clang  9.0.0svn
ExprConstant.cpp
Go to the documentation of this file.
1 //===--- ExprConstant.cpp - Expression Constant Evaluator -----------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the Expr constant evaluator.
10 //
11 // Constant expression evaluation produces four main results:
12 //
13 // * A success/failure flag indicating whether constant folding was successful.
14 // This is the 'bool' return value used by most of the code in this file. A
15 // 'false' return value indicates that constant folding has failed, and any
16 // appropriate diagnostic has already been produced.
17 //
18 // * An evaluated result, valid only if constant folding has not failed.
19 //
20 // * A flag indicating if evaluation encountered (unevaluated) side-effects.
21 // These arise in cases such as (sideEffect(), 0) and (sideEffect() || 1),
22 // where it is possible to determine the evaluated result regardless.
23 //
24 // * A set of notes indicating why the evaluation was not a constant expression
25 // (under the C++11 / C++1y rules only, at the moment), or, if folding failed
26 // too, why the expression could not be folded.
27 //
28 // If we are checking for a potential constant expression, failure to constant
29 // fold a potential constant sub-expression will be indicated by a 'false'
30 // return value (the expression could not be folded) and no diagnostic (the
31 // expression is not necessarily non-constant).
32 //
33 //===----------------------------------------------------------------------===//
34 
35 #include "clang/AST/APValue.h"
36 #include "clang/AST/ASTContext.h"
38 #include "clang/AST/ASTLambda.h"
39 #include "clang/AST/CharUnits.h"
40 #include "clang/AST/Expr.h"
41 #include "clang/AST/OSLog.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/FixedPoint.h"
47 #include "clang/Basic/TargetInfo.h"
48 #include "llvm/Support/SaveAndRestore.h"
49 #include "llvm/Support/raw_ostream.h"
50 #include <cstring>
51 #include <functional>
52 
53 #define DEBUG_TYPE "exprconstant"
54 
55 using namespace clang;
56 using llvm::APSInt;
57 using llvm::APFloat;
58 
59 static bool IsGlobalLValue(APValue::LValueBase B);
60 
61 namespace {
62  struct LValue;
63  struct CallStackFrame;
64  struct EvalInfo;
65 
66  static QualType getType(APValue::LValueBase B) {
67  if (!B) return QualType();
68  if (const ValueDecl *D = B.dyn_cast<const ValueDecl*>()) {
69  // FIXME: It's unclear where we're supposed to take the type from, and
70  // this actually matters for arrays of unknown bound. Eg:
71  //
72  // extern int arr[]; void f() { extern int arr[3]; };
73  // constexpr int *p = &arr[1]; // valid?
74  //
75  // For now, we take the array bound from the most recent declaration.
76  for (auto *Redecl = cast<ValueDecl>(D->getMostRecentDecl()); Redecl;
77  Redecl = cast_or_null<ValueDecl>(Redecl->getPreviousDecl())) {
78  QualType T = Redecl->getType();
79  if (!T->isIncompleteArrayType())
80  return T;
81  }
82  return D->getType();
83  }
84 
85  const Expr *Base = B.get<const Expr*>();
86 
87  // For a materialized temporary, the type of the temporary we materialized
88  // may not be the type of the expression.
89  if (const MaterializeTemporaryExpr *MTE =
90  dyn_cast<MaterializeTemporaryExpr>(Base)) {
93  const Expr *Temp = MTE->GetTemporaryExpr();
94  const Expr *Inner = Temp->skipRValueSubobjectAdjustments(CommaLHSs,
95  Adjustments);
96  // Keep any cv-qualifiers from the reference if we generated a temporary
97  // for it directly. Otherwise use the type after adjustment.
98  if (!Adjustments.empty())
99  return Inner->getType();
100  }
101 
102  return Base->getType();
103  }
104 
105  /// Get an LValue path entry, which is known to not be an array index, as a
106  /// field or base class.
107  static
110  Value.setFromOpaqueValue(E.BaseOrMember);
111  return Value;
112  }
113 
114  /// Get an LValue path entry, which is known to not be an array index, as a
115  /// field declaration.
116  static const FieldDecl *getAsField(APValue::LValuePathEntry E) {
117  return dyn_cast<FieldDecl>(getAsBaseOrMember(E).getPointer());
118  }
119  /// Get an LValue path entry, which is known to not be an array index, as a
120  /// base class declaration.
121  static const CXXRecordDecl *getAsBaseClass(APValue::LValuePathEntry E) {
122  return dyn_cast<CXXRecordDecl>(getAsBaseOrMember(E).getPointer());
123  }
124  /// Determine whether this LValue path entry for a base class names a virtual
125  /// base class.
126  static bool isVirtualBaseClass(APValue::LValuePathEntry E) {
127  return getAsBaseOrMember(E).getInt();
128  }
129 
130  /// Given a CallExpr, try to get the alloc_size attribute. May return null.
131  static const AllocSizeAttr *getAllocSizeAttr(const CallExpr *CE) {
132  const FunctionDecl *Callee = CE->getDirectCallee();
133  return Callee ? Callee->getAttr<AllocSizeAttr>() : nullptr;
134  }
135 
136  /// Attempts to unwrap a CallExpr (with an alloc_size attribute) from an Expr.
137  /// This will look through a single cast.
138  ///
139  /// Returns null if we couldn't unwrap a function with alloc_size.
140  static const CallExpr *tryUnwrapAllocSizeCall(const Expr *E) {
141  if (!E->getType()->isPointerType())
142  return nullptr;
143 
144  E = E->IgnoreParens();
145  // If we're doing a variable assignment from e.g. malloc(N), there will
146  // probably be a cast of some kind. In exotic cases, we might also see a
147  // top-level ExprWithCleanups. Ignore them either way.
148  if (const auto *FE = dyn_cast<FullExpr>(E))
149  E = FE->getSubExpr()->IgnoreParens();
150 
151  if (const auto *Cast = dyn_cast<CastExpr>(E))
152  E = Cast->getSubExpr()->IgnoreParens();
153 
154  if (const auto *CE = dyn_cast<CallExpr>(E))
155  return getAllocSizeAttr(CE) ? CE : nullptr;
156  return nullptr;
157  }
158 
159  /// Determines whether or not the given Base contains a call to a function
160  /// with the alloc_size attribute.
161  static bool isBaseAnAllocSizeCall(APValue::LValueBase Base) {
162  const auto *E = Base.dyn_cast<const Expr *>();
163  return E && E->getType()->isPointerType() && tryUnwrapAllocSizeCall(E);
164  }
165 
166  /// The bound to claim that an array of unknown bound has.
167  /// The value in MostDerivedArraySize is undefined in this case. So, set it
168  /// to an arbitrary value that's likely to loudly break things if it's used.
169  static const uint64_t AssumedSizeForUnsizedArray =
171 
172  /// Determines if an LValue with the given LValueBase will have an unsized
173  /// array in its designator.
174  /// Find the path length and type of the most-derived subobject in the given
175  /// path, and find the size of the containing array, if any.
176  static unsigned
177  findMostDerivedSubobject(ASTContext &Ctx, APValue::LValueBase Base,
179  uint64_t &ArraySize, QualType &Type, bool &IsArray,
180  bool &FirstEntryIsUnsizedArray) {
181  // This only accepts LValueBases from APValues, and APValues don't support
182  // arrays that lack size info.
183  assert(!isBaseAnAllocSizeCall(Base) &&
184  "Unsized arrays shouldn't appear here");
185  unsigned MostDerivedLength = 0;
186  Type = getType(Base);
187 
188  for (unsigned I = 0, N = Path.size(); I != N; ++I) {
189  if (Type->isArrayType()) {
190  const ArrayType *AT = Ctx.getAsArrayType(Type);
191  Type = AT->getElementType();
192  MostDerivedLength = I + 1;
193  IsArray = true;
194 
195  if (auto *CAT = dyn_cast<ConstantArrayType>(AT)) {
196  ArraySize = CAT->getSize().getZExtValue();
197  } else {
198  assert(I == 0 && "unexpected unsized array designator");
199  FirstEntryIsUnsizedArray = true;
200  ArraySize = AssumedSizeForUnsizedArray;
201  }
202  } else if (Type->isAnyComplexType()) {
203  const ComplexType *CT = Type->castAs<ComplexType>();
204  Type = CT->getElementType();
205  ArraySize = 2;
206  MostDerivedLength = I + 1;
207  IsArray = true;
208  } else if (const FieldDecl *FD = getAsField(Path[I])) {
209  Type = FD->getType();
210  ArraySize = 0;
211  MostDerivedLength = I + 1;
212  IsArray = false;
213  } else {
214  // Path[I] describes a base class.
215  ArraySize = 0;
216  IsArray = false;
217  }
218  }
219  return MostDerivedLength;
220  }
221 
222  // The order of this enum is important for diagnostics.
224  CSK_Base, CSK_Derived, CSK_Field, CSK_ArrayToPointer, CSK_ArrayIndex,
225  CSK_This, CSK_Real, CSK_Imag
226  };
227 
228  /// A path from a glvalue to a subobject of that glvalue.
229  struct SubobjectDesignator {
230  /// True if the subobject was named in a manner not supported by C++11. Such
231  /// lvalues can still be folded, but they are not core constant expressions
232  /// and we cannot perform lvalue-to-rvalue conversions on them.
233  unsigned Invalid : 1;
234 
235  /// Is this a pointer one past the end of an object?
236  unsigned IsOnePastTheEnd : 1;
237 
238  /// Indicator of whether the first entry is an unsized array.
239  unsigned FirstEntryIsAnUnsizedArray : 1;
240 
241  /// Indicator of whether the most-derived object is an array element.
242  unsigned MostDerivedIsArrayElement : 1;
243 
244  /// The length of the path to the most-derived object of which this is a
245  /// subobject.
246  unsigned MostDerivedPathLength : 28;
247 
248  /// The size of the array of which the most-derived object is an element.
249  /// This will always be 0 if the most-derived object is not an array
250  /// element. 0 is not an indicator of whether or not the most-derived object
251  /// is an array, however, because 0-length arrays are allowed.
252  ///
253  /// If the current array is an unsized array, the value of this is
254  /// undefined.
255  uint64_t MostDerivedArraySize;
256 
257  /// The type of the most derived object referred to by this address.
258  QualType MostDerivedType;
259 
260  typedef APValue::LValuePathEntry PathEntry;
261 
262  /// The entries on the path from the glvalue to the designated subobject.
264 
265  SubobjectDesignator() : Invalid(true) {}
266 
267  explicit SubobjectDesignator(QualType T)
268  : Invalid(false), IsOnePastTheEnd(false),
269  FirstEntryIsAnUnsizedArray(false), MostDerivedIsArrayElement(false),
270  MostDerivedPathLength(0), MostDerivedArraySize(0),
271  MostDerivedType(T) {}
272 
273  SubobjectDesignator(ASTContext &Ctx, const APValue &V)
274  : Invalid(!V.isLValue() || !V.hasLValuePath()), IsOnePastTheEnd(false),
275  FirstEntryIsAnUnsizedArray(false), MostDerivedIsArrayElement(false),
276  MostDerivedPathLength(0), MostDerivedArraySize(0) {
277  assert(V.isLValue() && "Non-LValue used to make an LValue designator?");
278  if (!Invalid) {
279  IsOnePastTheEnd = V.isLValueOnePastTheEnd();
280  ArrayRef<PathEntry> VEntries = V.getLValuePath();
281  Entries.insert(Entries.end(), VEntries.begin(), VEntries.end());
282  if (V.getLValueBase()) {
283  bool IsArray = false;
284  bool FirstIsUnsizedArray = false;
285  MostDerivedPathLength = findMostDerivedSubobject(
286  Ctx, V.getLValueBase(), V.getLValuePath(), MostDerivedArraySize,
287  MostDerivedType, IsArray, FirstIsUnsizedArray);
288  MostDerivedIsArrayElement = IsArray;
289  FirstEntryIsAnUnsizedArray = FirstIsUnsizedArray;
290  }
291  }
292  }
293 
294  void setInvalid() {
295  Invalid = true;
296  Entries.clear();
297  }
298 
299  /// Determine whether the most derived subobject is an array without a
300  /// known bound.
301  bool isMostDerivedAnUnsizedArray() const {
302  assert(!Invalid && "Calling this makes no sense on invalid designators");
303  return Entries.size() == 1 && FirstEntryIsAnUnsizedArray;
304  }
305 
306  /// Determine what the most derived array's size is. Results in an assertion
307  /// failure if the most derived array lacks a size.
308  uint64_t getMostDerivedArraySize() const {
309  assert(!isMostDerivedAnUnsizedArray() && "Unsized array has no size");
310  return MostDerivedArraySize;
311  }
312 
313  /// Determine whether this is a one-past-the-end pointer.
314  bool isOnePastTheEnd() const {
315  assert(!Invalid);
316  if (IsOnePastTheEnd)
317  return true;
318  if (!isMostDerivedAnUnsizedArray() && MostDerivedIsArrayElement &&
319  Entries[MostDerivedPathLength - 1].ArrayIndex == MostDerivedArraySize)
320  return true;
321  return false;
322  }
323 
324  /// Get the range of valid index adjustments in the form
325  /// {maximum value that can be subtracted from this pointer,
326  /// maximum value that can be added to this pointer}
327  std::pair<uint64_t, uint64_t> validIndexAdjustments() {
328  if (Invalid || isMostDerivedAnUnsizedArray())
329  return {0, 0};
330 
331  // [expr.add]p4: For the purposes of these operators, a pointer to a
332  // nonarray object behaves the same as a pointer to the first element of
333  // an array of length one with the type of the object as its element type.
334  bool IsArray = MostDerivedPathLength == Entries.size() &&
335  MostDerivedIsArrayElement;
336  uint64_t ArrayIndex =
337  IsArray ? Entries.back().ArrayIndex : (uint64_t)IsOnePastTheEnd;
338  uint64_t ArraySize =
339  IsArray ? getMostDerivedArraySize() : (uint64_t)1;
340  return {ArrayIndex, ArraySize - ArrayIndex};
341  }
342 
343  /// Check that this refers to a valid subobject.
344  bool isValidSubobject() const {
345  if (Invalid)
346  return false;
347  return !isOnePastTheEnd();
348  }
349  /// Check that this refers to a valid subobject, and if not, produce a
350  /// relevant diagnostic and set the designator as invalid.
351  bool checkSubobject(EvalInfo &Info, const Expr *E, CheckSubobjectKind CSK);
352 
353  /// Get the type of the designated object.
354  QualType getType(ASTContext &Ctx) const {
355  assert(!Invalid && "invalid designator has no subobject type");
356  return MostDerivedPathLength == Entries.size()
357  ? MostDerivedType
358  : Ctx.getRecordType(getAsBaseClass(Entries.back()));
359  }
360 
361  /// Update this designator to refer to the first element within this array.
362  void addArrayUnchecked(const ConstantArrayType *CAT) {
363  PathEntry Entry;
364  Entry.ArrayIndex = 0;
365  Entries.push_back(Entry);
366 
367  // This is a most-derived object.
368  MostDerivedType = CAT->getElementType();
369  MostDerivedIsArrayElement = true;
370  MostDerivedArraySize = CAT->getSize().getZExtValue();
371  MostDerivedPathLength = Entries.size();
372  }
373  /// Update this designator to refer to the first element within the array of
374  /// elements of type T. This is an array of unknown size.
375  void addUnsizedArrayUnchecked(QualType ElemTy) {
376  PathEntry Entry;
377  Entry.ArrayIndex = 0;
378  Entries.push_back(Entry);
379 
380  MostDerivedType = ElemTy;
381  MostDerivedIsArrayElement = true;
382  // The value in MostDerivedArraySize is undefined in this case. So, set it
383  // to an arbitrary value that's likely to loudly break things if it's
384  // used.
385  MostDerivedArraySize = AssumedSizeForUnsizedArray;
386  MostDerivedPathLength = Entries.size();
387  }
388  /// Update this designator to refer to the given base or member of this
389  /// object.
390  void addDeclUnchecked(const Decl *D, bool Virtual = false) {
391  PathEntry Entry;
392  APValue::BaseOrMemberType Value(D, Virtual);
393  Entry.BaseOrMember = Value.getOpaqueValue();
394  Entries.push_back(Entry);
395 
396  // If this isn't a base class, it's a new most-derived object.
397  if (const FieldDecl *FD = dyn_cast<FieldDecl>(D)) {
398  MostDerivedType = FD->getType();
399  MostDerivedIsArrayElement = false;
400  MostDerivedArraySize = 0;
401  MostDerivedPathLength = Entries.size();
402  }
403  }
404  /// Update this designator to refer to the given complex component.
405  void addComplexUnchecked(QualType EltTy, bool Imag) {
406  PathEntry Entry;
407  Entry.ArrayIndex = Imag;
408  Entries.push_back(Entry);
409 
410  // This is technically a most-derived object, though in practice this
411  // is unlikely to matter.
412  MostDerivedType = EltTy;
413  MostDerivedIsArrayElement = true;
414  MostDerivedArraySize = 2;
415  MostDerivedPathLength = Entries.size();
416  }
417  void diagnoseUnsizedArrayPointerArithmetic(EvalInfo &Info, const Expr *E);
418  void diagnosePointerArithmetic(EvalInfo &Info, const Expr *E,
419  const APSInt &N);
420  /// Add N to the address of this subobject.
421  void adjustIndex(EvalInfo &Info, const Expr *E, APSInt N) {
422  if (Invalid || !N) return;
423  uint64_t TruncatedN = N.extOrTrunc(64).getZExtValue();
424  if (isMostDerivedAnUnsizedArray()) {
425  diagnoseUnsizedArrayPointerArithmetic(Info, E);
426  // Can't verify -- trust that the user is doing the right thing (or if
427  // not, trust that the caller will catch the bad behavior).
428  // FIXME: Should we reject if this overflows, at least?
429  Entries.back().ArrayIndex += TruncatedN;
430  return;
431  }
432 
433  // [expr.add]p4: For the purposes of these operators, a pointer to a
434  // nonarray object behaves the same as a pointer to the first element of
435  // an array of length one with the type of the object as its element type.
436  bool IsArray = MostDerivedPathLength == Entries.size() &&
437  MostDerivedIsArrayElement;
438  uint64_t ArrayIndex =
439  IsArray ? Entries.back().ArrayIndex : (uint64_t)IsOnePastTheEnd;
440  uint64_t ArraySize =
441  IsArray ? getMostDerivedArraySize() : (uint64_t)1;
442 
443  if (N < -(int64_t)ArrayIndex || N > ArraySize - ArrayIndex) {
444  // Calculate the actual index in a wide enough type, so we can include
445  // it in the note.
446  N = N.extend(std::max<unsigned>(N.getBitWidth() + 1, 65));
447  (llvm::APInt&)N += ArrayIndex;
448  assert(N.ugt(ArraySize) && "bounds check failed for in-bounds index");
449  diagnosePointerArithmetic(Info, E, N);
450  setInvalid();
451  return;
452  }
453 
454  ArrayIndex += TruncatedN;
455  assert(ArrayIndex <= ArraySize &&
456  "bounds check succeeded for out-of-bounds index");
457 
458  if (IsArray)
459  Entries.back().ArrayIndex = ArrayIndex;
460  else
461  IsOnePastTheEnd = (ArrayIndex != 0);
462  }
463  };
464 
465  /// A stack frame in the constexpr call stack.
466  struct CallStackFrame {
467  EvalInfo &Info;
468 
469  /// Parent - The caller of this stack frame.
470  CallStackFrame *Caller;
471 
472  /// Callee - The function which was called.
473  const FunctionDecl *Callee;
474 
475  /// This - The binding for the this pointer in this call, if any.
476  const LValue *This;
477 
478  /// Arguments - Parameter bindings for this function call, indexed by
479  /// parameters' function scope indices.
480  APValue *Arguments;
481 
482  // Note that we intentionally use std::map here so that references to
483  // values are stable.
484  typedef std::pair<const void *, unsigned> MapKeyTy;
485  typedef std::map<MapKeyTy, APValue> MapTy;
486  /// Temporaries - Temporary lvalues materialized within this stack frame.
487  MapTy Temporaries;
488 
489  /// CallLoc - The location of the call expression for this call.
490  SourceLocation CallLoc;
491 
492  /// Index - The call index of this call.
493  unsigned Index;
494 
495  /// The stack of integers for tracking version numbers for temporaries.
496  SmallVector<unsigned, 2> TempVersionStack = {1};
497  unsigned CurTempVersion = TempVersionStack.back();
498 
499  unsigned getTempVersion() const { return TempVersionStack.back(); }
500 
501  void pushTempVersion() {
502  TempVersionStack.push_back(++CurTempVersion);
503  }
504 
505  void popTempVersion() {
506  TempVersionStack.pop_back();
507  }
508 
509  // FIXME: Adding this to every 'CallStackFrame' may have a nontrivial impact
510  // on the overall stack usage of deeply-recursing constexpr evaluations.
511  // (We should cache this map rather than recomputing it repeatedly.)
512  // But let's try this and see how it goes; we can look into caching the map
513  // as a later change.
514 
515  /// LambdaCaptureFields - Mapping from captured variables/this to
516  /// corresponding data members in the closure class.
517  llvm::DenseMap<const VarDecl *, FieldDecl *> LambdaCaptureFields;
518  FieldDecl *LambdaThisCaptureField;
519 
520  CallStackFrame(EvalInfo &Info, SourceLocation CallLoc,
521  const FunctionDecl *Callee, const LValue *This,
522  APValue *Arguments);
523  ~CallStackFrame();
524 
525  // Return the temporary for Key whose version number is Version.
526  APValue *getTemporary(const void *Key, unsigned Version) {
527  MapKeyTy KV(Key, Version);
528  auto LB = Temporaries.lower_bound(KV);
529  if (LB != Temporaries.end() && LB->first == KV)
530  return &LB->second;
531  // Pair (Key,Version) wasn't found in the map. Check that no elements
532  // in the map have 'Key' as their key.
533  assert((LB == Temporaries.end() || LB->first.first != Key) &&
534  (LB == Temporaries.begin() || std::prev(LB)->first.first != Key) &&
535  "Element with key 'Key' found in map");
536  return nullptr;
537  }
538 
539  // Return the current temporary for Key in the map.
540  APValue *getCurrentTemporary(const void *Key) {
541  auto UB = Temporaries.upper_bound(MapKeyTy(Key, UINT_MAX));
542  if (UB != Temporaries.begin() && std::prev(UB)->first.first == Key)
543  return &std::prev(UB)->second;
544  return nullptr;
545  }
546 
547  // Return the version number of the current temporary for Key.
548  unsigned getCurrentTemporaryVersion(const void *Key) const {
549  auto UB = Temporaries.upper_bound(MapKeyTy(Key, UINT_MAX));
550  if (UB != Temporaries.begin() && std::prev(UB)->first.first == Key)
551  return std::prev(UB)->first.second;
552  return 0;
553  }
554 
555  APValue &createTemporary(const void *Key, bool IsLifetimeExtended);
556  };
557 
558  /// Temporarily override 'this'.
559  class ThisOverrideRAII {
560  public:
561  ThisOverrideRAII(CallStackFrame &Frame, const LValue *NewThis, bool Enable)
562  : Frame(Frame), OldThis(Frame.This) {
563  if (Enable)
564  Frame.This = NewThis;
565  }
566  ~ThisOverrideRAII() {
567  Frame.This = OldThis;
568  }
569  private:
570  CallStackFrame &Frame;
571  const LValue *OldThis;
572  };
573 
574  /// A partial diagnostic which we might know in advance that we are not going
575  /// to emit.
576  class OptionalDiagnostic {
578 
579  public:
580  explicit OptionalDiagnostic(PartialDiagnostic *Diag = nullptr)
581  : Diag(Diag) {}
582 
583  template<typename T>
584  OptionalDiagnostic &operator<<(const T &v) {
585  if (Diag)
586  *Diag << v;
587  return *this;
588  }
589 
590  OptionalDiagnostic &operator<<(const APSInt &I) {
591  if (Diag) {
592  SmallVector<char, 32> Buffer;
593  I.toString(Buffer);
594  *Diag << StringRef(Buffer.data(), Buffer.size());
595  }
596  return *this;
597  }
598 
599  OptionalDiagnostic &operator<<(const APFloat &F) {
600  if (Diag) {
601  // FIXME: Force the precision of the source value down so we don't
602  // print digits which are usually useless (we don't really care here if
603  // we truncate a digit by accident in edge cases). Ideally,
604  // APFloat::toString would automatically print the shortest
605  // representation which rounds to the correct value, but it's a bit
606  // tricky to implement.
607  unsigned precision =
608  llvm::APFloat::semanticsPrecision(F.getSemantics());
609  precision = (precision * 59 + 195) / 196;
610  SmallVector<char, 32> Buffer;
611  F.toString(Buffer, precision);
612  *Diag << StringRef(Buffer.data(), Buffer.size());
613  }
614  return *this;
615  }
616 
617  OptionalDiagnostic &operator<<(const APFixedPoint &FX) {
618  if (Diag) {
619  SmallVector<char, 32> Buffer;
620  FX.toString(Buffer);
621  *Diag << StringRef(Buffer.data(), Buffer.size());
622  }
623  return *this;
624  }
625  };
626 
627  /// A cleanup, and a flag indicating whether it is lifetime-extended.
628  class Cleanup {
629  llvm::PointerIntPair<APValue*, 1, bool> Value;
630 
631  public:
632  Cleanup(APValue *Val, bool IsLifetimeExtended)
633  : Value(Val, IsLifetimeExtended) {}
634 
635  bool isLifetimeExtended() const { return Value.getInt(); }
636  void endLifetime() {
637  *Value.getPointer() = APValue();
638  }
639  };
640 
641  /// EvalInfo - This is a private struct used by the evaluator to capture
642  /// information about a subexpression as it is folded. It retains information
643  /// about the AST context, but also maintains information about the folded
644  /// expression.
645  ///
646  /// If an expression could be evaluated, it is still possible it is not a C
647  /// "integer constant expression" or constant expression. If not, this struct
648  /// captures information about how and why not.
649  ///
650  /// One bit of information passed *into* the request for constant folding
651  /// indicates whether the subexpression is "evaluated" or not according to C
652  /// rules. For example, the RHS of (0 && foo()) is not evaluated. We can
653  /// evaluate the expression regardless of what the RHS is, but C only allows
654  /// certain things in certain situations.
655  struct EvalInfo {
656  ASTContext &Ctx;
657 
658  /// EvalStatus - Contains information about the evaluation.
659  Expr::EvalStatus &EvalStatus;
660 
661  /// CurrentCall - The top of the constexpr call stack.
662  CallStackFrame *CurrentCall;
663 
664  /// CallStackDepth - The number of calls in the call stack right now.
665  unsigned CallStackDepth;
666 
667  /// NextCallIndex - The next call index to assign.
668  unsigned NextCallIndex;
669 
670  /// StepsLeft - The remaining number of evaluation steps we're permitted
671  /// to perform. This is essentially a limit for the number of statements
672  /// we will evaluate.
673  unsigned StepsLeft;
674 
675  /// BottomFrame - The frame in which evaluation started. This must be
676  /// initialized after CurrentCall and CallStackDepth.
677  CallStackFrame BottomFrame;
678 
679  /// A stack of values whose lifetimes end at the end of some surrounding
680  /// evaluation frame.
681  llvm::SmallVector<Cleanup, 16> CleanupStack;
682 
683  /// EvaluatingDecl - This is the declaration whose initializer is being
684  /// evaluated, if any.
685  APValue::LValueBase EvaluatingDecl;
686 
687  /// EvaluatingDeclValue - This is the value being constructed for the
688  /// declaration whose initializer is being evaluated, if any.
689  APValue *EvaluatingDeclValue;
690 
691  /// EvaluatingObject - Pair of the AST node that an lvalue represents and
692  /// the call index that that lvalue was allocated in.
693  typedef std::pair<APValue::LValueBase, std::pair<unsigned, unsigned>>
694  EvaluatingObject;
695 
696  /// EvaluatingConstructors - Set of objects that are currently being
697  /// constructed.
698  llvm::DenseSet<EvaluatingObject> EvaluatingConstructors;
699 
700  struct EvaluatingConstructorRAII {
701  EvalInfo &EI;
702  EvaluatingObject Object;
703  bool DidInsert;
704  EvaluatingConstructorRAII(EvalInfo &EI, EvaluatingObject Object)
705  : EI(EI), Object(Object) {
706  DidInsert = EI.EvaluatingConstructors.insert(Object).second;
707  }
708  ~EvaluatingConstructorRAII() {
709  if (DidInsert) EI.EvaluatingConstructors.erase(Object);
710  }
711  };
712 
713  bool isEvaluatingConstructor(APValue::LValueBase Decl, unsigned CallIndex,
714  unsigned Version) {
715  return EvaluatingConstructors.count(
716  EvaluatingObject(Decl, {CallIndex, Version}));
717  }
718 
719  /// The current array initialization index, if we're performing array
720  /// initialization.
721  uint64_t ArrayInitIndex = -1;
722 
723  /// HasActiveDiagnostic - Was the previous diagnostic stored? If so, further
724  /// notes attached to it will also be stored, otherwise they will not be.
725  bool HasActiveDiagnostic;
726 
727  /// Have we emitted a diagnostic explaining why we couldn't constant
728  /// fold (not just why it's not strictly a constant expression)?
729  bool HasFoldFailureDiagnostic;
730 
731  /// Whether or not we're currently speculatively evaluating.
732  bool IsSpeculativelyEvaluating;
733 
734  /// Whether or not we're in a context where the front end requires a
735  /// constant value.
736  bool InConstantContext;
737 
738  enum EvaluationMode {
739  /// Evaluate as a constant expression. Stop if we find that the expression
740  /// is not a constant expression.
741  EM_ConstantExpression,
742 
743  /// Evaluate as a potential constant expression. Keep going if we hit a
744  /// construct that we can't evaluate yet (because we don't yet know the
745  /// value of something) but stop if we hit something that could never be
746  /// a constant expression.
747  EM_PotentialConstantExpression,
748 
749  /// Fold the expression to a constant. Stop if we hit a side-effect that
750  /// we can't model.
751  EM_ConstantFold,
752 
753  /// Evaluate the expression looking for integer overflow and similar
754  /// issues. Don't worry about side-effects, and try to visit all
755  /// subexpressions.
756  EM_EvaluateForOverflow,
757 
758  /// Evaluate in any way we know how. Don't worry about side-effects that
759  /// can't be modeled.
760  EM_IgnoreSideEffects,
761 
762  /// Evaluate as a constant expression. Stop if we find that the expression
763  /// is not a constant expression. Some expressions can be retried in the
764  /// optimizer if we don't constant fold them here, but in an unevaluated
765  /// context we try to fold them immediately since the optimizer never
766  /// gets a chance to look at it.
767  EM_ConstantExpressionUnevaluated,
768 
769  /// Evaluate as a potential constant expression. Keep going if we hit a
770  /// construct that we can't evaluate yet (because we don't yet know the
771  /// value of something) but stop if we hit something that could never be
772  /// a constant expression. Some expressions can be retried in the
773  /// optimizer if we don't constant fold them here, but in an unevaluated
774  /// context we try to fold them immediately since the optimizer never
775  /// gets a chance to look at it.
776  EM_PotentialConstantExpressionUnevaluated,
777  } EvalMode;
778 
779  /// Are we checking whether the expression is a potential constant
780  /// expression?
781  bool checkingPotentialConstantExpression() const {
782  return EvalMode == EM_PotentialConstantExpression ||
783  EvalMode == EM_PotentialConstantExpressionUnevaluated;
784  }
785 
786  /// Are we checking an expression for overflow?
