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SemaCast.cpp
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//===--- SemaCast.cpp - Semantic Analysis for Casts -----------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements semantic analysis for cast expressions, including
// 1) C-style casts like '(int) x'
// 2) C++ functional casts like 'int(x)'
// 3) C++ named casts like 'static_cast<int>(x)'
//
//===----------------------------------------------------------------------===//
#include "clang/AST/ASTContext.h"
#include "clang/AST/ASTStructuralEquivalence.h"
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/ExprObjC.h"
#include "clang/AST/RecordLayout.h"
#include "clang/Basic/PartialDiagnostic.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Sema/Initialization.h"
#include "clang/Sema/SemaHLSL.h"
#include "clang/Sema/SemaObjC.h"
#include "clang/Sema/SemaRISCV.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.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_Extension, ///< The cast method is appropriate and accepted as a
///< language extension.
TC_Failed ///< The cast method is appropriate, but failed. A
///< diagnostic has been emitted.
};
static bool isValidCast(TryCastResult TCR) {
return TCR == TC_Success || TCR == TC_Extension;
}
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)
CT_Addrspace ///< addrspace_cast
};
namespace {
struct CastOperation {
CastOperation(Sema &S, QualType destType, ExprResult src)
: Self(S), SrcExpr(src), DestType(destType),
ResultType(destType.getNonLValueExprType(S.Context)),
ValueKind(Expr::getValueKindForType(destType)),
Kind(CK_Dependent), IsARCUnbridgedCast(false) {
// C++ [expr.type]/8.2.2:
// If a pr-value initially has the type cv-T, where T is a
// cv-unqualified non-class, non-array type, the type of the
// expression is adjusted to T prior to any further analysis.
// C23 6.5.4p6:
// Preceding an expression by a parenthesized type name converts the
// value of the expression to the unqualified, non-atomic version of
// the named type.
// Don't drop __ptrauth qualifiers. We want to treat casting to a
// __ptrauth-qualified type as an error instead of implicitly ignoring
// the qualifier.
if (!S.Context.getLangOpts().ObjC && !DestType->isRecordType() &&
!DestType->isArrayType() && !DestType.getPointerAuth()) {
DestType = DestType.getAtomicUnqualifiedType();
}
if (const BuiltinType *placeholder =
src.get()->getType()->getAsPlaceholderType()) {
PlaceholderKind = placeholder->getKind();
} else {
PlaceholderKind = (BuiltinType::Kind) 0;
}
}
Sema &Self;
ExprResult SrcExpr;
QualType DestType;
QualType ResultType;
ExprValueKind ValueKind;
CastKind Kind;
BuiltinType::Kind PlaceholderKind;
CXXCastPath BasePath;
bool IsARCUnbridgedCast;
SourceRange OpRange;
SourceRange DestRange;
// Top-level semantics-checking routines.
void CheckConstCast();
void CheckReinterpretCast();
void CheckStaticCast();
void CheckDynamicCast();
void CheckCXXCStyleCast(bool FunctionalCast, bool ListInitialization);
bool CheckHLSLCStyleCast(CheckedConversionKind CCK);
void CheckCStyleCast();
void CheckBuiltinBitCast();
void CheckAddrspaceCast();
void updatePartOfExplicitCastFlags(CastExpr *CE) {
// Walk down from the CE to the OrigSrcExpr, and mark all immediate
// ImplicitCastExpr's as being part of ExplicitCastExpr. The original CE
// (which is a ExplicitCastExpr), and the OrigSrcExpr are not touched.
for (; auto *ICE = dyn_cast<ImplicitCastExpr>(CE->getSubExpr()); CE = ICE)
ICE->setIsPartOfExplicitCast(true);
}
/// Complete an apparently-successful cast operation that yields
/// the given expression.
ExprResult complete(CastExpr *castExpr) {
// If this is an unbridged cast, wrap the result in an implicit
// cast that yields the unbridged-cast placeholder type.
if (IsARCUnbridgedCast) {
castExpr = ImplicitCastExpr::Create(
Self.Context, Self.Context.ARCUnbridgedCastTy, CK_Dependent,
castExpr, nullptr, castExpr->getValueKind(),
Self.CurFPFeatureOverrides());
}
updatePartOfExplicitCastFlags(castExpr);
return castExpr;
}
// Internal convenience methods.
