Re: [PATCH] libstdc++, Darwin: Limit recursive mutex init to OS versions needing it.

[Jonathan Wakely <jwakely.gcc@gmail.com>]

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On Sun, 4 Dec 2022, 11:08 Iain Sandoe via Libstdc++, <libstdc++@gcc.gnu.org>
wrote:

> While looking at Darwin's os_defines, I wondered whether
> _GTHREAD_USE_RECURSIVE_MUTEX_INIT_FUNC was really still necessary. On
> checking
> the OS, it seems that it was a transient problem that only appears in
> Darwin11.
> Earlier versions do not have the initializer, and the operation is fixed in
> Darwin12+.  So, I figure we still need the workaround for Darwin8-11 but
> not
> later versions (patch implements this).
>
> Testing on both earlier and later systems does not (as one might expect)
> reveal
> any differences (we still have some lock-related tests that 'twinkle' so
> that
> there can be something still hidden by that).
>
> Anyway. the question is. "is there any reason not to use the system
> version of
> this where it works, or should I just leave the status quo?"  If the
> former,
> then "ok for master?".
>


Using the initializer seems preferable when it works, so ok for master,
thanks.




> thanks
> Iain
>
> -- >8 --
>
> The problem described in pr 51906 was fixed in the next OS release.  Limit
> the
> workaround to systems that need it.
>
> Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
>
> libstdc++-v3/ChangeLog:
>
>         * config/os/bsd/darwin/os_defines.h
>         (_GTHREAD_USE_RECURSIVE_MUTEX_INIT_FUNC): Limit use of this macro
>         to OS versions that need it.
> ---
>  libstdc++-v3/config/os/bsd/darwin/os_defines.h | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/libstdc++-v3/config/os/bsd/darwin/os_defines.h
> b/libstdc++-v3/config/os/bsd/darwin/os_defines.h
> index 38fdfb5f6f0..5b611d32e0d 100644
> --- a/libstdc++-v3/config/os/bsd/darwin/os_defines.h
> +++ b/libstdc++-v3/config/os/bsd/darwin/os_defines.h
> @@ -39,8 +39,12 @@
>  // implementation is not itself a weak definition).
>  #define _GLIBCXX_WEAK_DEFINITION __attribute__ ((__weak__))
>
> -// Static initializer macro is buggy in darwin, see libstdc++/51906
> +#if defined (__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) \
> +     && (__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 1080)
> +// Static initializer macro is absent for Darwin < 11 and buggy in Darwin
> 11,
> +// see libstdc++/51906.  Fixed in Darwin 12 (OS X 10.8).
>  #define _GTHREAD_USE_RECURSIVE_MUTEX_INIT_FUNC
> +#endif
>
>  // Configure checks for nanosleep fail on Darwin, but nanosleep and
>  // sched_yield are always available, so use them.
> --
> 2.37.1 (Apple Git-137.1)
>
>