Jan,

Whow! You seem to have *serious* knowledge about this stuff. I'm impressed.

> For a store, a variety of exceptions are listed in the Intel processor
> manual (which is available as PDF from Intel's site).

I got pretty much all the manuals from Intel's site that are available. Can
you give me a reference to the appropriate section?! (just in case you know
which one to search ;-)

> In theory yes, unfortunatly there may be a LOT of DLL's 
> loaded into your process automagically. One of those DLL 
> may have a control path that changes the FP mode and returns 
> without setting it back, like when some error happens. 
> The behaivor is YOUR FP code blows up 15 minutes later
> because the FP exception is no longer masked. Serious FP code 
> will often turn exception handling back on, otherwise you have to check 
> for NaN's in every result value, even in cases where everything ran just
fine.

Hm ... how about extending the (already existing) exception handler to
handle floating point exceptions by masking the exceptions again and resume
as usual?! Do you know if FPU exceptions are always resumable?!

> >I've read about this but do you know how to find out if MMX mode is
> >currently active?!
> 
> The FP tag word has a 2-bit field for each FP/MMX register. I 
> believe the MSVC debugger will show the FP tag register if 
> you open the register window. A value of FFFF means the FP 
> registers are empty, 0000 means all full, and MAY indicate 
> a missing EMMS instruction after MMX code (a MMX
> instruction set's the tag register to 0000).

Guess we should be able to extend the exception handler to handle these
problems as well, shouldn't we?!

  Andreas