[fpc-pascal] EControlC instead of EZeroDivide when using SSE instructions

[OBones]

Jonas Maebe wrote:
>
> OBones wrote on Wed, 22 Aug 2012:
>
>> Jonas Maebe wrote:
>>>
>>> You can try debugging syswin32_i386_exception_handler in 
>>> rtl/win32/system.pp to see what exception Win32 reports instead.
>> Thanks for the confirmation as I was heading that way when I posted 
>> the message, without much hope.
>> But now that I have put that idea to full length, it became clear 
>> that the problem is not (entirely) with Win32 but because the 
>> exception handler does not handle the STATUS_FLOAT_MULTIPLE_FAULTS 
>> and STATUS_FLOAT_MULTIPLE_TRAPS cases.
>
> I guess you mean "a division by zero using an SSE instruction results 
> in STATUS_FLOAT_MULTIPLE_FAULTS and/or STATUS_FLOAT_MULTIPLE_TRAPS"?
Yes, that's it, sorry for not making it clearer.

>> And as you said, when it does not know what to do, it gives 217 that 
>> gets later translated to Control C, which to me is a bit misleading. 
>> I'd rather have a 202, External Exception.
>
> 202 is "stack overflow". 217 is also used in the RTL as "unhandled 
> exception". I don't know how come that this code is used both for 
> ctrl-c and unhandled exception. Probably a simple error from a long 
> time ago that never got corrected.
Woops, typo, I meant 212, as can be found in RunErrorToExcept from 
sysutils.inc. That's where the Control C is coming from by the way.


>> So right, now, using this I'm getting the appropriate exception, I'm 
>> just left wondering if this code (or a similar one) should be added 
>> to FreePascal so that other people are not having the same issue as 
>> I'm having.
>
> Probably. At least a quick web search seems to indicate this is a 
> fairly well-known problem with SSE exceptions and Win32.
Well, once one knows about the multiple traps/multiple faults, yes, it's 
easy to find it. But when starting from just a control C, it's much more 
complex.

Once again, thanks for your help.

Olivier