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Diffstat (limited to 'lib/Sema/SemaNamedCast.cpp')
| -rw-r--r-- | lib/Sema/SemaNamedCast.cpp | 932 |
1 files changed, 932 insertions, 0 deletions
diff --git a/lib/Sema/SemaNamedCast.cpp b/lib/Sema/SemaNamedCast.cpp new file mode 100644 index 0000000..daf6800 --- /dev/null +++ b/lib/Sema/SemaNamedCast.cpp @@ -0,0 +1,932 @@ +//===--- SemaNamedCast.cpp - Semantic Analysis for Named Casts ------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implements semantic analysis for C++ named casts. +// +//===----------------------------------------------------------------------===// + +#include "Sema.h" +#include "SemaInherit.h" +#include "clang/AST/ExprCXX.h" +#include "clang/AST/ASTContext.h" +#include "llvm/ADT/SmallVector.h" +#include <set> +using namespace clang; + +enum TryStaticCastResult { + TSC_NotApplicable, ///< The cast method is not applicable. + TSC_Success, ///< The cast method is appropriate and successful. + TSC_Failed ///< The cast method is appropriate, but failed. A + ///< diagnostic has been emitted. +}; + +static void CheckConstCast(Sema &Self, Expr *&SrcExpr, QualType DestType, + const SourceRange &OpRange, + const SourceRange &DestRange); +static void CheckReinterpretCast(Sema &Self, Expr *&SrcExpr, QualType DestType, + const SourceRange &OpRange, + const SourceRange &DestRange); +static void CheckStaticCast(Sema &Self, Expr *&SrcExpr, QualType DestType, + const SourceRange &OpRange); +static void CheckDynamicCast(Sema &Self, Expr *&SrcExpr, QualType DestType, + const SourceRange &OpRange, + const SourceRange &DestRange); + +static bool CastsAwayConstness(Sema &Self, QualType SrcType, QualType DestType); +static TryStaticCastResult TryLValueToRValueCast( + Sema &Self, Expr *SrcExpr, QualType DestType, const SourceRange &OpRange); +static TryStaticCastResult TryStaticReferenceDowncast( + Sema &Self, Expr *SrcExpr, QualType DestType, const SourceRange &OpRange); +static TryStaticCastResult TryStaticPointerDowncast( + Sema &Self, QualType SrcType, QualType DestType, const SourceRange &OpRange); +static TryStaticCastResult TryStaticMemberPointerUpcast( + Sema &Self, QualType SrcType, QualType DestType, const SourceRange &OpRange); +static TryStaticCastResult TryStaticDowncast(Sema &Self, QualType SrcType, + QualType DestType, + const SourceRange &OpRange, + QualType OrigSrcType, + QualType OrigDestType); +static TryStaticCastResult TryStaticImplicitCast(Sema &Self, Expr *SrcExpr, + QualType DestType, + const SourceRange &OpRange); + +/// ActOnCXXNamedCast - Parse {dynamic,static,reinterpret,const}_cast's. +Action::OwningExprResult +Sema::ActOnCXXNamedCast(SourceLocation OpLoc, tok::TokenKind Kind, + SourceLocation LAngleBracketLoc, TypeTy *Ty, + SourceLocation RAngleBracketLoc, + SourceLocation LParenLoc, ExprArg E, + SourceLocation RParenLoc) { + Expr *Ex = E.takeAs<Expr>(); + QualType DestType = QualType::getFromOpaquePtr(Ty); + SourceRange OpRange(OpLoc, RParenLoc); + SourceRange DestRange(LAngleBracketLoc, RAngleBracketLoc); + + // If the type is dependent, we won't do the semantic analysis now. + // FIXME: should we check this in a more fine-grained manner? + bool TypeDependent = DestType->isDependentType() || Ex->isTypeDependent(); + + switch (Kind) { + default: assert(0 && "Unknown C++ cast!"); + + case tok::kw_const_cast: + if (!TypeDependent) + CheckConstCast(*this, Ex, DestType, OpRange, DestRange); + return Owned(new (Context) CXXConstCastExpr(DestType.getNonReferenceType(), + Ex, DestType, OpLoc)); + + case tok::kw_dynamic_cast: + if (!TypeDependent) + CheckDynamicCast(*this, Ex, DestType, OpRange, DestRange); + return Owned(new (Context)CXXDynamicCastExpr(DestType.getNonReferenceType(), + Ex, DestType, OpLoc)); + + case tok::kw_reinterpret_cast: + if (!TypeDependent) + CheckReinterpretCast(*this, Ex, DestType, OpRange, DestRange); + return Owned(new (Context) CXXReinterpretCastExpr( + DestType.getNonReferenceType(), + Ex, DestType, OpLoc)); + + case tok::kw_static_cast: + if (!TypeDependent) + CheckStaticCast(*this, Ex, DestType, OpRange); + return Owned(new (Context) CXXStaticCastExpr(DestType.getNonReferenceType(), + Ex, DestType, OpLoc)); + } + + return ExprError(); +} + +/// CheckConstCast - Check that a const_cast\<DestType\>(SrcExpr) is valid. +/// Refer to C++ 5.2.11 for details. const_cast is typically used in code +/// like this: +/// const char *str = "literal"; +/// legacy_function(const_cast\<char*\>(str)); +void +CheckConstCast(Sema &Self, Expr *&SrcExpr, QualType DestType, + const SourceRange &OpRange, const SourceRange &DestRange) +{ + QualType OrigDestType = DestType, OrigSrcType = SrcExpr->getType(); + + DestType = Self.Context.getCanonicalType(DestType); + QualType SrcType = SrcExpr->getType(); + if (const LValueReferenceType *DestTypeTmp = + DestType->getAsLValueReferenceType()) { + if (SrcExpr->isLvalue(Self.Context) != Expr::LV_Valid) { + // Cannot cast non-lvalue to lvalue reference type. + Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_rvalue) + << "const_cast" << OrigDestType << SrcExpr->getSourceRange(); + return; + } + + // C++ 5.2.11p4: An lvalue of type T1 can be [cast] to an lvalue of type T2 + // [...] if a pointer to T1 can be [cast] to the type pointer to T2. + DestType = Self.Context.getPointerType(DestTypeTmp->getPointeeType()); + SrcType = Self.Context.getPointerType(SrcType); + } else { + // C++ 5.2.11p1: Otherwise, the result is an rvalue and the + // lvalue-to-rvalue, array-to-pointer, and function-to-pointer standard + // conversions are performed on the expression. + Self.DefaultFunctionArrayConversion(SrcExpr); + SrcType = SrcExpr->getType(); + } + + // C++ 5.2.11p5: For a const_cast involving pointers to data members [...] + // the rules for const_cast are the same as those used for pointers. + + if (!DestType->isPointerType() && !DestType->isMemberPointerType()) { + // Cannot cast to non-pointer, non-reference type. Note that, if DestType + // was a reference type, we converted it to a pointer above. + // The status of rvalue references isn't entirely clear, but it looks like + // conversion to them is simply invalid. + // C++ 5.2.11p3: For two pointer types [...] + Self.Diag(OpRange.getBegin(), diag::err_bad_const_cast_dest) + << OrigDestType << DestRange; + return; + } + if (DestType->isFunctionPointerType() || + DestType->isMemberFunctionPointerType()) { + // Cannot cast direct function pointers. + // C++ 5.2.11p2: [...] where T is any object type or the void type [...] + // T is the ultimate pointee of source and target type. + Self.Diag(OpRange.getBegin(), diag::err_bad_const_cast_dest) + << OrigDestType << DestRange; + return; + } + SrcType = Self.Context.getCanonicalType(SrcType); + + // Unwrap the pointers. Ignore qualifiers. Terminate early if the types are + // completely equal. + // FIXME: const_cast should probably not be able to convert between pointers + // to different address spaces. + // C++ 5.2.11p3 describes the core semantics of const_cast. All cv specifiers + // in multi-level pointers may change, but the level count must be the same, + // as must be the final pointee type. + while (SrcType != DestType && + Self.UnwrapSimilarPointerTypes(SrcType, DestType)) { + SrcType = SrcType.getUnqualifiedType(); + DestType = DestType.getUnqualifiedType(); + } + + // Doug Gregor said to disallow this until users complain. +#if 0 + // If we end up with constant arrays of equal size, unwrap those too. A cast + // from const int [N] to int (&)[N] is invalid by my reading of the + // standard, but g++ accepts it even with -ansi -pedantic. + // No more than one level, though, so don't embed this in the unwrap loop + // above. + const ConstantArrayType *SrcTypeArr, *DestTypeArr; + if ((SrcTypeArr = Self.Context.getAsConstantArrayType(SrcType)) && + (DestTypeArr = Self.Context.getAsConstantArrayType(DestType))) + { + if (SrcTypeArr->getSize() != DestTypeArr->getSize()) { + // Different array sizes. + Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_generic) + << "const_cast" << OrigDestType << OrigSrcType << OpRange; + return; + } + SrcType = SrcTypeArr->getElementType().getUnqualifiedType(); + DestType = DestTypeArr->getElementType().getUnqualifiedType(); + } +#endif + + // Since we're dealing in canonical types, the remainder must be the same. + if (SrcType != DestType) { + // Cast between unrelated types. + Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_generic) + << "const_cast" << OrigDestType << OrigSrcType << OpRange; + return; + } +} + +/// CheckReinterpretCast - Check that a reinterpret_cast\<DestType\>(SrcExpr) is +/// valid. +/// Refer to C++ 5.2.10 for details. reinterpret_cast is typically used in code +/// like this: +/// char *bytes = reinterpret_cast\<char*\>(int_ptr); +void +CheckReinterpretCast(Sema &Self, Expr *&SrcExpr, QualType DestType, + const SourceRange &OpRange, const SourceRange &DestRange) +{ + QualType OrigDestType = DestType, OrigSrcType = SrcExpr->getType(); + + DestType = Self.Context.getCanonicalType(DestType); + QualType