase()->getType();
5119  }
5120  if (!EvalOK) {
5121  if (!InvalidBaseOK)
5122  return false;
5123  Result.setInvalid(E);
5124  return true;
5125  }
5126 
5127  const ValueDecl *MD = E->getMemberDecl();
5128  if (const FieldDecl *FD = dyn_cast<FieldDecl>(E->getMemberDecl())) {
5129  assert(BaseTy->getAs<RecordType>()->getDecl()->getCanonicalDecl() ==
5130  FD->getParent()->getCanonicalDecl() && "record / field mismatch");
5131  (void)BaseTy;
5132  if (!HandleLValueMember(this->Info, E, Result, FD))
5133  return false;
5134  } else if (const IndirectFieldDecl *IFD = dyn_cast<IndirectFieldDecl>(MD)) {
5135  if (!HandleLValueIndirectMember(this->Info, E, Result, IFD))
5136  return false;
5137  } else
5138  return this->Error(E);
5139 
5140  if (MD->getType()->isReferenceType()) {
5141  APValue RefValue;
5142  if (!handleLValueToRValueConversion(this->Info, E, MD->getType(), Result,
5143  RefValue))
5144  return false;
5145  return Success(RefValue, E);
5146  }
5147  return true;
5148  }
5149 
5150  bool VisitBinaryOperator(const BinaryOperator *E) {
5151  switch (E->getOpcode()) {
5152  default:
5153  return ExprEvaluatorBaseTy::VisitBinaryOperator(E);
5154 
5155  case BO_PtrMemD:
5156  case BO_PtrMemI:
5157  return HandleMemberPointerAccess(this->Info, E, Result);
5158  }
5159  }
5160 
5161  bool VisitCastExpr(const CastExpr *E) {
5162  switch (E->getCastKind()) {
5163  default:
5164  return ExprEvaluatorBaseTy::VisitCastExpr(E);
5165 
5166  case CK_DerivedToBase:
5167  case CK_UncheckedDerivedToBase:
5168  if (!this->Visit(E->getSubExpr()))
5169  return false;
5170 
5171  // Now figure out the necessary offset to add to the base LV to get from
5172  // the derived class to the base class.
5173  return HandleLValueBasePath(this->Info, E, E->getSubExpr()->getType(),
5174  Result);
5175  }
5176  }
5177 };
5178 }
5179 
5180 //===----------------------------------------------------------------------===//
5181 // LValue Evaluation
5182 //
5183 // This is used for evaluating lvalues (in C and C++), xvalues (in C++11),
5184 // function designators (in C), decl references to void objects (in C), and
5185 // temporaries (if building with -Wno-address-of-temporary).
5186 //
5187 // LValue evaluation produces values comprising a base expression of one of the
5188 // following types:
5189 // - Declarations
5190 // * VarDecl
5191 // * FunctionDecl
5192 // - Literals
5193 // * CompoundLiteralExpr in C (and in global scope in C++)
5194 // * StringLiteral
5195 // * CXXTypeidExpr
5196 // * PredefinedExpr
5197 // * ObjCStringLiteralExpr
5198 // * ObjCEncodeExpr
5199 // * AddrLabelExpr
5200 // * BlockExpr
5201 // * CallExpr for a MakeStringConstant builtin
5202 // - Locals and temporaries
5203 // * MaterializeTemporaryExpr
5204 // * Any Expr, with a CallIndex indicating the function in which the temporary
5205 // was evaluated, for cases where the MaterializeTemporaryExpr is missing
5206 // from the AST (FIXME).
5207 // * A MaterializeTemporaryExpr that has static storage duration, with no
5208 // CallIndex, for a lifetime-extended temporary.
5209 // plus an offset in bytes.