787  // FIXME: We should check for any kind of undefined or suspicious behavior
788  // in such constructs, not just overflow.
789  bool checkingForOverflow() { return EvalMode == EM_EvaluateForOverflow; }
790 
791  EvalInfo(const ASTContext &C, Expr::EvalStatus &S, EvaluationMode Mode)
792  : Ctx(const_cast<ASTContext &>(C)), EvalStatus(S), CurrentCall(nullptr),
793  CallStackDepth(0), NextCallIndex(1),
794  StepsLeft(getLangOpts().ConstexprStepLimit),
795  BottomFrame(*this, SourceLocation(), nullptr, nullptr, nullptr),
796  EvaluatingDecl((const ValueDecl *)nullptr),
797  EvaluatingDeclValue(nullptr), HasActiveDiagnostic(false),
798  HasFoldFailureDiagnostic(false), IsSpeculativelyEvaluating(false),
799  InConstantContext(false), EvalMode(Mode) {}
800 
801  void setEvaluatingDecl(APValue::LValueBase Base, APValue &Value) {
802  EvaluatingDecl = Base;
803  EvaluatingDeclValue = &Value;
804  EvaluatingConstructors.insert({Base, {0, 0}});
805  }
806 
807  const LangOptions &getLangOpts() const { return Ctx.getLangOpts(); }
808 
809  bool CheckCallLimit(SourceLocation Loc) {
810  // Don't perform any constexpr calls (other than the call we're checking)
811  // when checking a potential constant expression.
812  if (checkingPotentialConstantExpression() && CallStackDepth > 1)
813  return false;
814  if (NextCallIndex == 0) {
815  // NextCallIndex has wrapped around.
816  FFDiag(Loc, diag::note_constexpr_call_limit_exceeded);
817  return false;
818  }
819  if (CallStackDepth <= getLangOpts().ConstexprCallDepth)
820  return true;
821  FFDiag(Loc, diag::note_constexpr_depth_limit_exceeded)
822  << getLangOpts().ConstexprCallDepth;
823  return false;
824  }
825 
826  CallStackFrame *getCallFrame(unsigned CallIndex) {
827  assert(CallIndex && "no call index in getCallFrame");
828  // We will eventually hit BottomFrame, which has Index 1, so Frame can't
829  // be null in this loop.
830  CallStackFrame *Frame = CurrentCall;
831  while (Frame->Index > CallIndex)
832  Frame = Frame->Caller;
833  return (Frame->Index == CallIndex) ? Frame : nullptr;
834  }
835 
836  bool nextStep(const Stmt *S) {
837  if (!StepsLeft) {
838  FFDiag(S->getBeginLoc(), diag::note_constexpr_step_limit_exceeded);
839  return false;
840  }
841  --StepsLeft;
842  return true;
843  }
844 
845  private:
846  /// Add a diagnostic to the diagnostics list.
847  PartialDiagnostic &addDiag(SourceLocation Loc, diag::kind DiagId) {
848  PartialDiagnostic PD(DiagId, Ctx.getDiagAllocator());
849  EvalStatus.Diag->push_back(std::make_pair(Loc, PD));
850  return EvalStatus.Diag->back().second;
851  }
852 
853  /// Add notes containing a call stack to the current point of evaluation.
854  void addCallStack(unsigned Limit);
855 
856  private:
857  OptionalDiagnostic Diag(SourceLocation Loc, diag::kind DiagId,
858  unsigned ExtraNotes, bool IsCCEDiag) {
859 
860  if (EvalStatus.Diag) {
861  // If we have a prior diagnostic, it will be noting that the expression
862  // isn't a constant expression. This diagnostic is more important,
863  // unless we require this evaluation to produce a constant expression.
864  //
865  // FIXME: We might want to show both diagnostics to the user in
866  // EM_ConstantFold mode.
867  if (!EvalStatus.Diag->empty()) {
868  switch (EvalMode) {
869  case EM_ConstantFold:
870  case EM_IgnoreSideEffects:
871  case EM_EvaluateForOverflow:
872  if (!HasFoldFailureDiagnostic)
873  break;
874  // We've already failed to fold something. Keep that diagnostic.
875  LLVM_FALLTHROUGH;
876  case EM_ConstantExpression:
877  case EM_PotentialConstantExpression:
878  case EM_ConstantExpressionUnevaluated:
879  case EM_PotentialConstantExpressionUnevaluated:
880  HasActiveDiagnostic = false;
881  return OptionalDiagnostic();
882  }
883  }
884 
885  unsigned CallStackNotes = CallStackDepth - 1;
886  unsigned Limit = Ctx.getDiagnostics().getConstexprBacktraceLimit();
887  if (Limit)
888  CallStackNotes = std::min(CallStackNotes, Limit + 1);
889  if (checkingPotentialConstantExpression())
890  CallStackNotes = 0;
891 
892  HasActiveDiagnostic = true;
893  HasFoldFailureDiagnostic = !IsCCEDiag;
894  EvalStatus.Diag->clear();
895  EvalStatus.Diag->reserve(1 + ExtraNotes + CallStackNotes);
896  addDiag(Loc, DiagId);
897  if (!checkingPotentialConstantExpression())
898  addCallStack(Limit);
899  return OptionalDiagnostic(&(*EvalStatus.Diag)[0].second);
900  }
901  HasActiveDiagnostic = false;
902  return OptionalDiagnostic();
903  }
904  public:
905  // Diagnose that the evaluation could not be folded (FF => FoldFailure)
906  OptionalDiagnostic
907  FFDiag(SourceLocation Loc,
908  diag::kind DiagId = diag::note_invalid_subexpr_in_const_expr,
909  unsigned ExtraNotes = 0) {
910  return Diag(Loc, DiagId, ExtraNotes, false);
911  }
912 
913  OptionalDiagnostic FFDiag(const Expr *E, diag::kind DiagId
914  = diag::note_invalid_subexpr_in_const_expr,
915  unsigned ExtraNotes = 0) {
916  if (EvalStatus.Diag)
917  return Diag(E->getExprLoc(), DiagId, ExtraNotes, /*IsCCEDiag*/false);
918  HasActiveDiagnostic = false;
919  return OptionalDiagnostic();
920  }
921 
922  /// Diagnose that the evaluation does not produce a C++11 core constant
923  /// expression.
924  ///
925  /// FIXME: Stop evaluating if we're in EM_ConstantExpression or
926  /// EM_PotentialConstantExpression mode and we produce one of these.
927  OptionalDiagnostic CCEDiag(SourceLocation Loc, diag::kind DiagId
928  = diag::note_invalid_subexpr_in_const_expr,
929  unsigned ExtraNotes = 0) {
930  // Don't override a previous diagnostic. Don't bother collecting
931  // diagnostics if we're evaluating for overflow.
932  if (!EvalStatus.Diag || !EvalStatus.Diag->empty()) {
933  HasActiveDiagnostic = false;
934  return OptionalDiagnostic();
935  }
936  return Diag(Loc, DiagId, ExtraNotes, true);
937  }
938  OptionalDiagnostic CCEDiag(const Expr *E, diag::kind DiagId
939  = diag::note_invalid_subexpr_in_const_expr,
940  unsigned ExtraNotes = 0) {
941  return CCEDiag(E->getExprLoc(), DiagId, ExtraNotes);
942  }
943  /// Add a note to a prior diagnostic.
944  OptionalDiagnostic Note(SourceLocation Loc, diag::kind DiagId) {
945  if (!HasActiveDiagnostic)
946  return OptionalDiagnostic();
947  return OptionalDiagnostic(&addDiag(Loc, DiagId));
948  }
949 
950  /// Add a stack of notes to a prior diagnostic.
951  void addNotes(ArrayRef<PartialDiagnosticAt> Diags) {
952  if (HasActiveDiagnostic) {
953  EvalStatus.Diag->insert(EvalStatus.Diag->end(),
954  Diags.begin(), Diags.end());
955  }
956  }
957 
958  /// Should we continue evaluation after encountering a side-effect that we
959  /// couldn't model?
960  bool keepEvaluatingAfterSideEffect() {
961  switch (EvalMode) {
962  case EM_PotentialConstantExpression:
963  case EM_PotentialConstantExpressionUnevaluated:
964  case EM_EvaluateForOverflow:
965  case EM_IgnoreSideEffects:
966  return true;
967 
968  case EM_ConstantExpression:
969  case EM_ConstantExpressionUnevaluated:
970  case EM_ConstantFold:
971  return false;
972  }
973  llvm_unreachable("Missed EvalMode case");
974  }
975 
976  /// Note that we have had a side-effect, and determine whether we should
977  /// keep evaluating.
978  bool noteSideEffect() {
979  EvalStatus.HasSideEffects = true;
980  return keepEvaluatingAfterSideEffect();
981  }
982 
983  /// Should we continue evaluation after encountering undefined behavior?
984  bool keepEvaluatingAfterUndefinedBehavior() {
985  switch (EvalMode) {
986  case EM_EvaluateForOverflow:
987  case EM_IgnoreSideEffects:
988  case EM_ConstantFold:
989  return true;
990 
991  case EM_PotentialConstantExpression:
992  case EM_PotentialConstantExpressionUnevaluated:
993  case EM_ConstantExpression:
994  case EM_ConstantExpressionUnevaluated:
995  return false;
996  }
997  llvm_unreachable("Missed EvalMode case");
998  }
999 
1000  /// Note that we hit something that was technically undefined behavior, but
1001  /// that we can evaluate past it (such as signed overflow or floating-point
1002  /// division by zero.)
1003  bool noteUndefinedBehavior() {
1004  EvalStatus.HasUndefinedBehavior = true;
1005  return keepEvaluatingAfterUndefinedBehavior();
1006  }
1007 
1008  /// Should we continue evaluation as much as possible after encountering a
1009  /// construct which can't be reduced to a value?
1010  bool keepEvaluatingAfterFailure() {
1011  if (!StepsLeft)
1012  return false;
1013 
1014  switch (EvalMode) {
1015  case EM_PotentialConstantExpression:
1016  case EM_PotentialConstantExpressionUnevaluated:
1017  case EM_EvaluateForOverflow:
1018  return true;
1019 
1020  case EM_ConstantExpression:
1021  case EM_ConstantExpressionUnevaluated:
1022  case EM_ConstantFold:
1023  case EM_IgnoreSideEffects:
1024  return false;
1025  }
1026  llvm_unreachable("Missed EvalMode case");
1027  }
1028 
1029  /// Notes that we failed to evaluate an expression that other expressions
1030  /// directly depend on, and determine if we should keep evaluating. This
1031  /// should only be called if we actually intend to keep evaluating.
1032  ///
1033  /// Call noteSideEffect() instead if we may be able to ignore the value that
1034  /// we failed to evaluate, e.g. if we failed to evaluate Foo() in:
1035  ///
1036  /// (Foo(), 1) // use noteSideEffect
1037  /// (Foo() || true) // use noteSideEffect
1038  /// Foo() + 1 // use noteFailure
1039  LLVM_NODISCARD bool noteFailure() {
1040  // Failure when evaluating some expression often means there is some
1041  // subexpression whose evaluation was skipped. Therefore, (because we
1042  // don't track whether we skipped an expression when unwinding after an
1043  // evaluation failure) every evaluation failure that bubbles up from a
1044  // subexpression implies that a side-effect has potentially happened. We
1045  // skip setting the HasSideEffects flag to true until we decide to
1046  // continue evaluating after that point, which happens here.
1047  bool KeepGoing = keepEvaluatingAfterFailure();
1048  EvalStatus.HasSideEffects |= KeepGoing;
1049  return KeepGoing;
1050  }
1051 
1052  class ArrayInitLoopIndex {
1053  EvalInfo &Info;
1054  uint64_t OuterIndex;
1055 
1056  public:
1057  ArrayInitLoopIndex(EvalInfo &Info)
1058  : Info(Info), OuterIndex(Info.ArrayInitIndex) {
1059  Info.ArrayInitIndex = 0;
1060  }
1061  ~ArrayInitLoopIndex() { Info.ArrayInitIndex = OuterIndex; }
1062 
1063  operator uint64_t&() { return Info.ArrayInitIndex; }
1064  };
1065  };
1066 
1067  /// Object used to treat all foldable expressions as constant expressions.
1068  struct FoldConstant {
1069  EvalInfo &Info;
1070  bool Enabled;
1071  bool HadNoPriorDiags;
1072  EvalInfo::EvaluationMode OldMode;
1073 
1074  explicit FoldConstant(EvalInfo &Info, bool Enabled)
1075  : Info(Info),
1076  Enabled(Enabled),
1077  HadNoPriorDiags(Info.EvalStatus.Diag &&
1078  Info.EvalStatus.Diag->empty() &&
1079  !Info.EvalStatus.HasSideEffects),
1080  OldMode(Info.EvalMode) {
1081  if (Enabled &&
1082  (Info.EvalMode == EvalInfo::EM_ConstantExpression ||
1083  Info.EvalMode == EvalInfo::EM_ConstantExpressionUnevaluated))
1084  Info.EvalMode = EvalInfo::EM_ConstantFold;
1085  }
1086  void keepDiagnostics() { Enabled = false; }
1087  ~FoldConstant() {
1088  if (Enabled && HadNoPriorDiags && !Info.EvalStatus.Diag->empty() &&
1089  !Info.EvalStatus.HasSideEffects)
1090  Info.EvalStatus.Diag->clear();
1091  Info.EvalMode = OldMode;
1092  }
1093  };
1094 
1095  /// RAII object used to set the current evaluation mode to ignore
1096  /// side-effects.
1097  struct IgnoreSideEffectsRAII {
1098  EvalInfo &Info;
1099  EvalInfo::EvaluationMode OldMode;
1100  explicit IgnoreSideEffectsRAII(EvalInfo &Info)
1101  : Info(Info), OldMode(Info.EvalMode) {
1102  if (!Info.checkingPotentialConstantExpression())
1103  Info.EvalMode = EvalInfo::EM_IgnoreSideEffects;
1104  }
1105 
1106  ~IgnoreSideEffectsRAII() { Info.EvalMode = OldMode; }
1107  };
1108 
1109  /// RAII object used to optionally suppress diagnostics and side-effects from
1110  /// a speculative evaluation.
1111  class SpeculativeEvaluationRAII {
1112  EvalInfo *Info = nullptr;
1113  Expr::EvalStatus OldStatus;
1114  bool OldIsSpeculativelyEvaluating;
1115 
1116  void moveFromAndCancel(SpeculativeEvaluationRAII &&Other) {
1117  Info = Other.Info;
1118  OldStatus = Other.OldStatus;
1119  OldIsSpeculativelyEvaluating = Other.OldIsSpeculativelyEvaluating;
1120  Other.Info = nullptr;
1121  }
1122 
1123  void maybeRestoreState() {
1124  if (!Info)
1125  return;
1126 
1127  Info->EvalStatus = OldStatus;
1128  Info->IsSpeculativelyEvaluating = OldIsSpeculativelyEvaluating;
1129  }
1130 
1131  public:
1132  SpeculativeEvaluationRAII() = default;
1133 
1134  SpeculativeEvaluationRAII(
1135  EvalInfo &Info, SmallVectorImpl<PartialDiagnosticAt> *NewDiag = nullptr)
1136  : Info(&Info), OldStatus(Info.EvalStatus),
1137  OldIsSpeculativelyEvaluating(Info.IsSpeculativelyEvaluating) {
1138  Info.EvalStatus.Diag = NewDiag;
1139  Info.IsSpeculativelyEvaluating = true;
1140  }
1141 
1142  SpeculativeEvaluationRAII(const SpeculativeEvaluationRAII &Other) = delete;
1143  SpeculativeEvaluationRAII(SpeculativeEvaluationRAII &&Other) {
1144  moveFromAndCancel(std::move(Other));
1145  }
1146 
1147  SpeculativeEvaluationRAII &operator=(SpeculativeEvaluationRAII &&Other) {
1148  maybeRestoreState();
1149  moveFromAndCancel(std::move(Other));
1150  return *this;
1151  }
1152 
1153  ~SpeculativeEvaluationRAII() { maybeRestoreState(); }
1154  };
1155 
1156  /// RAII object wrapping a full-expression or block scope, and handling
1157  /// the ending of the lifetime of temporaries created within it.
1158  template<bool IsFullExpression>
1159  class ScopeRAII {
1160  EvalInfo &Info;
1161  unsigned OldStackSize;
1162  public:
1163  ScopeRAII(EvalInfo &Info)
1164  : Info(Info), OldStackSize(Info.CleanupStack.size()) {
1165  // Push a new temporary version. This is needed to distinguish between
1166  // temporaries created in different iterations of a loop.
1167  Info.CurrentCall->pushTempVersion();
1168  }
1169  ~ScopeRAII() {
1170  // Body moved to a static method to encourage the compiler to inline away
1171  // instances of this class.
1172  cleanup(Info, OldStackSize);
1173  Info.CurrentCall->popTempVersion();
1174  }
1175  private:
1176  static void cleanup(EvalInfo &Info, unsigned OldStackSize) {
1177  unsigned NewEnd = OldStackSize;
1178  for (unsigned I = OldStackSize, N = Info.CleanupStack.size();
1179  I != N; ++I) {
1180  if (IsFullExpression && Info.CleanupStack[I].isLifetimeExtended()) {
1181  // Full-expression cleanup of a lifetime-extended temporary: nothing
1182  // to do, just move this cleanup to the right place in the stack.
1183  std::swap(Info.CleanupStack[I], Info.CleanupStack[NewEnd]);
1184  ++NewEnd;
1185  } else {
1186  // End the lifetime of the object.
1187  Info.CleanupStack[I].endLifetime();
1188  }
1189  }
1190  Info.CleanupStack.erase(Info.CleanupStack.begin() + NewEnd,
1191  Info.CleanupStack.end());
1192  }
1193  };
1194  typedef ScopeRAII<false> BlockScopeRAII;
1195  typedef ScopeRAII<true> FullExpressionRAII;
1196 }
1197 
1198 bool SubobjectDesignator::checkSubobject(EvalInfo &Info, const Expr *E,
1199  CheckSubobjectKind CSK) {
1200  if (Invalid)
1201  return false;
1202  if (isOnePastTheEnd()) {
1203  Info.CCEDiag(E, diag::note_constexpr_past_end_subobject)
1204  << CSK;
1205  setInvalid();
1206  return false;
1207  }
1208  // Note, we do not diagnose if isMostDerivedAnUnsizedArray(), because there
1209  // must actually be at least one array element; even a VLA cannot have a
1210  // bound of zero. And if our index is nonzero, we already had a CCEDiag.
1211  return true;
1212 }
1213 
1214 void SubobjectDesignator::diagnoseUnsizedArrayPointerArithmetic(EvalInfo &Info,
1215  const Expr *E) {
1216  Info.CCEDiag(E, diag::note_constexpr_unsized_array_indexed);
1217  // Do not set the designator as invalid: we can represent this situation,
1218  // and correct handling of __builtin_object_size requires us to do so.
1219 }
1220 
1221 void SubobjectDesignator::diagnosePointerArithmetic(EvalInfo &Info,
1222  const Expr *E,
1223  const APSInt &N) {
1224  // If we're complaining, we must be able to statically determine the size of
1225  // the most derived array.
1226  if (MostDerivedPathLength == Entries.size() && MostDerivedIsArrayElement)
1227  Info.CCEDiag(E, diag::note_constexpr_array_index)
1228  << N << /*array*/ 0
1229  << static_cast<unsigned>(getMostDerivedArraySize());
1230  else
1231  Info.CCEDiag(E, diag::note_constexpr_array_index)
1232  << N << /*non-array*/ 1;
1233  setInvalid();
1234 }
1235 
1236 CallStackFrame::CallStackFrame(EvalInfo &Info, SourceLocation CallLoc,
1237  const FunctionDecl *Callee, const LValue *This,
1238  APValue *Arguments)
1239  : Info(Info), Caller(Info.CurrentCall), Callee(Callee), This(This),
1240  Arguments(Arguments), CallLoc(CallLoc), Index(Info.NextCallIndex++) {
1241  Info.CurrentCall = this;
1242  ++Info.CallStackDepth;
1243 }
1244 
1245 CallStackFrame::~CallStackFrame() {
1246  assert(Info.CurrentCall == this && "calls retired out of order");
1247  --Info.CallStackDepth;
1248  Info.CurrentCall = Caller;
1249 }
1250 
1251 APValue &CallStackFrame::createTemporary(const void *Key,
1252  bool IsLifetimeExtended) {
1253  unsigned Version = Info.CurrentCall->getTempVersion();
1254  APValue &Result = Temporaries[MapKeyTy(Key, Version)];
1255  assert(Result.isUninit() && "temporary created multiple times");
1256  Info.CleanupStack.push_back(Cleanup(&Result, IsLifetimeExtended));
1257  return Result;
1258 }
1259 
1260 static void describeCall(CallStackFrame *Frame, raw_ostream &Out);
1261 
1262 void EvalInfo::addCallStack(unsigned Limit) {
1263  // Determine which calls to skip, if any.
1264  unsigned ActiveCalls = CallStackDepth - 1;
1265  unsigned SkipStart = ActiveCalls, SkipEnd = SkipStart;
1266  if (Limit && Limit < ActiveCalls) {
1267  SkipStart = Limit / 2 + Limit % 2;
1268  SkipEnd = ActiveCalls - Limit / 2;
1269  }
1270 
1271  // Walk the call stack and add the diagnostics.
1272  unsigned CallIdx = 0;
1273  for (CallStackFrame *Frame = CurrentCall; Frame != &BottomFrame;
1274  Frame = Frame->Caller, ++CallIdx) {
1275  // Skip this call?
1276  if (CallIdx >= SkipStart && CallIdx < SkipEnd) {
1277  if (CallIdx == SkipStart) {
1278  // Note that we're skipping calls.
1279  addDiag(Frame->CallLoc, diag::note_constexpr_calls_suppressed)
1280  << unsigned(ActiveCalls - Limit);
1281  }
1282  continue;
1283  }
1284 
1285  // Use a different note for an inheriting constructor, because from the
1286  // user's perspective it's not really a function at all.
1287  if (auto *CD = dyn_cast_or_null<CXXConstructorDecl>(Frame->Callee)) {
1288  if (CD->isInheritingConstructor()) {
1289  addDiag(Frame->CallLoc, diag::note_constexpr_inherited_ctor_call_here)
1290  << CD->getParent();
1291  continue;
1292  }
1293  }
1294 
1295  SmallVector<char, 128> Buffer;
1296  llvm::raw_svector_ostream Out(Buffer);
1297  describeCall(Frame, Out);
1298  addDiag(Frame->CallLoc, diag::note_constexpr_call_here) << Out.str();
1299  }
1300 }
1301 
1302 /// Kinds of access we can perform on an object, for diagnostics.
1308 };
1309 
1310 namespace {
1311  struct ComplexValue {
1312  private:
1313  bool IsInt;
1314 
1315  public:
1316  APSInt IntReal, IntImag;
1317  APFloat FloatReal, FloatImag;
1318 
1319  ComplexValue() : FloatReal(APFloat::Bogus()), FloatImag(APFloat::Bogus()) {}
1320 
1321  void makeComplexFloat() { IsInt = false; }
1322  bool isComplexFloat() const { return !IsInt; }
1323  APFloat &getComplexFloatReal() { return FloatReal; }
1324  APFloat &getComplexFloatImag() { return FloatImag; }
1325 
1326  void makeComplexInt() { IsInt = true; }
1327  bool isComplexInt() const { return IsInt; }
1328  APSInt &getComplexIntReal() { return IntReal; }
1329  APSInt &getComplexIntImag() { return IntImag; }
1330 
1331  void moveInto(APValue &v) const {
1332  if (isComplexFloat())
1333  v = APValue(FloatReal, FloatImag);
1334  else
1335  v = APValue(IntReal, IntImag);
1336  }
1337  void setFrom(const APValue &v) {
1338  assert(v.isComplexFloat() || v.isComplexInt());
1339  if (v.isComplexFloat()) {
1340  makeComplexFloat();
1341  FloatReal = v.getComplexFloatReal();
1342  FloatImag = v.getComplexFloatImag();
1343  } else {
1344  makeComplexInt();
1345  IntReal = v.getComplexIntReal();
1346  IntImag = v.getComplexIntImag();
1347  }
1348  }
1349  };
1350 
1351  struct LValue {
1352  APValue::LValueBase Base;
1353  CharUnits Offset;
1354  SubobjectDesignator Designator;
1355  bool IsNullPtr : 1;
1356  bool InvalidBase : 1;
1357 
1358  const APValue::LValueBase getLValueBase() const { return Base; }
1359  CharUnits &getLValueOffset() { return Offset; }
1360  const CharUnits &getLValueOffset() const { return Offset; }
1361  SubobjectDesignator &getLValueDesignator() { return Designator; }
1362  const SubobjectDesignator &getLValueDesignator() const { return Designator;}
1363  bool isNullPointer() const { return IsNullPtr;}
1364 
1365  unsigned getLValueCallIndex() const { return Base.getCallIndex(); }
1366  unsigned getLValueVersion() const { return Base.getVersion(); }
1367 
1368  void moveInto(APValue &V) const {
1369  if (Designator.Invalid)
1370  V = APValue(Base, Offset, APValue::NoLValuePath(), IsNullPtr);
1371  else {
1372  assert(!InvalidBase && "APValues can't handle invalid LValue bases");
1373  V = APValue(Base, Offset, Designator.Entries,
1374  Designator.IsOnePastTheEnd, IsNullPtr);
1375  }
1376  }
1377  void setFrom(ASTContext &Ctx, const APValue &V) {
1378  assert(V.isLValue() && "Setting LValue from a non-LValue?");
1379  Base = V.getLValueBase();
1380  Offset = V.getLValueOffset();
1381  InvalidBase = false;
1382  Designator = SubobjectDesignator(Ctx, V);
1383  IsNullPtr = V.isNullPointer();
1384  }
1385 
1386  void set(APValue::LValueBase B, bool BInvalid = false) {
1387 #ifndef NDEBUG
1388  // We only allow a few types of invalid bases. Enforce that here.
1389  if (BInvalid) {
1390  const auto *E = B.get<const Expr *>();
1391  assert((isa<MemberExpr>(E) || tryUnwrapAllocSizeCall(E)) &&
1392  "Unexpected type of invalid base");
1393  }
1394 #endif
1395 
1396  Base = B;
1397  Offset = CharUnits::fromQuantity(0);
1398  InvalidBase = BInvalid;
1399  Designator = SubobjectDesignator(getType(B));
1400  IsNullPtr = false;
1401  }
1402 
1403  void setNull(QualType PointerTy, uint64_t TargetVal) {
1404  Base = (Expr *)nullptr;
1405  Offset = CharUnits::fromQuantity(TargetVal);
1406  InvalidBase = false;
1407  Designator = SubobjectDesignator(PointerTy->getPointeeType());
1408  IsNullPtr = true;
1409  }
1410 
1411  void setInvalid(APValue::LValueBase B, unsigned I = 0) {
1412  set(B, true);
1413  }
1414 
1415  private:
1416  // Check that this LValue is not based on a null pointer. If it is, produce
1417  // a diagnostic and mark the designator as invalid.
1418  template <typename GenDiagType>
1419  bool checkNullPointerDiagnosingWith(const GenDiagType &GenDiag) {
1420  if (Designator.Invalid)
1421  return false;
1422  if (IsNullPtr) {
1423  GenDiag();
1424  Designator.setInvalid();
1425  return false;
1426  }
1427  return true;
1428  }
1429 
1430  public:
1431  bool checkNullPointer(EvalInfo &Info, const Expr *E,
1432  CheckSubobjectKind CSK) {
1433  return checkNullPointerDiagnosingWith([&Info, E, CSK] {
1434  Info.CCEDiag(E, diag::note_constexpr_null_subobject) << CSK;
1435  });
1436  }
1437 
1438  bool checkNullPointerForFoldAccess(EvalInfo &Info, const Expr *E,
1439  AccessKinds AK) {
1440  return checkNullPointerDiagnosingWith([&Info, E, AK] {
1441  Info.FFDiag(E, diag::note_constexpr_access_null) << AK;
1442  });
1443  }
1444 
1445  // Check this LValue refers to an object. If not, set the designator to be
1446  // invalid and emit a diagnostic.
1447  bool checkSubobject(EvalInfo &Info, const Expr *E, CheckSubobjectKind CSK) {
1448  return (CSK == CSK_ArrayToPointer || checkNullPointer(Info, E, CSK)) &&
1449  Designator.checkSubobject(Info, E, CSK);
1450  }
1451 
1452  void addDecl(EvalInfo &Info, const Expr *E,
1453  const Decl *D, bool Virtual = false) {
1454  if (checkSubobject(Info, E, isa<FieldDecl>(D) ? CSK_Field : CSK_Base))
1455  Designator.addDeclUnchecked(D, Virtual);
1456  }
1457  void addUnsizedArray(EvalInfo &Info, const Expr *E, QualType ElemTy) {
1458  if (!Designator.Entries.empty()) {
1459  Info.CCEDiag(E, diag::note_constexpr_unsupported_unsized_array);
1460  Designator.setInvalid();
1461  return;
1462  }
1463  if (checkSubobject(Info, E, CSK_ArrayToPointer)) {
1464  assert(getType(Base)->isPointerType() || getType(Base)->isArrayType());
1465  Designator.FirstEntryIsAnUnsizedArray = true;
1466  Designator.addUnsizedArrayUnchecked(ElemTy);
1467  }
1468  }
1469  void addArray(EvalInfo &Info, const Expr *E, const ConstantArrayType *CAT) {
1470  if (checkSubobject(Info, E, CSK_ArrayToPointer))
1471  Designator.addArrayUnchecked(CAT);
1472  }
1473  void addComplex(EvalInfo &Info, const Expr *E, QualType EltTy, bool Imag) {
1474  if (checkSubobject(Info, E, Imag ? CSK_Imag : CSK_Real))
1475  Designator.addComplexUnchecked(EltTy, Imag);
1476  }
1477  void clearIsNullPointer() {
1478  IsNullPtr = false;
1479  }
1480  void adjustOffsetAndIndex(EvalInfo &Info, const Expr *E,
1481  const APSInt &Index, CharUnits ElementSize) {
1482  // An index of 0 has no effect. (In C, adding 0 to a null pointer is UB,
1483  // but we're not required to diagnose it and it's valid in C++.)
1484  if (!Index)
1485  return;
1486 
1487  // Compute the new offset in the appropriate width, wrapping at 64 bits.
1488  // FIXME: When compiling for a 32-bit target, we should use 32-bit
1489  // offsets.
1490  uint64_t Offset64 = Offset.getQuantity();
1491  uint64_t ElemSize64 = ElementSize.getQuantity();
1492  uint64_t Index64 = Index.extOrTrunc(64).getZExtValue();
1493  Offset = CharUnits::fromQuantity(Offset64 + ElemSize64 * Index64);
1494 
1495  if (checkNullPointer(Info, E, CSK_ArrayIndex))
1496  Designator.adjustIndex(Info, E, Index);
1497  clearIsNullPointer();
1498  }
1499  void adjustOffset(CharUnits N) {
1500  Offset += N;
1501  if (N.getQuantity())
1502  clearIsNullPointer();
1503  }
1504  };
1505 
1506  struct MemberPtr {
1507  MemberPtr() {}
1508  explicit MemberPtr(const ValueDecl *Decl) :
1509  DeclAndIsDerivedMember(Decl, false), Path() {}
1510 
1511  /// The member or (direct or indirect) field referred to by this member
1512  /// pointer, or 0 if this is a null member pointer.
1513  const ValueDecl *getDecl() const {
1514  return DeclAndIsDerivedMember.getPointer();
1515  }
1516  /// Is this actually a member of some type derived from the relevant class?
