From owner-freebsd-questions  Thu Apr  5 14:39:53 2001
Delivered-To: freebsd-questions@freebsd.org
Received: from mail.thpoon.com (cr103675-a.bloor1.on.wave.home.com [24.42.106.79])
	by hub.freebsd.org (Postfix) with SMTP id 3371A37B449
	for <freebsd-questions@FreeBSD.ORG>; Thu,  5 Apr 2001 14:39:49 -0700 (PDT)
	(envelope-from a.genkin@utoronto.ca)
Received: (qmail 11592 invoked from network); 5 Apr 2001 21:39:48 -0000
Received: from unknown (HELO tea.thpoon.com) (qmailr@192.168.1.2)
  by cr103675-a.bloor1.on.wave.home.com with SMTP; 5 Apr 2001 21:39:48 -0000
Received: (qmail 2873 invoked by uid 1000); 5 Apr 2001 21:39:47 -0000
To: lucas@slb.to
Cc: freebsd-questions@FreeBSD.ORG
Subject: Re: [OT] Reinstalling signal handler inside signal handler
References: <87d7ardw5s.fsf@tea.thpoon.com>
	<20010405161123.A18827@billygoat.slb.to>
X-Face:  0=A/O5-+sE[Tf%X>rYr?Y5LD4,:^'jaJ!4jC&UR*ZrrK2>^`g22Qeb]!:d;}2YJ|Hq"LHdF
 OX`jWX|AT-WVFQ(TPhFVak)0nt$aEdlOq=1~D,:\z5QlVOrZ2(H,mKg=Xr|'VlHA="r
From: Arcady Genkin <a.genkin@utoronto.ca>
Date: 05 Apr 2001 17:39:47 -0400
In-Reply-To: <20010405161123.A18827@billygoat.slb.to>
Message-ID: <87vgojc9gc.fsf@tea.thpoon.com>
Lines: 40
User-Agent: Gnus/5.0808 (Gnus v5.8.8) XEmacs/21.1 (Cuyahoga Valley)
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Sender: owner-freebsd-questions@FreeBSD.ORG
Precedence: bulk
X-Loop: FreeBSD.ORG

Lucas Bergman <lucas@slb.to> writes:

> Signals on "traditional" systems (V7, System V) were reset to their
> default behavior after they were raised, so the signal handler had to
> reinstall itself if it was to persist.  BSD changed that; you have to
> deliberately reset a signal's behavior (excuse the split infinitive).
> Linux actually follows the old semantics, but you can include
> <bsd/signal.h> instead of <signal.h> (or call __bsd_signal() instead
> of signal()) to get the BSD semantics.  Confused yet?

Lucas, thanks for your answer.  For the record, it seems like Linux
does use the *BSD* sematics that you describe above.  For example, the
following code works the same way on both FreeBSD and Linux.

#include <stdlib.h>
#include <signal.h>

void
handler( int sig )
{
    puts( "foo" );
}

void
main(void)
{
    if ( signal( SIGUSR1, handler ) == SIG_ERR )
        exit(1);

    while (1) {
        printf( "%d\n", getpid() );
        sleep(1);
    }
}

So, is it better to reinstall the signal within the handler for
portabiity?  It seems like it can't hurt.
-- 
Arcady Genkin
Nostalgia isn't what it used to be.

To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-questions" in the body of the message