Hi rnk, hansw,
The MS ABI utilizes a compiler generated function called the "vector
constructor iterator" to construct arrays of objects with
non-trivial constructors/destructors. For this to work, the constructor
must follow a specific calling convention. A thunk must be created if
the default constructor has default arguments, is variadic or is
otherwise incompatible. This thunk is called the default constructor
closure.
N.B. Default constructor closures are only generated if the default
constructor is exported because clang itself does not utilize vector
constructor iterators. Failing to export the default constructor
closure will result in link/load failure if a translation unit compiled
with MSVC is on the import side.
http://reviews.llvm.org/D8331
Files:
lib/AST/MicrosoftMangle.cpp
lib/CodeGen/CGCall.cpp
lib/CodeGen/CodeGenTypes.h
lib/CodeGen/MicrosoftCXXABI.cpp
lib/Sema/SemaDecl.cpp
test/CodeGenCXX/dllexport.cpp
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Index: lib/AST/MicrosoftMangle.cpp
===================================================================
--- lib/AST/MicrosoftMangle.cpp
+++ lib/AST/MicrosoftMangle.cpp
@@ -1640,10 +1640,11 @@
->getPointeeType(),
/*SpelledAsLValue=*/true),
Range);
+ Out << '@';
} else {
llvm_unreachable("unexpected constructor closure!");
}
- Out << "@Z";
+ Out << 'Z';
return;
}
Out << '@';
Index: lib/CodeGen/CGCall.cpp
===================================================================
--- lib/CodeGen/CGCall.cpp
+++ lib/CodeGen/CGCall.cpp
@@ -347,12 +347,16 @@
}
const CGFunctionInfo &
-CodeGenTypes::arrangeMSCopyCtorClosure(const CXXConstructorDecl *CD) {
+CodeGenTypes::arrangeMSCtorClosure(const CXXConstructorDecl *CD,
+ CXXCtorType CT) {
+ assert(CT == Ctor_CopyingClosure || CT == Ctor_DefaultClosure);
+
CanQual<FunctionProtoType> FTP = GetFormalType(CD);
SmallVector<CanQualType, 2> ArgTys;
const CXXRecordDecl *RD = CD->getParent();
ArgTys.push_back(GetThisType(Context, RD));
- ArgTys.push_back(*FTP->param_type_begin());
+ if (CT == Ctor_CopyingClosure)
+ ArgTys.push_back(*FTP->param_type_begin());
if (RD->getNumVBases() > 0)
ArgTys.push_back(Context.IntTy);
CallingConv CC = Context.getDefaultCallingConvention(
Index: lib/CodeGen/CodeGenTypes.h
===================================================================
--- lib/CodeGen/CodeGenTypes.h
+++ lib/CodeGen/CodeGenTypes.h
@@ -264,7 +264,8 @@
const FunctionProtoType *type,
RequiredArgs required);
const CGFunctionInfo &arrangeMSMemberPointerThunk(const CXXMethodDecl *MD);
- const CGFunctionInfo &arrangeMSCopyCtorClosure(const CXXConstructorDecl *CD);
+ const CGFunctionInfo &arrangeMSCtorClosure(const CXXConstructorDecl *CD,
+ CXXCtorType CT);
const CGFunctionInfo &arrangeFreeFunctionType(CanQual<FunctionProtoType> Ty);
const CGFunctionInfo &arrangeFreeFunctionType(CanQual<FunctionNoProtoType> Ty);
Index: lib/CodeGen/MicrosoftCXXABI.cpp
===================================================================
--- lib/CodeGen/MicrosoftCXXABI.cpp
+++ lib/CodeGen/MicrosoftCXXABI.cpp
@@ -635,7 +635,8 @@
return Fn;
}
- llvm::Function *getAddrOfCXXCopyCtorClosure(const CXXConstructorDecl *CD);
+ llvm::Function *getAddrOfCXXCtorClosure(const CXXConstructorDecl *CD,
+ CXXCtorType CT);
llvm::Constant *getCatchableType(QualType T,
uint32_t NVOffset = 0,
@@ -1063,6 +1064,22 @@
void MicrosoftCXXABI::EmitCXXConstructors(const CXXConstructorDecl *D) {
// There's only one constructor type in this ABI.