SrcType = SrcExpr->getType(); + if (const LValueReferenceType *DestTypeTmp = + DestType->getAsLValueReferenceType()) { + if (SrcExpr->isLvalue(Self.Context) != Expr::LV_Valid) { + // Cannot cast non-lvalue to reference type. + Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_rvalue) + << "reinterpret_cast" << OrigDestType << SrcExpr->getSourceRange(); + return; + } + + // C++ 5.2.10p10: [...] a reference cast reinterpret_cast<T&>(x) has the + // same effect as the conversion *reinterpret_cast<T*>(&x) with the + // built-in & and * operators. + // This code does this transformation for the checked types. + DestType = Self.Context.getPointerType(DestTypeTmp->getPointeeType()); + SrcType = Self.Context.getPointerType(SrcType); + } else if (const RValueReferenceType *DestTypeTmp = + DestType->getAsRValueReferenceType()) { + // Both the reference conversion and the rvalue rules apply. + Self.DefaultFunctionArrayConversion(SrcExpr); + SrcType = SrcExpr->getType(); + + DestType = Self.Context.getPointerType(DestTypeTmp->getPointeeType()); + SrcType = Self.Context.getPointerType(SrcType); + } else { + // C++ 5.2.10p1: [...] the lvalue-to-rvalue, array-to-pointer, and + // function-to-pointer standard conversions are performed on the + // expression v. + Self.DefaultFunctionArrayConversion(SrcExpr); + SrcType = SrcExpr->getType(); + } + + // Canonicalize source for comparison. + SrcType = Self.Context.getCanonicalType(SrcType); + + const MemberPointerType *DestMemPtr = DestType->getAsMemberPointerType(), + *SrcMemPtr = SrcType->getAsMemberPointerType(); + if (DestMemPtr && SrcMemPtr) { + // C++ 5.2.10p9: An rvalue of type "pointer to member of X of type T1" + // can be explicitly converted to an rvalue of type "pointer to member + // of Y of type T2" if T1 and T2 are both function types or both object + // types. + if (DestMemPtr->getPointeeType()->isFunctionType() != + SrcMemPtr->getPointeeType()->isFunctionType()) { + Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_generic) + << "reinterpret_cast" << OrigDestType << OrigSrcType << OpRange; + return; + } + + // C++ 5.2.10p2: The reinterpret_cast operator shall not cast away + // constness. + if (CastsAwayConstness(Self, SrcType, DestType)) { + Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_const_away) + << "reinterpret_cast" << OrigDestType << OrigSrcType << OpRange; + return; + } + + // A valid member pointer cast. + return; + } + + // See below for the enumeral issue. + if (SrcType->isNullPtrType() && DestType->isIntegralType() && + !DestType->isEnumeralType()) { + // C++0x 5.2.10p4: A pointer can be explicitly converted to any integral + // type large enough to hold it. A value of std::nullptr_t can be + // converted to an integral type; the conversion has the same meaning + // and validity as a conversion of (void*)0 to the integral type. + if (Self.Context.getTypeSize(SrcType) > + Self.Context.getTypeSize(DestType)) { + Self.Diag(OpRange.getBegin(), diag::err_bad_reinterpret_cast_small_int) + << OrigDestType << DestRange; + } + return; + } + + bool destIsPtr = DestType->isPointerType(); + bool srcIsPtr = SrcType->isPointerType(); + if (!destIsPtr && !srcIsPtr) { + // Except for std::nullptr_t->integer and lvalue->reference, which are + // handled above, at least one of the two arguments must be a pointer. + Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_generic) + << "reinterpret_cast" << OrigDestType << OrigSrcType << OpRange; + return; + } + + if (SrcType == DestType) { + // C++ 5.2.10p2 has a note that mentions that, subject to all other + // restrictions, a cast to the same type is allowed. The intent is not + // entirely clear here, since all other paragraphs explicitly forbid casts + // to the same type. However, the behavior of compilers is pretty consistent + // on this point: allow same-type conversion if the involved types are + // pointers, disallow otherwise. + return; + } + + // Note: Clang treats enumeration types as integral types. If this is ever + // changed for C++, the additional check here will be redundant. + if (DestType->isIntegralType() && !DestType->isEnumeralType()) { + assert(srcIsPtr && "One type must be a pointer"); + // C++ 5.2.10p4: A pointer can be explicitly converted to any integral + // type large enough to hold it. + if (Self.Context.getTypeSize(SrcType) > + Self.Context.getTypeSize(DestType)) { + Self.Diag(OpRange.getBegin(), diag::err_bad_reinterpret_cast_small_int) + << OrigDestType << DestRange; + } + return; + } + + if (SrcType->isIntegralType() || SrcType->isEnumeralType()) { + assert(destIsPtr && "One type must be a pointer"); + // C++ 5.2.10p5: A value of integral or enumeration type can be explicitly + // converted to a pointer. + return; + } + + if (!destIsPtr || !srcIsPtr) { + // With the valid non-pointer conversions out of the way, we can be even + // more stringent. + Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_generic) + << "reinterpret_cast" << OrigDestType << OrigSrcType << OpRange; + return; + } + + // C++ 5.2.10p2: The reinterpret_cast operator shall not cast away constness. + if (CastsAwayConstness(Self, SrcType, DestType)) { + Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_const_away) + << "reinterpret_cast" << OrigDestType << OrigSrcType << OpRange; + return; + } + + // Not casting away constness, so the only remaining check is for compatible + // pointer categories. + + if (SrcType->isFunctionPointerType()) { + if (DestType->isFunctionPointerType()) { + // C++ 5.2.10p6: A pointer to a function can be explicitly converted to + // a pointer to a function of a different type. + return; + } + + // C++0x 5.2.10p8: Converting a pointer to a function into a pointer to + // an object type or vice versa is conditionally-supported. + // Compilers support it in C++03 too, though, because it's necessary for + // casting the return value of dlsym() and GetProcAddress(). + // FIXME: Conditionally-supported behavior should be configurable in the + // TargetInfo or similar. + if (!Self.getLangOptions().CPlusPlus0x) { + Self.Diag(OpRange.getBegin(), diag::ext_reinterpret_cast_fn_obj) + << OpRange; + } + return; + } + + if (DestType->isFunctionPointerType()) { + // See above. + if (!Self.getLangOptions().CPlusPlus0x) { + Self.Diag(OpRange.getBegin(), diag::ext_reinterpret_cast_fn_obj) + << OpRange; + } + return; + } + + // C++ 5.2.10p7: A pointer to an object can be explicitly converted to + // a pointer to an object of different type. + // Void pointers are not specified, but supported by every compiler out there. + // So we finish by allowing everything that remains - it's got to be two + // object pointers. +} + +/// CastsAwayConstness - Check if the pointer conversion from SrcType to +/// DestType casts away constness as defined in C++ 5.2.11p8ff. This is used by +/// the cast checkers. Both arguments must denote pointer (possibly to member) +/// types. +bool +CastsAwayConstness(Sema &Self, QualType SrcType, QualType DestType) +{ + // Casting away constness is defined in C++ 5.2.11p8 with reference to + // C++ 4.4. We piggyback on Sema::IsQualificationConversion for this, since + // the rules are non-trivial. So first we construct Tcv *...cv* as described + // in C++ 5.2.11p8. + assert((SrcType->isPointerType() || SrcType->isMemberPointerType()) && + "Source type is not pointer or pointer to member."); + assert((DestType->isPointerType() || DestType->isMemberPointerType()) && + "Destination type is not pointer or pointer to member."); + + QualType UnwrappedSrcType = SrcType, UnwrappedDestType = DestType; + llvm::SmallVector<unsigned, 8> cv1, cv2; + + // Find the qualifications. + while (Self.UnwrapSimilarPointerTypes(UnwrappedSrcType, UnwrappedDestType)) { + cv1.push_back(UnwrappedSrcType.getCVRQualifiers()); + cv2.push_back(UnwrappedDestType.getCVRQualifiers()); + } + assert(cv1.size() > 0 && "Must have at least one pointer level."); + + // Construct void pointers with those qualifiers (in reverse order of + // unwrapping, of course). + QualType SrcConstruct = Self.Context.VoidTy; + QualType DestConstruct = Self.Context.VoidTy; + for (llvm::SmallVector<unsigned, 8>::reverse_iterator i1 = cv1.rbegin(), + i2 = cv2.rbegin(); + i1 != cv1.rend(); ++i1, ++i2) + { + SrcConstruct = Self.Context.getPointerType( + SrcConstruct.getQualifiedType(*i1)); + DestConstruct = Self.Context.getPointerType( + DestConstruct.getQualifiedType(*i2)); + } + + // Test if they're compatible. + return SrcConstruct != DestConstruct && + !Self.IsQualificationConversion(SrcConstruct, DestConstruct); +} + +/// CheckStaticCast - Check that a static_cast\<DestType\>(SrcExpr) is valid. +/// Refer to C++ 5.2.9 for details. Static casts are mostly used for making +/// implicit conversions explicit and getting rid of data loss warnings. +void +CheckStaticCast(Sema &Self, Expr *&SrcExpr, QualType DestType, + const SourceRange &OpRange) +{ + // The order the tests is not entirely arbitrary. There is one conversion + // that can be handled in two different ways. Given: + // struct A {}; + // struct B : public A { + // B(); B(const A&); + // }; + // const A &a = B(); + // the cast static_cast<const B&>(a) could be seen as either a static + // reference downcast, or an explicit invocation of the user-defined + // conversion using B's conversion constructor. + // DR 427 specifies that the downcast is to be applied here. + + // FIXME: With N2812, casts to rvalue refs will change. + + // C++ 5.2.9p4: Any expression can be explicitly converted to type "cv void". + if (DestType->isVoidType()) { + return; + } + + // C++ 5.2.9p5, reference downcast. + // See the function for details. + // DR 427 specifies that this is to be applied before paragraph 2. + if (TryStaticReferenceDowncast(Self, SrcExpr, DestType, OpRange) + > TSC_NotApplicable) { + return; + } + + // N2844 5.2.9p3: An lvalue of type "cv1 T1" can be cast to type "rvalue + // reference to cv2 T2" if "cv2 T2" is reference-compatible with "cv1 T1". + if (TryLValueToRValueCast(Self, SrcExpr, DestType, OpRange) > + TSC_NotApplicable) { + return; + } + + // C++ 5.2.9p2: An expression e can be explicitly converted to a type T + // [...] if the declaration "T t(e);" is well-formed, [...]. + if (TryStaticImplicitCast(Self, SrcExpr, DestType, OpRange) > + TSC_NotApplicable) { + return; + } + + // C++ 5.2.9p6: May apply the reverse of any standard conversion, except + // lvalue-to-rvalue, array-to-pointer, function-to-pointer, and boolean + // conversions, subject to further restrictions. + // Also, C++ 5.2.9p1 forbids casting away constness, which makes reversal + // of qualification conversions impossible. + + // The lvalue-to-rvalue, array-to-pointer and function-to-pointer conversions + // are applied to the expression. + QualType OrigSrcType = SrcExpr->getType(); + Self.DefaultFunctionArrayConversion(SrcExpr); + + QualType SrcType = Self.Context.getCanonicalType(SrcExpr->getType()); + + // Reverse integral promotion/conversion. All such conversions are themselves + // again integral promotions or conversions and are thus already handled by + // p2 (TryDirectInitialization above). + // (Note: any data loss warnings should be suppressed.) + // The exception is the reverse of enum->integer, i.e. integer->enum (and + // enum->enum). See also C++ 5.2.9p7. + // The same goes for reverse floating point promotion/conversion and + // floating-integral conversions. Again, only floating->enum is relevant. + if (DestType->isEnumeralType()) { + if (SrcType->isComplexType() || SrcType->isVectorType()) { + // Fall through - these cannot be converted. + } else if (SrcType->isArithmeticType() || SrcType->isEnumeralType()) { + return; + } + } + + // Reverse pointer upcast. C++ 4.10p3 specifies pointer upcast. + // C++ 5.2.9p8 additionally disallows a cast path through virtual inheritance. + if (TryStaticPointerDowncast(Self, SrcType, DestType, OpRange) + > TSC_NotApplicable) { + return; + } + + // Reverse member pointer conversion. C++ 4.11 specifies member pointer + // conversion. C++ 5.2.9p9 has additional information. + // DR54's access restrictions apply here also. + if (TryStaticMemberPointerUpcast(Self, SrcType, DestType, OpRange) + > TSC_NotApplicable) { + return; + } + + // Reverse pointer conversion to void*. C++ 4.10.p2 specifies conversion to + // void*. C++ 5.2.9p10 specifies additional restrictions, which really is + // just the usual constness stuff. + if (const PointerType *SrcPointer = SrcType->getAsPointerType()) { + QualType SrcPointee = SrcPointer->getPointeeType(); + if (SrcPointee->isVoidType()) { + if (const PointerType *DestPointer = DestType->getAsPointerType()) { + QualType DestPointee = DestPointer->getPointeeType(); + if (DestPointee->isIncompleteOrObjectType()) { + // This is definitely the intended conversion, but it might fail due + // to a const violation. + if (!DestPointee.isAtLeastAsQualifiedAs(SrcPointee)) { + Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_const_away) + << "static_cast" << DestType << OrigSrcType << OpRange; + } + return; + } + } + } + } + + // We tried everything. Everything! Nothing works! :-( + // FIXME: Error reporting could be a lot better. Should store the reason why + // every substep failed and, at the end, select the most specific and report + // that. + Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_generic) + << "static_cast" << DestType << OrigSrcType + << OpRange; +} + +/// Tests whether a conversion according to N2844 is valid. +TryStaticCastResult +TryLValueToRValueCast(Sema &Self, Expr *SrcExpr, QualType