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//===--- CGClass.cpp - Emit LLVM Code for C++ classes -----------*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This contains code dealing with C++ code generation of classes
#include "CGBlocks.h"
#include "CGCXXABI.h"
#include "CGDebugInfo.h"
#include "CGRecordLayout.h"
#include "CodeGenFunction.h"
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/EvaluatedExprVisitor.h"
#include "clang/AST/RecordLayout.h"
#include "clang/AST/StmtCXX.h"
#include "clang/Basic/TargetBuiltins.h"
#include "clang/CodeGen/CGFunctionInfo.h"
#include "clang/Frontend/CodeGenOptions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Metadata.h"
#include "llvm/Transforms/Utils/SanitizerStats.h"
using namespace clang;
using namespace CodeGen;
/// Return the best known alignment for an unknown pointer to a
/// particular class.
CharUnits CodeGenModule::getClassPointerAlignment(const CXXRecordDecl *RD) {
if (!RD->isCompleteDefinition())
return CharUnits::One(); // Hopefully won't be used anywhere.
auto &layout = getContext().getASTRecordLayout(RD);
// If the class is final, then we know that the pointer points to an
// object of that type and can use the full alignment.
if (RD->hasAttr<FinalAttr>()) {
return layout.getAlignment();
// Otherwise, we have to assume it could be a subclass.
} else {
return layout.getNonVirtualAlignment();
/// Return the best known alignment for a pointer to a virtual base,
/// given the alignment of a pointer to the derived class.
CharUnits CodeGenModule::getVBaseAlignment(CharUnits actualDerivedAlign,
const CXXRecordDecl *derivedClass,
const CXXRecordDecl *vbaseClass) {
// The basic idea here is that an underaligned derived pointer might
// indicate an underaligned base pointer.
auto &baseLayout = getContext().getASTRecordLayout(vbaseClass);
CharUnits expectedVBaseAlign = baseLayout.getNonVirtualAlignment();
return getDynamicOffsetAlignment(actualDerivedAlign, derivedClass,
CodeGenModule::getDynamicOffsetAlignment(CharUnits actualBaseAlign,
const CXXRecordDecl *baseDecl,
CharUnits expectedTargetAlign) {
// If the base is an incomplete type (which is, alas, possible with
// member pointers), be pessimistic.
if (!baseDecl->isCompleteDefinition())
return std::min(actualBaseAlign, expectedTargetAlign);
auto &baseLayout = getContext().getASTRecordLayout(baseDecl);
CharUnits expectedBaseAlign = baseLayout.getNonVirtualAlignment();
// If the class is properly aligned, assume the target offset is, too.
// This actually isn't necessarily the right thing to do --- if the
// class is a complete object, but it's only properly aligned for a
// base subobject, then the alignments of things relative to it are
// probably off as well. (Note that this requires the alignment of
// the target to be greater than the NV alignment of the derived
// class.)
// However, our approach to this kind of under-alignment can only
// ever be best effort; after all, we're never going to propagate
// alignments through variables or parameters. Note, in particular,
// that constructing a polymorphic type in an address that's less
// than pointer-aligned will generally trap in the constructor,
// unless we someday add some sort of attribute to change the
// assumed alignment of 'this'. So our goal here is pretty much
// just to allow the user to explicitly say that a pointer is
// under-aligned and then safely access its fields and vtables.
if (actualBaseAlign >= expectedBaseAlign) {
return expectedTargetAlign;
// Otherwise, we might be offset by an arbitrary multiple of the
// actual alignment. The correct adjustment is to take the min of
// the two alignments.
return std::min(actualBaseAlign, expectedTargetAlign);
Address CodeGenFunction::LoadCXXThisAddress() {
assert(CurFuncDecl && "loading 'this' without a func declaration?");
// Lazily compute CXXThisAlignment.
if (CXXThisAlignment.isZero()) {
// Just use the best known alignment for the parent.
// TODO: if we're currently emitting a complete-object ctor/dtor,
// we can always use the complete-object alignment.
auto RD = cast<CXXMethodDecl>(CurFuncDecl)->getParent();
CXXThisAlignment = CGM.getClassPointerAlignment(RD);
return Address(LoadCXXThis(), CXXThisAlignment);
/// Emit the address of a field using a member data pointer.
/// \param E Only used for emergency diagnostics
CodeGenFunction::EmitCXXMemberDataPointerAddress(const Expr *E, Address base,
llvm::Value *memberPtr,
const MemberPointerType *memberPtrType,
LValueBaseInfo *BaseInfo,
TBAAAccessInfo *TBAAInfo) {
// Ask the ABI to compute the actual address.
llvm::Value *ptr =
CGM.getCXXABI().EmitMemberDataPointerAddress(*this, E, base,
memberPtr, memberPtrType);
QualType memberType = memberPtrType->getPointeeType();
CharUnits memberAlign = getNaturalTypeAlignment(memberType, BaseInfo,
memberAlign =
return Address(ptr, memberAlign);
CharUnits CodeGenModule::computeNonVirtualBaseClassOffset(
const CXXRecordDecl *DerivedClass, CastExpr::path_const_iterator Start,
CastExpr::path_const_iterator End) {
CharUnits Offset = CharUnits::Zero();
const ASTContext &Context = getContext();
const CXXRecordDecl *RD = DerivedClass;
for (CastExpr::path_const_iterator I = Start; I != End; ++I) {
const CXXBaseSpecifier *Base = *I;
assert(!Base->isVirtual() && "Should not see virtual bases here!");
// Get the layout.
const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
const CXXRecordDecl *BaseDecl =
// Add the offset.
Offset += Layout.getBaseClassOffset(BaseDecl);
RD = BaseDecl;
return Offset;
llvm::Constant *
CodeGenModule::GetNonVirtualBaseClassOffset(const CXXRecordDecl *ClassDecl,
CastExpr::path_const_iterator PathBegin,
CastExpr::path_const_iterator PathEnd) {
assert(PathBegin != PathEnd && "Base path should not be empty!");
CharUnits Offset =
computeNonVirtualBaseClassOffset(ClassDecl, PathBegin, PathEnd);
if (Offset.isZero())
return nullptr;
llvm::Type *PtrDiffTy =
return llvm::ConstantInt::get(PtrDiffTy, Offset.getQuantity());
/// Gets the address of a direct base class within a complete object.
/// This should only be used for (1) non-virtual bases or (2) virtual bases
/// when the type is known to be complete (e.g. in complete destructors).
/// The object pointed to by 'This' is assumed to be non-null.
CodeGenFunction::GetAddressOfDirectBaseInCompleteClass(Address This,
const CXXRecordDecl *Derived,
const CXXRecordDecl *Base,
bool BaseIsVirtual) {
// 'this' must be a pointer (in some address space) to Derived.
assert(This.getElementType() == ConvertType(Derived));
// Compute the offset of the virtual base.
CharUnits Offset;
const ASTRecordLayout &Layout = getContext().getASTRecordLayout(Derived);
if (BaseIsVirtual)
Offset = Layout.getVBaseClassOffset(Base);
Offset = Layout.getBaseClassOffset(Base);
// Shift and cast down to the base type.
// TODO: for complete types, this should be possible with a GEP.
Address V = This;
if (!Offset.isZero()) {
V = Builder.CreateElementBitCast(V, Int8Ty);
V = Builder.CreateConstInBoundsByteGEP(V, Offset);
V = Builder.CreateElementBitCast(V, ConvertType(Base));
return V;
static Address
ApplyNonVirtualAndVirtualOffset(CodeGenFunction &CGF, Address addr,
CharUnits nonVirtualOffset,
llvm::Value *virtualOffset,
const CXXRecordDecl *derivedClass,
const CXXRecordDecl *nearestVBase) {
// Assert that we have something to do.
assert(!nonVirtualOffset.isZero() || virtualOffset != nullptr);
// Compute the offset from the static and dynamic components.
llvm::Value *baseOffset;
if (!nonVirtualOffset.isZero()) {
baseOffset = llvm::ConstantInt::get(CGF.PtrDiffTy,
if (virtualOffset) {
baseOffset = CGF.Builder.CreateAdd(virtualOffset, baseOffset);
} else {
baseOffset = virtualOffset;
// Apply the base offset.
llvm::Value *ptr = addr.getPointer();
ptr = CGF.Builder.CreateBitCast(ptr, CGF.Int8PtrTy);
ptr = CGF.Builder.CreateInBoundsGEP(ptr, baseOffset, "add.ptr");
// If we have a virtual component, the alignment of the result will
// be relative only to the known alignment of that vbase.
CharUnits alignment;
if (virtualOffset) {
assert(nearestVBase && "virtual offset without vbase?");
alignment = CGF.CGM.getVBaseAlignment(addr.getAlignment(),
derivedClass, nearestVBase);
} else {
alignment = addr.getAlignment();
alignment = alignment.alignmentAtOffset(nonVirtualOffset);
return Address(ptr, alignment);
Address CodeGenFunction::GetAddressOfBaseClass(
Address Value, const CXXRecordDecl *Derived,
CastExpr::path_const_iterator PathBegin,
CastExpr::path_const_iterator PathEnd, bool NullCheckValue,
SourceLocation Loc) {
assert(PathBegin != PathEnd && "Base path should not be empty!");
CastExpr::path_const_iterator Start = PathBegin;
const CXXRecordDecl *VBase = nullptr;
// Sema has done some convenient canonicalization here: if the
// access path involved any virtual steps, the conversion path will
// *start* with a step down to the correct virtual base subobject,
// and hence will not require any further steps.
if ((*Start)->isVirtual()) {
VBase =
// Compute the static offset of the ultimate destination within its
// allocating subobject (the virtual base, if there is one, or else
// the "complete" object that we see).
CharUnits NonVirtualOffset = CGM.computeNonVirtualBaseClassOffset(
VBase ? VBase : Derived, Start, PathEnd);
// If there's a virtual step, we can sometimes "devirtualize" it.
// For now, that's limited to when the derived type is final.
// TODO: "devirtualize" this for accesses to known-complete objects.
if (VBase && Derived->hasAttr<FinalAttr>()) {
const ASTRecordLayout &layout = getContext().getASTRecordLayout(Derived);
CharUnits vBaseOffset = layout.getVBaseClassOffset(VBase);
NonVirtualOffset += vBaseOffset;
VBase = nullptr; // we no longer have a virtual step
// Get the base pointer type.
llvm::Type *BasePtrTy =
QualType DerivedTy = getContext().getRecordType(Derived);
CharUnits DerivedAlign = CGM.getClassPointerAlignment(Derived);
// If the static offset is zero and we don't have a virtual step,
// just do a bitcast; null checks are unnecessary.
if (NonVirtualOffset.isZero() && !VBase) {
if (sanitizePerformTypeCheck()) {
SanitizerSet SkippedChecks;
SkippedChecks.set(SanitizerKind::Null, !NullCheckValue);
EmitTypeCheck(TCK_Upcast, Loc, Value.getPointer(),
DerivedTy, DerivedAlign, SkippedChecks);
return Builder.CreateBitCast(Value, BasePtrTy);
llvm::BasicBlock *origBB = nullptr;
llvm::BasicBlock *endBB = nullptr;
// Skip over the offset (and the vtable load) if we're supposed to
// null-check the pointer.
if (NullCheckValue) {
origBB = Builder.GetInsertBlock();
llvm::BasicBlock *notNullBB = createBasicBlock("cast.notnull");
endBB = createBasicBlock("cast.end");
llvm::Value *isNull = Builder.CreateIsNull(Value.getPointer());
Builder.CreateCondBr(isNull, endBB, notNullBB);
if (sanitizePerformTypeCheck()) {
SanitizerSet SkippedChecks;
SkippedChecks.set(SanitizerKind::Null, true);
EmitTypeCheck(VBase ? TCK_UpcastToVirtualBase : TCK_Upcast, Loc,
Value.getPointer(), DerivedTy, DerivedAlign, SkippedChecks);
// Compute the virtual offset.
llvm::Value *VirtualOffset = nullptr;
if (VBase) {
VirtualOffset =
CGM.getCXXABI().GetVirtualBaseClassOffset(*this, Value, Derived, VBase);
// Apply both offsets.
Value = ApplyNonVirtualAndVirtualOffset(*this, Value, NonVirtualOffset,
VirtualOffset, Derived, VBase);
// Cast to the destination type.
