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llvm-project/clang/lib/Sema/SemaNamedCast.cpp

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//===--- 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 "clang/Basic/Diagnostic.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 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);
switch (Kind) {
default: assert(0 && "Unknown C++ cast!");
case tok::kw_const_cast:
CheckConstCast(*this, Ex, DestType, OpRange, DestRange);
return new CXXConstCastExpr(DestType.getNonReferenceType(), Ex,
DestType, OpLoc);
case tok::kw_dynamic_cast:
CheckDynamicCast(*this, Ex, DestType, OpRange, DestRange);
return new CXXDynamicCastExpr(DestType.getNonReferenceType(), Ex,
DestType, OpLoc);
case tok::kw_reinterpret_cast:
CheckReinterpretCast(*this, Ex, DestType, OpRange, DestRange);
return new CXXReinterpretCastExpr(DestType.getNonReferenceType(), Ex,
DestType, OpLoc);
case tok::kw_static_cast:
CheckStaticCast(*this, Ex, DestType, OpRange);
return new 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.getAsString()
<< 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();
}
if (!DestType->isPointerType()) {
// 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.getAsString() << DestRange;
return;
}
if (DestType->isFunctionPointerType()) {
// 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.getAsString() << 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.getAsString()
<< OrigSrcType.getAsString() << 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.getAsString()
<< OrigSrcType.getAsString() << 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.getAsString()
<< 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);
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.getAsString()
<< OrigSrcType.getAsString() << 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 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.getAsString() << 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.getAsString()
<< OrigSrcType.getAsString() << 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.getAsString()
<< OrigSrcType.getAsString() << 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;
}
// FIXME: Handle member pointers.
// 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;
}
// FIXME: Handle member pointers.
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 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.
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++ 5.11 specifies member pointer
// conversion. C++ 5.2.9p9 has additional information.
// DR54's access restrictions apply here also.
// FIXME: Don't have member pointers yet.
// 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.getAsString()
<< OrigSrcType.getAsString() << 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.getAsString() << OrigSrcType.getAsString()
<< 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.getAsString()
<< OrigSrcType.getAsString() << 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().getAsString()
<< DestType.getUnqualifiedType().getAsString()
<< 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.getAsString() << OrigDestType.getAsString()
<< VirtualBase.getAsString() << 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.getAsString() << DestRange;
return;
}
const RecordType *DestRecord = DestPointee->getAsRecordType();
if (DestPointee->isVoidType()) {
assert(DestPointer && "Reference to void is not possible");
} else if (DestRecord) {
if (!DestRecord->getDecl()->isDefinition()) {
Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_incomplete)
<< DestPointee.getUnqualifiedType().getAsString() << DestRange;
return;
}
} else {
Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_class)
<< DestPointee.getUnqualifiedType().getAsString() << 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.getAsString() << 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.getAsString() << OpRange;
}
SrcPointee = SrcType;
}
const RecordType *SrcRecord = SrcPointee->getAsRecordType();
if (SrcRecord) {
if (!SrcRecord->getDecl()->isDefinition()) {
Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_incomplete)
<< SrcPointee.getUnqualifiedType().getAsString()
<< SrcExpr->getSourceRange();
return;
}
} else {
Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_class)
<< SrcPointee.getUnqualifiedType().getAsString()
<< 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.getAsString()
<< OrigSrcType.getAsString() << 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().getAsString()
<< SrcExpr->getSourceRange();
}
// Done. Everything else is run-time checks.
}
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