DestType, + const SourceRange &OpRange) +{ + // N2844 5.2.9p3: An lvalue of type "cv1 T1" can be cast to type "rvalue + // reference to cv2 T2" if "cv2 T2" is reference-compatible with "cv1 T1". + const RValueReferenceType *R = DestType->getAsRValueReferenceType(); + if (!R) + return TSC_NotApplicable; + + if (SrcExpr->isLvalue(Self.Context) != Expr::LV_Valid) + return TSC_NotApplicable; + + // Because we try the reference downcast before this function, from now on + // this is the only cast possibility, so we issue an error if we fail now. + bool DerivedToBase; + if (Self.CompareReferenceRelationship(SrcExpr->getType(), R->getPointeeType(), + DerivedToBase) < + Sema::Ref_Compatible_With_Added_Qualification) { + Self.Diag(OpRange.getBegin(), diag::err_bad_lvalue_to_rvalue_cast) + << SrcExpr->getType() << R->getPointeeType() << OpRange; + return TSC_Failed; + } + + // FIXME: Similar to CheckReferenceInit, we actually need more AST annotation + // than nothing. + return TSC_Success; +} + +/// Tests whether a conversion according to C++ 5.2.9p5 is valid. +TryStaticCastResult +TryStaticReferenceDowncast(Sema &Self, Expr *SrcExpr, QualType DestType, + const SourceRange &OpRange) +{ + // C++ 5.2.9p5: An lvalue of type "cv1 B", where B is a class type, can be + // cast to type "reference to cv2 D", where D is a class derived from B, + // if a valid standard conversion from "pointer to D" to "pointer to B" + // exists, cv2 >= cv1, and B is not a virtual base class of D. + // In addition, DR54 clarifies that the base must be accessible in the + // current context. Although the wording of DR54 only applies to the pointer + // variant of this rule, the intent is clearly for it to apply to the this + // conversion as well. + + if (SrcExpr->isLvalue(Self.Context) != Expr::LV_Valid) { + return TSC_NotApplicable; + } + + const ReferenceType *DestReference = DestType->getAsReferenceType(); + if (!DestReference) { + return TSC_NotApplicable; + } + QualType DestPointee = DestReference->getPointeeType(); + + return TryStaticDowncast(Self, SrcExpr->getType(), DestPointee, OpRange, + SrcExpr->getType(), DestType); +} + +/// Tests whether a conversion according to C++ 5.2.9p8 is valid. +TryStaticCastResult +TryStaticPointerDowncast(Sema &Self, QualType SrcType, QualType DestType, + const SourceRange &OpRange) +{ + // C++ 5.2.9p8: An rvalue of type "pointer to cv1 B", where B is a class + // type, can be converted to an rvalue of type "pointer to cv2 D", where D + // is a class derived from B, if a valid standard conversion from "pointer + // to D" to "pointer to B" exists, cv2 >= cv1, and B is not a virtual base + // class of D. + // In addition, DR54 clarifies that the base must be accessible in the + // current context. + + const PointerType *SrcPointer = SrcType->getAsPointerType(); + if (!SrcPointer) { + return TSC_NotApplicable; + } + + const PointerType *DestPointer = DestType->getAsPointerType(); + if (!DestPointer) { + return TSC_NotApplicable; + } + + return TryStaticDowncast(Self, SrcPointer->getPointeeType(), + DestPointer->getPointeeType(), + OpRange, SrcType, DestType); +} + +/// TryStaticDowncast - Common functionality of TryStaticReferenceDowncast and +/// TryStaticPointerDowncast. Tests whether a static downcast from SrcType to +/// DestType, both of which must be canonical, is possible and allowed. +TryStaticCastResult +TryStaticDowncast(Sema &Self, QualType SrcType, QualType DestType, + const SourceRange &OpRange, QualType OrigSrcType, + QualType OrigDestType) +{ + // Downcast can only happen in class hierarchies, so we need classes. + if (!DestType->isRecordType() || !SrcType->isRecordType()) { + return TSC_NotApplicable; + } + + BasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/false, + /*DetectVirtual=*/true); + if (!Self.IsDerivedFrom(DestType, SrcType, Paths)) { + return TSC_NotApplicable; + } + + // Target type does derive from source type. Now we're serious. If an error + // appears now, it's not ignored. + // This may not be entirely in line with the standard. Take for example: + // struct A {}; + // struct B : virtual A { + // B(A&); + // }; + // + // void f() + // { + // (void)static_cast<const B&>(*((A*)0)); + // } + // As far as the standard is concerned, p5 does not apply (A is virtual), so + // p2 should be used instead - "const B& t(*((A*)0));" is perfectly valid. + // However, both GCC and Comeau reject this example, and accepting it would + // mean more complex code if we're to preserve the nice error