vfscanf
=======

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

Gnulib module: vfscanf, nonblocking

Portability problems fixed by Gnulib module vfscanf, together with module nonblocking:

  * When reading from a non-blocking pipe whose buffer is empty, this function fails with errno being set to EINVAL instead of EAGAIN on some platforms: mingw, MSVC 14.

Portability problems not fixed by Gnulib:

  * This function is missing on some platforms: Minix 3.1.8, IRIX 6.5.

  * On Windows platforms (excluding Cygwin), this function does not set errno upon failure.

  * On Windows, this function doesn't support the hh, ll, j, t, z size specifiers.