glibc/posix/spawn_valid_fd.c

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/* File descriptor validity check for posix_spawn file actions.
Copyright (C) 2000-2018 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include "spawn_int.h"
#include <unistd.h>
bool
__spawn_valid_fd (int fd)
{
long maxfd = __sysconf (_SC_OPEN_MAX);
return __glibc_likely (fd >= 0)
&& (__glibc_unlikely (maxfd < 0) /* No limit set. */
|| __glibc_likely (fd < maxfd));
}