Value = Builder.CreateBitCast(Value, BasePtrTy);
// Build a phi if we needed a null check.
if (NullCheckValue) {
llvm::BasicBlock *notNullBB = Builder.GetInsertBlock();
llvm::PHINode *PHI = Builder.CreatePHI(BasePtrTy, 2, "cast.result");
PHI->addIncoming(Value.getPointer(), notNullBB);
PHI->addIncoming(llvm::Constant::getNullValue(BasePtrTy), origBB);
Value = Address(PHI, Value.getAlignment());
return Value;
CodeGenFunction::GetAddressOfDerivedClass(Address BaseAddr,
const CXXRecordDecl *Derived,
CastExpr::path_const_iterator PathBegin,
CastExpr::path_const_iterator PathEnd,
bool NullCheckValue) {
assert(PathBegin != PathEnd && "Base path should not be empty!");
QualType DerivedTy =
llvm::Type *DerivedPtrTy = ConvertType(DerivedTy)->getPointerTo();
llvm::Value *NonVirtualOffset =
CGM.GetNonVirtualBaseClassOffset(Derived, PathBegin, PathEnd);
if (!NonVirtualOffset) {
// No offset, we can just cast back.
return Builder.CreateBitCast(BaseAddr, DerivedPtrTy);
llvm::BasicBlock *CastNull = nullptr;
llvm::BasicBlock *CastNotNull = nullptr;
llvm::BasicBlock *CastEnd = nullptr;
if (NullCheckValue) {
CastNull = createBasicBlock("cast.null");
CastNotNull = createBasicBlock("cast.notnull");
CastEnd = createBasicBlock("cast.end");
llvm::Value *IsNull = Builder.CreateIsNull(BaseAddr.getPointer());
Builder.CreateCondBr(IsNull, CastNull, CastNotNull);
// Apply the offset.
llvm::Value *Value = Builder.CreateBitCast(BaseAddr.getPointer(), Int8PtrTy);
Value = Builder.CreateGEP(Value, Builder.CreateNeg(NonVirtualOffset),
// Just cast.
Value = Builder.CreateBitCast(Value, DerivedPtrTy);
// Produce a PHI if we had a null-check.
if (NullCheckValue) {
llvm::PHINode *PHI = Builder.CreatePHI(Value->getType(), 2);
PHI->addIncoming(Value, CastNotNull);
PHI->addIncoming(llvm::Constant::getNullValue(Value->getType()), CastNull);
Value = PHI;
return Address(Value, CGM.getClassPointerAlignment(Derived));
llvm::Value *CodeGenFunction::GetVTTParameter(GlobalDecl GD,
bool ForVirtualBase,
bool Delegating) {
if (!CGM.getCXXABI().NeedsVTTParameter(GD)) {
// This constructor/destructor does not need a VTT parameter.
return nullptr;
const CXXRecordDecl *RD = cast<CXXMethodDecl>(CurCodeDecl)->getParent();
const CXXRecordDecl *Base = cast<CXXMethodDecl>(GD.getDecl())->getParent();
llvm::Value *VTT;
uint64_t SubVTTIndex;
if (Delegating) {
// If this is a delegating constructor call, just load the VTT.
return LoadCXXVTT();
} else if (RD == Base) {
// If the record matches the base, this is the complete ctor/dtor
// variant calling the base variant in a class with virtual bases.
assert(!CGM.getCXXABI().NeedsVTTParameter(CurGD) &&
"doing no-op VTT offset in base dtor/ctor?");
assert(!ForVirtualBase && "Can't have same class as virtual base!");
SubVTTIndex = 0;
} else {
const ASTRecordLayout &Layout = getContext().getASTRecordLayout(RD);
CharUnits BaseOffset = ForVirtualBase ?
Layout.getVBaseClassOffset(Base) :
SubVTTIndex =
CGM.getVTables().getSubVTTIndex(RD, BaseSubobject(Base, BaseOffset));
assert(SubVTTIndex != 0 && "Sub-VTT index must be greater than zero!");
if (CGM.getCXXABI().NeedsVTTParameter(CurGD)) {
// A VTT parameter was passed to the constructor, use it.
VTT = Builder.CreateConstInBoundsGEP1_64(VTT, SubVTTIndex);
} else {
// We're the complete constructor, so get the VTT by name.
VTT = CGM.getVTables().GetAddrOfVTT(RD);
VTT = Builder.CreateConstInBoundsGEP2_64(VTT, 0, SubVTTIndex);
return VTT;
namespace {
/// Call the destructor for a direct base class.
struct CallBaseDtor final : EHScopeStack::Cleanup {
const CXXRecordDecl *BaseClass;
bool BaseIsVirtual;
CallBaseDtor(const CXXRecordDecl *Base, bool BaseIsVirtual)
: BaseClass(Base), BaseIsVirtual(BaseIsVirtual) {}
void Emit(CodeGenFunction &CGF, Flags flags) override {
const CXXRecordDecl *DerivedClass =
const CXXDestructorDecl *D = BaseClass->getDestructor();
Address Addr =
DerivedClass, BaseClass,
CGF.EmitCXXDestructorCall(D, Dtor_Base, BaseIsVirtual,
/*Delegating=*/false, Addr);
/// A visitor which checks whether an initializer uses 'this' in a
/// way which requires the vtable to be properly set.
struct DynamicThisUseChecker : ConstEvaluatedExprVisitor<DynamicThisUseChecker> {
typedef ConstEvaluatedExprVisitor<DynamicThisUseChecker> super;
bool UsesThis;
DynamicThisUseChecker(const ASTContext &C) : super(C), UsesThis(false) {}
// Black-list all explicit and implicit references to 'this'.
// Do we need to worry about external references to 'this' derived
// from arbitrary code? If so, then anything which runs arbitrary
// external code might potentially access the vtable.
void VisitCXXThisExpr(const CXXThisExpr *E) { UsesThis = true; }
} // end anonymous namespace
static bool BaseInitializerUsesThis(ASTContext &C, const Expr *Init) {
DynamicThisUseChecker Checker(C);
return Checker.UsesThis;
static void EmitBaseInitializer(CodeGenFunction &CGF,
const CXXRecordDecl *ClassDecl,
CXXCtorInitializer *BaseInit,
CXXCtorType CtorType) {
assert(BaseInit->isBaseInitializer() &&
"Must have base initializer!");
Address ThisPtr = CGF.LoadCXXThisAddress();
const Type *BaseType = BaseInit->getBaseClass();
CXXRecordDecl *BaseClassDecl =
bool isBaseVirtual = BaseInit->isBaseVirtual();
// The base constructor doesn't construct virtual bases.
if (CtorType == Ctor_Base && isBaseVirtual)
// If the initializer for the base (other than the constructor
// itself) accesses 'this' in any way, we need to initialize the
// vtables.
if (BaseInitializerUsesThis(CGF.getContext(), BaseInit->getInit()))
// We can pretend to be a complete class because it only matters for
// virtual bases, and we only do virtual bases for complete ctors.
Address V =
CGF.GetAddressOfDirectBaseInCompleteClass(ThisPtr, ClassDecl,
AggValueSlot AggSlot =
AggValueSlot::forAddr(V, Qualifiers(),
CGF.EmitAggExpr(BaseInit->getInit(), AggSlot);
if (CGF.CGM.getLangOpts().Exceptions &&
CGF.EHStack.pushCleanup<CallBaseDtor>(EHCleanup, BaseClassDecl,
static bool isMemcpyEquivalentSpecialMember(const CXXMethodDecl *D) {
auto *CD = dyn_cast<CXXConstructorDecl>(D);
if (!(CD && CD->isCopyOrMoveConstructor()) &&
!D->isCopyAssignmentOperator() && !D->isMoveAssignmentOperator())
return false;
// We can emit a memcpy for a trivial copy or move constructor/assignment.
if (D->isTrivial() && !D->getParent()->mayInsertExtraPadding())
return true;
// We *must* emit a memcpy for a defaulted union copy or move op.
if (D->getParent()->isUnion() && D->isDefaulted())
return true;
return false;
static void EmitLValueForAnyFieldInitialization(CodeGenFunction &CGF,
CXXCtorInitializer *MemberInit,
LValue &LHS) {
FieldDecl *Field = MemberInit->getAnyMember();
if (MemberInit->isIndirectMemberInitializer()) {
// If we are initializing an anonymous union field, drill down to the field.
IndirectFieldDecl *IndirectField = MemberInit->getIndirectMember();
for (const auto *I : IndirectField->chain())
LHS = CGF.EmitLValueForFieldInitialization(LHS, cast<FieldDecl>(I));
} else {
LHS = CGF.EmitLValueForFieldInitialization(LHS, Field);
static void EmitMemberInitializer(CodeGenFunction &CGF,
const CXXRecordDecl *ClassDecl,
CXXCtorInitializer *MemberInit,
const CXXConstructorDecl *Constructor,
FunctionArgList &Args) {
ApplyDebugLocation Loc(CGF, MemberInit->getSourceLocation());
assert(MemberInit->isAnyMemberInitializer() &&
"Must have member initializer!");
assert(MemberInit->getInit() && "Must have initializer!");
// non-static data member initializers.
FieldDecl *Field = MemberInit->getAnyMember();
QualType FieldType = Field->getType();
llvm::Value *ThisPtr = CGF.LoadCXXThis();
QualType RecordTy = CGF.getContext().getTypeDeclType(ClassDecl);
LValue LHS = CGF.MakeNaturalAlignAddrLValue(ThisPtr, RecordTy);
EmitLValueForAnyFieldInitialization(CGF, MemberInit, LHS);
// Special case: if we are in a copy or move constructor, and we are copying
// an array of PODs or classes with trivial copy constructors, ignore the
// AST and perform the copy we know is equivalent.
// FIXME: This is hacky at best... if we had a bit more explicit information
// in the AST, we could generalize it more easily.
const ConstantArrayType *Array
= CGF.getContext().getAsConstantArrayType(FieldType);
if (Array && Constructor->isDefaulted() &&
Constructor->isCopyOrMoveConstructor()) {
QualType BaseElementTy = CGF.getContext().getBaseElementType(Array);
CXXConstructExpr *CE = dyn_cast<CXXConstructExpr>(MemberInit->getInit());
if (BaseElementTy.isPODType(CGF.getContext()) ||
(CE && isMemcpyEquivalentSpecialMember(CE->getConstructor()))) {
unsigned SrcArgIndex =
CGF.CGM.getCXXABI().getSrcArgforCopyCtor(Constructor, Args);
llvm::Value *SrcPtr
= CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(Args[SrcArgIndex]));
LValue ThisRHSLV = CGF.MakeNaturalAlignAddrLValue(SrcPtr, RecordTy);
LValue Src = CGF.EmitLValueForFieldInitialization(ThisRHSLV, Field);
// Copy the aggregate.
CGF.EmitAggregateCopy(LHS.getAddress(), Src.getAddress(), FieldType,
// Ensure that we destroy the objects if an exception is thrown later in
// the constructor.
QualType::DestructionKind dtorKind = FieldType.isDestructedType();
if (CGF.needsEHCleanup(dtorKind))
CGF.pushEHDestroy(dtorKind, LHS.getAddress(), FieldType);
CGF.EmitInitializerForField(Field, LHS, MemberInit->getInit());
void CodeGenFunction::EmitInitializerForField(FieldDecl *Field, LValue LHS,
Expr *Init) {
QualType FieldType = Field->getType();
switch (getEvaluationKind(FieldType)) {
case TEK_Scalar:
if (LHS.isSimple()) {
EmitExprAsInit(Init, Field, LHS, false);
} else {
RValue RHS = RValue::get(EmitScalarExpr(Init));
EmitStoreThroughLValue(RHS, LHS);
case TEK_Complex:
EmitComplexExprIntoLValue(Init, LHS, /*isInit*/ true);
case TEK_Aggregate: {
AggValueSlot Slot =
EmitAggExpr(Init, Slot);
// Ensure that we destroy this object if an exception is thrown
// later in the constructor.
QualType::DestructionKind dtorKind = FieldType.isDestructedType();
if (needsEHCleanup(dtorKind))
pushEHDestroy(dtorKind, LHS.getAddress(), FieldType);
/// Checks whether the given constructor is a valid subject for the
/// complete-to-base constructor delegation optimization, i.e.