/// Try to handle the given placeholder expression kind. Return
/// true if the source expression has the appropriate placeholder
/// kind. A placeholder can only be claimed once.
bool claimPlaceholder(BuiltinType::Kind K) {
if (PlaceholderKind != K) return false;
PlaceholderKind = (BuiltinType::Kind) 0;
return true;
}
bool isPlaceholder() const {
return PlaceholderKind != 0;
}
bool isPlaceholder(BuiltinType::Kind K) const {
return PlaceholderKind == K;
}
bool isBoundPMFConversion() const {
return isPlaceholder(BuiltinType::BoundMember) &&
DestType->isFunctionPointerType() &&
SrcExpr.get()->isBoundMemberFunction(Self.Context);
}
// Language specific cast restrictions for address spaces.
void checkAddressSpaceCast(QualType SrcType, QualType DestType);
void checkCastAlign() {
Self.CheckCastAlign(SrcExpr.get(), DestType, OpRange);
}
void checkObjCConversion(CheckedConversionKind CCK) {
assert(Self.getLangOpts().allowsNonTrivialObjCLifetimeQualifiers());
Expr *src = SrcExpr.get();
if (Self.ObjC().CheckObjCConversion(OpRange, DestType, src, CCK) ==
SemaObjC::ACR_unbridged)
IsARCUnbridgedCast = true;
SrcExpr = src;
}
void checkQualifiedDestType() {
// Destination type may not be qualified with __ptrauth.
if (DestType.getPointerAuth()) {
Self.Diag(DestRange.getBegin(), diag::err_ptrauth_qualifier_cast)
<< DestType << DestRange;
}
}
/// Check for and handle non-overload placeholder expressions.
void checkNonOverloadPlaceholders() {
if (!isPlaceholder() || isPlaceholder(BuiltinType::Overload))
return;
SrcExpr = Self.CheckPlaceholderExpr(SrcExpr.get());
if (SrcExpr.isInvalid())
return;
PlaceholderKind = (BuiltinType::Kind) 0;
}
};
void CheckNoDeref(Sema &S, const QualType FromType, const QualType ToType,
SourceLocation OpLoc) {
if (const auto *PtrType = dyn_cast<PointerType>(FromType)) {
if (PtrType->getPointeeType()->hasAttr(attr::NoDeref)) {
if (const auto *DestType = dyn_cast<PointerType>(ToType)) {
if (!DestType->getPointeeType()->hasAttr(attr::NoDeref)) {
S.Diag(OpLoc, diag::warn_noderef_to_dereferenceable_pointer);
}
}
}
}
}
struct CheckNoDerefRAII {
CheckNoDerefRAII(CastOperation &Op) : Op(Op) {}
~CheckNoDerefRAII() {
if (!Op.SrcExpr.isInvalid())
CheckNoDeref(Op.Self, Op.SrcExpr.get()->getType(), Op.ResultType,
Op.OpRange.getBegin());
}
CastOperation &Op;
};
}
static void DiagnoseCastQual(Sema &Self, const ExprResult &SrcExpr,
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, bool CStyle,
CastKind &Kind,
CXXCastPath &BasePath,
unsigned &msg);
static TryCastResult TryStaticReferenceDowncast(Sema &Self, Expr *SrcExpr,
QualType DestType, bool CStyle,
SourceRange OpRange,
unsigned &msg,
CastKind &Kind,
CXXCastPath &BasePath);
static TryCastResult TryStaticPointerDowncast(Sema &Self, QualType SrcType,
QualType DestType, bool CStyle,
SourceRange OpRange,
unsigned &msg,
CastKind &Kind,
CXXCastPath &BasePath);
static TryCastResult TryStaticDowncast(Sema &Self, CanQualType SrcType,
CanQualType DestType, bool CStyle,
SourceRange OpRange,
QualType OrigSrcType,
QualType OrigDestType, unsigned &msg,
CastKind &Kind,
CXXCastPath &BasePath);
static TryCastResult
TryStaticMemberPointerUpcast(Sema &Self, ExprResult &SrcExpr, QualType SrcType,
QualType DestType, bool CStyle,
SourceRange OpRange, unsigned &msg, CastKind &Kind,
CXXCastPath &BasePath);
static TryCastResult
TryStaticImplicitCast(Sema &Self, ExprResult &SrcExpr, QualType DestType,
CheckedConversionKind CCK, SourceRange OpRange,
unsigned &msg, CastKind &Kind, bool ListInitialization);
static TryCastResult TryStaticCast(Sema &Self, ExprResult &SrcExpr,
QualType DestType, CheckedConversionKind CCK,
SourceRange OpRange, unsigned &msg,
CastKind &Kind, CXXCastPath &BasePath,
bool ListInitialization);
static TryCastResult TryConstCast(Sema &Self, ExprResult &SrcExpr,
QualType DestType, bool CStyle,
unsigned &msg);
static TryCastResult TryReinterpretCast(Sema &Self, ExprResult &SrcExpr,
QualType DestType, bool CStyle,
SourceRange OpRange, unsigned &msg,
CastKind &Kind);
static TryCastResult TryAddressSpaceCast(Sema &Self, ExprResult &SrcExpr,
QualType DestType, bool CStyle,
unsigned &msg, CastKind &Kind);
ExprResult
Sema::ActOnCXXNamedCast(SourceLocation OpLoc, tok::TokenKind Kind,
SourceLocation LAngleBracketLoc, Declarator &D,
SourceLocation RAngleBracketLoc,
SourceLocation LParenLoc, Expr *E,
SourceLocation RParenLoc) {
assert(!D.isInvalidType());
TypeSourceInfo *TInfo = GetTypeForDeclaratorCast(D, E->getType());
if (D.isInvalidType())
return ExprError();
if (getLangOpts().CPlusPlus) {
// Check that there are no default arguments (C++ only).
