Re: [PATCH] libstdc++/112351 - deal with __gthread_once failure during locale init

[Jakub Jelinek <jakub@redhat.com>]

On Mon, Nov 06, 2023 at 11:52:08AM +0000, Richard Biener wrote:
> The following makes the C++98 locale init path follow the way the
> C++11 performs initialization.  This way we deal with pthread_once
> failing, falling back to non-threadsafe initialization which, given we
> initialize from the library, should be serialized by the dynamic
> loader already.
> 
> Bootstrapped and tested on x86_64-unknown-linux-gnu, OK for trunk?
> And GCC 13 branch?
> 
> Thanks,
> Richard.
> 
> 	PR libstdc++/112351
> libstdc++-v3/
> 	* src/c++98/locale.cc (locale::facet::_S_get_c_locale):
> 	Always perform non-threadsafe init when threadsafe init
> 	failed.
> ---
>  libstdc++-v3/src/c++98/locale.cc | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/libstdc++-v3/src/c++98/locale.cc b/libstdc++-v3/src/c++98/locale.cc
> index d308140bab7..e9bec1db3b6 100644
> --- a/libstdc++-v3/src/c++98/locale.cc
> +++ b/libstdc++-v3/src/c++98/locale.cc
> @@ -216,12 +216,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>  #ifdef __GTHREADS
>      if (__gthread_active_p())
>        __gthread_once(&_S_once, _S_initialize_once);
> -    else
>  #endif
> -      {
> -	if (!_S_c_locale)
> -	  _S_initialize_once();
> -      }
> +    if (__builtin_expect (!_S_c_locale, 0))
> +      _S_initialize_once();
>      return _S_c_locale;

Wouldn't it be better to just test __gthread_once return value
#ifdef __THREADS
  if ((!__gthread_active_p()
       || __gthread_once(&_S_once, _S_initialize_once)))
#endif
    if (!_S_c_locale)
      _S_initialize_once();
?

	Jakub