message. + // FIXME: Being 100% compliant here would be nice to have. + + // Must preserve cv, as always. + if (!DestType.isAtLeastAsQualifiedAs(SrcType)) { + Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_const_away) + << "static_cast" << OrigDestType << OrigSrcType << OpRange; + return TSC_Failed; + } + + if (Paths.isAmbiguous(SrcType.getUnqualifiedType())) { + // This code is analoguous to that in CheckDerivedToBaseConversion, except + // that it builds the paths in reverse order. + // To sum up: record all paths to the base and build a nice string from + // them. Use it to spice up the error message. + Paths.clear(); + Paths.setRecordingPaths(true); + Self.IsDerivedFrom(DestType, SrcType, Paths); + std::string PathDisplayStr; + std::set<unsigned> DisplayedPaths; + for (BasePaths::paths_iterator Path = Paths.begin(); + Path != Paths.end(); ++Path) { + if (DisplayedPaths.insert(Path->back().SubobjectNumber).second) { + // We haven't displayed a path to this particular base + // class subobject yet. + PathDisplayStr += "\n "; + for (BasePath::const_reverse_iterator Element = Path->rbegin(); + Element != Path->rend(); ++Element) + PathDisplayStr += Element->Base->getType().getAsString() + " -> "; + PathDisplayStr += DestType.getAsString(); + } + } + + Self.Diag(OpRange.getBegin(), diag::err_ambiguous_base_to_derived_cast) + << SrcType.getUnqualifiedType() << DestType.getUnqualifiedType() + << PathDisplayStr << OpRange; + return TSC_Failed; + } + + if (Paths.getDetectedVirtual() != 0) { + QualType VirtualBase(Paths.getDetectedVirtual(), 0); + Self.Diag(OpRange.getBegin(), diag::err_static_downcast_via_virtual) + << OrigSrcType << OrigDestType << VirtualBase << OpRange; + return TSC_Failed; + } + + // FIXME: Test accessibility. + + return TSC_Success; +} + +/// TryStaticMemberPointerUpcast - Tests whether a conversion according to +/// C++ 5.2.9p9 is valid: +/// +/// An rvalue of type "pointer to member of D of type cv1 T" can be +/// converted to an rvalue of type "pointer to member of B of type cv2 T", +/// where B is a base class of D [...]. +/// +TryStaticCastResult +TryStaticMemberPointerUpcast(Sema &Self, QualType SrcType, QualType DestType, + const SourceRange &OpRange) +{ + const MemberPointerType *SrcMemPtr = SrcType->getAsMemberPointerType(); + if (!SrcMemPtr) + return TSC_NotApplicable; + const MemberPointerType *DestMemPtr = DestType->getAsMemberPointerType(); + if (!DestMemPtr) + return TSC_NotApplicable; + + // T == T, modulo cv + if (Self.Context.getCanonicalType( + SrcMemPtr->getPointeeType().getUnqualifiedType()) != + Self.Context.getCanonicalType(DestMemPtr->getPointeeType(). + getUnqualifiedType())) + return TSC_NotApplicable; + + // B base of D + QualType SrcClass(SrcMemPtr->getClass(), 0); + QualType DestClass(DestMemPtr->getClass(), 0); + BasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/false, + /*DetectVirtual=*/true); + if (!Self.IsDerivedFrom(SrcClass, DestClass, Paths)) { + return TSC_NotApplicable; + } + + // B is a base of D. But is it an allowed base? If not, it's a hard error. + if (Paths.isAmbiguous(DestClass)) { + Paths.clear(); + Paths.setRecordingPaths(true); + bool StillOkay = Self.IsDerivedFrom(SrcClass, DestClass, Paths); + assert(StillOkay); + StillOkay = StillOkay; + std::string PathDisplayStr = Self.getAmbiguousPathsDisplayString(Paths); + Self.Diag(OpRange.getBegin(), diag::err_ambiguous_memptr_conv) + << 1 << SrcClass << DestClass << PathDisplayStr << OpRange; + return TSC_Failed; + } + + if (const RecordType *VBase = Paths.getDetectedVirtual()) { + Self.Diag(OpRange.getBegin(), diag::err_memptr_conv_via_virtual) + << SrcClass << DestClass << QualType(VBase, 0) << OpRange; + return TSC_Failed; + } + + // FIXME: Test accessibility. + + return TSC_Success; +} + +/// TryStaticImplicitCast - Tests whether a conversion according to C++ 5.2.9p2 +/// is valid: +/// +/// An expression e can be explicitly converted to a type T using a +/// @c static_cast if the declaration "T t(e);" is well-formed [...]