1 //===--- SemaCast.cpp - Semantic Analysis for Casts -----------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 //  This file implements semantic analysis for cast expressions, including
11 //  1) C-style casts like '(int) x'
12 //  2) C++ functional casts like 'int(x)'
13 //  3) C++ named casts like 'static_cast<int>(x)'
14 //
15 //===----------------------------------------------------------------------===//
16 
17 #include "clang/Sema/SemaInternal.h"
18 #include "clang/AST/ASTContext.h"
19 #include "clang/AST/CXXInheritance.h"
20 #include "clang/AST/ExprCXX.h"
21 #include "clang/AST/ExprObjC.h"
22 #include "clang/AST/RecordLayout.h"
23 #include "clang/Basic/PartialDiagnostic.h"
24 #include "clang/Basic/TargetInfo.h"
25 #include "clang/Sema/Initialization.h"
26 #include "llvm/ADT/SmallVector.h"
27 #include <set>
28 using namespace clang;
29 
30 
31 
32 enum TryCastResult {
33   TC_NotApplicable, ///< The cast method is not applicable.
34   TC_Success,       ///< The cast method is appropriate and successful.
35   TC_Failed         ///< The cast method is appropriate, but failed. A
36                     ///< diagnostic has been emitted.
37 };
38 
39 enum CastType {
40   CT_Const,       ///< const_cast
41   CT_Static,      ///< static_cast
42   CT_Reinterpret, ///< reinterpret_cast
43   CT_Dynamic,     ///< dynamic_cast
44   CT_CStyle,      ///< (Type)expr
45   CT_Functional   ///< Type(expr)
46 };
47 
48 namespace {
49   struct CastOperation {
50     CastOperation(Sema &S, QualType destType, ExprResult src)
51       : Self(S), SrcExpr(src), DestType(destType),
52         ResultType(destType.getNonLValueExprType(S.Context)),
53         ValueKind(Expr::getValueKindForType(destType)),
54         Kind(CK_Dependent), IsARCUnbridgedCast(false) {
55 
56       if (const BuiltinType *placeholder =
57             src.get()->getType()->getAsPlaceholderType()) {
58         PlaceholderKind = placeholder->getKind();
59       } else {
60         PlaceholderKind = (BuiltinType::Kind) 0;
61       }
62     }
63 
64     Sema &Self;
65     ExprResult SrcExpr;
66     QualType DestType;
67     QualType ResultType;
68     ExprValueKind ValueKind;
69     CastKind Kind;
70     BuiltinType::Kind PlaceholderKind;
71     CXXCastPath BasePath;
72     bool IsARCUnbridgedCast;
73 
74     SourceRange OpRange;
75     SourceRange DestRange;
76 
77     // Top-level semantics-checking routines.
78     void CheckConstCast();
79     void CheckReinterpretCast();
80     void CheckStaticCast();
81     void CheckDynamicCast();
82     void CheckCXXCStyleCast(bool FunctionalCast, bool ListInitialization);
83     void CheckCStyleCast();
84 
85     /// Complete an apparently-successful cast operation that yields
86     /// the given expression.
87     ExprResult complete(CastExpr *castExpr) {
88       // If this is an unbridged cast, wrap the result in an implicit
89       // cast that yields the unbridged-cast placeholder type.
90       if (IsARCUnbridgedCast) {
91         castExpr = ImplicitCastExpr::Create(Self.Context,
92                                             Self.Context.ARCUnbridgedCastTy,
93                                             CK_Dependent, castExpr, nullptr,
94                                             castExpr->getValueKind());
95       }
96       return castExpr;
97     }
98 
99     // Internal convenience methods.
100 
101     /// Try to handle the given placeholder expression kind.  Return
102     /// true if the source expression has the appropriate placeholder
103     /// kind.  A placeholder can only be claimed once.
104     bool claimPlaceholder(BuiltinType::Kind K) {
105       if (PlaceholderKind != K) return false;
106 
107       PlaceholderKind = (BuiltinType::Kind) 0;
108       return true;
109     }
110 
111     bool isPlaceholder() const {
112       return PlaceholderKind != 0;
113     }
114     bool isPlaceholder(BuiltinType::Kind K) const {
115       return PlaceholderKind == K;
116     }
117 
118     void checkCastAlign() {
119       Self.CheckCastAlign(SrcExpr.get(), DestType, OpRange);
120     }
121 
122     void checkObjCARCConversion(Sema::CheckedConversionKind CCK) {
123       assert(Self.getLangOpts().ObjCAutoRefCount);
124 
125       Expr *src = SrcExpr.get();
126       if (Self.CheckObjCARCConversion(OpRange, DestType, src, CCK) ==
127             Sema::ACR_unbridged)
128         IsARCUnbridgedCast = true;
129       SrcExpr = src;
130     }
131 
132     /// Check for and handle non-overload placeholder expressions.
133     void checkNonOverloadPlaceholders() {
134       if (!isPlaceholder() || isPlaceholder(BuiltinType::Overload))
135         return;
136 
137       SrcExpr = Self.CheckPlaceholderExpr(SrcExpr.get());
138       if (SrcExpr.isInvalid())
139         return;
140       PlaceholderKind = (BuiltinType::Kind) 0;
141     }
142   };
143 }
144 
145 // The Try functions attempt a specific way of casting. If they succeed, they
146 // return TC_Success. If their way of casting is not appropriate for the given
147 // arguments, they return TC_NotApplicable and *may* set diag to a diagnostic
148 // to emit if no other way succeeds. If their way of casting is appropriate but
149 // fails, they return TC_Failed and *must* set diag; they can set it to 0 if
150 // they emit a specialized diagnostic.
151 // All diagnostics returned by these functions must expect the same three
152 // arguments:
153 // %0: Cast Type (a value from the CastType enumeration)
154 // %1: Source Type
155 // %2: Destination Type
156 static TryCastResult TryLValueToRValueCast(Sema &Self, Expr *SrcExpr,
157                                            QualType DestType, bool CStyle,
158                                            CastKind &Kind,
159                                            CXXCastPath &BasePath,
160                                            unsigned &msg);
161 static TryCastResult TryStaticReferenceDowncast(Sema &Self, Expr *SrcExpr,
162                                                QualType DestType, bool CStyle,
163                                                const SourceRange &OpRange,
164                                                unsigned &msg,
165                                                CastKind &Kind,
166                                                CXXCastPath &BasePath);
167 static TryCastResult TryStaticPointerDowncast(Sema &Self, QualType SrcType,
168                                               QualType DestType, bool CStyle,
169                                               const SourceRange &OpRange,
170                                               unsigned &msg,
171                                               CastKind &Kind,
172                                               CXXCastPath &BasePath);
173 static TryCastResult TryStaticDowncast(Sema &Self, CanQualType SrcType,
174                                        CanQualType DestType, bool CStyle,
175                                        const SourceRange &OpRange,
176                                        QualType OrigSrcType,
177                                        QualType OrigDestType, unsigned &msg,
178                                        CastKind &Kind,
179                                        CXXCastPath &BasePath);
180 static TryCastResult TryStaticMemberPointerUpcast(Sema &Self, ExprResult &SrcExpr,
181                                                QualType SrcType,
182                                                QualType DestType,bool CStyle,
183                                                const SourceRange &OpRange,
184                                                unsigned &msg,
185                                                CastKind &Kind,
186                                                CXXCastPath &BasePath);
187 
188 static TryCastResult TryStaticImplicitCast(Sema &Self, ExprResult &SrcExpr,
189                                            QualType DestType,
190                                            Sema::CheckedConversionKind CCK,
191                                            const SourceRange &OpRange,
192                                            unsigned &msg, CastKind &Kind,
193                                            bool ListInitialization);
194 static TryCastResult TryStaticCast(Sema &Self, ExprResult &SrcExpr,
195                                    QualType DestType,
196                                    Sema::CheckedConversionKind CCK,
197                                    const SourceRange &OpRange,
198                                    unsigned &msg, CastKind &Kind,
199                                    CXXCastPath &BasePath,
200                                    bool ListInitialization);
201 static TryCastResult TryConstCast(Sema &Self, ExprResult &SrcExpr,
202                                   QualType DestType, bool CStyle,
203                                   unsigned &msg);
204 static TryCastResult TryReinterpretCast(Sema &Self, ExprResult &SrcExpr,
205                                         QualType DestType, bool CStyle,
206                                         const SourceRange &OpRange,
207                                         unsigned &msg,
208                                         CastKind &Kind);
209 
210 
211 /// ActOnCXXNamedCast - Parse {dynamic,static,reinterpret,const}_cast's.
212 ExprResult
213 Sema::ActOnCXXNamedCast(SourceLocation OpLoc, tok::TokenKind Kind,
214                         SourceLocation LAngleBracketLoc, Declarator &D,
215                         SourceLocation RAngleBracketLoc,
216                         SourceLocation LParenLoc, Expr *E,
217                         SourceLocation RParenLoc) {
218 
219   assert(!D.isInvalidType());
220 
221   TypeSourceInfo *TInfo = GetTypeForDeclaratorCast(D, E->getType());
222   if (D.isInvalidType())
223     return ExprError();
224 
225   if (getLangOpts().CPlusPlus) {
226     // Check that there are no default arguments (C++ only).
227     CheckExtraCXXDefaultArguments(D);
228   }
229 
230   return BuildCXXNamedCast(OpLoc, Kind, TInfo, E,
231                            SourceRange(LAngleBracketLoc, RAngleBracketLoc),
232                            SourceRange(LParenLoc, RParenLoc));
233 }
234 
235 ExprResult
236 Sema::BuildCXXNamedCast(SourceLocation OpLoc, tok::TokenKind Kind,
237                         TypeSourceInfo *DestTInfo, Expr *E,
238                         SourceRange AngleBrackets, SourceRange Parens) {
239   ExprResult Ex = E;
240   QualType DestType = DestTInfo->getType();
241 
242   // If the type is dependent, we won't do the semantic analysis now.
243   // FIXME: should we check this in a more fine-grained manner?
244   bool TypeDependent = DestType->isDependentType() ||
245                        Ex.get()->isTypeDependent() ||
246                        Ex.get()->isValueDependent();
247 
248   CastOperation Op(*this, DestType, E);
249   Op.OpRange = SourceRange(OpLoc, Parens.getEnd());
250   Op.DestRange = AngleBrackets;
251 
252   switch (Kind) {
253   default: llvm_unreachable("Unknown C++ cast!");
254 
255   case tok::kw_const_cast:
256     if (!TypeDependent) {
257       Op.CheckConstCast();
258       if (Op.SrcExpr.isInvalid())
259         return ExprError();
260     }
261     return Op.complete(CXXConstCastExpr::Create(Context, Op.ResultType,
262                                   Op.ValueKind, Op.SrcExpr.get(), DestTInfo,
263                                                 OpLoc, Parens.getEnd(),
264                                                 AngleBrackets));
265 
266   case tok::kw_dynamic_cast: {
267     if (!TypeDependent) {
268       Op.CheckDynamicCast();
269       if (Op.SrcExpr.isInvalid())
270         return ExprError();
271     }
272     return Op.complete(CXXDynamicCastExpr::Create(Context, Op.ResultType,
273                                     Op.ValueKind, Op.Kind, Op.SrcExpr.get(),
274                                                   &Op.BasePath, DestTInfo,
275                                                   OpLoc, Parens.getEnd(),
276                                                   AngleBrackets));
277   }
278   case tok::kw_reinterpret_cast: {
279     if (!TypeDependent) {
280       Op.CheckReinterpretCast();
281       if (Op.SrcExpr.isInvalid())
282         return ExprError();
283     }
284     return Op.complete(CXXReinterpretCastExpr::Create(Context, Op.ResultType,
285                                     Op.ValueKind, Op.Kind, Op.SrcExpr.get(),
286                                                       nullptr, DestTInfo, OpLoc,
287                                                       Parens.getEnd(),
288                                                       AngleBrackets));
289   }
290   case tok::kw_static_cast: {
291     if (!TypeDependent) {
292       Op.CheckStaticCast();
293       if (Op.SrcExpr.isInvalid())
294         return ExprError();
295     }
296 
297     return Op.complete(CXXStaticCastExpr::Create(Context, Op.ResultType,
298                                    Op.ValueKind, Op.Kind, Op.SrcExpr.get(),
299                                                  &Op.BasePath, DestTInfo,
300                                                  OpLoc, Parens.getEnd(),
301                                                  AngleBrackets));
302   }
303   }
304 }
305 
306 /// Try to diagnose a failed overloaded cast.  Returns true if
307 /// diagnostics were emitted.
308 static bool tryDiagnoseOverloadedCast(Sema &S, CastType CT,
309                                       SourceRange range, Expr *src,
310                                       QualType destType,
311                                       bool listInitialization) {
312   switch (CT) {
313   // These cast kinds don't consider user-defined conversions.
314   case CT_Const:
315   case CT_Reinterpret:
316   case CT_Dynamic:
317     return false;
318 
319   // These do.