1517  bool isDerivedMember() const {
1518  return DeclAndIsDerivedMember.getInt();
1519  }
1520  /// Get the class which the declaration actually lives in.
1521  const CXXRecordDecl *getContainingRecord() const {
1522  return cast<CXXRecordDecl>(
1523  DeclAndIsDerivedMember.getPointer()->getDeclContext());
1524  }
1525 
1526  void moveInto(APValue &V) const {
1527  V = APValue(getDecl(), isDerivedMember(), Path);
1528  }
1529  void setFrom(const APValue &V) {
1530  assert(V.isMemberPointer());
1531  DeclAndIsDerivedMember.setPointer(V.getMemberPointerDecl());
1532  DeclAndIsDerivedMember.setInt(V.isMemberPointerToDerivedMember());
1533  Path.clear();
1535  Path.insert(Path.end(), P.begin(), P.end());
1536  }
1537 
1538  /// DeclAndIsDerivedMember - The member declaration, and a flag indicating
1539  /// whether the member is a member of some class derived from the class type
1540  /// of the member pointer.
1541  llvm::PointerIntPair<const ValueDecl*, 1, bool> DeclAndIsDerivedMember;
1542  /// Path - The path of base/derived classes from the member declaration's
1543  /// class (exclusive) to the class type of the member pointer (inclusive).
1545 
1546  /// Perform a cast towards the class of the Decl (either up or down the
1547  /// hierarchy).
1548  bool castBack(const CXXRecordDecl *Class) {
1549  assert(!Path.empty());
1550  const CXXRecordDecl *Expected;
1551  if (Path.size() >= 2)
1552  Expected = Path[Path.size() - 2];
1553  else
1554  Expected = getContainingRecord();
1555  if (Expected->getCanonicalDecl() != Class->getCanonicalDecl()) {
1556  // C++11 [expr.static.cast]p12: In a conversion from (D::*) to (B::*),
1557  // if B does not contain the original member and is not a base or
1558  // derived class of the class containing the original member, the result
1559  // of the cast is undefined.
1560  // C++11 [conv.mem]p2 does not cover this case for a cast from (B::*) to
1561  // (D::*). We consider that to be a language defect.
1562  return false;
1563  }
1564  Path.pop_back();
1565  return true;
1566  }
1567  /// Perform a base-to-derived member pointer cast.
1568  bool castToDerived(const CXXRecordDecl *Derived) {
1569  if (!getDecl())
1570  return true;
1571  if (!isDerivedMember()) {
1572  Path.push_back(Derived);
1573  return true;
1574  }
1575  if (!castBack(Derived))
1576  return false;
1577  if (Path.empty())
1578  DeclAndIsDerivedMember.setInt(false);
1579  return true;
1580  }
1581  /// Perform a derived-to-base member pointer cast.
1582  bool castToBase(const CXXRecordDecl *Base) {
1583  if (!getDecl())
1584  return true;
1585  if (Path.empty())
1586  DeclAndIsDerivedMember.setInt(true);
1587  if (isDerivedMember()) {
1588  Path.push_back(Base);
1589  return true;
1590  }
1591  return castBack(Base);
1592  }
1593  };
1594 
1595  /// Compare two member pointers, which are assumed to be of the same type.
1596  static bool operator==(const MemberPtr &LHS, const MemberPtr &RHS) {
1597  if (!LHS.getDecl() || !RHS.getDecl())
1598  return !LHS.getDecl() && !RHS.getDecl();
1599  if (LHS.getDecl()->getCanonicalDecl() != RHS.getDecl()->getCanonicalDecl())
1600  return false;
1601  return LHS.Path == RHS.Path;
1602  }
1603 }
1604 
1605 static bool Evaluate(APValue &Result, EvalInfo &Info, const Expr *E);
1606 static bool EvaluateInPlace(APValue &Result, EvalInfo &Info,
1607  const LValue &This, const Expr *E,
1608  bool AllowNonLiteralTypes = false);
1609 static bool EvaluateLValue(const Expr *E, LValue &Result, EvalInfo &Info,
1610  bool InvalidBaseOK = false);
1611 static bool EvaluatePointer(const Expr *E, LValue &Result, EvalInfo &Info,
1612  bool InvalidBaseOK = false);
1613 static bool EvaluateMemberPointer(const Expr *E, MemberPtr &Result,
1614  EvalInfo &Info);
1615 static bool EvaluateTemporary(const Expr *E, LValue &Result, EvalInfo &Info);
1616 static bool EvaluateInteger(const Expr *E, APSInt &Result, EvalInfo &Info);
1617 static bool EvaluateIntegerOrLValue(const Expr *E, APValue &Result,
1618  EvalInfo &Info);
1619 static bool EvaluateFloat(const Expr *E, APFloat &Result, EvalInfo &Info);
1620 static bool EvaluateComplex(const Expr *E, ComplexValue &Res, EvalInfo &Info);
1621 static bool EvaluateAtomic(const Expr *E, const LValue *This, APValue &Result,
1622  EvalInfo &Info);
1623 static bool EvaluateAsRValue(EvalInfo &Info, const Expr *E, APValue &Result);
1624 
1625 /// Evaluate an integer or fixed point expression into an APResult.
1626 static bool EvaluateFixedPointOrInteger(const Expr *E, APFixedPoint &Result,
1627  EvalInfo &Info);
1628 
1629 /// Evaluate only a fixed point expression into an APResult.
1630 static bool EvaluateFixedPoint(const Expr *E, APFixedPoint &Result,
1631  EvalInfo &Info);
1632 
1633 //===----------------------------------------------------------------------===//
1634 // Misc utilities
1635 //===----------------------------------------------------------------------===//
1636 
1637 /// A helper function to create a temporary and set an LValue.
1638 template <class KeyTy>
1639 static APValue &createTemporary(const KeyTy *Key, bool IsLifetimeExtended,
1640  LValue &LV, CallStackFrame &Frame) {
1641  LV.set({Key, Frame.Info.CurrentCall->Index,
1642  Frame.Info.CurrentCall->getTempVersion()});
1643  return Frame.createTemporary(Key, IsLifetimeExtended);
1644 }
1645 
1646 /// Negate an APSInt in place, converting it to a signed form if necessary, and
1647 /// preserving its value (by extending by up to one bit as needed).
1648 static void negateAsSigned(APSInt &Int) {
1649  if (Int.isUnsigned() || Int.isMinSignedValue()) {
1650  Int = Int.extend(Int.getBitWidth() + 1);
1651  Int.setIsSigned(true);
1652  }
1653  Int = -Int;
1654 }
1655 
1656 /// Produce a string describing the given constexpr call.
1657 static void describeCall(CallStackFrame *Frame, raw_ostream &Out) {
1658  unsigned ArgIndex = 0;
1659  bool IsMemberCall = isa<CXXMethodDecl>(Frame->Callee) &&
1660  !isa<CXXConstructorDecl>(Frame->Callee) &&
1661  cast<CXXMethodDecl>(Frame->Callee)->isInstance();
1662 
1663  if (!IsMemberCall)
1664  Out << *Frame->Callee << '(';
1665 
1666  if (Frame->This && IsMemberCall) {
1667  APValue Val;
1668  Frame->This->moveInto(Val);
1669  Val.printPretty(Out, Frame->Info.Ctx,
1670  Frame->This->Designator.MostDerivedType);
1671  // FIXME: Add parens around Val if needed.
1672  Out << "->" << *Frame->Callee << '(';
1673  IsMemberCall = false;
1674  }
1675 
1676  for (FunctionDecl::param_const_iterator I = Frame->Callee->param_begin(),
1677  E = Frame->Callee->param_end(); I != E; ++I, ++ArgIndex) {
1678  if (ArgIndex > (unsigned)IsMemberCall)
1679  Out << ", ";
1680 
1681  const ParmVarDecl *Param = *I;
1682  const APValue &Arg = Frame->Arguments[ArgIndex];
1683  Arg.printPretty(Out, Frame->Info.Ctx, Param->getType());
1684 
1685  if (ArgIndex == 0 && IsMemberCall)
1686  Out << "->" << *Frame->Callee << '(';
1687  }
1688 
1689  Out << ')';
1690 }
1691 
1692 /// Evaluate an expression to see if it had side-effects, and discard its
1693 /// result.
1694 /// \return \c true if the caller should keep evaluating.
1695 static bool EvaluateIgnoredValue(EvalInfo &Info, const Expr *E) {
1696  APValue Scratch;
1697  if (!Evaluate(Scratch, Info, E))
1698  // We don't need the value, but we might have skipped a side effect here.
1699  return Info.noteSideEffect();
1700  return true;
1701 }
1702 
1703 /// Should this call expression be treated as a string literal?
1704 static bool IsStringLiteralCall(const CallExpr *E) {
1705  unsigned Builtin = E->getBuiltinCallee();
1706  return (Builtin == Builtin::BI__builtin___CFStringMakeConstantString ||
1707  Builtin == Builtin::BI__builtin___NSStringMakeConstantString);
1708 }
1709 
1711  // C++11 [expr.const]p3 An address constant expression is a prvalue core
1712  // constant expression of pointer type that evaluates to...
1713 
1714  // ... a null pointer value, or a prvalue core constant expression of type
1715  // std::nullptr_t.
1716  if (!B) return true;
1717 
1718  if (const ValueDecl *D = B.dyn_cast<const ValueDecl*>()) {
1719  // ... the address of an object with static storage duration,
1720  if (const VarDecl *VD = dyn_cast<VarDecl>(D))
1721  return VD->hasGlobalStorage();
1722  // ... the address of a function,
1723  return isa<FunctionDecl>(D);
1724  }
1725 
1726  const Expr *E = B.get<const Expr*>();
1727  switch (E->getStmtClass()) {
1728  default:
1729  return false;
1730  case Expr::CompoundLiteralExprClass: {
1731  const CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
1732  return CLE->isFileScope() && CLE->isLValue();
1733  }
1734  case Expr::MaterializeTemporaryExprClass:
1735  // A materialized temporary might have been lifetime-extended to static
1736  // storage duration.
1737  return cast<MaterializeTemporaryExpr>(E)->getStorageDuration() == SD_Static;
1738  // A string literal has static storage duration.
1739  case Expr::StringLiteralClass:
1740  case Expr::PredefinedExprClass:
1741  case Expr::ObjCStringLiteralClass:
1742  case Expr::ObjCEncodeExprClass:
1743  case Expr::CXXTypeidExprClass:
1744  case Expr::CXXUuidofExprClass:
1745  return true;
1746  case Expr::ObjCBoxedExprClass:
1747  return cast<ObjCBoxedExpr>(E)->isExpressibleAsConstantInitializer();
1748  case Expr::CallExprClass:
1749  return IsStringLiteralCall(cast<CallExpr>(E));
1750  // For GCC compatibility, &&label has static storage duration.
1751  case Expr::AddrLabelExprClass:
1752  return true;
1753  // A Block literal expression may be used as the initialization value for
1754  // Block variables at global or local static scope.
1755  case Expr::BlockExprClass:
1756  return !cast<BlockExpr>(E)->getBlockDecl()->hasCaptures();
1757  case Expr::ImplicitValueInitExprClass:
1758  // FIXME:
1759  // We can never form an lvalue with an implicit value initialization as its
1760  // base through expression evaluation, so these only appear in one case: the
1761  // implicit variable declaration we invent when checking whether a constexpr
1762  // constructor can produce a constant expression. We must assume that such
1763  // an expression might be a global lvalue.
1764  return true;
1765  }
1766 }
1767 
1768 static const ValueDecl *GetLValueBaseDecl(const LValue &LVal) {
1769  return LVal.Base.dyn_cast<const ValueDecl*>();
1770 }
1771 
1772 static bool IsLiteralLValue(const LValue &Value) {
1773  if (Value.getLValueCallIndex())
1774  return false;
1775  const Expr *E = Value.Base.dyn_cast<const Expr*>();
1776  return E && !isa<MaterializeTemporaryExpr>(E);
1777 }
1778 
1779 static bool IsWeakLValue(const LValue &Value) {
1780  const ValueDecl *Decl = GetLValueBaseDecl(Value);
1781  return Decl && Decl->isWeak();
1782 }
1783 
1784 static bool isZeroSized(const LValue &Value) {
1785  const ValueDecl *Decl = GetLValueBaseDecl(Value);
1786  if (Decl && isa<VarDecl>(Decl)) {
1787  QualType Ty = Decl->getType();
1788  if (Ty->isArrayType())
1789  return Ty->isIncompleteType() ||
1790  Decl->getASTContext().getTypeSize(Ty) == 0;
1791  }
1792  return false;
1793 }
1794 
1795 static bool HasSameBase(const LValue &A, const LValue &B) {
1796  if (!A.getLValueBase())
1797  return !B.getLValueBase();
1798  if (!B.getLValueBase())
1799  return false;
1800 
1801  if (A.getLValueBase().getOpaqueValue() !=
1802  B.getLValueBase().getOpaqueValue()) {
1803  const Decl *ADecl = GetLValueBaseDecl(A);
1804  if (!ADecl)
1805  return false;
1806  const Decl *BDecl = GetLValueBaseDecl(B);
1807  if (!BDecl || ADecl->getCanonicalDecl() != BDecl->getCanonicalDecl())
1808  return false;
1809  }
1810 
1811  return IsGlobalLValue(A.getLValueBase()) ||
1812  (A.getLValueCallIndex() == B.getLValueCallIndex() &&
1813  A.getLValueVersion() == B.getLValueVersion());
1814 }
1815 
1816 static void NoteLValueLocation(EvalInfo &Info, APValue::LValueBase Base) {
1817  assert(Base && "no location for a null lvalue");
1818  const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
1819  if (VD)
1820  Info.Note(VD->getLocation(), diag::note_declared_at);
1821  else
1822  Info.Note(Base.get<const Expr*>()->getExprLoc(),
1823  diag::note_constexpr_temporary_here);
1824 }
1825 
1826 /// Check that this reference or pointer core constant expression is a valid
1827 /// value for an address or reference constant expression. Return true if we
1828 /// can fold this expression, whether or not it's a constant expression.
1829 static bool CheckLValueConstantExpression(EvalInfo &Info, SourceLocation Loc,
1830  QualType Type, const LValue &LVal,
1831  Expr::ConstExprUsage Usage) {
1832  bool IsReferenceType = Type->isReferenceType();
1833 
1834  APValue::LValueBase Base = LVal.getLValueBase();
1835  const SubobjectDesignator &Designator = LVal.getLValueDesignator();
1836 
1837  // Check that the object is a global. Note that the fake 'this' object we
1838  // manufacture when checking potential constant expressions is conservatively
1839  // assumed to be global here.
1840  if (!IsGlobalLValue(Base)) {
1841  if (Info.getLangOpts().CPlusPlus11) {
1842  const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
1843  Info.FFDiag(Loc, diag::note_constexpr_non_global, 1)
1844  << IsReferenceType << !Designator.Entries.empty()
1845  << !!VD << VD;
1846  NoteLValueLocation(Info, Base);
1847  } else {
1848  Info.FFDiag(Loc);
1849  }
1850  // Don't allow references to temporaries to escape.
1851  return false;
1852  }
1853  assert((Info.checkingPotentialConstantExpression() ||
1854  LVal.getLValueCallIndex() == 0) &&
1855  "have call index for global lvalue");
1856 
1857  if (const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>()) {
1858  if (const VarDecl *Var = dyn_cast<const VarDecl>(VD)) {
1859  // Check if this is a thread-local variable.
1860  if (Var->getTLSKind())
1861  return false;
1862 
1863  // A dllimport variable never acts like a constant.
1864  if (Usage == Expr::EvaluateForCodeGen && Var->hasAttr<DLLImportAttr>())
1865  return false;
1866  }
1867  if (const auto *FD = dyn_cast<const FunctionDecl>(VD)) {
1868  // __declspec(dllimport) must be handled very carefully:
1869  // We must never initialize an expression with the thunk in C++.
1870  // Doing otherwise would allow the same id-expression to yield
1871  // different addresses for the same function in different translation
1872  // units. However, this means that we must dynamically initialize the
1873  // expression with the contents of the import address table at runtime.
1874  //
1875  // The C language has no notion of ODR; furthermore, it has no notion of
1876  // dynamic initialization. This means that we are permitted to
1877  // perform initialization with the address of the thunk.
1878  if (Info.getLangOpts().CPlusPlus && Usage == Expr::EvaluateForCodeGen &&
1879  FD->hasAttr<DLLImportAttr>())
1880  return false;
1881  }
1882  }
1883 
1884  // Allow address constant expressions to be past-the-end pointers. This is
1885  // an extension: the standard requires them to point to an object.
1886  if (!IsReferenceType)
1887  return true;
1888 
1889  // A reference constant expression must refer to an object.
1890  if (!Base) {
1891  // FIXME: diagnostic
1892  Info.CCEDiag(Loc);
1893  return true;
1894  }
1895 
1896  // Does this refer one past the end of some object?
1897  if (!Designator.Invalid && Designator.isOnePastTheEnd()) {
1898  const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
1899  Info.FFDiag(Loc, diag::note_constexpr_past_end, 1)
1900  << !Designator.Entries.empty() << !!VD << VD;
1901  NoteLValueLocation(Info, Base);
1902  }
1903 
1904  return true;
1905 }
1906 
1907 /// Member pointers are constant expressions unless they point to a
1908 /// non-virtual dllimport member function.
1909 static bool CheckMemberPointerConstantExpression(EvalInfo &Info,
1910  SourceLocation Loc,
1911  QualType Type,
1912  const APValue &Value,
1913  Expr::ConstExprUsage Usage) {
1914  const ValueDecl *Member = Value.getMemberPointerDecl();
1915  const auto *FD = dyn_cast_or_null<CXXMethodDecl>(Member);
1916  if (!FD)
1917  return true;
1918  return Usage == Expr::EvaluateForMangling || FD->isVirtual() ||
1919  !FD->hasAttr<DLLImportAttr>();
1920 }
1921 
1922 /// Check that this core constant expression is of literal type, and if not,
1923 /// produce an appropriate diagnostic.
1924 static bool CheckLiteralType(EvalInfo &Info, const Expr *E,
1925  const LValue *This = nullptr) {
1926  if (!E->isRValue() || E->getType()->isLiteralType(Info.Ctx))
1927  return true;
1928 
1929  // C++1y: A constant initializer for an object o [...] may also invoke
1930  // constexpr constructors for o and its subobjects even if those objects
1931  // are of non-literal class types.
1932  //
1933  // C++11 missed this detail for aggregates, so classes like this:
1934  // struct foo_t { union { int i; volatile int j; } u; };
1935  // are not (obviously) initializable like so:
1936  // __attribute__((__require_constant_initialization__))
1937  // static const foo_t x = {{0}};
1938  // because "i" is a subobject with non-literal initialization (due to the
1939  // volatile member of the union). See:
1940  // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1677
1941  // Therefore, we use the C++1y behavior.
1942  if (This && Info.EvaluatingDecl == This->getLValueBase())
1943  return true;
1944 
1945  // Prvalue constant expressions must be of literal types.
1946  if (Info.getLangOpts().CPlusPlus11)
1947  Info.FFDiag(E, diag::note_constexpr_nonliteral)
1948  << E->getType();
1949  else
1950  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
1951  return false;
1952 }
1953 
1954 /// Check that this core constant expression value is a valid value for a
1955 /// constant expression. If not, report an appropriate diagnostic. Does not
1956 /// check that the expression is of literal type.
1957 static bool
1958 CheckConstantExpression(EvalInfo &Info, SourceLocation DiagLoc, QualType Type,
1959  const APValue &Value,
1961  if (Value.isUninit()) {
1962  Info.FFDiag(DiagLoc, diag::note_constexpr_uninitialized)
1963  << true << Type;
1964  return false;
1965  }
1966 
1967  // We allow _Atomic(T) to be initialized from anything that T can be
1968  // initialized from.
1969  if (const AtomicType *AT = Type->getAs<AtomicType>())
1970  Type = AT->getValueType();
1971 
1972  // Core issue 1454: For a literal constant expression of array or class type,
1973  // each subobject of its value shall have been initialized by a constant
1974  // expression.
1975  if (Value.isArray()) {
1976  QualType EltTy = Type->castAsArrayTypeUnsafe()->getElementType();
1977  for (unsigned I = 0, N = Value.getArrayInitializedElts(); I != N; ++I) {
1978  if (!CheckConstantExpression(Info, DiagLoc, EltTy,
1979  Value.getArrayInitializedElt(I), Usage))
1980  return false;
1981  }
1982  if (!Value.hasArrayFiller())
1983  return true;
1984  return CheckConstantExpression(Info, DiagLoc, EltTy, Value.getArrayFiller(),
1985  Usage);
1986  }
1987  if (Value.isUnion() && Value.getUnionField()) {
1988  return CheckConstantExpression(Info, DiagLoc,
1989  Value.getUnionField()->getType(),
1990  Value.getUnionValue(), Usage);
1991  }
1992  if (Value.isStruct()) {
1993  RecordDecl *RD = Type->castAs<RecordType>()->getDecl();
1994  if (const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD)) {
1995  unsigned BaseIndex = 0;
1996  for (const CXXBaseSpecifier &BS : CD->bases()) {
1997  if (!CheckConstantExpression(Info, DiagLoc, BS.getType(),
1998  Value.getStructBase(BaseIndex), Usage))
1999  return false;
2000  ++BaseIndex;
2001  }
2002  }
2003  for (const auto *I : RD->fields()) {
2004  if (I->isUnnamedBitfield())
2005  continue;
2006 
2007  if (!CheckConstantExpression(Info, DiagLoc, I->getType(),
2008  Value.getStructField(I->getFieldIndex()),
2009  Usage))
2010  return false;
2011  }
2012  }
2013 
2014  if (Value.isLValue()) {
2015  LValue LVal;
2016  LVal.setFrom(Info.Ctx, Value);
2017  return CheckLValueConstantExpression(Info, DiagLoc, Type, LVal, Usage);
2018  }
2019 
2020  if (Value.isMemberPointer())
2021  return CheckMemberPointerConstantExpression(Info, DiagLoc, Type, Value, Usage);
2022 
2023  // Everything else is fine.
2024  return true;
2025 }
2026 
2027 static bool EvalPointerValueAsBool(const APValue &Value, bool &Result) {
2028  // A null base expression indicates a null pointer. These are always
2029  // evaluatable, and they are false unless the offset is zero.
2030  if (!Value.getLValueBase()) {
2031  Result = !Value.getLValueOffset().isZero();
2032  return true;
2033  }
2034 
2035  // We have a non-null base. These are generally known to be true, but if it's
2036  // a weak declaration it can be null at runtime.
2037  Result = true;
2038  const ValueDecl *Decl = Value.getLValueBase().dyn_cast<const ValueDecl*>();
2039  return !Decl || !Decl->isWeak();
2040 }
2041 
2042 static bool HandleConversionToBool(const APValue &Val, bool &Result) {
2043  switch (Val.getKind()) {
2045  return false;
2046  case APValue::Int:
2047  Result = Val.getInt().getBoolValue();
2048  return true;
2049  case APValue::FixedPoint:
2050  Result = Val.getFixedPoint().getBoolValue();
2051  return true;
2052  case APValue::Float:
2053  Result = !Val.getFloat().isZero();
2054  return true;
2055  case APValue::ComplexInt:
2056  Result = Val.getComplexIntReal().getBoolValue() ||
2057  Val.getComplexIntImag().getBoolValue();
2058  return true;
2059  case APValue::ComplexFloat:
2060  Result = !Val.getComplexFloatReal().isZero() ||
2061  !Val.getComplexFloatImag().isZero();
2062  return true;
2063  case APValue::LValue:
2064  return EvalPointerValueAsBool(Val, Result);
2066  Result = Val.getMemberPointerDecl();
2067  return true;
2068  case APValue::Vector:
2069  case APValue::Array:
2070  case APValue::Struct:
2071  case APValue::Union:
2073  return false;
2074  }
2075 
2076  llvm_unreachable("unknown APValue kind");
2077 }
2078 
2079 static bool EvaluateAsBooleanCondition(const Expr *E, bool &Result,
2080  EvalInfo &Info) {
2081  assert(E->isRValue() && "missing lvalue-to-rvalue conv in bool condition");
2082  APValue Val;
2083  if (!Evaluate(Val, Info, E))
2084  return false;
2085  return HandleConversionToBool(Val, Result);
2086 }
2087 
2088 template<typename T>
2089 static bool HandleOverflow(EvalInfo &Info, const Expr *E,
2090  const T &SrcValue, QualType DestType) {
2091  Info.CCEDiag(E, diag::note_constexpr_overflow)
2092  << SrcValue << DestType;
2093  return Info.noteUndefinedBehavior();
2094 }
2095 
2096 static bool HandleFloatToIntCast(EvalInfo &Info, const Expr *E,
2097  QualType SrcType, const APFloat &Value,
2098  QualType DestType, APSInt &Result) {
2099  unsigned DestWidth = Info.Ctx.getIntWidth(DestType);
2100  // Determine whether we are converting to unsigned or signed.
2101  bool DestSigned = DestType->isSignedIntegerOrEnumerationType();
2102 
2103  Result = APSInt(DestWidth, !DestSigned);
2104  bool ignored;
2105  if (Value.convertToInteger(Result, llvm::APFloat::rmTowardZero, &ignored)
2106  & APFloat::opInvalidOp)
2107  return HandleOverflow(Info, E, Value, DestType);
2108  return true;
2109 }
2110 
2111 static bool HandleFloatToFloatCast(EvalInfo &Info, const Expr *E,
2112  QualType SrcType, QualType DestType,
2113  APFloat &Result) {
2114  APFloat Value = Result;
2115  bool ignored;
2116  if (Result.convert(Info.Ctx.getFloatTypeSemantics(DestType),
2117  APFloat::rmNearestTiesToEven, &ignored)
2118  & APFloat::opOverflow)
2119  return HandleOverflow(Info, E, Value, DestType);
2120  return true;
2121 }
2122 
2123 static APSInt HandleIntToIntCast(EvalInfo &Info, const Expr *E,
2124  QualType DestType, QualType SrcType,
2125  const APSInt &Value) {
2126  unsigned DestWidth = Info.Ctx.getIntWidth(DestType);
2127  // Figure out if this is a truncate, extend or noop cast.
2128  // If the input is signed, do a sign extend, noop, or truncate.
2129  APSInt Result = Value.extOrTrunc(DestWidth);
2130  Result.setIsUnsigned(DestType->isUnsignedIntegerOrEnumerationType());
2131  if (DestType->isBooleanType())
2132  Result = Value.getBoolValue();
2133  return Result;
2134 }
2135 
2136 static bool HandleIntToFloatCast(EvalInfo &Info, const Expr *E,
2137  QualType SrcType, const APSInt &Value,
2138  QualType DestType, APFloat &Result) {
2139  Result = APFloat(Info.Ctx.getFloatTypeSemantics(DestType), 1);
2140  if (Result.convertFromAPInt(Value, Value.isSigned(),
2141  APFloat::rmNearestTiesToEven)
2142  & APFloat::opOverflow)
2143  return HandleOverflow(Info, E, Value, DestType);
2144  return true;
2145 }
2146 
2147 static bool truncateBitfieldValue(EvalInfo &Info, const Expr *E,
2148  APValue &Value, const FieldDecl *FD) {
2149  assert(FD->isBitField() && "truncateBitfieldValue on non-bitfield");
2150 
2151  if (!Value.isInt()) {
2152  // Trying to store a pointer-cast-to-integer into a bitfield.
2153  // FIXME: In this case, we should provide the diagnostic for casting
2154  // a pointer to an integer.
2155  assert(Value.isLValue() && "integral value neither int nor lvalue?");
2156  Info.FFDiag(E);
2157  return false;
2158  }
2159 
2160  APSInt &Int = Value.getInt();
2161  unsigned OldBitWidth = Int.getBitWidth();
2162  unsigned NewBitWidth = FD->getBitWidthValue(Info.Ctx);
2163  if (NewBitWidth < OldBitWidth)
2164  Int = Int.trunc(NewBitWidth).extend(OldBitWidth);
2165  return true;
2166 }
2167 
2168 static bool EvalAndBitcastToAPInt(EvalInfo &Info, const Expr *E,
2169  llvm::APInt &Res) {
2170  APValue SVal;
2171  if (!Evaluate(SVal, Info, E))
2172  return false;
2173  if (SVal.isInt()) {
2174  Res = SVal.getInt();
2175  return true;
2176  }
2177  if (SVal.isFloat()) {
2178  Res = SVal.getFloat().bitcastToAPInt();
2179  return true;
2180  }
2181  if (SVal.isVector()) {
2182  QualType VecTy = E->getType();
2183  unsigned VecSize = Info.Ctx.getTypeSize(VecTy);
2184  QualType EltTy = VecTy->castAs<VectorType>()->getElementType();
2185  unsigned EltSize = Info.Ctx.getTypeSize(EltTy);
2186  bool BigEndian = Info.Ctx.getTargetInfo().isBigEndian();
2187  Res = llvm::APInt::getNullValue(VecSize);
2188  for (unsigned i = 0; i < SVal.getVectorLength(); i++) {
2189  APValue &Elt = SVal.getVectorElt(i);
2190  llvm::APInt EltAsInt;
2191  if (Elt.isInt()) {
2192  EltAsInt = Elt.getInt();
2193  } else if (Elt.isFloat()) {
2194  EltAsInt = Elt.getFloat().bitcastToAPInt();
2195  } else {
2196  // Don't try to handle vectors of anything other than int or float
2197  // (not sure if it's possible to hit this case).
2198  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2199  return false;
2200  }
2201  unsigned BaseEltSize = EltAsInt.getBitWidth();
2202  if (BigEndian)
2203  Res |= EltAsInt.zextOrTrunc(VecSize).rotr(i*EltSize+BaseEltSize);
2204  else
2205  Res |= EltAsInt.zextOrTrunc(VecSize).rotl(i*EltSize);
2206  }
2207  return true;
2208  }
2209  // Give up if the input isn't an int, float, or vector. For example, we
2210  // reject "(v4i16)(intptr_t)&a".
2211  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2212  return false;
2213 }
2214 
2215 /// Perform the given integer operation, which is known to need at most BitWidth
2216 /// bits, and check for overflow in the original type (if that type was not an
2217 /// unsigned type).
2218 template<typename Operation>
2219 static bool CheckedIntArithmetic(EvalInfo &Info, const Expr *E,
2220  const APSInt &LHS, const APSInt &RHS,
2221  unsigned BitWidth, Operation Op,
2222  APSInt &Result) {
2223  if (LHS.isUnsigned()) {
2224  Result = Op(LHS, RHS);
2225  return true;
2226  }
2227 
2228  APSInt Value(Op(LHS.extend(BitWidth), RHS.extend(BitWidth)), false);
2229  Result = Value.trunc(LHS.getBitWidth());
2230  if (Result.extend(BitWidth) != Value) {
2231  if (Info.checkingForOverflow())
2232  Info.Ctx.getDiagnostics().Report(E->getExprLoc(),
2233  diag::warn_integer_constant_overflow)
2234  << Result.toString(10) << E->getType();
2235  else
2236  return HandleOverflow(Info, E, Value, E->getType());
2237  }
2238  return true;
2239 }
2240 
2241 /// Perform the given binary integer operation.
