fsync
=====

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

Gnulib module: fsync

Portability problems fixed by Gnulib:

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

Portability problems not fixed by Gnulib:

  * If the argument is a read-only file descriptor, this function fails with EBADF on some platforms: AIX 7.2, Cygwin 2.9.