Python 在FreeBSD下使用os.WNOHANG时，os.waitpid的状态值是否不可靠？

waitpid文档表示，如果子进程尚未退出，则返回值将是

（0,0）

，但是在FreeBSD（FreeBSD 10.3-RELEASE-p7）上，有时会返回

（0，-512）

或

（0，-2048）

。示例程序：

#!/usr/bin/env python

import os
import sys
import time

def show_waitpid_results(results):
    print("results: %s" % (str(results)))
    print("core: %r continued: %r stopped: %r signaled: %r exited %r" %
        (
            os.WCOREDUMP(results[1]),
            os.WIFCONTINUED(results[1]),
            os.WIFSTOPPED(results[1]),
            os.WIFSIGNALED(results[1]),
            os.WIFEXITED(results[1]))
        )
    if os.WIFEXITED(results[1]):
        print("exit code: %r" % (os.WEXITSTATUS(results[1])))

if __name__ == '__main__':
    try:
        pid = os.fork()
        if pid:
            print("in parent. child pid: %r" % (pid))
            while True:
                waitpid_result = os.waitpid(pid, os.WNOHANG)
                show_waitpid_results(waitpid_result)
                if waitpid_result == (0,0) or waitpid_result == (0,-512):
                    time.sleep(.1)
                    pass
                else:
                    break
            print("parent exiting")
        else:
            # child
            time.sleep(.5)
            print("child exiting with exit code 10");
            sys.exit(10)
    except Exception:
        e = sys.exc_info()[1]
        print("error: %s"%(e))
        sys.exit(20)

osx（Python 2.7.11）和ubuntu（Python 2.7.6）上的正确输出（类似/相同）

不对？FreeBSD（Python 2.7.12）上的行为：

我还看到了FreeBSD下的-2048对-512

---

当使用

os.WNOHANG

时，可能FreeBSD上的状态值（返回元组中的第二个元素）未正确初始化？我不能依靠waitpid返回

（0,0）

？

来简单地看一下：是的。如果将WNOHANG作为waitpid的一个选项，并且没有要报告的内容，则返回0，变量kern_exit.c:：sys_wait4:：status仍然是未初始化的垃圾，但仍然复制到用户的

status

参数中。感谢@MarkPlotnick提供的指针。我用a验证了我得到了相同的（垃圾）-512行为。现在我想知道这是一个FreeBSD错误还是Python方面的错误（无效假设？或文档错误？），我认为这是一个FreeBSD错误。我阅读了POSIX标准的页面，虽然系统不需要在*状态下返回任何有意义的内容，但如果waitpid没有报告任何内容，则返回未初始化的内核变量的内容可能会导致信息泄漏。

in parent. child pid: 3196
results: (0, 0)
core: False continued: False stopped: False signaled: False exited True
exit code: 0
results: (0, 0)
core: False continued: False stopped: False signaled: False exited True
exit code: 0
results: (0, 0)
core: False continued: False stopped: False signaled: False exited True
exit code: 0
results: (0, 0)
core: False continued: False stopped: False signaled: False exited True
exit code: 0
results: (0, 0)
core: False continued: False stopped: False signaled: False exited True
exit code: 0
child exiting with exit code 10
results: (0, 0)
core: False continued: False stopped: False signaled: False exited True
exit code: 0
results: (3196, 2560)
core: False continued: False stopped: False signaled: False exited True
exit code: 10
parent exiting

in parent. child pid: 5054
results: (0, -512)
core: False continued: False stopped: False signaled: False exited True
exit code: -2
results: (0, -512)
core: False continued: False stopped: False signaled: False exited True
exit code: -2
results: (0, -512)
core: False continued: False stopped: False signaled: False exited True
exit code: -2
results: (0, -512)
core: False continued: False stopped: False signaled: False exited True
exit code: -2
results: (0, -512)
core: False continued: False stopped: False signaled: False exited True
exit code: -2
child exiting with exit code 10
results: (5054, 2560)
core: False continued: False stopped: False signaled: False exited True
exit code: 10
parent exiting