[Cython] GCC 4.6 unused-but-set-variable warnings

Vitja Makarov vitja.makarov at gmail.com
Fri Jul 29 10:08:06 CEST 2011

2011/7/29 Stefan Behnel <stefan_ml at behnel.de>:
> Vitja Makarov, 29.07.2011 08:38:
>> 2011/7/29 Vitja Makarov:
>>> 2011/7/29 Stefan Behnel:
>>>> Nikolaus Rath, 13.06.2011 16:59:
>>>>> $ gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall
>>>>> -Wstrict-prototypes -fPIC -I/usr/include/python2.6 -c test.c -o test.o
>>>>> -D_FILE_OFFSET_BITS=64 -I/usr/include/fuse -Werror -Wall -Wextra
>>>>> -Wconversion -Wno-unused-parameter -Wno-sign-conversion
>>>>> -fno-strict-aliasing
>>>>> test.c:
>>>>> test.c:454:13: warning: variable ‘__pyx_v_exc’ set but not used
>>>>> [-Wunused-but-set-variable]
>>>>> test.c:453:13: warning: variable ‘__pyx_v_fn’ set but not used
>>>>> [-Wunused-but-set-variable]
>>>>> test.c:452:13: warning: variable ‘__pyx_v_self’ set but not used
>>>>> [-Wunused-but-set-variable]
>>>> http://trac.cython.org/cython_trac/ticket/704
>>>> I think this is something that the control flow analysis could deal
>>>> with.
>>>> Basically, every parameter that turns out to be unused in the function
>>>> (and
>>>> this most likely only happens with parameters) could be ignored, unless
>>>> it
>>>> requires a type conversion with potential side effects. In that
>>>> (unlikely)
>>>> case, we could still drop the final assignment to the variable itself.
>>> There is entry.cf_unused flag it's set when the whole entry is not used.
>> ((6af313c...)) vitja at vitja-laptop:~/work/cython-vitek$ python
>> cython.py -X warn.unused_arg=True test.pyx
>> warning: test.pyx:2:19: Unused argument 'self'
>> warning: test.pyx:2:25: Unused argument 'fn'
>> warning: test.pyx:2:29: Unused argument 'exc'
> Cool. That's what I expected. :)
> Want to give it a try? The argument unpacking code has traditionally been my
> domain, and it's somewhat complex, but it should still be easy to stick this
> in. Note that there is more than one place where this needs to be handled,
> as the code is structured into different cases based on the type of
> signature.
> Otherwise, I can see if I find a bit of time over the weekend.

I will try to find some time. Btw this issue isn't critical and even
isn't a bug at all.


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