Re: Can't ignore signal CHLD, forcing to default

From: Solar Designer (solar@private)
Date: Thu Jan 23 2003 - 18:35:22 PST


On Wed, Jan 22, 2003 at 10:03:25AM -0600, Steve Bremer wrote:

Hi Steve,

> 00 01 * * * /sbin/system_check.pl
> 
> Each time it runs, I also receive the message: 
> 
> Can't ignore signal CHLD, forcing to default

Thanks for reminding me of this issue (yes, it's been reported once
before).

> http://www.netbsd.org/cgi-bin/query-pr-single.pl?number=11778
> 
> The patch to OpenBSD listed in the post looks like it would apply 
> cleanly to the version of cron provided with Owl.

Yes, -- and it appears to be the correct fix.

> However, after 
> looking at the source code, it looks to me like there is a reason that 
> SIG_IGN was used instead of SIG_DFL when USE_SIGCHLD is defined.

I think the only reason SIG_IGN was used is that Vixie Cron was
written prior to the newer standards which now leave the behavior for
{SIGCHLD, SIG_IGN} only partially specified, and in a new way.  I
don't think the behavior was ever fully specified, but it's natural to
write "SIG_IGN" when you're thinking "ignore".  Now this combination
is just non-portable and should be avoided.

For SIGCHLD, default action (SIG_DFL) is to ignore the signal, so we
may just use that.

-- 
/sd



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