memcmp
======

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

Gnulib module: memcmp

Portability problems fixed by Gnulib:

  * This function fails when comparing 16 bytes or more and with at least one buffer not starting on a 4-byte boundary on some older platforms: NeXTstep/x86.

Portability problems not fixed by Gnulib:

  * This function produces wrong results when the arguments are constant strings and the compiler is clang 6.0.1.