Re: [PATCH v2 1/3] compat/posix.h: track SA_RESTART fallback

From: Carlo Marcelo Arenas Belón <carenas@gmail.com>
Date: Jun 25, 2025, 22:24 UTC
Message-ID: <4oh4eatsp4wo4ur6rluy6ickfy5jfpuarg435vplrqzvk3eaiz@jbtnnwqnz2yi>
In-Reply-To: <xmqq4iw3yfd8.fsf@gitster.g>

On Wed, Jun 25, 2025 at 09:07:15AM -0800, Junio C Hamano wrote:

Show 15 quoted lines

> "Carlo Marcelo Arenas Belón via GitGitGadget"
> <gitgitgadget@gmail.com> writes:
> 
> > +# Define USE_NON_POSIX_SIGNAL if don't have support for SA_RESTART or
> > +# prefer using ANSI C signal() over POSIX sigaction()
> > +
> > +AC_CACHE_CHECK([whether SA_RESTART is supported], [ac_cv_siginterrupt], [
> > +	AC_COMPILE_IFELSE(
> > +		[AC_LANG_PROGRAM([#include <signal.h>], [[
> > +		#ifdef SA_RESTART
> > +		#endif
> > +		siginterrupt(SIGCHLD, 1)
> 
> This is curious.  What is this #ifdef/#endif doing that does not
> have anything in it?

It checks that `SA_RESTART` is defined in `signal.h`, which should fail at least in QNX, NonStop and Windows.

Carlo