CheckExtraCXXDefaultArguments(D);
}
return BuildCXXNamedCast(OpLoc, Kind, TInfo, E,
SourceRange(LAngleBracketLoc, RAngleBracketLoc),
SourceRange(LParenLoc, RParenLoc));
}
ExprResult
Sema::BuildCXXNamedCast(SourceLocation OpLoc, tok::TokenKind Kind,
TypeSourceInfo *DestTInfo, Expr *E,
SourceRange AngleBrackets, SourceRange Parens) {
ExprResult Ex = E;
QualType DestType = DestTInfo->getType();
// If the type is dependent, we won't do the semantic analysis now.
bool TypeDependent =
DestType->isDependentType() || Ex.get()->isTypeDependent();
CastOperation Op(*this, DestType, E);
Op.OpRange = SourceRange(OpLoc, Parens.getEnd());
Op.DestRange = AngleBrackets;
Op.checkQualifiedDestType();
switch (Kind) {
default: llvm_unreachable("Unknown C++ cast!");
case tok::kw_addrspace_cast:
if (!TypeDependent) {
Op.CheckAddrspaceCast();
if (Op.SrcExpr.isInvalid())
return ExprError();
}
return Op.complete(CXXAddrspaceCastExpr::Create(
Context, Op.ResultType, Op.ValueKind, Op.Kind, Op.SrcExpr.get(),
DestTInfo, OpLoc, Parens.getEnd(), AngleBrackets));
case tok::kw_const_cast:
if (!TypeDependent) {
Op.CheckConstCast();
if (Op.SrcExpr.isInvalid())
return ExprError();
DiscardMisalignedMemberAddress(DestType.getTypePtr(), E);
}
return Op.complete(CXXConstCastExpr::Create(Context, Op.ResultType,
Op.ValueKind, Op.SrcExpr.get(), DestTInfo,
OpLoc, Parens.getEnd(),
AngleBrackets));
case tok::kw_dynamic_cast: {
// dynamic_cast is not supported in C++ for OpenCL.