5210 //===----------------------------------------------------------------------===//
5211 namespace {
5212 class LValueExprEvaluator
5213  : public LValueExprEvaluatorBase<LValueExprEvaluator> {
5214 public:
5215  LValueExprEvaluator(EvalInfo &Info, LValue &Result, bool InvalidBaseOK) :
5216  LValueExprEvaluatorBaseTy(Info, Result, InvalidBaseOK) {}
5217 
5218  bool VisitVarDecl(const Expr *E, const VarDecl *VD);
5219  bool VisitUnaryPreIncDec(const UnaryOperator *UO);
5220 
5221  bool VisitDeclRefExpr(const DeclRefExpr *E);
5222  bool VisitPredefinedExpr(const PredefinedExpr *E) { return Success(E); }
5223  bool VisitMaterializeTemporaryExpr(const MaterializeTemporaryExpr *E);
5224  bool VisitCompoundLiteralExpr(const CompoundLiteralExpr *E);
5225  bool VisitMemberExpr(const MemberExpr *E);
5226  bool VisitStringLiteral(const StringLiteral *E) { return Success(E); }
5227  bool VisitObjCEncodeExpr(const ObjCEncodeExpr *E) { return Success(E); }
5228  bool VisitCXXTypeidExpr(const CXXTypeidExpr *E);
5229  bool VisitCXXUuidofExpr(const CXXUuidofExpr *E);
5230  bool VisitArraySubscriptExpr(const ArraySubscriptExpr *E);
5231  bool VisitUnaryDeref(const UnaryOperator *E);
5232  bool VisitUnaryReal(const UnaryOperator *E);
5233  bool VisitUnaryImag(const UnaryOperator *E);
5234  bool VisitUnaryPreInc(const UnaryOperator *UO) {
5235  return VisitUnaryPreIncDec(UO);
5236  }
5237  bool VisitUnaryPreDec(const UnaryOperator *UO) {
5238  return VisitUnaryPreIncDec(UO);
5239  }
5240  bool VisitBinAssign(const BinaryOperator *BO);
5241  bool VisitCompoundAssignOperator(const CompoundAssignOperator *CAO);
5242 
5243  bool VisitCastExpr(const CastExpr *E) {
5244  switch (E->getCastKind()) {
5245  default:
5246  return LValueExprEvaluatorBaseTy::VisitCastExpr(E);
5247 
5248  case CK_LValueBitCast:
5249  this->CCEDiag(E, diag::note_constexpr_invalid_cast) << 2;
5250  if (!Visit(E->getSubExpr()))
5251  return false;
5252  Result.Designator.setInvalid();
5253  return true;
5254 
5255  case CK_BaseToDerived:
5256  if (!Visit(E->getSubExpr()))
5257  return false;
5258  return HandleBaseToDerivedCast(Info, E, Result);
5259  }
5260  }
5261 };
5262 } // end anonymous namespace
5263 
5264 /// Evaluate an expression as an lvalue. This can be legitimately called on
5265 /// expressions which are not glvalues, in three cases:
5266 /// * function designators in C, and
5267 /// * "extern void" objects
5268 /// * @selector() expressions in Objective-C
5269 static bool EvaluateLValue(const Expr *E, LValue &Result, EvalInfo &Info,
5270  bool InvalidBaseOK) {
5271  assert(E->isGLValue() || E->getType()->isFunctionType() ||
5272  E->getType()->isVoidType() || isa<ObjCSelectorExpr>(E));
5273  return LValueExprEvaluator(Info, Result, InvalidBaseOK).Visit(E);
5274 }
5275 
5276 bool LValueExprEvaluator::VisitDeclRefExpr(const DeclRefExpr *E) {
5277  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(E->getDecl()))
5278  return Success(FD);
5279  if (const VarDecl *VD = dyn_cast<VarDecl>(E->getDecl()))
5280  return VisitVarDecl(E, VD);
5281  if (const BindingDecl *BD = dyn_cast<BindingDecl>(E->getDecl()))
5282  return Visit(BD->getBinding());
5283  return Error(E);
5284 }
5285 
5286 
5287 bool LValueExprEvaluator::VisitVarDecl(const Expr *E, const VarDecl *VD) {
5288 
5289  // If we are within a lambda's call operator, check whether the 'VD' referred
5290  // to within 'E' actually represents a lambda-capture that maps to a
5291  // data-member/field within the closure object, and if so, evaluate to the
5292  // field or what the field refers to.
5293  if (Info.CurrentCall && isLambdaCallOperator(Info.CurrentCall->Callee) &&
5294  isa<DeclRefExpr>(E) &&
5295  cast<DeclRefExpr>(E)->refersToEnclosingVariableOrCapture()) {
5296  // We don't always have a complete capture-map when checking or inferring if
5297  // the function call operator meets the requirements of a constexpr function
5298  // - but we don't need to evaluate the captures to determine constexprness
5299  // (dcl.constexpr C++17).
5300  if (Info.checkingPotentialConstantExpression())
5301  return false;
5302 
5303  if (auto *FD = Info.CurrentCall->LambdaCaptureFields.lookup(VD)) {
5304  // Start with 'Result' referring to the complete closure object...
5305  Result = *Info.CurrentCall->This;
5306  // ... then update it to refer to the field of the closure object
5307  // that represents the capture.
5308  if (!HandleLValueMember(Info, E, Result, FD))
5309  return false;
5310  // And if the field is of reference type, update 'Result' to refer to what
5311  // the field refers to.