320   case CT_Static:
321   case CT_CStyle:
322   case CT_Functional:
323     break;
324   }
325 
326   QualType srcType = src->getType();
327   if (!destType->isRecordType() && !srcType->isRecordType())
328     return false;
329 
330   InitializedEntity entity = InitializedEntity::InitializeTemporary(destType);
331   InitializationKind initKind
332     = (CT == CT_CStyle)? InitializationKind::CreateCStyleCast(range.getBegin(),
333                                                       range, listInitialization)
334     : (CT == CT_Functional)? InitializationKind::CreateFunctionalCast(range,
335                                                              listInitialization)
336     : InitializationKind::CreateCast(/*type range?*/ range);
337   InitializationSequence sequence(S, entity, initKind, src);
338 
339   assert(sequence.Failed() && "initialization succeeded on second try?");
340   switch (sequence.getFailureKind()) {
341   default: return false;
342 
343   case InitializationSequence::FK_ConstructorOverloadFailed:
344   case InitializationSequence::FK_UserConversionOverloadFailed:
345     break;
346   }
347 
348   OverloadCandidateSet &candidates = sequence.getFailedCandidateSet();
349 
350   unsigned msg = 0;
351   OverloadCandidateDisplayKind howManyCandidates = OCD_AllCandidates;
352 
353   switch (sequence.getFailedOverloadResult()) {
354   case OR_Success: llvm_unreachable("successful failed overload");
355   case OR_No_Viable_Function:
356     if (candidates.empty())
357       msg = diag::err_ovl_no_conversion_in_cast;
358     else
359       msg = diag::err_ovl_no_viable_conversion_in_cast;
360     howManyCandidates = OCD_AllCandidates;
361     break;
362 
363   case OR_Ambiguous:
364     msg = diag::err_ovl_ambiguous_conversion_in_cast;
365     howManyCandidates = OCD_ViableCandidates;
366     break;
367 
368   case OR_Deleted:
369     msg = diag::err_ovl_deleted_conversion_in_cast;
370     howManyCandidates = OCD_ViableCandidates;
371     break;
372   }
373 
374   S.Diag(range.getBegin(), msg)
375     << CT << srcType << destType
376     << range << src->getSourceRange();
377 
378   candidates.NoteCandidates(S, howManyCandidates, src);
379 
380   return true;
381 }
382 
383 /// Diagnose a failed cast.
384 static void diagnoseBadCast(Sema &S, unsigned msg, CastType castType,
385                             SourceRange opRange, Expr *src, QualType destType,
386                             bool listInitialization) {
387   if (msg == diag::err_bad_cxx_cast_generic &&
388       tryDiagnoseOverloadedCast(S, castType, opRange, src, destType,
389                                 listInitialization))
390     return;
391 
392   S.Diag(opRange.getBegin(), msg) << castType
393     << src->getType() << destType << opRange << src->getSourceRange();
394 }
395 
396 /// UnwrapDissimilarPointerTypes - Like Sema::UnwrapSimilarPointerTypes,
397 /// this removes one level of indirection from both types, provided that they're
398 /// the same kind of pointer (plain or to-member). Unlike the Sema function,
399 /// this one doesn't care if the two pointers-to-member don't point into the
400 /// same class. This is because CastsAwayConstness doesn't care.
401 static bool UnwrapDissimilarPointerTypes(QualType& T1, QualType& T2) {
402   const PointerType *T1PtrType = T1->getAs<PointerType>(),
403                     *T2PtrType = T2->getAs<PointerType>();
404   if (T1PtrType && T2PtrType) {
405     T1 = T1PtrType->getPointeeType();
406     T2 = T2PtrType->getPointeeType();
407     return true;
408   }
409   const ObjCObjectPointerType *T1ObjCPtrType =
410                                             T1->getAs<ObjCObjectPointerType>(),
411                               *T2ObjCPtrType =
412                                             T2->getAs<ObjCObjectPointerType>();
413   if (T1ObjCPtrType) {
414     if (T2ObjCPtrType) {
415       T1 = T1ObjCPtrType->getPointeeType();
416       T2 = T2ObjCPtrType->getPointeeType();
417       return true;
418     }
419     else if (T2PtrType) {
420       T1 = T1ObjCPtrType->getPointeeType();
421       T2 = T2PtrType->getPointeeType();
422       return true;
423     }
424   }
425   else if (T2ObjCPtrType) {
426     if (T1PtrType) {
427       T2 = T2ObjCPtrType->getPointeeType();
428       T1 = T1PtrType->getPointeeType();
429       return true;
430     }
431   }
432 
433   const MemberPointerType *T1MPType = T1->getAs<MemberPointerType>(),
434                           *T2MPType = T2->getAs<MemberPointerType>();
435   if (T1MPType && T2MPType) {
436     T1 = T1MPType->getPointeeType();
437     T2 = T2MPType->getPointeeType();
438     return true;
439   }
440 
441   const BlockPointerType *T1BPType = T1->getAs<BlockPointerType>(),
442                          *T2BPType = T2->getAs<BlockPointerType>();
443   if (T1BPType && T2BPType) {
444     T1 = T1BPType->getPointeeType();
445     T2 = T2BPType->getPointeeType();
446     return true;
447   }
448 
449   return false;
450 }
451 
452 /// CastsAwayConstness - Check if the pointer conversion from SrcType to
453 /// DestType casts away constness as defined in C++ 5.2.11p8ff. This is used by
454 /// the cast checkers.  Both arguments must denote pointer (possibly to member)
455 /// types.
456 ///
457 /// \param CheckCVR Whether to check for const/volatile/restrict qualifiers.
458 ///
459 /// \param CheckObjCLifetime Whether to check Objective-C lifetime qualifiers.
460 static bool
461 CastsAwayConstness(Sema &Self, QualType SrcType, QualType DestType,
462                    bool CheckCVR, bool CheckObjCLifetime,
463                    QualType *TheOffendingSrcType = nullptr,
464                    QualType *TheOffendingDestType = nullptr,
465                    Qualifiers *CastAwayQualifiers = nullptr) {
466   // If the only checking we care about is for Objective-C lifetime qualifiers,
467   // and we're not in ARC mode, there's nothing to check.
468   if (!CheckCVR && CheckObjCLifetime &&
469       !Self.Context.getLangOpts().ObjCAutoRefCount)
470     return false;
471 
472   // Casting away constness is defined in C++ 5.2.11p8 with reference to
473   // C++ 4.4. We piggyback on Sema::IsQualificationConversion for this, since
474   // the rules are non-trivial. So first we construct Tcv *...cv* as described
475   // in C++ 5.2.11p8.
476   assert((SrcType->isAnyPointerType() || SrcType->isMemberPointerType() ||
477           SrcType->isBlockPointerType()) &&
478          "Source type is not pointer or pointer to member.");
479   assert((DestType->isAnyPointerType() || DestType->isMemberPointerType() ||
480           DestType->isBlockPointerType()) &&
481          "Destination type is not pointer or pointer to member.");
482 
483   QualType UnwrappedSrcType = Self.Context.getCanonicalType(SrcType),
484            UnwrappedDestType = Self.Context.getCanonicalType(DestType);
485   SmallVector<Qualifiers, 8> cv1, cv2;
486 
487   // Find the qualifiers. We only care about cvr-qualifiers for the
488   // purpose of this check, because other qualifiers (address spaces,
489   // Objective-C GC, etc.) are part of the type's identity.
490   QualType PrevUnwrappedSrcType = UnwrappedSrcType;
491   QualType PrevUnwrappedDestType = UnwrappedDestType;
492   while (UnwrapDissimilarPointerTypes(UnwrappedSrcType, UnwrappedDestType)) {
493     // Determine the relevant qualifiers at this level.
494     Qualifiers SrcQuals, DestQuals;
495     Self.Context.getUnqualifiedArrayType(UnwrappedSrcType, SrcQuals);
496     Self.Context.getUnqualifiedArrayType(UnwrappedDestType, DestQuals);
497 
498     Qualifiers RetainedSrcQuals, RetainedDestQuals;
499     if (CheckCVR) {
500       RetainedSrcQuals.setCVRQualifiers(SrcQuals.getCVRQualifiers());
501       RetainedDestQuals.setCVRQualifiers(DestQuals.getCVRQualifiers());
502 
503       if (RetainedSrcQuals != RetainedDestQuals && TheOffendingSrcType &&
504           TheOffendingDestType && CastAwayQualifiers) {
505         *TheOffendingSrcType = PrevUnwrappedSrcType;
506         *TheOffendingDestType = PrevUnwrappedDestType;
507         *CastAwayQualifiers = RetainedSrcQuals - RetainedDestQuals;
508       }
509     }
510 
511     if (CheckObjCLifetime &&
512         !DestQuals.compatiblyIncludesObjCLifetime(SrcQuals))
513       return true;
514 
515     cv1.push_back(RetainedSrcQuals);
516     cv2.push_back(RetainedDestQuals);
517 
518     PrevUnwrappedSrcType = UnwrappedSrcType;
519     PrevUnwrappedDestType = UnwrappedDestType;
520   }
521   if (cv1.empty())
522     return false;
523 
524   // Construct void pointers with those qualifiers (in reverse order of
525   // unwrapping, of course).
526   QualType SrcConstruct = Self.Context.VoidTy;
527   QualType DestConstruct = Self.Context.VoidTy;
528   ASTContext &Context = Self.Context;
529   for (SmallVectorImpl<Qualifiers>::reverse_iterator i1 = cv1.rbegin(),
530                                                      i2 = cv2.rbegin();
531        i1 != cv1.rend(); ++i1, ++i2) {
532     SrcConstruct
533       = Context.getPointerType(Context.getQualifiedType(SrcConstruct, *i1));
534     DestConstruct
535       = Context.getPointerType(Context.getQualifiedType(DestConstruct, *i2));
536   }
537 
538   // Test if they're compatible.
539   bool ObjCLifetimeConversion;
540   return SrcConstruct != DestConstruct &&
541     !Self.IsQualificationConversion(SrcConstruct, DestConstruct, false,
542                                     ObjCLifetimeConversion);
543 }
544 
545 /// CheckDynamicCast - Check that a dynamic_cast\<DestType\>(SrcExpr) is valid.
546 /// Refer to C++ 5.2.7 for details. Dynamic casts are used mostly for runtime-
547 /// checked downcasts in class hierarchies.
548 void CastOperation::CheckDynamicCast() {
549   if (ValueKind == VK_RValue)
550     SrcExpr = Self.DefaultFunctionArrayLvalueConversion(SrcExpr.get());
551   else if (isPlaceholder())
552     SrcExpr = Self.CheckPlaceholderExpr(SrcExpr.get());
553   if (SrcExpr.isInvalid()) // if conversion failed, don't report another error
554     return;
555 
556   QualType OrigSrcType = SrcExpr.get()->getType();
557   QualType DestType = Self.Context.getCanonicalType(this->DestType);
558 
559   // C++ 5.2.7p1: T shall be a pointer or reference to a complete class type,
560   //   or "pointer to cv void".
561 
562   QualType DestPointee;
563   const PointerType *DestPointer = DestType->getAs<PointerType>();
564   const ReferenceType *DestReference = nullptr;
565   if (DestPointer) {
566     DestPointee = DestPointer->getPointeeType();
567   } else if ((DestReference = DestType->getAs<ReferenceType>())) {
568     DestPointee = DestReference->getPointeeType();
569   } else {
570     Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_ref_or_ptr)
571       << this->DestType << DestRange;
572     SrcExpr = ExprError();
573     return;
574   }
575 
576   const RecordType *DestRecord = DestPointee->getAs<RecordType>();
577   if (DestPointee->isVoidType()) {
578     assert(DestPointer && "Reference to void is not possible");
579   } else if (DestRecord) {
580     if (Self.RequireCompleteType(OpRange.getBegin(), DestPointee,
581                                  diag::err_bad_dynamic_cast_incomplete,
582                                  DestRange)) {
583       SrcExpr = ExprError();
584       return;
585     }
586   } else {
587     Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_class)
588       << DestPointee.getUnqualifiedType() << DestRange;
589     SrcExpr = ExprError();
590     return;
591   }
592 
593   // C++0x 5.2.7p2: If T is a pointer type, v shall be an rvalue of a pointer to
594   //   complete class type, [...]. If T is an lvalue reference type, v shall be
595   //   an lvalue of a complete class type, [...]. If T is an rvalue reference
596   //   type, v shall be an expression having a complete class type, [...]
597   QualType SrcType = Self.Context.getCanonicalType(OrigSrcType);
598   QualType SrcPointee;
599   if (DestPointer) {
600     if (const PointerType *SrcPointer = SrcType->getAs<PointerType>()) {
601       SrcPointee = SrcPointer->getPointeeType();
602     } else {
603       Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_ptr)
604         << OrigSrcType << SrcExpr.get()->getSourceRange();
605       SrcExpr = ExprError();
606       return;
607     }
608   } else if (DestReference->isLValueReferenceType()) {
609     if (!SrcExpr.get()->isLValue()) {
610       Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_rvalue)
611         << CT_Dynamic << OrigSrcType << this->DestType << OpRange;
612     }
613     SrcPointee = SrcType;
614   } else {
615     // If we're dynamic_casting from a prvalue to an rvalue reference, we need
616     // to materialize the prvalue before we bind the reference to it.
617     if (SrcExpr.get()->isRValue())
618       SrcExpr = new (Self.Context) MaterializeTemporaryExpr(
619           SrcType, SrcExpr.get(), /*IsLValueReference*/false);
620     SrcPointee = SrcType;
621   }
622 
623   const RecordType *SrcRecord = SrcPointee->getAs<RecordType>();
624   if (SrcRecord) {
625     if (Self.RequireCompleteType(OpRange.getBegin(), SrcPointee,
626                                  diag::err_bad_dynamic_cast_incomplete,
627                                  SrcExpr.get())) {
628       SrcExpr = ExprError();
629       return;
630     }
631   } else {
632     Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_class)
633       << SrcPointee.getUnqualifiedType() << SrcExpr.get()->getSourceRange();
634     SrcExpr = ExprError();
635     return;
636   }
637 
638   assert((DestPointer || DestReference) &&
639     "Bad destination non-ptr/ref slipped through.");
640   assert((DestRecord || DestPointee->isVoidType()) &&
641     "Bad destination pointee slipped through.");
642   assert(SrcRecord && "Bad source pointee slipped through.");
643 
644   // C++ 5.2.7p1: The dynamic_cast operator shall not cast away constness.
645   if (!DestPointee.isAtLeastAsQualifiedAs(SrcPointee)) {
646     Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_qualifiers_away)
647       << CT_Dynamic << OrigSrcType << this->DestType << OpRange;
648     SrcExpr = ExprError();
649     return;
650   }
651 
652   // C++ 5.2.7p3: If the type of v is the same as the required result type,
653   //   [except for cv].
654   if (DestRecord == SrcRecord) {
655     Kind = CK_NoOp;
656     return;
657   }
658 
659   // C++ 5.2.7p5
660   // Upcasts are resolved statically.
