asctime_r
=========

POSIX specification:
 https://pubs.opengroup.org/onlinepubs/9699919799/functions/asctime_r.html

Future POSIX removal:
 https://www.austingroupbugs.net/view.php?id=1410

Gnulib module: extensions

Portability problems fixed by Gnulib:

  * This function has an incompatible declaration on some platforms: Solaris 11.4 (when _POSIX_PTHREAD_SEMANTICS is not defined).

Portability problems not fixed by Gnulib:

  * This function is missing on some platforms: mingw, MSVC 14.

  * POSIX says this function is obsolescent and it is planned to be removed in a future version. Use the function strftime (or even sprintf) instead.

  * This function may put more than 26 bytes into the argument buffer if an invalid year is passed.