5312  if (FD->getType()->isReferenceType()) {
5313  APValue RVal;
5314  if (!handleLValueToRValueConversion(Info, E, FD->getType(), Result,
5315  RVal))
5316  return false;
5317  Result.setFrom(Info.Ctx, RVal);
5318  }
5319  return true;
5320  }
5321  }
5322  CallStackFrame *Frame = nullptr;
5323  if (VD->hasLocalStorage() && Info.CurrentCall->Index > 1) {
5324  // Only if a local variable was declared in the function currently being
5325  // evaluated, do we expect to be able to find its value in the current
5326  // frame. (Otherwise it was likely declared in an enclosing context and
5327  // could either have a valid evaluatable value (for e.g. a constexpr
5328  // variable) or be ill-formed (and trigger an appropriate evaluation
5329  // diagnostic)).
5330  if (Info.CurrentCall->Callee &&
5331  Info.CurrentCall->Callee->Equals(VD->getDeclContext())) {
5332  Frame = Info.CurrentCall;
5333  }
5334  }
5335 
5336  if (!VD->getType()->isReferenceType()) {
5337  if (Frame) {
5338  Result.set({VD, Frame->Index,
5339  Info.CurrentCall->getCurrentTemporaryVersion(VD)});
5340  return true;
5341  }
5342  return Success(VD);
5343  }
5344 
5345  APValue *V;
5346  if (!evaluateVarDeclInit(Info, E, VD, Frame, V, nullptr))
5347  return false;
5348  if (V->isUninit()) {
5349  if (!Info.checkingPotentialConstantExpression())
5350  Info.FFDiag(E, diag::note_constexpr_use_uninit_reference);
5351  return false;
5352  }
5353  return Success(*V, E);
5354 }
5355 
5356 bool LValueExprEvaluator::VisitMaterializeTemporaryExpr(
5357  const MaterializeTemporaryExpr *E) {
5358  // Walk through the expression to find the materialized temporary itself.
5359  SmallVector<const Expr *, 2> CommaLHSs;
5361  const Expr *Inner = E->GetTemporaryExpr()->
5362  skipRValueSubobjectAdjustments(CommaLHSs, Adjustments);
5363 
5364  // If we passed any comma operators, evaluate their LHSs.
5365  for (unsigned I = 0, N = CommaLHSs.size(); I != N; ++I)
5366  if (!EvaluateIgnoredValue(Info, CommaLHSs[I]))
5367  return false;
5368 
5369  // A materialized temporary with static storage duration can appear within the
5370  // result of a constant expression evaluation, so we need to preserve its
5371  // value for use outside this evaluation.
5372  APValue *Value;
5373  if (E->getStorageDuration() == SD_Static) {
5374  Value = Info.Ctx.getMaterializedTemporaryValue(E, true);
5375  *Value = APValue();
5376  Result.set(E);
5377  } else {
5379  *Info.CurrentCall);
5380  }
5381 
5382  QualType Type = Inner->getType();
5383 
5384  // Materialize the temporary itself.
5385  if (!EvaluateInPlace(*Value, Info, Result, Inner) ||
5386  (E->getStorageDuration() == SD_Static &&
5387  !CheckConstantExpression(Info, E->getExprLoc(), Type, *Value))) {
5388  *Value = APValue();
5389  return false;
5390  }
5391 
5392  // Adjust our lvalue to refer to the desired subobject.
5393  for (unsigned I = Adjustments.size(); I != 0; /**/) {
5394  --I;
5395  switch (Adjustments[I].Kind) {
5397  if (!HandleLValueBasePath(Info, Adjustments[I].DerivedToBase.BasePath,
5398  Type, Result))
5399  return false;
5400  Type = Adjustments[I].DerivedToBase.BasePath->getType();
5401  break;
5402 
5404  if (!HandleLValueMember(Info, E, Result, Adjustments[I].Field))
5405  return false;
5406  Type = Adjustments[I].Field->getType();
5407  break;
5408 
5410  if (!HandleMemberPointerAccess(this->Info, Type, Result,
5411  Adjustments[I].Ptr.RHS))
5412  return false;
5413  Type = Adjustments[I].Ptr.MPT->getPointeeType();
5414  break;
5415  }
5416  }
5417 
5418  return true;
5419 }
5420 
5421 bool
5422 LValueExprEvaluator::VisitCompoundLiteralExpr(const CompoundLiteralExpr *E) {
5423  assert((!Info.getLangOpts().CPlusPlus || E->isFileScope()) &&
5424  "lvalue compound literal in c++?");
5425  // Defer visiting the literal until the lvalue-to-rvalue conversion. We can
5426  // only see this when folding in C, so there's no standard to follow here.