/// emitting the complete constructor as a simple call to the base
/// constructor.
bool CodeGenFunction::IsConstructorDelegationValid(
const CXXConstructorDecl *Ctor) {
// Currently we disable the optimization for classes with virtual
// bases because (1) the addresses of parameter variables need to be
// consistent across all initializers but (2) the delegate function
// call necessarily creates a second copy of the parameter variable.
// The limiting example (purely theoretical AFAIK):
// struct A { A(int &c) { c++; } };
// struct B : virtual A {
// B(int count) : A(count) { printf("%d\n", count); }
// };
// ...although even this example could in principle be emitted as a
// delegation since the address of the parameter doesn't escape.
if (Ctor->getParent()->getNumVBases()) {
// TODO: white-list trivial vbase initializers. This case wouldn't
// be subject to the restrictions below.
// TODO: white-list cases where:
// - there are no non-reference parameters to the constructor
// - the initializers don't access any non-reference parameters
// - the initializers don't take the address of non-reference
// parameters
// - etc.
// If we ever add any of the above cases, remember that:
// - function-try-blocks will always blacklist this optimization
// - we need to perform the constructor prologue and cleanup in
// EmitConstructorBody.
return false;
// We also disable the optimization for variadic functions because
// it's impossible to "re-pass" varargs.
if (Ctor->getType()->getAs<FunctionProtoType>()->isVariadic())
return false;
// FIXME: Decide if we can do a delegation of a delegating constructor.
if (Ctor->isDelegatingConstructor())
return false;
return true;
// Emit code in ctor (Prologue==true) or dtor (Prologue==false)
// to poison the extra field paddings inserted under
// -fsanitize-address-field-padding=1|2.
void CodeGenFunction::EmitAsanPrologueOrEpilogue(bool Prologue) {
ASTContext &Context = getContext();
const CXXRecordDecl *ClassDecl =
Prologue ? cast<CXXConstructorDecl>(CurGD.getDecl())->getParent()
: cast<CXXDestructorDecl>(CurGD.getDecl())->getParent();
if (!ClassDecl->mayInsertExtraPadding()) return;
struct SizeAndOffset {
uint64_t Size;
uint64_t Offset;
unsigned PtrSize = CGM.getDataLayout().getPointerSizeInBits();
const ASTRecordLayout &Info = Context.getASTRecordLayout(ClassDecl);
// Populate sizes and offsets of fields.
SmallVector<SizeAndOffset, 16> SSV(Info.getFieldCount());
for (unsigned i = 0, e = Info.getFieldCount(); i != e; ++i)
SSV[i].Offset =
size_t NumFields = 0;
for (const auto *Field : ClassDecl->fields()) {
const FieldDecl *D = Field;
std::pair<CharUnits, CharUnits> FieldInfo =
CharUnits FieldSize = FieldInfo.first;
assert(NumFields < SSV.size());
SSV[NumFields].Size = D->isBitField() ? 0 : FieldSize.getQuantity();
assert(NumFields == SSV.size());
if (SSV.size() <= 1) return;
// We will insert calls to __asan_* run-time functions.
// LLVM AddressSanitizer pass may decide to inline them later.
llvm::Type *Args[2] = {IntPtrTy, IntPtrTy};
llvm::FunctionType *FTy =
llvm::FunctionType::get(CGM.VoidTy, Args, false);
llvm::Constant *F = CGM.CreateRuntimeFunction(
FTy, Prologue ? "__asan_poison_intra_object_redzone"
: "__asan_unpoison_intra_object_redzone");
llvm::Value *ThisPtr = LoadCXXThis();
ThisPtr = Builder.CreatePtrToInt(ThisPtr, IntPtrTy);
uint64_t TypeSize = Info.getNonVirtualSize().getQuantity();
// For each field check if it has sufficient padding,
// if so (un)poison it with a call.
for (size_t i = 0; i < SSV.size(); i++) {
uint64_t AsanAlignment = 8;
uint64_t NextField = i == SSV.size() - 1 ? TypeSize : SSV[i + 1].Offset;
uint64_t PoisonSize = NextField - SSV[i].Offset - SSV[i].Size;
uint64_t EndOffset = SSV[i].Offset + SSV[i].Size;
if (PoisonSize < AsanAlignment || !SSV[i].Size ||
(NextField % AsanAlignment) != 0)
F, {Builder.CreateAdd(ThisPtr, Builder.getIntN(PtrSize, EndOffset)),
Builder.getIntN(PtrSize, PoisonSize)});
/// EmitConstructorBody - Emits the body of the current constructor.
void CodeGenFunction::EmitConstructorBody(FunctionArgList &Args) {
const CXXConstructorDecl *Ctor = cast<CXXConstructorDecl>(CurGD.getDecl());
CXXCtorType CtorType = CurGD.getCtorType();
assert((CGM.getTarget().getCXXABI().hasConstructorVariants() ||
CtorType == Ctor_Complete) &&
"can only generate complete ctor for this ABI");
// Before we go any further, try the complete->base constructor
// delegation optimization.
if (CtorType == Ctor_Complete && IsConstructorDelegationValid(Ctor) &&
CGM.getTarget().getCXXABI().hasConstructorVariants()) {
EmitDelegateCXXConstructorCall(Ctor, Ctor_Base, Args, Ctor->getLocEnd());
const FunctionDecl *Definition = nullptr;
Stmt *Body = Ctor->getBody(Definition);
assert(Definition == Ctor && "emitting wrong constructor body");
// Enter the function-try-block before the constructor prologue if
// applicable.
bool IsTryBody = (Body && isa<CXXTryStmt>(Body));
if (IsTryBody)
EnterCXXTryStmt(*cast<CXXTryStmt>(Body), true);
RunCleanupsScope RunCleanups(*this);
// TODO: in restricted cases, we can emit the vbase initializers of
// a complete ctor and then delegate to the base ctor.
// Emit the constructor prologue, i.e. the base and member
// initializers.
EmitCtorPrologue(Ctor, CtorType, Args);
// Emit the body of the statement.
if (IsTryBody)
else if (Body)
// Emit any cleanup blocks associated with the member or base
// initializers, which includes (along the exceptional path) the
// destructors for those members and bases that were fully
// constructed.
if (IsTryBody)
ExitCXXTryStmt(*cast<CXXTryStmt>(Body), true);
namespace {
/// RAII object to indicate that codegen is copying the value representation
/// instead of the object representation. Useful when copying a struct or
/// class which has uninitialized members and we're only performing
/// lvalue-to-rvalue conversion on the object but not its members.
class CopyingValueRepresentation {
explicit CopyingValueRepresentation(CodeGenFunction &CGF)
: CGF(CGF), OldSanOpts(CGF.SanOpts) {
CGF.SanOpts.set(SanitizerKind::Bool, false);
CGF.SanOpts.set(SanitizerKind::Enum, false);
~CopyingValueRepresentation() {
CGF.SanOpts = OldSanOpts;
CodeGenFunction &CGF;
SanitizerSet OldSanOpts;
} // end anonymous namespace
namespace {
class FieldMemcpyizer {
FieldMemcpyizer(CodeGenFunction &CGF, const CXXRecordDecl *ClassDecl,
const VarDecl *SrcRec)
: CGF(CGF), ClassDecl(ClassDecl), SrcRec(SrcRec),
FirstField(nullptr), LastField(nullptr), FirstFieldOffset(0),
LastFieldOffset(0), LastAddedFieldIndex(0) {}
bool isMemcpyableField(FieldDecl *F) const {
// Never memcpy fields when we are adding poisoned paddings.
if (CGF.getContext().getLangOpts().SanitizeAddressFieldPadding)
return false;
Qualifiers Qual = F->getType().getQualifiers();
if (Qual.hasVolatile() || Qual.hasObjCLifetime())
return false;
return true;
void addMemcpyableField(FieldDecl *F) {
if (!FirstField)
CharUnits getMemcpySize(uint64_t FirstByteOffset) const {
unsigned LastFieldSize =
LastField->isBitField() ?
LastField->getBitWidthValue(CGF.getContext()) :
uint64_t MemcpySizeBits =
LastFieldOffset + LastFieldSize - FirstByteOffset +
CGF.getContext().getCharWidth() - 1;
CharUnits MemcpySize =
return MemcpySize;
void emitMemcpy() {
// Give the subclass a chance to bail out if it feels the memcpy isn't
// worth it (e.g. Hasn't aggregated enough data).
if (!FirstField) {
uint64_t FirstByteOffset;
if (FirstField->isBitField()) {
const CGRecordLayout &RL =
const CGBitFieldInfo &BFInfo = RL.getBitFieldInfo(FirstField);
// FirstFieldOffset is not appropriate for bitfields,
// we need to use the storage offset instead.
FirstByteOffset = CGF.getContext().toBits(BFInfo.StorageOffset);
} else {
FirstByteOffset = FirstFieldOffset;
CharUnits MemcpySize = getMemcpySize(FirstByteOffset);
QualType RecordTy = CGF.getContext().getTypeDeclType(ClassDecl);
Address ThisPtr = CGF.LoadCXXThisAddress();
LValue DestLV = CGF.MakeAddrLValue(ThisPtr, RecordTy);
LValue Dest = CGF.EmitLValueForFieldInitialization(DestLV, FirstField);
llvm::Value *SrcPtr = CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(SrcRec));
LValue SrcLV = CGF.MakeNaturalAlignAddrLValue(SrcPtr, RecordTy);
LValue Src = CGF.EmitLValueForFieldInitialization(SrcLV, FirstField);
emitMemcpyIR(Dest.isBitField() ? Dest.getBitFieldAddress() : Dest.getAddress(),
Src.isBitField() ? Src.getBitFieldAddress() : Src.getAddress(),
void reset() {
FirstField = nullptr;
CodeGenFunction &CGF;
const CXXRecordDecl *ClassDecl;
void emitMemcpyIR(Address DestPtr, Address SrcPtr, CharUnits Size) {
llvm::PointerType *DPT = DestPtr.getType();
llvm::Type *DBP =
llvm::Type::getInt8PtrTy(CGF.getLLVMContext(), DPT->getAddressSpace());
DestPtr = CGF.Builder.CreateBitCast(DestPtr, DBP);
llvm::PointerType *SPT = SrcPtr.getType();
llvm::Type *SBP =
llvm::Type::getInt8PtrTy(CGF.getLLVMContext(), SPT->getAddressSpace());
SrcPtr = CGF.Builder.CreateBitCast(SrcPtr, SBP);
CGF.Builder.CreateMemCpy(DestPtr, SrcPtr, Size.getQuantity());
void addInitialField(FieldDecl *F) {
FirstField = F;
LastField = F;
FirstFieldOffset = RecLayout.getFieldOffset(F->getFieldIndex());
LastFieldOffset = FirstFieldOffset;
LastAddedFieldIndex = F->getFieldIndex();
void addNextField(FieldDecl *F) {
// For the most part, the following invariant will hold:
// F->getFieldIndex() == LastAddedFieldIndex + 1
// The one exception is that Sema won't add a copy-initializer for an
// unnamed bitfield, which will show up here as a gap in the sequence.
assert(F->getFieldIndex() >= LastAddedFieldIndex + 1 &&
"Cannot aggregate fields out of order.");
LastAddedFieldIndex = F->getFieldIndex();
// The 'first' and 'last' fields are chosen by offset, rather than field
// index. This allows the code to support bitfields, as well as regular
// fields.
uint64_t FOffset = RecLayout.getFieldOffset(F->getFieldIndex());
if (FOffset < FirstFieldOffset) {
FirstField = F;
FirstFieldOffset = FOffset;
} else if (FOffset > LastFieldOffset) {
LastField = F;
LastFieldOffset = FOffset;
const VarDecl *SrcRec;
const ASTRecordLayout &RecLayout;
FieldDecl *FirstField;
FieldDecl *LastField;
uint64_t FirstFieldOffset, LastFieldOffset;
unsigned LastAddedFieldIndex;
class ConstructorMemcpyizer : public FieldMemcpyizer {
/// Get source argument for copy constructor. Returns null if not a copy
/// constructor.
static const VarDecl *getTrivialCopySource(CodeGenFunction &CGF,
const CXXConstructorDecl *CD,
FunctionArgList &Args) {
if (CD->isCopyOrMoveConstructor() && CD->isDefaulted())
return Args[CGF.CGM.getCXXABI().getSrcArgforCopyCtor(CD, Args)];
return nullptr;
// Returns true if a CXXCtorInitializer represents a member initialization
// that can be rolled into a memcpy.