661   if (DestRecord && Self.IsDerivedFrom(SrcPointee, DestPointee)) {
662     if (Self.CheckDerivedToBaseConversion(SrcPointee, DestPointee,
663                                            OpRange.getBegin(), OpRange,
664                                            &BasePath)) {
665       SrcExpr = ExprError();
666       return;
667     }
668 
669     Kind = CK_DerivedToBase;
670 
671     // If we are casting to or through a virtual base class, we need a
672     // vtable.
673     if (Self.BasePathInvolvesVirtualBase(BasePath))
674       Self.MarkVTableUsed(OpRange.getBegin(),
675                           cast<CXXRecordDecl>(SrcRecord->getDecl()));
676     return;
677   }
678 
679   // C++ 5.2.7p6: Otherwise, v shall be [polymorphic].
680   const RecordDecl *SrcDecl = SrcRecord->getDecl()->getDefinition();
681   assert(SrcDecl && "Definition missing");
682   if (!cast<CXXRecordDecl>(SrcDecl)->isPolymorphic()) {
683     Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_polymorphic)
684       << SrcPointee.getUnqualifiedType() << SrcExpr.get()->getSourceRange();
685     SrcExpr = ExprError();
686   }
687   Self.MarkVTableUsed(OpRange.getBegin(),
688                       cast<CXXRecordDecl>(SrcRecord->getDecl()));
689 
690   // dynamic_cast is not available with -fno-rtti.
691   // As an exception, dynamic_cast to void* is available because it doesn't
692   // use RTTI.
693   if (!Self.getLangOpts().RTTI && !DestPointee->isVoidType()) {
694     Self.Diag(OpRange.getBegin(), diag::err_no_dynamic_cast_with_fno_rtti);
695     SrcExpr = ExprError();
696     return;
697   }
698 
699   // Done. Everything else is run-time checks.
700   Kind = CK_Dynamic;
701 }
702 
703 /// CheckConstCast - Check that a const_cast\<DestType\>(SrcExpr) is valid.
704 /// Refer to C++ 5.2.11 for details. const_cast is typically used in code
705 /// like this:
706 /// const char *str = "literal";
707 /// legacy_function(const_cast\<char*\>(str));
708 void CastOperation::CheckConstCast() {
709   if (ValueKind == VK_RValue)
710     SrcExpr = Self.DefaultFunctionArrayLvalueConversion(SrcExpr.get());
711   else if (isPlaceholder())
712     SrcExpr = Self.CheckPlaceholderExpr(SrcExpr.get());
713   if (SrcExpr.isInvalid()) // if conversion failed, don't report another error
714     return;
715 
716   unsigned msg = diag::err_bad_cxx_cast_generic;
717   if (TryConstCast(Self, SrcExpr, DestType, /*CStyle*/false, msg) != TC_Success
718       && msg != 0) {
719     Self.Diag(OpRange.getBegin(), msg) << CT_Const
720       << SrcExpr.get()->getType() << DestType << OpRange;
721     SrcExpr = ExprError();
722   }
723 }
724 
725 /// Check that a reinterpret_cast\<DestType\>(SrcExpr) is not used as upcast
726 /// or downcast between respective pointers or references.
727 static void DiagnoseReinterpretUpDownCast(Sema &Self, const Expr *SrcExpr,
728                                           QualType DestType,
729                                           SourceRange OpRange) {
730   QualType SrcType = SrcExpr->getType();
731   // When casting from pointer or reference, get pointee type; use original
732   // type otherwise.
733   const CXXRecordDecl *SrcPointeeRD = SrcType->getPointeeCXXRecordDecl();
734   const CXXRecordDecl *SrcRD =
735     SrcPointeeRD ? SrcPointeeRD : SrcType->getAsCXXRecordDecl();
736 
737   // Examining subobjects for records is only possible if the complete and
738   // valid definition is available.  Also, template instantiation is not
739   // allowed here.
740   if (!SrcRD || !SrcRD->isCompleteDefinition() || SrcRD->isInvalidDecl())
741     return;
742 
743   const CXXRecordDecl *DestRD = DestType->getPointeeCXXRecordDecl();
744 
745   if (!DestRD || !DestRD->isCompleteDefinition() || DestRD->isInvalidDecl())
746     return;
747 
748   enum {
749     ReinterpretUpcast,
750     ReinterpretDowncast
751   } ReinterpretKind;
752 
753   CXXBasePaths BasePaths;
754 
755   if (SrcRD->isDerivedFrom(DestRD, BasePaths))
756     ReinterpretKind = ReinterpretUpcast;
757   else if (DestRD->isDerivedFrom(SrcRD, BasePaths))
758     ReinterpretKind = ReinterpretDowncast;
759   else
760     return;
761 
762   bool VirtualBase = true;
763   bool NonZeroOffset = false;
764   for (CXXBasePaths::const_paths_iterator I = BasePaths.begin(),
765                                           E = BasePaths.end();
766        I != E; ++I) {
767     const CXXBasePath &Path = *I;
768     CharUnits Offset = CharUnits::Zero();
769     bool IsVirtual = false;
770     for (CXXBasePath::const_iterator IElem = Path.begin(), EElem = Path.end();
771          IElem != EElem; ++IElem) {
772       IsVirtual = IElem->Base->isVirtual();
773       if (IsVirtual)
774         break;
775       const CXXRecordDecl *BaseRD = IElem->Base->getType()->getAsCXXRecordDecl();
776       assert(BaseRD && "Base type should be a valid unqualified class type");
777       // Don't check if any base has invalid declaration or has no definition
778       // since it has no layout info.
779       const CXXRecordDecl *Class = IElem->Class,
780                           *ClassDefinition = Class->getDefinition();
781       if (Class->isInvalidDecl() || !ClassDefinition ||
782           !ClassDefinition->isCompleteDefinition())
783         return;
784 
785       const ASTRecordLayout &DerivedLayout =
786           Self.Context.getASTRecordLayout(Class);
787       Offset += DerivedLayout.getBaseClassOffset(BaseRD);
788     }
789     if (!IsVirtual) {
790       // Don't warn if any path is a non-virtually derived base at offset zero.
791       if (Offset.isZero())
792         return;
793       // Offset makes sense only for non-virtual bases.
794       else
795         NonZeroOffset = true;
796     }
797     VirtualBase = VirtualBase && IsVirtual;
798   }
799 
800   (void) NonZeroOffset; // Silence set but not used warning.
801   assert((VirtualBase || NonZeroOffset) &&
802          "Should have returned if has non-virtual base with zero offset");
803 
804   QualType BaseType =
805       ReinterpretKind == ReinterpretUpcast? DestType : SrcType;
806   QualType DerivedType =
807       ReinterpretKind == ReinterpretUpcast? SrcType : DestType;
808 
809   SourceLocation BeginLoc = OpRange.getBegin();
810   Self.Diag(BeginLoc, diag::warn_reinterpret_different_from_static)
811     << DerivedType << BaseType << !VirtualBase << int(ReinterpretKind)
812     << OpRange;
813   Self.Diag(BeginLoc, diag::note_reinterpret_updowncast_use_static)
814     << int(ReinterpretKind)
815     << FixItHint::CreateReplacement(BeginLoc, "static_cast");
816 }
817 
818 /// CheckReinterpretCast - Check that a reinterpret_cast\<DestType\>(SrcExpr) is
819 /// valid.
820 /// Refer to C++ 5.2.10 for details. reinterpret_cast is typically used in code
821 /// like this:
822 /// char *bytes = reinterpret_cast\<char*\>(int_ptr);
823 void CastOperation::CheckReinterpretCast() {
824   if (ValueKind == VK_RValue && !isPlaceholder(BuiltinType::Overload))
825     SrcExpr = Self.DefaultFunctionArrayLvalueConversion(SrcExpr.get());
826   else
827     checkNonOverloadPlaceholders();
828   if (SrcExpr.isInvalid()) // if conversion failed, don't report another error
829     return;
830 
831   unsigned msg = diag::err_bad_cxx_cast_generic;
832   TryCastResult tcr =
833     TryReinterpretCast(Self, SrcExpr, DestType,
834                        /*CStyle*/false, OpRange, msg, Kind);
835   if (tcr != TC_Success && msg != 0)
836   {
837     if (SrcExpr.isInvalid()) // if conversion failed, don't report another error
838       return;
839     if (SrcExpr.get()->getType() == Self.Context.OverloadTy) {
840       //FIXME: &f<int>; is overloaded and resolvable
841       Self.Diag(OpRange.getBegin(), diag::err_bad_reinterpret_cast_overload)
842         << OverloadExpr::find(SrcExpr.get()).Expression->getName()
843         << DestType << OpRange;
844       Self.NoteAllOverloadCandidates(SrcExpr.get());
845 
846     } else {
847       diagnoseBadCast(Self, msg, CT_Reinterpret, OpRange, SrcExpr.get(),
848                       DestType, /*listInitialization=*/false);
849     }
850     SrcExpr = ExprError();
851   } else if (tcr == TC_Success) {
852     if (Self.getLangOpts().ObjCAutoRefCount)
853       checkObjCARCConversion(Sema::CCK_OtherCast);
854     DiagnoseReinterpretUpDownCast(Self, SrcExpr.get(), DestType, OpRange);
855   }
856 }
857 
858 
859 /// CheckStaticCast - Check that a static_cast\<DestType\>(SrcExpr) is valid.
860 /// Refer to C++ 5.2.9 for details. Static casts are mostly used for making
861 /// implicit conversions explicit and getting rid of data loss warnings.
862 void CastOperation::CheckStaticCast() {
863   if (isPlaceholder()) {
864     checkNonOverloadPlaceholders();
865     if (SrcExpr.isInvalid())
866       return;
867   }
868 
869   // This test is outside everything else because it's the only case where
870   // a non-lvalue-reference target type does not lead to decay.
871   // C++ 5.2.9p4: Any expression can be explicitly converted to type "cv void".
872   if (DestType->isVoidType()) {
873     Kind = CK_ToVoid;
874 
875     if (claimPlaceholder(BuiltinType::Overload)) {
876       Self.ResolveAndFixSingleFunctionTemplateSpecialization(SrcExpr,
877                 false, // Decay Function to ptr
878                 true, // Complain
879                 OpRange, DestType, diag::err_bad_static_cast_overload);
880       if (SrcExpr.isInvalid())
881         return;
882     }
883 
884     SrcExpr = Self.IgnoredValueConversions(SrcExpr.get());
885     return;
886   }
887 
888   if (ValueKind == VK_RValue && !DestType->isRecordType() &&
889       !isPlaceholder(BuiltinType::Overload)) {
890     SrcExpr = Self.DefaultFunctionArrayLvalueConversion(SrcExpr.get());
891     if (SrcExpr.isInvalid()) // if conversion failed, don't report another error
892       return;
893   }
894 
895   unsigned msg = diag::err_bad_cxx_cast_generic;
896   TryCastResult tcr
897     = TryStaticCast(Self, SrcExpr, DestType, Sema::CCK_OtherCast, OpRange, msg,
898                     Kind, BasePath, /*ListInitialization=*/false);
899   if (tcr != TC_Success && msg != 0) {
900     if (SrcExpr.isInvalid())
901       return;
902     if (SrcExpr.get()->getType() == Self.Context.OverloadTy) {
903       OverloadExpr* oe = OverloadExpr::find(SrcExpr.get()).Expression;
904       Self.Diag(OpRange.getBegin(), diag::err_bad_static_cast_overload)
905         << oe->getName() << DestType << OpRange
906         << oe->getQualifierLoc().getSourceRange();
907       Self.NoteAllOverloadCandidates(SrcExpr.get());
908     } else {
909       diagnoseBadCast(Self, msg, CT_Static, OpRange, SrcExpr.get(), DestType,
910                       /*listInitialization=*/false);
911     }
912     SrcExpr = ExprError();
913   } else if (tcr == TC_Success) {
914     if (Kind == CK_BitCast)
915       checkCastAlign();
916     if (Self.getLangOpts().ObjCAutoRefCount)
917       checkObjCARCConversion(Sema::CCK_OtherCast);
918   } else if (Kind == CK_BitCast) {
919     checkCastAlign();
920   }
921 }
922 
923 /// TryStaticCast - Check if a static cast can be performed, and do so if
924 /// possible. If @p CStyle, ignore access restrictions on hierarchy casting
925 /// and casting away constness.
926 static TryCastResult TryStaticCast(Sema &Self, ExprResult &SrcExpr,
927                                    QualType DestType,
928                                    Sema::CheckedConversionKind CCK,
929                                    const SourceRange &OpRange, unsigned &msg,
930                                    CastKind &Kind, CXXCastPath &BasePath,
931                                    bool ListInitialization) {
932   // Determine whether we have the semantics of a C-style cast.
933   bool CStyle
934     = (CCK == Sema::CCK_CStyleCast || CCK == Sema::CCK_FunctionalCast);
935 
936   // The order the tests is not entirely arbitrary. There is one conversion
937   // that can be handled in two different ways. Given:
938   // struct A {};
939   // struct B : public A {
940   //   B(); B(const A&);
941   // };
942   // const A &a = B();
943   // the cast static_cast<const B&>(a) could be seen as either a static
944   // reference downcast, or an explicit invocation of the user-defined
945   // conversion using B's conversion constructor.
946   // DR 427 specifies that the downcast is to be applied here.
947 
948   // C++ 5.2.9p4: Any expression can be explicitly converted to type "cv void".
949   // Done outside this function.
950 
951   TryCastResult tcr;
952 
953   // C++ 5.2.9p5, reference downcast.
954   // See the function for details.
955   // DR 427 specifies that this is to be applied before paragraph 2.
956   tcr = TryStaticReferenceDowncast(Self, SrcExpr.get(), DestType, CStyle,
957                                    OpRange, msg, Kind, BasePath);
958   if (tcr != TC_NotApplicable)
959     return tcr;
960 
961   // C++0x [expr.static.cast]p3:
962   //   A glvalue of type "cv1 T1" can be cast to type "rvalue reference to cv2
963   //   T2" if "cv2 T2" is reference-compatible with "cv1 T1".
964   tcr = TryLValueToRValueCast(Self, SrcExpr.get(), DestType, CStyle, Kind,
965                               BasePath, msg);
966   if (tcr != TC_NotApplicable)
967     return tcr;
968 
969   // C++ 5.2.9p2: An expression e can be explicitly converted to a type T
970   //   [...] if the declaration "T t(e);" is well-formed, [...].
