Sender: nate AT cartsys DOT com
Message-ID: <3564F35C.A0FBA509@cartsys.com>
Date: Thu, 21 May 1998 20:39:08 -0700
From: Nate Eldredge <nate AT cartsys DOT com>
MIME-Version: 1.0
To: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>, Eric Rudd <rudd AT cyberoptics DOT com>,
        djgpp AT delorie DOT com
Subject: Re: Code to Fix sinh() in libm.a
References: <Pine DOT SUN DOT 3 DOT 91 DOT 980520121106 DOT 24974C-100000 AT is>
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Eli Zaretskii wrote:
> 
> On Tue, 19 May 1998, Eric Rudd wrote:
> > I had envisioned retaining libm as an option
> > for those who need the best possible error-handling, but upgrading libc
> > to a lean-and-mean (but accurate and ANSI-compliant) library for the
> > rest of us.
> 
> This is an okay solution, provided that the lean-and-mean version is
> indeed ANSI-compliant.  However, ANSI compliance actually requires
> errno to be set; see below.
> 
[deletia]
> > > I fail to understand this argument.  What's non-portable about
> > > assuming that errno can be set when I call, say, exp with an argument
> > > which can be large?
> >
> > Because ANSI doens't *require* it.
> 
> My references indicate that ANSI *does* require errno to be set, at
> least in some cases.  I attach several excerpts at the end of this
> message.  I think that those cases where the standard doesn't require
> errno to be set, but it can be set with no significant runtime
> penalty, it should be done.  For example, testing the result for being
> a NaN or an Inf, and setting errno if it is, doesn't seem like a large
> penalty to me.
> 

What about this idea: create another library which provides all the same
functions, but is fast instead of being ANSI-compliant. Perhaps call it
libfm.a. Then things that wanted ANSI could use -lm (or alternatively
libm's functions could be plopped directly into libc), while game
programmers etc. could use -lfm.

I realize it would be more work, but it could give the best of both
worlds.
-- 

Nate Eldredge
nate AT cartsys DOT com