- Use pipe2 on Linux and BSDs, which can set all flags through a single syscall.
- macOS/darwin does not support pipe2, add a wrapper for it.
- Close pipes when fork() failed. These fds should be closed when
the function returns.
- Set O_CLOEXEC at pipes, the exec() family of functions will close
this fds automatically.
- Use _exit instead of exit. Exit calls the callbacks registered by atexit
and flushes the stdio's buffer, which can lead to some unexpected behavior,
especially after an exec syscall failure.
- Fix timeout.
- Not use non-blocking IO. because we only wait for one file, and cannot
do other things during waiting.
`write` in child process blocks when the pipe is full. However because we are `waitpid`ing, we don't read the pipe, so that the pipe is never free. Therefore `write` in child process blocks forever and `waitpid` hangs.
Fix#493
李通洲