971   tcr = TryStaticImplicitCast(Self, SrcExpr, DestType, CCK, OpRange, msg,
972                               Kind, ListInitialization);
973   if (SrcExpr.isInvalid())
974     return TC_Failed;
975   if (tcr != TC_NotApplicable)
976     return tcr;
977 
978   // C++ 5.2.9p6: May apply the reverse of any standard conversion, except
979   // lvalue-to-rvalue, array-to-pointer, function-to-pointer, and boolean
980   // conversions, subject to further restrictions.
981   // Also, C++ 5.2.9p1 forbids casting away constness, which makes reversal
982   // of qualification conversions impossible.
983   // In the CStyle case, the earlier attempt to const_cast should have taken
984   // care of reverse qualification conversions.
985 
986   QualType SrcType = Self.Context.getCanonicalType(SrcExpr.get()->getType());
987 
988   // C++0x 5.2.9p9: A value of a scoped enumeration type can be explicitly
989   // converted to an integral type. [...] A value of a scoped enumeration type
990   // can also be explicitly converted to a floating-point type [...].
991   if (const EnumType *Enum = SrcType->getAs<EnumType>()) {
992     if (Enum->getDecl()->isScoped()) {
993       if (DestType->isBooleanType()) {
994         Kind = CK_IntegralToBoolean;
995         return TC_Success;
996       } else if (DestType->isIntegralType(Self.Context)) {
997         Kind = CK_IntegralCast;
998         return TC_Success;
999       } else if (DestType->isRealFloatingType()) {
1000         Kind = CK_IntegralToFloating;
1001         return TC_Success;
1002       }
1003     }
1004   }
1005 
1006   // Reverse integral promotion/conversion. All such conversions are themselves
1007   // again integral promotions or conversions and are thus already handled by
1008   // p2 (TryDirectInitialization above).
1009   // (Note: any data loss warnings should be suppressed.)
1010   // The exception is the reverse of enum->integer, i.e. integer->enum (and
1011   // enum->enum). See also C++ 5.2.9p7.
1012   // The same goes for reverse floating point promotion/conversion and
1013   // floating-integral conversions. Again, only floating->enum is relevant.
1014   if (DestType->isEnumeralType()) {
1015     if (SrcType->isIntegralOrEnumerationType()) {
1016       Kind = CK_IntegralCast;
1017       return TC_Success;
1018     } else if (SrcType->isRealFloatingType())   {
1019       Kind = CK_FloatingToIntegral;
1020       return TC_Success;
1021     }
1022   }
1023 
1024   // Reverse pointer upcast. C++ 4.10p3 specifies pointer upcast.
1025   // C++ 5.2.9p8 additionally disallows a cast path through virtual inheritance.
1026   tcr = TryStaticPointerDowncast(Self, SrcType, DestType, CStyle, OpRange, msg,
1027                                  Kind, BasePath);
1028   if (tcr != TC_NotApplicable)
1029     return tcr;
1030 
1031   // Reverse member pointer conversion. C++ 4.11 specifies member pointer
1032   // conversion. C++ 5.2.9p9 has additional information.
1033   // DR54's access restrictions apply here also.
1034   tcr = TryStaticMemberPointerUpcast(Self, SrcExpr, SrcType, DestType, CStyle,
1035                                      OpRange, msg, Kind, BasePath);
1036   if (tcr != TC_NotApplicable)
1037     return tcr;
1038 
1039   // Reverse pointer conversion to void*. C++ 4.10.p2 specifies conversion to
1040   // void*. C++ 5.2.9p10 specifies additional restrictions, which really is
1041   // just the usual constness stuff.
1042   if (const PointerType *SrcPointer = SrcType->getAs<PointerType>()) {
1043     QualType SrcPointee = SrcPointer->getPointeeType();
1044     if (SrcPointee->isVoidType()) {
1045       if (const PointerType *DestPointer = DestType->getAs<PointerType>()) {
1046         QualType DestPointee = DestPointer->getPointeeType();
1047         if (DestPointee->isIncompleteOrObjectType()) {
1048           // This is definitely the intended conversion, but it might fail due
1049           // to a qualifier violation. Note that we permit Objective-C lifetime
1050           // and GC qualifier mismatches here.
1051           if (!CStyle) {
1052             Qualifiers DestPointeeQuals = DestPointee.getQualifiers();
1053             Qualifiers SrcPointeeQuals = SrcPointee.getQualifiers();
1054             DestPointeeQuals.removeObjCGCAttr();
1055             DestPointeeQuals.removeObjCLifetime();
1056             SrcPointeeQuals.removeObjCGCAttr();
1057             SrcPointeeQuals.removeObjCLifetime();
1058             if (DestPointeeQuals != SrcPointeeQuals &&
1059                 !DestPointeeQuals.compatiblyIncludes(SrcPointeeQuals)) {
1060               msg = diag::err_bad_cxx_cast_qualifiers_away;
1061               return TC_Failed;
1062             }
1063           }
1064           Kind = CK_BitCast;
1065           return TC_Success;
1066         }
1067       }
1068       else if (DestType->isObjCObjectPointerType()) {
1069         // allow both c-style cast and static_cast of objective-c pointers as
1070         // they are pervasive.
1071         Kind = CK_CPointerToObjCPointerCast;
1072         return TC_Success;
1073       }
1074       else if (CStyle && DestType->isBlockPointerType()) {
1075         // allow c-style cast of void * to block pointers.
1076         Kind = CK_AnyPointerToBlockPointerCast;
1077         return TC_Success;
1078       }
1079     }
1080   }
1081   // Allow arbitray objective-c pointer conversion with static casts.
1082   if (SrcType->isObjCObjectPointerType() &&
1083       DestType->isObjCObjectPointerType()) {
1084     Kind = CK_BitCast;
1085     return TC_Success;
1086   }
1087   // Allow ns-pointer to cf-pointer conversion in either direction
1088   // with static casts.
1089   if (!CStyle &&
1090       Self.CheckTollFreeBridgeStaticCast(DestType, SrcExpr.get(), Kind))
1091     return TC_Success;
1092 
1093   // We tried everything. Everything! Nothing works! :-(
1094   return TC_NotApplicable;
1095 }
1096 
1097 /// Tests whether a conversion according to N2844 is valid.
1098 TryCastResult
1099 TryLValueToRValueCast(Sema &Self, Expr *SrcExpr, QualType DestType,
1100                       bool CStyle, CastKind &Kind, CXXCastPath &BasePath,
1101                       unsigned &msg) {
1102   // C++0x [expr.static.cast]p3:
1103   //   A glvalue of type "cv1 T1" can be cast to type "rvalue reference to
1104   //   cv2 T2" if "cv2 T2" is reference-compatible with "cv1 T1".
1105   const RValueReferenceType *R = DestType->getAs<RValueReferenceType>();
1106   if (!R)
1107     return TC_NotApplicable;
1108 
1109   if (!SrcExpr->isGLValue())
1110     return TC_NotApplicable;
1111 
1112   // Because we try the reference downcast before this function, from now on
1113   // this is the only cast possibility, so we issue an error if we fail now.
1114   // FIXME: Should allow casting away constness if CStyle.
1115   bool DerivedToBase;
1116   bool ObjCConversion;
1117   bool ObjCLifetimeConversion;
1118   QualType FromType = SrcExpr->getType();
1119   QualType ToType = R->getPointeeType();
1120   if (CStyle) {
1121     FromType = FromType.getUnqualifiedType();
1122     ToType = ToType.getUnqualifiedType();
1123   }
1124 
1125   if (Self.CompareReferenceRelationship(SrcExpr->getLocStart(),
1126                                         ToType, FromType,
1127                                         DerivedToBase, ObjCConversion,
1128                                         ObjCLifetimeConversion)
1129         < Sema::Ref_Compatible_With_Added_Qualification) {
1130     msg = diag::err_bad_lvalue_to_rvalue_cast;
1131     return TC_Failed;
1132   }
1133 
1134   if (DerivedToBase) {
1135     Kind = CK_DerivedToBase;
1136     CXXBasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/true,
1137                        /*DetectVirtual=*/true);
1138     if (!Self.IsDerivedFrom(SrcExpr->getType(), R->getPointeeType(), Paths))
1139       return TC_NotApplicable;
1140 
1141     Self.BuildBasePathArray(Paths, BasePath);
1142   } else
1143     Kind = CK_NoOp;
1144 
1145   return TC_Success;
1146 }
1147 
1148 /// Tests whether a conversion according to C++ 5.2.9p5 is valid.
1149 TryCastResult
1150 TryStaticReferenceDowncast(Sema &Self, Expr *SrcExpr, QualType DestType,
1151                            bool CStyle, const SourceRange &OpRange,
1152                            unsigned &msg, CastKind &Kind,
1153                            CXXCastPath &BasePath) {
1154   // C++ 5.2.9p5: An lvalue of type "cv1 B", where B is a class type, can be
1155   //   cast to type "reference to cv2 D", where D is a class derived from B,
1156   //   if a valid standard conversion from "pointer to D" to "pointer to B"
1157   //   exists, cv2 >= cv1, and B is not a virtual base class of D.
1158   // In addition, DR54 clarifies that the base must be accessible in the
1159   // current context. Although the wording of DR54 only applies to the pointer
1160   // variant of this rule, the intent is clearly for it to apply to the this
1161   // conversion as well.
1162 
1163   const ReferenceType *DestReference = DestType->getAs<ReferenceType>();
1164   if (!DestReference) {
1165     return TC_NotApplicable;
1166   }
1167   bool RValueRef = DestReference->isRValueReferenceType();
1168   if (!RValueRef && !SrcExpr->isLValue()) {
1169     // We know the left side is an lvalue reference, so we can suggest a reason.
1170     msg = diag::err_bad_cxx_cast_rvalue;
1171     return TC_NotApplicable;
1172   }
1173 
1174   QualType DestPointee = DestReference->getPointeeType();
1175 
1176   // FIXME: If the source is a prvalue, we should issue a warning (because the
1177   // cast always has undefined behavior), and for AST consistency, we should
1178   // materialize a temporary.
1179   return TryStaticDowncast(Self,
1180                            Self.Context.getCanonicalType(SrcExpr->getType()),
1181                            Self.Context.getCanonicalType(DestPointee), CStyle,
1182                            OpRange, SrcExpr->getType(), DestType, msg, Kind,
1183                            BasePath);
1184 }
1185 
1186 /// Tests whether a conversion according to C++ 5.2.9p8 is valid.
1187 TryCastResult
1188 TryStaticPointerDowncast(Sema &Self, QualType SrcType, QualType DestType,
1189                          bool CStyle, const SourceRange &OpRange,
1190                          unsigned &msg, CastKind &Kind,
1191                          CXXCastPath &BasePath) {
1192   // C++ 5.2.9p8: An rvalue of type "pointer to cv1 B", where B is a class
1193   //   type, can be converted to an rvalue of type "pointer to cv2 D", where D
1194   //   is a class derived from B, if a valid standard conversion from "pointer
1195   //   to D" to "pointer to B" exists, cv2 >= cv1, and B is not a virtual base
1196   //   class of D.
1197   // In addition, DR54 clarifies that the base must be accessible in the
1198   // current context.
1199 
1200   const PointerType *DestPointer = DestType->getAs<PointerType>();
1201   if (!DestPointer) {
1202     return TC_NotApplicable;
1203   }
1204 
1205   const PointerType *SrcPointer = SrcType->getAs<PointerType>();
1206   if (!SrcPointer) {
1207     msg = diag::err_bad_static_cast_pointer_nonpointer;
1208     return TC_NotApplicable;
1209   }
1210 
1211   return TryStaticDowncast(Self,
1212                    Self.Context.getCanonicalType(SrcPointer->getPointeeType()),
1213                   Self.Context.getCanonicalType(DestPointer->getPointeeType()),
1214                            CStyle, OpRange, SrcType, DestType, msg, Kind,
1215                            BasePath);
1216 }
1217 
1218 /// TryStaticDowncast - Common functionality of TryStaticReferenceDowncast and
1219 /// TryStaticPointerDowncast. Tests whether a static downcast from SrcType to
1220 /// DestType is possible and allowed.
1221 TryCastResult
1222 TryStaticDowncast(Sema &Self, CanQualType SrcType, CanQualType DestType,
1223                   bool CStyle, const SourceRange &OpRange, QualType OrigSrcType,
1224                   QualType OrigDestType, unsigned &msg,
1225                   CastKind &Kind, CXXCastPath &BasePath) {
1226   // We can only work with complete types. But don't complain if it doesn't work
1227   if (Self.RequireCompleteType(OpRange.getBegin(), SrcType, 0) ||
1228       Self.RequireCompleteType(OpRange.getBegin(), DestType, 0))
1229     return TC_NotApplicable;
1230 
1231   // Downcast can only happen in class hierarchies, so we need classes.
1232   if (!DestType->getAs<RecordType>() || !SrcType->getAs<RecordType>()) {
1233     return TC_NotApplicable;
1234   }
1235 
1236   CXXBasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/true,
1237                      /*DetectVirtual=*/true);
1238   if (!Self.IsDerivedFrom(DestType, SrcType, Paths)) {
1239     return TC_NotApplicable;
1240   }
1241 
1242   // Target type does derive from source type. Now we're serious. If an error
1243   // appears now, it's not ignored.
1244   // This may not be entirely in line with the standard. Take for example:
1245   // struct A {};
1246   // struct B : virtual A {
1247   //   B(A&);
1248   // };
1249   //
1250   // void f()
1251   // {
1252   //   (void)static_cast<const B&>(*((A*)0));
1253   // }
1254   // As far as the standard is concerned, p5 does not apply (A is virtual), so
1255   // p2 should be used instead - "const B& t(*((A*)0));" is perfectly valid.
1256   // However, both GCC and Comeau reject this example, and accepting it would
1257   // mean more complex code if we're to preserve the nice error message.
1258   // FIXME: Being 100% compliant here would be nice to have.
