Re: GCC withdraw

On Sun, Aug 25, 2013 at 11:08:57AM +0100, David Chisnall wrote:
> On 25 Aug 2013, at 00:06, Steve Kargl <sgk_at_troutmask.apl.washington.edu> wrote:
> 
> > On Sat, Aug 24, 2013 at 11:44:38PM +0100, David Chisnall wrote:
> >> On 24 Aug 2013, at 23:42, Slawa Olhovchenkov <slw_at_zxy.spb.ru> wrote:
> >> 
> >>> And i found PR about clang and mplayer: ports/176272
> >>> This PR contains log with build error log.
> >> 
> >> Please file clang bugs at http://llvm.org/bugs/
> >> 
> > 
> > As if this is going to help.
> > 
> > http://llvm.org/bugs/show_bug.cgi?id=8532
> > 
> > 2 years, 9 month and counting.
> 
> This bug relates to a corner case in complex floating point support,
> which GCC in base doesn't get right either,

GCC addressed issue in 4.5.0.  I don't necessarily agree with
the fix, but gcc did not ignore it.  I understand why FreeBSD has 
not updated to a newer gcc base.

> and which affects a tiny proportion of users

yep, anyone using complex arithmetic.

> and which comes with a hypothetical test case

Of course, it is a trivial testcase.  It was meant to be trivial to
demonstrate the bug and aid the compiler writer in fixing it.

> but no evidence that any real-world code is affected by it.

http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/147599

> If you have some real-world code that is compiled correctly
> by GCC but incorrectly by clang as a result of this, then
> please update the bug.

Go read FreeBSD libm's code where I (and now others) had/have
to jump through hoops with cpack[f|l] functions to avoid the 
problem.  

> Oh, and it's worth noting that clang, as an extension, supports
> using initialiser lists to create complex values and so this
> particular case is trivial to avoid if you use this feature,
> which you will if you create complex numbers using the macro that
> the C specification introduced specifically to avoid this case.  

See msun/src/math_private.h.  

But, the above is irrelevant.  You missed my point, so to
be blunt.  Reporting the bug to llvm does not mean that it
will be fixed.  More importantly the problem with mplayer
and clang should be reported/recorded in FreeBSD's bug
database where others can find the issue when clang fails
to build mplayer.  The mplayer maintainer can either 
fix the problem or escaluate the issue upstream.

-- 
Steve