5427  return Success(E);
5428 }
5429 
5430 bool LValueExprEvaluator::VisitCXXTypeidExpr(const CXXTypeidExpr *E) {
5431  if (!E->isPotentiallyEvaluated())
5432  return Success(E);
5433 
5434  Info.FFDiag(E, diag::note_constexpr_typeid_polymorphic)
5435  << E->getExprOperand()->getType()
5436  << E->getExprOperand()->getSourceRange();
5437  return false;
5438 }
5439 
5440 bool LValueExprEvaluator::VisitCXXUuidofExpr(const CXXUuidofExpr *E) {
5441  return Success(E);
5442 }
5443 
5444 bool LValueExprEvaluator::VisitMemberExpr(const MemberExpr *E) {
5445  // Handle static data members.
5446  if (const VarDecl *VD = dyn_cast<VarDecl>(E->getMemberDecl())) {
5447  VisitIgnoredBaseExpression(E->getBase());
5448  return VisitVarDecl(E, VD);
5449  }
5450 
5451  // Handle static member functions.
5452  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(E->getMemberDecl())) {
5453  if (MD->isStatic()) {
5454  VisitIgnoredBaseExpression(E->getBase());
5455  return Success(MD);
5456  }
5457  }
5458 
5459  // Handle non-static data members.
5460  return LValueExprEvaluatorBaseTy::VisitMemberExpr(E);
5461 }
5462 
5463 bool LValueExprEvaluator::VisitArraySubscriptExpr(const ArraySubscriptExpr *E) {
5464  // FIXME: Deal with vectors as array subscript bases.
5465  if (E->getBase()->getType()->isVectorType())
5466  return Error(E);
5467 
5468  bool Success = true;
5469  if (!evaluatePointer(E->getBase(), Result)) {
5470  if (!Info.noteFailure())
5471  return false;
5472  Success = false;
5473  }
5474 
5475  APSInt Index;
5476  if (!EvaluateInteger(E->getIdx(), Index, Info))
5477  return false;
5478 
5479  return Success &&
5480  HandleLValueArrayAdjustment(Info, E, Result, E->getType(), Index);
5481 }
5482 
5483 bool LValueExprEvaluator::VisitUnaryDeref(const UnaryOperator *E) {
5484  return evaluatePointer(E->getSubExpr(), Result);
5485 }
5486 
5487 bool LValueExprEvaluator::VisitUnaryReal(const UnaryOperator *E) {
5488  if (!Visit(E->getSubExpr()))
5489  return false;
5490  // __real is a no-op on scalar lvalues.
5491  if (E->getSubExpr()->getType()->isAnyComplexType())
5492  HandleLValueComplexElement(Info, E, Result, E->getType(), false);
5493  return true;
5494 }
5495 
5496 bool LValueExprEvaluator::VisitUnaryImag(const UnaryOperator *E) {
5497  assert(E->getSubExpr()->getType()->isAnyComplexType() &&
5498  "lvalue __imag__ on scalar?");
5499  if (!Visit(E->getSubExpr()))
5500  return false;
5501  HandleLValueComplexElement(Info, E, Result, E->getType(), true);
5502  return true;
5503 }
5504 
5505 bool LValueExprEvaluator::VisitUnaryPreIncDec(const UnaryOperator *UO) {
5506  if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
5507  return Error(UO);
5508 
5509  if (!this->Visit(UO->getSubExpr()))
5510  return false;
5511 
5512  return handleIncDec(
5513  this->Info, UO, Result, UO->getSubExpr()->getType(),
5514  UO->isIncrementOp(), nullptr);
5515 }
5516 
5517 bool LValueExprEvaluator::VisitCompoundAssignOperator(
5518  const CompoundAssignOperator *CAO) {
5519  if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
5520  return Error(CAO);
5521 
5522  APValue RHS;
5523 
5524  // The overall lvalue result is the result of evaluating the LHS.
5525  if (!this->Visit(CAO->getLHS())) {
5526  if (Info.noteFailure())
5527  Evaluate(RHS, this->Info, CAO->getRHS());
5528  return false;
5529  }
5530 
5531  if (!Evaluate(RHS, this->Info, CAO->getRHS()))
5532  return false;
5533 
5534  return handleCompoundAssignment(
5535  this->Info, CAO,
5536  Result, CAO->getLHS()->getType(), CAO->getComputationLHSType(),
5537  CAO->getOpForCompoundAssignment(CAO->getOpcode()), RHS);
5538 }
5539 
5540 bool LValueExprEvaluator::VisitBinAssign(const BinaryOperator *E) {
5541  if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
5542  return Error(E);
5543 
5544  APValue NewVal;
5545 
5546  if (!this->Visit(E->getLHS())) {
5547  if (Info.noteFailure())
5548  Evaluate(NewVal, this->Info, E->getRHS());
5549  return false;
5550  }
5551 
5552  if (!Evaluate(NewVal, this->Info, E->getRHS()))
5553  return false;
5554 
5555  return handleAssignment(this->Info, E, Result, E->getLHS()->getType(),
5556  NewVal);
5557 }
5558 
5559 //===----------------------------------------------------------------------===//
5560 // Pointer Evaluation
5561 //===----------------------------------------------------------------------===//
5562 
5563 /// Attempts to compute the number of bytes available at the pointer
5564 /// returned by a function with the alloc_size attribute. Returns true if we
5565 /// were successful. Places an unsigned number into `Result`.
