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Diffstat (limited to 'lib/Sema/SemaCXXCast.cpp')
| -rw-r--r-- | lib/Sema/SemaCXXCast.cpp | 1128 |
1 files changed, 1128 insertions, 0 deletions
diff --git a/lib/Sema/SemaCXXCast.cpp b/lib/Sema/SemaCXXCast.cpp new file mode 100644 index 0000000000000..69d1f92a08323 --- /dev/null +++ b/lib/Sema/SemaCXXCast.cpp @@ -0,0 +1,1128 @@ +//===--- 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 "clang/AST/ExprCXX.h" +#include "clang/AST/ASTContext.h" +#include "clang/AST/CXXInheritance.h" +#include "clang/Basic/PartialDiagnostic.h" +#include "llvm/ADT/SmallVector.h" +#include <set> +using namespace clang; + +enum TryCastResult { + TC_NotApplicable, ///< The cast method is not applicable. + TC_Success, ///< The cast method is appropriate and successful. + TC_Failed ///< The cast method is appropriate, but failed. A + ///< diagnostic has been emitted. +}; + +enum CastType { + CT_Const, ///< const_cast + CT_Static, ///< static_cast + CT_Reinterpret, ///< reinterpret_cast + CT_Dynamic, ///< dynamic_cast + CT_CStyle, ///< (Type)expr + CT_Functional ///< Type(expr) +}; + +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, + CastExpr::CastKind &Kind); +static void CheckStaticCast(Sema &Self, Expr *&SrcExpr, QualType DestType, + const SourceRange &OpRange, + CastExpr::CastKind &Kind, + CXXMethodDecl *&ConversionDecl); +static void CheckDynamicCast(Sema &Self, Expr *&SrcExpr, QualType DestType, + const SourceRange &OpRange, + const SourceRange &DestRange, + CastExpr::CastKind &Kind); + +static bool CastsAwayConstness(Sema &Self, QualType SrcType, QualType DestType); + +// The Try functions attempt a specific way of casting. If they succeed, they +// return TC_Success. If their way of casting is not appropriate for the given +// arguments, they return TC_NotApplicable and *may* set diag to a diagnostic +// to emit if no other way succeeds. If their way of casting is appropriate but +// fails, they return TC_Failed and *must* set diag; they can set it to 0 if +// they emit a specialized diagnostic. +// All diagnostics returned by these functions must expect the same three +// arguments: +// %0: Cast Type (a value from the CastType enumeration) +// %1: Source Type +// %2: Destination Type +static TryCastResult TryLValueToRValueCast(Sema &Self, Expr *SrcExpr, + QualType DestType, unsigned &msg); +static TryCastResult TryStaticReferenceDowncast(Sema &Self, Expr *SrcExpr, + QualType DestType, bool CStyle, + const SourceRange &OpRange, + unsigned &msg); +static TryCastResult TryStaticPointerDowncast(Sema &Self, QualType SrcType, + QualType DestType, bool CStyle, + const SourceRange &OpRange, + unsigned &msg); +static TryCastResult TryStaticDowncast(Sema &Self, QualType SrcType, + QualType DestType, bool CStyle, + const SourceRange &OpRange, + QualType OrigSrcType, + QualType OrigDestType, unsigned &msg); +static TryCastResult TryStaticMemberPointerUpcast(Sema &Self, QualType SrcType, + QualType DestType,bool CStyle, + const SourceRange &OpRange, + unsigned &msg); +static TryCastResult TryStaticImplicitCast(Sema &Self, Expr *SrcExpr, + QualType DestType, bool CStyle, + const SourceRange &OpRange, + unsigned &msg, + CastExpr::CastKind &Kind, + CXXMethodDecl *&ConversionDecl); +static TryCastResult TryStaticCast(Sema &Self, Expr *SrcExpr, + QualType DestType, bool CStyle, + const SourceRange &OpRange, + unsigned &msg, + CastExpr::CastKind &Kind, + CXXMethodDecl *&ConversionDecl); +static TryCastResult TryConstCast(Sema &Self, Expr *SrcExpr, QualType DestType, + bool CStyle, unsigned &msg); +static TryCastResult TryReinterpretCast(Sema &Self, Expr *SrcExpr, + QualType DestType, bool CStyle, + const SourceRange &OpRange, + unsigned &msg, + CastExpr::CastKind &Kind); + +/// 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>(); + // FIXME: Preserve type source info. + QualType DestType = GetTypeFromParser(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: { + CastExpr::CastKind Kind = CastExpr::CK_Unknown; + if (!TypeDependent) + CheckDynamicCast(*this, Ex, DestType, OpRange, DestRange, Kind); + return Owned(new (Context)CXXDynamicCastExpr(DestType.getNonReferenceType(), + Kind, Ex, DestType, OpLoc)); + } + case tok::kw_reinterpret_cast: { + CastExpr::CastKind Kind = CastExpr::CK_Unknown; + if (!TypeDependent) + CheckReinterpretCast(*this, Ex, DestType, OpRange, DestRange, Kind); + return Owned(new (Context) CXXReinterpretCastExpr( + DestType.getNonReferenceType(), + Kind, Ex, DestType, OpLoc)); + } + case tok::kw_static_cast: { + CastExpr::CastKind Kind = CastExpr::CK_Unknown; + if (!TypeDependent) { + CXXMethodDecl *Method = 0; + + CheckStaticCast(*this, Ex, DestType, OpRange, Kind, Method); + + if (Method) { + OwningExprResult CastArg + = BuildCXXCastArgument(OpLoc, DestType.getNonReferenceType(), + Kind, Method, Owned(Ex)); + if (CastArg.isInvalid()) + return ExprError(); + + Ex = CastArg.takeAs<Expr>(); + } + } + + return Owned(new (Context) CXXStaticCastExpr(DestType.getNonReferenceType(), + Kind, Ex, DestType, OpLoc)); + } + } + + return ExprError(); +} + +/// 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<Qualifiers, 8> cv1, cv2; + + // Find the qualifications. + while (Self.UnwrapSimilarPointerTypes(UnwrappedSrcType, UnwrappedDestType)) { + cv1.push_back(UnwrappedSrcType.getQualifiers()); + cv2.push_back(UnwrappedDestType.getQualifiers()); + } + 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; + ASTContext &Context = Self.Context; + for (llvm::SmallVector<Qualifiers, 8>::reverse_iterator i1 = cv1.rbegin(), + i2 = cv2.rbegin(); + i1 != cv1.rend(); ++i1, ++i2) { + SrcConstruct + = Context.getPointerType(Context.getQualifiedType(SrcConstruct, *i1)); + DestConstruct + = Context.getPointerType(Context.getQualifiedType(DestConstruct, *i2)); + } + + // Test if they're compatible. + return SrcConstruct != DestConstruct && + !Self.IsQualificationConversion(SrcConstruct, DestConstruct); +} + +/// 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. +static void +CheckDynamicCast(Sema &Self, Expr *&SrcExpr, QualType DestType, + const SourceRange &OpRange, + const SourceRange &DestRange, CastExpr::CastKind &Kind) { + 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->getAs<PointerType>(); + const ReferenceType *DestReference = DestType->getAs<ReferenceType>(); + 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->getAs<RecordType>(); + if (DestPointee->isVoidType()) { + assert(DestPointer && "Reference to void is not possible"); + } else if (DestRecord) { + if (Self.RequireCompleteType(OpRange.getBegin(), DestPointee, + PDiag(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->getAs<PointerType>()) { + 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) + << CT_Dynamic << OrigSrcType << OrigDestType << OpRange; + } + SrcPointee = SrcType; + } else { + SrcPointee = SrcType; + } + + const RecordType *SrcRecord = SrcPointee->getAs<RecordType>(); + if (SrcRecord) { + if (Self.RequireCompleteType(OpRange.getBegin(), SrcPointee, + PDiag(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) + << CT_Dynamic << OrigSrcType << OrigDestType << 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); + Kind = CastExpr::CK_DerivedToBase; + // 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. + Kind = CastExpr::CK_Dynamic; +} + +/// 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) { + if (!DestType->isLValueReferenceType()) + Self.DefaultFunctionArrayConversion(SrcExpr); + + unsigned msg = diag::err_bad_cxx_cast_generic; + if (TryConstCast(Self, SrcExpr, DestType, /*CStyle*/false, msg) != TC_Success + && msg != 0) + Self.Diag(OpRange.getBegin(), msg) << CT_Const + << SrcExpr->getType() << DestType << OpRange; +} + +/// 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, + CastExpr::CastKind &Kind) { + if (!DestType->isLValueReferenceType()) + Self.DefaultFunctionArrayConversion(SrcExpr); + + unsigned msg = diag::err_bad_cxx_cast_generic; + if (TryReinterpretCast(Self, SrcExpr, DestType, /*CStyle*/false, OpRange, + msg, Kind) + != TC_Success && msg != 0) + Self.Diag(OpRange.getBegin(), msg) << CT_Reinterpret + << SrcExpr->getType() << DestType << OpRange; +} + + +/// 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, CastExpr::CastKind &Kind, + CXXMethodDecl *&ConversionDecl) { + // This test is outside everything else because it's the only case where + // a non-lvalue-reference target type does not lead to decay. + // C++ 5.2.9p4: Any expression can be explicitly converted to type "cv void". + if (DestType->isVoidType()) { + return; + } + + if (!DestType->isLValueReferenceType()) + Self.DefaultFunctionArrayConversion(SrcExpr); + + unsigned msg = diag::err_bad_cxx_cast_generic; + if (TryStaticCast(Self, SrcExpr, DestType, /*CStyle*/false,OpRange, msg, + Kind, ConversionDecl) + != TC_Success && msg != 0) + Self.Diag(OpRange.getBegin(), msg) << CT_Static + << SrcExpr->getType() << DestType << OpRange; +} + +/// TryStaticCast - Check if a static cast can be performed, and do so if +/// possible. If @p CStyle, ignore access restrictions on hierarchy casting +/// and casting away constness. +static TryCastResult TryStaticCast(Sema &Self, Expr *SrcExpr, + QualType DestType, bool CStyle, + const SourceRange &OpRange, unsigned &msg, + CastExpr::CastKind &Kind, + CXXMethodDecl *&ConversionDecl) { + // 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. + + // C++ 5.2.9p4: Any expression can be explicitly converted to type "cv void". + // Done outside this function. + + TryCastResult tcr; + + // C++ 5.2.9p5, reference downcast. + // See the function for details. + // DR 427 specifies that this is to be applied before paragraph 2. + tcr = TryStaticReferenceDowncast(Self, SrcExpr, DestType, CStyle,OpRange,msg); + if (tcr != TC_NotApplicable) + return tcr; + + // 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". + tcr = TryLValueToRValueCast(Self, SrcExpr, DestType, msg); + if (tcr != TC_NotApplicable) + return tcr; + + // C++ 5.2.9p2: An expression e can be explicitly converted to a type T + // [...] if the declaration "T t(e);" is well-formed, [...]. + tcr = TryStaticImplicitCast(Self, SrcExpr, DestType, CStyle, OpRange, msg, + Kind, ConversionDecl); + if (tcr != TC_NotApplicable) + return tcr; + + // 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. + // In the CStyle case, the earlier attempt to const_cast should have taken + // care of reverse qualification conversions. + + QualType OrigSrcType = SrcExpr->getType(); + + 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 TC_Success; + } + + // Reverse pointer upcast. C++ 4.10p3 specifies pointer upcast. + // C++ 5.2.9p8 additionally disallows a cast path through virtual inheritance. + tcr = TryStaticPointerDowncast(Self, SrcType, DestType, CStyle, OpRange, msg); + if (tcr != TC_NotApplicable) + return tcr; + + // 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. + tcr = TryStaticMemberPointerUpcast(Self, SrcType, DestType, CStyle, + OpRange, msg); + if (tcr != TC_NotApplicable) + return tcr; + + // 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->getAs<PointerType>()) { + QualType SrcPointee = SrcPointer->getPointeeType(); + if (SrcPointee->isVoidType()) { + if (const PointerType *DestPointer = DestType->getAs<PointerType>()) { + QualType DestPointee = DestPointer->getPointeeType(); + if (DestPointee->isIncompleteOrObjectType()) { + // This is definitely the intended conversion, but it might fail due + // to a const violation. + if (!CStyle && !DestPointee.isAtLeastAsQualifiedAs(SrcPointee)) { + msg = diag::err_bad_cxx_cast_const_away; + return TC_Failed; + } + return TC_Success; + } + } + } + } + + // We tried everything. Everything! Nothing works! :-( + return TC_NotApplicable; +} + +/// Tests