dnl OpenBSD 4.7 unsetenv("") does not fail.
AC_CACHE_CHECK([whether unsetenv obeys POSIX],
[gl_cv_func_unsetenv_works],
[AC_RUN_IFELSE([AC_LANG_PROGRAM([[
#include <stdlib.h>
#include <errno.h>
dnl OpenBSD 4.7 unsetenv("") does not fail.
AC_CACHE_CHECK([whether unsetenv obeys POSIX],
[gl_cv_func_unsetenv_works],
[AC_RUN_IFELSE([AC_LANG_PROGRAM([[
#include <stdlib.h>
#include <errno.h>