5566 ///
5567 /// This expects the given CallExpr to be a call to a function with an
5568 /// alloc_size attribute.
5570  const CallExpr *Call,
5571  llvm::APInt &Result) {
5572  const AllocSizeAttr *AllocSize = getAllocSizeAttr(Call);
5573 
5574  assert(AllocSize && AllocSize->getElemSizeParam().isValid());
5575  unsigned SizeArgNo = AllocSize->getElemSizeParam().getASTIndex();
5576  unsigned BitsInSizeT = Ctx.getTypeSize(Ctx.getSizeType());
5577  if (Call->getNumArgs() <= SizeArgNo)
5578  return false;
5579 
5580  auto EvaluateAsSizeT = [&](const Expr *E, APSInt &Into) {
5581  if (!E->EvaluateAsInt(Into, Ctx, Expr::SE_AllowSideEffects))
5582  return false;
5583  if (Into.isNegative() || !Into.isIntN(BitsInSizeT))
5584  return false;
5585  Into = Into.zextOrSelf(BitsInSizeT);
5586  return true;
5587  };
5588 
5589  APSInt SizeOfElem;
5590  if (!EvaluateAsSizeT(Call->getArg(SizeArgNo), SizeOfElem))
5591  return false;
5592 
5593  if (!AllocSize->getNumElemsParam().isValid()) {
5594  Result = std::move(SizeOfElem);
5595  return true;
5596  }
5597 
5598  APSInt NumberOfElems;
5599  unsigned NumArgNo = AllocSize->getNumElemsParam().getASTIndex();
5600  if (!EvaluateAsSizeT(Call->getArg(NumArgNo), NumberOfElems))
5601  return false;
5602 
5603  bool Overflow;
5604  llvm::APInt BytesAvailable = SizeOfElem.umul_ov(NumberOfElems, Overflow);
5605  if (Overflow)
5606  return false;
5607 
5608  Result = std::move(BytesAvailable);
5609  return true;
5610 }
5611 
5612 /// Convenience function. LVal's base must be a call to an alloc_size
5613 /// function.
5615  const LValue &LVal,
5616  llvm::APInt &Result) {
5617  assert(isBaseAnAllocSizeCall(LVal.getLValueBase()) &&
5618  "Can't get the size of a non alloc_size function");
5619  const auto *Base = LVal.getLValueBase().get<const Expr *>();
5620  const CallExpr *CE = tryUnwrapAllocSizeCall(Base);
5621  return getBytesReturnedByAllocSizeCall(Ctx, CE, Result);
5622 }
5623 
5624 /// Attempts to evaluate the given LValueBase as the result of a call to
5625 /// a function with the alloc_size attribute. If it was possible to do so, this
5626 /// function will return true, make Result's Base point to said function call,
5627 /// and mark Result's Base as invalid.
5628 static bool evaluateLValueAsAllocSize(EvalInfo &Info, APValue::LValueBase Base,
5629  LValue &Result) {
5630  if (Base.isNull())
5631  return false;
5632 
5633  // Because we do no form of static analysis, we only support const variables.
5634  //
5635  // Additionally, we can't support parameters, nor can we support static
5636  // variables (in the latter case, use-before-assign isn't UB; in the former,
5637  // we have no clue what they'll be assigned to).
5638  const auto *VD =
5639  dyn_cast_or_null<VarDecl>(Base.dyn_cast<const ValueDecl *>());
5640  if (!VD || !VD->isLocalVarDecl() || !VD->getType().isConstQualified())
5641  return false;
5642 
5643  const Expr *Init = VD->getAnyInitializer();
5644  if (!Init)
5645  return false;
5646 
5647  const Expr *E = Init->IgnoreParens();
5648  if (!tryUnwrapAllocSizeCall(E))
5649  return false;
5650 
5651  // Store E instead of E unwrapped so that the type of the LValue's base is
5652  // what the user wanted.