whether a conversion according to N2844 is valid. +TryCastResult +TryLValueToRValueCast(Sema &Self, Expr *SrcExpr, QualType DestType, + unsigned &msg) { + // 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->getAs<RValueReferenceType>(); + if (!R) + return TC_NotApplicable; + + if (SrcExpr->isLvalue(Self.Context) != Expr::LV_Valid) + return TC_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. + // FIXME: Should allow casting away constness if CStyle. + bool DerivedToBase; + if (Self.CompareReferenceRelationship(SrcExpr->getType(), R->getPointeeType(), + DerivedToBase) < + Sema::Ref_Compatible_With_Added_Qualification) { + msg = diag::err_bad_lvalue_to_rvalue_cast; + return TC_Failed; + } + + // FIXME: Similar to CheckReferenceInit, we actually need more AST annotation + // than nothing. + return TC_Success; +} + +/// Tests whether a conversion according to C++ 5.2.9p5 is valid. +TryCastResult +TryStaticReferenceDowncast(Sema &Self, Expr *SrcExpr, QualType DestType, + bool CStyle, const SourceRange &OpRange, + unsigned &msg) { + // 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. + + const ReferenceType *DestReference = DestType->getAs<ReferenceType>(); + if (!DestReference) { + return TC_NotApplicable; + } + bool RValueRef = DestReference->isRValueReferenceType(); + if (!RValueRef && SrcExpr->isLvalue(Self.Context) != Expr::LV_Valid) { + // We know the left side is an lvalue reference, so we can suggest a reason. + msg = diag::err_bad_cxx_cast_rvalue; + return TC_NotApplicable; + } + + QualType DestPointee = DestReference->getPointeeType(); + + return TryStaticDowncast(Self, SrcExpr->getType(), DestPointee, CStyle, + OpRange, SrcExpr->getType(), DestType, msg); +} + +/// Tests whether a conversion according to C++ 5.2.9p8 is valid. +TryCastResult +TryStaticPointerDowncast(Sema &Self, QualType SrcType, QualType DestType, + bool CStyle, const SourceRange &OpRange, + unsigned &msg) { + // 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 *DestPointer = DestType->getAs<PointerType>(); + if (!DestPointer) { + return TC_NotApplicable; + } + + const PointerType *SrcPointer = SrcType->getAs<PointerType>(); + if (!SrcPointer) { + msg = diag::err_bad_static_cast_pointer_nonpointer; + return TC_NotApplicable; + } + + return TryStaticDowncast(Self, SrcPointer->getPointeeType(), + DestPointer->getPointeeType(), CStyle, + OpRange, SrcType, DestType, msg); +} + +/// 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. +TryCastResult +TryStaticDowncast(Sema &Self, QualType SrcType, QualType DestType, + bool CStyle, const SourceRange &OpRange, QualType OrigSrcType, + QualType OrigDestType, unsigned &msg) { + // Downcast can only happen in class hierarchies, so we need classes. + if (!DestType->isRecordType() || !SrcType->isRecordType()) { + return TC_NotApplicable; + } + + CXXBasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/!CStyle, + /*DetectVirtual=*/true); + if (!Self.IsDerivedFrom(DestType, SrcType, Paths)) { + return TC_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, unless we're in C-style mode. + if (!CStyle && !DestType.isAtLeastAsQualifiedAs(SrcType)) { + msg = diag::err_bad_cxx_cast_const_away; + return TC_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. + if (!Paths.isRecordingPaths()) { + Paths.clear(); + Paths.setRecordingPaths(true); + Self.IsDerivedFrom(DestType, SrcType, Paths); + } + std::string PathDisplayStr; + std::set<unsigned> DisplayedPaths; + for (CXXBasePaths::paths_iterator PI = Paths.begin(), PE = Paths.end(); + PI != PE; ++PI) { + if (DisplayedPaths.insert(PI->back().SubobjectNumber).second) { + // We haven't displayed a path to this particular base + // class subobject yet. + PathDisplayStr += "\n "; + for (CXXBasePath::const_reverse_iterator EI = PI->rbegin(), + EE = PI->rend(); + EI != EE; ++EI) + PathDisplayStr += EI->Base->getType().getAsString() + " -> "; + PathDisplayStr += DestType.getAsString(); + } + } + + Self.Diag(OpRange.getBegin(), diag::err_ambiguous_base_to_derived_cast) + << SrcType.getUnqualifiedType() << DestType.getUnqualifiedType() + << PathDisplayStr << OpRange; + msg = 0; + return TC_Failed; + } + + if (Paths.getDetectedVirtual() != 0) { + QualType VirtualBase(Paths.getDetectedVirtual(), 0); + Self.Diag(OpRange.getBegin(), diag::err_static_downcast_via_virtual) + << OrigSrcType << OrigDestType << VirtualBase << OpRange; + msg = 0; + return TC_Failed; + } + + if (!CStyle && Self.CheckBaseClassAccess(DestType, SrcType, + diag::err_downcast_from_inaccessible_base, Paths, + OpRange.getBegin(), DeclarationName())) { + msg = 0; + return TC_Failed; + } + + return TC_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 [...]. +/// +TryCastResult +TryStaticMemberPointerUpcast(Sema &Self, QualType SrcType, QualType DestType, + bool CStyle, const SourceRange &OpRange, + unsigned &msg) { + const MemberPointerType *DestMemPtr = DestType->getAs<MemberPointerType>(); + if (!DestMemPtr) + return TC_NotApplicable; + const MemberPointerType *SrcMemPtr = SrcType->getAs<MemberPointerType>(); + if (!SrcMemPtr) { + msg = diag::err_bad_static_cast_member_pointer_nonmp; + return TC_NotApplicable; + } + + // T == T, modulo cv + if (Self.Context.getCanonicalType( + SrcMemPtr->getPointeeType().getUnqualifiedType()) != + Self.Context.getCanonicalType(DestMemPtr->getPointeeType(). + getUnqualifiedType())) + return TC_NotApplicable; + + // B base of D + QualType SrcClass(SrcMemPtr->getClass(), 0); + QualType DestClass(DestMemPtr->getClass(), 0); + CXXBasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/!CStyle, + /*DetectVirtual=*/true); + if (!Self.IsDerivedFrom(SrcClass, DestClass, Paths)) { + return TC_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; + msg = 0; + return TC_Failed; + } + + if (const RecordType *VBase = Paths.getDetectedVirtual()) { + Self.Diag(OpRange.getBegin(), diag::err_memptr_conv_via_virtual) + << SrcClass << DestClass << QualType(VBase, 0) << OpRange; + msg = 0; + return TC_Failed; + } + + if (!CStyle && Self.CheckBaseClassAccess(DestType, SrcType, + diag::err_downcast_from_inaccessible_base, Paths, + OpRange.getBegin(), DeclarationName())) { + msg = 0; + return TC_Failed; + } + + return TC_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 [...]. +TryCastResult +TryStaticImplicitCast(Sema &Self, Expr *SrcExpr, QualType DestType, + bool CStyle, const SourceRange &OpRange, unsigned &msg, + CastExpr::CastKind &Kind, + CXXMethodDecl *&ConversionDecl) { + if (DestType->isRecordType()) { + if (Self.RequireCompleteType(OpRange.getBegin(), DestType, + diag::err_bad_dynamic_cast_incomplete)) { + msg = 0; + return TC_Failed; + } + } + + 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. + // On the other hand, if we're checking a C-style cast, we've still got + // the reinterpret_cast way. In that case, we pass an ICS so we don't + // get error messages. + ImplicitConversionSequence ICS; + bool failed = Self.CheckReferenceInit(SrcExpr, DestType, + OpRange.getBegin(), + /*SuppressUserConversions=*/false, + /*AllowExplicit=*/false, + /*ForceRValue=*/false, + CStyle ? &ICS : 0); + if (!failed) + return TC_Success; + if (CStyle) + return TC_NotApplicable; + // If we didn't pass the ICS, we already got an error message. + msg = 0; + return TC_Failed; + } + + // FIXME: To get a proper error from invalid conversions here, we need to + // reimplement more of this. + // FIXME: This does not actually perform the conversion, and thus does not + // check for ambiguity or access. + ImplicitConversionSequence ICS = + Self.TryImplicitConversion(SrcExpr, DestType, + /*SuppressUserConversions=*/false, + /*AllowExplicit=*/true, + /*ForceRValue=*/false, + /*InOverloadResolution=*/false, + /*one of user provided casts*/true); + + if (ICS.ConversionKind == ImplicitConversionSequence::BadConversion) + return TC_NotApplicable; + + if (ICS.ConversionKind == ImplicitConversionSequence::UserDefinedConversion) { + ConversionDecl = cast<CXXMethodDecl>(ICS.UserDefined.ConversionFunction); + if (isa<CXXConstructorDecl>(ConversionDecl)) + Kind = CastExpr::CK_ConstructorConversion; + else if (isa<CXXConversionDecl>(ConversionDecl)) + Kind = CastExpr::CK_UserDefinedConversion; + } else if (ICS.ConversionKind == + ImplicitConversionSequence::StandardConversion) { + // FIXME: Set the cast kind depending on which types of conversions we have. + } + + return TC_Success; +} + +/// TryConstCast - See if a const_cast from source to destination is allowed, +/// and perform it if it is. +static TryCastResult TryConstCast(Sema &Self, Expr *SrcExpr, QualType DestType, + bool CStyle, unsigned &msg) { + DestType = Self.Context.getCanonicalType(DestType); + QualType SrcType = SrcExpr->getType(); + if (const LValueReferenceType *DestTypeTmp = + DestType->getAs<LValueReferenceType>()) { + if (SrcExpr->isLvalue(Self.Context) != Expr::LV_Valid) { + // Cannot const_cast non-lvalue to lvalue reference type. But if this + // is C-style, static_cast might find a way, so we simply suggest a + // message and tell the parent to keep searching. + msg = diag::err_bad_cxx_cast_rvalue; + return TC_NotApplicable; + } + + // 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); + } + + // 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 [...] + if (!CStyle) + msg = diag::err_bad_const_cast_dest; + return TC_NotApplicable; + } + 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. + if (!CStyle) + msg = diag::err_bad_const_cast_dest; + return TC_NotApplicable; + } + 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(); + } + + // Since we're dealing in canonical types, the remainder must be the same. + if (SrcType != DestType) + return TC_NotApplicable; + + return TC_Success; +} + +static TryCastResult TryReinterpretCast(Sema &Self, Expr *SrcExpr, + QualType DestType, bool CStyle, + const SourceRange &OpRange, + unsigned &msg, + CastExpr::CastKind &Kind) { + QualType OrigDestType = DestType, OrigSrcType = SrcExpr->getType(); + + DestType = Self.Context.getCanonicalType(DestType); + QualType SrcType = SrcExpr->getType(); + if (const ReferenceType *DestTypeTmp = DestType->getAs<ReferenceType>()) { + bool LValue = DestTypeTmp->isLValueReferenceType(); + if (LValue && SrcExpr->isLvalue(Self.Context) != Expr::LV_Valid) { + // Cannot cast non-lvalue to reference type. See the similar comment in + // const_cast. + msg = diag::err_bad_cxx_cast_rvalue; + return TC_NotApplicable; + } + + // 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); + } + + // Canonicalize source for comparison. + SrcType = Self.Context.getCanonicalType(SrcType); + + const MemberPointerType *DestMemPtr = DestType->getAs<MemberPointerType>(), + *SrcMemPtr = SrcType->getAs<MemberPointerType>(); + 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()) + return TC_NotApplicable; + + // C++ 5.2.10p2: The reinterpret_cast operator shall not cast away + // constness. + // A reinterpret_cast followed by a const_cast can, though, so in C-style, + // we accept it. + if (!CStyle && CastsAwayConstness(Self, SrcType, DestType)) { + msg = diag::err_bad_cxx_cast_const_away; + return TC_Failed; + } + + // A valid member pointer cast. + return TC_Success; + } + + // 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)) { + msg = diag::err_bad_reinterpret_cast_small_int; + return TC_Failed; + } + Kind = CastExpr::CK_PointerToIntegral; + return TC_Success; + } + + bool destIsVector = DestType->isVectorType(); + bool srcIsVector = SrcType->isVectorType(); + if (srcIsVector || destIsVector) { + bool srcIsScalar = SrcType->isIntegralType() && !SrcType->isEnumeralType(); + bool destIsScalar = + DestType->isIntegralType() && !DestType->isEnumeralType(); + + // Check if this is a cast between a vector and something else. + if (!(srcIsScalar && destIsVector) && !