[CodeGen] Emit a CoreFoundation link guard when @available is used
After r297760, __isOSVersionAtLeast in compiler-rt loads the CoreFoundation
symbols at runtime. This means that `@available` will always fail when used in a
binary without a linked CoreFoundation.
This commit forces Clang to emit a reference to a CoreFoundation symbol when
`@available` is used to ensure that linking will fail when CoreFoundation isn't
linked with the build product.
rdar://31039592
Differential Revision: https://reviews.llvm.org/D30977
llvm-svn: 298588
diff --git a/clang/lib/CodeGen/CGObjC.cpp b/clang/lib/CodeGen/CGObjC.cpp
index 4954a0d..4af5af9 100644
--- a/clang/lib/CodeGen/CGObjC.cpp
+++ b/clang/lib/CodeGen/CGObjC.cpp
@@ -3416,4 +3416,37 @@
return Builder.CreateICmpNE(CallRes, llvm::Constant::getNullValue(Int32Ty));
}
+void CodeGenModule::emitAtAvailableLinkGuard() {
+ if (!IsOSVersionAtLeastFn)
+ return;
+ // @available requires CoreFoundation only on Darwin.
+ if (!Target.getTriple().isOSDarwin())
+ return;
+ // Add -framework CoreFoundation to the linker commands. We still want to
+ // emit the core foundation reference down below because otherwise if
+ // CoreFoundation is not used in the code, the linker won't link the
+ // framework.
+ auto &Context = getLLVMContext();
+ llvm::Metadata *Args[2] = {llvm::MDString::get(Context, "-framework"),
+ llvm::MDString::get(Context, "CoreFoundation")};
+ LinkerOptionsMetadata.push_back(llvm::MDNode::get(Context, Args));
+ // Emit a reference to a symbol from CoreFoundation to ensure that
+ // CoreFoundation is linked into the final binary.
+ llvm::FunctionType *FTy =
+ llvm::FunctionType::get(Int32Ty, {VoidPtrTy}, false);
+ llvm::Constant *CFFunc =
+ CreateRuntimeFunction(FTy, "CFBundleGetVersionNumber");
+
+ llvm::FunctionType *CheckFTy = llvm::FunctionType::get(VoidTy, {}, false);
+ llvm::Function *CFLinkCheckFunc = cast<llvm::Function>(CreateBuiltinFunction(
+ CheckFTy, "__clang_at_available_requires_core_foundation_framework"));
+ CFLinkCheckFunc->setLinkage(llvm::GlobalValue::LinkOnceAnyLinkage);
+ CFLinkCheckFunc->setVisibility(llvm::GlobalValue::HiddenVisibility);
+ CodeGenFunction CGF(*this);
+ CGF.Builder.SetInsertPoint(CGF.createBasicBlock("", CFLinkCheckFunc));
+ CGF.EmitNounwindRuntimeCall(CFFunc, llvm::Constant::getNullValue(VoidPtrTy));
+ CGF.Builder.CreateUnreachable();
+ addCompilerUsedGlobal(CFLinkCheckFunc);
+}
+
CGObjCRuntime::~CGObjCRuntime() {}