Re: [PATCH 2/3] posix: Use posix_spawn on popen

[David Newall <glibc at davidnewall dot com>]

On 18/09/18 00:20, Rich Felker wrote:
> The historical contract of vfork is that you can basically do nothing
> after it returns in the child except for exec or _exit
Yes, that is true.  My  understanding is that vfork was intended only as 
a fast way of doing fork/exec sequence.

> One thing to note is that vfork is completely unsafe to use as
> documented if any signal handlers are installed, unless you block all
> signals before calling vfork, in which case the exec'd process will
> inherit a fully-blocked signal mask which is probably not what you
> want. Otherwise signal handlers may wrongly run in the child that's
> sharing memory with the parent.

You're saying that kernel will deliver a signal to child pid when it was 
parent pid that was signalled.  Can that really happen?