if (getLangOpts().OpenCLCPlusPlus) {
return ExprError(Diag(OpLoc, diag::err_openclcxx_not_supported)
<< "dynamic_cast");
}
if (!TypeDependent) {
Op.CheckDynamicCast();
if (Op.SrcExpr.isInvalid())
return ExprError();
}
return Op.complete(CXXDynamicCastExpr::Create(Context, Op.ResultType,
Op.ValueKind, Op.Kind, Op.SrcExpr.get(),
&Op.BasePath, DestTInfo,
OpLoc, Parens.getEnd(),
AngleBrackets));
}
case tok::kw_reinterpret_cast: {
if (!TypeDependent) {
Op.CheckReinterpretCast();
if (Op.SrcExpr.isInvalid())
return ExprError();
DiscardMisalignedMemberAddress(DestType.getTypePtr(), E);
}
return Op.complete(CXXReinterpretCastExpr::Create(Context, Op.ResultType,
Op.ValueKind, Op.Kind, Op.SrcExpr.get(),
nullptr, DestTInfo, OpLoc,
Parens.getEnd(),
AngleBrackets));
}
case tok::kw_static_cast: {
if (!TypeDependent) {
Op.CheckStaticCast();
if (Op.SrcExpr.isInvalid())
return ExprError();
DiscardMisalignedMemberAddress(DestType.getTypePtr(), E);
}
return Op.complete(CXXStaticCastExpr::Create(
Context, Op.ResultType, Op.ValueKind, Op.Kind, Op.SrcExpr.get(),
&Op.BasePath, DestTInfo, CurFPFeatureOverrides(), OpLoc,
Parens.getEnd(), AngleBrackets));
}
}
}
ExprResult Sema::ActOnBuiltinBitCastExpr(SourceLocation KWLoc, Declarator &D,
ExprResult Operand,
SourceLocation RParenLoc) {
assert(!D.isInvalidType());
TypeSourceInfo *TInfo = GetTypeForDeclaratorCast(D, Operand.get()->getType());
if (D.isInvalidType())
return ExprError();
return BuildBuiltinBitCastExpr(KWLoc, TInfo, Operand.get(), RParenLoc);
}
ExprResult Sema::BuildBuiltinBitCastExpr(SourceLocation KWLoc,
TypeSourceInfo *TSI, Expr *Operand,
SourceLocation RParenLoc) {
CastOperation Op(*this, TSI->getType(), Operand);
Op.OpRange = SourceRange(KWLoc, RParenLoc);
TypeLoc TL = TSI->getTypeLoc();
Op.DestRange = SourceRange(TL.getBeginLoc(), TL.getEndLoc());
if (!Operand->isTypeDependent() && !TSI->getType()->isDependentType()) {
Op.CheckBuiltinBitCast();
if (Op.SrcExpr.isInvalid())
return ExprError();
}
BuiltinBitCastExpr *BCE =
new (Context) BuiltinBitCastExpr(Op.ResultType, Op.ValueKind, Op.Kind,
Op.SrcExpr.get(), TSI, KWLoc, RParenLoc);
return Op.complete(BCE);
}
/// Try to diagnose a failed overloaded cast. Returns true if
/// diagnostics were emitted.
static bool tryDiagnoseOverloadedCast(Sema &S, CastType CT,
SourceRange range, Expr *src,
QualType destType,
bool listInitialization) {
switch (CT) {
// These cast kinds don't consider user-defined conversions.
case CT_Const:
case CT_Reinterpret:
case CT_Dynamic:
case CT_Addrspace:
return false;
// These do.
case CT_Static:
case CT_CStyle:
case CT_Functional:
break;
}
QualType srcType = src->getType();
if (!destType->isRecordType() && !srcType->isRecordType())
return false;
InitializedEntity entity = InitializedEntity::InitializeTemporary(destType);
InitializationKind initKind
= (CT == CT_CStyle)? InitializationKind::CreateCStyleCast(range.getBegin(),
range, listInitialization)
: (CT == CT_Functional)? InitializationKind::CreateFunctionalCast(range,
listInitialization)
: InitializationKind::CreateCast(/*type range?*/ range);
InitializationSequence sequence(S, entity, initKind, src);
// It could happen that a constructor failed to be used because
// it requires a temporary of a broken type. Still, it will be found when
// looking for a match.
if (!sequence.Failed())
return false;
switch (sequence.getFailureKind()) {
default: return false;
case InitializationSequence::FK_ParenthesizedListInitFailed:
// In C++20, if the underlying destination type is a RecordType, Clang
// attempts to perform parentesized aggregate initialization if constructor
// overload fails:
//
// C++20 [expr.static.cast]p4:
// An expression E can be explicitly converted to a type T...if overload
// resolution for a direct-initialization...would find at least one viable
// function ([over.match.viable]), or if T is an aggregate type having a
// first element X and there is an implicit conversion sequence from E to
// the type of X.
//
// If that fails, then we'll generate the diagnostics from the failed
// previous constructor overload attempt. Array initialization, however, is
// not done after attempting constructor overloading, so we exit as there
// won't be a failed overload result.
