Date: Thu, 14 Jun 2001 10:08:27 -0700 (PDT) From: Matt Dillon <dillon@earth.backplane.com> To: Terry Lambert <tlambert2@mindspring.com> Cc: Cejka Rudolf <cejkar@dcse.fee.vutbr.cz>, David Malone <dwmalone@maths.tcd.ie>, Peter Wemm <peter@wemm.org>, hackers@FreeBSD.ORG Subject: Re: signal(SIGCHLD, SIG_IGN) patch solving SUSv2 compatibility issue Message-ID: <200106141708.f5EH8Re24543@earth.backplane.com> References: <200106101845.f5AIje014790@earth.backplane.com> <20010611002050.362CE380E@overcee.netplex.com.au> <20010611115806.A53216@walton.maths.tcd.ie> <20010612095323.A72009@dcse.fee.vutbr.cz> <200106121638.f5CGcOo42940@earth.backplane.com> <3B285C40.6500519C@mindspring.com> <200106140657.f5E6v7i20197@earth.backplane.com> <3B2884C1.A938821A@mindspring.com>
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:Matt Dillon wrote:
:> The issue here is first: since we are fixing a bug we might
:> as well be as compatible as possible with other platforms and,
:> second: on general principles it does make sense to keep SIG_IGN
:> operation independant from the newer SA_NOCLDWAIT stuff. A program
:> using SIG_IGN has absolutely no expectation that that use will
:> effect the sigaction flags, so us modifying the sigaction flags
:> accomplish absolutely nothing and could in fact be detrimental of
:> some poor sod of a programmer writing code on a FreeBSD box actually
:> started depending on the side effect.
:
:You made the point earlier about SIG_IGN vs. SIG_DFL, and
:avoiding a side effect there.
:
:
:The side effect here is similar:
:
:I set SIG_IGN sith signal(), then get the flags (which show a
:zero), and then set them with sigaction() -- clearing the bit
:that results in the implied side effect behaviour with SIG_IGN.
:
:Further, if I have historically depended upon being able to
:seperately deal with SA_NOCLDWAIT so as to be able to reap
:childgren whose STOP/CONT I wanted to ignore, then I am
:now screwed, and have to handle all or none of them, and
:there is nothing I can do to my source code to fix it, short
:of adding STOP/CONT handlers and explicitly "handling" the
:job control crap.
Umm. Terry, I really have no idea what you are talking about.
:> So I agree with Cejka - the first patch was pretty good but didn't
:> quite hit the mark and now we have a new candidate patch that seems to
:> cover all the bases, which David Malone is reviewing and will
:> probably commit to -current (and me to stable afterwords).
:
:This breaks software which depends on the historical behaviour,
:since there is no way to recover the historical behaviour, and
:no way to know that you aren't recovering the historical
:behaviour.
What historical behavior? That FreeBSD was not properly
dealing with SIG_IGN when every other UNIX does?
So you are saying that your interest is in writing software
that only works under FreeBSD? I'm sorry, I don't buy it.
:At least with a SA_CLDWAIT flag, you could do the ignore and
:you would get a compilation warning on half your programs (the
:ones that used the now useless SA_NOCLDWAIT).
Again, I have no idea what you are talking about here. Why
would we want to introduce a non-standard flag?
-Matt
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