Re: [Rd] make check of R-alpha_2006-04-08_r37675 fails: qbeta

From: Prof Brian Ripley <>
Date: Fri 14 Apr 2006 - 17:47:28 GMT

On Fri, 14 Apr 2006, Peter Dalgaard wrote:

> Prof Brian Ripley <> writes:
>> Uwe Ligges had the same problem with gcc 3.3.1 on SuSE 9.0. So I
>> installed gcc 3.3.5 from the sources on an i386 box, and was able to
>> reproduce it.
>> It is an optimization bug. The crucial code is
>> xtrunc = tx; /* this prevents trouble with excess FPU */
>> /* precision on some machines. */
>> if (xtrunc == xinbta)
>> goto L_converged;
>> and both xtrunc and xinbta are volatile. Seems that is being ignored
>> in 3.3.5/1, and so the loop never terminates.
>> Using an explicit check is safer and faster. I'll put mine in once I
>> have finished testing.
> However, if the compiler is disobeying "volatile", it is buggy and it
> might be safer not to use that compiler at all. There's no telling
> what else might break for the same reason.

I agree, and in my earlier reply suggested we write this off but given we now have two reports I can see many more after release. It is a known bug in gcc 3.3.x, and so far nothing else has come to light. (This only came to light because the warning had previously been suppressed.)

I would advise against systems as old as SuSE 9.0 or many grounds, but some people may have no choice.


Brian D. Ripley,        
Professor of Applied Statistics,
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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