| //===--- 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 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); |
| static void CheckStaticCast(Sema &Self, Expr *&SrcExpr, QualType DestType, |
| const SourceRange &OpRange, |
| CastExpr::CastKind &Kind); |
| 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); |
| static TryCastResult TryStaticCast(Sema &Self, Expr *SrcExpr, |
| QualType DestType, bool CStyle, |
| const SourceRange &OpRange, |
| CastExpr::CastKind &Kind, unsigned &msg); |
| 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); |
| |
| /// 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: |
| if (!TypeDependent) |
| CheckReinterpretCast(*this, Ex, DestType, OpRange, DestRange); |
| return Owned(new (Context) CXXReinterpretCastExpr( |
| DestType.getNonReferenceType(), |
| Ex, DestType, OpLoc)); |
| |
| case tok::kw_static_cast: { |
| CastExpr::CastKind Kind = CastExpr::CK_Unknown; |
| if (!TypeDependent) |
| CheckStaticCast(*this, Ex, DestType, OpRange, Kind); |
| 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<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); |
| } |
| |
| /// 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, |
| 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, |
| 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) |
| { |
| if (!DestType->isLValueReferenceType()) |
| Self.DefaultFunctionArrayConversion(SrcExpr); |
| |
| unsigned msg = diag::err_bad_cxx_cast_generic; |
| if (TryReinterpretCast(Self, SrcExpr, DestType, /*CStyle*/false, OpRange, msg) |
| != 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) |
| { |
| // 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, |
| Kind, msg) |
| != 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, |
| CastExpr::CastKind &Kind, unsigned &msg) |
| { |
| // 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); |
| 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; |
| } |
| |
| BasePaths 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 (BasePaths::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 (BasePath::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); |
| BasePaths 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) |
| { |
| 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, 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; |
| } |
| if (DestType->isRecordType()) { |
| // There are no further possibilities for the target type being a class, |
| // neither in static_cast nor in a C-style cast. So we can fail here. |
| // FIXME: We need to store this constructor in the AST. |
| if (Self.PerformInitializationByConstructor(DestType, &SrcExpr, 1, |
| OpRange.getBegin(), OpRange, DeclarationName(), Sema::IK_Direct)) |
| return TC_Success; |
| // The function already emitted an error. |
| 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); |
| return ICS.ConversionKind == ImplicitConversionSequence::BadConversion ? |
| TC_NotApplicable : 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) { |
| 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; |
| } |
| return TC_Success; |
| } |
| |
| 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; |
| } |
| 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. |
| 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. |
| return TC_Success; |
| } |
| |
| bool Sema::CXXCheckCStyleCast(SourceRange R, QualType CastTy, Expr *&CastExpr, |
| CastExpr::CastKind &Kind, bool FunctionalStyle) |
| { |
| // 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, Kind, msg); |
| if (tcr == TC_NotApplicable) { |
| // ... and finally a reinterpret_cast, ignoring const. |
| tcr = TryReinterpretCast(*this, CastExpr, CastTy, /*CStyle*/true, R, msg); |
| } |
| } |
| |
| if (tcr != TC_Success && msg != 0) |
| Diag(R.getBegin(), msg) << (FunctionalStyle ? CT_Functional : CT_CStyle) |
| << CastExpr->getType() << CastTy << R; |
| |
| return tcr != TC_Success; |
| } |
