-Wdocumentation causes sporadic crash in clang::ASTContext::getRawCommentForDeclNoCacheImpl

[seanm]

Bugzilla Link	49707
Version	11.0
OS	MacOS X
Attachments	repro case
CC	@zygoloid

Extended Description

We have a source file that reliably, but not always, causes clang 11.0.0 to crash if and only if -Wdocumentation is used.

The .sh and .m file that the crash generates to not reproduce the issue, at least not readily. Perhaps with ASan or similar it might. They are attached regardless.

The only special thing about the source file (we think) is that it #includes another source file.

We made a little shell script (runner.sh) that runs multiple clang processes. On some Macs it crashes quite easily, on others even running overnight it does not. We did not try other OSes.

We've also observed that after leaving it running for a little while, then pressing Ctrl-C to cancel, clang will also crash, with seemingly the same backtrace!

This crash also happens with AppleClang from Xcode 12 onwards, but not earlier. So it's probably a regression, though we did not regress it against open source clang.

See the attached archive for the reproducer shell script, there's also a Read Me inside. Hopefully you can repro.

The backtrace from clang 11.0.0 [1] is:

0 clang 0x000000010b4c4465 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 37
1 clang 0x000000010b4c33f8 llvm::sys::RunSignalHandlers() + 248
2 clang 0x000000010b4c3a30 llvm::sys::CleanupOnSignal(unsigned long) + 208
3 clang 0x000000010b41505d CrashRecoverySignalHandler(int) + 189
4 libsystem_platform.dylib 0x00007fff700f25fd _sigtramp + 29
5 libsystem_platform.dylib 0x00007fdfb4858e00 _sigtramp + 18446743937419208736
6 clang 0x000000010d511b11 clang::ASTContext::getRawCommentForDeclNoCacheImpl(clang::Decl const*, clang::SourceLocation, std::__1::map<unsigned int, clang::RawComment*, std::__1::less, std::__1::allocator<std::__1::pair<unsigned int const, clang::RawComment*> > > const&) const + 513
7 clang 0x000000010d51261a clang::ASTContext::attachCommentsToJustParsedDecls(llvm::ArrayRefclang::Decl*, clang::Preprocessor const*) + 378
8 clang 0x000000010cead50a clang::Sema::BuildDeclaratorGroup(llvm::MutableArrayRefclang::Decl*) + 986
9 clang 0x000000010cfa08b8 clang::Sema::ActOnFinishObjCImplementation(clang::Decl*, llvm::ArrayRefclang::Decl*) + 328
10 clang 0x000000010cc6178c clang::Parser::ParseObjCAtImplementationDeclaration(clang::SourceLocation, clang::ParsedAttributes&) + 2828
11 clang 0x000000010ccb44ac clang::Parser::ParseExternalDeclaration(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*) + 540
12 clang 0x000000010ccb3050 clang::Parser::ParseTopLevelDecl(clang::OpaquePtrclang::DeclGroupRef&, bool) + 1408
13 clang 0x000000010cc00bad clang::ParseAST(clang::Sema&, bool, bool) + 509
14 clang 0x000000010bcde8da clang::FrontendAction::Execute() + 90
15 clang 0x000000010bc66fa1 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) + 2097
16 clang 0x000000010bd4f50a clang::ExecuteCompilerInvocation(clang::CompilerInstance*) + 1962
17 clang 0x000000010989f123 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) + 2131
18 clang 0x000000010989d23c ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&) + 316
19 clang 0x000000010baf2557 void llvm::function_ref<void ()>::callback_fn<clang::driver::CC1Command::Execute(llvm::ArrayRef<llvm::Optionalllvm::StringRef >, std::__1::basic_string<char, std::__1::char_traits, std::__1::allocator >, bool) const::$_1>(long) + 23
20 clang 0x000000010b414e12 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) + 226
21 clang 0x000000010baf1915 clang::driver::CC1Command::Execute(llvm::ArrayRef<llvm::Optionalllvm::StringRef >, std::__1::basic_string<char, std::__1::char_traits, std::__1::allocator >, bool) const + 341
22 clang 0x000000010bac186b clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&) const + 411
23 clang 0x000000010bac1d8c clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::__1::pair<int, clang::driver::Command const*> >&) const + 124
24 clang 0x000000010bada64c clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::__1::pair<int, clang::driver::Command const*> >&) + 396
25 clang 0x000000010989cbf8 main + 10264

[1] specifically: https://github.com/llvm/llvm-project/releases/download/llvmorg-11.0.0/clang+llvm-11.0.0-x86_64-apple-darwin.tar.xz

[seanm]

OK, so in fact I can't attach the .sh and .m file that the crash generates, because even maximally compressed it's more than the 1 MB that bugzilla allows. Anyway, as I said, it doesn't even help to repro, so no big loss.