if (destType->isArrayType())
return false;
break;
case InitializationSequence::FK_ConstructorOverloadFailed:
case InitializationSequence::FK_UserConversionOverloadFailed:
break;
}
OverloadCandidateSet &candidates = sequence.getFailedCandidateSet();
unsigned msg = 0;
OverloadCandidateDisplayKind howManyCandidates = OCD_AllCandidates;
switch (sequence.getFailedOverloadResult()) {
case OR_Success: llvm_unreachable("successful failed overload");
case OR_No_Viable_Function:
if (candidates.empty())
msg = diag::err_ovl_no_conversion_in_cast;
else
msg = diag::err_ovl_no_viable_conversion_in_cast;
howManyCandidates = OCD_AllCandidates;
break;
case OR_Ambiguous:
msg = diag::err_ovl_ambiguous_conversion_in_cast;
howManyCandidates = OCD_AmbiguousCandidates;
break;
case OR_Deleted: {
OverloadCandidateSet::iterator Best;
[[maybe_unused]] OverloadingResult Res =
candidates.BestViableFunction(S, range.getBegin(), Best);
assert(Res == OR_Deleted && "Inconsistent overload resolution");
StringLiteral *Msg = Best->Function->getDeletedMessage();
candidates.NoteCandidates(
PartialDiagnosticAt(range.getBegin(),
S.PDiag(diag::err_ovl_deleted_conversion_in_cast)
<< CT << srcType << destType << (Msg != nullptr)
<< (Msg ? Msg->getString() : StringRef())
<< range << src->getSourceRange()),
S, OCD_ViableCandidates, src);
return true;
}
}
candidates.NoteCandidates(
PartialDiagnosticAt(range.getBegin(),
S.PDiag(msg) << CT << srcType << destType << range
<< src->getSourceRange()),
S, howManyCandidates, src);
return true;
}
/// Diagnose a failed cast.
static void diagnoseBadCast(Sema &S, unsigned msg, CastType castType,
SourceRange opRange, Expr *src, QualType destType,
bool listInitialization) {
if (msg == diag::err_bad_cxx_cast_generic &&
tryDiagnoseOverloadedCast(S, castType, opRange, src, destType,
listInitialization))
return;
S.Diag(opRange.getBegin(), msg) << castType
<< src->getType() << destType << opRange << src->getSourceRange();
// Detect if both types are (ptr to) class, and note any incompleteness.
int DifferentPtrness = 0;
QualType From = destType;
if (auto Ptr = From->getAs<PointerType>()) {
From = Ptr->getPointeeType();
DifferentPtrness++;
}
QualType To = src->getType();
if (auto Ptr = To->getAs<PointerType>()) {
To = Ptr->getPointeeType();
DifferentPtrness--;
}
if (!DifferentPtrness) {
auto RecFrom = From->getAs<RecordType>();
auto RecTo = To->getAs<RecordType>();
if (RecFrom && RecTo) {
auto DeclFrom = RecFrom->getAsCXXRecordDecl();
if (!DeclFrom->isCompleteDefinition())
S.Diag(DeclFrom->getLocation(), diag::note_type_incomplete) << DeclFrom;
auto DeclTo = RecTo->getAsCXXRecordDecl();
if (!DeclTo->isCompleteDefinition())
S.Diag(DeclTo->getLocation(), diag::note_type_incomplete) << DeclTo;
}
}
}
namespace {
/// The kind of unwrapping we did when determining whether a conversion casts
/// away constness.
enum CastAwayConstnessKind {
/// The conversion does not cast away constness.
CACK_None = 0,
/// We unwrapped similar types.
CACK_Similar = 1,
/// We unwrapped dissimilar types with similar representations (eg, a pointer
/// versus an Objective-C object pointer).
CACK_SimilarKind = 2,
/// We unwrapped representationally-unrelated types, such as a pointer versus
/// a pointer-to-member.
CACK_Incoherent = 3,
};
}
/// Unwrap one level of types for CastsAwayConstness.
///
/// Like Sema::UnwrapSimilarTypes, this removes one level of indirection from
/// both types, provided that they're both pointer-like or array-like. Unlike
/// the Sema function, doesn't care if the unwrapped pieces are related.
///
/// This function may remove additional levels as necessary for correctness:
/// the resulting T1 is unwrapped sufficiently that it is never an array type,
/// so that its qualifiers can be directly compared to those of T2 (which will
/// have the combined set of qualifiers from all indermediate levels of T2),
/// as (effectively) required by [expr.const.cast]p7 replacing T1's qualifiers
/// with those from T2.
static CastAwayConstnessKind
unwrapCastAwayConstnessLevel(ASTContext &Context, QualType &T1, QualType &T2) {
enum { None, Ptr, MemPtr, BlockPtr, Array };
auto Classify = [](QualType T) {
if (T->isAnyPointerType()) return Ptr;
if (T->isMemberPointerType()) return MemPtr;
if (T->isBlockPointerType()) return BlockPtr;
// We somewhat-arbitrarily don't look through VLA types here. This is at
// least consistent with the behavior of UnwrapSimilarTypes.
if (T->isConstantArrayType() || T->isIncompleteArrayType()) return Array;
return None;
};
auto Unwrap = [&](QualType T) {
if (auto *AT = Context.getAsArrayType(T))
return AT->getElementType();
return T->getPointeeType();
};
CastAwayConstnessKind Kind;
if (T2->isReferenceType()) {
// Special case: if the destination type is a reference type, unwrap it as
// the first level. (The source will have been an lvalue expression in this
// case, so there is no corresponding "reference to" in T1 to remove.) This
// simulates removing a "pointer to" from both sides.
