[Cython] CEP1000: Native dispatch through callables

[mark florisson]

On 13 April 2012 13:48, Stefan Behnel <stefan_ml at behnel.de> wrote:
> Stefan Behnel, 13.04.2012 14:27:
>> Dag Sverre Seljebotn, 13.04.2012 13:59:
>>> Requiring interning is somewhat less elegant in one way, but it makes a lot
>>> of other stuff much simpler.
>>>
>>> That gives us
>>>
>>> struct {
>>>     void *pointer;
>>>     PyBytesObject *signature;
>>> } record;
>>>
>>> and then you allocate a NULL-terminated arrays of these for all the overloads.
>>
>> However, the problem is the setup. These references will have to be created
>> at init time and discarded during runtime termination. Not a problem for
>> Cython generated code, but some overhead for hand written code.
>>
>> Since the size of these structs is not a problem, I'd prefer keeping Python
>> objects out of the game and using an ssize_t ID instead, inferred from a
>> char* signature at module init time by calling a C-API function. That
>> avoids the need for any cleanup.
>
> Actually, we could even use interned char* values. Nothing keeps that C-API
> setup function from reassigning the "char* signature" field to the char*
> buffer of an internally allocated byte string. Except that we'd have to
> *require* users to use literals or otherwise statically allocated C strings
> in that field. Hmm, maybe not the best idea ever...
>
> Stefan
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You could create a module shared by all versions and projects, which
exposes a function 'get_signature', which given a char *signature
returns the pointer that should be used in the ABI signature type
information. You can then always compare by identity.