From 023cc968e1295994ed8039da43b0f2f4ea4e9390 Mon Sep 17 00:00:00 2001 From: Josh Stone Date: Fri, 19 Nov 2021 19:33:29 -0800 Subject: Make `LLVMRustGetOrInsertGlobal` always return a `GlobalVariable` `Module::getOrInsertGlobal` returns a `Constant*`, which is a super class of `GlobalVariable`, but if the given type doesn't match an existing declaration, it returns a bitcast of that global instead. This causes UB when we pass that to `LLVMGetVisibility` which unconditionally casts the opaque argument to a `GlobalValue*`. Instead, we can do our own get-or-insert without worrying whether existing types match exactly. It's not relevant when we're just trying to get/set the linkage and visibility, and if types are needed we can bitcast or error nicely from `rustc_codegen_llvm` instead. --- compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) (limited to 'compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp') diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp index e77d29bed71..f3d8eb2602a 100644 --- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp +++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp @@ -124,8 +124,18 @@ extern "C" LLVMValueRef LLVMRustGetOrInsertFunction(LLVMModuleRef M, extern "C" LLVMValueRef LLVMRustGetOrInsertGlobal(LLVMModuleRef M, const char *Name, size_t NameLen, LLVMTypeRef Ty) { + Module *Mod = unwrap(M); StringRef NameRef(Name, NameLen); - return wrap(unwrap(M)->getOrInsertGlobal(NameRef, unwrap(Ty))); + + // We don't use Module::getOrInsertGlobal because that returns a Constant*, + // which may either be the real GlobalVariable*, or a constant bitcast of it + // if our type doesn't match the original declaration. We always want the + // GlobalVariable* so we can access linkage, visibility, etc. + GlobalVariable *GV = Mod->getGlobalVariable(NameRef, true); + if (!GV) + GV = new GlobalVariable(*Mod, unwrap(Ty), false, + GlobalValue::ExternalLinkage, nullptr, NameRef); + return wrap(GV); } extern "C" LLVMValueRef -- cgit 1.4.1-3-g733a5