| //===--- 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 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::ExprResult |
| Sema::ActOnCXXNamedCast(SourceLocation OpLoc, tok::TokenKind Kind, |
| SourceLocation LAngleBracketLoc, TypeTy *Ty, |
| SourceLocation RAngleBracketLoc, |
| SourceLocation LParenLoc, ExprTy *E, |
| SourceLocation RParenLoc) { |
| Expr *Ex = (Expr*)E; |
| 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 new (Context) CXXConstCastExpr(DestType.getNonReferenceType(), Ex, |
| DestType, OpLoc); |
| |
| case tok::kw_dynamic_cast: |
| if (!TypeDependent) |
| CheckDynamicCast(*this, Ex, DestType, OpRange, DestRange); |
| return new (Context)CXXDynamicCastExpr(DestType.getNonReferenceType(), Ex, |
| DestType, OpLoc); |
| |
| case tok::kw_reinterpret_cast: |
| if (!TypeDependent) |
| CheckReinterpretCast(*this, Ex, DestType, OpRange, DestRange); |
| return new (Context) CXXReinterpretCastExpr(DestType.getNonReferenceType(), |
| Ex, DestType, OpLoc); |
| |
| case tok::kw_static_cast: |
| if (!TypeDependent) |
| CheckStaticCast(*this, Ex, DestType, OpRange); |
| return new (Context) CXXStaticCastExpr(DestType.getNonReferenceType(), Ex, |
| DestType, OpLoc); |
| } |
| |
| return true; |
| } |
| |
| /// 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 ReferenceType *DestTypeTmp = DestType->getAsReferenceType()) { |
| 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) |
| << "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. |
| // 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 ReferenceType *DestTypeTmp = DestType->getAsReferenceType()) { |
| 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 { |
| // 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; |
| } |
| |
| bool destIsPtr = DestType->isPointerType(); |
| bool srcIsPtr = SrcType->isPointerType(); |
| if (!destIsPtr && !srcIsPtr) { |
| // Except for std::nullptr_t->integer, which is not supported yet, and |
| // lvalue->reference, which is 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. |
| |
| // 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; |
| } |
| |
| // 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->isObjectType()) { |
| // 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 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++ 5.2.7p2: If T is a pointer type, v shall be an rvalue of a pointer to |
| // complete class type, [...]. If T is a reference type, v shall be an |
| // lvalue of a complete 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 (SrcExpr->isLvalue(Self.Context) != Expr::LV_Valid) { |
| Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_rvalue) |
| << "dynamic_cast" << OrigDestType << OpRange; |
| } |
| 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. |
| } |