CGM.EmitGlobal(GlobalDecl(D, Ctor_Complete));
+
+ // Exported default constructors either have a simple call-site where they use
+ // the typical calling convention and have a single 'this' pointer for an
+ // argument -or- they get a wrapper function which appropriately thunks to the
+ // real default constructor. This thunk is the default constructor closure.
+ if (D->hasAttr<DLLExportAttr>() && D->isDefaultConstructor()) {
+ CallingConv ExpectedCallingConv = getContext().getDefaultCallingConvention(
+ /*IsVariadic=*/false, /*IsCXXMethod=*/true);
+ CallingConv ActualCallingConv =
+ D->getType()->getAs<FunctionProtoType>()->getCallConv();
+ if (ExpectedCallingConv != ActualCallingConv || D->getNumParams() != 0) {
+ llvm::Function *Fn = getAddrOfCXXCtorClosure(D, Ctor_DefaultClosure);
+ Fn->setLinkage(llvm::GlobalValue::WeakODRLinkage);
+ Fn->setDLLStorageClass(llvm::GlobalValue::DLLExportStorageClass);
+ }
+ }
}
void MicrosoftCXXABI::EmitVBPtrStores(CodeGenFunction &CGF,
@@ -3223,47 +3240,51 @@
}
llvm::Function *
-MicrosoftCXXABI::getAddrOfCXXCopyCtorClosure(const CXXConstructorDecl *CD) {
+MicrosoftCXXABI::getAddrOfCXXCtorClosure(const CXXConstructorDecl *CD,
+ CXXCtorType CT) {
+ assert(CT == Ctor_CopyingClosure || CT == Ctor_DefaultClosure);
+
// Calculate the mangled name.
SmallString<256> ThunkName;
llvm::raw_svector_ostream Out(ThunkName);
- getMangleContext().mangleCXXCtor(CD, Ctor_CopyingClosure, Out);
+ getMangleContext().mangleCXXCtor(CD, CT, Out);
Out.flush();
// If the thunk has been generated previously, just return it.
if (llvm::GlobalValue *GV = CGM.getModule().getNamedValue(ThunkName))
return cast<llvm::Function>(GV);
// Create the llvm::Function.
- const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeMSCopyCtorClosure(CD);
+ const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeMSCtorClosure(CD, CT);
llvm::FunctionType *ThunkTy = CGM.getTypes().GetFunctionType(FnInfo);
const CXXRecordDecl *RD = CD->getParent();
QualType RecordTy = getContext().getRecordType(RD);
llvm::Function *ThunkFn = llvm::Function::Create(
ThunkTy, getLinkageForRTTI(RecordTy), ThunkName.str(), &CGM.getModule());
+ bool IsCopy = CT == Ctor_CopyingClosure;
// Start codegen.
CodeGenFunction CGF(CGM);
CGF.CurGD = GlobalDecl(CD, Ctor_Complete);
// Build FunctionArgs.
FunctionArgList FunctionArgs;
- // A copy constructor always starts with a 'this' pointer as its first
- // argument.
+ // A constructor always starts with a 'this' pointer as its first argument.
buildThisParam(CGF, FunctionArgs);
// Following the 'this' pointer is a reference to the source object that we
// are copying from.
ImplicitParamDecl SrcParam(
getContext(), nullptr, SourceLocation(), &getContext().Idents.get("src"),
getContext().getLValueReferenceType(RecordTy,
/*SpelledAsLValue=*/true));
- FunctionArgs.push_back(&SrcParam);
+ if (IsCopy)
+ FunctionArgs.push_back(&SrcParam);
- // Copy constructors for classes which utilize virtual bases have an
- // additional parameter which indicates whether or not it is being delegated
- // to by a more derived constructor.
+ // Constructors for classes which utilize virtual bases have an additional
+ // parameter which indicates whether or not it is being delegated to by a more
+ // derived constructor.
ImplicitParamDecl IsMostDerived(getContext(), nullptr, SourceLocation(),
&getContext().Idents.get("is_most_derived"),
getContext().IntTy);
@@ -3278,27 +3299,29 @@
llvm::Value *This = getThisValue(CGF);
llvm::Value *SrcVal =
- CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(&SrcParam), "src");
+ IsCopy ? CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(&SrcParam), "src")
+ : nullptr;
CallArgList Args;
// Push the this ptr.