T2 = T2->getPointeeType();
Kind = CastAwayConstnessKind::CACK_Similar;
} else if (Context.UnwrapSimilarTypes(T1, T2)) {
Kind = CastAwayConstnessKind::CACK_Similar;
} else {
// Try unwrapping mismatching levels.
int T1Class = Classify(T1);
if (T1Class == None)
return CastAwayConstnessKind::CACK_None;
int T2Class = Classify(T2);
if (T2Class == None)
return CastAwayConstnessKind::CACK_None;
T1 = Unwrap(T1);
T2 = Unwrap(T2);
Kind = T1Class == T2Class ? CastAwayConstnessKind::CACK_SimilarKind
: CastAwayConstnessKind::CACK_Incoherent;
}
// We've unwrapped at least one level. If the resulting T1 is a (possibly
// multidimensional) array type, any qualifier on any matching layer of
// T2 is considered to correspond to T1. Decompose down to the element
// type of T1 so that we can compare properly.
while (true) {
Context.UnwrapSimilarArrayTypes(T1, T2);
if (Classify(T1) != Array)
break;
auto T2Class = Classify(T2);
if (T2Class == None)
break;
if (T2Class != Array)
Kind = CastAwayConstnessKind::CACK_Incoherent;
else if (Kind != CastAwayConstnessKind::CACK_Incoherent)
Kind = CastAwayConstnessKind::CACK_SimilarKind;
T1 = Unwrap(T1);
T2 = Unwrap(T2).withCVRQualifiers(T2.getCVRQualifiers());
}
return Kind;
}
/// Check if the pointer conversion from SrcType to DestType casts away
/// constness as defined in C++ [expr.const.cast]. This is used by the cast
/// checkers. Both arguments must denote pointer (possibly to member) types.
///
/// \param CheckCVR Whether to check for const/volatile/restrict qualifiers.
/// \param CheckObjCLifetime Whether to check Objective-C lifetime qualifiers.
static CastAwayConstnessKind
CastsAwayConstness(Sema &Self, QualType SrcType, QualType DestType,
bool CheckCVR, bool CheckObjCLifetime,
QualType *TheOffendingSrcType = nullptr,
QualType *TheOffendingDestType = nullptr,
Qualifiers *CastAwayQualifiers = nullptr) {
// If the only checking we care about is for Objective-C lifetime qualifiers,
// and we're not in ObjC mode, there's nothing to check.
if (!CheckCVR && CheckObjCLifetime && !Self.Context.getLangOpts().ObjC)
return CastAwayConstnessKind::CACK_None;
if (!DestType->isReferenceType()) {
assert((SrcType->isAnyPointerType() || SrcType->isMemberPointerType() ||
SrcType->isBlockPointerType()) &&
"Source type is not pointer or pointer to member.");
assert((DestType->isAnyPointerType() || DestType->isMemberPointerType() ||
DestType->isBlockPointerType()) &&
"Destination type is not pointer or pointer to member.");
}
QualType UnwrappedSrcType = Self.Context.getCanonicalType(SrcType),
UnwrappedDestType = Self.Context.getCanonicalType(DestType);
// Find the qualifiers. We only care about cvr-qualifiers for the
// purpose of this check, because other qualifiers (address spaces,
// Objective-C GC, etc.) are part of the type's identity.
QualType PrevUnwrappedSrcType = UnwrappedSrcType;
QualType PrevUnwrappedDestType = UnwrappedDestType;
auto WorstKind = CastAwayConstnessKind::CACK_Similar;
bool AllConstSoFar = true;
while (auto Kind = unwrapCastAwayConstnessLevel(
Self.Context, UnwrappedSrcType, UnwrappedDestType)) {
// Track the worst kind of unwrap we needed to do before we found a
// problem.
if (Kind > WorstKind)
WorstKind = Kind;
// Determine the relevant qualifiers at this level.
