Re: [PATCH 1/5] progress.c: replace signal() with sigaction()

From: Jeremiah Mahler <jmmahler@gmail.com>
Date: May 28, 2014, 15:45 UTC
Message-ID: <20140528154509.GA7076@hudson.localdomain>
In-Reply-To: <5385994A.5040507@gmail.com>

On Wed, May 28, 2014 at 08:07:38PM +1200, Chris Packham wrote:

Show 11 quoted lines

> On 28/05/14 18:14, Jeremiah Mahler wrote:
> > From signal(2)
> > 
> >   The behavior of signal() varies across UNIX versions, and has also var‐
> >   ied historically across different versions of Linux.   Avoid  its  use:
> >   use sigaction(2) instead.  See Portability below.
> 
> Minor nit. The last sentence applies to the man page you're quoting and
> doesn't really make sense when viewed in the context of this commit
> message. Same applies to other patches in this series.
>

Yes, that is confusing.

...

Show 14 quoted lines

> > @@ -66,8 +66,12 @@ static void set_progress_signal(void)
> >  static void clear_progress_signal(void)
> >  {
> >  	struct itimerval v = {{0,},};
> > +	struct sigaction sa;
> > +
> > +	memset(&sa, 0, sizeof(sa));
> > +	sa.sa_handler = SIG_IGN;
> 
> A C99 initialiser here would save the call to memset. Unfortunately
> Documentation/CodingGuidelines is fairly clear on not using C99
> initialisers, given the fact we're now at git 2.0 maybe it's time to
> revisit this policy?
>

struct sigaction sa = { .sa_handler = SIG_IGN };

I do like that.

This brings up another issue. memset(&sa, 0, sizeof(sa)); The sigaction examples I have seen always use memset. The manpage for sigaction(2) doesn't mention it. Other code it Git uses memset with sigaction (see fast-import.c line 530).

Is this struct guaranteed to be initialized to zero so I don't have to use memset?

-- 
Jeremiah Mahler
jmmahler@gmail.com
http://github.com/jmahler