On Thu, Mar 21, 2002 at 12:33:45PM +1100, Bruce Evans wrote:
> On Wed, 20 Mar 2002, Steve Kargl wrote:
> I forgot about the missing __pure2 in <math.h>.  (It prevents gcc
> doing optimizations like moving sqrt(2) out of loops.) There is
> another thread on freebsd-standards about _MULTI_LIBM support.  I

I'm not subscribed to freebsd-standards.  Too many list, too
little time.  I guess I'll go browse the archive.

> want the errno support completely removed so that we have a chance
> of declaring math functions as __pure2 unconditionally.  But maybe
> we can't do this anyway, because math functions normally have the
> side effect of setting IEEE exception flags.  Can we do things like
> double sqrt(double);
> #else
> double sqrt(double) __pure2;
> #endif
> ?

I don't know.  I forgot about the libm PR until last
week when someone else posted about paranoi.c failing
several tests.  I decided to check into the quality
of libm and work on improvements.  I still have a lot to

I think we'll only be able to add __pure2 on a case 
by case basis.  For example, the POSIX sqrt(3) manpage states 

   An application wishing to check for error situations should set
   errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling
   these functions.  On return, if errno is non-zero or
   is non-zero, an error has occurred.

> > Also, are functions missing in libm with respect to the
> > C99 standard?  I would be willing to work on implementing
> > these functions.
> Most are missing, if you count long double and complex support.  Only
> a few are, for double support.  I noticed some easy ones like
> isnormal() when I scanned the C99 draft standard today to check the
> status if infnan.3.

Garrett pointed me to the Open Group's docs.  I didn't know
the docs were available on-line.  Complex functions are
confined to complex.h.  I suppose we need to implement 
complex.h, but I'll probably concentrate on math.h.


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