Date: Tue, 21 May 2013 07:57:02 +0200 From: Polytropon <freebsd@edvax.de> To: Noel Hunt <noel.hunt@gmail.com> Cc: freebsd-questions@freebsd.org Subject: Re: signal vs. sigaction and SIGCHLD Message-ID: <20130521075702.6d59bbac.freebsd@edvax.de> In-Reply-To: <CAGfO01wE7ZROQWTv7TXZdSySqWCkRqj7dcqDDc28-jvhqMuVDw@mail.gmail.com> References: <CAGfO01wE7ZROQWTv7TXZdSySqWCkRqj7dcqDDc28-jvhqMuVDw@mail.gmail.com>
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On Tue, 21 May 2013 15:24:26 +1000, Noel Hunt wrote:
> If I recompile with `#undef SIGACTION', waithandler is not
> called.
>
> I should add that even with the sigaction(2) interface, without
> the `sigprocmask' call, it still doesn't work, which suggests
> that SIGCHLD is being blocked.
>
> Can anyone explain why?
>From reading "man 3 signal", I get the following impression:
No Name Default Action Description
20 SIGCHLD discard signal child status has changed
The default action is to discard the signal, so the following
paragraph could make sense:
The sig argument specifies which signal was received. The func procedure
allows a user to choose the action upon receipt of a signal. To set the
default action of the signal to occur as listed above, func should be
SIG_DFL. A SIG_DFL resets the default action. To ignore the signal func
should be SIG_IGN. This will cause subsequent instances of the signal to
be ignored and pending instances to be discarded. If SIG_IGN is not
used, further occurrences of the signal are automatically blocked and
func is called.
>From my limited understanding, maybe this could help you find
an explanation of the observed behaviour?
Also compare /usr/include/sys/signal.h for the definition of
the involved typedef's.
--
Polytropon
Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...
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