| Message ID | 871rdhhgyq.fsf@oldenburg.str.redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | nptl: Mention libstdc++ compatibility for pthread_once | expand |
* Florian Weimer via Libc-alpha: > --- > nptl/pthread_once.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/nptl/pthread_once.c b/nptl/pthread_once.c > index 28d97097c7..702d1c0877 100644 > --- a/nptl/pthread_once.c > +++ b/nptl/pthread_once.c > @@ -61,7 +61,15 @@ clear_once_control (void *arg) > interrupted cases anymore. > XXX: We split out this slow path because current compilers do not generate > as efficient code when the fast path in __pthread_once below is not in a > - separate function. */ > + separate function. > + > + Compatibility note: The implementation of std::call_once in > + libstdc++ before GCC 11 does not call pthread_once if the control > + object has the value __PTHREAD_ONCE_DONE (2). libstdc++ starting > + in GCC 11 uses the values 0 (uninitialized), 1 (in progress), 2 > + (done) for its own from-scratch implementation. These > + implementations can operate on the same control object if libstdc++ > + is statically linked. */ > static int > __attribute__ ((noinline)) > __pthread_once_slow (pthread_once_t *once_control, void (*init_routine) (void)) I'm dropping this patch, it's not correct and no longer relevant. Thanks, Florian
diff --git a/nptl/pthread_once.c b/nptl/pthread_once.c index 28d97097c7..702d1c0877 100644 --- a/nptl/pthread_once.c +++ b/nptl/pthread_once.c @@ -61,7 +61,15 @@ clear_once_control (void *arg) interrupted cases anymore. XXX: We split out this slow path because current compilers do not generate as efficient code when the fast path in __pthread_once below is not in a - separate function. */ + separate function. + + Compatibility note: The implementation of std::call_once in + libstdc++ before GCC 11 does not call pthread_once if the control + object has the value __PTHREAD_ONCE_DONE (2). libstdc++ starting + in GCC 11 uses the values 0 (uninitialized), 1 (in progress), 2 + (done) for its own from-scratch implementation. These + implementations can operate on the same control object if libstdc++ + is statically linked. */ static int __attribute__ ((noinline)) __pthread_once_slow (pthread_once_t *once_control, void (*init_routine) (void))