Qualifiers SrcQuals, DestQuals;
Self.Context.getUnqualifiedArrayType(UnwrappedSrcType, SrcQuals);
Self.Context.getUnqualifiedArrayType(UnwrappedDestType, DestQuals);
// We do not meaningfully track object const-ness of Objective-C object
// types. Remove const from the source type if either the source or
// the destination is an Objective-C object type.
if (UnwrappedSrcType->isObjCObjectType() ||
UnwrappedDestType->isObjCObjectType())
SrcQuals.removeConst();
if (CheckCVR) {
Qualifiers SrcCvrQuals =
Qualifiers::fromCVRMask(SrcQuals.getCVRQualifiers());
Qualifiers DestCvrQuals =
Qualifiers::fromCVRMask(DestQuals.getCVRQualifiers());
if (SrcCvrQuals != DestCvrQuals) {
if (CastAwayQualifiers)
*CastAwayQualifiers = SrcCvrQuals - DestCvrQuals;
// If we removed a cvr-qualifier, this is casting away 'constness'.
if (!DestCvrQuals.compatiblyIncludes(SrcCvrQuals,
Self.getASTContext())) {
if (TheOffendingSrcType)
*TheOffendingSrcType = PrevUnwrappedSrcType;
if (TheOffendingDestType)
*TheOffendingDestType = PrevUnwrappedDestType;
return WorstKind;
}
// If any prior level was not 'const', this is also casting away
// 'constness'. We noted the outermost type missing a 'const' already.
if (!AllConstSoFar)
return WorstKind;
}
}
if (CheckObjCLifetime &&
!DestQuals.compatiblyIncludesObjCLifetime(SrcQuals))
return WorstKind;
// If we found our first non-const-qualified type, this may be the place
// where things start to go wrong.
if (AllConstSoFar && !DestQuals.hasConst()) {
AllConstSoFar = false;
if (TheOffendingSrcType)
*TheOffendingSrcType = PrevUnwrappedSrcType;
if (TheOffendingDestType)
*TheOffendingDestType = PrevUnwrappedDestType;
}
PrevUnwrappedSrcType = UnwrappedSrcType;
PrevUnwrappedDestType = UnwrappedDestType;
}
return CastAwayConstnessKind::CACK_None;
}
static TryCastResult getCastAwayConstnessCastKind(CastAwayConstnessKind CACK,
unsigned &DiagID) {
switch (CACK) {
case CastAwayConstnessKind::CACK_None:
llvm_unreachable("did not cast away constness");
case CastAwayConstnessKind::CACK_Similar:
// FIXME: Accept these as an extension too?
case CastAwayConstnessKind::CACK_SimilarKind:
DiagID = diag::err_bad_cxx_cast_qualifiers_away;
return TC_Failed;
case CastAwayConstnessKind::CACK_Incoherent:
DiagID = diag::ext_bad_cxx_cast_qualifiers_away_incoherent;
return TC_Extension;
}
llvm_unreachable("unexpected cast away constness kind");
}
/// 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 CastOperation::CheckDynamicCast() {
CheckNoDerefRAII NoderefCheck(*this);
if (ValueKind == VK_PRValue)
SrcExpr = Self.DefaultFunctionArrayLvalueConversion(SrcExpr.get());
else if (isPlaceholder())
SrcExpr = Self.CheckPlaceholderExpr(SrcExpr.get());
if (SrcExpr.isInvalid()) // if conversion failed, don't report another error
return;
QualType OrigSrcType = SrcExpr.get()->getType();
QualType DestType = Self.Context.getCanonicalType(this->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 = nullptr;
if (DestPointer) {
DestPointee = DestPointer->getPointeeType();
} else if ((DestReference = DestType->getAs<ReferenceType>())) {
DestPointee = DestReference->getPointeeType();
} else {
Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_ref_or_ptr)
<< this->DestType << DestRange;
SrcExpr = ExprError();
return;
}
const RecordType *DestRecord = DestPointee->getAs<RecordType>();
if (DestPointee->isVoidType()) {
assert(DestPointer && "Reference to void is not possible");
} else if (DestRecord) {
if (Self.RequireCompleteType(OpRange.getBegin(), DestPointee,
diag::err_bad_cast_incomplete,
DestRange)) {
SrcExpr = ExprError();
return;
}
} else {
Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_class)
<< DestPointee.getUnqualifiedType() << DestRange;
SrcExpr = ExprError();
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 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 << this->DestType << SrcExpr.get()->getSourceRange();
SrcExpr = ExprError();
return;
}
} else if (DestReference->isLValueReferenceType()) {
if (!SrcExpr.get()->isLValue()) {
Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_rvalue)
<< CT_Dynamic << OrigSrcType << this->DestType << OpRange;
}
SrcPointee = SrcType;
} else {
// If we're dynamic_casting from a prvalue to an rvalue reference, we need
// to materialize the prvalue before we bind the reference to it.