. +TryStaticCastResult +TryStaticImplicitCast(Sema &Self, Expr *SrcExpr, QualType DestType, + const SourceRange &OpRange) +{ + if (DestType->isReferenceType()) { + // At this point of CheckStaticCast, if the destination is a reference, + // this has to work. There is no other way that works. + return Self.CheckReferenceInit(SrcExpr, DestType) ? + TSC_Failed : TSC_Success; + } + if (DestType->isRecordType()) { + // FIXME: Use an implementation of C++ [over.match.ctor] for this. + return TSC_NotApplicable; + } + + // FIXME: To get a proper error from invalid conversions here, we need to + // reimplement more of this. + ImplicitConversionSequence ICS = Self.TryImplicitConversion( + SrcExpr, DestType); + return ICS.ConversionKind == ImplicitConversionSequence::BadConversion ? + TSC_NotApplicable : TSC_Success; +} + +/// CheckDynamicCast - Check that a dynamic_cast\<DestType\>(SrcExpr) is valid. +/// Refer to C++ 5.2.7 for details. Dynamic casts are used mostly for runtime- +/// checked downcasts in class hierarchies. +void +CheckDynamicCast(Sema &Self, Expr *&SrcExpr, QualType DestType, + const SourceRange &OpRange, + const SourceRange &DestRange) +{ + QualType OrigDestType = DestType, OrigSrcType = SrcExpr->getType(); + DestType = Self.Context.getCanonicalType(DestType); + + // C++ 5.2.7p1: T shall be a pointer or reference to a complete class type, + // or "pointer to cv void". + + QualType DestPointee; + const PointerType *DestPointer = DestType->getAsPointerType(); + const ReferenceType *DestReference = DestType->getAsReferenceType(); + if (DestPointer) { + DestPointee = DestPointer->getPointeeType(); + } else if (DestReference) { + DestPointee = DestReference->getPointeeType(); + } else { + Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_ref_or_ptr) + << OrigDestType << DestRange; + return; + } + + const RecordType *DestRecord = DestPointee->getAsRecordType(); + if (DestPointee->isVoidType()) { + assert(DestPointer && "Reference to void is not possible"); + } else if (DestRecord) { + if (Self.RequireCompleteType(OpRange.getBegin(), DestPointee, + diag::err_bad_dynamic_cast_incomplete, + DestRange)) + return; + } else { + Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_class) + << DestPointee.getUnqualifiedType() << DestRange; + return; + } + + // C++0x 5.2.7p2: If T is a pointer type, v shall be an rvalue of a pointer to + // complete class type, [...]. If T is an lvalue reference type, v shall be + // an lvalue of a complete class type, [...]. If T is an rvalue reference + // type, v shall be an expression having a complete effective class type, + // [...] + + QualType SrcType = Self.Context.getCanonicalType(OrigSrcType); + QualType SrcPointee; + if (DestPointer) { + if (const PointerType *SrcPointer = SrcType->getAsPointerType()) { + SrcPointee = SrcPointer->getPointeeType(); + } else { + Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_ptr) + << OrigSrcType << SrcExpr->getSourceRange(); + return; + } + } else if (DestReference->isLValueReferenceType()) { + if (SrcExpr->isLvalue(Self.Context) != Expr::LV_Valid) { + Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_rvalue) + << "dynamic_cast" << OrigDestType << OpRange; + } + SrcPointee = SrcType; + } else { + SrcPointee = SrcType; + } + + const RecordType *SrcRecord = SrcPointee->getAsRecordType(); + if (SrcRecord) { + if (Self.RequireCompleteType(OpRange.getBegin(), SrcPointee, + diag::err_bad_dynamic_cast_incomplete, + SrcExpr->getSourceRange())) + return; + } else { + Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_class) + << SrcPointee.getUnqualifiedType() << SrcExpr->getSourceRange(); + return; + } + + assert((DestPointer || DestReference) && + "Bad destination non-ptr/ref slipped through."); + assert((DestRecord || DestPointee->isVoidType()) && + "Bad destination pointee slipped through."); + assert(SrcRecord && "Bad source pointee slipped through."); + + // C++ 5.2.7p1: The dynamic_cast operator shall not cast away constness. + if (!DestPointee.isAtLeastAsQualifiedAs(SrcPointee)) { + Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_const_away) + << "dynamic_cast" << OrigDestType << OrigSrcType << OpRange; + return; + } + + // C++ 5.2.7p3: If the type of v is the same as the required result type, + // [except for cv]. + if (DestRecord == SrcRecord) { + return; + } + + // C++ 5.2.7p5 + // Upcasts are resolved statically. + if (DestRecord && Self.IsDerivedFrom(SrcPointee, DestPointee)) { + Self.CheckDerivedToBaseConversion(SrcPointee, DestPointee, + OpRange.getBegin(), OpRange); + // Diagnostic already emitted on error. + return; + } + + // C++ 5.2.7p6: Otherwise, v shall be [polymorphic]. + const RecordDecl *SrcDecl = SrcRecord->getDecl()->getDefinition(Self.Context); + assert(SrcDecl && "Definition missing"); + if (!cast<CXXRecordDecl>(SrcDecl)->isPolymorphic()) { + Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_polymorphic) + << SrcPointee.getUnqualifiedType() << SrcExpr->getSourceRange(); + } + + // Done. Everything else is run-time checks. +} |