5653  Result.setInvalid(E);
5654 
5655  QualType Pointee = E->getType()->castAs<PointerType>()->getPointeeType();
5656  Result.addUnsizedArray(Info, E, Pointee);
5657  return true;
5658 }
5659 
5660 namespace {
5661 class PointerExprEvaluator
5662  : public ExprEvaluatorBase<PointerExprEvaluator> {
5663  LValue &Result;
5664  bool InvalidBaseOK;
5665 
5666  bool Success(const Expr *E) {
5667  Result.set(E);
5668  return true;
5669  }
5670 
5671  bool evaluateLValue(const Expr *E, LValue &Result) {
5672  return EvaluateLValue(E, Result, Info, InvalidBaseOK);
5673  }
5674 
5675  bool evaluatePointer(const Expr *E, LValue &Result) {
5676  return EvaluatePointer(E, Result, Info, InvalidBaseOK);
5677  }
5678 
5679  bool visitNonBuiltinCallExpr(const CallExpr *E);
5680 public:
5681 
5682  PointerExprEvaluator(EvalInfo &info, LValue &Result, bool InvalidBaseOK)
5683  : ExprEvaluatorBaseTy(info), Result(Result),
5684  InvalidBaseOK(InvalidBaseOK) {}
5685 
5686  bool Success(const APValue &V, const Expr *E) {
5687  Result.setFrom(Info.Ctx, V);
5688  return true;
5689  }
5690  bool ZeroInitialization(const Expr *E) {
5691  auto TargetVal = Info.Ctx.getTargetNullPointerValue(E->getType());
5692  Result.setNull(E->getType(), TargetVal);
5693  return true;
5694  }
5695 
5696  bool VisitBinaryOperator(const BinaryOperator *E);
5697  bool VisitCastExpr(const CastExpr* E);
5698  bool VisitUnaryAddrOf(const UnaryOperator *E);
5699  bool VisitObjCStringLiteral(const ObjCStringLiteral *E)
5700  { return Success(E); }
5701  bool VisitObjCBoxedExpr(const ObjCBoxedExpr *E) {
5702  if (Info.noteFailure())
5703  EvaluateIgnoredValue(Info, E->getSubExpr());
5704  return Error(E);
5705  }
5706  bool VisitAddrLabelExpr(const AddrLabelExpr *E)
5707  { return Success(E); }
5708  bool VisitCallExpr(const CallExpr *E);
5709  bool VisitBuiltinCallExpr(const CallExpr *E, unsigned BuiltinOp);
5710  bool VisitBlockExpr(const BlockExpr *E) {
5711  if (!E->getBlockDecl()->hasCaptures())
5712  return Success(E);
5713  return Error(E);
5714  }
5715  bool VisitCXXThisExpr(const CXXThisExpr *E) {
5716  // Can't look at 'this' when checking a potential constant expression.
5717  if (Info.checkingPotentialConstantExpression())
5718  return false;
5719  if (!Info.CurrentCall->This) {
5720  if (Info.getLangOpts().CPlusPlus11)
5721  Info.FFDiag(E, diag::note_constexpr_this) << E->isImplicit();
5722  else
5723  Info.FFDiag(E);
5724  return false;
5725  }
5726  Result = *Info.CurrentCall->This;
5727  // If we are inside a lambda's call operator, the 'this' expression refers
5728  // to the enclosing '*this' object (either by value or reference) which is
5729  // either copied into the closure object's field that represents the '*this'
5730  // or refers to '*this'.
5731  if (isLambdaCallOperator(Info.CurrentCall->Callee)) {
5732  // Update 'Result' to refer to the data member/field of the closure object
5733  // that represents the '*this' capture.
5734  if (!HandleLValueMember(Info, E, Result,
5735  Info.CurrentCall->LambdaThisCaptureField))
5736  return false;
5737  // If we captured '*this' by reference, replace the field with its referent.
