X-Authentication-Warning: delorie.com: mail set sender to djgpp-workers-bounces using -f
Sender: rich AT phekda DOT freeserve DOT co DOT uk
Message-ID: <3FACD2AA.8C08E9F4@phekda.freeserve.co.uk>
Date: Sat, 08 Nov 2003 11:25:30 +0000
From: Richard Dawe <rich AT phekda DOT freeserve DOT co DOT uk>
X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.2.23 i586)
X-Accept-Language: de,fr
MIME-Version: 1.0
To: djgpp-workers AT delorie DOT com
Subject: Re: C99 Functions Under Development and Checkout
References: <1eb DOT 12bb4eae DOT 2cdd71ca AT aol DOT com>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Reply-To: djgpp-workers AT delorie DOT com

Hello.

Kbwms AT aol DOT com wrote:
> 
> Attached to this email is the C code that implements global variable
> math_errhandling and associated macros.

Cool, thanks!

> Noted below are additions to math.h:
> 
> #define MATH_ERRNO        1
> #define MATH_ERREXCEPT 2
> extern int math_errhandling;
> 
> int get_math_errhandling (void);
> int set_math_errhandling (int);
> void set_errno (int);
> int raise_except (int);

This are functions internal to libc. They should be prefixed with "__", to
avoid polluting the global namespace. They should also go in the not-ANSI,
not-POSIX section of <math.h>.

I'd also suggest that set_errno and raise_except are renamed. These names are
fairly generic and not obviously related to the maths module. How about these
names instead?

__get_math_errhandling
__set_math_errhandling
__math_set_errno
__math_raise_exception

The second two have math at the start of their names, because they're internal
to the maths module. The first two actually manipulate math_errhandling, hence
they have get/set at the start of their names.

[snip]
> Comments are welcome.  Please look the code over and let me know whether
> there is a gotcha lurking.

Do the maths functions use get_math_errhandling, to get the value of
math_errhandling? Or do they just read math_errhandling? If they look at
math_errhandling, then get_math_errhandling is useless. The library user could
modify math_errhandling, making the value returned by get_math_errhandling
completely bogus.

It would be better for math_errhandling to be a macro calling
get_math_errhandling. That way the user cannot modify math_errhandling. Put
something like this in <math.h>:

#define math_errhandling (__get_math_errhandling())

And modify errhndlr.c like this:

[snip]
> int         math_errhandling;
[snip]

static int         math_errhandling = 0;

Then use math_errhandling instead of LocalMathErrHandling in the code.

What do you think?

Thanks, bye, Rich =]

-- 
Richard Dawe [ http://www.phekda.freeserve.co.uk/richdawe/ ]

"You can't evaluate a man by logic alone." -- McCoy, "I, Mudd", Star Trek