cosmopolitan/libc/calls/getpid.c

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ This program is free software; you can redistribute it and/or modify         │
│ it under the terms of the GNU General Public License as published by         │
│ the Free Software Foundation; version 2 of the License.                      │
│                                                                              │
│ This program 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             │
│ General Public License for more details.                                     │
│                                                                              │
│ You should have received a copy of the GNU General Public License            │
│ along with this program; if not, write to the Free Software                  │
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA                │
│ 02110-1301 USA                                                               │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/assert.h"
#include "libc/calls/calls.h"
#include "libc/calls/internal.h"
#include "libc/dce.h"
#include "libc/nt/process.h"
#include "libc/runtime/runtime.h"

static int g_pid;

static int __get_pid(void) {
  if (!IsWindows()) {
    return getpid$sysv();
  } else {
    return GetCurrentProcessId();
  }
}

static void __update_pid(void) {
  g_pid = __get_pid();
}

/**
 * Returns process id.
 * @asyncsignalsafe
 */
int getpid(void) {
  static bool once;
  if (!once) {
    __update_pid();
    atfork(__update_pid, NULL);
    once = true;
  }
  return g_pid;
}