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From Dean Gaudet <dgau...@arctic.org>
Subject Re: [APR] Universal return syntax
Date Mon, 01 Feb 1999 17:20:10 GMT


On Tue, 26 Jan 1999, Rodent of Unusual Size wrote:

> Dean Gaudet wrote:
> > 
> > On Mon, 25 Jan 1999, Rodent of Unusual Size wrote:
> > 
> > > them into return values; this frees errno for use by any
> > > other uses in the call stack
> > 
> > That's false of course.  errno is tainted by any libc call.
> > APR presumably will be using some of libc.
> 
> I dispute the claim that it's false.  Consider routine A calling
> routine B.  Routine B does something that sets errno, detects it,
> and returns -1.  errno is now fair game, and the value may be
> lost and no-one will know why B failed.  If B returned the error,
> even if it just copied errno as its return value, errno's volatility
> would be irrelevant.

That's not what your claim said though.  We're agreeing with each other.

> > > or parallel threads without losing
> > > the condition within the current call stack.
> > 
> > errno has no multithread problems, not sure if you're implying
> > it does or not.
> 
> I'm coming up to speed on threads and am ignorant in this area.
> Are you saying that each thread has its own copy of errno?

Yes.

Dean

> I thought it was a single global and hence susceptible to parallel
> processing stomping on it.
> -- 
> #ken    P-)}
> 
> Ken Coar                    <http://Web.Golux.Com/coar/>
> Apache Group member         <http://www.apache.org/>
> "Apache Server for Dummies" <http://Web.Golux.Com/coar/ASFD/>
> 


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