On Mon, 6 Nov 2023 at 12:16, Jakub Jelinek <ja...@redhat.com> wrote:
>
> 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();
> ?
This still has the problem of calling the function twice, once because
__gthread_once fails and one because it succeeds.