bool isMemberInitMemcpyable(CXXCtorInitializer *MemberInit) const {
if (!MemcpyableCtor)
return false;
FieldDecl *Field = MemberInit->getMember();
assert(Field && "No field for member init.");
QualType FieldType = Field->getType();
CXXConstructExpr *CE = dyn_cast<CXXConstructExpr>(MemberInit->getInit());
// Bail out on non-memcpyable, not-trivially-copyable members.
if (!(CE && isMemcpyEquivalentSpecialMember(CE->getConstructor())) &&
!(FieldType.isTriviallyCopyableType(CGF.getContext()) ||
return false;
// Bail out on volatile fields.
if (!isMemcpyableField(Field))
return false;
// Otherwise we're good.
return true;
ConstructorMemcpyizer(CodeGenFunction &CGF, const CXXConstructorDecl *CD,
FunctionArgList &Args)
: FieldMemcpyizer(CGF, CD->getParent(), getTrivialCopySource(CGF, CD, Args)),
MemcpyableCtor(CD->isDefaulted() &&
CD->isCopyOrMoveConstructor() &&
CGF.getLangOpts().getGC() == LangOptions::NonGC),
Args(Args) { }
void addMemberInitializer(CXXCtorInitializer *MemberInit) {
if (isMemberInitMemcpyable(MemberInit)) {
} else {
EmitMemberInitializer(CGF, ConstructorDecl->getParent(), MemberInit,
ConstructorDecl, Args);
void emitAggregatedInits() {
if (AggregatedInits.size() <= 1) {
// This memcpy is too small to be worthwhile. Fall back on default
// codegen.
if (!AggregatedInits.empty()) {
CopyingValueRepresentation CVR(CGF);
EmitMemberInitializer(CGF, ConstructorDecl->getParent(),
AggregatedInits[0], ConstructorDecl, Args);
void pushEHDestructors() {
Address ThisPtr = CGF.LoadCXXThisAddress();
QualType RecordTy = CGF.getContext().getTypeDeclType(ClassDecl);
LValue LHS = CGF.MakeAddrLValue(ThisPtr, RecordTy);
for (unsigned i = 0; i < AggregatedInits.size(); ++i) {
CXXCtorInitializer *MemberInit = AggregatedInits[i];
QualType FieldType = MemberInit->getAnyMember()->getType();
QualType::DestructionKind dtorKind = FieldType.isDestructedType();
if (!CGF.needsEHCleanup(dtorKind))
LValue FieldLHS = LHS;
EmitLValueForAnyFieldInitialization(CGF, MemberInit, FieldLHS);
CGF.pushEHDestroy(dtorKind, FieldLHS.getAddress(), FieldType);
void finish() {
const CXXConstructorDecl *ConstructorDecl;
bool MemcpyableCtor;
FunctionArgList &Args;
SmallVector<CXXCtorInitializer*, 16> AggregatedInits;
class AssignmentMemcpyizer : public FieldMemcpyizer {
// Returns the memcpyable field copied by the given statement, if one
// exists. Otherwise returns null.
FieldDecl *getMemcpyableField(Stmt *S) {
if (!AssignmentsMemcpyable)
return nullptr;
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(S)) {
// Recognise trivial assignments.
if (BO->getOpcode() != BO_Assign)
return nullptr;
MemberExpr *ME = dyn_cast<MemberExpr>(BO->getLHS());
if (!ME)
return nullptr;
FieldDecl *Field = dyn_cast<FieldDecl>(ME->getMemberDecl());
if (!Field || !isMemcpyableField(Field))
return nullptr;
Stmt *RHS = BO->getRHS();
if (ImplicitCastExpr *EC = dyn_cast<ImplicitCastExpr>(RHS))
RHS = EC->getSubExpr();
if (!RHS)
return nullptr;
if (MemberExpr *ME2 = dyn_cast<MemberExpr>(RHS)) {
if (ME2->getMemberDecl() == Field)
return Field;
return nullptr;
} else if (CXXMemberCallExpr *MCE = dyn_cast<CXXMemberCallExpr>(S)) {
CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(MCE->getCalleeDecl());
if (!(MD && isMemcpyEquivalentSpecialMember(MD)))
return nullptr;
MemberExpr *IOA = dyn_cast<MemberExpr>(MCE->getImplicitObjectArgument());
if (!IOA)
return nullptr;
FieldDecl *Field = dyn_cast<FieldDecl>(IOA->getMemberDecl());
if (!Field || !isMemcpyableField(Field))
return nullptr;
MemberExpr *Arg0 = dyn_cast<MemberExpr>(MCE->getArg(0));
if (!Arg0 || Field != dyn_cast<FieldDecl>(Arg0->getMemberDecl()))
return nullptr;
return Field;
} else if (CallExpr *CE = dyn_cast<CallExpr>(S)) {
FunctionDecl *FD = dyn_cast<FunctionDecl>(CE->getCalleeDecl());
if (!FD || FD->getBuiltinID() != Builtin::BI__builtin_memcpy)
return nullptr;
Expr *DstPtr = CE->getArg(0);
if (ImplicitCastExpr *DC = dyn_cast<ImplicitCastExpr>(DstPtr))
DstPtr = DC->getSubExpr();
UnaryOperator *DUO = dyn_cast<UnaryOperator>(DstPtr);
if (!DUO || DUO->getOpcode() != UO_AddrOf)
return nullptr;
MemberExpr *ME = dyn_cast<MemberExpr>(DUO->getSubExpr());
if (!ME)
return nullptr;
FieldDecl *Field = dyn_cast<FieldDecl>(ME->getMemberDecl());
if (!Field || !isMemcpyableField(Field))
return nullptr;
Expr *SrcPtr = CE->getArg(1);
if (ImplicitCastExpr *SC = dyn_cast<ImplicitCastExpr>(SrcPtr))
SrcPtr = SC->getSubExpr();
UnaryOperator *SUO = dyn_cast<UnaryOperator>(SrcPtr);
if (!SUO || SUO->getOpcode() != UO_AddrOf)
return nullptr;
MemberExpr *ME2 = dyn_cast<MemberExpr>(SUO->getSubExpr());
if (!ME2 || Field != dyn_cast<FieldDecl>(ME2->getMemberDecl()))
return nullptr;
return Field;
return nullptr;
bool AssignmentsMemcpyable;
SmallVector<Stmt*, 16> AggregatedStmts;
AssignmentMemcpyizer(CodeGenFunction &CGF, const CXXMethodDecl *AD,
FunctionArgList &Args)
: FieldMemcpyizer(CGF, AD->getParent(), Args[Args.size() - 1]),
AssignmentsMemcpyable(CGF.getLangOpts().getGC() == LangOptions::NonGC) {
assert(Args.size() == 2);
void emitAssignment(Stmt *S) {
FieldDecl *F = getMemcpyableField(S);
if (F) {
} else {
void emitAggregatedStmts() {
if (AggregatedStmts.size() <= 1) {
if (!AggregatedStmts.empty()) {
CopyingValueRepresentation CVR(CGF);
void finish() {
} // end anonymous namespace
static bool isInitializerOfDynamicClass(const CXXCtorInitializer *BaseInit) {
const Type *BaseType = BaseInit->getBaseClass();
const auto *BaseClassDecl =
return BaseClassDecl->isDynamicClass();
/// EmitCtorPrologue - This routine generates necessary code to initialize
/// base classes and non-static data members belonging to this constructor.
void CodeGenFunction::EmitCtorPrologue(const CXXConstructorDecl *CD,
CXXCtorType CtorType,
FunctionArgList &Args) {
if (CD->isDelegatingConstructor())
return EmitDelegatingCXXConstructorCall(CD, Args);
const CXXRecordDecl *ClassDecl = CD->getParent();
CXXConstructorDecl::init_const_iterator B = CD->init_begin(),
E = CD->init_end();
llvm::BasicBlock *BaseCtorContinueBB = nullptr;
if (ClassDecl->getNumVBases() &&
!CGM.getTarget().getCXXABI().hasConstructorVariants()) {
// The ABIs that don't have constructor variants need to put a branch
// before the virtual base initialization code.
BaseCtorContinueBB =
CGM.getCXXABI().EmitCtorCompleteObjectHandler(*this, ClassDecl);
llvm::Value *const OldThis = CXXThisValue;
// Virtual base initializers first.
for (; B != E && (*B)->isBaseInitializer() && (*B)->isBaseVirtual(); B++) {
if (CGM.getCodeGenOpts().StrictVTablePointers &&
CGM.getCodeGenOpts().OptimizationLevel > 0 &&
CXXThisValue = Builder.CreateInvariantGroupBarrier(LoadCXXThis());
EmitBaseInitializer(*this, ClassDecl, *B, CtorType);
if (BaseCtorContinueBB) {
// Complete object handler should continue to the remaining initializers.
// Then, non-virtual base initializers.
for (; B != E && (*B)->isBaseInitializer(); B++) {
if (CGM.getCodeGenOpts().StrictVTablePointers &&
CGM.getCodeGenOpts().OptimizationLevel > 0 &&
CXXThisValue = Builder.CreateInvariantGroupBarrier(LoadCXXThis());
EmitBaseInitializer(*this, ClassDecl, *B, CtorType);
CXXThisValue = OldThis;
// And finally, initialize class members.
FieldConstructionScope FCS(*this, LoadCXXThisAddress());
ConstructorMemcpyizer CM(*this, CD, Args);
for (; B != E; B++) {
CXXCtorInitializer *Member = (*B);
assert(Member->isAnyMemberInitializer() &&
"Delegating initializer on non-delegating constructor");
static bool
FieldHasTrivialDestructorBody(ASTContext &Context, const FieldDecl *Field);
static bool
HasTrivialDestructorBody(ASTContext &Context,
const CXXRecordDecl *BaseClassDecl,
const CXXRecordDecl *MostDerivedClassDecl)
// If the destructor is trivial we don't have to check anything else.
if (BaseClassDecl->hasTrivialDestructor())
return true;
if (!BaseClassDecl->getDestructor()->hasTrivialBody())
return false;
// Check fields.
for (const auto *Field : BaseClassDecl->fields())
if (!FieldHasTrivialDestructorBody(Context, Field))
return false;
// Check non-virtual bases.
for (const auto &I : BaseClassDecl->bases()) {
if (I.isVirtual())
const CXXRecordDecl *NonVirtualBase =
if (!HasTrivialDestructorBody(Context, NonVirtualBase,
return false;
if (BaseClassDecl == MostDerivedClassDecl) {
// Check virtual bases.
for (const auto &I : BaseClassDecl->vbases()) {
const CXXRecordDecl *VirtualBase =
if (!HasTrivialDestructorBody(Context, VirtualBase,
return false;
return true;
static bool
FieldHasTrivialDestructorBody(ASTContext &Context,
const FieldDecl *Field)
QualType FieldBaseElementType = Context.getBaseElementType(Field->getType());
const RecordType *RT = FieldBaseElementType->getAs<RecordType>();
if (!RT)
return true;
CXXRecordDecl *FieldClassDecl = cast<CXXRecordDecl>(RT->getDecl());
// The destructor for an implicit anonymous union member is never invoked.
if (FieldClassDecl->isUnion() && FieldClassDecl->isAnonymousStructOrUnion())
return false;
return HasTrivialDestructorBody(Context, FieldClassDecl, FieldClassDecl);
/// CanSkipVTablePointerInitialization - Check whether we need to initialize
/// any vtable pointers before calling this destructor.
static bool CanSkipVTablePointerInitialization(CodeGenFunction &CGF,
const CXXDestructorDecl *Dtor) {
const CXXRecordDecl *ClassDecl = Dtor->getParent();
if (!ClassDecl->isDynamicClass())
return true;
if (!Dtor->hasTrivialBody())
return false;
// Check the fields.
for (const auto *Field : ClassDecl->fields())
if (!FieldHasTrivialDestructorBody(CGF.getContext(), Field))
return false;
return true;
/// EmitDestructorBody - Emits the body of the current destructor.
void CodeGenFunction::EmitDestructorBody(FunctionArgList &Args) {
const CXXDestructorDecl *Dtor = cast<CXXDestructorDecl>(CurGD.getDecl());
CXXDtorType DtorType = CurGD.getDtorType();
// For an abstract class, non-base destructors are never used (and can't
// be emitted in general, because vbase dtors may not have been validated
// by Sema), but the Itanium ABI doesn't make them optional and Clang may
// in fact emit references to them from other compilations, so emit them
// as functions containing a trap instruction.
if (DtorType != Dtor_Base && Dtor->getParent()->isAbstract()) {
llvm::CallInst *TrapCall = EmitTrapCall(llvm::Intrinsic::trap);
Stmt *Body = Dtor->getBody();
if (Body)
// The call to operator delete in a deleting destructor happens
// outside of the function-try-block, which means it's always
// possible to delegate the destructor body to the complete
// destructor. Do so.
if (DtorType == Dtor_Deleting) {
RunCleanupsScope DtorEpilogue(*this);
EnterDtorCleanups(Dtor, Dtor_Deleting);
if (HaveInsertPoint())
EmitCXXDestructorCall(Dtor, Dtor_Complete, /*ForVirtualBase=*/false,
/*Delegating=*/false, LoadCXXThisAddress());
// If the body is a function-try-block, enter the try before
// anything else.
bool isTryBody = (Body && isa<CXXTryStmt>(Body));
if (isTryBody)
EnterCXXTryStmt(*cast<CXXTryStmt>(Body), true);
// Enter the epilogue cleanups.