1259 
1260   // Must preserve cv, as always, unless we're in C-style mode.
1261   if (!CStyle && !DestType.isAtLeastAsQualifiedAs(SrcType)) {
1262     msg = diag::err_bad_cxx_cast_qualifiers_away;
1263     return TC_Failed;
1264   }
1265 
1266   if (Paths.isAmbiguous(SrcType.getUnqualifiedType())) {
1267     // This code is analoguous to that in CheckDerivedToBaseConversion, except
1268     // that it builds the paths in reverse order.
1269     // To sum up: record all paths to the base and build a nice string from
1270     // them. Use it to spice up the error message.
1271     if (!Paths.isRecordingPaths()) {
1272       Paths.clear();
1273       Paths.setRecordingPaths(true);
1274       Self.IsDerivedFrom(DestType, SrcType, Paths);
1275     }
1276     std::string PathDisplayStr;
1277     std::set<unsigned> DisplayedPaths;
1278     for (CXXBasePaths::paths_iterator PI = Paths.begin(), PE = Paths.end();
1279          PI != PE; ++PI) {
1280       if (DisplayedPaths.insert(PI->back().SubobjectNumber).second) {
1281         // We haven't displayed a path to this particular base
1282         // class subobject yet.
1283         PathDisplayStr += "\n    ";
1284         for (CXXBasePath::const_reverse_iterator EI = PI->rbegin(),
1285                                                  EE = PI->rend();
1286              EI != EE; ++EI)
1287           PathDisplayStr += EI->Base->getType().getAsString() + " -> ";
1288         PathDisplayStr += QualType(DestType).getAsString();
1289       }
1290     }
1291 
1292     Self.Diag(OpRange.getBegin(), diag::err_ambiguous_base_to_derived_cast)
1293       << QualType(SrcType).getUnqualifiedType()
1294       << QualType(DestType).getUnqualifiedType()
1295       << PathDisplayStr << OpRange;
1296     msg = 0;
1297     return TC_Failed;
1298   }
1299 
1300   if (Paths.getDetectedVirtual() != nullptr) {
1301     QualType VirtualBase(Paths.getDetectedVirtual(), 0);
1302     Self.Diag(OpRange.getBegin(), diag::err_static_downcast_via_virtual)
1303       << OrigSrcType << OrigDestType << VirtualBase << OpRange;
1304     msg = 0;
1305     return TC_Failed;
1306   }
1307 
1308   if (!CStyle) {
1309     switch (Self.CheckBaseClassAccess(OpRange.getBegin(),
1310                                       SrcType, DestType,
1311                                       Paths.front(),
1312                                 diag::err_downcast_from_inaccessible_base)) {
1313     case Sema::AR_accessible:
1314     case Sema::AR_delayed:     // be optimistic
1315     case Sema::AR_dependent:   // be optimistic
1316       break;
1317 
1318     case Sema::AR_inaccessible:
1319       msg = 0;
1320       return TC_Failed;
1321     }
1322   }
1323 
1324   Self.BuildBasePathArray(Paths, BasePath);
1325   Kind = CK_BaseToDerived;
1326   return TC_Success;
1327 }
1328 
1329 /// TryStaticMemberPointerUpcast - Tests whether a conversion according to
1330 /// C++ 5.2.9p9 is valid:
1331 ///
1332 ///   An rvalue of type "pointer to member of D of type cv1 T" can be
1333 ///   converted to an rvalue of type "pointer to member of B of type cv2 T",
1334 ///   where B is a base class of D [...].
1335 ///
1336 TryCastResult
1337 TryStaticMemberPointerUpcast(Sema &Self, ExprResult &SrcExpr, QualType SrcType,
1338                              QualType DestType, bool CStyle,
1339                              const SourceRange &OpRange,
1340                              unsigned &msg, CastKind &Kind,
1341                              CXXCastPath &BasePath) {
1342   const MemberPointerType *DestMemPtr = DestType->getAs<MemberPointerType>();
1343   if (!DestMemPtr)
1344     return TC_NotApplicable;
1345 
1346   bool WasOverloadedFunction = false;
1347   DeclAccessPair FoundOverload;
1348   if (SrcExpr.get()->getType() == Self.Context.OverloadTy) {
1349     if (FunctionDecl *Fn
1350           = Self.ResolveAddressOfOverloadedFunction(SrcExpr.get(), DestType, false,
1351                                                     FoundOverload)) {
1352       CXXMethodDecl *M = cast<CXXMethodDecl>(Fn);
1353       SrcType = Self.Context.getMemberPointerType(Fn->getType(),
1354                       Self.Context.getTypeDeclType(M->getParent()).getTypePtr());
1355       WasOverloadedFunction = true;
1356     }
1357   }
1358 
1359   const MemberPointerType *SrcMemPtr = SrcType->getAs<MemberPointerType>();
1360   if (!SrcMemPtr) {
1361     msg = diag::err_bad_static_cast_member_pointer_nonmp;
1362     return TC_NotApplicable;
1363   }
1364 
1365   // T == T, modulo cv
1366   if (!Self.Context.hasSameUnqualifiedType(SrcMemPtr->getPointeeType(),
1367                                            DestMemPtr->getPointeeType()))
1368     return TC_NotApplicable;
1369 
1370   // B base of D
1371   QualType SrcClass(SrcMemPtr->getClass(), 0);
1372   QualType DestClass(DestMemPtr->getClass(), 0);
1373   CXXBasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/true,
1374                   /*DetectVirtual=*/true);
1375   if (Self.RequireCompleteType(OpRange.getBegin(), SrcClass, 0) ||
1376       !Self.IsDerivedFrom(SrcClass, DestClass, Paths)) {
1377     return TC_NotApplicable;
1378   }
1379 
1380   // B is a base of D. But is it an allowed base? If not, it's a hard error.
1381   if (Paths.isAmbiguous(Self.Context.getCanonicalType(DestClass))) {
1382     Paths.clear();
1383     Paths.setRecordingPaths(true);
1384     bool StillOkay = Self.IsDerivedFrom(SrcClass, DestClass, Paths);
1385     assert(StillOkay);
1386     (void)StillOkay;
1387     std::string PathDisplayStr = Self.getAmbiguousPathsDisplayString(Paths);
1388     Self.Diag(OpRange.getBegin(), diag::err_ambiguous_memptr_conv)
1389       << 1 << SrcClass << DestClass << PathDisplayStr << OpRange;
1390     msg = 0;
1391     return TC_Failed;
1392   }
1393 
1394   if (const RecordType *VBase = Paths.getDetectedVirtual()) {
1395     Self.Diag(OpRange.getBegin(), diag::err_memptr_conv_via_virtual)
1396       << SrcClass << DestClass << QualType(VBase, 0) << OpRange;
1397     msg = 0;
1398     return TC_Failed;
1399   }
1400 
1401   if (!CStyle) {
1402     switch (Self.CheckBaseClassAccess(OpRange.getBegin(),
1403                                       DestClass, SrcClass,
1404                                       Paths.front(),
1405                                       diag::err_upcast_to_inaccessible_base)) {
1406     case Sema::AR_accessible:
1407     case Sema::AR_delayed:
1408     case Sema::AR_dependent:
1409       // Optimistically assume that the delayed and dependent cases
1410       // will work out.
1411       break;
1412 
1413     case Sema::AR_inaccessible:
1414       msg = 0;
1415       return TC_Failed;
1416     }
1417   }
1418 
1419   if (WasOverloadedFunction) {
1420     // Resolve the address of the overloaded function again, this time
1421     // allowing complaints if something goes wrong.
1422     FunctionDecl *Fn = Self.ResolveAddressOfOverloadedFunction(SrcExpr.get(),
1423                                                                DestType,
1424                                                                true,
1425                                                                FoundOverload);
1426     if (!Fn) {
1427       msg = 0;
1428       return TC_Failed;
1429     }
1430 
1431     SrcExpr = Self.FixOverloadedFunctionReference(SrcExpr, FoundOverload, Fn);
1432     if (!SrcExpr.isUsable()) {
1433       msg = 0;
1434       return TC_Failed;
1435     }
1436   }
1437 
1438   Self.BuildBasePathArray(Paths, BasePath);
1439   Kind = CK_DerivedToBaseMemberPointer;
1440   return TC_Success;
1441 }
1442 
1443 /// TryStaticImplicitCast - Tests whether a conversion according to C++ 5.2.9p2
1444 /// is valid:
1445 ///
1446 ///   An expression e can be explicitly converted to a type T using a
1447 ///   @c static_cast if the declaration "T t(e);" is well-formed [...].
1448 TryCastResult
1449 TryStaticImplicitCast(Sema &Self, ExprResult &SrcExpr, QualType DestType,
1450                       Sema::CheckedConversionKind CCK,
1451                       const SourceRange &OpRange, unsigned &msg,
1452                       CastKind &Kind, bool ListInitialization) {
1453   if (DestType->isRecordType()) {
1454     if (Self.RequireCompleteType(OpRange.getBegin(), DestType,
1455                                  diag::err_bad_dynamic_cast_incomplete) ||
1456         Self.RequireNonAbstractType(OpRange.getBegin(), DestType,
1457                                     diag::err_allocation_of_abstract_type)) {
1458       msg = 0;
1459       return TC_Failed;
1460     }
1461   } else if (DestType->isMemberPointerType()) {
1462     if (Self.Context.getTargetInfo().getCXXABI().isMicrosoft()) {
1463       Self.RequireCompleteType(OpRange.getBegin(), DestType, 0);
1464     }
1465   }
1466 
1467   InitializedEntity Entity = InitializedEntity::InitializeTemporary(DestType);
1468   InitializationKind InitKind
1469     = (CCK == Sema::CCK_CStyleCast)
1470         ? InitializationKind::CreateCStyleCast(OpRange.getBegin(), OpRange,
1471                                                ListInitialization)
1472     : (CCK == Sema::CCK_FunctionalCast)
1473         ? InitializationKind::CreateFunctionalCast(OpRange, ListInitialization)
1474     : InitializationKind::CreateCast(OpRange);
1475   Expr *SrcExprRaw = SrcExpr.get();
1476   InitializationSequence InitSeq(Self, Entity, InitKind, SrcExprRaw);
1477 
1478   // At this point of CheckStaticCast, if the destination is a reference,
1479   // or the expression is an overload expression this has to work.
1480   // There is no other way that works.
1481   // On the other hand, if we're checking a C-style cast, we've still got
1482   // the reinterpret_cast way.
1483   bool CStyle
1484     = (CCK == Sema::CCK_CStyleCast || CCK == Sema::CCK_FunctionalCast);
1485   if (InitSeq.Failed() && (CStyle || !DestType->isReferenceType()))
1486     return TC_NotApplicable;
1487 
1488   ExprResult Result = InitSeq.Perform(Self, Entity, InitKind, SrcExprRaw);
1489   if (Result.isInvalid()) {
1490     msg = 0;
1491     return TC_Failed;
1492   }
1493 
1494   if (InitSeq.isConstructorInitialization())
1495     Kind = CK_ConstructorConversion;
1496   else
1497     Kind = CK_NoOp;
1498 
1499   SrcExpr = Result;
1500   return TC_Success;
1501 }
1502 
1503 /// TryConstCast - See if a const_cast from source to destination is allowed,
1504 /// and perform it if it is.
1505 static TryCastResult TryConstCast(Sema &Self, ExprResult &SrcExpr,
1506                                   QualType DestType, bool CStyle,
1507                                   unsigned &msg) {
1508   DestType = Self.Context.getCanonicalType(DestType);
1509   QualType SrcType = SrcExpr.get()->getType();
1510   bool NeedToMaterializeTemporary = false;
1511 
1512   if (const ReferenceType *DestTypeTmp =DestType->getAs<ReferenceType>()) {
1513     // C++11 5.2.11p4:
1514     //   if a pointer to T1 can be explicitly converted to the type "pointer to
1515     //   T2" using a const_cast, then the following conversions can also be
1516     //   made:
1517     //    -- an lvalue of type T1 can be explicitly converted to an lvalue of
1518     //       type T2 using the cast const_cast<T2&>;
1519     //    -- a glvalue of type T1 can be explicitly converted to an xvalue of
1520     //       type T2 using the cast const_cast<T2&&>; and
1521     //    -- if T1 is a class type, a prvalue of type T1 can be explicitly
1522     //       converted to an xvalue of type T2 using the cast const_cast<T2&&>.
1523 
1524     if (isa<LValueReferenceType>(DestTypeTmp) && !SrcExpr.get()->isLValue()) {
1525       // Cannot const_cast non-lvalue to lvalue reference type. But if this
1526       // is C-style, static_cast might find a way, so we simply suggest a
1527       // message and tell the parent to keep searching.
1528       msg = diag::err_bad_cxx_cast_rvalue;
1529       return TC_NotApplicable;
1530     }
1531 
1532     if (isa<RValueReferenceType>(DestTypeTmp) && SrcExpr.get()->isRValue()) {
1533       if (!SrcType->isRecordType()) {
1534         // Cannot const_cast non-class prvalue to rvalue reference type. But if
1535         // this is C-style, static_cast can do this.
1536         msg = diag::err_bad_cxx_cast_rvalue;
1537         return TC_NotApplicable;
1538       }
1539 
1540       // Materialize the class prvalue so that the const_cast can bind a
1541       // reference to it.
1542       NeedToMaterializeTemporary = true;
1543     }
1544 
1545     // It's not completely clear under the standard whether we can
1546     // const_cast bit-field gl-values.  Doing so would not be
1547     // intrinsically complicated, but for now, we say no for
1548     // consistency with other compilers and await the word of the
1549     // committee.
1550     if (SrcExpr.get()->refersToBitField()) {
1551       msg = diag::err_bad_cxx_cast_bitfield;
1552       return TC_NotApplicable;
1553     }
1554 
1555     DestType = Self.Context.getPointerType(DestTypeTmp->getPointeeType());
1556     SrcType = Self.Context.getPointerType(SrcType);
1557   }
1558 
1559   // C++ 5.2.11p5: For a const_cast involving pointers to data members [...]
