[Cython] 'local variable referenced before assignment' warnings

Vitja Makarov vitja.makarov at gmail.com
Fri Sep 23 06:36:45 CEST 2011

2011/9/23 Robert Bradshaw <robertwb at math.washington.edu>:
> On Thu, Sep 22, 2011 at 5:08 AM, Vitja Makarov <vitja.makarov at gmail.com> wrote:
>> 2011/9/22 Robert Bradshaw <robertwb at math.washington.edu>:
>>> On Wed, Sep 21, 2011 at 1:20 AM,  <robert.rex at exasol.com> wrote:
>>>> Hi Robert,
>>>> Robert Bradshaw wrote:
>>>>> The warning seem correct to me, or is foo actually modifying the
>>>>> values of cya and cyb? (I suppose this could be possible by taking the
>>>>> address of the "passed by reference" arguments, but would seem like a
>>>>> *very* poor API design.)
>>>> thanks for your fast answer! What made me came up with this issue is
>>>> that GCC/C++ will not complain in similar situations in C++ code (and
>>>> assumes foo() to initialize/change the value of cya/cyb). Thus, there
>>>> is an (arguable) difference in C++ compiler/Cython warnings.
>>> Yes, in C++ the called function can modify values passed by reference,
>>> so we need to add this exception to Cython.
>> That could be hard because we can not always resolve function to check
>> its args at create-control-flow stage.
> Doesn't this always happen after declaration analysis?

Sure. But before analyse expressions, so you have to manually lookup
entries for names and attributes.

I see two cases here: global function call and method call. Both are


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