2242 static bool handleIntIntBinOp(EvalInfo &Info, const Expr *E, const APSInt &LHS,
2243  BinaryOperatorKind Opcode, APSInt RHS,
2244  APSInt &Result) {
2245  switch (Opcode) {
2246  default:
2247  Info.FFDiag(E);
2248  return false;
2249  case BO_Mul:
2250  return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() * 2,
2251  std::multiplies<APSInt>(), Result);
2252  case BO_Add:
2253  return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() + 1,
2254  std::plus<APSInt>(), Result);
2255  case BO_Sub:
2256  return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() + 1,
2257  std::minus<APSInt>(), Result);
2258  case BO_And: Result = LHS & RHS; return true;
2259  case BO_Xor: Result = LHS ^ RHS; return true;
2260  case BO_Or: Result = LHS | RHS; return true;
2261  case BO_Div:
2262  case BO_Rem:
2263  if (RHS == 0) {
2264  Info.FFDiag(E, diag::note_expr_divide_by_zero);
2265  return false;
2266  }
2267  Result = (Opcode == BO_Rem ? LHS % RHS : LHS / RHS);
2268  // Check for overflow case: INT_MIN / -1 or INT_MIN % -1. APSInt supports
2269  // this operation and gives the two's complement result.
2270  if (RHS.isNegative() && RHS.isAllOnesValue() &&
2271  LHS.isSigned() && LHS.isMinSignedValue())
2272  return HandleOverflow(Info, E, -LHS.extend(LHS.getBitWidth() + 1),
2273  E->getType());
2274  return true;
2275  case BO_Shl: {
2276  if (Info.getLangOpts().OpenCL)
2277  // OpenCL 6.3j: shift values are effectively % word size of LHS.
2278  RHS &= APSInt(llvm::APInt(RHS.getBitWidth(),
2279  static_cast<uint64_t>(LHS.getBitWidth() - 1)),
2280  RHS.isUnsigned());
2281  else if (RHS.isSigned() && RHS.isNegative()) {
2282  // During constant-folding, a negative shift is an opposite shift. Such
2283  // a shift is not a constant expression.
2284  Info.CCEDiag(E, diag::note_constexpr_negative_shift) << RHS;
2285  RHS = -RHS;
2286  goto shift_right;
2287  }
2288  shift_left:
2289  // C++11 [expr.shift]p1: Shift width must be less than the bit width of
2290  // the shifted type.
2291  unsigned SA = (unsigned) RHS.getLimitedValue(LHS.getBitWidth()-1);
2292  if (SA != RHS) {
2293  Info.CCEDiag(E, diag::note_constexpr_large_shift)
2294  << RHS << E->getType() << LHS.getBitWidth();
2295  } else if (LHS.isSigned()) {
2296  // C++11 [expr.shift]p2: A signed left shift must have a non-negative
2297  // operand, and must not overflow the corresponding unsigned type.
2298  if (LHS.isNegative())
2299  Info.CCEDiag(E, diag::note_constexpr_lshift_of_negative) << LHS;
2300  else if (LHS.countLeadingZeros() < SA)
2301  Info.CCEDiag(E, diag::note_constexpr_lshift_discards);
2302  }
2303  Result = LHS << SA;
2304  return true;
2305  }
2306  case BO_Shr: {
2307  if (Info.getLangOpts().OpenCL)
2308  // OpenCL 6.3j: shift values are effectively % word size of LHS.
2309  RHS &= APSInt(llvm::APInt(RHS.getBitWidth(),
2310  static_cast<uint64_t>(LHS.getBitWidth() - 1)),
2311  RHS.isUnsigned());
2312  else if (RHS.isSigned() && RHS.isNegative()) {
2313  // During constant-folding, a negative shift is an opposite shift. Such a
2314  // shift is not a constant expression.
2315  Info.CCEDiag(E, diag::note_constexpr_negative_shift) << RHS;
2316  RHS = -RHS;
2317  goto shift_left;
2318  }
2319  shift_right:
2320  // C++11 [expr.shift]p1: Shift width must be less than the bit width of the
2321  // shifted type.
2322  unsigned SA = (unsigned) RHS.getLimitedValue(LHS.getBitWidth()-1);
2323  if (SA != RHS)
2324  Info.CCEDiag(E, diag::note_constexpr_large_shift)
2325  << RHS << E->getType() << LHS.getBitWidth();
2326  Result = LHS >> SA;
2327  return true;
2328  }
2329 
2330  case BO_LT: Result = LHS < RHS; return true;
2331  case BO_GT: Result = LHS > RHS; return true;
2332  case BO_LE: Result = LHS <= RHS; return true;
2333  case BO_GE: Result = LHS >= RHS; return true;
2334  case BO_EQ: Result = LHS == RHS; return true;
2335  case BO_NE: Result = LHS != RHS; return true;
2336  case BO_Cmp:
2337  llvm_unreachable("BO_Cmp should be handled elsewhere");
2338  }
2339 }
2340 
2341 /// Perform the given binary floating-point operation, in-place, on LHS.
2342 static bool handleFloatFloatBinOp(EvalInfo &Info, const Expr *E,
2343  APFloat &LHS, BinaryOperatorKind Opcode,
2344  const APFloat &RHS) {
2345  switch (Opcode) {
2346  default:
2347  Info.FFDiag(E);
2348  return false;
2349  case BO_Mul:
2350  LHS.multiply(RHS, APFloat::rmNearestTiesToEven);
2351  break;
2352  case BO_Add:
2353  LHS.add(RHS, APFloat::rmNearestTiesToEven);
2354  break;
2355  case BO_Sub:
2356  LHS.subtract(RHS, APFloat::rmNearestTiesToEven);
2357  break;
2358  case BO_Div:
2359  LHS.divide(RHS, APFloat::rmNearestTiesToEven);
2360  break;
2361  }
2362 
2363  if (LHS.isInfinity() || LHS.isNaN()) {
2364  Info.CCEDiag(E, diag::note_constexpr_float_arithmetic) << LHS.isNaN();
2365  return Info.noteUndefinedBehavior();
2366  }
2367  return true;
2368 }
2369 
2370 /// Cast an lvalue referring to a base subobject to a derived class, by
2371 /// truncating the lvalue's path to the given length.
2372 static bool CastToDerivedClass(EvalInfo &Info, const Expr *E, LValue &Result,
2373  const RecordDecl *TruncatedType,
2374  unsigned TruncatedElements) {
2375  SubobjectDesignator &D = Result.Designator;
2376 
2377  // Check we actually point to a derived class object.
2378  if (TruncatedElements == D.Entries.size())
2379  return true;
2380  assert(TruncatedElements >= D.MostDerivedPathLength &&
2381  "not casting to a derived class");
2382  if (!Result.checkSubobject(Info, E, CSK_Derived))
2383  return false;
2384 
2385  // Truncate the path to the subobject, and remove any derived-to-base offsets.
2386  const RecordDecl *RD = TruncatedType;
2387  for (unsigned I = TruncatedElements, N = D.Entries.size(); I != N; ++I) {
2388  if (RD->isInvalidDecl()) return false;
2389  const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
2390  const CXXRecordDecl *Base = getAsBaseClass(D.Entries[I]);
2391  if (isVirtualBaseClass(D.Entries[I]))
2392  Result.Offset -= Layout.getVBaseClassOffset(Base);
2393  else
2394  Result.Offset -= Layout.getBaseClassOffset(Base);
2395  RD = Base;
2396  }
2397  D.Entries.resize(TruncatedElements);
2398  return true;
2399 }
2400 
2401 static bool HandleLValueDirectBase(EvalInfo &Info, const Expr *E, LValue &Obj,
2402  const CXXRecordDecl *Derived,
2403  const CXXRecordDecl *Base,
2404  const ASTRecordLayout *RL = nullptr) {
2405  if (!RL) {
2406  if (Derived->isInvalidDecl()) return false;
2407  RL = &Info.Ctx.getASTRecordLayout(Derived);
2408  }
2409 
2410  Obj.getLValueOffset() += RL->getBaseClassOffset(Base);
2411  Obj.addDecl(Info, E, Base, /*Virtual*/ false);
2412  return true;
2413 }
2414 
2415 static bool HandleLValueBase(EvalInfo &Info, const Expr *E, LValue &Obj,
2416  const CXXRecordDecl *DerivedDecl,
2417  const CXXBaseSpecifier *Base) {
2418  const CXXRecordDecl *BaseDecl = Base->getType()->getAsCXXRecordDecl();
2419 
2420  if (!Base->isVirtual())
2421  return HandleLValueDirectBase(Info, E, Obj, DerivedDecl, BaseDecl);
2422 
2423  SubobjectDesignator &D = Obj.Designator;
2424  if (D.Invalid)
2425  return false;
2426 
2427  // Extract most-derived object and corresponding type.
2428  DerivedDecl = D.MostDerivedType->getAsCXXRecordDecl();
2429  if (!CastToDerivedClass(Info, E, Obj, DerivedDecl, D.MostDerivedPathLength))
2430  return false;
2431 
2432  // Find the virtual base class.
2433  if (DerivedDecl->isInvalidDecl()) return false;
2434  const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(DerivedDecl);
2435  Obj.getLValueOffset() += Layout.getVBaseClassOffset(BaseDecl);
2436  Obj.addDecl(Info, E, BaseDecl, /*Virtual*/ true);
2437  return true;
2438 }
2439 
2440 static bool HandleLValueBasePath(EvalInfo &Info, const CastExpr *E,
2441  QualType Type, LValue &Result) {
2442  for (CastExpr::path_const_iterator PathI = E->path_begin(),
2443  PathE = E->path_end();
2444  PathI != PathE; ++PathI) {
2445  if (!HandleLValueBase(Info, E, Result, Type->getAsCXXRecordDecl(),
2446  *PathI))
2447  return false;
2448  Type = (*PathI)->getType();
2449  }
2450  return true;
2451 }
2452 
2453 /// Update LVal to refer to the given field, which must be a member of the type
2454 /// currently described by LVal.
2455 static bool HandleLValueMember(EvalInfo &Info, const Expr *E, LValue &LVal,
2456  const FieldDecl *FD,
2457  const ASTRecordLayout *RL = nullptr) {
2458  if (!RL) {
2459  if (FD->getParent()->isInvalidDecl()) return false;
2460  RL = &Info.Ctx.getASTRecordLayout(FD->getParent());
2461  }
2462 
2463  unsigned I = FD->getFieldIndex();
2464  LVal.adjustOffset(Info.Ctx.toCharUnitsFromBits(RL->getFieldOffset(I)));
2465  LVal.addDecl(Info, E, FD);
2466  return true;
2467 }
2468 
2469 /// Update LVal to refer to the given indirect field.
2470 static bool HandleLValueIndirectMember(EvalInfo &Info, const Expr *E,
2471  LValue &LVal,
2472  const IndirectFieldDecl *IFD) {
2473  for (const auto *C : IFD->chain())
2474  if (!HandleLValueMember(Info, E, LVal, cast<FieldDecl>(C)))
2475  return false;
2476  return true;
2477 }
2478 
2479 /// Get the size of the given type in char units.
2480 static bool HandleSizeof(EvalInfo &Info, SourceLocation Loc,
2481  QualType Type, CharUnits &Size) {
2482  // sizeof(void), __alignof__(void), sizeof(function) = 1 as a gcc
2483  // extension.
2484  if (Type->isVoidType() || Type->isFunctionType()) {
2485  Size = CharUnits::One();
2486  return true;
2487  }
2488 
2489  if (Type->isDependentType()) {
2490  Info.FFDiag(Loc);
2491  return false;
2492  }
2493 
2494  if (!Type->isConstantSizeType()) {
2495  // sizeof(vla) is not a constantexpr: C99 6.5.3.4p2.
2496  // FIXME: Better diagnostic.
2497  Info.FFDiag(Loc);
2498  return false;
2499  }
2500 
2501  Size = Info.Ctx.getTypeSizeInChars(Type);
2502  return true;
2503 }
2504 
2505 /// Update a pointer value to model pointer arithmetic.
2506 /// \param Info - Information about the ongoing evaluation.
2507 /// \param E - The expression being evaluated, for diagnostic purposes.
2508 /// \param LVal - The pointer value to be updated.
2509 /// \param EltTy - The pointee type represented by LVal.
2510 /// \param Adjustment - The adjustment, in objects of type EltTy, to add.
2511 static bool HandleLValueArrayAdjustment(EvalInfo &Info, const Expr *E,
2512  LValue &LVal, QualType EltTy,
2513  APSInt Adjustment) {
2514  CharUnits SizeOfPointee;
2515  if (!HandleSizeof(Info, E->getExprLoc(), EltTy, SizeOfPointee))
2516  return false;
2517 
2518  LVal.adjustOffsetAndIndex(Info, E, Adjustment, SizeOfPointee);
2519  return true;
2520 }
2521 
2522 static bool HandleLValueArrayAdjustment(EvalInfo &Info, const Expr *E,
2523  LValue &LVal, QualType EltTy,
2524  int64_t Adjustment) {
2525  return HandleLValueArrayAdjustment(Info, E, LVal, EltTy,
2526  APSInt::get(Adjustment));
2527 }
2528 
2529 /// Update an lvalue to refer to a component of a complex number.
2530 /// \param Info - Information about the ongoing evaluation.
2531 /// \param LVal - The lvalue to be updated.
2532 /// \param EltTy - The complex number's component type.
2533 /// \param Imag - False for the real component, true for the imaginary.
2534 static bool HandleLValueComplexElement(EvalInfo &Info, const Expr *E,
2535  LValue &LVal, QualType EltTy,
2536  bool Imag) {
2537  if (Imag) {
2538  CharUnits SizeOfComponent;
2539  if (!HandleSizeof(Info, E->getExprLoc(), EltTy, SizeOfComponent))
2540  return false;
2541  LVal.Offset += SizeOfComponent;
2542  }
2543  LVal.addComplex(Info, E, EltTy, Imag);
2544  return true;
2545 }
2546 
2547 static bool handleLValueToRValueConversion(EvalInfo &Info, const Expr *Conv,
2548  QualType Type, const LValue &LVal,
2549  APValue &RVal);
2550 
2551 /// Try to evaluate the initializer for a variable declaration.
2552 ///
2553 /// \param Info Information about the ongoing evaluation.
2554 /// \param E An expression to be used when printing diagnostics.
2555 /// \param VD The variable whose initializer should be obtained.
2556 /// \param Frame The frame in which the variable was created. Must be null
2557 /// if this variable is not local to the evaluation.
2558 /// \param Result Filled in with a pointer to the value of the variable.
2559 static bool evaluateVarDeclInit(EvalInfo &Info, const Expr *E,
2560  const VarDecl *VD, CallStackFrame *Frame,
2561  APValue *&Result, const LValue *LVal) {
2562 
2563  // If this is a parameter to an active constexpr function call, perform
2564  // argument substitution.
2565  if (const ParmVarDecl *PVD = dyn_cast<ParmVarDecl>(VD)) {
2566  // Assume arguments of a potential constant expression are unknown
2567  // constant expressions.
2568  if (Info.checkingPotentialConstantExpression())
2569  return false;
2570  if (!Frame || !Frame->Arguments) {
2571  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2572  return false;
2573  }
2574  Result = &Frame->Arguments[PVD->getFunctionScopeIndex()];
2575  return true;
2576  }
2577 
2578  // If this is a local variable, dig out its value.
2579  if (Frame) {
2580  Result = LVal ? Frame->getTemporary(VD, LVal->getLValueVersion())
2581  : Frame->getCurrentTemporary(VD);
2582  if (!Result) {
2583  // Assume variables referenced within a lambda's call operator that were
2584  // not declared within the call operator are captures and during checking
2585  // of a potential constant expression, assume they are unknown constant
2586  // expressions.
2587  assert(isLambdaCallOperator(Frame->Callee) &&
2588  (VD->getDeclContext() != Frame->Callee || VD->isInitCapture()) &&
2589  "missing value for local variable");
2590  if (Info.checkingPotentialConstantExpression())
2591  return false;
2592  // FIXME: implement capture evaluation during constant expr evaluation.
2593  Info.FFDiag(E->getBeginLoc(),
2594  diag::note_unimplemented_constexpr_lambda_feature_ast)
2595  << "captures not currently allowed";
2596  return false;
2597  }
2598  return true;
2599  }
2600 
2601  // Dig out the initializer, and use the declaration which it's attached to.
2602  const Expr *Init = VD->getAnyInitializer(VD);
2603  if (!Init || Init->isValueDependent()) {
2604  // If we're checking a potential constant expression, the variable could be
2605  // initialized later.
2606  if (!Info.checkingPotentialConstantExpression())
2607  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2608  return false;
2609  }
2610 
2611  // If we're currently evaluating the initializer of this declaration, use that
2612  // in-flight value.
2613  if (Info.EvaluatingDecl.dyn_cast<const ValueDecl*>() == VD) {
2614  Result = Info.EvaluatingDeclValue;
2615  return true;
2616  }
2617 
2618  // Never evaluate the initializer of a weak variable. We can't be sure that
2619  // this is the definition which will be used.
2620  if (VD->isWeak()) {
2621  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2622  return false;
2623  }
2624 
2625  // Check that we can fold the initializer. In C++, we will have already done
2626  // this in the cases where it matters for conformance.
2628  if (!VD->evaluateValue(Notes)) {
2629  Info.FFDiag(E, diag::note_constexpr_var_init_non_constant,
2630  Notes.size() + 1) << VD;
2631  Info.Note(VD->getLocation(), diag::note_declared_at);
2632  Info.addNotes(Notes);
2633  return false;
2634  } else if (!VD->checkInitIsICE()) {
2635  Info.CCEDiag(E, diag::note_constexpr_var_init_non_constant,
2636  Notes.size() + 1) << VD;
2637  Info.Note(VD->getLocation(), diag::note_declared_at);
2638  Info.addNotes(Notes);
2639  }
2640 
2641  Result = VD->getEvaluatedValue();
2642  return true;
2643 }
2644 
2646  Qualifiers Quals = T.getQualifiers();
2647  return Quals.hasConst() && !Quals.hasVolatile();
2648 }
2649 
2650 /// Get the base index of the given base class within an APValue representing
2651 /// the given derived class.
2652 static unsigned getBaseIndex(const CXXRecordDecl *Derived,
2653  const CXXRecordDecl *Base) {
2654  Base = Base->getCanonicalDecl();
2655  unsigned Index = 0;
2657  E = Derived->bases_end(); I != E; ++I, ++Index) {
2658  if (I->getType()->getAsCXXRecordDecl()->getCanonicalDecl() == Base)
2659  return Index;
2660  }
2661 
2662  llvm_unreachable("base class missing from derived class's bases list");
2663 }
2664 
2665 /// Extract the value of a character from a string literal.
2666 static APSInt extractStringLiteralCharacter(EvalInfo &Info, const Expr *Lit,
2667  uint64_t Index) {
2668  // FIXME: Support MakeStringConstant
2669  if (const auto *ObjCEnc = dyn_cast<ObjCEncodeExpr>(Lit)) {
2670  std::string Str;
2671  Info.Ctx.getObjCEncodingForType(ObjCEnc->getEncodedType(), Str);
2672  assert(Index <= Str.size() && "Index too large");
2673  return APSInt::getUnsigned(Str.c_str()[Index]);
2674  }
2675 
2676  if (auto PE = dyn_cast<PredefinedExpr>(Lit))
2677  Lit = PE->getFunctionName();
2678  const StringLiteral *S = cast<StringLiteral>(Lit);
2679  const ConstantArrayType *CAT =
2680  Info.Ctx.getAsConstantArrayType(S->getType());
2681  assert(CAT && "string literal isn't an array");
2682  QualType CharType = CAT->getElementType();
2683  assert(CharType->isIntegerType() && "unexpected character type");
2684 
2685  APSInt Value(S->getCharByteWidth() * Info.Ctx.getCharWidth(),
2686  CharType->isUnsignedIntegerType());
2687  if (Index < S->getLength())
2688  Value = S->getCodeUnit(Index);
2689  return Value;
2690 }
2691 
2692 // Expand a string literal into an array of characters.
2693 //
2694 // FIXME: This is inefficient; we should probably introduce something similar
2695 // to the LLVM ConstantDataArray to make this cheaper.
2696 static void expandStringLiteral(EvalInfo &Info, const StringLiteral *S,
2697  APValue &Result) {
2698  const ConstantArrayType *CAT =
2699  Info.Ctx.getAsConstantArrayType(S->getType());
2700  assert(CAT && "string literal isn't an array");
2701  QualType CharType = CAT->getElementType();
2702  assert(CharType->isIntegerType() && "unexpected character type");
2703 
2704  unsigned Elts = CAT->getSize().getZExtValue();
2705  Result = APValue(APValue::UninitArray(),
2706  std::min(S->getLength(), Elts), Elts);
2707  APSInt Value(S->getCharByteWidth() * Info.Ctx.getCharWidth(),
2708  CharType->isUnsignedIntegerType());
2709  if (Result.hasArrayFiller())
2710  Result.getArrayFiller() = APValue(Value);
2711  for (unsigned I = 0, N = Result.getArrayInitializedElts(); I != N; ++I) {
2712  Value = S->getCodeUnit(I);
2713  Result.getArrayInitializedElt(I) = APValue(Value);
2714  }
2715 }
2716 
2717 // Expand an array so that it has more than Index filled elements.
2718 static void expandArray(APValue &Array, unsigned Index) {
2719  unsigned Size = Array.getArraySize();
2720  assert(Index < Size);
2721 
2722  // Always at least double the number of elements for which we store a value.
2723  unsigned OldElts = Array.getArrayInitializedElts();
2724  unsigned NewElts = std::max(Index+1, OldElts * 2);
2725  NewElts = std::min(Size, std::max(NewElts, 8u));
2726 
2727  // Copy the data across.
2728  APValue NewValue(APValue::UninitArray(), NewElts, Size);
2729  for (unsigned I = 0; I != OldElts; ++I)
2730  NewValue.getArrayInitializedElt(I).swap(Array.getArrayInitializedElt(I));
2731  for (unsigned I = OldElts; I != NewElts; ++I)
2732  NewValue.getArrayInitializedElt(I) = Array.getArrayFiller();
2733  if (NewValue.hasArrayFiller())
2734  NewValue.getArrayFiller() = Array.getArrayFiller();
2735  Array.swap(NewValue);
2736 }
2737 
2738 /// Determine whether a type would actually be read by an lvalue-to-rvalue
2739 /// conversion. If it's of class type, we may assume that the copy operation
2740 /// is trivial. Note that this is never true for a union type with fields
2741 /// (because the copy always "reads" the active member) and always true for
2742 /// a non-class type.
2745  if (!RD || (RD->isUnion() && !RD->field_empty()))
2746  return true;
2747  if (RD->isEmpty())
2748  return false;
2749 
2750  for (auto *Field : RD->fields())
2751  if (isReadByLvalueToRvalueConversion(Field->getType()))
2752  return true;
2753 
2754  for (auto &BaseSpec : RD->bases())
2755  if (isReadByLvalueToRvalueConversion(BaseSpec.getType()))
2756  return true;
2757 
2758  return false;
2759 }
2760 
2761 /// Diagnose an attempt to read from any unreadable field within the specified
2762 /// type, which might be a class type.
2763 static bool diagnoseUnreadableFields(EvalInfo &Info, const Expr *E,
2764  QualType T) {
2766  if (!RD)
2767  return false;
2768 
2769  if (!RD->hasMutableFields())
2770  return false;
2771 
2772  for (auto *Field : RD->fields()) {
2773  // If we're actually going to read this field in some way, then it can't
2774  // be mutable. If we're in a union, then assigning to a mutable field
2775  // (even an empty one) can change the active member, so that's not OK.
2776  // FIXME: Add core issue number for the union case.
2777  if (Field->isMutable() &&
2778  (RD->isUnion() || isReadByLvalueToRvalueConversion(Field->getType()))) {
2779  Info.FFDiag(E, diag::note_constexpr_ltor_mutable, 1) << Field;
2780  Info.Note(Field->getLocation(), diag::note_declared_at);
2781  return true;
2782  }
2783 
2784  if (diagnoseUnreadableFields(Info, E, Field->getType()))
2785  return true;
2786  }
2787 
2788  for (auto &BaseSpec : RD->bases())
2789  if (diagnoseUnreadableFields(Info, E, BaseSpec.getType()))
2790  return true;
2791 
2792  // All mutable fields were empty, and thus not actually read.
2793  return false;
2794 }
2795 
2796 namespace {
2797 /// A handle to a complete object (an object that is not a subobject of
2798 /// another object).
2799 struct CompleteObject {
2800  /// The value of the complete object.
2801  APValue *Value;
2802  /// The type of the complete object.
2803  QualType Type;
2804  bool LifetimeStartedInEvaluation;
2805 
2806  CompleteObject() : Value(nullptr) {}
2807  CompleteObject(APValue *Value, QualType Type,
2808  bool LifetimeStartedInEvaluation)
2809  : Value(Value), Type(Type),
2810  LifetimeStartedInEvaluation(LifetimeStartedInEvaluation) {
2811  assert(Value && "missing value for complete object");
2812  }
2813 
2814  explicit operator bool() const { return Value; }
2815 };
2816 } // end anonymous namespace
2817 
2818 /// Find the designated sub-object of an rvalue.
2819 template<typename SubobjectHandler>
2820 typename SubobjectHandler::result_type
2821 findSubobject(EvalInfo &Info, const Expr *E, const CompleteObject &Obj,
2822  const SubobjectDesignator &Sub, SubobjectHandler &handler) {
2823  if (Sub.Invalid)
2824  // A diagnostic will have already been produced.
2825  return handler.failed();
2826  if (Sub.isOnePastTheEnd() || Sub.isMostDerivedAnUnsizedArray()) {
2827  if (Info.getLangOpts().CPlusPlus11)
2828  Info.FFDiag(E, Sub.isOnePastTheEnd()
2829  ? diag::note_constexpr_access_past_end
2830  : diag::note_constexpr_access_unsized_array)
2831  << handler.AccessKind;
2832  else
2833  Info.FFDiag(E);
2834  return handler.failed();
2835  }
2836 
2837  APValue *O = Obj.Value;
2838  QualType ObjType = Obj.Type;
2839  const FieldDecl *LastField = nullptr;
2840  const bool MayReadMutableMembers =
2841  Obj.LifetimeStartedInEvaluation && Info.getLangOpts().CPlusPlus14;
2842 
2843  // Walk the designator's path to find the subobject.
2844  for (unsigned I = 0, N = Sub.Entries.size(); /**/; ++I) {
2845  if (O->isUninit()) {
2846  if (!Info.checkingPotentialConstantExpression())
2847  Info.FFDiag(E, diag::note_constexpr_access_uninit) << handler.AccessKind;
2848  return handler.failed();
2849  }
2850 
2851  if (I == N) {
2852  // If we are reading an object of class type, there may still be more
2853  // things we need to check: if there are any mutable subobjects, we
2854  // cannot perform this read. (This only happens when performing a trivial
2855  // copy or assignment.)
2856  if (ObjType->isRecordType() && handler.AccessKind == AK_Read &&
2857  !MayReadMutableMembers && diagnoseUnreadableFields(Info, E, ObjType))
2858  return handler.failed();
2859 
2860  if (!handler.found(*O, ObjType))
2861  return false;
2862 
2863  // If we modified a bit-field, truncate it to the right width.
2864  if (handler.AccessKind != AK_Read &&
2865  LastField && LastField->isBitField() &&
2866  !truncateBitfieldValue(Info, E, *O, LastField))
2867  return false;
2868 
2869  return true;
2870  }
2871 
2872  LastField = nullptr;
2873  if (ObjType->isArrayType()) {
2874  // Next subobject is an array element.
2875  const ConstantArrayType *CAT = Info.Ctx.getAsConstantArrayType(ObjType);
2876  assert(CAT && "vla in literal type?");
2877  uint64_t Index = Sub.Entries[I].ArrayIndex;
2878  if (CAT->getSize().ule(Index)) {
2879  // Note, it should not be possible to form a pointer with a valid
2880  // designator which points more than one past the end of the array.
2881  if (Info.getLangOpts().CPlusPlus11)
2882  Info.FFDiag(E, diag::note_constexpr_access_past_end)
2883  << handler.AccessKind;
2884  else
2885  Info.FFDiag(E);
2886  return handler.failed();
2887  }
2888 
2889  ObjType = CAT->getElementType();
2890 
2891  if (O->getArrayInitializedElts() > Index)
2892  O = &O->getArrayInitializedElt(Index);
2893  else if (handler.AccessKind != AK_Read) {
2894  expandArray(*O, Index);
2895  O = &O->getArrayInitializedElt(Index);
2896  } else
2897  O = &O->getArrayFiller();
2898  } else if (ObjType->isAnyComplexType()) {
2899  // Next subobject is a complex number.
2900  uint64_t Index = Sub.Entries[I].ArrayIndex;
2901  if (Index > 1) {
2902  if (Info.getLangOpts().CPlusPlus11)
2903  Info.FFDiag(E, diag::note_constexpr_access_past_end)
2904  << handler.AccessKind;
2905  else
2906  Info.FFDiag(E);
2907  return handler.failed();
2908  }
2909 
2910  bool WasConstQualified = ObjType.isConstQualified();
2911  ObjType = ObjType->castAs<ComplexType>()->getElementType();
2912  if (WasConstQualified)
2913  ObjType.addConst();
2914 
2915  assert(I == N - 1 && "extracting subobject of scalar?");
2916  if (O->isComplexInt()) {
2917  return handler.found(Index ? O->getComplexIntImag()
2918  : O->getComplexIntReal(), ObjType);
2919  } else {
2920  assert(O->isComplexFloat());
2921  return handler.found(Index ? O->getComplexFloatImag()
2922  : O->getComplexFloatReal(), ObjType);
2923  }
2924  } else if (const FieldDecl *Field = getAsField(Sub.Entries[I])) {
2925  // In C++14 onwards, it is permitted to read a mutable member whose
2926  // lifetime began within the evaluation.
2927  // FIXME: Should we also allow this in C++11?
2928  if (Field->isMutable() && handler.AccessKind == AK_Read &&
2929  !MayReadMutableMembers) {
2930  Info.FFDiag(E, diag::note_constexpr_ltor_mutable, 1)
2931  << Field;
2932  Info.Note(Field->getLocation(), diag::note_declared_at);
2933  return handler.failed();
2934  }
2935 
2936  // Next subobject is a class, struct or union field.
2937  RecordDecl *RD = ObjType->castAs<RecordType>()->getDecl();
2938  if (RD->isUnion()) {
2939  const FieldDecl *UnionField = O->getUnionField();
2940  if (!UnionField ||
2941  UnionField->getCanonicalDecl() != Field->getCanonicalDecl()) {
2942  Info.FFDiag(E, diag::note_constexpr_access_inactive_union_member)
2943  << handler.AccessKind << Field << !UnionField << UnionField;
2944  return handler.failed();
2945  }
2946  O = &O->getUnionValue();
2947  } else
2948  O = &O->getStructField(Field->getFieldIndex());
2949 
2950  bool WasConstQualified = ObjType.isConstQualified();
2951  ObjType = Field->getType();
2952  if (WasConstQualified && !Field->isMutable())
2953  ObjType.addConst();
2954 
2955  if (ObjType.isVolatileQualified()) {
2956  if (Info.getLangOpts().CPlusPlus) {
2957  // FIXME: Include a description of the path to the volatile subobject.
2958  Info.FFDiag(E, diag::note_constexpr_access_volatile_obj, 1)
2959  << handler.AccessKind << 2 << Field;
2960  Info.Note(Field->getLocation(), diag::note_declared_at);
2961  } else {
2962  Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
2963  }
2964  return handler.failed();
2965  }
2966 
2967  LastField = Field;
2968  } else {
2969  // Next subobject is a base class.
