//===--- 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,
CastExpr::CastKind &Kind);
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.
static 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, Kind);
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) {
// We can only work with complete types. But don't complain if it doesn't work
if (Self.RequireCompleteType(OpRange.getBegin(), SrcType, PDiag(0)) ||
Self.RequireCompleteType(OpRange.getBegin(), DestType, PDiag(0)))
return TC_NotApplicable;
// 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, CastExpr::CastKind &Kind) {
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;
}
Kind = CastExpr::CK_DerivedToBaseMemberPointer;
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.
Kind = CastExpr::CK_BitCast;
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.
Kind = CastExpr::CK_BitCast;
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()) {
Kind = CastExpr::CK_ToVoid;
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_Success)
Kind = CastExpr::CK_NoOp;
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;
}