Re: notification-fd inadvertently closed by selfpipe_finish on FreeBSD?

>Is this a bug, or am I holding it wrong?

  It is a bug indeed! Thanks for the report and the detailed analysis. 
I'll fix it asap.


>So maybe skalibs' cspawn...
>...calls cspawn_fork() on FreeBSD if CSPAWN_FLAGS_SETSID is set.
>...calls cspawn_pspawn() on macOS under the same conditions.
>
>There is no call to selfpipe_finish() in cspawn_pspawn.

  Yes. selfpipe_finish() must not be called in cspawn_pspawn() since only 
the parent
process is running; the child process is only controlled by the 
posix_spawn attributes.
With cspawn_fork(), selfpipe_finish() runs in the child.


>(I guess because of posix_spawnattr_setsigmask?)

  The signal mask must be restored before the exec in both cases. It's 
the sigmask
attribute for posix_spawn(), and selfpipe_finish() for fork().

  But all that is only where the problem manifests. The real issue 
happens much earlier:
when notification-fd is read and accepted without vetting that it's not 
clobbering the
selfpipe. This is what I'll fix.

--
  Laurent