2970  const CXXRecordDecl *Derived = ObjType->getAsCXXRecordDecl();
2971  const CXXRecordDecl *Base = getAsBaseClass(Sub.Entries[I]);
2972  O = &O->getStructBase(getBaseIndex(Derived, Base));
2973 
2974  bool WasConstQualified = ObjType.isConstQualified();
2975  ObjType = Info.Ctx.getRecordType(Base);
2976  if (WasConstQualified)
2977  ObjType.addConst();
2978  }
2979  }
2980 }
2981 
2982 namespace {
2983 struct ExtractSubobjectHandler {
2984  EvalInfo &Info;
2985  APValue &Result;
2986 
2987  static const AccessKinds AccessKind = AK_Read;
2988 
2989  typedef bool result_type;
2990  bool failed() { return false; }
2991  bool found(APValue &Subobj, QualType SubobjType) {
2992  Result = Subobj;
2993  return true;
2994  }
2995  bool found(APSInt &Value, QualType SubobjType) {
2996  Result = APValue(Value);
2997  return true;
2998  }
2999  bool found(APFloat &Value, QualType SubobjType) {
3000  Result = APValue(Value);
3001  return true;
3002  }
3003 };
3004 } // end anonymous namespace
3005 
3007 
3008 /// Extract the designated sub-object of an rvalue.
3009 static bool extractSubobject(EvalInfo &Info, const Expr *E,
3010  const CompleteObject &Obj,
3011  const SubobjectDesignator &Sub,
3012  APValue &Result) {
3013  ExtractSubobjectHandler Handler = { Info, Result };
3014  return findSubobject(Info, E, Obj, Sub, Handler);
3015 }
3016 
3017 namespace {
3018 struct ModifySubobjectHandler {
3019  EvalInfo &Info;
3020  APValue &NewVal;
3021  const Expr *E;
3022 
3023  typedef bool result_type;
3024  static const AccessKinds AccessKind = AK_Assign;
3025 
3026  bool checkConst(QualType QT) {
3027  // Assigning to a const object has undefined behavior.
3028  if (QT.isConstQualified()) {
3029  Info.FFDiag(E, diag::note_constexpr_modify_const_type) << QT;
3030  return false;
3031  }
3032  return true;
3033  }
3034 
3035  bool failed() { return false; }
3036  bool found(APValue &Subobj, QualType SubobjType) {
3037  if (!checkConst(SubobjType))
3038  return false;
3039  // We've been given ownership of NewVal, so just swap it in.
3040  Subobj.swap(NewVal);
3041  return true;
3042  }
3043  bool found(APSInt &Value, QualType SubobjType) {
3044  if (!checkConst(SubobjType))
3045  return false;
3046  if (!NewVal.isInt()) {
3047  // Maybe trying to write a cast pointer value into a complex?
3048  Info.FFDiag(E);
3049  return false;
3050  }
3051  Value = NewVal.getInt();
3052  return true;
3053  }
3054  bool found(APFloat &Value, QualType SubobjType) {
3055  if (!checkConst(SubobjType))
3056  return false;
3057  Value = NewVal.getFloat();
3058  return true;
3059  }
3060 };
3061 } // end anonymous namespace
3062 
3064 
3065 /// Update the designated sub-object of an rvalue to the given value.
3066 static bool modifySubobject(EvalInfo &Info, const Expr *E,
3067  const CompleteObject &Obj,
3068  const SubobjectDesignator &Sub,
3069  APValue &NewVal) {
3070  ModifySubobjectHandler Handler = { Info, NewVal, E };
3071  return findSubobject(Info, E, Obj, Sub, Handler);
3072 }
3073 
3074 /// Find the position where two subobject designators diverge, or equivalently
3075 /// the length of the common initial subsequence.
3076 static unsigned FindDesignatorMismatch(QualType ObjType,
3077  const SubobjectDesignator &A,
3078  const SubobjectDesignator &B,
3079  bool &WasArrayIndex) {
3080  unsigned I = 0, N = std::min(A.Entries.size(), B.Entries.size());
3081  for (/**/; I != N; ++I) {
3082  if (!ObjType.isNull() &&
3083  (ObjType->isArrayType() || ObjType->isAnyComplexType())) {
3084  // Next subobject is an array element.
3085  if (A.Entries[I].ArrayIndex != B.Entries[I].ArrayIndex) {
3086  WasArrayIndex = true;
3087  return I;
3088  }
3089  if (ObjType->isAnyComplexType())
3090  ObjType = ObjType->castAs<ComplexType>()->getElementType();
3091  else
3092  ObjType = ObjType->castAsArrayTypeUnsafe()->getElementType();
3093  } else {
3094  if (A.Entries[I].BaseOrMember != B.Entries[I].BaseOrMember) {
3095  WasArrayIndex = false;
3096  return I;
3097  }
3098  if (const FieldDecl *FD = getAsField(A.Entries[I]))
3099  // Next subobject is a field.
3100  ObjType = FD->getType();
3101  else
3102  // Next subobject is a base class.
3103  ObjType = QualType();
3104  }
3105  }
3106  WasArrayIndex = false;
3107  return I;
3108 }
3109 
3110 /// Determine whether the given subobject designators refer to elements of the
3111 /// same array object.
3112 static bool AreElementsOfSameArray(QualType ObjType,
3113  const SubobjectDesignator &A,
3114  const SubobjectDesignator &B) {
3115  if (A.Entries.size() != B.Entries.size())
3116  return false;
3117 
3118  bool IsArray = A.MostDerivedIsArrayElement;
3119  if (IsArray && A.MostDerivedPathLength != A.Entries.size())
3120  // A is a subobject of the array element.
3121  return false;
3122 
3123  // If A (and B) designates an array element, the last entry will be the array
3124  // index. That doesn't have to match. Otherwise, we're in the 'implicit array
3125  // of length 1' case, and the entire path must match.
3126  bool WasArrayIndex;
3127  unsigned CommonLength = FindDesignatorMismatch(ObjType, A, B, WasArrayIndex);
3128  return CommonLength >= A.Entries.size() - IsArray;
3129 }
3130 
3131 /// Find the complete object to which an LValue refers.
3132 static CompleteObject findCompleteObject(EvalInfo &Info, const Expr *E,
3133  AccessKinds AK, const LValue &LVal,
3134  QualType LValType) {
3135  if (!LVal.Base) {
3136  Info.FFDiag(E, diag::note_constexpr_access_null) << AK;
3137  return CompleteObject();
3138  }
3139 
3140  CallStackFrame *Frame = nullptr;
3141  if (LVal.getLValueCallIndex()) {
3142  Frame = Info.getCallFrame(LVal.getLValueCallIndex());
3143  if (!Frame) {
3144  Info.FFDiag(E, diag::note_constexpr_lifetime_ended, 1)
3145  << AK << LVal.Base.is<const ValueDecl*>();
3146  NoteLValueLocation(Info, LVal.Base);
3147  return CompleteObject();
3148  }
3149  }
3150 
3151  // C++11 DR1311: An lvalue-to-rvalue conversion on a volatile-qualified type
3152  // is not a constant expression (even if the object is non-volatile). We also
3153  // apply this rule to C++98, in order to conform to the expected 'volatile'
3154  // semantics.
3155  if (LValType.isVolatileQualified()) {
3156  if (Info.getLangOpts().CPlusPlus)
3157  Info.FFDiag(E, diag::note_constexpr_access_volatile_type)
3158  << AK << LValType;
3159  else
3160  Info.FFDiag(E);
3161  return CompleteObject();
3162  }
3163 
3164  // Compute value storage location and type of base object.
3165  APValue *BaseVal = nullptr;
3166  QualType BaseType = getType(LVal.Base);
3167  bool LifetimeStartedInEvaluation = Frame;
3168 
3169  if (const ValueDecl *D = LVal.Base.dyn_cast<const ValueDecl*>()) {
3170  // In C++98, const, non-volatile integers initialized with ICEs are ICEs.
3171  // In C++11, constexpr, non-volatile variables initialized with constant
3172  // expressions are constant expressions too. Inside constexpr functions,
3173  // parameters are constant expressions even if they're non-const.
3174  // In C++1y, objects local to a constant expression (those with a Frame) are
3175  // both readable and writable inside constant expressions.
3176  // In C, such things can also be folded, although they are not ICEs.
3177  const VarDecl *VD = dyn_cast<VarDecl>(D);
3178  if (VD) {
3179  if (const VarDecl *VDef = VD->getDefinition(Info.Ctx))
3180  VD = VDef;
3181  }
3182  if (!VD || VD->isInvalidDecl()) {
3183  Info.FFDiag(E);
3184  return CompleteObject();
3185  }
3186 
3187  // Accesses of volatile-qualified objects are not allowed.
3188  if (BaseType.isVolatileQualified()) {
3189  if (Info.getLangOpts().CPlusPlus) {
3190  Info.FFDiag(E, diag::note_constexpr_access_volatile_obj, 1)
3191  << AK << 1 << VD;
3192  Info.Note(VD->getLocation(), diag::note_declared_at);
3193  } else {
3194  Info.FFDiag(E);
3195  }
3196  return CompleteObject();
3197  }
3198 
3199  // Unless we're looking at a local variable or argument in a constexpr call,
3200  // the variable we're reading must be const.
3201  if (!Frame) {
3202  if (Info.getLangOpts().CPlusPlus14 &&
3203  VD == Info.EvaluatingDecl.dyn_cast<const ValueDecl *>()) {
3204  // OK, we can read and modify an object if we're in the process of
3205  // evaluating its initializer, because its lifetime began in this
3206  // evaluation.
3207  } else if (AK != AK_Read) {
3208  // All the remaining cases only permit reading.
3209  Info.FFDiag(E, diag::note_constexpr_modify_global);
3210  return CompleteObject();
3211  } else if (VD->isConstexpr()) {
3212  // OK, we can read this variable.
3213  } else if (BaseType->isIntegralOrEnumerationType()) {
3214  // In OpenCL if a variable is in constant address space it is a const value.
3215  if (!(BaseType.isConstQualified() ||
3216  (Info.getLangOpts().OpenCL &&
3217  BaseType.getAddressSpace() == LangAS::opencl_constant))) {
3218  if (Info.getLangOpts().CPlusPlus) {
3219  Info.FFDiag(E, diag::note_constexpr_ltor_non_const_int, 1) << VD;
3220  Info.Note(VD->getLocation(), diag::note_declared_at);
3221  } else {
3222  Info.FFDiag(E);
3223  }
3224  return CompleteObject();
3225  }
3226  } else if (BaseType->isFloatingType() && BaseType.isConstQualified()) {
3227  // We support folding of const floating-point types, in order to make
3228  // static const data members of such types (supported as an extension)
3229  // more useful.
3230  if (Info.getLangOpts().CPlusPlus11) {
3231  Info.CCEDiag(E, diag::note_constexpr_ltor_non_constexpr, 1) << VD;
3232  Info.Note(VD->getLocation(), diag::note_declared_at);
3233  } else {
3234  Info.CCEDiag(E);
3235  }
3236  } else if (BaseType.isConstQualified() && VD->hasDefinition(Info.Ctx)) {
3237  Info.CCEDiag(E, diag::note_constexpr_ltor_non_constexpr) << VD;
3238  // Keep evaluating to see what we can do.
3239  } else {
3240  // FIXME: Allow folding of values of any literal type in all languages.
3241  if (Info.checkingPotentialConstantExpression() &&
3242  VD->getType().isConstQualified() && !VD->hasDefinition(Info.Ctx)) {
3243  // The definition of this variable could be constexpr. We can't
3244  // access it right now, but may be able to in future.
3245  } else if (Info.getLangOpts().CPlusPlus11) {
3246  Info.FFDiag(E, diag::note_constexpr_ltor_non_constexpr, 1) << VD;
3247  Info.Note(VD->getLocation(), diag::note_declared_at);
3248  } else {
3249  Info.FFDiag(E);
3250  }
3251  return CompleteObject();
3252  }
3253  }
3254 
3255  if (!evaluateVarDeclInit(Info, E, VD, Frame, BaseVal, &LVal))
3256  return CompleteObject();
3257  } else {
3258  const Expr *Base = LVal.Base.dyn_cast<const Expr*>();
3259 
3260  if (!Frame) {
3261  if (const MaterializeTemporaryExpr *MTE =
3262  dyn_cast<MaterializeTemporaryExpr>(Base)) {
3263  assert(MTE->getStorageDuration() == SD_Static &&
3264  "should have a frame for a non-global materialized temporary");
3265 
3266  // Per C++1y [expr.const]p2:
3267  // an lvalue-to-rvalue conversion [is not allowed unless it applies to]
3268  // - a [...] glvalue of integral or enumeration type that refers to
3269  // a non-volatile const object [...]
3270  // [...]
3271  // - a [...] glvalue of literal type that refers to a non-volatile
3272  // object whose lifetime began within the evaluation of e.
3273  //
3274  // C++11 misses the 'began within the evaluation of e' check and
3275  // instead allows all temporaries, including things like:
3276  // int &&r = 1;
3277  // int x = ++r;
3278  // constexpr int k = r;
3279  // Therefore we use the C++14 rules in C++11 too.
3280  const ValueDecl *VD = Info.EvaluatingDecl.dyn_cast<const ValueDecl*>();
3281  const ValueDecl *ED = MTE->getExtendingDecl();
3282  if (!(BaseType.isConstQualified() &&
3283  BaseType->isIntegralOrEnumerationType()) &&
3284  !(VD && VD->getCanonicalDecl() == ED->getCanonicalDecl())) {
3285  Info.FFDiag(E, diag::note_constexpr_access_static_temporary, 1) << AK;
3286  Info.Note(MTE->getExprLoc(), diag::note_constexpr_temporary_here);
3287  return CompleteObject();
3288  }
3289 
3290  BaseVal = Info.Ctx.getMaterializedTemporaryValue(MTE, false);
3291  assert(BaseVal && "got reference to unevaluated temporary");
3292  LifetimeStartedInEvaluation = true;
3293  } else {
3294  Info.FFDiag(E);
3295  return CompleteObject();
3296  }
3297  } else {
3298  BaseVal = Frame->getTemporary(Base, LVal.Base.getVersion());
3299  assert(BaseVal && "missing value for temporary");
3300  }
3301 
3302  // Volatile temporary objects cannot be accessed in constant expressions.
3303  if (BaseType.isVolatileQualified()) {
3304  if (Info.getLangOpts().CPlusPlus) {
3305  Info.FFDiag(E, diag::note_constexpr_access_volatile_obj, 1)
3306  << AK << 0;
3307  Info.Note(Base->getExprLoc(), diag::note_constexpr_temporary_here);
3308  } else {
3309  Info.FFDiag(E);
3310  }
3311  return CompleteObject();
3312  }
3313  }
3314 
3315  // During the construction of an object, it is not yet 'const'.
3316  // FIXME: This doesn't do quite the right thing for const subobjects of the
3317  // object under construction.
3318  if (Info.isEvaluatingConstructor(LVal.getLValueBase(),
3319  LVal.getLValueCallIndex(),
3320  LVal.getLValueVersion())) {
3321  BaseType = Info.Ctx.getCanonicalType(BaseType);
3322  BaseType.removeLocalConst();
3323  LifetimeStartedInEvaluation = true;
3324  }
3325 
3326  // In C++14, we can't safely access any mutable state when we might be
3327  // evaluating after an unmodeled side effect.
3328  //
3329  // FIXME: Not all local state is mutable. Allow local constant subobjects
3330  // to be read here (but take care with 'mutable' fields).
3331  if ((Frame && Info.getLangOpts().CPlusPlus14 &&
3332  Info.EvalStatus.HasSideEffects) ||
3333  (AK != AK_Read && Info.IsSpeculativelyEvaluating))
3334  return CompleteObject();
3335 
3336  return CompleteObject(BaseVal, BaseType, LifetimeStartedInEvaluation);
3337 }
3338 
3339 /// Perform an lvalue-to-rvalue conversion on the given glvalue. This
3340 /// can also be used for 'lvalue-to-lvalue' conversions for looking up the
3341 /// glvalue referred to by an entity of reference type.
3342 ///
3343 /// \param Info - Information about the ongoing evaluation.
3344 /// \param Conv - The expression for which we are performing the conversion.
3345 /// Used for diagnostics.
3346 /// \param Type - The type of the glvalue (before stripping cv-qualifiers in the
3347 /// case of a non-class type).
3348 /// \param LVal - The glvalue on which we are attempting to perform this action.
3349 /// \param RVal - The produced value will be placed here.
3350 static bool handleLValueToRValueConversion(EvalInfo &Info, const Expr *Conv,
3351  QualType Type,
3352  const LValue &LVal, APValue &RVal) {
3353  if (LVal.Designator.Invalid)
3354  return false;
3355 
3356  // Check for special cases where there is no existing APValue to look at.
3357  const Expr *Base = LVal.Base.dyn_cast<const Expr*>();
3358  if (Base && !LVal.getLValueCallIndex() && !Type.isVolatileQualified()) {
3359  if (const CompoundLiteralExpr *CLE = dyn_cast<CompoundLiteralExpr>(Base)) {
3360  // In C99, a CompoundLiteralExpr is an lvalue, and we defer evaluating the
3361  // initializer until now for such expressions. Such an expression can't be
3362  // an ICE in C, so this only matters for fold.
3363  if (Type.isVolatileQualified()) {
3364  Info.FFDiag(Conv);
3365  return false;
3366  }
3367  APValue Lit;
3368  if (!Evaluate(Lit, Info, CLE->getInitializer()))
3369  return false;
3370  CompleteObject LitObj(&Lit, Base->getType(), false);
3371  return extractSubobject(Info, Conv, LitObj, LVal.Designator, RVal);
3372  } else if (isa<StringLiteral>(Base) || isa<PredefinedExpr>(Base)) {
3373  // Special-case character extraction so we don't have to construct an
3374  // APValue for the whole string.
3375  assert(LVal.Designator.Entries.size() <= 1 &&
3376  "Can only read characters from string literals");
3377  if (LVal.Designator.Entries.empty()) {
3378  // Fail for now for LValue to RValue conversion of an array.
3379  // (This shouldn't show up in C/C++, but it could be triggered by a
3380  // weird EvaluateAsRValue call from a tool.)
3381  Info.FFDiag(Conv);
3382  return false;
3383  }
3384  if (LVal.Designator.isOnePastTheEnd()) {
3385  if (Info.getLangOpts().CPlusPlus11)
3386  Info.FFDiag(Conv, diag::note_constexpr_access_past_end) << AK_Read;
3387  else
3388  Info.FFDiag(Conv);
3389  return false;
3390  }
3391  uint64_t CharIndex = LVal.Designator.Entries[0].ArrayIndex;
3392  RVal = APValue(extractStringLiteralCharacter(Info, Base, CharIndex));
3393  return true;
3394  }
3395  }
3396 
3397  CompleteObject Obj = findCompleteObject(Info, Conv, AK_Read, LVal, Type);
3398  return Obj && extractSubobject(Info, Conv, Obj, LVal.Designator, RVal);
3399 }
3400 
3401 /// Perform an assignment of Val to LVal. Takes ownership of Val.
3402 static bool handleAssignment(EvalInfo &Info, const Expr *E, const LValue &LVal,
3403  QualType LValType, APValue &Val) {
3404  if (LVal.Designator.Invalid)
3405  return false;
3406 
3407  if (!Info.getLangOpts().CPlusPlus14) {
3408  Info.FFDiag(E);
3409  return false;
3410  }
3411 
3412  CompleteObject Obj = findCompleteObject(Info, E, AK_Assign, LVal, LValType);
3413  return Obj && modifySubobject(Info, E, Obj, LVal.Designator, Val);
3414 }
3415 
3416 namespace {
3417 struct CompoundAssignSubobjectHandler {
3418  EvalInfo &Info;
3419  const Expr *E;
3420  QualType PromotedLHSType;
3421  BinaryOperatorKind Opcode;
3422  const APValue &RHS;
3423 
3424  static const AccessKinds AccessKind = AK_Assign;
3425 
3426  typedef bool result_type;
3427 
3428  bool checkConst(QualType QT) {
3429  // Assigning to a const object has undefined behavior.
3430  if (QT.isConstQualified()) {
3431  Info.FFDiag(E, diag::note_constexpr_modify_const_type) << QT;
3432  return false;
3433  }
3434  return true;
3435  }
3436 
3437  bool failed() { return false; }
3438  bool found(APValue &Subobj, QualType SubobjType) {
3439  switch (Subobj.getKind()) {
3440  case APValue::Int:
3441  return found(Subobj.getInt(), SubobjType);
3442  case APValue::Float:
3443  return found(Subobj.getFloat(), SubobjType);
3444  case APValue::ComplexInt:
3445  case APValue::ComplexFloat:
3446  // FIXME: Implement complex compound assignment.
3447  Info.FFDiag(E);
3448  return false;
3449  case APValue::LValue:
3450  return foundPointer(Subobj, SubobjType);
3451  default:
3452  // FIXME: can this happen?
3453  Info.FFDiag(E);
3454  return false;
3455  }
3456  }
3457  bool found(APSInt &Value, QualType SubobjType) {
3458  if (!checkConst(SubobjType))
3459  return false;
3460 
3461  if (!SubobjType->isIntegerType()) {
3462  // We don't support compound assignment on integer-cast-to-pointer
3463  // values.
3464  Info.FFDiag(E);
3465  return false;
3466  }
3467 
3468  if (RHS.isInt()) {
3469  APSInt LHS =
3470  HandleIntToIntCast(Info, E, PromotedLHSType, SubobjType, Value);
3471  if (!handleIntIntBinOp(Info, E, LHS, Opcode, RHS.getInt(), LHS))
3472  return false;
3473  Value = HandleIntToIntCast(Info, E, SubobjType, PromotedLHSType, LHS);
3474  return true;
3475  } else if (RHS.isFloat()) {
3476  APFloat FValue(0.0);
3477  return HandleIntToFloatCast(Info, E, SubobjType, Value, PromotedLHSType,
3478  FValue) &&
3479  handleFloatFloatBinOp(Info, E, FValue, Opcode, RHS.getFloat()) &&
3480  HandleFloatToIntCast(Info, E, PromotedLHSType, FValue, SubobjType,
3481  Value);
3482  }
3483 
3484  Info.FFDiag(E);
3485  return false;
3486  }
3487  bool found(APFloat &Value, QualType SubobjType) {
3488  return checkConst(SubobjType) &&
3489  HandleFloatToFloatCast(Info, E, SubobjType, PromotedLHSType,
3490  Value) &&
3491  handleFloatFloatBinOp(Info, E, Value, Opcode, RHS.getFloat()) &&
3492  HandleFloatToFloatCast(Info, E, PromotedLHSType, SubobjType, Value);
3493  }
3494  bool foundPointer(APValue &Subobj, QualType SubobjType) {
3495  if (!checkConst(SubobjType))
3496  return false;
3497 
3498  QualType PointeeType;
3499  if (const PointerType *PT = SubobjType->getAs<PointerType>())
3500  PointeeType = PT->getPointeeType();
3501 
3502  if (PointeeType.isNull() || !RHS.isInt() ||
3503  (Opcode != BO_Add && Opcode != BO_Sub)) {
3504  Info.FFDiag(E);
3505  return false;
3506  }
3507 
3508  APSInt Offset = RHS.getInt();
3509  if (Opcode == BO_Sub)
3510  negateAsSigned(Offset);
3511 
3512  LValue LVal;
3513  LVal.setFrom(Info.Ctx, Subobj);
3514  if (!HandleLValueArrayAdjustment(Info, E, LVal, PointeeType, Offset))
3515  return false;
3516  LVal.moveInto(Subobj);
3517  return true;
3518  }
3519 };
3520 } // end anonymous namespace
3521 
3523 
3524 /// Perform a compound assignment of LVal <op>= RVal.
3526  EvalInfo &Info, const Expr *E,
3527  const LValue &LVal, QualType LValType, QualType PromotedLValType,
3528  BinaryOperatorKind Opcode, const APValue &RVal) {
3529  if (LVal.Designator.Invalid)
3530  return false;
3531 
3532  if (!Info.getLangOpts().CPlusPlus14) {
3533  Info.FFDiag(E);
3534  return false;
3535  }
3536 
3537  CompleteObject Obj = findCompleteObject(Info, E, AK_Assign, LVal, LValType);
3538  CompoundAssignSubobjectHandler Handler = { Info, E, PromotedLValType, Opcode,
3539  RVal };
3540  return Obj && findSubobject(Info, E, Obj, LVal.Designator, Handler);
3541 }
3542 
3543 namespace {
3544 struct IncDecSubobjectHandler {
3545  EvalInfo &Info;
3546  const UnaryOperator *E;
3548  APValue *Old;
3549 
3550  typedef bool result_type;
3551 
3552  bool checkConst(QualType QT) {
3553  // Assigning to a const object has undefined behavior.
3554  if (QT.isConstQualified()) {
3555  Info.FFDiag(E, diag::note_constexpr_modify_const_type) << QT;
3556  return false;
3557  }
3558  return true;
3559  }
3560 
3561  bool failed() { return false; }
3562  bool found(APValue &Subobj, QualType SubobjType) {
3563  // Stash the old value. Also clear Old, so we don't clobber it later
3564  // if we're post-incrementing a complex.
3565  if (Old) {
3566  *Old = Subobj;
3567  Old = nullptr;
3568  }
3569 
3570  switch (Subobj.getKind()) {
3571  case APValue::Int:
3572  return found(Subobj.getInt(), SubobjType);
3573  case APValue::Float:
3574  return found(Subobj.getFloat(), SubobjType);
3575  case APValue::ComplexInt:
3576  return found(Subobj.getComplexIntReal(),
3577  SubobjType->castAs<ComplexType>()->getElementType()
3578  .withCVRQualifiers(SubobjType.getCVRQualifiers()));
3579  case APValue::ComplexFloat:
3580  return found(Subobj.getComplexFloatReal(),
3581  SubobjType->castAs<ComplexType>()->getElementType()
3582  .withCVRQualifiers(SubobjType.getCVRQualifiers()));
3583  case APValue::LValue:
3584  return foundPointer(Subobj, SubobjType);
3585  default:
3586  // FIXME: can this happen?
3587  Info.FFDiag(E);
3588  return false;
3589  }
3590  }
3591  bool found(APSInt &Value, QualType SubobjType) {
3592  if (!checkConst(SubobjType))
3593  return false;
3594 
3595  if (!SubobjType->isIntegerType()) {
3596  // We don't support increment / decrement on integer-cast-to-pointer
3597  // values.
3598  Info.FFDiag(E);
3599  return false;
3600  }
3601 
3602  if (Old) *Old = APValue(Value);
3603 
3604  // bool arithmetic promotes to int, and the conversion back to bool
3605  // doesn't reduce mod 2^n, so special-case it.
3606  if (SubobjType->isBooleanType()) {
3607  if (AccessKind == AK_Increment)
3608  Value = 1;
3609  else
3610  Value = !Value;
3611  return true;
3612  }
3613 
3614  bool WasNegative = Value.isNegative();
3615  if (AccessKind == AK_Increment) {
3616  ++Value;
3617 
3618  if (!WasNegative && Value.isNegative() && E->canOverflow()) {
3619  APSInt ActualValue(Value, /*IsUnsigned*/true);
3620  return HandleOverflow(Info, E, ActualValue, SubobjType);
3621  }
3622  } else {
3623  --Value;
3624 
3625  if (WasNegative && !Value.isNegative() && E->canOverflow()) {
3626  unsigned BitWidth = Value.getBitWidth();
3627  APSInt ActualValue(Value.sext(BitWidth + 1), /*IsUnsigned*/false);
3628  ActualValue.setBit(BitWidth);
3629  return HandleOverflow(Info, E, ActualValue, SubobjType);
3630  }
3631  }
3632  return true;
3633  }
3634  bool found(APFloat &Value, QualType SubobjType) {
3635  if (!checkConst(SubobjType))
3636  return false;
3637 
3638  if (Old) *Old = APValue(Value);
3639 
3640  APFloat One(Value.getSemantics(), 1);
3641  if (AccessKind == AK_Increment)
3642  Value.add(One, APFloat::rmNearestTiesToEven);
3643  else
3644  Value.subtract(One, APFloat::rmNearestTiesToEven);
3645  return true;
3646  }
3647  bool foundPointer(APValue &Subobj, QualType SubobjType) {
3648  if (!checkConst(SubobjType))
3649  return false;
3650 
3651  QualType PointeeType;
3652  if (const PointerType *PT = SubobjType->getAs<PointerType>())
3653  PointeeType = PT->getPointeeType();
3654  else {
3655  Info.FFDiag(E);
3656  return false;
3657  }
3658 
3659  LValue LVal;
3660  LVal.setFrom(Info.Ctx, Subobj);
3661  if (!HandleLValueArrayAdjustment(Info, E, LVal, PointeeType,
3662  AccessKind == AK_Increment ? 1 : -1))
3663  return false;
3664  LVal.moveInto(Subobj);
3665  return true;
3666  }
3667 };
3668 } // end anonymous namespace
3669 
3670 /// Perform an increment or decrement on LVal.
3671 static bool handleIncDec(EvalInfo &Info, const Expr *E, const LValue &LVal,
3672  QualType LValType, bool IsIncrement, APValue *Old) {
3673  if (LVal.Designator.Invalid)
3674  return false;
3675 
3676  if (!Info.getLangOpts().CPlusPlus14) {
3677  Info.FFDiag(E);
3678  return false;
3679  }
3680 
3681  AccessKinds AK = IsIncrement ? AK_Increment : AK_Decrement;
3682  CompleteObject Obj = findCompleteObject(Info, E, AK, LVal, LValType);
3683  IncDecSubobjectHandler Handler = {Info, cast<UnaryOperator>(E), AK, Old};
3684  return Obj && findSubobject(Info, E, Obj, LVal.Designator, Handler);
3685 }
3686 
3687 /// Build an lvalue for the object argument of a member function call.
3688 static bool EvaluateObjectArgument(EvalInfo &Info, const Expr *Object,
3689  LValue &This) {
3690  if (Object->getType()->isPointerType())
3691  return EvaluatePointer(Object, This, Info);
3692 
3693  if (Object->isGLValue())
3694  return EvaluateLValue(Object, This, Info);
3695 
3696  if (Object->getType()->isLiteralType(Info.Ctx))
3697  return EvaluateTemporary(Object, This, Info);
3698 
3699  Info.FFDiag(Object, diag::note_constexpr_nonliteral) << Object->getType();
3700  return false;
3701 }
3702 
3703 /// HandleMemberPointerAccess - Evaluate a member access operation and build an
3704 /// lvalue referring to the result.
3705 ///
3706 /// \param Info - Information about the ongoing evaluation.
3707 /// \param LV - An lvalue referring to the base of the member pointer.
3708 /// \param RHS - The member pointer expression.
3709 /// \param IncludeMember - Specifies whether the member itself is included in
3710 /// the resulting LValue subobject designator. This is not possible when
3711 /// creating a bound member function.
3712 /// \return The field or method declaration to which the member pointer refers,
3713 /// or 0 if evaluation fails.
3714 static const ValueDecl *HandleMemberPointerAccess(EvalInfo &Info,
3715  QualType LVType,
3716  LValue &LV,
3717  const Expr *RHS,
3718  bool IncludeMember = true) {
3719  MemberPtr MemPtr;
3720  if (!EvaluateMemberPointer(RHS, MemPtr, Info))
3721  return nullptr;
3722 
3723  // C++11 [expr.mptr.oper]p6: If the second operand is the null pointer to
3724  // member value, the behavior is undefined.
3725  if (!MemPtr.getDecl()) {
3726  // FIXME: Specific diagnostic.
3727  Info.FFDiag(RHS);
3728  return nullptr;
3729  }
3730 
3731  if (MemPtr.isDerivedMember()) {
3732  // This is a member of some derived class. Truncate LV appropriately.
3733  // The end of the derived-to-base path for the base object must match the
3734  // derived-to-base path for the member pointer.
