[clang] [Clang] Static and explicit object member functions with the same parameter-type-lists (PR #93430)

[David Blaikie via cfe-commits]

dwblaikie wrote:

Hit an msan use-of-uninitialized on an internal use case (a tool that uses Clang via API).

the test was compiling this source code:
```
#include <string>
namespace proto2 {
struct Message {};
}  // namespace proto2
struct FakeProto : proto2::Message {
  const std::string& getter() const { return str; }  // NOLINT
  static std::string str;
};
struct S {
  S(std::string) {}  // NOLINT
};
void UseS(S s) {}
const std::string& foo() {
  FakeProto fp;
  return fp.getter();
}
void baz() { UseS(foo()); }
std::string s = foo();
```

and failed in this stack:
```
   #0 0x7f1da36404cd in NoteFunctionCandidate third_party/llvm/llvm-project/clang/lib/Sema/SemaOverload.cpp:12113:35
    #1 0x7f1da36404cd in clang::OverloadCandidateSet::NoteCandidates(clang::Sema&, llvm::ArrayRef<clang::Expr*>, llvm::ArrayRef<clang::OverloadCandidate*>, llvm::StringRef, clang::SourceLocation) third_party/llvm/llvm-project/clang/lib/Sema/SemaOverload.cpp:12733:7
    #2 0x7f1da3207016 in clang::InitializationSequence::Diagnose(clang::Sema&, clang::InitializedEntity const&, clang::InitializationKind const&, llvm::ArrayRef<clang::Expr*>) third_party/llvm/llvm-project/clang/lib/Sema/SemaInit.cpp:9933:26
    #3 0x7f1da31fa0e2 in clang::InitializationSequence::Perform(clang::Sema&, clang::InitializedEntity const&, clang::InitializationKind const&, llvm::MutableArrayRef<clang::Expr*>, clang::QualType*) third_party/llvm/llvm-project/clang/lib/Sema/SemaInit.cpp:8705:5
    #4 0x7f1da2704fbe in clang::Sema::AddInitializerToDecl(clang::Decl*, clang::Expr*, bool) third_party/llvm/llvm-project/clang/lib/Sema/SemaDecl.cpp:13730:33
    #5 0x7f1da58cfea0 in clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::ForRangeInit*) third_party/llvm/llvm-project/clang/lib/Parse/ParseDecl.cpp:2787:17
    #6 0x7f1da58c924b in clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::ParsedAttributes&, clang::Parser::ParsedTemplateInfo&, clang::SourceLocation*, clang::Parser::ForRangeInit*) third_party/llvm/llvm-project/clang/lib/Parse/ParseDecl.cpp:2480:7
    #7 0x7f1da5b06b4d in clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec&, clang::AccessSpecifier) third_party/llvm/llvm-project/clang/lib/Parse/Parser.cpp:1249:10
    #8 0x7f1da5b058b0 in clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*, clang::AccessSpecifier) third_party/llvm/llvm-project/clang/lib/Parse/Parser.cpp:1271:12
    #9 0x7f1da5b0338b in clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) third_party/llvm/llvm-project/clang/lib/Parse/Parser.cpp:1074:14
    #10 0x7f1da5afe984 in clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) third_party/llvm/llvm-project/clang/lib/Parse/Parser.cpp:763:12
    #11 0x7f1da588c011 in clang::ParseAST(clang::Sema&, bool, bool) third_party/llvm/llvm-project/clang/lib/Parse/ParseAST.cpp:163:20
    #12 0x7f1da743f407 in clang::ASTFrontendAction::ExecuteAction() third_party/llvm/llvm-project/clang/lib/Frontend/FrontendAction.cpp:1192:3
    #13 0x7f1da743dfab in clang::FrontendAction::Execute() third_party/llvm/llvm-project/clang/lib/Frontend/FrontendAction.cpp:1078:8
```

I realize this isn't exactly repro steps - the <string> included is from libc++, for what that's worth - I don't /think/ this build is using modules.

But providing this info in case it's sufficient information to diagnose the issue.

It seems to be the TookAddressOfOverload variable is used-uninitialized somewhere in this path.

(I don't actually have a clang-built-with-msan to test this further myself at the moment, but trying to figure out some bootstrapping issues to try to help narrow it down)

https://github.com/llvm/llvm-project/pull/93430