5738  if (Info.CurrentCall->LambdaThisCaptureField->getType()
5739  ->isPointerType()) {
5740  APValue RVal;
5741  if (!handleLValueToRValueConversion(Info, E, E->getType(), Result,
5742  RVal))
5743  return false;
5744 
5745  Result.setFrom(Info.Ctx, RVal);
5746  }
5747  }
5748  return true;
5749  }
5750 
5751  // FIXME: Missing: @protocol, @selector
5752 };
5753 } // end anonymous namespace
5754 
5755 static bool EvaluatePointer(const Expr* E, LValue& Result, EvalInfo &Info,
5756  bool InvalidBaseOK) {
5757  assert(E->isRValue() && E->getType()->hasPointerRepresentation());
5758  return PointerExprEvaluator(Info, Result, InvalidBaseOK).Visit(E);
5759 }
5760 
5761 bool PointerExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
5762  if (E->getOpcode() != BO_Add &&
5763  E->getOpcode() != BO_Sub)
5764  return ExprEvaluatorBaseTy::VisitBinaryOperator(E);
5765 
5766  const Expr *PExp = E->getLHS();
5767  const Expr *IExp = E->getRHS();
5768  if (IExp->getType()->isPointerType())
5769  std::swap(PExp, IExp);
5770 
5771  bool EvalPtrOK = evaluatePointer(PExp, Result);
5772  if (!EvalPtrOK && !Info.noteFailure())
5773  return false;
5774 
5775  llvm::APSInt Offset;
5776  if (!EvaluateInteger(IExp, Offset, Info) || !EvalPtrOK)
5777  return false;
5778 
5779  if (E->getOpcode() == BO_Sub)
5780  negateAsSigned(Offset);
5781 
5782  QualType Pointee = PExp->getType()->castAs<PointerType>()->getPointeeType();
5783  return HandleLValueArrayAdjustment(Info, E, Result, Pointee, Offset);
5784 }
5785 
5786 bool PointerExprEvaluator::VisitUnaryAddrOf(const UnaryOperator *E) {
5787  return evaluateLValue(E->getSubExpr(), Result);
5788 }
5789 
5790 bool PointerExprEvaluator::VisitCastExpr(const CastExpr* E) {
5791  const Expr* SubExpr = E->getSubExpr();
5792 
5793  switch (E->getCastKind()) {
5794  default:
5795  break;
5796 
5797  case CK_BitCast:
5798  case CK_CPointerToObjCPointerCast:
5799  case CK_BlockPointerToObjCPointerCast:
5800  case CK_AnyPointerToBlockPointerCast:
5801  case CK_AddressSpaceConversion:
5802  if (!Visit(SubExpr))
5803  return false;
5804  // Bitcasts to cv void* are static_casts, not reinterpret_casts, so are
5805  // permitted in constant expressions in C++11. Bitcasts from cv void* are
5806  // also static_casts, but we disallow them as a resolution to DR1312.
5807  if (!E->getType()->isVoidPointerType()) {
5808  Result.Designator.setInvalid();
5809  if (SubExpr->getType()->isVoidPointerType())
5810  CCEDiag(E, diag::note_constexpr_invalid_cast)
5811  << 3 << SubExpr->getType();
5812  else
5813  CCEDiag(E, diag::note_constexpr_invalid_cast) << 2;
5814  }
5815  if (E->getCastKind() == CK_AddressSpaceConversion && Result.IsNullPtr)
5816  ZeroInitialization(E);
5817  return true;
5818 
5819  case CK_DerivedToBase:
5820  case CK_UncheckedDerivedToBase:
5821  if (!evaluatePointer(E->getSubExpr(), Result))
5822  return false;
5823  if (!Result.Base && Result.Offset.isZero())
5824  return true;
5825 
5826  // Now figure out the necessary offset to add to the base LV to get from
5827  // the derived class to the base class.
5828  return HandleLValueBasePath(Info, E, E->getSubExpr()->getType()->
5829  castAs<PointerType>()->getPointeeType(),
5830  Result);
5831 
5832  case CK_BaseToDerived:
5833  if (!Visit(E->getSubExpr()))
5834  return false;
5835  if (!Result.Base && Result.Offset.isZero())
5836  return true;
5837  return HandleBaseToDerivedCast(Info, E, Result);
5838 
5839  case CK_NullToPointer:
5840  VisitIgnoredValue(E->getSubExpr());
5841  return ZeroInitialization(E);
5842 
5843  case CK_IntegralToPointer: {
5844  CCEDiag(E, diag::note_constexpr_invalid_cast) << 2;
5845 
5846  APValue Value;
5847  if (!EvaluateIntegerOrLValue(SubExpr, Value, Info))
5848  break;
5849 
5850  if (Value.isInt()) {
5851  unsigned Size = Info.Ctx.getTypeSize(E->getType());
5852  uint64_t N = Value.getInt().extOrTrunc(Size).getZExtValue();
5853  Result.Base = (Expr*)nullptr;
5854  Result.InvalidBase = false;
5855  Result.Offset = CharUnits::fromQuantity(N);
5856  Result.Designator.setInvalid();
5857  Result.IsNullPtr = false;
5858  return true;
5859  } else {
5860  // Cast is of an lvalue, no need to change value.
5861  Result.setFrom(Info.Ctx, Value);
5862  return true;
5863  }
5864  }
5865 
5866  case CK_ArrayToPointerDecay: {
5867  if (SubExpr->isGLValue()) {
5868  if (!evaluateLValue(SubExpr, Result))
5869  return false;
5870  } else {
5871  APValue &Value = createTemporary(SubExpr, false, Result,
5872  *Info.CurrentCall);
5873  if (!EvaluateInPlace(Value, Info, Result, SubExpr))
5874  return false;
5875  }
5876  // The result is a pointer to the first element of the array.
