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

From: Junio C Hamano <[email-masked]>
Date: Wed, 25 Jun 2025 09:07:15 -0700

"Carlo Marcelo Arenas Belón via GitGitGadget"
<[email-masked]> 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?

> +		]])],[ac_cv_siginterrupt=yes],[
> +			ac_cv_siginterrupt=no
> +			USE_NON_POSIX_SIGNAL=UnfortunatelyYes
> +		]
> +	)
> +])
> +GIT_CONF_SUBST([USE_NON_POSIX_SIGNAL])