[Cython] C int division by zero

[Robert Bradshaw]

On Apr 14, 2009, at 9:17 AM, Dag Sverre Seljebotn wrote:

> I was just thinking about this:
>
>      cdef int a = 10, b = 0
>      print a // b
>
> which currently gives a C exception terminating the Python  
> interpreter.
>
> On one hand: We have already changed division to Python behaviour  
> (with
> a speed penalty); so using the same arguments (which I won't  
> reiterate)
> it would make sense to raise a Python exception instead here.
>
> It seems to make sense to couple this as well to the cdivision  
> directive
> and cython.cdiv function.
>
> On the other hand: Well, all the arguments that was against  
> changing //
> to Python behaviour.

Since we changed it, we should chang it all the way. It will be  
somewhat uglier as this means when writing a / (c-c) one needs to  
store the denominator in a temp and check it rather than simply  
letting the expression through to C (I already did this for warnings).

> But in addition:
>
> This is coupled with the "exception under nogil" issue that I  
> raised in
> another thread today, as one should definitely be allowed to do C
> division within a nogil section.
>
> One solution would be to work on accepting exceptions under nogil,
> another one would be to require use of cdivision directive/cdiv to do
> division in nogil sections.

I don't think exceptions are safe without the gil. With cdivision on  
it won't raise anything.

- Robert