Re: [PATCH] lib/stdio.in.h: define _POSIX_C_SOURCE on >=Sierra

[Bruno Haible]

Paul Eggert wrote:
> the business with 
> __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ is taken from unistd.in.h.
> 
> /* Suppress macOS deprecation warnings for sprintf and vsprintf.  */
> #if (defined __APPLE__ && defined __MACH__) && !defined _POSIX_C_SOURCE
> # ifdef __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__
> #  include <AvailabilityMacros.h>
> # endif
> # if (defined MAC_OS_X_VERSION_MIN_REQUIRED \
>        && 101300 <= MAC_OS_X_VERSION_MIN_REQUIRED)
> #  define _POSIX_C_SOURCE 200809L
> #  define _GL_DEFINED__POSIX_C_SOURCE
> # endif
> #endif

This looks good.

In [1] I wrote: "I'll prefer to use the macros without __ prefix; it
looks safer to use AvailabilityMacros.h than to bypass it."
But as long as we don't have proof of the contrary, both the idiom from
unistd.h and the idiom from get_ppid_of.c look equally safe to use.

Bruno

[1] https://lists.gnu.org/archive/html/bug-gnulib/2021-12/msg00071.html