RunCleanupsScope DtorEpilogue(*this);
// If this is the complete variant, just invoke the base variant;
// the epilogue will destruct the virtual bases. But we can't do
// this optimization if the body is a function-try-block, because
// we'd introduce *two* handler blocks. In the Microsoft ABI, we
// always delegate because we might not have a definition in this TU.
switch (DtorType) {
case Dtor_Comdat: llvm_unreachable("not expecting a COMDAT");
case Dtor_Deleting: llvm_unreachable("already handled deleting case");
case Dtor_Complete:
assert((Body || getTarget().getCXXABI().isMicrosoft()) &&
"can't emit a dtor without a body for non-Microsoft ABIs");
// Enter the cleanup scopes for virtual bases.
EnterDtorCleanups(Dtor, Dtor_Complete);
if (!isTryBody) {
EmitCXXDestructorCall(Dtor, Dtor_Base, /*ForVirtualBase=*/false,
/*Delegating=*/false, LoadCXXThisAddress());
// Fallthrough: act like we're in the base variant.
case Dtor_Base:
// Enter the cleanup scopes for fields and non-virtual bases.
EnterDtorCleanups(Dtor, Dtor_Base);
// Initialize the vtable pointers before entering the body.
if (!CanSkipVTablePointerInitialization(*this, Dtor)) {
// Insert the intrinsic before initializing
// the vptrs to cancel any previous assumptions we might have made.
if (CGM.getCodeGenOpts().StrictVTablePointers &&
CGM.getCodeGenOpts().OptimizationLevel > 0)
CXXThisValue = Builder.CreateInvariantGroupBarrier(LoadCXXThis());
if (isTryBody)
else if (Body)
else {
assert(Dtor->isImplicit() && "bodyless dtor not implicit");
// nothing to do besides what's in the epilogue
// -fapple-kext must inline any call to this dtor into
// the caller's body.
if (getLangOpts().AppleKext)
// Jump out through the epilogue cleanups.
// Exit the try if applicable.
if (isTryBody)
ExitCXXTryStmt(*cast<CXXTryStmt>(Body), true);
void CodeGenFunction::emitImplicitAssignmentOperatorBody(FunctionArgList &Args) {
const CXXMethodDecl *AssignOp = cast<CXXMethodDecl>(CurGD.getDecl());
const Stmt *RootS = AssignOp->getBody();
assert(isa<CompoundStmt>(RootS) &&
"Body of an implicit assignment operator should be compound stmt.");
const CompoundStmt *RootCS = cast<CompoundStmt>(RootS);
LexicalScope Scope(*this, RootCS->getSourceRange());
AssignmentMemcpyizer AM(*this, AssignOp, Args);
for (auto *I : RootCS->body())
namespace {
llvm::Value *LoadThisForDtorDelete(CodeGenFunction &CGF,
const CXXDestructorDecl *DD) {
if (Expr *ThisArg = DD->getOperatorDeleteThisArg())
return CGF.EmitScalarExpr(ThisArg);
return CGF.LoadCXXThis();
/// Call the operator delete associated with the current destructor.
struct CallDtorDelete final : EHScopeStack::Cleanup {
CallDtorDelete() {}
void Emit(CodeGenFunction &CGF, Flags flags) override {
const CXXDestructorDecl *Dtor = cast<CXXDestructorDecl>(CGF.CurCodeDecl);
const CXXRecordDecl *ClassDecl = Dtor->getParent();
LoadThisForDtorDelete(CGF, Dtor),
void EmitConditionalDtorDeleteCall(CodeGenFunction &CGF,
llvm::Value *ShouldDeleteCondition,
bool ReturnAfterDelete) {
llvm::BasicBlock *callDeleteBB = CGF.createBasicBlock("dtor.call_delete");
llvm::BasicBlock *continueBB = CGF.createBasicBlock("dtor.continue");
llvm::Value *ShouldCallDelete
= CGF.Builder.CreateIsNull(ShouldDeleteCondition);
CGF.Builder.CreateCondBr(ShouldCallDelete, continueBB, callDeleteBB);
const CXXDestructorDecl *Dtor = cast<CXXDestructorDecl>(CGF.CurCodeDecl);
const CXXRecordDecl *ClassDecl = Dtor->getParent();
LoadThisForDtorDelete(CGF, Dtor),
assert(Dtor->getOperatorDelete()->isDestroyingOperatorDelete() ==
ReturnAfterDelete &&
"unexpected value for ReturnAfterDelete");
if (ReturnAfterDelete)
struct CallDtorDeleteConditional final : EHScopeStack::Cleanup {
llvm::Value *ShouldDeleteCondition;
CallDtorDeleteConditional(llvm::Value *ShouldDeleteCondition)
: ShouldDeleteCondition(ShouldDeleteCondition) {
assert(ShouldDeleteCondition != nullptr);
void Emit(CodeGenFunction &CGF, Flags flags) override {
EmitConditionalDtorDeleteCall(CGF, ShouldDeleteCondition,
class DestroyField final : public EHScopeStack::Cleanup {
const FieldDecl *field;
CodeGenFunction::Destroyer *destroyer;
bool useEHCleanupForArray;
DestroyField(const FieldDecl *field, CodeGenFunction::Destroyer *destroyer,
bool useEHCleanupForArray)
: field(field), destroyer(destroyer),
useEHCleanupForArray(useEHCleanupForArray) {}
void Emit(CodeGenFunction &CGF, Flags flags) override {
// Find the address of the field.
Address thisValue = CGF.LoadCXXThisAddress();
QualType RecordTy = CGF.getContext().getTagDeclType(field->getParent());
LValue ThisLV = CGF.MakeAddrLValue(thisValue, RecordTy);
LValue LV = CGF.EmitLValueForField(ThisLV, field);
CGF.emitDestroy(LV.getAddress(), field->getType(), destroyer,
flags.isForNormalCleanup() && useEHCleanupForArray);
static void EmitSanitizerDtorCallback(CodeGenFunction &CGF, llvm::Value *Ptr,
CharUnits::QuantityType PoisonSize) {
CodeGenFunction::SanitizerScope SanScope(&CGF);
// Pass in void pointer and size of region as arguments to runtime
// function
llvm::Value *Args[] = {CGF.Builder.CreateBitCast(Ptr, CGF.VoidPtrTy),
llvm::ConstantInt::get(CGF.SizeTy, PoisonSize)};
llvm::Type *ArgTypes[] = {CGF.VoidPtrTy, CGF.SizeTy};
llvm::FunctionType *FnType =
llvm::FunctionType::get(CGF.VoidTy, ArgTypes, false);
llvm::Value *Fn =
CGF.CGM.CreateRuntimeFunction(FnType, "__sanitizer_dtor_callback");
CGF.EmitNounwindRuntimeCall(Fn, Args);
class SanitizeDtorMembers final : public EHScopeStack::Cleanup {
const CXXDestructorDecl *Dtor;
SanitizeDtorMembers(const CXXDestructorDecl *Dtor) : Dtor(Dtor) {}
// Generate function call for handling object poisoning.
// Disables tail call elimination, to prevent the current stack frame
// from disappearing from the stack trace.
void Emit(CodeGenFunction &CGF, Flags flags) override {
const ASTRecordLayout &Layout =
// Nothing to poison.
if (Layout.getFieldCount() == 0)
// Prevent the current stack frame from disappearing from the stack trace.
CGF.CurFn->addFnAttr("disable-tail-calls", "true");
// Construct pointer to region to begin poisoning, and calculate poison
// size, so that only members declared in this class are poisoned.
ASTContext &Context = CGF.getContext();
unsigned fieldIndex = 0;
int startIndex = -1;
// RecordDecl::field_iterator Field;
for (const FieldDecl *Field : Dtor->getParent()->fields()) {
// Poison field if it is trivial
if (FieldHasTrivialDestructorBody(Context, Field)) {
// Start sanitizing at this field
if (startIndex < 0)
startIndex = fieldIndex;
// Currently on the last field, and it must be poisoned with the
// current block.
if (fieldIndex == Layout.getFieldCount() - 1) {
PoisonMembers(CGF, startIndex, Layout.getFieldCount());
} else if (startIndex >= 0) {
// No longer within a block of memory to poison, so poison the block
PoisonMembers(CGF, startIndex, fieldIndex);
// Re-set the start index
startIndex = -1;
fieldIndex += 1;
/// \param layoutStartOffset index of the ASTRecordLayout field to
/// start poisoning (inclusive)
/// \param layoutEndOffset index of the ASTRecordLayout field to
/// end poisoning (exclusive)
void PoisonMembers(CodeGenFunction &CGF, unsigned layoutStartOffset,
unsigned layoutEndOffset) {
ASTContext &Context = CGF.getContext();
const ASTRecordLayout &Layout =
llvm::ConstantInt *OffsetSizePtr = llvm::ConstantInt::get(
llvm::Value *OffsetPtr = CGF.Builder.CreateGEP(
CGF.Builder.CreateBitCast(CGF.LoadCXXThis(), CGF.Int8PtrTy),
CharUnits::QuantityType PoisonSize;
if (layoutEndOffset >= Layout.getFieldCount()) {
PoisonSize = Layout.getNonVirtualSize().getQuantity() -
} else {
PoisonSize = Context.toCharUnitsFromBits(
Layout.getFieldOffset(layoutEndOffset) -
if (PoisonSize == 0)
EmitSanitizerDtorCallback(CGF, OffsetPtr, PoisonSize);
class SanitizeDtorVTable final : public EHScopeStack::Cleanup {
const CXXDestructorDecl *Dtor;
SanitizeDtorVTable(const CXXDestructorDecl *Dtor) : Dtor(Dtor) {}
// Generate function call for handling vtable pointer poisoning.
void Emit(CodeGenFunction &CGF, Flags flags) override {
ASTContext &Context = CGF.getContext();
// Poison vtable and vtable ptr if they exist for this class.
llvm::Value *VTablePtr = CGF.LoadCXXThis();
CharUnits::QuantityType PoisonSize =
// Pass in void pointer and size of region as arguments to runtime
// function
EmitSanitizerDtorCallback(CGF, VTablePtr, PoisonSize);
} // end anonymous namespace
/// \brief Emit all code that comes at the end of class's
/// destructor. This is to call destructors on members and base classes
/// in reverse order of their construction.