5877  auto *AT = Info.Ctx.getAsArrayType(SubExpr->getType());
5878  if (auto *CAT = dyn_cast<ConstantArrayType>(AT))
5879  Result.addArray(Info, E, CAT);
5880  else
5881  Result.addUnsizedArray(Info, E, AT->getElementType());
5882  return true;
5883  }
5884 
5885  case CK_FunctionToPointerDecay:
5886  return evaluateLValue(SubExpr, Result);
5887 
5888  case CK_LValueToRValue: {
5889  LValue LVal;
5890  if (!evaluateLValue(E->getSubExpr(), LVal))
5891  return false;
5892 
5893  APValue RVal;
5894  // Note, we use the subexpression's type in order to retain cv-qualifiers.
5895  if (!handleLValueToRValueConversion(Info, E, E->getSubExpr()->getType(),
5896  LVal, RVal))
5897  return InvalidBaseOK &&
5898  evaluateLValueAsAllocSize(Info, LVal.Base, Result);
5899  return Success(RVal, E);
5900  }
5901  }
5902 
5903  return ExprEvaluatorBaseTy::VisitCastExpr(E);
5904 }
5905 
5906 static CharUnits GetAlignOfType(EvalInfo &Info, QualType T) {
5907  // C++ [expr.alignof]p3:
5908  // When alignof is applied to a reference type, the result is the
5909  // alignment of the referenced type.
5910  if (const ReferenceType *Ref = T->getAs<ReferenceType>())
5911  T = Ref->getPointeeType();
5912 
5913  // __alignof is defined to return the preferred alignment.
5914  if (T.getQualifiers().hasUnaligned())
5915  return CharUnits::One();
5916  return Info.Ctx.toCharUnitsFromBits(
5917  Info.Ctx.getPreferredTypeAlign(T.getTypePtr()));
5918 }
5919 
5920 static CharUnits GetAlignOfExpr(EvalInfo &Info, const Expr *E) {
5921  E = E->IgnoreParens();
5922 
5923  // The kinds of expressions that we have special-case logic here for
5924  // should be kept up to date with the special checks for those
5925  // expressions in Sema.
5926 
5927  // alignof decl is always accepted, even if it doesn't make sense: we default
5928  // to 1 in those cases.
5929  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
5930  return Info.Ctx.getDeclAlign(DRE->getDecl(),
5931  /*RefAsPointee*/true);
5932 
5933  if (const MemberExpr *ME = dyn_cast<MemberExpr>(E))
5934  return Info.Ctx.getDeclAlign(ME->getMemberDecl(),
5935  /*RefAsPointee*/true);
5936 
5937  return GetAlignOfType(Info, E->getType());
5938 }
5939 
5940 // To be clear: this happily visits unsupported builtins. Better name welcomed.
5941 bool PointerExprEvaluator::visitNonBuiltinCallExpr(const CallExpr *E) {
5942  if (ExprEvaluatorBaseTy::VisitCallExpr(E))
5943  return true;
5944 
5945  if (!(InvalidBaseOK && getAllocSizeAttr(E)))
5946  return false;
5947 
5948  Result.setInvalid(E);
5949  QualType PointeeTy = E->getType()->castAs<PointerType>()->getPointeeType();
5950  Result.addUnsizedArray(Info, E, PointeeTy);
5951  return true;
5952 }
5953 
5954 bool PointerExprEvaluator::VisitCallExpr(const CallExpr *E) {
5955  if (IsStringLiteralCall(E))
5956  return Success(E);
5957 
5958  if (unsigned BuiltinOp = E->getBuiltinCallee())
5959  return VisitBuiltinCallExpr(E, BuiltinOp);
5960 
5961  return visitNonBuiltinCallExpr(E);
5962 }
5963 
5964 bool PointerExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
5965  unsigned BuiltinOp) {
5966  switch (BuiltinOp) {
5967  case Builtin::BI__builtin_addressof:
5968  return evaluateLValue(E->getArg(0), Result);
5969  case Builtin::BI__builtin_assume_aligned: {
5970  // We need to be very careful here because: if the pointer does not have the
5971  // asserted alignment, then the behavior is undefined, and undefined
5972  // behavior is non-constant.
5973  if (!evaluatePointer(E->getArg(0), Result))
5974  return false;
5975 
5976  LValue OffsetResult(Result);
5977  APSInt Alignment;
5978  if (!EvaluateInteger(E->getArg(1), Alignment, Info))
5979  return false;
5980  CharUnits Align = CharUnits::fromQuantity(Alignment.getZExtValue());
5981 
5982  if (E->getNumArgs() > 2) {