if (SrcExpr.get()->isPRValue())
SrcExpr = Self.CreateMaterializeTemporaryExpr(
SrcType, SrcExpr.get(), /*IsLValueReference*/ false);
SrcPointee = SrcType;
}
const RecordType *SrcRecord = SrcPointee->getAs<RecordType>();
if (SrcRecord) {
if (Self.RequireCompleteType(OpRange.getBegin(), SrcPointee,
diag::err_bad_cast_incomplete,
SrcExpr.get())) {
SrcExpr = ExprError();
return;
}
} else {
Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_class)
<< SrcPointee.getUnqualifiedType() << SrcExpr.get()->getSourceRange();
SrcExpr = ExprError();
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.getASTContext())) {
Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_qualifiers_away)
<< CT_Dynamic << OrigSrcType << this->DestType << OpRange;
SrcExpr = ExprError();
return;
}
// C++ 5.2.7p3: If the type of v is the same as the required result type,
// [except for cv].
if (DestRecord == SrcRecord) {
Kind = CK_NoOp;
return;
}
// C++ 5.2.7p5
// Upcasts are resolved statically.
if (DestRecord &&
Self.IsDerivedFrom(OpRange.getBegin(), SrcPointee, DestPointee)) {
if (Self.CheckDerivedToBaseConversion(SrcPointee, DestPointee,
OpRange.getBegin(), OpRange,
&BasePath)) {
SrcExpr = ExprError();
return;
}
Kind = CK_DerivedToBase;
return;
}
// C++ 5.2.7p6: Otherwise, v shall be [polymorphic].
const RecordDecl *SrcDecl = SrcRecord->getDecl()->getDefinition();
assert(SrcDecl && "Definition missing");
if (!cast<CXXRecordDecl>(SrcDecl)->isPolymorphic()) {
Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_polymorphic)
<< SrcPointee.getUnqualifiedType() << SrcExpr.get()->getSourceRange();
SrcExpr = ExprError();
}
// dynamic_cast is not available with -fno-rtti.
// As an exception, dynamic_cast to void* is available because it doesn't
// use RTTI.
if (!Self.getLangOpts().RTTI && !DestPointee->isVoidType()) {
Self.Diag(OpRange.getBegin(), diag::err_no_dynamic_cast_with_fno_rtti);
SrcExpr = ExprError();
return;
}
// Warns when dynamic_cast is used with RTTI data disabled.
if (!Self.getLangOpts().RTTIData) {
bool MicrosoftABI =
Self.getASTContext().getTargetInfo().getCXXABI().isMicrosoft();
bool isClangCL = Self.getDiagnostics().getDiagnosticOptions().getFormat() ==
DiagnosticOptions::MSVC;
if (MicrosoftABI || !DestPointee->isVoidType())
Self.Diag(OpRange.getBegin(),
diag::warn_no_dynamic_cast_with_rtti_disabled)
<< isClangCL;
}
// For a dynamic_cast to a final type, IR generation might emit a reference
// to the vtable.
if (DestRecord) {
auto *DestDecl = DestRecord->getAsCXXRecordDecl();
if (DestDecl->isEffectivelyFinal())
Self.MarkVTableUsed(OpRange.getBegin(), DestDecl);
}
// Done. Everything else is run-time checks.
Kind = 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 CastOperation::CheckConstCast() {
CheckNoDerefRAII NoderefCheck(*this);
if (ValueKind == VK_PRValue)
SrcExpr = Self.DefaultFunctionArrayLvalueConversion(SrcExpr.get());
else if (isPlaceholder())
SrcExpr = Self.CheckPlaceholderExpr(SrcExpr.get());
if (SrcExpr.isInvalid()) // if conversion failed, don't report another error
return;
unsigned msg = diag::err_bad_cxx_cast_generic;
auto TCR = TryConstCast(Self, SrcExpr, DestType, /*CStyle*/ false, msg);
if (TCR != TC_Success && msg != 0) {
Self.Diag(OpRange.getBegin(), msg) << CT_Const
<< SrcExpr.get()->getType() << DestType << OpRange;