[Bug libstdc++/96817] __cxa_guard_acquire unsafe against dynamically loaded pthread

[yshuiv7 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96817

--- Comment #15 from Yuxuan Shui <yshuiv7 at gmail dot com> ---
(In reply to Jonathan Wakely from comment #13)
> (In reply to Yuxuan Shui from comment #1)
> > Example:
> > 
> > This program normally deadlocks when using linked pthread:
> > 
> > https://godbolt.org/z/Yrza4e
> > 
> > But it will throw recursive_init_error when using dlopen'd pthread:
> > 
> > https://godbolt.org/z/afMe5d
> 
> I'm not sure what these examples are very helpful. Throwing
> recursive_init_error is the correct behaviour here, it's a bug that we fail
> to detect the recursion when it happens in the same thread.

This is just to demonstrate the difference in the behavior. It's easy to
imagine this happen in a legitimate use case (and we indeed have one).