1560   //   the rules for const_cast are the same as those used for pointers.
1561 
1562   if (!DestType->isPointerType() &&
1563       !DestType->isMemberPointerType() &&
1564       !DestType->isObjCObjectPointerType()) {
1565     // Cannot cast to non-pointer, non-reference type. Note that, if DestType
1566     // was a reference type, we converted it to a pointer above.
1567     // The status of rvalue references isn't entirely clear, but it looks like
1568     // conversion to them is simply invalid.
1569     // C++ 5.2.11p3: For two pointer types [...]
1570     if (!CStyle)
1571       msg = diag::err_bad_const_cast_dest;
1572     return TC_NotApplicable;
1573   }
1574   if (DestType->isFunctionPointerType() ||
1575       DestType->isMemberFunctionPointerType()) {
1576     // Cannot cast direct function pointers.
1577     // C++ 5.2.11p2: [...] where T is any object type or the void type [...]
1578     // T is the ultimate pointee of source and target type.
1579     if (!CStyle)
1580       msg = diag::err_bad_const_cast_dest;
1581     return TC_NotApplicable;
1582   }
1583   SrcType = Self.Context.getCanonicalType(SrcType);
1584 
1585   // Unwrap the pointers. Ignore qualifiers. Terminate early if the types are
1586   // completely equal.
1587   // C++ 5.2.11p3 describes the core semantics of const_cast. All cv specifiers
1588   // in multi-level pointers may change, but the level count must be the same,
1589   // as must be the final pointee type.
1590   while (SrcType != DestType &&
1591          Self.Context.UnwrapSimilarPointerTypes(SrcType, DestType)) {
1592     Qualifiers SrcQuals, DestQuals;
1593     SrcType = Self.Context.getUnqualifiedArrayType(SrcType, SrcQuals);
1594     DestType = Self.Context.getUnqualifiedArrayType(DestType, DestQuals);
1595 
1596     // const_cast is permitted to strip cvr-qualifiers, only. Make sure that
1597     // the other qualifiers (e.g., address spaces) are identical.
1598     SrcQuals.removeCVRQualifiers();
1599     DestQuals.removeCVRQualifiers();
1600     if (SrcQuals != DestQuals)
1601       return TC_NotApplicable;
1602   }
1603 
1604   // Since we're dealing in canonical types, the remainder must be the same.
1605   if (SrcType != DestType)
1606     return TC_NotApplicable;
1607 
1608   if (NeedToMaterializeTemporary)
1609     // This is a const_cast from a class prvalue to an rvalue reference type.
1610     // Materialize a temporary to store the result of the conversion.
1611     SrcExpr = new (Self.Context) MaterializeTemporaryExpr(
1612         SrcType, SrcExpr.get(), /*IsLValueReference*/ false);
1613 
1614   return TC_Success;
1615 }
1616 
1617 // Checks for undefined behavior in reinterpret_cast.
1618 // The cases that is checked for is:
1619 // *reinterpret_cast<T*>(&a)
1620 // reinterpret_cast<T&>(a)
1621 // where accessing 'a' as type 'T' will result in undefined behavior.
1622 void Sema::CheckCompatibleReinterpretCast(QualType SrcType, QualType DestType,
1623                                           bool IsDereference,
1624                                           SourceRange Range) {
1625   unsigned DiagID = IsDereference ?
1626                         diag::warn_pointer_indirection_from_incompatible_type :
1627                         diag::warn_undefined_reinterpret_cast;
1628 
1629   if (Diags.isIgnored(DiagID, Range.getBegin()))
1630     return;
1631 
1632   QualType SrcTy, DestTy;
1633   if (IsDereference) {
1634     if (!SrcType->getAs<PointerType>() || !DestType->getAs<PointerType>()) {
1635       return;
1636     }
1637     SrcTy = SrcType->getPointeeType();
1638     DestTy = DestType->getPointeeType();
1639   } else {
1640     if (!DestType->getAs<ReferenceType>()) {
1641       return;
1642     }
1643     SrcTy = SrcType;
1644     DestTy = DestType->getPointeeType();
1645   }
1646 
1647   // Cast is compatible if the types are the same.
1648   if (Context.hasSameUnqualifiedType(DestTy, SrcTy)) {
1649     return;
1650   }
1651   // or one of the types is a char or void type
1652   if (DestTy->isAnyCharacterType() || DestTy->isVoidType() ||
1653       SrcTy->isAnyCharacterType() || SrcTy->isVoidType()) {
1654     return;
1655   }
1656   // or one of the types is a tag type.
1657   if (SrcTy->getAs<TagType>() || DestTy->getAs<TagType>()) {
1658     return;
1659   }
1660 
1661   // FIXME: Scoped enums?
1662   if ((SrcTy->isUnsignedIntegerType() && DestTy->isSignedIntegerType()) ||
1663       (SrcTy->isSignedIntegerType() && DestTy->isUnsignedIntegerType())) {
1664     if (Context.getTypeSize(DestTy) == Context.getTypeSize(SrcTy)) {
1665       return;
1666     }
1667   }
1668 
1669   Diag(Range.getBegin(), DiagID) << SrcType << DestType << Range;
1670 }
1671 
1672 static void DiagnoseCastOfObjCSEL(Sema &Self, const ExprResult &SrcExpr,
1673                                   QualType DestType) {
1674   QualType SrcType = SrcExpr.get()->getType();
1675   if (Self.Context.hasSameType(SrcType, DestType))
1676     return;
1677   if (const PointerType *SrcPtrTy = SrcType->getAs<PointerType>())
1678     if (SrcPtrTy->isObjCSelType()) {
1679       QualType DT = DestType;
1680       if (isa<PointerType>(DestType))
1681         DT = DestType->getPointeeType();
1682       if (!DT.getUnqualifiedType()->isVoidType())
1683         Self.Diag(SrcExpr.get()->getExprLoc(),
1684                   diag::warn_cast_pointer_from_sel)
1685         << SrcType << DestType << SrcExpr.get()->getSourceRange();
1686     }
1687 }
1688 
1689 static void checkIntToPointerCast(bool CStyle, SourceLocation Loc,
1690                                   const Expr *SrcExpr, QualType DestType,
1691                                   Sema &Self) {
1692   QualType SrcType = SrcExpr->getType();
1693 
1694   // Not warning on reinterpret_cast, boolean, constant expressions, etc
1695   // are not explicit design choices, but consistent with GCC's behavior.
1696   // Feel free to modify them if you've reason/evidence for an alternative.
1697   if (CStyle && SrcType->isIntegralType(Self.Context)
1698       && !SrcType->isBooleanType()
1699       && !SrcType->isEnumeralType()
1700       && !SrcExpr->isIntegerConstantExpr(Self.Context)
1701       && Self.Context.getTypeSize(DestType) >
1702          Self.Context.getTypeSize(SrcType)) {
1703     // Separate between casts to void* and non-void* pointers.
1704     // Some APIs use (abuse) void* for something like a user context,
1705     // and often that value is an integer even if it isn't a pointer itself.
1706     // Having a separate warning flag allows users to control the warning
1707     // for their workflow.
1708     unsigned Diag = DestType->isVoidPointerType() ?
1709                       diag::warn_int_to_void_pointer_cast
1710                     : diag::warn_int_to_pointer_cast;
1711     Self.Diag(Loc, Diag) << SrcType << DestType;
1712   }
1713 }
1714 
1715 static TryCastResult TryReinterpretCast(Sema &Self, ExprResult &SrcExpr,
1716                                         QualType DestType, bool CStyle,
1717                                         const SourceRange &OpRange,
1718                                         unsigned &msg,
1719                                         CastKind &Kind) {
1720   bool IsLValueCast = false;
1721 
1722   DestType = Self.Context.getCanonicalType(DestType);
1723   QualType SrcType = SrcExpr.get()->getType();
1724 
1725   // Is the source an overloaded name? (i.e. &foo)
1726   // If so, reinterpret_cast can not help us here (13.4, p1, bullet 5) ...
1727   if (SrcType == Self.Context.OverloadTy) {
1728     // ... unless foo<int> resolves to an lvalue unambiguously.
1729     // TODO: what if this fails because of DiagnoseUseOfDecl or something
1730     // like it?
1731     ExprResult SingleFunctionExpr = SrcExpr;
1732     if (Self.ResolveAndFixSingleFunctionTemplateSpecialization(
1733           SingleFunctionExpr,
1734           Expr::getValueKindForType(DestType) == VK_RValue // Convert Fun to Ptr
1735         ) && SingleFunctionExpr.isUsable()) {
1736       SrcExpr = SingleFunctionExpr;
1737       SrcType = SrcExpr.get()->getType();
1738     } else {
1739       return TC_NotApplicable;
1740     }
1741   }
1742 
1743   if (const ReferenceType *DestTypeTmp = DestType->getAs<ReferenceType>()) {
1744     if (!SrcExpr.get()->isGLValue()) {
1745       // Cannot cast non-glvalue to (lvalue or rvalue) reference type. See the
1746       // similar comment in const_cast.
1747       msg = diag::err_bad_cxx_cast_rvalue;
1748       return TC_NotApplicable;
1749     }
1750 
1751     if (!CStyle) {
1752       Self.CheckCompatibleReinterpretCast(SrcType, DestType,
1753                                           /*isDereference=*/false, OpRange);
1754     }
1755 
1756     // C++ 5.2.10p10: [...] a reference cast reinterpret_cast<T&>(x) has the
1757     //   same effect as the conversion *reinterpret_cast<T*>(&x) with the
1758     //   built-in & and * operators.
1759 
1760     const char *inappropriate = nullptr;
1761     switch (SrcExpr.get()->getObjectKind()) {
1762     case OK_Ordinary:
1763       break;
1764     case OK_BitField:        inappropriate = "bit-field";           break;
1765     case OK_VectorComponent: inappropriate = "vector element";      break;
1766     case OK_ObjCProperty:    inappropriate = "property expression"; break;
1767     case OK_ObjCSubscript:   inappropriate = "container subscripting expression";
1768                              break;
1769     }
1770     if (inappropriate) {
1771       Self.Diag(OpRange.getBegin(), diag::err_bad_reinterpret_cast_reference)
1772           << inappropriate << DestType
1773           << OpRange << SrcExpr.get()->getSourceRange();
1774       msg = 0; SrcExpr = ExprError();
1775       return TC_NotApplicable;
1776     }
1777 
1778     // This code does this transformation for the checked types.
1779     DestType = Self.Context.getPointerType(DestTypeTmp->getPointeeType());
1780     SrcType = Self.Context.getPointerType(SrcType);
1781 
1782     IsLValueCast = true;
1783   }
1784 
1785   // Canonicalize source for comparison.
1786   SrcType = Self.Context.getCanonicalType(SrcType);
1787 
1788   const MemberPointerType *DestMemPtr = DestType->getAs<MemberPointerType>(),
1789                           *SrcMemPtr = SrcType->getAs<MemberPointerType>();
1790   if (DestMemPtr && SrcMemPtr) {
1791     // C++ 5.2.10p9: An rvalue of type "pointer to member of X of type T1"
1792     //   can be explicitly converted to an rvalue of type "pointer to member
1793     //   of Y of type T2" if T1 and T2 are both function types or both object
1794     //   types.
1795     if (DestMemPtr->getPointeeType()->isFunctionType() !=
1796         SrcMemPtr->getPointeeType()->isFunctionType())
1797       return TC_NotApplicable;
1798 
1799     // C++ 5.2.10p2: The reinterpret_cast operator shall not cast away
1800     //   constness.
1801     // A reinterpret_cast followed by a const_cast can, though, so in C-style,
1802     // we accept it.
1803     if (CastsAwayConstness(Self, SrcType, DestType, /*CheckCVR=*/!CStyle,
1804                            /*CheckObjCLifetime=*/CStyle)) {
1805       msg = diag::err_bad_cxx_cast_qualifiers_away;
1806       return TC_Failed;
1807     }
1808 
1809     if (Self.Context.getTargetInfo().getCXXABI().isMicrosoft()) {
1810       // We need to determine the inheritance model that the class will use if
1811       // haven't yet.
1812       Self.RequireCompleteType(OpRange.getBegin(), SrcType, 0);
1813       Self.RequireCompleteType(OpRange.getBegin(), DestType, 0);
1814     }
1815 
1816     // Don't allow casting between member pointers of different sizes.
1817     if (Self.Context.getTypeSize(DestMemPtr) !=
1818         Self.Context.getTypeSize(SrcMemPtr)) {
1819       msg = diag::err_bad_cxx_cast_member_pointer_size;
1820       return TC_Failed;
1821     }
1822 
1823     // A valid member pointer cast.
1824     assert(!IsLValueCast);
1825     Kind = CK_ReinterpretMemberPointer;
1826     return TC_Success;
1827   }
1828 
1829   // See below for the enumeral issue.
1830   if (SrcType->isNullPtrType() && DestType->isIntegralType(Self.Context)) {
1831     // C++0x 5.2.10p4: A pointer can be explicitly converted to any integral
1832     //   type large enough to hold it. A value of std::nullptr_t can be
1833     //   converted to an integral type; the conversion has the same meaning
1834     //   and validity as a conversion of (void*)0 to the integral type.
1835     if (Self.Context.getTypeSize(SrcType) >
1836         Self.Context.getTypeSize(DestType)) {
1837       msg = diag::err_bad_reinterpret_cast_small_int;
1838       return TC_Failed;
1839     }
1840     Kind = CK_PointerToIntegral;
1841     return TC_Success;
1842   }
1843 
1844   bool destIsVector = DestType->isVectorType();
1845   bool srcIsVector = SrcType->isVectorType();
1846   if (srcIsVector || destIsVector) {
1847     // FIXME: Should this also apply to floating point types?
1848     bool srcIsScalar = SrcType->isIntegralType(Self.Context);
1849     bool destIsScalar = DestType->isIntegralType(Self.Context);
1850 
1851     // Check if this is a cast between a vector and something else.
1852     if (!(srcIsScalar && destIsVector) && !(srcIsVector && destIsScalar) &&
1853         !(srcIsVector && destIsVector))
1854       return TC_NotApplicable;
1855 
1856     // If both types have the same size, we can successfully cast.
