RE: Possible bug in wait4(), 2.1.126-129 ?

Guest section DW (dwguest@win.tue.nl)
Tue, 24 Nov 1998 22:39:23 +0100 (MET)


From ionut@moisil.cs.columbia.edu Tue Nov 24 11:29:08 1998

Too bad it's not documented anywhere. All the (Linux) documentation I had
access to said that the above behavior cannot happen.

> Note that POSIX explicitly disallows setting the action
> of SIGCHLD to SIG_IGN. It follows that crond and atd are
> not POSIX compliant.

Never mind POSIX though, as long as Linux allows it it ought to be
documented, even if it has a big warning before it.

Hint for the Linux man pages maintainer? :-)

Thanks for the hint. But you are right, it was not documented.
The man pages for signal and sigaction now say:

According to POSIX (B.3.3.1.3) you must not set the action
for SIGCHLD to SIG_IGN. Here the BSD and SYSV behaviours
differ. It is unwise to know what Linux does.

(so here we differ perhaps - I do not want to know what Linux does,
just as I do not want to know the order of the bytes in an integer -
such knowledge always comes back to haunt you).

This also answers

From jsp@ms.com Tue Nov 24 17:44:35 1998
From: Jan-Simon Pendry <jsp@ms.com>

the copy of posix in my hands just says that the behaviour of SIGCHLD
set to SIG_IGN is unspecified.

Yes, that is what 3.3.1.3 says. But B.3.3.1.3 uses slightly stronger wording.

Andries

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