Path: utzoo!attcan!uunet!know!zaphod.mps.ohio-state.edu!lavaca.uh.edu!menudo.uh.edu!sugar!ficc!peter
From: peter@ficc.ferranti.com (Peter da Silva)
Newsgroups: comp.lang.c
Subject: Re: Ambiguity in definition of setjmp/longjmp makes them much less useful
Message-ID: <5KC6SXG@xds13.ferranti.com>
Date: 11 Oct 90 17:13:59 GMT
References: <1597@redsox.bsw.com> <1990Oct09.143521.24019@unx.sas.com> <1990Oct10.152659.6334@zoo.toronto.edu>
Reply-To: peter@ficc.ferranti.com (Peter da Silva)
Organization: Xenix Support, FICC
Lines: 11

In article <1990Oct10.152659.6334@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes:
> In article <1990Oct09.143521.24019@unx.sas.com> sasrer@unx.sas.com (Rodney Radford) writes:
> >I believe (just guessing really) that the original C used 'builtins' for the
> >setjmp/longjmp functions, ie: they special cased them.

> Nope.  The original pdp11 C compiler had a predictable stack-frame format
> and could do stack unravelling right.

It also didn't do any optimisations across statement boundaries or past
function calls, that I know of. So there wasn't anything sitting in a
register waiting to get clobbered when you did the longjmp().
-- 
Peter da Silva.   `-_-'
+1 713 274 5180.   'U`
peter@ferranti.com