/// For a deleting destructor, this also handles the case where a destroying
/// operator delete completely overrides the definition.
void CodeGenFunction::EnterDtorCleanups(const CXXDestructorDecl *DD,
CXXDtorType DtorType) {
assert((!DD->isTrivial() || DD->hasAttr<DLLExportAttr>()) &&
"Should not emit dtor epilogue for non-exported trivial dtor!");
// The deleting-destructor phase just needs to call the appropriate
// operator delete that Sema picked up.
if (DtorType == Dtor_Deleting) {
assert(DD->getOperatorDelete() &&
"operator delete missing - EnterDtorCleanups");
if (CXXStructorImplicitParamValue) {
// If there is an implicit param to the deleting dtor, it's a boolean
// telling whether this is a deleting destructor.
if (DD->getOperatorDelete()->isDestroyingOperatorDelete())
EmitConditionalDtorDeleteCall(*this, CXXStructorImplicitParamValue,
NormalAndEHCleanup, CXXStructorImplicitParamValue);
} else {
if (DD->getOperatorDelete()->isDestroyingOperatorDelete()) {
const CXXRecordDecl *ClassDecl = DD->getParent();
LoadThisForDtorDelete(*this, DD),
} else {
const CXXRecordDecl *ClassDecl = DD->getParent();
// Unions have no bases and do not call field destructors.
if (ClassDecl->isUnion())
// The complete-destructor phase just destructs all the virtual bases.
if (DtorType == Dtor_Complete) {
// Poison the vtable pointer such that access after the base
// and member destructors are invoked is invalid.
if (CGM.getCodeGenOpts().SanitizeMemoryUseAfterDtor &&
SanOpts.has(SanitizerKind::Memory) && ClassDecl->getNumVBases() &&
EHStack.pushCleanup<SanitizeDtorVTable>(NormalAndEHCleanup, DD);
// We push them in the forward order so that they'll be popped in
// the reverse order.
for (const auto &Base : ClassDecl->vbases()) {
CXXRecordDecl *BaseClassDecl
= cast<CXXRecordDecl>(Base.getType()->getAs<RecordType>()->getDecl());
// Ignore trivial destructors.
if (BaseClassDecl->hasTrivialDestructor())
/*BaseIsVirtual*/ true);
assert(DtorType == Dtor_Base);
// Poison the vtable pointer if it has no virtual bases, but inherits
// virtual functions.
if (CGM.getCodeGenOpts().SanitizeMemoryUseAfterDtor &&
SanOpts.has(SanitizerKind::Memory) && !ClassDecl->getNumVBases() &&
EHStack.pushCleanup<SanitizeDtorVTable>(NormalAndEHCleanup, DD);
// Destroy non-virtual bases.
for (const auto &Base : ClassDecl->bases()) {
// Ignore virtual bases.
if (Base.isVirtual())
CXXRecordDecl *BaseClassDecl = Base.getType()->getAsCXXRecordDecl();
// Ignore trivial destructors.
if (BaseClassDecl->hasTrivialDestructor())
/*BaseIsVirtual*/ false);
// Poison fields such that access after their destructors are
// invoked, and before the base class destructor runs, is invalid.
if (CGM.getCodeGenOpts().SanitizeMemoryUseAfterDtor &&
EHStack.pushCleanup<SanitizeDtorMembers>(NormalAndEHCleanup, DD);
// Destroy direct fields.
for (const auto *Field : ClassDecl->fields()) {
QualType type = Field->getType();
QualType::DestructionKind dtorKind = type.isDestructedType();
if (!dtorKind) continue;
// Anonymous union members do not have their destructors called.
const RecordType *RT = type->getAsUnionType();
if (RT && RT->getDecl()->isAnonymousStructOrUnion()) continue;
CleanupKind cleanupKind = getCleanupKind(dtorKind);
EHStack.pushCleanup<DestroyField>(cleanupKind, Field,
cleanupKind & EHCleanup);
/// EmitCXXAggrConstructorCall - Emit a loop to call a particular
/// constructor for each of several members of an array.
/// \param ctor the constructor to call for each element
/// \param arrayType the type of the array to initialize
/// \param arrayBegin an arrayType*
/// \param zeroInitialize true if each element should be
/// zero-initialized before it is constructed
void CodeGenFunction::EmitCXXAggrConstructorCall(
const CXXConstructorDecl *ctor, const ArrayType *arrayType,
Address arrayBegin, const CXXConstructExpr *E, bool zeroInitialize) {
QualType elementType;
llvm::Value *numElements =
emitArrayLength(arrayType, elementType, arrayBegin);
EmitCXXAggrConstructorCall(ctor, numElements, arrayBegin, E, zeroInitialize);
/// EmitCXXAggrConstructorCall - Emit a loop to call a particular
/// constructor for each of several members of an array.
/// \param ctor the constructor to call for each element
/// \param numElements the number of elements in the array;
/// may be zero
/// \param arrayBase a T*, where T is the type constructed by ctor
/// \param zeroInitialize true if each element should be
/// zero-initialized before it is constructed
void CodeGenFunction::EmitCXXAggrConstructorCall(const CXXConstructorDecl *ctor,
llvm::Value *numElements,
Address arrayBase,
const CXXConstructExpr *E,
bool zeroInitialize) {
// It's legal for numElements to be zero. This can happen both
// dynamically, because x can be zero in 'new A[x]', and statically,
// because of GCC extensions that permit zero-length arrays. There
// are probably legitimate places where we could assume that this
// doesn't happen, but it's not clear that it's worth it.
llvm::BranchInst *zeroCheckBranch = nullptr;
// Optimize for a constant count.
llvm::ConstantInt *constantCount
= dyn_cast<llvm::ConstantInt>(numElements);
if (constantCount) {
// Just skip out if the constant count is zero.
if (constantCount->isZero()) return;
// Otherwise, emit the check.
} else {
llvm::BasicBlock *loopBB = createBasicBlock("new.ctorloop");
llvm::Value *iszero = Builder.CreateIsNull(numElements, "isempty");
zeroCheckBranch = Builder.CreateCondBr(iszero, loopBB, loopBB);
// Find the end of the array.
llvm::Value *arrayBegin = arrayBase.getPointer();
llvm::Value *arrayEnd = Builder.CreateInBoundsGEP(arrayBegin, numElements,
// Enter the loop, setting up a phi for the current location to initialize.
llvm::BasicBlock *entryBB = Builder.GetInsertBlock();
llvm::BasicBlock *loopBB = createBasicBlock("arrayctor.loop");
llvm::PHINode *cur = Builder.CreatePHI(arrayBegin->getType(), 2,
cur->addIncoming(arrayBegin, entryBB);
// Inside the loop body, emit the constructor call on the array element.
// The alignment of the base, adjusted by the size of a single element,
// provides a conservative estimate of the alignment of every element.
// (This assumes we never start tracking offsetted alignments.)
// Note that these are complete objects and so we don't need to
// use the non-virtual size or alignment.
QualType type = getContext().getTypeDeclType(ctor->getParent());
CharUnits eltAlignment =
Address curAddr = Address(cur, eltAlignment);
// Zero initialize the storage, if requested.
if (zeroInitialize)
EmitNullInitialization(curAddr, type);
// C++ [class.temporary]p4:
// There are two contexts in which temporaries are destroyed at a different
// point than the end of the full-expression. The first context is when a
// default constructor is called to initialize an element of an array.
// If the constructor has one or more default arguments, the destruction of
// every temporary created in a default argument expression is sequenced
// before the construction of the next array element, if any.
RunCleanupsScope Scope(*this);
// Evaluate the constructor and its arguments in a regular
// partial-destroy cleanup.
if (getLangOpts().Exceptions &&
!ctor->getParent()->hasTrivialDestructor()) {
Destroyer *destroyer = destroyCXXObject;
pushRegularPartialArrayCleanup(arrayBegin, cur, type, eltAlignment,
EmitCXXConstructorCall(ctor, Ctor_Complete, /*ForVirtualBase=*/false,
/*Delegating=*/false, curAddr, E);
// Go to the next element.
llvm::Value *next =
Builder.CreateInBoundsGEP(cur, llvm::ConstantInt::get(SizeTy, 1),
cur->addIncoming(next, Builder.GetInsertBlock());
// Check whether that's the end of the loop.
llvm::Value *done = Builder.CreateICmpEQ(next, arrayEnd, "arrayctor.done");
llvm::BasicBlock *contBB = createBasicBlock("arrayctor.cont");
Builder.CreateCondBr(done, contBB, loopBB);
// Patch the earlier check to skip over the loop.
if (zeroCheckBranch) zeroCheckBranch->setSuccessor(0, contBB);
void CodeGenFunction::destroyCXXObject(CodeGenFunction &CGF,
Address addr,
QualType type) {
const RecordType *rtype = type->castAs<RecordType>();
const CXXRecordDecl *record = cast<CXXRecordDecl>(rtype->getDecl());
const CXXDestructorDecl *dtor = record->getDestructor();
CGF.EmitCXXDestructorCall(dtor, Dtor_Complete, /*for vbase*/ false,
/*Delegating=*/false, addr);
void CodeGenFunction::EmitCXXConstructorCall(const CXXConstructorDecl *D,
CXXCtorType Type,
bool ForVirtualBase,
bool Delegating, Address This,
const CXXConstructExpr *E) {
CallArgList Args;
// Push the this ptr.
Args.add(RValue::get(This.getPointer()), D->getThisType(getContext()));
// If this is a trivial constructor, emit a memcpy now before we lose
// the alignment information on the argument.
// FIXME: It would be better to preserve alignment information into CallArg.
if (isMemcpyEquivalentSpecialMember(D)) {
assert(E->getNumArgs() == 1 && "unexpected argcount for trivial ctor");
const Expr *Arg = E->getArg(0);
QualType SrcTy = Arg->getType();
Address Src = EmitLValue(Arg).getAddress();
QualType DestTy = getContext().getTypeDeclType(D->getParent());
EmitAggregateCopyCtor(This, Src, DestTy, SrcTy);
// Add the rest of the user-supplied arguments.
const FunctionProtoType *FPT = D->getType()->castAs<FunctionProtoType>();
EvaluationOrder Order = E->isListInitialization()
? EvaluationOrder::ForceLeftToRight
: EvaluationOrder::Default;
EmitCallArgs(Args, FPT, E->arguments(), E->getConstructor(),
/*ParamsToSkip*/ 0, Order);
EmitCXXConstructorCall(D, Type, ForVirtualBase, Delegating, This, Args);
static bool canEmitDelegateCallArgs(CodeGenFunction &CGF,
const CXXConstructorDecl *Ctor,
CXXCtorType Type, CallArgList &Args) {
// We can't forward a variadic call.
if (Ctor->isVariadic())
return false;
if (CGF.getTarget().getCXXABI().areArgsDestroyedLeftToRightInCallee()) {
// If the parameters are callee-cleanup, it's not safe to forward.
for (auto *P : Ctor->parameters())
if (P->getType().isDestructedType())
return false;
// Likewise if they're inalloca.
const CGFunctionInfo &Info =
CGF.CGM.getTypes().arrangeCXXConstructorCall(Args, Ctor, Type, 0, 0);
if (Info.usesInAlloca())
return false;
// Anything else should be OK.
return true;
void CodeGenFunction::EmitCXXConstructorCall(const CXXConstructorDecl *D,
CXXCtorType Type,
bool ForVirtualBase,
bool Delegating,
Address This,
CallArgList &Args) {
const CXXRecordDecl *ClassDecl = D->getParent();
// C++11 [class.mfct.non-static]p2:
// If a non-static member function of a class X is called for an object that
// is not of type X, or of a type derived from X, the behavior is undefined.
// FIXME: Provide a source location here.
EmitTypeCheck(CodeGenFunction::TCK_ConstructorCall, SourceLocation(),
This.getPointer(), getContext().getRecordType(ClassDecl));
if (D->isTrivial() && D->isDefaultConstructor()) {
assert(Args.size() == 1 && "trivial default ctor with args");
// If this is a trivial constructor, just emit what's needed. If this is a
// union copy constructor, we must emit a memcpy, because the AST does not
// model that copy.
if (isMemcpyEquivalentSpecialMember(D)) {
assert(Args.size() == 2 && "unexpected argcount for trivial ctor");
QualType SrcTy = D->getParamDecl(0)->getType().getNonReferenceType();
Address Src(Args[1].RV.getScalarVal(), getNaturalTypeAlignment(SrcTy));
QualType DestTy = getContext().getTypeDeclType(ClassDecl);
EmitAggregateCopyCtor(This, Src, DestTy, SrcTy);
bool PassPrototypeArgs = true;
// Check whether we can actually emit the constructor before trying to do so.
if (auto Inherited = D->getInheritedConstructor()) {
PassPrototypeArgs = getTypes().inheritingCtorHasParams(Inherited, Type);
if (PassPrototypeArgs && !canEmitDelegateCallArgs(*this, D, Type, Args)) {
EmitInlinedInheritingCXXConstructorCall(D, Type, ForVirtualBase,
Delegating, Args);
// Insert any ABI-specific implicit constructor arguments.
