unsetenv
========

POSIX specification:
 http://www.opengroup.org/onlinepubs/9699919799/functions/unsetenv.html

Gnulib module: unsetenv

Portability problems fixed by Gnulib:

  * This function is missing on some platforms: AIX 5.1, HP-UX 11, IRIX 6.5, Solaris 9, mingw, BeOS.

  * This function has the return type void instead of int on some platforms: MacOS X 10.3, FreeBSD 6.0, NetBSD 1.6, OpenBSD 3.8, OSF/1 5.1.

  * On some platforms, this function does not fail with EINVAL when passed an empty string or a string containing =: FreeBSD 6.0, NetBSD 1.6, OpenBSD 4.7.

  * This function removes only the first value association for the given environment variable, not all of them, on some platforms: Solaris 10.

Portability problems not fixed by Gnulib:

  * Older versions of POSIX required that unsetenv(NULL) gracefully fail with EINVAL, but not all implementations guarantee this, and the requirement was removed.