Args.add(RValue::get(This), CD->getThisType(getContext()));
// Push the src ptr.
- Args.add(RValue::get(SrcVal), SrcParam.getType());
+ if (SrcVal)
+ Args.add(RValue::get(SrcVal), SrcParam.getType());
// Add the rest of the default arguments.
std::vector<Stmt *> ArgVec;
- for (unsigned I = 1, E = CD->getNumParams(); I != E; ++I)
+ for (unsigned I = IsCopy ? 1 : 0, E = CD->getNumParams(); I != E; ++I)
ArgVec.push_back(getContext().getDefaultArgExprForConstructor(CD, I));
CodeGenFunction::RunCleanupsScope Cleanups(CGF);
const auto *FPT = CD->getType()->castAs<FunctionProtoType>();
ConstExprIterator ArgBegin(ArgVec.data()),
ArgEnd(ArgVec.data() + ArgVec.size());
- CGF.EmitCallArgs(Args, FPT, ArgBegin, ArgEnd, CD, 1);
+ CGF.EmitCallArgs(Args, FPT, ArgBegin, ArgEnd, CD, IsCopy ? 1 : 0);
// Insert any ABI-specific implicit constructor arguments.
unsigned ExtraArgs = addImplicitConstructorArgs(CGF, CD, Ctor_Complete,
@@ -3358,7 +3381,7 @@
llvm::Constant *CopyCtor;
if (CD) {
if (CT == Ctor_CopyingClosure)
- CopyCtor = getAddrOfCXXCopyCtorClosure(CD);
+ CopyCtor = getAddrOfCXXCtorClosure(CD, Ctor_CopyingClosure);
else
CopyCtor = CGM.getAddrOfCXXStructor(CD, StructorType::Complete);
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -12077,9 +12077,32 @@
RD->completeDefinition();
}
- if (isa<CXXRecordDecl>(Tag))
+ if (auto *Class = dyn_cast<CXXRecordDecl>(Tag)) {
FieldCollector->FinishClass();
+ // Default constructors that are annotated with __declspec(dllexport) which
+ // have default arguments or don't use the standard calling convention are
+ // wrapped with a thunk called the default constructor closure.
+ if (!Class->getDescribedClassTemplate() &&
+ Context.getTargetInfo().getCXXABI().isMicrosoft()) {
+ for (Decl *Member : Class->decls()) {
+ auto *CD = dyn_cast<CXXConstructorDecl>(Member);
+ if (!CD || !CD->isDefaultConstructor() || !CD->hasAttr<DLLExportAttr>())
+ continue;
+
+ for (unsigned I = 0, E = CD->getNumParams(); I != E; ++I) {
+ // Skip any default arguments that we've already instantiated.
+ if (Context.getDefaultArgExprForConstructor(CD, I))
+ continue;
+
+ Expr *DefaultArg = BuildCXXDefaultArgExpr(Class->getLocation(), CD,
+ CD->getParamDecl(I)).get();
+ Context.addDefaultArgExprForConstructor(CD, I, DefaultArg);
+ }
+ }
+ }
+ }
+
// Exit this scope of this tag's definition.
PopDeclContext();
Index: test/CodeGenCXX/dllexport.cpp
===================================================================
--- test/CodeGenCXX/dllexport.cpp
+++ test/CodeGenCXX/dllexport.cpp
@@ -484,6 +484,15 @@
};
};
+struct ClassWithClosure {
+ __declspec(dllexport) ClassWithClosure(...) {}
+// M32-DAG: define weak_odr dllexport void @"\01??_FClassWithClosure@@QAEXXZ"
+// M32-DAG: %[[this_addr:.*]] = alloca %struct.ClassWithClosure*, align 4
+// M32-DAG: store %struct.ClassWithClosure* %this, %struct.ClassWithClosure** %[[this_addr]], align 4
+// M32-DAG: %[[this:.*]] = load %struct.ClassWithClosure*, %struct.ClassWithClosure** %this.addr
+// M32-DAG: call %struct.ClassWithClosure* (%struct.ClassWithClosure*, ...)* @"\01??0ClassWithClosure@@QAA@ZZ"(%struct.ClassWithClosure* %[[this]])
+// M32-DAG: ret void
+};
struct __declspec(dllexport) T {
// Copy assignment operator:
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