3735  if (LV.Designator.MostDerivedPathLength + MemPtr.Path.size() >
3736  LV.Designator.Entries.size()) {
3737  Info.FFDiag(RHS);
3738  return nullptr;
3739  }
3740  unsigned PathLengthToMember =
3741  LV.Designator.Entries.size() - MemPtr.Path.size();
3742  for (unsigned I = 0, N = MemPtr.Path.size(); I != N; ++I) {
3743  const CXXRecordDecl *LVDecl = getAsBaseClass(
3744  LV.Designator.Entries[PathLengthToMember + I]);
3745  const CXXRecordDecl *MPDecl = MemPtr.Path[I];
3746  if (LVDecl->getCanonicalDecl() != MPDecl->getCanonicalDecl()) {
3747  Info.FFDiag(RHS);
3748  return nullptr;
3749  }
3750  }
3751 
3752  // Truncate the lvalue to the appropriate derived class.
3753  if (!CastToDerivedClass(Info, RHS, LV, MemPtr.getContainingRecord(),
3754  PathLengthToMember))
3755  return nullptr;
3756  } else if (!MemPtr.Path.empty()) {
3757  // Extend the LValue path with the member pointer's path.
3758  LV.Designator.Entries.reserve(LV.Designator.Entries.size() +
3759  MemPtr.Path.size() + IncludeMember);
3760 
3761  // Walk down to the appropriate base class.
3762  if (const PointerType *PT = LVType->getAs<PointerType>())
3763  LVType = PT->getPointeeType();
3764  const CXXRecordDecl *RD = LVType->getAsCXXRecordDecl();
3765  assert(RD && "member pointer access on non-class-type expression");
3766  // The first class in the path is that of the lvalue.
3767  for (unsigned I = 1, N = MemPtr.Path.size(); I != N; ++I) {
3768  const CXXRecordDecl *Base = MemPtr.Path[N - I - 1];
3769  if (!HandleLValueDirectBase(Info, RHS, LV, RD, Base))
3770  return nullptr;
3771  RD = Base;
3772  }
3773  // Finally cast to the class containing the member.
3774  if (!HandleLValueDirectBase(Info, RHS, LV, RD,
3775  MemPtr.getContainingRecord()))
3776  return nullptr;
3777  }
3778 
3779  // Add the member. Note that we cannot build bound member functions here.
3780  if (IncludeMember) {
3781  if (const FieldDecl *FD = dyn_cast<FieldDecl>(MemPtr.getDecl())) {
3782  if (!HandleLValueMember(Info, RHS, LV, FD))
3783  return nullptr;
3784  } else if (const IndirectFieldDecl *IFD =
3785  dyn_cast<IndirectFieldDecl>(MemPtr.getDecl())) {
3786  if (!HandleLValueIndirectMember(Info, RHS, LV, IFD))
3787  return nullptr;
3788  } else {
3789  llvm_unreachable("can't construct reference to bound member function");
3790  }
3791  }
3792 
3793  return MemPtr.getDecl();
3794 }
3795 
3796 static const ValueDecl *HandleMemberPointerAccess(EvalInfo &Info,
3797  const BinaryOperator *BO,
3798  LValue &LV,
3799  bool IncludeMember = true) {
3800  assert(BO->getOpcode() == BO_PtrMemD || BO->getOpcode() == BO_PtrMemI);
3801 
3802  if (!EvaluateObjectArgument(Info, BO->getLHS(), LV)) {
3803  if (Info.noteFailure()) {
3804  MemberPtr MemPtr;
3805  EvaluateMemberPointer(BO->getRHS(), MemPtr, Info);
3806  }
3807  return nullptr;
3808  }
3809 
3810  return HandleMemberPointerAccess(Info, BO->getLHS()->getType(), LV,
3811  BO->getRHS(), IncludeMember);
3812 }
3813 
3814 /// HandleBaseToDerivedCast - Apply the given base-to-derived cast operation on
3815 /// the provided lvalue, which currently refers to the base object.
3816 static bool HandleBaseToDerivedCast(EvalInfo &Info, const CastExpr *E,
3817  LValue &Result) {
3818  SubobjectDesignator &D = Result.Designator;
3819  if (D.Invalid || !Result.checkNullPointer(Info, E, CSK_Derived))
3820  return false;
3821 
3822  QualType TargetQT = E->getType();
3823  if (const PointerType *PT = TargetQT->getAs<PointerType>())
3824  TargetQT = PT->getPointeeType();
3825 
3826  // Check this cast lands within the final derived-to-base subobject path.
3827  if (D.MostDerivedPathLength + E->path_size() > D.Entries.size()) {
3828  Info.CCEDiag(E, diag::note_constexpr_invalid_downcast)
3829  << D.MostDerivedType << TargetQT;
3830  return false;
3831  }
3832 
3833  // Check the type of the final cast. We don't need to check the path,
3834  // since a cast can only be formed if the path is unique.
3835  unsigned NewEntriesSize = D.Entries.size() - E->path_size();
3836  const CXXRecordDecl *TargetType = TargetQT->getAsCXXRecordDecl();
3837  const CXXRecordDecl *FinalType;
3838  if (NewEntriesSize == D.MostDerivedPathLength)
3839  FinalType = D.MostDerivedType->getAsCXXRecordDecl();
3840  else
3841  FinalType = getAsBaseClass(D.Entries[NewEntriesSize - 1]);
3842  if (FinalType->getCanonicalDecl() != TargetType->getCanonicalDecl()) {
3843  Info.CCEDiag(E, diag::note_constexpr_invalid_downcast)
3844  << D.MostDerivedType << TargetQT;
3845  return false;
3846  }
3847 
3848  // Truncate the lvalue to the appropriate derived class.
3849  return CastToDerivedClass(Info, E, Result, TargetType, NewEntriesSize);
3850 }
3851 
3852 namespace {
3854  /// Evaluation failed.
3855  ESR_Failed,
3856  /// Hit a 'return' statement.
3857  ESR_Returned,
3858  /// Evaluation succeeded.
3859  ESR_Succeeded,
3860  /// Hit a 'continue' statement.
3861  ESR_Continue,
3862  /// Hit a 'break' statement.
3863  ESR_Break,
3864  /// Still scanning for 'case' or 'default' statement.
3865  ESR_CaseNotFound
3866 };
3867 }
3868 
3869 static bool EvaluateVarDecl(EvalInfo &Info, const VarDecl *VD) {
3870  // We don't need to evaluate the initializer for a static local.
3871  if (!VD->hasLocalStorage())
3872  return true;
3873 
3874  LValue Result;
3875  APValue &Val = createTemporary(VD, true, Result, *Info.CurrentCall);
3876 
3877  const Expr *InitE = VD->getInit();
3878  if (!InitE) {
3879  Info.FFDiag(VD->getBeginLoc(), diag::note_constexpr_uninitialized)
3880  << false << VD->getType();
3881  Val = APValue();
3882  return false;
3883  }
3884 
3885  if (InitE->isValueDependent())
3886  return false;
3887 
3888  if (!EvaluateInPlace(Val, Info, Result, InitE)) {
3889  // Wipe out any partially-computed value, to allow tracking that this
3890  // evaluation failed.
3891  Val = APValue();
3892  return false;
3893  }
3894 
3895  return true;
3896 }
3897 
3898 static bool EvaluateDecl(EvalInfo &Info, const Decl *D) {
3899  bool OK = true;
3900 
3901  if (const VarDecl *VD = dyn_cast<VarDecl>(D))
3902  OK &= EvaluateVarDecl(Info, VD);
3903 
3904  if (const DecompositionDecl *DD = dyn_cast<DecompositionDecl>(D))
3905  for (auto *BD : DD->bindings())
3906  if (auto *VD = BD->getHoldingVar())
3907  OK &= EvaluateDecl(Info, VD);
3908 
3909  return OK;
3910 }
3911 
3912 
3913 /// Evaluate a condition (either a variable declaration or an expression).
3914 static bool EvaluateCond(EvalInfo &Info, const VarDecl *CondDecl,
3915  const Expr *Cond, bool &Result) {
3916  FullExpressionRAII Scope(Info);
3917  if (CondDecl && !EvaluateDecl(Info, CondDecl))
3918  return false;
3919  return EvaluateAsBooleanCondition(Cond, Result, Info);
3920 }
3921 
3922 namespace {
3923 /// A location where the result (returned value) of evaluating a
3924 /// statement should be stored.
3925 struct StmtResult {
3926  /// The APValue that should be filled in with the returned value.
3927  APValue &Value;
3928  /// The location containing the result, if any (used to support RVO).
3929  const LValue *Slot;
3930 };
3931 
3932 struct TempVersionRAII {
3933  CallStackFrame &Frame;
3934 
3935  TempVersionRAII(CallStackFrame &Frame) : Frame(Frame) {
3936  Frame.pushTempVersion();
3937  }
3938 
3939  ~TempVersionRAII() {
3940  Frame.popTempVersion();
3941  }
3942 };
3943 
3944 }
3945 
3946 static EvalStmtResult EvaluateStmt(StmtResult &Result, EvalInfo &Info,
3947  const Stmt *S,
3948  const SwitchCase *SC = nullptr);
3949 
3950 /// Evaluate the body of a loop, and translate the result as appropriate.
3951 static EvalStmtResult EvaluateLoopBody(StmtResult &Result, EvalInfo &Info,
3952  const Stmt *Body,
3953  const SwitchCase *Case = nullptr) {
3954  BlockScopeRAII Scope(Info);
3955  switch (EvalStmtResult ESR = EvaluateStmt(Result, Info, Body, Case)) {
3956  case ESR_Break:
3957  return ESR_Succeeded;
3958  case ESR_Succeeded:
3959  case ESR_Continue:
3960  return ESR_Continue;
3961  case ESR_Failed:
3962  case ESR_Returned:
3963  case ESR_CaseNotFound:
3964  return ESR;
3965  }
3966  llvm_unreachable("Invalid EvalStmtResult!");
3967 }
3968 
3969 /// Evaluate a switch statement.
3970 static EvalStmtResult EvaluateSwitch(StmtResult &Result, EvalInfo &Info,
3971  const SwitchStmt *SS) {
3972  BlockScopeRAII Scope(Info);
3973 
3974  // Evaluate the switch condition.
3975  APSInt Value;
3976  {
3977  FullExpressionRAII Scope(Info);
3978  if (const Stmt *Init = SS->getInit()) {
3979  EvalStmtResult ESR = EvaluateStmt(Result, Info, Init);
3980  if (ESR != ESR_Succeeded)
3981  return ESR;
3982  }
3983  if (SS->getConditionVariable() &&
3984  !EvaluateDecl(Info, SS->getConditionVariable()))
3985  return ESR_Failed;
3986  if (!EvaluateInteger(SS->getCond(), Value, Info))
3987  return ESR_Failed;
3988  }
3989 
3990  // Find the switch case corresponding to the value of the condition.
3991  // FIXME: Cache this lookup.
3992  const SwitchCase *Found = nullptr;
3993  for (const SwitchCase *SC = SS->getSwitchCaseList(); SC;
3994  SC = SC->getNextSwitchCase()) {
3995  if (isa<DefaultStmt>(SC)) {
3996  Found = SC;
3997  continue;
3998  }
3999 
4000  const CaseStmt *CS = cast<CaseStmt>(SC);
4001  APSInt LHS = CS->getLHS()->EvaluateKnownConstInt(Info.Ctx);
4002  APSInt RHS = CS->getRHS() ? CS->getRHS()->EvaluateKnownConstInt(Info.Ctx)
4003  : LHS;
4004  if (LHS <= Value && Value <= RHS) {
4005  Found = SC;
4006  break;
4007  }
4008  }
4009 
4010  if (!Found)
4011  return ESR_Succeeded;
4012 
4013  // Search the switch body for the switch case and evaluate it from there.
4014  switch (EvalStmtResult ESR = EvaluateStmt(Result, Info, SS->getBody(), Found)) {
4015  case ESR_Break:
4016  return ESR_Succeeded;
4017  case ESR_Succeeded:
4018  case ESR_Continue:
4019  case ESR_Failed:
4020  case ESR_Returned:
4021  return ESR;
4022  case ESR_CaseNotFound:
4023  // This can only happen if the switch case is nested within a statement
4024  // expression. We have no intention of supporting that.
4025  Info.FFDiag(Found->getBeginLoc(),
4026  diag::note_constexpr_stmt_expr_unsupported);
4027  return ESR_Failed;
4028  }
4029  llvm_unreachable("Invalid EvalStmtResult!");
4030 }
4031 
4032 // Evaluate a statement.
4033 static EvalStmtResult EvaluateStmt(StmtResult &Result, EvalInfo &Info,
4034  const Stmt *S, const SwitchCase *Case) {
4035  if (!Info.nextStep(S))
4036  return ESR_Failed;
4037 
4038  // If we're hunting down a 'case' or 'default' label, recurse through
4039  // substatements until we hit the label.
4040  if (Case) {
4041  // FIXME: We don't start the lifetime of objects whose initialization we
4042  // jump over. However, such objects must be of class type with a trivial
4043  // default constructor that initialize all subobjects, so must be empty,
4044  // so this almost never matters.
4045  switch (S->getStmtClass()) {
4046  case Stmt::CompoundStmtClass:
4047  // FIXME: Precompute which substatement of a compound statement we
4048  // would jump to, and go straight there rather than performing a
4049  // linear scan each time.
4050  case Stmt::LabelStmtClass:
4051  case Stmt::AttributedStmtClass:
4052  case Stmt::DoStmtClass:
4053  break;
4054 
4055  case Stmt::CaseStmtClass:
4056  case Stmt::DefaultStmtClass:
4057  if (Case == S)
4058  Case = nullptr;
4059  break;
4060 
4061  case Stmt::IfStmtClass: {
4062  // FIXME: Precompute which side of an 'if' we would jump to, and go
4063  // straight there rather than scanning both sides.
4064  const IfStmt *IS = cast<IfStmt>(S);
4065 
4066  // Wrap the evaluation in a block scope, in case it's a DeclStmt
4067  // preceded by our switch label.
4068  BlockScopeRAII Scope(Info);
4069 
4070  EvalStmtResult ESR = EvaluateStmt(Result, Info, IS->getThen(), Case);
4071  if (ESR != ESR_CaseNotFound || !IS->getElse())
4072  return ESR;
4073  return EvaluateStmt(Result, Info, IS->getElse(), Case);
4074  }
4075 
4076  case Stmt::WhileStmtClass: {
4077  EvalStmtResult ESR =
4078  EvaluateLoopBody(Result, Info, cast<WhileStmt>(S)->getBody(), Case);
4079  if (ESR != ESR_Continue)
4080  return ESR;
4081  break;
4082  }
4083 
4084  case Stmt::ForStmtClass: {
4085  const ForStmt *FS = cast<ForStmt>(S);
4086  EvalStmtResult ESR =
4087  EvaluateLoopBody(Result, Info, FS->getBody(), Case);
4088  if (ESR != ESR_Continue)
4089  return ESR;
4090  if (FS->getInc()) {
4091  FullExpressionRAII IncScope(Info);
4092  if (!EvaluateIgnoredValue(Info, FS->getInc()))
4093  return ESR_Failed;
4094  }
4095  break;
4096  }
4097 
4098  case Stmt::DeclStmtClass:
4099  // FIXME: If the variable has initialization that can't be jumped over,
4100  // bail out of any immediately-surrounding compound-statement too.
4101  default:
4102  return ESR_CaseNotFound;
4103  }
4104  }
4105 
4106  switch (S->getStmtClass()) {
4107  default:
4108  if (const Expr *E = dyn_cast<Expr>(S)) {
4109  // Don't bother evaluating beyond an expression-statement which couldn't
4110  // be evaluated.
4111  FullExpressionRAII Scope(Info);
4112  if (!EvaluateIgnoredValue(Info, E))
4113  return ESR_Failed;
4114  return ESR_Succeeded;
4115  }
4116 
4117  Info.FFDiag(S->getBeginLoc());
4118  return ESR_Failed;
4119 
4120  case Stmt::NullStmtClass:
4121  return ESR_Succeeded;
4122 
4123  case Stmt::DeclStmtClass: {
4124  const DeclStmt *DS = cast<DeclStmt>(S);
4125  for (const auto *DclIt : DS->decls()) {
4126  // Each declaration initialization is its own full-expression.
4127  // FIXME: This isn't quite right; if we're performing aggregate
4128  // initialization, each braced subexpression is its own full-expression.
4129  FullExpressionRAII Scope(Info);
4130  if (!EvaluateDecl(Info, DclIt) && !Info.noteFailure())
4131  return ESR_Failed;
4132  }
4133  return ESR_Succeeded;
4134  }
4135 
4136  case Stmt::ReturnStmtClass: {
4137  const Expr *RetExpr = cast<ReturnStmt>(S)->getRetValue();
4138  FullExpressionRAII Scope(Info);
4139  if (RetExpr &&
4140  !(Result.Slot
4141  ? EvaluateInPlace(Result.Value, Info, *Result.Slot, RetExpr)
4142  : Evaluate(Result.Value, Info, RetExpr)))
4143  return ESR_Failed;
4144  return ESR_Returned;
4145  }
4146 
4147  case Stmt::CompoundStmtClass: {
4148  BlockScopeRAII Scope(Info);
4149 
4150  const CompoundStmt *CS = cast<CompoundStmt>(S);
4151  for (const auto *BI : CS->body()) {
4152  EvalStmtResult ESR = EvaluateStmt(Result, Info, BI, Case);
4153  if (ESR == ESR_Succeeded)
4154  Case = nullptr;
4155  else if (ESR != ESR_CaseNotFound)
4156  return ESR;
4157  }
4158  return Case ? ESR_CaseNotFound : ESR_Succeeded;
4159  }
4160 
4161  case Stmt::IfStmtClass: {
4162  const IfStmt *IS = cast<IfStmt>(S);
4163 
4164  // Evaluate the condition, as either a var decl or as an expression.
4165  BlockScopeRAII Scope(Info);
4166  if (const Stmt *Init = IS->getInit()) {
4167  EvalStmtResult ESR = EvaluateStmt(Result, Info, Init);
4168  if (ESR != ESR_Succeeded)
4169  return ESR;
4170  }
4171  bool Cond;
4172  if (!EvaluateCond(Info, IS->getConditionVariable(), IS->getCond(), Cond))
4173  return ESR_Failed;
4174 
4175  if (const Stmt *SubStmt = Cond ? IS->getThen() : IS->getElse()) {
4176  EvalStmtResult ESR = EvaluateStmt(Result, Info, SubStmt);
4177  if (ESR != ESR_Succeeded)
4178  return ESR;
4179  }
4180  return ESR_Succeeded;
4181  }
4182 
4183  case Stmt::WhileStmtClass: {
4184  const WhileStmt *WS = cast<WhileStmt>(S);
4185  while (true) {
4186  BlockScopeRAII Scope(Info);
4187  bool Continue;
4188  if (!EvaluateCond(Info, WS->getConditionVariable(), WS->getCond(),
4189  Continue))
4190  return ESR_Failed;
4191  if (!Continue)
4192  break;
4193 
4194  EvalStmtResult ESR = EvaluateLoopBody(Result, Info, WS->getBody());
4195  if (ESR != ESR_Continue)
4196  return ESR;
4197  }
4198  return ESR_Succeeded;
4199  }
4200 
4201  case Stmt::DoStmtClass: {
4202  const DoStmt *DS = cast<DoStmt>(S);
4203  bool Continue;
4204  do {
4205  EvalStmtResult ESR = EvaluateLoopBody(Result, Info, DS->getBody(), Case);
4206  if (ESR != ESR_Continue)
4207  return ESR;
4208  Case = nullptr;
4209 
4210  FullExpressionRAII CondScope(Info);
4211  if (!EvaluateAsBooleanCondition(DS->getCond(), Continue, Info))
4212  return ESR_Failed;
4213  } while (Continue);
4214  return ESR_Succeeded;
4215  }
4216 
4217  case Stmt::ForStmtClass: {
4218  const ForStmt *FS = cast<ForStmt>(S);
4219  BlockScopeRAII Scope(Info);
4220  if (FS->getInit()) {
4221  EvalStmtResult ESR = EvaluateStmt(Result, Info, FS->getInit());
4222  if (ESR != ESR_Succeeded)
4223  return ESR;
4224  }
4225  while (true) {
4226  BlockScopeRAII Scope(Info);
4227  bool Continue = true;
4228  if (FS->getCond() && !EvaluateCond(Info, FS->getConditionVariable(),
4229  FS->getCond(), Continue))
4230  return ESR_Failed;
4231  if (!Continue)
4232  break;
4233 
4234  EvalStmtResult ESR = EvaluateLoopBody(Result, Info, FS->getBody());
4235  if (ESR != ESR_Continue)
4236  return ESR;
4237 
4238  if (FS->getInc()) {
4239  FullExpressionRAII IncScope(Info);
4240  if (!EvaluateIgnoredValue(Info, FS->getInc()))
4241  return ESR_Failed;
4242  }
4243  }
4244  return ESR_Succeeded;
4245  }
4246 
4247  case Stmt::CXXForRangeStmtClass: {
4248  const CXXForRangeStmt *FS = cast<CXXForRangeStmt>(S);
4249  BlockScopeRAII Scope(Info);
4250 
4251  // Evaluate the init-statement if present.
4252  if (FS->getInit()) {
4253  EvalStmtResult ESR = EvaluateStmt(Result, Info, FS->getInit());
4254  if (ESR != ESR_Succeeded)
4255  return ESR;
4256  }
4257 
4258  // Initialize the __range variable.
4259  EvalStmtResult ESR = EvaluateStmt(Result, Info, FS->getRangeStmt());
4260  if (ESR != ESR_Succeeded)
4261  return ESR;
4262 
4263  // Create the __begin and __end iterators.
4264  ESR = EvaluateStmt(Result, Info, FS->getBeginStmt());
4265  if (ESR != ESR_Succeeded)
4266  return ESR;
4267  ESR = EvaluateStmt(Result, Info, FS->getEndStmt());
4268  if (ESR != ESR_Succeeded)
4269  return ESR;
4270 
4271  while (true) {
4272  // Condition: __begin != __end.
4273  {
4274  bool Continue = true;
4275  FullExpressionRAII CondExpr(Info);
4276  if (!EvaluateAsBooleanCondition(FS->getCond(), Continue, Info))
4277  return ESR_Failed;
4278  if (!Continue)
4279  break;
4280  }
4281 
4282  // User's variable declaration, initialized by *__begin.
4283  BlockScopeRAII InnerScope(Info);
4284  ESR = EvaluateStmt(Result, Info, FS->getLoopVarStmt());
4285  if (ESR != ESR_Succeeded)
4286  return ESR;
4287 
4288  // Loop body.
4289  ESR = EvaluateLoopBody(Result, Info, FS->getBody());
4290  if (ESR != ESR_Continue)
4291  return ESR;
4292 
4293  // Increment: ++__begin
4294  if (!EvaluateIgnoredValue(Info, FS->getInc()))
4295  return ESR_Failed;
4296  }
4297 
4298  return ESR_Succeeded;
4299  }
4300 
4301  case Stmt::SwitchStmtClass:
4302  return EvaluateSwitch(Result, Info, cast<SwitchStmt>(S));
4303 
4304  case Stmt::ContinueStmtClass:
4305  return ESR_Continue;
4306 
4307  case Stmt::BreakStmtClass:
4308  return ESR_Break;
4309 
4310  case Stmt::LabelStmtClass:
4311  return EvaluateStmt(Result, Info, cast<LabelStmt>(S)->getSubStmt(), Case);
4312 
4313  case Stmt::AttributedStmtClass:
4314  // As a general principle, C++11 attributes can be ignored without
4315  // any semantic impact.
4316  return EvaluateStmt(Result, Info, cast<AttributedStmt>(S)->getSubStmt(),
4317  Case);
4318 
4319  case Stmt::CaseStmtClass:
4320  case Stmt::DefaultStmtClass:
4321  return EvaluateStmt(Result, Info, cast<SwitchCase>(S)->getSubStmt(), Case);
4322  case Stmt::CXXTryStmtClass:
4323  // Evaluate try blocks by evaluating all sub statements.
4324  return EvaluateStmt(Result, Info, cast<CXXTryStmt>(S)->getTryBlock(), Case);
4325  }
4326 }
4327 
4328 /// CheckTrivialDefaultConstructor - Check whether a constructor is a trivial
4329 /// default constructor. If so, we'll fold it whether or not it's marked as
4330 /// constexpr. If it is marked as constexpr, we will never implicitly define it,
4331 /// so we need special handling.
4332 static bool CheckTrivialDefaultConstructor(EvalInfo &Info, SourceLocation Loc,
4333  const CXXConstructorDecl *CD,
4334  bool IsValueInitialization) {
4335  if (!CD->isTrivial() || !CD->isDefaultConstructor())
4336  return false;
4337 
4338  // Value-initialization does not call a trivial default constructor, so such a
4339  // call is a core constant expression whether or not the constructor is
4340  // constexpr.
4341  if (!CD->isConstexpr() && !IsValueInitialization) {
4342  if (Info.getLangOpts().CPlusPlus11) {
4343  // FIXME: If DiagDecl is an implicitly-declared special member function,
4344  // we should be much more explicit about why it's not constexpr.
4345  Info.CCEDiag(Loc, diag::note_constexpr_invalid_function, 1)
4346  << /*IsConstexpr*/0 << /*IsConstructor*/1 << CD;
4347  Info.Note(CD->getLocation(), diag::note_declared_at);
4348  } else {
4349  Info.CCEDiag(Loc, diag::note_invalid_subexpr_in_const_expr);
4350  }
4351  }
4352  return true;
4353 }
4354 
4355 /// CheckConstexprFunction - Check that a function can be called in a constant
4356 /// expression.
4357 static bool CheckConstexprFunction(EvalInfo &Info, SourceLocation CallLoc,
4358  const FunctionDecl *Declaration,
4359  const FunctionDecl *Definition,
4360  const Stmt *Body) {
4361  // Potential constant expressions can contain calls to declared, but not yet
4362  // defined, constexpr functions.
4363  if (Info.checkingPotentialConstantExpression() && !Definition &&
4364  Declaration->isConstexpr())
4365  return false;
4366 
4367  // Bail out if the function declaration itself is invalid. We will
4368  // have produced a relevant diagnostic while parsing it, so just
4369  // note the problematic sub-expression.
4370  if (Declaration->isInvalidDecl()) {
4371  Info.FFDiag(CallLoc, diag::note_invalid_subexpr_in_const_expr);
4372  return false;
4373  }
4374 
4375  // Can we evaluate this function call?
4376  if (Definition && Definition->isConstexpr() &&
4377  !Definition->isInvalidDecl() && Body)
4378  return true;
4379 
4380  if (Info.getLangOpts().CPlusPlus11) {
4381  const FunctionDecl *DiagDecl = Definition ? Definition : Declaration;
4382 
4383  // If this function is not constexpr because it is an inherited
4384  // non-constexpr constructor, diagnose that directly.
4385  auto *CD = dyn_cast<CXXConstructorDecl>(DiagDecl);
4386  if (CD && CD->isInheritingConstructor()) {
4387  auto *Inherited = CD->getInheritedConstructor().getConstructor();
4388  if (!Inherited->isConstexpr())
4389  DiagDecl = CD = Inherited;
4390  }
4391 
4392  // FIXME: If DiagDecl is an implicitly-declared special member function
4393  // or an inheriting constructor, we should be much more explicit about why
4394  // it's not constexpr.
4395  if (CD && CD->isInheritingConstructor())
4396  Info.FFDiag(CallLoc, diag::note_constexpr_invalid_inhctor, 1)
4397  << CD->getInheritedConstructor().getConstructor()->getParent();
4398  else
4399  Info.FFDiag(CallLoc, diag::note_constexpr_invalid_function, 1)
4400  << DiagDecl->isConstexpr() << (bool)CD << DiagDecl;
4401  Info.Note(DiagDecl->getLocation(), diag::note_declared_at);
4402  } else {
4403  Info.FFDiag(CallLoc, diag::note_invalid_subexpr_in_const_expr);
4404  }
4405  return false;
4406 }
4407 
4408 /// Determine if a class has any fields that might need to be copied by a
4409 /// trivial copy or move operation.
4410 static bool hasFields(const CXXRecordDecl *RD) {
4411  if (!RD || RD->isEmpty())
4412  return false;
4413  for (auto *FD : RD->fields()) {
4414  if (FD->isUnnamedBitfield())
4415  continue;
4416  return true;
4417  }
4418  for (auto &Base : RD->bases())
4419  if (hasFields(Base.getType()->getAsCXXRecordDecl()))
4420  return true;
4421  return false;
4422 }
4423 
4424 namespace {
4425 typedef SmallVector<APValue, 8> ArgVector;
4426 }
4427 
4428 /// EvaluateArgs - Evaluate the arguments to a function call.
4429 static bool EvaluateArgs(ArrayRef<const Expr*> Args, ArgVector &ArgValues,
4430  EvalInfo &Info) {
4431  bool Success = true;
4432  for (ArrayRef<const Expr*>::iterator I = Args.begin(), E = Args.end();
4433  I != E; ++I) {
4434  if (!Evaluate(ArgValues[I - Args.begin()], Info, *I)) {
4435  // If we're checking for a potential constant expression, evaluate all
4436  // initializers even if some of them fail.
4437  if (!Info.noteFailure())
4438  return false;
4439  Success = false;
4440  }
4441  }
4442  return Success;
4443 }
4444 
4445 /// Evaluate a function call.
4447  const FunctionDecl *Callee, const LValue *This,
4448  ArrayRef<const Expr*> Args, const Stmt *Body,
4449  EvalInfo &Info, APValue &Result,
4450  const LValue *ResultSlot) {
4451  ArgVector ArgValues(Args.size());
4452  if (!EvaluateArgs(Args, ArgValues, Info))
4453  return false;
4454 
4455  if (!Info.CheckCallLimit(CallLoc))
4456  return false;
4457 
4458  CallStackFrame Frame(Info, CallLoc, Callee, This, ArgValues.data());
4459 
4460  // For a trivial copy or move assignment, perform an APValue copy. This is
4461  // essential for unions, where the operations performed by the assignment
4462  // operator cannot be represented as statements.
4463  //
4464  // Skip this for non-union classes with no fields; in that case, the defaulted
4465  // copy/move does not actually read the object.
4466  const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(Callee);
4467  if (MD && MD->isDefaulted() &&
4468  (MD->getParent()->isUnion() ||
4469  (MD->isTrivial() && hasFields(MD->getParent())))) {
4470  assert(This &&
4471  (MD->isCopyAssignmentOperator() || MD->isMoveAssignmentOperator()));
4472  LValue RHS;
4473  RHS.setFrom(Info.Ctx, ArgValues[0]);
4474  APValue RHSValue;
4475  if (!handleLValueToRValueConversion(Info, Args[0], Args[0]->getType(),
4476  RHS, RHSValue))
4477  return false;
4478  if (!handleAssignment(Info, Args[0], *This, MD->getThisType(),
4479  RHSValue))
4480  return false;
4481  This->moveInto(Result);
4482  return true;
4483  } else if (MD && isLambdaCallOperator(MD)) {
4484  // We're in a lambda; determine the lambda capture field maps unless we're
4485  // just constexpr checking a lambda's call operator. constexpr checking is
4486  // done before the captures have been added to the closure object (unless
4487  // we're inferring constexpr-ness), so we don't have access to them in this
4488  // case. But since we don't need the captures to constexpr check, we can
4489  // just ignore them.