CGCXXABI::AddedStructorArgs ExtraArgs =
CGM.getCXXABI().addImplicitConstructorArgs(*this, D, Type, ForVirtualBase,
Delegating, Args);
// Emit the call.
llvm::Constant *CalleePtr =
CGM.getAddrOfCXXStructor(D, getFromCtorType(Type));
const CGFunctionInfo &Info = CGM.getTypes().arrangeCXXConstructorCall(
Args, D, Type, ExtraArgs.Prefix, ExtraArgs.Suffix, PassPrototypeArgs);
CGCallee Callee = CGCallee::forDirect(CalleePtr, D);
EmitCall(Info, Callee, ReturnValueSlot(), Args);
// Generate vtable assumptions if we're constructing a complete object
// with a vtable. We don't do this for base subobjects for two reasons:
// first, it's incorrect for classes with virtual bases, and second, we're
// about to overwrite the vptrs anyway.
// We also have to make sure if we can refer to vtable:
// - Otherwise we can refer to vtable if it's safe to speculatively emit.
// FIXME: If vtable is used by ctor/dtor, or if vtable is external and we are
// sure that definition of vtable is not hidden,
// then we are always safe to refer to it.
// FIXME: It looks like InstCombine is very inefficient on dealing with
// assumes. Make assumption loads require -fstrict-vtable-pointers temporarily.
if (CGM.getCodeGenOpts().OptimizationLevel > 0 &&
ClassDecl->isDynamicClass() && Type != Ctor_Base &&
CGM.getCXXABI().canSpeculativelyEmitVTable(ClassDecl) &&
EmitVTableAssumptionLoads(ClassDecl, This);
void CodeGenFunction::EmitInheritedCXXConstructorCall(
const CXXConstructorDecl *D, bool ForVirtualBase, Address This,
bool InheritedFromVBase, const CXXInheritedCtorInitExpr *E) {
CallArgList Args;
CallArg ThisArg(RValue::get(This.getPointer()), D->getThisType(getContext()),
// Forward the parameters.
if (InheritedFromVBase &&
CGM.getTarget().getCXXABI().hasConstructorVariants()) {
// Nothing to do; this construction is not responsible for constructing
// the base class containing the inherited constructor.
// FIXME: Can we just pass undef's for the remaining arguments if we don't
// have constructor variants?
} else if (!CXXInheritedCtorInitExprArgs.empty()) {
// The inheriting constructor was inlined; just inject its arguments.
assert(CXXInheritedCtorInitExprArgs.size() >= D->getNumParams() &&
"wrong number of parameters for inherited constructor call");
Args = CXXInheritedCtorInitExprArgs;
Args[0] = ThisArg;
} else {
// The inheriting constructor was not inlined. Emit delegating arguments.
const auto *OuterCtor = cast<CXXConstructorDecl>(CurCodeDecl);
assert(OuterCtor->getNumParams() == D->getNumParams());
assert(!OuterCtor->isVariadic() && "should have been inlined");
for (const auto *Param : OuterCtor->parameters()) {
EmitDelegateCallArg(Args, Param, E->getLocation());
// Forward __attribute__(pass_object_size).
if (Param->hasAttr<PassObjectSizeAttr>()) {
auto *POSParam = SizeArguments[Param];
assert(POSParam && "missing pass_object_size value for forwarding");
EmitDelegateCallArg(Args, POSParam, E->getLocation());
EmitCXXConstructorCall(D, Ctor_Base, ForVirtualBase, /*Delegating*/false,
This, Args);
void CodeGenFunction::EmitInlinedInheritingCXXConstructorCall(
const CXXConstructorDecl *Ctor, CXXCtorType CtorType, bool ForVirtualBase,
bool Delegating, CallArgList &Args) {
GlobalDecl GD(Ctor, CtorType);
InlinedInheritingConstructorScope Scope(*this, GD);
ApplyInlineDebugLocation DebugScope(*this, GD);
// Save the arguments to be passed to the inherited constructor.
CXXInheritedCtorInitExprArgs = Args;
FunctionArgList Params;
QualType RetType = BuildFunctionArgList(CurGD, Params);
FnRetTy = RetType;
// Insert any ABI-specific implicit constructor arguments.
CGM.getCXXABI().addImplicitConstructorArgs(*this, Ctor, CtorType,
ForVirtualBase, Delegating, Args);
// Emit a simplified prolog. We only need to emit the implicit params.
assert(Args.size() >= Params.size() && "too few arguments for call");
for (unsigned I = 0, N = Args.size(); I != N; ++I) {
if (I < Params.size() && isa<ImplicitParamDecl>(Params[I])) {
const RValue &RV = Args[I].RV;
assert(!RV.isComplex() && "complex indirect params not supported");
ParamValue Val = RV.isScalar()
? ParamValue::forDirect(RV.getScalarVal())
: ParamValue::forIndirect(RV.getAggregateAddress());
EmitParmDecl(*Params[I], Val, I + 1);
// Create a return value slot if the ABI implementation wants one.
// FIXME: This is dumb, we should ask the ABI not to try to set the return
// value instead.
if (!RetType->isVoidType())
ReturnValue = CreateIRTemp(RetType, "retval.inhctor");
CXXThisValue = CXXABIThisValue;
// Directly emit the constructor initializers.
EmitCtorPrologue(Ctor, CtorType, Params);
void CodeGenFunction::EmitVTableAssumptionLoad(const VPtr &Vptr, Address This) {
llvm::Value *VTableGlobal =
CGM.getCXXABI().getVTableAddressPoint(Vptr.Base, Vptr.VTableClass);
if (!VTableGlobal)
// We can just use the base offset in the complete class.
CharUnits NonVirtualOffset = Vptr.Base.getBaseOffset();
if (!NonVirtualOffset.isZero())
This =
ApplyNonVirtualAndVirtualOffset(*this, This, NonVirtualOffset, nullptr,
Vptr.VTableClass, Vptr.NearestVBase);
llvm::Value *VPtrValue =
GetVTablePtr(This, VTableGlobal->getType(), Vptr.VTableClass);
llvm::Value *Cmp =
Builder.CreateICmpEQ(VPtrValue, VTableGlobal, "cmp.vtables");
void CodeGenFunction::EmitVTableAssumptionLoads(const CXXRecordDecl *ClassDecl,
Address This) {
if (CGM.getCXXABI().doStructorsInitializeVPtrs(ClassDecl))
for (const VPtr &Vptr : getVTablePointers(ClassDecl))
EmitVTableAssumptionLoad(Vptr, This);
CodeGenFunction::EmitSynthesizedCXXCopyCtorCall(const CXXConstructorDecl *D,
Address This, Address Src,
const CXXConstructExpr *E) {
const FunctionProtoType *FPT = D->getType()->castAs<FunctionProtoType>();
CallArgList Args;
// Push the this ptr.
Args.add(RValue::get(This.getPointer()), D->getThisType(getContext()));
// Push the src ptr.
QualType QT = *(FPT->param_type_begin());
llvm::Type *t = CGM.getTypes().ConvertType(QT);
Src = Builder.CreateBitCast(Src, t);
Args.add(RValue::get(Src.getPointer()), QT);
// Skip over first argument (Src).
EmitCallArgs(Args, FPT, drop_begin(E->arguments(), 1), E->getConstructor(),
/*ParamsToSkip*/ 1);
EmitCXXConstructorCall(D, Ctor_Complete, false, false, This, Args);
CodeGenFunction::EmitDelegateCXXConstructorCall(const CXXConstructorDecl *Ctor,
CXXCtorType CtorType,
const FunctionArgList &Args,
SourceLocation Loc) {
CallArgList DelegateArgs;
FunctionArgList::const_iterator I = Args.begin(), E = Args.end();
assert(I != E && "no parameters to constructor");
// this
Address This = LoadCXXThisAddress();
DelegateArgs.add(RValue::get(This.getPointer()), (*I)->getType());
// FIXME: The location of the VTT parameter in the parameter list is
// specific to the Itanium ABI and shouldn't be hardcoded here.
if (CGM.getCXXABI().NeedsVTTParameter(CurGD)) {
assert(I != E && "cannot skip vtt parameter, already done with args");
assert((*I)->getType()->isPointerType() &&
"skipping parameter not of vtt type");
// Explicit arguments.
for (; I != E; ++I) {
const VarDecl *param = *I;
// FIXME: per-argument source location
EmitDelegateCallArg(DelegateArgs, param, Loc);
EmitCXXConstructorCall(Ctor, CtorType, /*ForVirtualBase=*/false,
/*Delegating=*/true, This, DelegateArgs);
namespace {
struct CallDelegatingCtorDtor final : EHScopeStack::Cleanup {
const CXXDestructorDecl *Dtor;
Address Addr;
CXXDtorType Type;
CallDelegatingCtorDtor(const CXXDestructorDecl *D, Address Addr,
CXXDtorType Type)
: Dtor(D), Addr(Addr), Type(Type) {}
void Emit(CodeGenFunction &CGF, Flags flags) override {
CGF.EmitCXXDestructorCall(Dtor, Type, /*ForVirtualBase=*/false,
/*Delegating=*/true, Addr);
} // end anonymous namespace
CodeGenFunction::EmitDelegatingCXXConstructorCall(const CXXConstructorDecl *Ctor,
const FunctionArgList &Args) {
Address ThisPtr = LoadCXXThisAddress();
AggValueSlot AggSlot =
AggValueSlot::forAddr(ThisPtr, Qualifiers(),
EmitAggExpr(Ctor->init_begin()[0]->getInit(), AggSlot);
const CXXRecordDecl *ClassDecl = Ctor->getParent();
if (CGM.getLangOpts().Exceptions && !ClassDecl->hasTrivialDestructor()) {
CXXDtorType Type =
CurGD.getCtorType() == Ctor_Complete ? Dtor_Complete : Dtor_Base;
ThisPtr, Type);
void CodeGenFunction::EmitCXXDestructorCall(const CXXDestructorDecl *DD,
CXXDtorType Type,
bool ForVirtualBase,
bool Delegating,
Address This) {
CGM.getCXXABI().EmitDestructorCall(*this, DD, Type, ForVirtualBase,
Delegating, This);
namespace {
struct CallLocalDtor final : EHScopeStack::Cleanup {
const CXXDestructorDecl *Dtor;
Address Addr;
CallLocalDtor(const CXXDestructorDecl *D, Address Addr)
: Dtor(D), Addr(Addr) {}
void Emit(CodeGenFunction &CGF, Flags flags) override {
CGF.EmitCXXDestructorCall(Dtor, Dtor_Complete,
/*Delegating=*/false, Addr);
} // end anonymous namespace
void CodeGenFunction::PushDestructorCleanup(const CXXDestructorDecl *D,
Address Addr) {
EHStack.pushCleanup<CallLocalDtor>(NormalAndEHCleanup, D, Addr);
void CodeGenFunction::PushDestructorCleanup(QualType T, Address Addr) {
CXXRecordDecl *ClassDecl = T->getAsCXXRecordDecl();
if (!ClassDecl) return;
if (ClassDecl->hasTrivialDestructor()) return;
const CXXDestructorDecl *D = ClassDecl->getDestructor();
assert(D && D->isUsed() && "destructor not marked as used!");
PushDestructorCleanup(D, Addr);
void CodeGenFunction::InitializeVTablePointer(const VPtr &Vptr) {
// Compute the address point.
llvm::Value *VTableAddressPoint =
*this, Vptr.VTableClass, Vptr.Base, Vptr.NearestVBase);
if (!VTableAddressPoint)
// Compute where to store the address point.
llvm::Value *VirtualOffset = nullptr;
CharUnits NonVirtualOffset = CharUnits::Zero();
if (CGM.getCXXABI().isVirtualOffsetNeededForVTableField(*this, Vptr)) {
// We need to use the virtual base offset offset because the virtual base
// might have a different offset in the most derived class.
VirtualOffset = CGM.getCXXABI().GetVirtualBaseClassOffset(
*this, LoadCXXThisAddress(), Vptr.VTableClass, Vptr.NearestVBase);
NonVirtualOffset = Vptr.OffsetFromNearestVBase;
} else {
// We can just use the base offset in the complete class.