(srcIsVector && destIsScalar) && + !(srcIsVector && destIsVector)) + return TC_NotApplicable; + + // If both types have the same size, we can successfully cast. + if (Self.Context.getTypeSize(SrcType) == Self.Context.getTypeSize(DestType)) + return TC_Success; + + if (destIsScalar) + msg = diag::err_bad_cxx_cast_vector_to_scalar_different_size; + else if (srcIsScalar) + msg = diag::err_bad_cxx_cast_scalar_to_vector_different_size; + else + msg = diag::err_bad_cxx_cast_vector_to_vector_different_size; + + return TC_Failed; + } + + 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. + return TC_NotApplicable; + } + + 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 TC_Success; + } + + // 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)) { + msg = diag::err_bad_reinterpret_cast_small_int; + return TC_Failed; + } + Kind = CastExpr::CK_PointerToIntegral; + return TC_Success; + } + + 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. + Kind = CastExpr::CK_IntegralToPointer; + return TC_Success; + } + + if (!destIsPtr || !srcIsPtr) { + // With the valid non-pointer conversions out of the way, we can be even + // more stringent. + return TC_NotApplicable; + } + + // C++ 5.2.10p2: The reinterpret_cast operator shall not cast away constness. + // The C-style cast operator can. + if (!CStyle && CastsAwayConstness(Self, SrcType, DestType)) { + msg = diag::err_bad_cxx_cast_const_away; + return TC_Failed; + } + + // 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 TC_Success; + } + + // 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_cast_fn_obj) << OpRange; + return TC_Success; + } + + if (DestType->isFunctionPointerType()) { + // See above. + if (!Self.getLangOptions().CPlusPlus0x) + Self.Diag(OpRange.getBegin(), diag::ext_cast_fn_obj) << OpRange; + return TC_Success; + } + + // 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. + Kind = CastExpr::CK_BitCast; + return TC_Success; +} + +bool Sema::CXXCheckCStyleCast(SourceRange R, QualType CastTy, Expr *&CastExpr, + CastExpr::CastKind &Kind, bool FunctionalStyle, + CXXMethodDecl *&ConversionDecl) { + // This test is outside everything else because it's the only case where + // a non-lvalue-reference target type does not lead to decay. + // C++ 5.2.9p4: Any expression can be explicitly converted to type "cv void". + if (CastTy->isVoidType()) + return false; + + // If the type is dependent, we won't do any other semantic analysis now. + if (CastTy->isDependentType() || CastExpr->isTypeDependent()) + return false; + + if (!CastTy->isLValueReferenceType()) + DefaultFunctionArrayConversion(CastExpr); + + // C++ [expr.cast]p5: The conversions performed by + // - a const_cast, + // - a static_cast, + // - a static_cast followed by a const_cast, + // - a reinterpret_cast, or + // - a reinterpret_cast followed by a const_cast, + // can be performed using the cast notation of explicit type conversion. + // [...] If a conversion can be interpreted in more than one of the ways + // listed above, the interpretation that appears first in the list is used, + // even if a cast resulting from that interpretation is ill-formed. + // In plain language, this means trying a const_cast ... + unsigned msg = diag::err_bad_cxx_cast_generic; + TryCastResult tcr = TryConstCast(*this, CastExpr, CastTy, /*CStyle*/true, + msg); + if (tcr == TC_NotApplicable) { + // ... or if that is not possible, a static_cast, ignoring const, ... + tcr = TryStaticCast(*this, CastExpr, CastTy, /*CStyle*/true, R, msg, + Kind, ConversionDecl); + if (tcr == TC_NotApplicable) { + // ... and finally a reinterpret_cast, ignoring const. + tcr = TryReinterpretCast(*this, CastExpr, CastTy, /*CStyle*/true, R, msg, + Kind); + } + } + + if (tcr != TC_Success && msg != 0) + Diag(R.getBegin(), msg) << (FunctionalStyle ? CT_Functional : CT_CStyle) + << CastExpr->getType() << CastTy << R; + + return tcr != TC_Success; +} |