4490  if (!Info.checkingPotentialConstantExpression())
4491  MD->getParent()->getCaptureFields(Frame.LambdaCaptureFields,
4492  Frame.LambdaThisCaptureField);
4493  }
4494 
4495  StmtResult Ret = {Result, ResultSlot};
4496  EvalStmtResult ESR = EvaluateStmt(Ret, Info, Body);
4497  if (ESR == ESR_Succeeded) {
4498  if (Callee->getReturnType()->isVoidType())
4499  return true;
4500  Info.FFDiag(Callee->getEndLoc(), diag::note_constexpr_no_return);
4501  }
4502  return ESR == ESR_Returned;
4503 }
4504 
4505 /// Evaluate a constructor call.
4506 static bool HandleConstructorCall(const Expr *E, const LValue &This,
4507  APValue *ArgValues,
4508  const CXXConstructorDecl *Definition,
4509  EvalInfo &Info, APValue &Result) {
4510  SourceLocation CallLoc = E->getExprLoc();
4511  if (!Info.CheckCallLimit(CallLoc))
4512  return false;
4513 
4514  const CXXRecordDecl *RD = Definition->getParent();
4515  if (RD->getNumVBases()) {
4516  Info.FFDiag(CallLoc, diag::note_constexpr_virtual_base) << RD;
4517  return false;
4518  }
4519 
4520  EvalInfo::EvaluatingConstructorRAII EvalObj(
4521  Info, {This.getLValueBase(),
4522  {This.getLValueCallIndex(), This.getLValueVersion()}});
4523  CallStackFrame Frame(Info, CallLoc, Definition, &This, ArgValues);
4524 
4525  // FIXME: Creating an APValue just to hold a nonexistent return value is
4526  // wasteful.
4527  APValue RetVal;
4528  StmtResult Ret = {RetVal, nullptr};
4529 
4530  // If it's a delegating constructor, delegate.
4531  if (Definition->isDelegatingConstructor()) {
4533  {
4534  FullExpressionRAII InitScope(Info);
4535  if (!EvaluateInPlace(Result, Info, This, (*I)->getInit()))
4536  return false;
4537  }
4538  return EvaluateStmt(Ret, Info, Definition->getBody()) != ESR_Failed;
4539  }
4540 
4541  // For a trivial copy or move constructor, perform an APValue copy. This is
4542  // essential for unions (or classes with anonymous union members), where the
4543  // operations performed by the constructor cannot be represented by
4544  // ctor-initializers.
4545  //
4546  // Skip this for empty non-union classes; we should not perform an
4547  // lvalue-to-rvalue conversion on them because their copy constructor does not
4548  // actually read them.
4549  if (Definition->isDefaulted() && Definition->isCopyOrMoveConstructor() &&
4550  (Definition->getParent()->isUnion() ||
4551  (Definition->isTrivial() && hasFields(Definition->getParent())))) {
4552  LValue RHS;
4553  RHS.setFrom(Info.Ctx, ArgValues[0]);
4555  Info, E, Definition->getParamDecl(0)->getType().getNonReferenceType(),
4556  RHS, Result);
4557  }
4558 
4559  // Reserve space for the struct members.
4560  if (!RD->isUnion() && Result.isUninit())
4561  Result = APValue(APValue::UninitStruct(), RD->getNumBases(),
4562  std::distance(RD->field_begin(), RD->field_end()));
4563 
4564  if (RD->isInvalidDecl()) return false;
4565  const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
4566 
4567  // A scope for temporaries lifetime-extended by reference members.
4568  BlockScopeRAII LifetimeExtendedScope(Info);
4569 
4570  bool Success = true;
4571  unsigned BasesSeen = 0;
4572 #ifndef NDEBUG
4574 #endif
4575  for (const auto *I : Definition->inits()) {
4576  LValue Subobject = This;
4577  LValue SubobjectParent = This;
4578  APValue *Value = &Result;
4579 
4580  // Determine the subobject to initialize.
4581  FieldDecl *FD = nullptr;
4582  if (I->isBaseInitializer()) {
4583  QualType BaseType(I->getBaseClass(), 0);
4584 #ifndef NDEBUG
4585  // Non-virtual base classes are initialized in the order in the class
4586  // definition. We have already checked for virtual base classes.
4587  assert(!BaseIt->isVirtual() && "virtual base for literal type");
4588  assert(Info.Ctx.hasSameType(BaseIt->getType(), BaseType) &&
4589  "base class initializers not in expected order");
4590  ++BaseIt;
4591 #endif
4592  if (!HandleLValueDirectBase(Info, I->getInit(), Subobject, RD,
4593  BaseType->getAsCXXRecordDecl(), &Layout))
4594  return false;
4595  Value = &Result.getStructBase(BasesSeen++);
4596  } else if ((FD = I->getMember())) {
4597  if (!HandleLValueMember(Info, I->getInit(), Subobject, FD, &Layout))
4598  return false;
4599  if (RD->isUnion()) {
4600  Result = APValue(FD);
4601  Value = &Result.getUnionValue();
4602  } else {
4603  Value = &Result.getStructField(FD->getFieldIndex());
4604  }
4605  } else if (IndirectFieldDecl *IFD = I->getIndirectMember()) {
4606  // Walk the indirect field decl's chain to find the object to initialize,
4607  // and make sure we've initialized every step along it.
4608  auto IndirectFieldChain = IFD->chain();
4609  for (auto *C : IndirectFieldChain) {
4610  FD = cast<FieldDecl>(C);
4611  CXXRecordDecl *CD = cast<CXXRecordDecl>(FD->getParent());
4612  // Switch the union field if it differs. This happens if we had
4613  // preceding zero-initialization, and we're now initializing a union
4614  // subobject other than the first.
4615  // FIXME: In this case, the values of the other subobjects are
4616  // specified, since zero-initialization sets all padding bits to zero.
4617  if (Value->isUninit() ||
4618  (Value->isUnion() && Value->getUnionField() != FD)) {
4619  if (CD->isUnion())
4620  *Value = APValue(FD);
4621  else
4622  *Value = APValue(APValue::UninitStruct(), CD->getNumBases(),
4623  std::distance(CD->field_begin(), CD->field_end()));
4624  }
4625  // Store Subobject as its parent before updating it for the last element
4626  // in the chain.
4627  if (C == IndirectFieldChain.back())
4628  SubobjectParent = Subobject;
4629  if (!HandleLValueMember(Info, I->getInit(), Subobject, FD))
4630  return false;
4631  if (CD->isUnion())
4632  Value = &Value->getUnionValue();
4633  else
4634  Value = &Value->getStructField(FD->getFieldIndex());
4635  }
4636  } else {
4637  llvm_unreachable("unknown base initializer kind");
4638  }
4639 
4640  // Need to override This for implicit field initializers as in this case
4641  // This refers to innermost anonymous struct/union containing initializer,
4642  // not to currently constructed class.
4643  const Expr *Init = I->getInit();
4644  ThisOverrideRAII ThisOverride(*Info.CurrentCall, &SubobjectParent,
4645  isa<CXXDefaultInitExpr>(Init));
4646  FullExpressionRAII InitScope(Info);
4647  if (!EvaluateInPlace(*Value, Info, Subobject, Init) ||
4648  (FD && FD->isBitField() &&
4649  !truncateBitfieldValue(Info, Init, *Value, FD))) {
4650  // If we're checking for a potential constant expression, evaluate all
4651  // initializers even if some of them fail.
4652  if (!Info.noteFailure())
4653  return false;
4654  Success = false;
4655  }
4656  }
4657 
4658  return Success &&
4659  EvaluateStmt(Ret, Info, Definition->getBody()) != ESR_Failed;
4660 }
4661 
4662 static bool HandleConstructorCall(const Expr *E, const LValue &This,
4663  ArrayRef<const Expr*> Args,
4664  const CXXConstructorDecl *Definition,
4665  EvalInfo &Info, APValue &Result) {
4666  ArgVector ArgValues(Args.size());
4667  if (!EvaluateArgs(Args, ArgValues, Info))
4668  return false;
4669 
4670  return HandleConstructorCall(E, This, ArgValues.data(), Definition,
4671  Info, Result);
4672 }
4673 
4674 //===----------------------------------------------------------------------===//
4675 // Generic Evaluation
4676 //===----------------------------------------------------------------------===//
4677 namespace {
4678 
4679 template <class Derived>
4680 class ExprEvaluatorBase
4681  : public ConstStmtVisitor<Derived, bool> {
4682 private:
4683  Derived &getDerived() { return static_cast<Derived&>(*this); }
4684  bool DerivedSuccess(const APValue &V, const Expr *E) {
4685  return getDerived().Success(V, E);
4686  }
4687  bool DerivedZeroInitialization(const Expr *E) {
4688  return getDerived().ZeroInitialization(E);
4689  }
4690 
4691  // Check whether a conditional operator with a non-constant condition is a
4692  // potential constant expression. If neither arm is a potential constant
4693  // expression, then the conditional operator is not either.
4694  template<typename ConditionalOperator>
4695  void CheckPotentialConstantConditional(const ConditionalOperator *E) {
4696  assert(Info.checkingPotentialConstantExpression());
4697 
4698  // Speculatively evaluate both arms.
4700  {
4701  SpeculativeEvaluationRAII Speculate(Info, &Diag);
4702  StmtVisitorTy::Visit(E->getFalseExpr());
4703  if (Diag.empty())
4704  return;
4705  }
4706 
4707  {
4708  SpeculativeEvaluationRAII Speculate(Info, &Diag);
4709  Diag.clear();
4710  StmtVisitorTy::Visit(E->getTrueExpr());
4711  if (Diag.empty())
4712  return;
4713  }
4714 
4715  Error(E, diag::note_constexpr_conditional_never_const);
4716  }
4717 
4718 
4719  template<typename ConditionalOperator>
4720  bool HandleConditionalOperator(const ConditionalOperator *E) {
4721  bool BoolResult;
4722  if (!EvaluateAsBooleanCondition(E->getCond(), BoolResult, Info)) {
4723  if (Info.checkingPotentialConstantExpression() && Info.noteFailure()) {
4724  CheckPotentialConstantConditional(E);
4725  return false;
4726  }
4727  if (Info.noteFailure()) {
4728  StmtVisitorTy::Visit(E->getTrueExpr());
4729  StmtVisitorTy::Visit(E->getFalseExpr());
4730  }
4731  return false;
4732  }
4733 
4734  Expr *EvalExpr = BoolResult ? E->getTrueExpr() : E->getFalseExpr();
4735  return StmtVisitorTy::Visit(EvalExpr);
4736  }
4737 
4738 protected:
4739  EvalInfo &Info;
4740  typedef ConstStmtVisitor<Derived, bool> StmtVisitorTy;
4741  typedef ExprEvaluatorBase ExprEvaluatorBaseTy;
4742 
4743  OptionalDiagnostic CCEDiag(const Expr *E, diag::kind D) {
4744  return Info.CCEDiag(E, D);
4745  }
4746 
4747  bool ZeroInitialization(const Expr *E) { return Error(E); }
4748 
4749 public:
4750  ExprEvaluatorBase(EvalInfo &Info) : Info(Info) {}
4751 
4752  EvalInfo &getEvalInfo() { return Info; }
4753 
4754  /// Report an evaluation error. This should only be called when an error is
4755  /// first discovered. When propagating an error, just return false.
4756  bool Error(const Expr *E, diag::kind D) {
4757  Info.FFDiag(E, D);
4758  return false;
4759  }
4760  bool Error(const Expr *E) {
4761  return Error(E, diag::note_invalid_subexpr_in_const_expr);
4762  }
4763 
4764  bool VisitStmt(const Stmt *) {
4765  llvm_unreachable("Expression evaluator should not be called on stmts");
4766  }
4767  bool VisitExpr(const Expr *E) {
4768  return Error(E);
4769  }
4770 
4771  bool VisitConstantExpr(const ConstantExpr *E)
4772  { return StmtVisitorTy::Visit(E->getSubExpr()); }
4773  bool VisitParenExpr(const ParenExpr *E)
4774  { return StmtVisitorTy::Visit(E->getSubExpr()); }
4775  bool VisitUnaryExtension(const UnaryOperator *E)
4776  { return StmtVisitorTy::Visit(E->getSubExpr()); }
4777  bool VisitUnaryPlus(const UnaryOperator *E)
4778  { return StmtVisitorTy::Visit(E->getSubExpr()); }
4779  bool VisitChooseExpr(const ChooseExpr *E)
4780  { return StmtVisitorTy::Visit(E->getChosenSubExpr()); }
4781  bool VisitGenericSelectionExpr(const GenericSelectionExpr *E)
4782  { return StmtVisitorTy::Visit(E->getResultExpr()); }
4783  bool VisitSubstNonTypeTemplateParmExpr(const SubstNonTypeTemplateParmExpr *E)
4784  { return StmtVisitorTy::Visit(E->getReplacement()); }
4785  bool VisitCXXDefaultArgExpr(const CXXDefaultArgExpr *E) {
4786  TempVersionRAII RAII(*Info.CurrentCall);
4787  return StmtVisitorTy::Visit(E->getExpr());
4788  }
4789  bool VisitCXXDefaultInitExpr(const CXXDefaultInitExpr *E) {
4790  TempVersionRAII RAII(*Info.CurrentCall);
4791  // The initializer may not have been parsed yet, or might be erroneous.
4792  if (!E->getExpr())
4793  return Error(E);
4794  return StmtVisitorTy::Visit(E->getExpr());
4795  }
4796  // We cannot create any objects for which cleanups are required, so there is
4797  // nothing to do here; all cleanups must come from unevaluated subexpressions.
4798  bool VisitExprWithCleanups(const ExprWithCleanups *E)
4799  { return StmtVisitorTy::Visit(E->getSubExpr()); }
4800 
4801  bool VisitCXXReinterpretCastExpr(const CXXReinterpretCastExpr *E) {
4802  CCEDiag(E, diag::note_constexpr_invalid_cast) << 0;
4803  return static_cast<Derived*>(this)->VisitCastExpr(E);
4804  }
4805  bool VisitCXXDynamicCastExpr(const CXXDynamicCastExpr *E) {
4806  CCEDiag(E, diag::note_constexpr_invalid_cast) << 1;
4807  return static_cast<Derived*>(this)->VisitCastExpr(E);
4808  }
4809 
4810  bool VisitBinaryOperator(const BinaryOperator *E) {
4811  switch (E->getOpcode()) {
4812  default:
4813  return Error(E);
4814 
4815  case BO_Comma:
4816  VisitIgnoredValue(E->getLHS());
4817  return StmtVisitorTy::Visit(E->getRHS());
4818 
4819  case BO_PtrMemD:
4820  case BO_PtrMemI: {
4821  LValue Obj;
4822  if (!HandleMemberPointerAccess(Info, E, Obj))
4823  return false;
4824  APValue Result;
4825  if (!handleLValueToRValueConversion(Info, E, E->getType(), Obj, Result))
4826  return false;
4827  return DerivedSuccess(Result, E);
4828  }
4829  }
4830  }
4831 
4832  bool VisitBinaryConditionalOperator(const BinaryConditionalOperator *E) {
4833  // Evaluate and cache the common expression. We treat it as a temporary,
4834  // even though it's not quite the same thing.
4835  if (!Evaluate(Info.CurrentCall->createTemporary(E->getOpaqueValue(), false),
4836  Info, E->getCommon()))
4837  return false;
4838 
4839  return HandleConditionalOperator(E);
4840  }
4841 
4842  bool VisitConditionalOperator(const ConditionalOperator *E) {
4843  bool IsBcpCall = false;
4844  // If the condition (ignoring parens) is a __builtin_constant_p call,
4845  // the result is a constant expression if it can be folded without
4846  // side-effects. This is an important GNU extension. See GCC PR38377
4847  // for discussion.
4848  if (const CallExpr *CallCE =
4849  dyn_cast<CallExpr>(E->getCond()->IgnoreParenCasts()))
4850  if (CallCE->getBuiltinCallee() == Builtin::BI__builtin_constant_p)
4851  IsBcpCall = true;
4852 
4853  // Always assume __builtin_constant_p(...) ? ... : ... is a potential
4854  // constant expression; we can't check whether it's potentially foldable.
4855  if (Info.checkingPotentialConstantExpression() && IsBcpCall)
4856  return false;
4857 
4858  FoldConstant Fold(Info, IsBcpCall);
4859  if (!HandleConditionalOperator(E)) {
4860  Fold.keepDiagnostics();
4861  return false;
4862  }
4863 
4864  return true;
4865  }
4866 
4867  bool VisitOpaqueValueExpr(const OpaqueValueExpr *E) {
4868  if (APValue *Value = Info.CurrentCall->getCurrentTemporary(E))
4869  return DerivedSuccess(*Value, E);
4870 
4871  const Expr *Source = E->getSourceExpr();
4872  if (!Source)
4873  return Error(E);
4874  if (Source == E) { // sanity checking.
4875  assert(0 && "OpaqueValueExpr recursively refers to itself");
4876  return Error(E);
4877  }
4878  return StmtVisitorTy::Visit(Source);
4879  }
4880 
4881  bool VisitCallExpr(const CallExpr *E) {
4882  APValue Result;
4883  if (!handleCallExpr(E, Result, nullptr))
4884  return false;
4885  return DerivedSuccess(Result, E);
4886  }
4887 
4888  bool handleCallExpr(const CallExpr *E, APValue &Result,
4889  const LValue *ResultSlot) {
4890  const Expr *Callee = E->getCallee()->IgnoreParens();
4891  QualType CalleeType = Callee->getType();
4892 
4893  const FunctionDecl *FD = nullptr;
4894  LValue *This = nullptr, ThisVal;
4895  auto Args = llvm::makeArrayRef(E->getArgs(), E->getNumArgs());
4896  bool HasQualifier = false;
4897 
4898  // Extract function decl and 'this' pointer from the callee.
4899  if (CalleeType->isSpecificBuiltinType(BuiltinType::BoundMember)) {
4900  const ValueDecl *Member = nullptr;
4901  if (const MemberExpr *ME = dyn_cast<MemberExpr>(Callee)) {
4902  // Explicit bound member calls, such as x.f() or p->g();
4903  if (!EvaluateObjectArgument(Info, ME->getBase(), ThisVal))
4904  return false;
4905  Member = ME->getMemberDecl();
4906  This = &ThisVal;
4907  HasQualifier = ME->hasQualifier();
4908  } else if (const BinaryOperator *BE = dyn_cast<BinaryOperator>(Callee)) {
4909  // Indirect bound member calls ('.*' or '->*').
4910  Member = HandleMemberPointerAccess(Info, BE, ThisVal, false);
4911  if (!Member) return false;
4912  This = &ThisVal;
4913  } else
4914  return Error(Callee);
4915 
4916  FD = dyn_cast<FunctionDecl>(Member);
4917  if (!FD)
4918  return Error(Callee);
4919  } else if (CalleeType->isFunctionPointerType()) {
4920  LValue Call;
4921  if (!EvaluatePointer(Callee, Call, Info))
4922  return false;
4923 
4924  if (!Call.getLValueOffset().isZero())
4925  return Error(Callee);
4926  FD = dyn_cast_or_null<FunctionDecl>(
4927  Call.getLValueBase().dyn_cast<const ValueDecl*>());
4928  if (!FD)
4929  return Error(Callee);
4930  // Don't call function pointers which have been cast to some other type.
4931  // Per DR (no number yet), the caller and callee can differ in noexcept.
4932  if (!Info.Ctx.hasSameFunctionTypeIgnoringExceptionSpec(
4933  CalleeType->getPointeeType(), FD->getType())) {
4934  return Error(E);
4935  }
4936 
4937  // Overloaded operator calls to member functions are represented as normal
4938  // calls with '*this' as the first argument.
4939  const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD);
4940  if (MD && !MD->isStatic()) {
4941  // FIXME: When selecting an implicit conversion for an overloaded
4942  // operator delete, we sometimes try to evaluate calls to conversion
4943  // operators without a 'this' parameter!
4944  if (Args.empty())
4945  return Error(E);
4946 
4947  if (!EvaluateObjectArgument(Info, Args[0], ThisVal))
4948  return false;
4949  This = &ThisVal;
4950  Args = Args.slice(1);
4951  } else if (MD && MD->isLambdaStaticInvoker()) {
4952  // Map the static invoker for the lambda back to the call operator.
4953  // Conveniently, we don't have to slice out the 'this' argument (as is
4954  // being done for the non-static case), since a static member function
4955  // doesn't have an implicit argument passed in.
4956  const CXXRecordDecl *ClosureClass = MD->getParent();
4957  assert(
4958  ClosureClass->captures_begin() == ClosureClass->captures_end() &&
4959  "Number of captures must be zero for conversion to function-ptr");
4960 
4961  const CXXMethodDecl *LambdaCallOp =
4962  ClosureClass->getLambdaCallOperator();
4963 
4964  // Set 'FD', the function that will be called below, to the call
4965  // operator. If the closure object represents a generic lambda, find
4966  // the corresponding specialization of the call operator.
4967 
4968  if (ClosureClass->isGenericLambda()) {
4969  assert(MD->isFunctionTemplateSpecialization() &&
4970  "A generic lambda's static-invoker function must be a "
4971  "template specialization");
4973  FunctionTemplateDecl *CallOpTemplate =
4974  LambdaCallOp->getDescribedFunctionTemplate();
4975  void *InsertPos = nullptr;
4976  FunctionDecl *CorrespondingCallOpSpecialization =
4977  CallOpTemplate->findSpecialization(TAL->asArray(), InsertPos);
4978  assert(CorrespondingCallOpSpecialization &&
4979  "We must always have a function call operator specialization "
4980  "that corresponds to our static invoker specialization");
4981  FD = cast<CXXMethodDecl>(CorrespondingCallOpSpecialization);
4982  } else
4983  FD = LambdaCallOp;
4984  }
4985 
4986 
4987  } else
4988  return Error(E);
4989 
4990  if (This && !This->checkSubobject(Info, E, CSK_This))
4991  return false;
4992 
4993  // DR1358 allows virtual constexpr functions in some cases. Don't allow
4994  // calls to such functions in constant expressions.
4995  if (This && !HasQualifier &&
4996  isa<CXXMethodDecl>(FD) && cast<CXXMethodDecl>(FD)->isVirtual())
4997  return Error(E, diag::note_constexpr_virtual_call);
4998 
4999  const FunctionDecl *Definition = nullptr;
5000  Stmt *Body = FD->getBody(Definition);
5001 
5002  if (!CheckConstexprFunction(Info, E->getExprLoc(), FD, Definition, Body) ||
5003  !HandleFunctionCall(E->getExprLoc(), Definition, This, Args, Body, Info,
5004  Result, ResultSlot))
5005  return false;
5006 
5007  return true;
5008  }
5009 
5010  bool VisitCompoundLiteralExpr(const CompoundLiteralExpr *E) {
5011  return StmtVisitorTy::Visit(E->getInitializer());
5012  }
5013  bool VisitInitListExpr(const InitListExpr *E) {
5014  if (E->getNumInits() == 0)
5015  return DerivedZeroInitialization(E);
5016  if (E->getNumInits() == 1)
5017  return StmtVisitorTy::Visit(E->getInit(0));
5018  return Error(E);
5019  }
5020  bool VisitImplicitValueInitExpr(const ImplicitValueInitExpr *E) {
5021  return DerivedZeroInitialization(E);
5022  }
5023  bool VisitCXXScalarValueInitExpr(const CXXScalarValueInitExpr *E) {
5024  return DerivedZeroInitialization(E);
5025  }
5026  bool VisitCXXNullPtrLiteralExpr(const CXXNullPtrLiteralExpr *E) {
5027  return DerivedZeroInitialization(E);
5028  }
5029 
5030  /// A member expression where the object is a prvalue is itself a prvalue.
5031  bool VisitMemberExpr(const MemberExpr *E) {
5032  assert(!E->isArrow() && "missing call to bound member function?");
5033 
5034  APValue Val;
5035  if (!Evaluate(Val, Info, E->getBase()))
5036  return false;
5037 
5038  QualType BaseTy = E->getBase()->getType();
5039 
5040  const FieldDecl *FD = dyn_cast<FieldDecl>(E->getMemberDecl());
5041  if (!FD) return Error(E);
5042  assert(!FD->getType()->isReferenceType() && "prvalue reference?");
5043  assert(BaseTy->castAs<RecordType>()->getDecl()->getCanonicalDecl() ==
5044  FD->getParent()->getCanonicalDecl() && "record / field mismatch");
5045 
5046  CompleteObject Obj(&Val, BaseTy, true);
5047  SubobjectDesignator Designator(BaseTy);
5048  Designator.addDeclUnchecked(FD);
5049 
5050  APValue Result;
5051  return extractSubobject(Info, E, Obj, Designator, Result) &&
5052  DerivedSuccess(Result, E);
5053  }
5054 
5055  bool VisitCastExpr(const CastExpr *E) {
5056  switch (E->getCastKind()) {
5057  default:
5058  break;
5059 
5060  case CK_AtomicToNonAtomic: {
5061  APValue AtomicVal;
5062  // This does not need to be done in place even for class/array types:
5063  // atomic-to-non-atomic conversion implies copying the object
5064  // representation.
5065  if (!Evaluate(AtomicVal, Info, E->getSubExpr()))
5066  return false;
5067  return DerivedSuccess(AtomicVal, E);
5068  }
5069 
5070  case CK_NoOp:
5071  case CK_UserDefinedConversion:
5072  return StmtVisitorTy::Visit(E->getSubExpr());
5073 
5074  case CK_LValueToRValue: {
5075  LValue LVal;
5076  if (!EvaluateLValue(E->getSubExpr(), LVal, Info))
5077  return false;
5078  APValue RVal;
5079  // Note, we use the subexpression's type in order to retain cv-qualifiers.
5080  if (!handleLValueToRValueConversion(Info, E, E->getSubExpr()->getType(),
5081  LVal, RVal))
5082  return false;
5083  return DerivedSuccess(RVal, E);
5084  }
5085  }
5086 
5087  return Error(E);
5088  }
5089 
5090  bool VisitUnaryPostInc(const UnaryOperator *UO) {
5091  return VisitUnaryPostIncDec(UO);
5092  }
5093  bool VisitUnaryPostDec(const UnaryOperator *UO) {
5094  return VisitUnaryPostIncDec(UO);
5095  }
5096  bool VisitUnaryPostIncDec(const UnaryOperator *UO) {
5097  if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
5098  return Error(UO);
5099 
5100  LValue LVal;
5101  if (!EvaluateLValue(UO->getSubExpr(), LVal, Info))
5102  return false;
5103  APValue RVal;
5104  if (!handleIncDec(this->Info, UO, LVal, UO->getSubExpr()->getType(),
5105  UO->isIncrementOp(), &RVal))
5106  return false;
5107  return DerivedSuccess(RVal, UO);
5108  }
5109 
5110  bool VisitStmtExpr(const StmtExpr *E) {
5111  // We will have checked the full-expressions inside the statement expression
5112  // when they were completed, and don't need to check them again now.
5113  if (Info.checkingForOverflow())
5114  return Error(E);
5115 
5116  BlockScopeRAII Scope(Info);
5117  const CompoundStmt *CS = E->getSubStmt();
5118  if (CS->body_empty())
5119  return true;
5120 
5122  BE = CS->body_end();
5123  /**/; ++BI) {
5124  if (BI + 1 == BE) {
5125  const Expr *FinalExpr = dyn_cast<Expr>(*BI);
5126  if (!FinalExpr) {
5127  Info.FFDiag((*BI)->getBeginLoc(),
5128  diag::note_constexpr_stmt_expr_unsupported);
5129  return false;
5130  }
5131  return this->Visit(FinalExpr);
5132  }
5133 
5134  APValue ReturnValue;
5135  StmtResult Result = { ReturnValue, nullptr };
5136  EvalStmtResult ESR = EvaluateStmt(Result, Info, *BI);
5137  if (ESR != ESR_Succeeded) {
5138  // FIXME: If the statement-expression terminated due to 'return',
5139  // 'break', or 'continue', it would be nice to propagate that to
5140  // the outer statement evaluation rather than bailing out.
5141  if (ESR != ESR_Failed)
5142  Info.FFDiag((*BI)->getBeginLoc(),
5143  diag::note_constexpr_stmt_expr_unsupported);
5144  return false;
5145  }
5146  }
5147 
5148  llvm_unreachable("Return from function from the loop above.");
5149  }
5150 
5151  /// Visit a value which is evaluated, but whose value is ignored.
5152  void VisitIgnoredValue(const Expr *E) {
5153  EvaluateIgnoredValue(Info, E);
5154  }
5155 
5156  /// Potentially visit a MemberExpr's base expression.
5157  void VisitIgnoredBaseExpression(const Expr *E) {
5158  // While MSVC doesn't evaluate the base expression, it does diagnose the
5159  // presence of side-effecting behavior.
5160  if (Info.getLangOpts().MSVCCompat && !E->HasSideEffects(Info.Ctx))
5161  return;
5162  VisitIgnoredValue(E);
5163  }
5164 };
5165 
5166 } // namespace
5167 
5168 //===----------------------------------------------------------------------===//
5169 // Common base class for lvalue and temporary evaluation.
5170 //===----------------------------------------------------------------------===//
5171 namespace {
5172 template<class Derived>
5173 class LValueExprEvaluatorBase
5174  : public ExprEvaluatorBase<Derived> {
5175 protected:
5176  LValue &Result;
5177  bool InvalidBaseOK;
5178  typedef LValueExprEvaluatorBase LValueExprEvaluatorBaseTy;
5179  typedef ExprEvaluatorBase<Derived> ExprEvaluatorBaseTy;
5180 
5181  bool Success(APValue::LValueBase B) {
5182  Result.set(B);
5183  return true;
5184  }
5185 
5186  bool evaluatePointer(const Expr *E, LValue &Result) {
5187  return EvaluatePointer(E, Result, this->Info, InvalidBaseOK);
5188  }
5189 
5190 public:
5191  LValueExprEvaluatorBase(EvalInfo &Info, LValue &Result, bool InvalidBaseOK)
5192  : ExprEvaluatorBaseTy(Info), Result(Result),
5193  InvalidBaseOK(InvalidBaseOK) {}
5194 
5195  bool Success(const APValue &V, const Expr *E) {
5196  Result.setFrom(this->Info.Ctx, V);
5197  return true;
5198  }
5199 
5200  bool VisitMemberExpr(const MemberExpr *E) {
5201  // Handle non-static data members.
5202  QualType BaseTy;
5203  bool EvalOK;
5204  if (E->isArrow()) {
5205  EvalOK = evaluatePointer(E->getBase(), Result);
5206  BaseTy = E->getBase()->getType()->castAs<PointerType>()->getPointeeType();
5207  } else if (E->getBase()->isRValue()) {
5208  assert(E->getBase()->getType()->isRecordType());
5209  EvalOK = EvaluateTemporary(E->getBase(), Result, this->Info);
5210  BaseTy = E->getBase()->getType();
5211  } else {
5212  EvalOK = this->Visit(E->getBase());
5213  BaseTy = E->getBase()->getType();
5214  }
5215  if (!EvalOK) {
5216  if (!InvalidBaseOK)
5217  return false;
5218  Result.setInvalid(E);
5219  return true;
5220  }
5221 
5222  const ValueDecl *MD = E->getMemberDecl();
5223  if (const FieldDecl *FD = dyn_cast<FieldDecl>(E->getMemberDecl())) {
5224  assert(BaseTy->getAs<RecordType>()->getDecl()->getCanonicalDecl() ==
5225  FD->getParent()->getCanonicalDecl() && "record / field mismatch");
5226  (void)BaseTy;
5227  if (!HandleLValueMember(this->Info, E, Result, FD))
5228  return false;
5229  } else if (const IndirectFieldDecl *IFD = dyn_cast<IndirectFieldDecl>(MD)) {
5230  if (!HandleLValueIndirectMember(this->Info, E, Result, IFD))
5231  return false;
5232  } else
5233  return this->Error(E);
5234 
5235  if (MD->getType()->isReferenceType()) {
5236  APValue RefValue;
5237  if (!handleLValueToRValueConversion(this->Info, E, MD->getType(), Result,
5238  RefValue))
5239  return false;
5240  return Success(RefValue, E);
5241  }
5242  return true;
5243  }
5244 
5245  bool VisitBinaryOperator(const BinaryOperator *E) {
5246  switch (E->getOpcode()) {
5247  default:
5248  return ExprEvaluatorBaseTy::VisitBinaryOperator(E);
5249 
5250  case BO_PtrMemD:
5251  case BO_PtrMemI:
5252  return HandleMemberPointerAccess(this->Info, E, Result);
5253  }
5254  }
5255 
5256  bool VisitCastExpr(const CastExpr *E) {
5257  switch (E->getCastKind()) {
5258  default:
5259  return ExprEvaluatorBaseTy::VisitCastExpr(E);
5260 
5261  case CK_DerivedToBase:
5262  case CK_UncheckedDerivedToBase:
5263  if (!this->Visit(E->getSubExpr()))
5264  return false;
5265 
5266  // Now figure out the necessary offset to add to the base LV to get from
5267  // the derived class to the base class.
