Antoine Pitrou wrote:
> Stefan Behnel <stefan_ml <at> behnel.de> writes:
>> BTW, I noticed that the code in typeobject.c uses "DECREF before set" two
>> times, like this:
>>
>> method_cache[h].version = type->tp_version_tag;
>> method_cache[h].value = res; /* borrowed */
>> Py_INCREF(name);
>> Py_DECREF(method_cache[h].name);
>> method_cache[h].name = name;
>
> Since this is so common, would it be useful to define a macro for the correct
> construct?
>
> Something like
>
> #define Py_SETREF(var, obj) \
> { PyObject *tmp = (var); Py_INCREF(obj); \
> (var) = (obj); Py_XDECREF(tmp); }
>
> Or, if we want to allow more optimizations, make two versions of it:
>
> #define Py_SETREF(var, obj) \
> { PyObject *tmp = (var); Py_INCREF(obj); \
> (var) = (obj); Py_DECREF(tmp); }
>
> #define Py_XSETREF(var, obj) \
> { PyObject *tmp = (var); Py_INCREF(obj); \
> (var) = (obj); Py_XDECREF(tmp); }
Both sound like a good idea to me. Having to think about whether or not DECREF
poses a problem in a specific case is just cumbersome.
Stefan
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