Re: [Sbcl-devel] floating point exceptions

[Peter V. E. <pva...@de...>]

On Mon, Jan 28, 2002 at 06:24:56AM +0000, Daniel Barlow wrote:
> William Harold Newman <wil...@ai...> writes:
> 
> > The "No traps are enabled? How can this be?" thing was, in my mind
> > anyway, a known bug. However, I never realized it didn't appear in
> > BUGS. (It's bug 146 now. (EXPT 2.0 -127) doesn't suffice to exercise
> > the bug on x86/OpenBSD., but (EXPT 2.0 123456) does.)
> 
> I note also bug 45 ("a slew of floating point errrors reported by
> Peter Van Eynde").  Peter, do you have the tests that these arose
> from?

IIRC they are results from an older version of ansi-test (part of
clocc).

Please note that some versions of Linux were/are so dumb as to clear the
FPU control word on creating an signal handler, thus nuking your reason
to have the signal.

See: cmucl/src/lisp/x86-arch.c:

void  sigtrap_handler(HANDLER_ARGS)
{
...
#if defined(__linux__) && defined(i386)
  /*
   * Restore the FPU control word, setting the rounding mode to nearest.
   */

  if (contextstruct.fpstate)
    setfpucw(contextstruct.fpstate->cw & ~0xc00);
#endif
...

Maybe something similar is happening?

Groetjes, Peter

-- 
It's logic Jim, but not as we know it. | pva...@de...
"God, root, what is difference?" - Pitr|
"God is more forgiving." - Dave Aronson| http://cvs2.cons.org/~pvaneynd/