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"GCC emits an __objc_class_name_{classname} symbol for every class, and a corresponding reference to this symbol for every compilation unit that references the class. This causes linker errors when you try linking a program which references some classes but doesn't define them. The attached patch implements this support in clang, so you can compile a class with clang, reference it in a file compiled with GCC, and have it all work correctly." 

Patch by David Chisnall!

llvm-svn: 73364
This commit is contained in:
Chris Lattner 2009-06-15 01:09:11 +00:00
parent 4fe64deb7b
commit c7d2bfacef
1 changed files with 29 additions and 4 deletions
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33
clang/lib/CodeGen/CGObjCGNU.cpp
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@ -104,6 +104,7 @@ private:
std::vector<llvm::Constant*> &V, const std::string &Name="");
llvm::GlobalVariable *ObjCIvarOffsetVariable(const ObjCInterfaceDecl *ID,
const ObjCIvarDecl *Ivar);
void EmitClassRef(const std::string &className);
public:
CGObjCGNU(CodeGen::CodeGenModule &cgm);
virtual llvm::Constant *GenerateConstantString(const ObjCStringLiteral *);
@ -168,15 +169,31 @@ public:
} // end anonymous namespace
/// Emits a reference to a dummy variable which is emitted with each class.
/// This ensures that a linker error will be generated when trying to link
/// together modules where a referenced class is not defined.
void CGObjCGNU::EmitClassRef(const std::string &className){
std::string symbolRef = "__objc_class_ref_" + className;
// Don't emit two copies of the same symbol
if (TheModule.getGlobalVariable(symbolRef)) return;
std::string symbolName = "__objc_class_name_" + className;
llvm::GlobalVariable *ClassSymbol = TheModule.getGlobalVariable(symbolName);
if (!ClassSymbol) {
ClassSymbol = new llvm::GlobalVariable(LongTy, false,
llvm::GlobalValue::ExternalLinkage, 0, symbolName, &TheModule);
}
new llvm::GlobalVariable(ClassSymbol->getType(), true,
llvm::GlobalValue::CommonLinkage, ClassSymbol, symbolRef, &TheModule);
}
static std::string SymbolNameForClass(const std::string &ClassName) {
return "___objc_class_name_" + ClassName;
return "_OBJC_CLASS_" + ClassName;
}
static std::string SymbolNameForMethod(const std::string &ClassName, const
std::string &CategoryName, const std::string &MethodName, bool isClassMethod)
{
return "._objc_method_" + ClassName +"("+CategoryName+")"+
return "_OBJC_METHOD_" + ClassName + "("+CategoryName+")"+
(isClassMethod ? "+" : "-") + MethodName;
}
@ -217,6 +234,7 @@ CGObjCGNU::CGObjCGNU(CodeGen::CodeGenModule &cgm)
llvm::Value *CGObjCGNU::GetClass(CGBuilderTy &Builder,
const ObjCInterfaceDecl *OID) {
llvm::Value *ClassName = CGM.GetAddrOfConstantCString(OID->getNameAsString());
EmitClassRef(OID->getNameAsString());
ClassName = Builder.CreateStructGEP(ClassName, 0);
std::vector<const llvm::Type*> Params(1, PtrToInt8Ty);
@ -831,14 +849,21 @@ void CGObjCGNU::GenerateClass(const ObjCImplementationDecl *OID) {
const ObjCInterfaceDecl * SuperClassDecl =
OID->getClassInterface()->getSuperClass();
std::string SuperClassName;
if (SuperClassDecl)
if (SuperClassDecl) {
SuperClassName = SuperClassDecl->getNameAsString();
EmitClassRef(SuperClassName);
}
// Get the class name
ObjCInterfaceDecl *ClassDecl =
const_cast<ObjCInterfaceDecl *>(OID->getClassInterface());
std::string ClassName = ClassDecl->getNameAsString();
// Emit the symbol that is used to generate linker errors if this class is
// referenced in other modules but not declared.
new llvm::GlobalVariable(LongTy, false, llvm::GlobalValue::ExternalLinkage,
llvm::ConstantInt::get(LongTy, 0), "__objc_class_name_" + ClassName,
&TheModule);
// Get the size of instances.
int instanceSize = Context.getASTObjCImplementationLayout(OID).getSize() / 8;