std::unique_lock with thread annotations

Runtimes C++
1

Hi,

I’ve been experimenting with -Wthread-safety in clang/libc++. The documentation at https://libcxx.llvm.org/docs/UsingLibcxx.html says that _LIBCPP_ENABLE_THREAD_SAFETY_ANNOTATIONS is ‘used to enable -Wthread-safety annotations on libc++’s std::mutex and std::lock_guard’.

I’m hoping to use thread-safety analysis for a sizeable code base which makes a lot of use of unique_lock, but there’s no libc++ annotations for unique_lock, just for lock_guard. What is the status of this? Is this something that might be addressed in the future, or is it fundamentally problematic? I gather it’s complicated by the optional deferred locking semantics.

For my purposes I can work around the issue by changing uses of unique_lock to instead be lock_guard (which needs to be done anyway) so it’s not a show-stopper for me, just curious.

Thanks!

2

Last time I looked the attributes weren’t expressive enough to model unique_lock.
I don’t believe there’s any work on going to improve this.

I’ll happily annotate unique_lock when Clang can model it.

3

Ok, thanks for that, sounds like it’s as I’d guessed. I’ll just use lock_guard instead of unique_lock.

Thanks!