NonVirtualOffset = Vptr.Base.getBaseOffset();
// Apply the offsets.
Address VTableField = LoadCXXThisAddress();
if (!NonVirtualOffset.isZero() || VirtualOffset)
VTableField = ApplyNonVirtualAndVirtualOffset(
*this, VTableField, NonVirtualOffset, VirtualOffset, Vptr.VTableClass,
// Finally, store the address point. Use the same LLVM types as the field to
// support optimization.
llvm::Type *VTablePtrTy =
llvm::FunctionType::get(CGM.Int32Ty, /*isVarArg=*/true)
VTableField = Builder.CreateBitCast(VTableField, VTablePtrTy->getPointerTo());
VTableAddressPoint = Builder.CreateBitCast(VTableAddressPoint, VTablePtrTy);
llvm::StoreInst *Store = Builder.CreateStore(VTableAddressPoint, VTableField);
CGM.DecorateInstructionWithTBAA(Store, CGM.getTBAAVTablePtrAccessInfo());
if (CGM.getCodeGenOpts().OptimizationLevel > 0 &&
CGM.DecorateInstructionWithInvariantGroup(Store, Vptr.VTableClass);
CodeGenFunction::getVTablePointers(const CXXRecordDecl *VTableClass) {
CodeGenFunction::VPtrsVector VPtrsResult;
VisitedVirtualBasesSetTy VBases;
getVTablePointers(BaseSubobject(VTableClass, CharUnits::Zero()),
/*BaseIsNonVirtualPrimaryBase=*/false, VTableClass, VBases,
return VPtrsResult;
void CodeGenFunction::getVTablePointers(BaseSubobject Base,
const CXXRecordDecl *NearestVBase,
CharUnits OffsetFromNearestVBase,
bool BaseIsNonVirtualPrimaryBase,
const CXXRecordDecl *VTableClass,
VisitedVirtualBasesSetTy &VBases,
VPtrsVector &Vptrs) {
// If this base is a non-virtual primary base the address point has already
// been set.
if (!BaseIsNonVirtualPrimaryBase) {
// Initialize the vtable pointer for this base.
VPtr Vptr = {Base, NearestVBase, OffsetFromNearestVBase, VTableClass};
const CXXRecordDecl *RD = Base.getBase();
// Traverse bases.
for (const auto &I : RD->bases()) {
CXXRecordDecl *BaseDecl
= cast<CXXRecordDecl>(I.getType()->getAs<RecordType>()->getDecl());
// Ignore classes without a vtable.
if (!BaseDecl->isDynamicClass())
CharUnits BaseOffset;
CharUnits BaseOffsetFromNearestVBase;
bool BaseDeclIsNonVirtualPrimaryBase;
if (I.isVirtual()) {
// Check if we've visited this virtual base before.
if (!VBases.insert(BaseDecl).second)
const ASTRecordLayout &Layout =
BaseOffset = Layout.getVBaseClassOffset(BaseDecl);
BaseOffsetFromNearestVBase = CharUnits::Zero();
BaseDeclIsNonVirtualPrimaryBase = false;
} else {
const ASTRecordLayout &Layout = getContext().getASTRecordLayout(RD);
BaseOffset = Base.getBaseOffset() + Layout.getBaseClassOffset(BaseDecl);
BaseOffsetFromNearestVBase =
OffsetFromNearestVBase + Layout.getBaseClassOffset(BaseDecl);
BaseDeclIsNonVirtualPrimaryBase = Layout.getPrimaryBase() == BaseDecl;
BaseSubobject(BaseDecl, BaseOffset),
I.isVirtual() ? BaseDecl : NearestVBase, BaseOffsetFromNearestVBase,
BaseDeclIsNonVirtualPrimaryBase, VTableClass, VBases, Vptrs);
void CodeGenFunction::InitializeVTablePointers(const CXXRecordDecl *RD) {
// Ignore classes without a vtable.
if (!RD->isDynamicClass())
// Initialize the vtable pointers for this class and all of its bases.
if (CGM.getCXXABI().doStructorsInitializeVPtrs(RD))
for (const VPtr &Vptr : getVTablePointers(RD))
if (RD->getNumVBases())
CGM.getCXXABI().initializeHiddenVirtualInheritanceMembers(*this, RD);
llvm::Value *CodeGenFunction::GetVTablePtr(Address This,
llvm::Type *VTableTy,
const CXXRecordDecl *RD) {
Address VTablePtrSrc = Builder.CreateElementBitCast(This, VTableTy);
llvm::Instruction *VTable = Builder.CreateLoad(VTablePtrSrc, "vtable");
CGM.DecorateInstructionWithTBAA(VTable, CGM.getTBAAVTablePtrAccessInfo());
if (CGM.getCodeGenOpts().OptimizationLevel > 0 &&
CGM.DecorateInstructionWithInvariantGroup(VTable, RD);
return VTable;
// If a class has a single non-virtual base and does not introduce or override
// virtual member functions or fields, it will have the same layout as its base.
// This function returns the least derived such class.
// Casting an instance of a base class to such a derived class is technically
// undefined behavior, but it is a relatively common hack for introducing member
// functions on class instances with specific properties (e.g. llvm::Operator)
// that works under most compilers and should not have security implications, so
// we allow it by default. It can be disabled with -fsanitize=cfi-cast-strict.
static const CXXRecordDecl *
LeastDerivedClassWithSameLayout(const CXXRecordDecl *RD) {
if (!RD->field_empty())
return RD;
if (RD->getNumVBases() != 0)
return RD;
if (RD->getNumBases() != 1)
return RD;
for (const CXXMethodDecl *MD : RD->methods()) {
if (MD->isVirtual()) {
// Virtual member functions are only ok if they are implicit destructors
// because the implicit destructor will have the same semantics as the
// base class's destructor if no fields are added.
if (isa<CXXDestructorDecl>(MD) && MD->isImplicit())
return RD;
return LeastDerivedClassWithSameLayout(
void CodeGenFunction::EmitTypeMetadataCodeForVCall(const CXXRecordDecl *RD,
llvm::Value *VTable,
SourceLocation Loc) {
if (SanOpts.has(SanitizerKind::CFIVCall))
EmitVTablePtrCheckForCall(RD, VTable, CodeGenFunction::CFITCK_VCall, Loc);
else if (CGM.getCodeGenOpts().WholeProgramVTables &&
CGM.HasHiddenLTOVisibility(RD)) {
llvm::Metadata *MD =
CGM.CreateMetadataIdentifierForType(QualType(RD->getTypeForDecl(), 0));
llvm::Value *TypeId =
llvm::MetadataAsValue::get(CGM.getLLVMContext(), MD);
llvm::Value *CastedVTable = Builder.CreateBitCast(VTable, Int8PtrTy);
llvm::Value *TypeTest =
{CastedVTable, TypeId});
Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::assume), TypeTest);
void CodeGenFunction::EmitVTablePtrCheckForCall(const CXXRecordDecl *RD,
llvm::Value *VTable,
CFITypeCheckKind TCK,
SourceLocation Loc) {
if (!SanOpts.has(SanitizerKind::CFICastStrict))
RD = LeastDerivedClassWithSameLayout(RD);
EmitVTablePtrCheck(RD, VTable, TCK, Loc);
void CodeGenFunction::EmitVTablePtrCheckForCast(QualType T,
llvm::Value *Derived,
bool MayBeNull,
CFITypeCheckKind TCK,
SourceLocation Loc) {
if (!getLangOpts().CPlusPlus)
auto *ClassTy = T->getAs<RecordType>();
if (!ClassTy)
const CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(ClassTy->getDecl());
if (!ClassDecl->isCompleteDefinition() || !ClassDecl->isDynamicClass())
if (!SanOpts.has(SanitizerKind::CFICastStrict))
ClassDecl = LeastDerivedClassWithSameLayout(ClassDecl);
llvm::BasicBlock *ContBlock = nullptr;
if (MayBeNull) {
llvm::Value *DerivedNotNull =
Builder.CreateIsNotNull(Derived, "cast.nonnull");
llvm::BasicBlock *CheckBlock = createBasicBlock("cast.check");
ContBlock = createBasicBlock("cast.cont");
Builder.CreateCondBr(DerivedNotNull, CheckBlock, ContBlock);
llvm::Value *VTable =
GetVTablePtr(Address(Derived, getPointerAlign()), Int8PtrTy, ClassDecl);
EmitVTablePtrCheck(ClassDecl, VTable, TCK, Loc);
if (MayBeNull) {
void CodeGenFunction::EmitVTablePtrCheck(const CXXRecordDecl *RD,
llvm::Value *VTable,
CFITypeCheckKind TCK,
SourceLocation Loc) {
if (!CGM.getCodeGenOpts().SanitizeCfiCrossDso &&
SanitizerMask M;
llvm::SanitizerStatKind SSK;
switch (TCK) {
case CFITCK_VCall:
M = SanitizerKind::CFIVCall;
SSK = llvm::SanStat_CFI_VCall;
case CFITCK_NVCall:
M = SanitizerKind::CFINVCall;
SSK = llvm::SanStat_CFI_NVCall;
case CFITCK_DerivedCast:
M = SanitizerKind::CFIDerivedCast;
SSK = llvm::SanStat_CFI_DerivedCast;
case CFITCK_UnrelatedCast:
M = SanitizerKind::CFIUnrelatedCast;
SSK = llvm::SanStat_CFI_UnrelatedCast;
case CFITCK_ICall:
llvm_unreachable("not expecting CFITCK_ICall");
std::string TypeName = RD->getQualifiedNameAsString();
if (getContext().getSanitizerBlacklist().isBlacklistedType(M, TypeName))
SanitizerScope SanScope(this);
llvm::Metadata *MD =
CGM.CreateMetadataIdentifierForType(QualType(RD->getTypeForDecl(), 0));
llvm::Value *TypeId = llvm::MetadataAsValue::get(getLLVMContext(), MD);
llvm::Value *CastedVTable = Builder.CreateBitCast(VTable, Int8PtrTy);
llvm::Value *TypeTest = Builder.CreateCall(
CGM.getIntrinsic(llvm::Intrinsic::type_test), {CastedVTable, TypeId});
llvm::Constant *StaticData[] = {
llvm::ConstantInt::get(Int8Ty, TCK),
EmitCheckTypeDescriptor(QualType(RD->getTypeForDecl(), 0)),
auto CrossDsoTypeId = CGM.CreateCrossDsoCfiTypeId(MD);
if (CGM.getCodeGenOpts().SanitizeCfiCrossDso && CrossDsoTypeId) {
EmitCfiSlowPathCheck(M, TypeTest, CrossDsoTypeId, CastedVTable, StaticData);
if (CGM.getCodeGenOpts().SanitizeTrap.has(M)) {
llvm::Value *AllVtables = llvm::MetadataAsValue::get(
llvm::MDString::get(CGM.getLLVMContext(), "all-vtables"));
llvm::Value *ValidVtable = Builder.CreateCall(
CGM.getIntrinsic(llvm::Intrinsic::type_test), {CastedVTable, AllVtables});
EmitCheck(std::make_pair(TypeTest, M), SanitizerHandler::CFICheckFail,
StaticData, {CastedVTable, ValidVtable});
bool CodeGenFunction::ShouldEmitVTableTypeCheckedLoad(const CXXRecordDecl *RD) {
if (!CGM.getCodeGenOpts().WholeProgramVTables ||
!SanOpts.has(SanitizerKind::CFIVCall) ||
!CGM.getCodeGenOpts().SanitizeTrap.has(SanitizerKind::CFIVCall) ||
return false;
std::string TypeName = RD->getQualifiedNameAsString();
return !getContext().getSanitizerBlacklist().isBlacklistedType(
SanitizerKind::CFIVCall, TypeName);
llvm::Value *CodeGenFunction::EmitVTableTypeCheckedLoad(
const CXXRecordDecl *RD, llvm::Value *VTable, uint64_t VTableByteOffset) {
SanitizerScope SanScope(this);
llvm::Metadata *MD =
CGM.CreateMetadataIdentifierForType(QualType(RD->getTypeForDecl(), 0));
llvm::Value *TypeId = llvm::MetadataAsValue::get(CGM.getLLVMContext(), MD);
llvm::Value *CastedVTable = Builder.CreateBitCast(VTable, Int8PtrTy);