1857     if (Self.Context.getTypeSize(SrcType)
1858           == Self.Context.getTypeSize(DestType)) {
1859       Kind = CK_BitCast;
1860       return TC_Success;
1861     }
1862 
1863     if (destIsScalar)
1864       msg = diag::err_bad_cxx_cast_vector_to_scalar_different_size;
1865     else if (srcIsScalar)
1866       msg = diag::err_bad_cxx_cast_scalar_to_vector_different_size;
1867     else
1868       msg = diag::err_bad_cxx_cast_vector_to_vector_different_size;
1869 
1870     return TC_Failed;
1871   }
1872 
1873   if (SrcType == DestType) {
1874     // C++ 5.2.10p2 has a note that mentions that, subject to all other
1875     // restrictions, a cast to the same type is allowed so long as it does not
1876     // cast away constness. In C++98, the intent was not entirely clear here,
1877     // since all other paragraphs explicitly forbid casts to the same type.
1878     // C++11 clarifies this case with p2.
1879     //
1880     // The only allowed types are: integral, enumeration, pointer, or
1881     // pointer-to-member types.  We also won't restrict Obj-C pointers either.
1882     Kind = CK_NoOp;
1883     TryCastResult Result = TC_NotApplicable;
1884     if (SrcType->isIntegralOrEnumerationType() ||
1885         SrcType->isAnyPointerType() ||
1886         SrcType->isMemberPointerType() ||
1887         SrcType->isBlockPointerType()) {
1888       Result = TC_Success;
1889     }
1890     return Result;
1891   }
1892 
1893   bool destIsPtr = DestType->isAnyPointerType() ||
1894                    DestType->isBlockPointerType();
1895   bool srcIsPtr = SrcType->isAnyPointerType() ||
1896                   SrcType->isBlockPointerType();
1897   if (!destIsPtr && !srcIsPtr) {
1898     // Except for std::nullptr_t->integer and lvalue->reference, which are
1899     // handled above, at least one of the two arguments must be a pointer.
1900     return TC_NotApplicable;
1901   }
1902 
1903   if (DestType->isIntegralType(Self.Context)) {
1904     assert(srcIsPtr && "One type must be a pointer");
1905     // C++ 5.2.10p4: A pointer can be explicitly converted to any integral
1906     //   type large enough to hold it; except in Microsoft mode, where the
1907     //   integral type size doesn't matter (except we don't allow bool).
1908     bool MicrosoftException = Self.getLangOpts().MicrosoftExt &&
1909                               !DestType->isBooleanType();
1910     if ((Self.Context.getTypeSize(SrcType) >
1911          Self.Context.getTypeSize(DestType)) &&
1912          !MicrosoftException) {
1913       msg = diag::err_bad_reinterpret_cast_small_int;
1914       return TC_Failed;
1915     }
1916     Kind = CK_PointerToIntegral;
1917     return TC_Success;
1918   }
1919 
1920   if (SrcType->isIntegralOrEnumerationType()) {
1921     assert(destIsPtr && "One type must be a pointer");
1922     checkIntToPointerCast(CStyle, OpRange.getBegin(), SrcExpr.get(), DestType,
1923                           Self);
1924     // C++ 5.2.10p5: A value of integral or enumeration type can be explicitly
1925     //   converted to a pointer.
1926     // C++ 5.2.10p9: [Note: ...a null pointer constant of integral type is not
1927     //   necessarily converted to a null pointer value.]
1928     Kind = CK_IntegralToPointer;
1929     return TC_Success;
1930   }
1931 
1932   if (!destIsPtr || !srcIsPtr) {
1933     // With the valid non-pointer conversions out of the way, we can be even
1934     // more stringent.
1935     return TC_NotApplicable;
1936   }
1937 
1938   // C++ 5.2.10p2: The reinterpret_cast operator shall not cast away constness.
1939   // The C-style cast operator can.
1940   if (CastsAwayConstness(Self, SrcType, DestType, /*CheckCVR=*/!CStyle,
1941                          /*CheckObjCLifetime=*/CStyle)) {
1942     msg = diag::err_bad_cxx_cast_qualifiers_away;
1943     return TC_Failed;
1944   }
1945 
1946   // Cannot convert between block pointers and Objective-C object pointers.
1947   if ((SrcType->isBlockPointerType() && DestType->isObjCObjectPointerType()) ||
1948       (DestType->isBlockPointerType() && SrcType->isObjCObjectPointerType()))
1949     return TC_NotApplicable;
1950 
1951   if (IsLValueCast) {
1952     Kind = CK_LValueBitCast;
1953   } else if (DestType->isObjCObjectPointerType()) {
1954     Kind = Self.PrepareCastToObjCObjectPointer(SrcExpr);
1955   } else if (DestType->isBlockPointerType()) {
1956     if (!SrcType->isBlockPointerType()) {
1957       Kind = CK_AnyPointerToBlockPointerCast;
1958     } else {
1959       Kind = CK_BitCast;
1960     }
1961   } else {
1962     Kind = CK_BitCast;
1963   }
1964 
1965   // Any pointer can be cast to an Objective-C pointer type with a C-style
1966   // cast.
1967   if (CStyle && DestType->isObjCObjectPointerType()) {
1968     return TC_Success;
1969   }
1970   if (CStyle)
1971     DiagnoseCastOfObjCSEL(Self, SrcExpr, DestType);
1972 
1973   // Not casting away constness, so the only remaining check is for compatible
1974   // pointer categories.
1975 
1976   if (SrcType->isFunctionPointerType()) {
1977     if (DestType->isFunctionPointerType()) {
1978       // C++ 5.2.10p6: A pointer to a function can be explicitly converted to
1979       // a pointer to a function of a different type.
1980       return TC_Success;
1981     }
1982 
1983     // C++0x 5.2.10p8: Converting a pointer to a function into a pointer to
1984     //   an object type or vice versa is conditionally-supported.
1985     // Compilers support it in C++03 too, though, because it's necessary for
1986     // casting the return value of dlsym() and GetProcAddress().
1987     // FIXME: Conditionally-supported behavior should be configurable in the
1988     // TargetInfo or similar.
1989     Self.Diag(OpRange.getBegin(),
1990               Self.getLangOpts().CPlusPlus11 ?
1991                 diag::warn_cxx98_compat_cast_fn_obj : diag::ext_cast_fn_obj)
1992       << OpRange;
1993     return TC_Success;
1994   }
1995 
1996   if (DestType->isFunctionPointerType()) {
1997     // See above.
1998     Self.Diag(OpRange.getBegin(),
1999               Self.getLangOpts().CPlusPlus11 ?
2000                 diag::warn_cxx98_compat_cast_fn_obj : diag::ext_cast_fn_obj)
2001       << OpRange;
2002     return TC_Success;
2003   }
2004 
2005   // C++ 5.2.10p7: A pointer to an object can be explicitly converted to
2006   //   a pointer to an object of different type.
2007   // Void pointers are not specified, but supported by every compiler out there.
2008   // So we finish by allowing everything that remains - it's got to be two
2009   // object pointers.
2010   return TC_Success;
2011 }
2012 
2013 void CastOperation::CheckCXXCStyleCast(bool FunctionalStyle,
2014                                        bool ListInitialization) {
2015   // Handle placeholders.
2016   if (isPlaceholder()) {
2017     // C-style casts can resolve __unknown_any types.
2018     if (claimPlaceholder(BuiltinType::UnknownAny)) {
2019       SrcExpr = Self.checkUnknownAnyCast(DestRange, DestType,
2020                                          SrcExpr.get(), Kind,
2021                                          ValueKind, BasePath);
2022       return;
2023     }
2024 
2025     checkNonOverloadPlaceholders();
2026     if (SrcExpr.isInvalid())
2027       return;
2028   }
2029 
2030   // C++ 5.2.9p4: Any expression can be explicitly converted to type "cv void".
2031   // This test is outside everything else because it's the only case where
2032   // a non-lvalue-reference target type does not lead to decay.
2033   if (DestType->isVoidType()) {
2034     Kind = CK_ToVoid;
2035 
2036     if (claimPlaceholder(BuiltinType::Overload)) {
2037       Self.ResolveAndFixSingleFunctionTemplateSpecialization(
2038                   SrcExpr, /* Decay Function to ptr */ false,
2039                   /* Complain */ true, DestRange, DestType,
2040                   diag::err_bad_cstyle_cast_overload);
2041       if (SrcExpr.isInvalid())
2042         return;
2043     }
2044 
2045     SrcExpr = Self.IgnoredValueConversions(SrcExpr.get());
2046     return;
2047   }
2048 
2049   // If the type is dependent, we won't do any other semantic analysis now.
2050   if (DestType->isDependentType() || SrcExpr.get()->isTypeDependent() ||
2051       SrcExpr.get()->isValueDependent()) {
2052     assert(Kind == CK_Dependent);
2053     return;
2054   }
2055 
2056   if (ValueKind == VK_RValue && !DestType->isRecordType() &&
2057       !isPlaceholder(BuiltinType::Overload)) {
2058     SrcExpr = Self.DefaultFunctionArrayLvalueConversion(SrcExpr.get());
2059     if (SrcExpr.isInvalid())
2060       return;
2061   }
2062 
2063   // AltiVec vector initialization with a single literal.
2064   if (const VectorType *vecTy = DestType->getAs<VectorType>())
2065     if (vecTy->getVectorKind() == VectorType::AltiVecVector
2066         && (SrcExpr.get()->getType()->isIntegerType()
2067             || SrcExpr.get()->getType()->isFloatingType())) {
2068       Kind = CK_VectorSplat;
2069       return;
2070     }
2071 
2072   // C++ [expr.cast]p5: The conversions performed by
2073   //   - a const_cast,
2074   //   - a static_cast,
2075   //   - a static_cast followed by a const_cast,
2076   //   - a reinterpret_cast, or
2077   //   - a reinterpret_cast followed by a const_cast,
2078   //   can be performed using the cast notation of explicit type conversion.
2079   //   [...] If a conversion can be interpreted in more than one of the ways
2080   //   listed above, the interpretation that appears first in the list is used,
2081   //   even if a cast resulting from that interpretation is ill-formed.
2082   // In plain language, this means trying a const_cast ...
2083   unsigned msg = diag::err_bad_cxx_cast_generic;
2084   TryCastResult tcr = TryConstCast(Self, SrcExpr, DestType,
2085                                    /*CStyle*/true, msg);
2086   if (SrcExpr.isInvalid())
2087     return;
2088   if (tcr == TC_Success)
2089     Kind = CK_NoOp;
2090 
2091   Sema::CheckedConversionKind CCK
2092     = FunctionalStyle? Sema::CCK_FunctionalCast
2093                      : Sema::CCK_CStyleCast;
2094   if (tcr == TC_NotApplicable) {
2095     // ... or if that is not possible, a static_cast, ignoring const, ...
2096     tcr = TryStaticCast(Self, SrcExpr, DestType, CCK, OpRange,
2097                         msg, Kind, BasePath, ListInitialization);
2098     if (SrcExpr.isInvalid())
2099       return;
2100 
2101     if (tcr == TC_NotApplicable) {
2102       // ... and finally a reinterpret_cast, ignoring const.
2103       tcr = TryReinterpretCast(Self, SrcExpr, DestType, /*CStyle*/true,
2104                                OpRange, msg, Kind);
2105       if (SrcExpr.isInvalid())
2106         return;
2107     }
2108   }
2109 
2110   if (Self.getLangOpts().ObjCAutoRefCount && tcr == TC_Success)
2111     checkObjCARCConversion(CCK);
2112 
2113   if (tcr != TC_Success && msg != 0) {
2114     if (SrcExpr.get()->getType() == Self.Context.OverloadTy) {
2115       DeclAccessPair Found;
2116       FunctionDecl *Fn = Self.ResolveAddressOfOverloadedFunction(SrcExpr.get(),
2117                                 DestType,
2118                                 /*Complain*/ true,
2119                                 Found);
2120       if (Fn) {
2121         // If DestType is a function type (not to be confused with the function
2122         // pointer type), it will be possible to resolve the function address,
2123         // but the type cast should be considered as failure.
2124         OverloadExpr *OE = OverloadExpr::find(SrcExpr.get()).Expression;
2125         Self.Diag(OpRange.getBegin(), diag::err_bad_cstyle_cast_overload)
2126           << OE->getName() << DestType << OpRange
2127           << OE->getQualifierLoc().getSourceRange();
2128         Self.NoteAllOverloadCandidates(SrcExpr.get());
2129       }
2130     } else {
2131       diagnoseBadCast(Self, msg, (FunctionalStyle ? CT_Functional : CT_CStyle),
2132                       OpRange, SrcExpr.get(), DestType, ListInitialization);
2133     }
2134   } else if (Kind == CK_BitCast) {
2135     checkCastAlign();
2136   }
2137 
2138   // Clear out SrcExpr if there was a fatal error.
2139   if (tcr != TC_Success)
2140     SrcExpr = ExprError();
2141 }
2142 
2143 /// DiagnoseBadFunctionCast - Warn whenever a function call is cast to a
2144 ///  non-matching type. Such as enum function call to int, int call to
2145 /// pointer; etc. Cast to 'void' is an exception.
2146 static void DiagnoseBadFunctionCast(Sema &Self, const ExprResult &SrcExpr,
2147                                   QualType DestType) {
2148   if (Self.Diags.isIgnored(diag::warn_bad_function_cast,
2149                            SrcExpr.get()->getExprLoc()))
2150     return;
2151 
2152   if (!isa<CallExpr>(SrcExpr.get()))
2153     return;
2154 
2155   QualType SrcType = SrcExpr.get()->getType();
2156   if (DestType.getUnqualifiedType()->isVoidType())
2157     return;
2158   if ((SrcType->isAnyPointerType() || SrcType->isBlockPointerType())
2159       && (DestType->isAnyPointerType() || DestType->isBlockPointerType()))
2160     return;
2161   if (SrcType->isIntegerType() && DestType->isIntegerType() &&
2162       (SrcType->isBooleanType() == DestType->isBooleanType()) &&
2163       (SrcType->isEnumeralType() == DestType->isEnumeralType()))
2164     return;
2165   if (SrcType->isRealFloatingType() && DestType->isRealFloatingType())
2166     return;
2167   if (SrcType->isEnumeralType() && DestType->isEnumeralType())
2168     return;
2169   if (SrcType->isComplexType() && DestType->isComplexType())
2170     return;
2171   if (SrcType->isComplexIntegerType() && DestType->isComplexIntegerType())
2172     return;
2173 
2174   Self.Diag(SrcExpr.get()->getExprLoc(),
2175             diag::warn_bad_function_cast)
2176             << SrcType << DestType << SrcExpr.get()->getSourceRange();
2177 }
2178 
2179 /// Check the semantics of a C-style cast operation, in C.
