[Cython] All DEF constants are now unsigned?

[Stefan Behnel]

Stefan Behnel schrieb am 05.09.2015 um 16:01:
> Jeroen Demeyer schrieb am 05.09.2015 um 12:17:
>> I noticed that now unsigned constants like
>>
>> DEF foo = 1
>>
>> become 1U in the C source code.
>>
>> This change (i.e. commit ea6414cd293ba2134c3df5b37b158d8e3db79083) broke
>> Sage. I haven't managed yet to actually isolate why this change broke
>> something.
>>
>> Was this change of 1 to 1U intentional? Why was it done?
> 
> Pretty much intentional, yes. I changed it in response to this bug report:
> 
> http://thread.gmane.org/gmane.comp.python.cython.devel/15774
> 
> The problem with DEF constants is that they are Python values that use
> Python semantics in expressions before they eventually get converted back
> into literals and inserted into the AST. Specifically, they loose any
> literals semantics that they initially had in the source code, including
> any information about literal C integer types that contributed to their
> value, as in this case. Thus, there isn't really a 'correct' way to write
> them out as literals and C might be happy with what we output, or not.
> 
> I guess it might be better to undo this part of the change. Unsigned
> literals are usually not the right way to do it in C, definitely not for
> everything. We could then maybe apply the usual 32/64 bits heuristic to add
> at least L/LL suffixes at need.

Does this look better?

https://github.com/cython/cython/commit/2ac9ffbab1e868137bf33bf025eb7a5c7e4707ce

It now appends the 'U' suffix only to literals that are used in an unsigned
context (e.g. assignment to unsigned variable), and additionally appends
L/LL suffixes for integers that might exceed the int/long limits. That's
just guessing, but it should generally improve the current handling of
literals and DEF expressions.

Stefan