5268  return HandleLValueBasePath(this->Info, E, E->getSubExpr()->getType(),
5269  Result);
5270  }
5271  }
5272 };
5273 }
5274 
5275 //===----------------------------------------------------------------------===//
5276 // LValue Evaluation
5277 //
5278 // This is used for evaluating lvalues (in C and C++), xvalues (in C++11),
5279 // function designators (in C), decl references to void objects (in C), and
5280 // temporaries (if building with -Wno-address-of-temporary).
5281 //
5282 // LValue evaluation produces values comprising a base expression of one of the
5283 // following types:
5284 // - Declarations
5285 // * VarDecl
5286 // * FunctionDecl
5287 // - Literals
5288 // * CompoundLiteralExpr in C (and in global scope in C++)
5289 // * StringLiteral
5290 // * CXXTypeidExpr
5291 // * PredefinedExpr
5292 // * ObjCStringLiteralExpr
5293 // * ObjCEncodeExpr
5294 // * AddrLabelExpr
5295 // * BlockExpr
5296 // * CallExpr for a MakeStringConstant builtin
5297 // - Locals and temporaries
5298 // * MaterializeTemporaryExpr
5299 // * Any Expr, with a CallIndex indicating the function in which the temporary
5300 // was evaluated, for cases where the MaterializeTemporaryExpr is missing
5301 // from the AST (FIXME).
5302 // * A MaterializeTemporaryExpr that has static storage duration, with no
5303 // CallIndex, for a lifetime-extended temporary.
5304 // plus an offset in bytes.
5305 //===----------------------------------------------------------------------===//
5306 namespace {
5307 class LValueExprEvaluator
5308  : public LValueExprEvaluatorBase<LValueExprEvaluator> {
5309 public:
5310  LValueExprEvaluator(EvalInfo &Info, LValue &Result, bool InvalidBaseOK) :
5311  LValueExprEvaluatorBaseTy(Info, Result, InvalidBaseOK) {}
5312 
5313  bool VisitVarDecl(const Expr *E, const VarDecl *VD);
5314  bool VisitUnaryPreIncDec(const UnaryOperator *UO);
5315 
5316  bool VisitDeclRefExpr(const DeclRefExpr *E);
5317  bool VisitPredefinedExpr(const PredefinedExpr *E) { return Success(E); }
5318  bool VisitMaterializeTemporaryExpr(const MaterializeTemporaryExpr *E);
5319  bool VisitCompoundLiteralExpr(const CompoundLiteralExpr *E);
5320  bool VisitMemberExpr(const MemberExpr *E);
5321  bool VisitStringLiteral(const StringLiteral *E) { return Success(E); }
5322  bool VisitObjCEncodeExpr(const ObjCEncodeExpr *E) { return Success(E); }
5323  bool VisitCXXTypeidExpr(const CXXTypeidExpr *E);
5324  bool VisitCXXUuidofExpr(const CXXUuidofExpr *E);
5325  bool VisitArraySubscriptExpr(const ArraySubscriptExpr *E);
5326  bool VisitUnaryDeref(const UnaryOperator *E);
5327  bool VisitUnaryReal(const UnaryOperator *E);
5328  bool VisitUnaryImag(const UnaryOperator *E);
5329  bool VisitUnaryPreInc(const UnaryOperator *UO) {
5330  return VisitUnaryPreIncDec(UO);
5331  }
5332  bool VisitUnaryPreDec(const UnaryOperator *UO) {
5333  return VisitUnaryPreIncDec(UO);
5334  }
5335  bool VisitBinAssign(const BinaryOperator *BO);
5336  bool VisitCompoundAssignOperator(const CompoundAssignOperator *CAO);
5337 
5338  bool VisitCastExpr(const CastExpr *E) {
5339  switch (E->getCastKind()) {
5340  default:
5341  return LValueExprEvaluatorBaseTy::VisitCastExpr(E);
5342 
5343  case CK_LValueBitCast:
5344  this->CCEDiag(E, diag::note_constexpr_invalid_cast) << 2;
5345  if (!Visit(E->getSubExpr()))
5346  return false;
5347  Result.Designator.setInvalid();
5348  return true;
5349 
5350  case CK_BaseToDerived:
5351  if (!Visit(E->getSubExpr()))
5352  return false;
5353  return HandleBaseToDerivedCast(Info, E, Result);
5354  }
5355  }
5356 };
5357 } // end anonymous namespace
5358 
5359 /// Evaluate an expression as an lvalue. This can be legitimately called on
5360 /// expressions which are not glvalues, in three cases:
5361 /// * function designators in C, and
5362 /// * "extern void" objects
5363 /// * @selector() expressions in Objective-C
5364 static bool EvaluateLValue(const Expr *E, LValue &Result, EvalInfo &Info,
5365  bool InvalidBaseOK) {
5366  assert(E->isGLValue() || E->getType()->isFunctionType() ||
5367  E->getType()->isVoidType() || isa<ObjCSelectorExpr>(E));
5368  return LValueExprEvaluator(Info, Result, InvalidBaseOK).Visit(E);
5369 }
5370 
5371 bool LValueExprEvaluator::VisitDeclRefExpr(const DeclRefExpr *E) {
5372  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(E->getDecl()))
5373  return Success(FD);
5374  if (const VarDecl *VD = dyn_cast<VarDecl>(E->getDecl()))
5375  return VisitVarDecl(E, VD);
5376  if (const BindingDecl *BD = dyn_cast<BindingDecl>(E->getDecl()))
5377  return Visit(BD->getBinding());
5378  return Error(E);
5379 }
5380 
5381 
5382 bool LValueExprEvaluator::VisitVarDecl(const Expr *E, const VarDecl *VD) {
5383 
5384  // If we are within a lambda's call operator, check whether the 'VD' referred
5385  // to within 'E' actually represents a lambda-capture that maps to a
5386  // data-member/field within the closure object, and if so, evaluate to the
5387  // field or what the field refers to.
5388  if (Info.CurrentCall && isLambdaCallOperator(Info.CurrentCall->Callee) &&
5389  isa<DeclRefExpr>(E) &&
5390  cast<DeclRefExpr>(E)->refersToEnclosingVariableOrCapture()) {
5391  // We don't always have a complete capture-map when checking or inferring if
5392  // the function call operator meets the requirements of a constexpr function
5393  // - but we don't need to evaluate the captures to determine constexprness
5394  // (dcl.constexpr C++17).
5395  if (Info.checkingPotentialConstantExpression())
5396  return false;
5397 
5398  if (auto *FD = Info.CurrentCall->LambdaCaptureFields.lookup(VD)) {
5399  // Start with 'Result' referring to the complete closure object...
5400  Result = *Info.CurrentCall->This;
5401  // ... then update it to refer to the field of the closure object
5402  // that represents the capture.
5403  if (!HandleLValueMember(Info, E, Result, FD))
5404  return false;
5405  // And if the field is of reference type, update 'Result' to refer to what
5406  // the field refers to.
5407  if (FD->getType()->isReferenceType()) {
5408  APValue RVal;
5409  if (!handleLValueToRValueConversion(Info, E, FD->getType(), Result,
5410  RVal))
5411  return false;
5412  Result.setFrom(Info.Ctx, RVal);
5413  }
5414  return true;
5415  }
5416  }
5417  CallStackFrame *Frame = nullptr;
5418  if (VD->hasLocalStorage() && Info.CurrentCall->Index > 1) {
5419  // Only if a local variable was declared in the function currently being
5420  // evaluated, do we expect to be able to find its value in the current
5421  // frame. (Otherwise it was likely declared in an enclosing context and
5422  // could either have a valid evaluatable value (for e.g. a constexpr
5423  // variable) or be ill-formed (and trigger an appropriate evaluation
5424  // diagnostic)).
5425  if (Info.CurrentCall->Callee &&
5426  Info.CurrentCall->Callee->Equals(VD->getDeclContext())) {
5427  Frame = Info.CurrentCall;
5428  }
5429  }
5430 
5431  if (!VD->getType()->isReferenceType()) {
5432  if (Frame) {
5433  Result.set({VD, Frame->Index,
5434  Info.CurrentCall->getCurrentTemporaryVersion(VD)});
5435  return true;
5436  }
5437  return Success(VD);
5438  }
5439 
5440  APValue *V;
5441  if (!evaluateVarDeclInit(Info, E, VD, Frame, V, nullptr))
5442  return false;
5443  if (V->isUninit()) {
5444  if (!Info.checkingPotentialConstantExpression())
5445  Info.FFDiag(E, diag::note_constexpr_use_uninit_reference);
5446  return false;
5447  }
5448  return Success(*V, E);
5449 }
5450 
5451 bool LValueExprEvaluator::VisitMaterializeTemporaryExpr(
5452  const MaterializeTemporaryExpr *E) {
5453  // Walk through the expression to find the materialized temporary itself.
5454  SmallVector<const Expr *, 2> CommaLHSs;
5456  const Expr *Inner = E->GetTemporaryExpr()->
5457  skipRValueSubobjectAdjustments(CommaLHSs, Adjustments);
5458 
5459  // If we passed any comma operators, evaluate their LHSs.
5460  for (unsigned I = 0, N = CommaLHSs.size(); I != N; ++I)
5461  if (!EvaluateIgnoredValue(Info, CommaLHSs[I]))
5462  return false;
5463 
5464  // A materialized temporary with static storage duration can appear within the
5465  // result of a constant expression evaluation, so we need to preserve its
5466  // value for use outside this evaluation.
5467  APValue *Value;
5468  if (E->getStorageDuration() == SD_Static) {
5469  Value = Info.Ctx.getMaterializedTemporaryValue(E, true);
5470  *Value = APValue();
5471  Result.set(E);
5472  } else {
5474  *Info.CurrentCall);
5475  }
5476 
5477  QualType Type = Inner->getType();
5478 
5479  // Materialize the temporary itself.
5480  if (!EvaluateInPlace(*Value, Info, Result, Inner) ||
5481  (E->getStorageDuration() == SD_Static &&
5482  !CheckConstantExpression(Info, E->getExprLoc(), Type, *Value))) {
5483  *Value = APValue();
5484  return false;
5485  }
5486 
5487  // Adjust our lvalue to refer to the desired subobject.
5488  for (unsigned I = Adjustments.size(); I != 0; /**/) {
5489  --I;
5490  switch (Adjustments[I].Kind) {
5492  if (!HandleLValueBasePath(Info, Adjustments[I].DerivedToBase.BasePath,
5493  Type, Result))
5494  return false;
5495  Type = Adjustments[I].DerivedToBase.BasePath->getType();
5496  break;
5497 
5499  if (!HandleLValueMember(Info, E, Result, Adjustments[I].Field))
5500  return false;
5501  Type = Adjustments[I].Field->getType();
5502  break;
5503 
5505  if (!HandleMemberPointerAccess(this->Info, Type, Result,
5506  Adjustments[I].Ptr.RHS))
5507  return false;
5508  Type = Adjustments[I].Ptr.MPT->getPointeeType();
5509  break;
5510  }
5511  }
5512 
5513  return true;
5514 }
5515 
5516 bool
5517 LValueExprEvaluator::VisitCompoundLiteralExpr(const CompoundLiteralExpr *E) {
5518  assert((!Info.getLangOpts().CPlusPlus || E->isFileScope()) &&
5519  "lvalue compound literal in c++?");
5520  // Defer visiting the literal until the lvalue-to-rvalue conversion. We can
5521  // only see this when folding in C, so there's no standard to follow here.
5522  return Success(E);
5523 }
5524 
5525 bool LValueExprEvaluator::VisitCXXTypeidExpr(const CXXTypeidExpr *E) {
5526  if (!E->isPotentiallyEvaluated())
5527  return Success(E);
5528 
5529  Info.FFDiag(E, diag::note_constexpr_typeid_polymorphic)
5530  << E->getExprOperand()->getType()
5531  << E->getExprOperand()->getSourceRange();
5532  return false;
5533 }
5534 
5535 bool LValueExprEvaluator::VisitCXXUuidofExpr(const CXXUuidofExpr *E) {
5536  return Success(E);
5537 }
5538 
5539 bool LValueExprEvaluator::VisitMemberExpr(const MemberExpr *E) {
5540  // Handle static data members.
5541  if (const VarDecl *VD = dyn_cast<VarDecl>(E->getMemberDecl())) {
5542  VisitIgnoredBaseExpression(E->getBase());
5543  return VisitVarDecl(E, VD);
5544  }
5545 
5546  // Handle static member functions.
5547  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(E->getMemberDecl())) {
5548  if (MD->isStatic()) {
5549  VisitIgnoredBaseExpression(E->getBase());
5550  return Success(MD);
5551  }
5552  }
5553 
5554  // Handle non-static data members.
5555  return LValueExprEvaluatorBaseTy::VisitMemberExpr(E);
5556 }
5557 
5558 bool LValueExprEvaluator::VisitArraySubscriptExpr(const ArraySubscriptExpr *E) {
5559  // FIXME: Deal with vectors as array subscript bases.
5560  if (E->getBase()->getType()->isVectorType())
5561  return Error(E);
5562 
5563  bool Success = true;
5564  if (!evaluatePointer(E->getBase(), Result)) {
5565  if (!Info.noteFailure())
5566  return false;
5567  Success = false;
5568  }
5569 
5570  APSInt Index;
5571  if (!EvaluateInteger(E->getIdx(), Index, Info))
5572  return false;
5573 
5574  return Success &&
5575  HandleLValueArrayAdjustment(Info, E, Result, E->getType(), Index);
5576 }
5577 
5578 bool LValueExprEvaluator::VisitUnaryDeref(const UnaryOperator *E) {
5579  return evaluatePointer(E->getSubExpr(), Result);
5580 }
5581 
5582 bool LValueExprEvaluator::VisitUnaryReal(const UnaryOperator *E) {
5583  if (!Visit(E->getSubExpr()))
5584  return false;
5585  // __real is a no-op on scalar lvalues.
5586  if (E->getSubExpr()->getType()->isAnyComplexType())
5587  HandleLValueComplexElement(Info, E, Result, E->getType(), false);
5588  return true;
5589 }
5590 
5591 bool LValueExprEvaluator::VisitUnaryImag(const UnaryOperator *E) {
5592  assert(E->getSubExpr()->getType()->isAnyComplexType() &&
5593  "lvalue __imag__ on scalar?");
5594  if (!Visit(E->getSubExpr()))
5595  return false;
5596  HandleLValueComplexElement(Info, E, Result, E->getType(), true);
5597  return true;
5598 }
5599 
5600 bool LValueExprEvaluator::VisitUnaryPreIncDec(const UnaryOperator *UO) {
5601  if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
5602  return Error(UO);
5603 
5604  if (!this->Visit(UO->getSubExpr()))
5605  return false;
5606 
5607  return handleIncDec(
5608  this->Info, UO, Result, UO->getSubExpr()->getType(),
5609  UO->isIncrementOp(), nullptr);
5610 }
5611 
5612 bool LValueExprEvaluator::VisitCompoundAssignOperator(
5613  const CompoundAssignOperator *CAO) {
5614  if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
5615  return Error(CAO);
5616 
5617  APValue RHS;
5618 
5619  // The overall lvalue result is the result of evaluating the LHS.
5620  if (!this->Visit(CAO->getLHS())) {
5621  if (Info.noteFailure())
5622  Evaluate(RHS, this->Info, CAO->getRHS());
5623  return false;
5624  }
5625 
5626  if (!Evaluate(RHS, this->Info, CAO->getRHS()))
5627  return false;
5628 
5629  return handleCompoundAssignment(
5630  this->Info, CAO,
5631  Result, CAO->getLHS()->getType(), CAO->getComputationLHSType(),
5632  CAO->getOpForCompoundAssignment(CAO->getOpcode()), RHS);
5633 }
5634 
5635 bool LValueExprEvaluator::VisitBinAssign(const BinaryOperator *E) {
5636  if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
5637  return Error(E);
5638 
5639  APValue NewVal;
5640 
5641  if (!this->Visit(E->getLHS())) {
5642  if (Info.noteFailure())
5643  Evaluate(NewVal, this->Info, E->getRHS());
5644  return false;
5645  }
5646 
5647  if (!Evaluate(NewVal, this->Info, E->getRHS()))
5648  return false;
5649 
5650  return handleAssignment(this->Info, E, Result, E->getLHS()->getType(),
5651  NewVal);
5652 }
5653 
5654 //===----------------------------------------------------------------------===//
5655 // Pointer Evaluation
5656 //===----------------------------------------------------------------------===//
5657 
5658 /// Attempts to compute the number of bytes available at the pointer
5659 /// returned by a function with the alloc_size attribute. Returns true if we
5660 /// were successful. Places an unsigned number into `Result`.
5661 ///
5662 /// This expects the given CallExpr to be a call to a function with an
5663 /// alloc_size attribute.
5665  const CallExpr *Call,
5666  llvm::APInt &Result) {
5667  const AllocSizeAttr *AllocSize = getAllocSizeAttr(Call);
5668 
5669  assert(AllocSize && AllocSize->getElemSizeParam().isValid());
5670  unsigned SizeArgNo = AllocSize->getElemSizeParam().getASTIndex();
5671  unsigned BitsInSizeT = Ctx.getTypeSize(Ctx.getSizeType());
5672  if (Call->getNumArgs() <= SizeArgNo)
5673  return false;
5674 
5675  auto EvaluateAsSizeT = [&](const Expr *E, APSInt &Into) {
5677  if (!E->EvaluateAsInt(ExprResult, Ctx, Expr::SE_AllowSideEffects))
5678  return false;
5679  Into = ExprResult.Val.getInt();
5680  if (Into.isNegative() || !Into.isIntN(BitsInSizeT))
5681  return false;
5682  Into = Into.zextOrSelf(BitsInSizeT);
5683  return true;
5684  };
5685 
5686  APSInt SizeOfElem;
5687  if (!EvaluateAsSizeT(Call->getArg(SizeArgNo), SizeOfElem))
5688  return false;
5689 
5690  if (!AllocSize->getNumElemsParam().isValid()) {
5691  Result = std::move(SizeOfElem);
5692  return true;
5693  }
5694 
5695  APSInt NumberOfElems;
5696  unsigned NumArgNo = AllocSize->getNumElemsParam().getASTIndex();
5697  if (!EvaluateAsSizeT(Call->getArg(NumArgNo), NumberOfElems))
5698  return false;
5699 
5700  bool Overflow;
5701  llvm::APInt BytesAvailable = SizeOfElem.umul_ov(NumberOfElems, Overflow);
5702  if (Overflow)
5703  return false;
5704 
5705  Result = std::move(BytesAvailable);
5706  return true;
5707 }
5708 
5709 /// Convenience function. LVal's base must be a call to an alloc_size
5710 /// function.
5712  const LValue &LVal,
5713  llvm::APInt &Result) {
5714  assert(isBaseAnAllocSizeCall(LVal.getLValueBase()) &&
5715  "Can't get the size of a non alloc_size function");
5716  const auto *Base = LVal.getLValueBase().get<const Expr *>();
5717  const CallExpr *CE = tryUnwrapAllocSizeCall(Base);
5718  return getBytesReturnedByAllocSizeCall(Ctx, CE, Result);
5719 }
5720 
5721 /// Attempts to evaluate the given LValueBase as the result of a call to
5722 /// a function with the alloc_size attribute. If it was possible to do so, this
5723 /// function will return true, make Result's Base point to said function call,
5724 /// and mark Result's Base as invalid.
5725 static bool evaluateLValueAsAllocSize(EvalInfo &Info, APValue::LValueBase Base,
5726  LValue &Result) {
5727  if (Base.isNull())
5728  return false;
5729 
5730  // Because we do no form of static analysis, we only support const variables.
5731  //
5732  // Additionally, we can't support parameters, nor can we support static
5733  // variables (in the latter case, use-before-assign isn't UB; in the former,
5734  // we have no clue what they'll be assigned to).
5735  const auto *VD =
5736  dyn_cast_or_null<VarDecl>(Base.dyn_cast<const ValueDecl *>());
5737  if (!VD || !VD->isLocalVarDecl() || !VD->getType().isConstQualified())
5738  return false;
5739 
5740  const Expr *Init = VD->getAnyInitializer();
5741  if (!Init)
5742  return false;
5743 
5744  const Expr *E = Init->IgnoreParens();
5745  if (!tryUnwrapAllocSizeCall(E))
5746  return false;
5747 
5748  // Store E instead of E unwrapped so that the type of the LValue's base is
5749  // what the user wanted.
5750  Result.setInvalid(E);
5751 
5752  QualType Pointee = E->getType()->castAs<PointerType>()->getPointeeType();
5753  Result.addUnsizedArray(Info, E, Pointee);
5754  return true;
5755 }
5756 
5757 namespace {
5758 class PointerExprEvaluator
5759  : public ExprEvaluatorBase<PointerExprEvaluator> {
5760  LValue &Result;
5761  bool InvalidBaseOK;
5762 
5763  bool Success(const Expr *E) {
5764  Result.set(E);
5765  return true;
5766  }
5767 
5768  bool evaluateLValue(const Expr *E, LValue &Result) {
5769  return EvaluateLValue(E, Result, Info, InvalidBaseOK);
5770  }
5771 
5772  bool evaluatePointer(const Expr *E, LValue &Result) {
5773  return EvaluatePointer(E, Result, Info, InvalidBaseOK);
5774  }
5775 
5776  bool visitNonBuiltinCallExpr(const CallExpr *E);
5777 public:
5778 
5779  PointerExprEvaluator(EvalInfo &info, LValue &Result, bool InvalidBaseOK)
5780  : ExprEvaluatorBaseTy(info), Result(Result),
5781  InvalidBaseOK(InvalidBaseOK) {}
5782 
5783  bool Success(const APValue &V, const Expr *E) {
5784  Result.setFrom(Info.Ctx, V);
5785  return true;
5786  }
5787  bool ZeroInitialization(const Expr *E) {
5788  auto TargetVal = Info.Ctx.getTargetNullPointerValue(E->getType());
5789  Result.setNull(E->getType(), TargetVal);
5790  return true;
5791  }
5792 
5793  bool VisitBinaryOperator(const BinaryOperator *E);
5794  bool VisitCastExpr(const CastExpr* E);
5795  bool VisitUnaryAddrOf(const UnaryOperator *E);
5796  bool VisitObjCStringLiteral(const ObjCStringLiteral *E)
5797  { return Success(E); }
5798  bool VisitObjCBoxedExpr(const ObjCBoxedExpr *E) {
5800  return Success(E);
5801  if (Info.noteFailure())
5802  EvaluateIgnoredValue(Info, E->getSubExpr());
5803  return Error(E);
5804  }
5805  bool VisitAddrLabelExpr(const AddrLabelExpr *E)
5806  { return Success(E); }
5807  bool VisitCallExpr(const CallExpr *E);
5808  bool VisitBuiltinCallExpr(const CallExpr *E, unsigned BuiltinOp);
5809  bool VisitBlockExpr(const BlockExpr *E) {
5810  if (!E->getBlockDecl()->hasCaptures())
5811  return Success(E);
5812  return Error(E);
5813  }
5814  bool VisitCXXThisExpr(const CXXThisExpr *E) {
5815  // Can't look at 'this' when checking a potential constant expression.
5816  if (Info.checkingPotentialConstantExpression())
5817  return false;
5818  if (!Info.CurrentCall->This) {
5819  if (Info.getLangOpts().CPlusPlus11)
5820  Info.FFDiag(E, diag::note_constexpr_this) << E->isImplicit();
5821  else
5822  Info.FFDiag(E);
5823  return false;
5824  }
5825  Result = *Info.CurrentCall->This;
5826  // If we are inside a lambda's call operator, the 'this' expression refers
5827  // to the enclosing '*this' object (either by value or reference) which is
5828  // either copied into the closure object's field that represents the '*this'
5829  // or refers to '*this'.
5830  if (isLambdaCallOperator(Info.CurrentCall->Callee)) {
5831  // Update 'Result' to refer to the data member/field of the closure object
5832  // that represents the '*this' capture.
5833  if (!HandleLValueMember(Info, E, Result,
5834  Info.CurrentCall->LambdaThisCaptureField))
5835  return false;
5836  // If we captured '*this' by reference, replace the field with its referent.
5837  if (Info.CurrentCall->LambdaThisCaptureField->getType()
5838  ->isPointerType()) {
5839  APValue RVal;
5840  if (!handleLValueToRValueConversion(Info, E, E->getType(), Result,
5841  RVal))
5842  return false;
5843 
5844  Result.setFrom(Info.Ctx, RVal);
5845  }
5846  }
5847  return true;
5848  }
5849 
5850  // FIXME: Missing: @protocol, @selector
5851 };
5852 } // end anonymous namespace
5853 
5854 static bool EvaluatePointer(const Expr* E, LValue& Result, EvalInfo &Info,
5855  bool InvalidBaseOK) {
5856  assert(E->isRValue() && E->getType()->hasPointerRepresentation());
5857  return PointerExprEvaluator(Info, Result, InvalidBaseOK).Visit(E);
5858 }
5859 
5860 bool PointerExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
5861  if (E->getOpcode() != BO_Add &&
5862  E->getOpcode() != BO_Sub)
5863  return ExprEvaluatorBaseTy::VisitBinaryOperator(E);
5864 
5865  const Expr *PExp = E->getLHS();
5866  const Expr *IExp = E->getRHS();
5867  if (IExp->getType()->isPointerType())
5868  std::swap(PExp, IExp);
5869 
5870  bool EvalPtrOK = evaluatePointer(PExp, Result);
5871  if (!EvalPtrOK && !Info.noteFailure())
5872  return false;
5873 
5874  llvm::APSInt Offset;
5875  if (!EvaluateInteger(IExp, Offset, Info) || !EvalPtrOK)
5876  return false;
5877 
5878  if (E->getOpcode() == BO_Sub)
5879  negateAsSigned(Offset);
5880 
5881  QualType Pointee = PExp->getType()->castAs<PointerType>()->getPointeeType();
5882  return HandleLValueArrayAdjustment(Info, E, Result, Pointee, Offset);
5883 }
5884 
5885 bool PointerExprEvaluator::VisitUnaryAddrOf(const UnaryOperator *E) {
5886  return evaluateLValue(E->getSubExpr(), Result);
5887 }
5888 
5889 bool PointerExprEvaluator::VisitCastExpr(const CastExpr *E) {
5890  const Expr *SubExpr = E->getSubExpr();
5891 
5892  switch (E->getCastKind()) {
5893  default:
5894  break;
5895 
5896  case CK_BitCast:
5897  case CK_CPointerToObjCPointerCast:
5898  case CK_BlockPointerToObjCPointerCast:
5899  case CK_AnyPointerToBlockPointerCast:
5900  case CK_AddressSpaceConversion:
5901  if (!Visit(SubExpr))
5902  return false;
5903  // Bitcasts to cv void* are static_casts, not reinterpret_casts, so are
5904  // permitted in constant expressions in C++11. Bitcasts from cv void* are
5905  // also static_casts, but we disallow them as a resolution to DR1312.
5906  if (!E->getType()->isVoidPointerType()) {
5907  Result.Designator.setInvalid();
5908  if (SubExpr->getType()->isVoidPointerType())
5909  CCEDiag(E, diag::note_constexpr_invalid_cast)
5910  << 3 << SubExpr->getType();
5911  else
5912  CCEDiag(E, diag::note_constexpr_invalid_cast) << 2;
5913  }
5914  if (E->getCastKind() == CK_AddressSpaceConversion && Result.IsNullPtr)
5915  ZeroInitialization(E);
5916  return true;
5917 
5918  case CK_DerivedToBase:
5919  case CK_UncheckedDerivedToBase:
5920  if (!evaluatePointer(E->getSubExpr(), Result))
5921  return false;
5922  if (!Result.Base && Result.Offset.isZero())
5923  return true;
5924 
5925  // Now figure out the necessary offset to add to the base LV to get from
5926  // the derived class to the base class.
5927  return HandleLValueBasePath(Info, E, E->getSubExpr()->getType()->
5928  castAs<PointerType>()->getPointeeType(),
5929  Result);
5930 
5931  case CK_BaseToDerived:
5932  if (!Visit(E->getSubExpr()))
5933  return false;
5934  if (!Result.Base && Result.Offset.isZero())
5935  return true;
5936  return HandleBaseToDerivedCast(Info, E, Result);
5937 
5938  case CK_NullToPointer:
5939  VisitIgnoredValue(E->getSubExpr());
5940  return ZeroInitialization(E);
5941 
5942  case CK_IntegralToPointer: {
5943  CCEDiag(E, diag::note_constexpr_invalid_cast) << 2;
5944 
5945  APValue Value;
5946  if (!EvaluateIntegerOrLValue(SubExpr, Value, Info))
5947  break;
5948 
5949  if (Value.isInt()) {
5950  unsigned Size = Info.Ctx.getTypeSize(E->getType());
5951  uint64_t N = Value.getInt().extOrTrunc(Size).getZExtValue();
5952  Result.Base = (Expr*)nullptr;
5953  Result.InvalidBase = false;
5954  Result.Offset = CharUnits::fromQuantity(N);
5955  Result.Designator.setInvalid();
5956  Result.IsNullPtr = false;
5957  return true;
5958  } else {
5959  // Cast is of an lvalue, no need to change value.
5960  Result.setFrom(Info.Ctx, Value);
5961  return true;
5962  }
5963  }
5964 
5965  case CK_ArrayToPointerDecay: {
5966  if (SubExpr->isGLValue()) {
5967  if (!evaluateLValue(SubExpr, Result))
5968  return false;
5969  } else {
5970  APValue &Value = createTemporary(SubExpr, false, Result,
5971  *Info.CurrentCall);
5972  if (!EvaluateInPlace(Value, Info, Result, SubExpr))
5973  return false;
5974  }
5975  // The result is a pointer to the first element of the array.
5976  auto *AT = Info.Ctx.getAsArrayType(SubExpr->getType());
5977  if (auto *CAT = dyn_cast<ConstantArrayType>(AT))
5978  Result.addArray(Info, E, CAT);
5979  else
5980  Result.addUnsizedArray(Info, E, AT->getElementType());
5981  return true;
5982  }
5983 
5984  case CK_FunctionToPointerDecay:
5985  return evaluateLValue(SubExpr, Result);
5986 
5987  case CK_LValueToRValue: {
5988  LValue LVal;
5989  if (!evaluateLValue(E->getSubExpr(), LVal))
5990  return false;
5991 
5992  APValue RVal;
5993  // Note, we use t