2180 void CastOperation::CheckCStyleCast() {
2181   assert(!Self.getLangOpts().CPlusPlus);
2182 
2183   // C-style casts can resolve __unknown_any types.
2184   if (claimPlaceholder(BuiltinType::UnknownAny)) {
2185     SrcExpr = Self.checkUnknownAnyCast(DestRange, DestType,
2186                                        SrcExpr.get(), Kind,
2187                                        ValueKind, BasePath);
2188     return;
2189   }
2190 
2191   // C99 6.5.4p2: the cast type needs to be void or scalar and the expression
2192   // type needs to be scalar.
2193   if (DestType->isVoidType()) {
2194     // We don't necessarily do lvalue-to-rvalue conversions on this.
2195     SrcExpr = Self.IgnoredValueConversions(SrcExpr.get());
2196     if (SrcExpr.isInvalid())
2197       return;
2198 
2199     // Cast to void allows any expr type.
2200     Kind = CK_ToVoid;
2201     return;
2202   }
2203 
2204   SrcExpr = Self.DefaultFunctionArrayLvalueConversion(SrcExpr.get());
2205   if (SrcExpr.isInvalid())
2206     return;
2207   QualType SrcType = SrcExpr.get()->getType();
2208 
2209   assert(!SrcType->isPlaceholderType());
2210 
2211   // OpenCL v1 s6.5: Casting a pointer to address space A to a pointer to
2212   // address space B is illegal.
2213   if (Self.getLangOpts().OpenCL && DestType->isPointerType() &&
2214       SrcType->isPointerType()) {
2215     const PointerType *DestPtr = DestType->getAs<PointerType>();
2216     if (!DestPtr->isAddressSpaceOverlapping(*SrcType->getAs<PointerType>())) {
2217       Self.Diag(OpRange.getBegin(),
2218                 diag::err_typecheck_incompatible_address_space)
2219           << SrcType << DestType << Sema::AA_Casting
2220           << SrcExpr.get()->getSourceRange();
2221       SrcExpr = ExprError();
2222       return;
2223     }
2224   }
2225 
2226   if (Self.RequireCompleteType(OpRange.getBegin(), DestType,
2227                                diag::err_typecheck_cast_to_incomplete)) {
2228     SrcExpr = ExprError();
2229     return;
2230   }
2231 
2232   if (!DestType->isScalarType() && !DestType->isVectorType()) {
2233     const RecordType *DestRecordTy = DestType->getAs<RecordType>();
2234 
2235     if (DestRecordTy && Self.Context.hasSameUnqualifiedType(DestType, SrcType)){
2236       // GCC struct/union extension: allow cast to self.
2237       Self.Diag(OpRange.getBegin(), diag::ext_typecheck_cast_nonscalar)
2238         << DestType << SrcExpr.get()->getSourceRange();
2239       Kind = CK_NoOp;
2240       return;
2241     }
2242 
2243     // GCC's cast to union extension.
2244     if (DestRecordTy && DestRecordTy->getDecl()->isUnion()) {
2245       RecordDecl *RD = DestRecordTy->getDecl();
2246       RecordDecl::field_iterator Field, FieldEnd;
2247       for (Field = RD->field_begin(), FieldEnd = RD->field_end();
2248            Field != FieldEnd; ++Field) {
2249         if (Self.Context.hasSameUnqualifiedType(Field->getType(), SrcType) &&
2250             !Field->isUnnamedBitfield()) {
2251           Self.Diag(OpRange.getBegin(), diag::ext_typecheck_cast_to_union)
2252             << SrcExpr.get()->getSourceRange();
2253           break;
2254         }
2255       }
2256       if (Field == FieldEnd) {
2257         Self.Diag(OpRange.getBegin(), diag::err_typecheck_cast_to_union_no_type)
2258           << SrcType << SrcExpr.get()->getSourceRange();
2259         SrcExpr = ExprError();
2260         return;
2261       }
2262       Kind = CK_ToUnion;
2263       return;
2264     }
2265 
2266     // Reject any other conversions to non-scalar types.
2267     Self.Diag(OpRange.getBegin(), diag::err_typecheck_cond_expect_scalar)
2268       << DestType << SrcExpr.get()->getSourceRange();
2269     SrcExpr = ExprError();
2270     return;
2271   }
2272 
2273   // The type we're casting to is known to be a scalar or vector.
2274 
2275   // Require the operand to be a scalar or vector.
2276   if (!SrcType->isScalarType() && !SrcType->isVectorType()) {
2277     Self.Diag(SrcExpr.get()->getExprLoc(),
2278               diag::err_typecheck_expect_scalar_operand)
2279       << SrcType << SrcExpr.get()->getSourceRange();
2280     SrcExpr = ExprError();
2281     return;
2282   }
2283 
2284   if (DestType->isExtVectorType()) {
2285     SrcExpr = Self.CheckExtVectorCast(OpRange, DestType, SrcExpr.get(), Kind);
2286     return;
2287   }
2288 
2289   if (const VectorType *DestVecTy = DestType->getAs<VectorType>()) {
2290     if (DestVecTy->getVectorKind() == VectorType::AltiVecVector &&
2291           (SrcType->isIntegerType() || SrcType->isFloatingType())) {
2292       Kind = CK_VectorSplat;
2293     } else if (Self.CheckVectorCast(OpRange, DestType, SrcType, Kind)) {
2294       SrcExpr = ExprError();
2295     }
2296     return;
2297   }
2298 
2299   if (SrcType->isVectorType()) {
2300     if (Self.CheckVectorCast(OpRange, SrcType, DestType, Kind))
2301       SrcExpr = ExprError();
2302     return;
2303   }
2304 
2305   // The source and target types are both scalars, i.e.
2306   //   - arithmetic types (fundamental, enum, and complex)
2307   //   - all kinds of pointers
2308   // Note that member pointers were filtered out with C++, above.
2309 
2310   if (isa<ObjCSelectorExpr>(SrcExpr.get())) {
2311     Self.Diag(SrcExpr.get()->getExprLoc(), diag::err_cast_selector_expr);
2312     SrcExpr = ExprError();
2313     return;
2314   }
2315 
2316   // If either type is a pointer, the other type has to be either an
2317   // integer or a pointer.
2318   if (!DestType->isArithmeticType()) {
2319     if (!SrcType->isIntegralType(Self.Context) && SrcType->isArithmeticType()) {
2320       Self.Diag(SrcExpr.get()->getExprLoc(),
2321                 diag::err_cast_pointer_from_non_pointer_int)
2322         << SrcType << SrcExpr.get()->getSourceRange();
2323       SrcExpr = ExprError();
2324       return;
2325     }
2326     checkIntToPointerCast(/* CStyle */ true, OpRange.getBegin(), SrcExpr.get(),
2327                           DestType, Self);
2328   } else if (!SrcType->isArithmeticType()) {
2329     if (!DestType->isIntegralType(Self.Context) &&
2330         DestType->isArithmeticType()) {
2331       Self.Diag(SrcExpr.get()->getLocStart(),
2332            diag::err_cast_pointer_to_non_pointer_int)
2333         << DestType << SrcExpr.get()->getSourceRange();
2334       SrcExpr = ExprError();
2335       return;
2336     }
2337   }
2338 
2339   if (Self.getLangOpts().OpenCL && !Self.getOpenCLOptions().cl_khr_fp16) {
2340     if (DestType->isHalfType()) {
2341       Self.Diag(SrcExpr.get()->getLocStart(), diag::err_opencl_cast_to_half)
2342         << DestType << SrcExpr.get()->getSourceRange();
2343       SrcExpr = ExprError();
2344       return;
2345     }
2346   }
2347 
2348   // ARC imposes extra restrictions on casts.
2349   if (Self.getLangOpts().ObjCAutoRefCount) {
2350     checkObjCARCConversion(Sema::CCK_CStyleCast);
2351     if (SrcExpr.isInvalid())
2352       return;
2353 
2354     if (const PointerType *CastPtr = DestType->getAs<PointerType>()) {
2355       if (const PointerType *ExprPtr = SrcType->getAs<PointerType>()) {
2356         Qualifiers CastQuals = CastPtr->getPointeeType().getQualifiers();
2357         Qualifiers ExprQuals = ExprPtr->getPointeeType().getQualifiers();
2358         if (CastPtr->getPointeeType()->isObjCLifetimeType() &&
2359             ExprPtr->getPointeeType()->isObjCLifetimeType() &&
2360             !CastQuals.compatiblyIncludesObjCLifetime(ExprQuals)) {
2361           Self.Diag(SrcExpr.get()->getLocStart(),
2362                     diag::err_typecheck_incompatible_ownership)
2363             << SrcType << DestType << Sema::AA_Casting
2364             << SrcExpr.get()->getSourceRange();
2365           return;
2366         }
2367       }
2368     }
2369     else if (!Self.CheckObjCARCUnavailableWeakConversion(DestType, SrcType)) {
2370       Self.Diag(SrcExpr.get()->getLocStart(),
2371                 diag::err_arc_convesion_of_weak_unavailable)
2372         << 1 << SrcType << DestType << SrcExpr.get()->getSourceRange();
2373       SrcExpr = ExprError();
2374       return;
2375     }
2376   }
2377 
2378   DiagnoseCastOfObjCSEL(Self, SrcExpr, DestType);
2379   DiagnoseBadFunctionCast(Self, SrcExpr, DestType);
2380   Kind = Self.PrepareScalarCast(SrcExpr, DestType);
2381   if (SrcExpr.isInvalid())
2382     return;
2383 
2384   if (Kind == CK_BitCast)
2385     checkCastAlign();
2386 
2387   // -Wcast-qual
2388   QualType TheOffendingSrcType, TheOffendingDestType;
2389   Qualifiers CastAwayQualifiers;
2390   if (SrcType->isAnyPointerType() && DestType->isAnyPointerType() &&
2391       CastsAwayConstness(Self, SrcType, DestType, true, false,
2392                          &TheOffendingSrcType, &TheOffendingDestType,
2393                          &CastAwayQualifiers)) {
2394     int qualifiers = -1;
2395     if (CastAwayQualifiers.hasConst() && CastAwayQualifiers.hasVolatile()) {
2396       qualifiers = 0;
2397     } else if (CastAwayQualifiers.hasConst()) {
2398       qualifiers = 1;
2399     } else if (CastAwayQualifiers.hasVolatile()) {
2400       qualifiers = 2;
2401     }
2402     // This is a variant of int **x; const int **y = (const int **)x;
2403     if (qualifiers == -1)
2404       Self.Diag(SrcExpr.get()->getLocStart(), diag::warn_cast_qual2) <<
2405         SrcType << DestType;
2406     else
2407       Self.Diag(SrcExpr.get()->getLocStart(), diag::warn_cast_qual) <<
2408         TheOffendingSrcType << TheOffendingDestType << qualifiers;
2409   }
2410 }
2411 
2412 ExprResult Sema::BuildCStyleCastExpr(SourceLocation LPLoc,
2413                                      TypeSourceInfo *CastTypeInfo,
2414                                      SourceLocation RPLoc,
2415                                      Expr *CastExpr) {
2416   CastOperation Op(*this, CastTypeInfo->getType(), CastExpr);
2417   Op.DestRange = CastTypeInfo->getTypeLoc().getSourceRange();
2418   Op.OpRange = SourceRange(LPLoc, CastExpr->getLocEnd());
2419 
2420   if (getLangOpts().CPlusPlus) {
2421     Op.CheckCXXCStyleCast(/*FunctionalStyle=*/ false,
2422                           isa<InitListExpr>(CastExpr));
2423   } else {
2424     Op.CheckCStyleCast();
2425   }
2426 
2427   if (Op.SrcExpr.isInvalid())
2428     return ExprError();
2429 
2430   return Op.complete(CStyleCastExpr::Create(Context, Op.ResultType,
2431                               Op.ValueKind, Op.Kind, Op.SrcExpr.get(),
2432                               &Op.BasePath, CastTypeInfo, LPLoc, RPLoc));
2433 }
2434 
2435 ExprResult Sema::BuildCXXFunctionalCastExpr(TypeSourceInfo *CastTypeInfo,
2436                                             SourceLocation LPLoc,
2437                                             Expr *CastExpr,
2438                                             SourceLocation RPLoc) {
2439   assert(LPLoc.isValid() && "List-initialization shouldn't get here.");
2440   CastOperation Op(*this, CastTypeInfo->getType(), CastExpr);
2441   Op.DestRange = CastTypeInfo->getTypeLoc().getSourceRange();
2442   Op.OpRange = SourceRange(Op.DestRange.getBegin(), CastExpr->getLocEnd());
2443 
2444   Op.CheckCXXCStyleCast(/*FunctionalStyle=*/true, /*ListInit=*/false);
2445   if (Op.SrcExpr.isInvalid())
2446     return ExprError();
2447 
2448   if (CXXConstructExpr *ConstructExpr = dyn_cast<CXXConstructExpr>(Op.SrcExpr.get()))
2449     ConstructExpr->setParenOrBraceRange(SourceRange(LPLoc, RPLoc));
2450 
2451   return Op.complete(CXXFunctionalCastExpr::Create(Context, Op.ResultType,
2452                          Op.ValueKind, CastTypeInfo, Op.Kind,
2453                          Op.SrcExpr.get(), &Op.BasePath, LPLoc, RPLoc));
2454 }
2455