Re: [glean-dev] catching FP exceptions in C++

[Brian P. <bri...@tu...>]

Allen Akin wrote:
> On Tue, Nov 08, 2005 at 04:08:19PM -0700, Brian Paul wrote:
> | I'm going to be writing a new glean test to see how OpenGL handles 
> | infinite/nan/denorm/etc floating point values.
> 
> You're a braver man than I am. :-)
> 
> | My experience with exception handling in C++ is pretty slim and I'm 
> | not even sure if there's a standard way to handle them.
> 
> I'm not either.  I've checked my printed references and done a few web
> searches, and I haven't found anything that claims to work universally.
> 
> I suspect the most portable thing we could do would be to use the C99
> standard IEEE exception mechanism.  (See "man fetestexcept", etc.)  It
> depends on the ANSI C signal-catching utilities, but nothing
> *nix-specific as far as I can tell.
> 
> However, I don't have any experience with it, so I don't know for sure
> that it'll do the job.

Thanks, Allen.  I wasn't even aware of those functions.

I'm checking in what I have so far.  There's no attempt at trapping 
exceptions yet.

Both Mesa and NVIDIA's driver pass the test in that FP exceptions 
aren't raised by default.  If I enable FP exceptions in Mesa with 
export MESA_DEBUG=FP things blow up as soon as I do this assignment:

285:		v[1][0] = make_signaling_nan();

I guess the various make_*() functions should take a pointer to the 
destination float and store the bit pattern as an integer to avoid 
blowing up in Glean before we even get into OpenGL.

-Brian