Related to https://github.com/cython/cython/issues/3343
One issue with the current code generated for fastcall function is that
for a function like:
def f(a, *args, **kwds):
# something...
the wrapper function immediately generates a tuple for `args` and a dict
for `kwds`, which presumably misses most of the benefits of the more
efficient calling method. It therefore seems like a good idea to have an
optional optimization so that the more efficient representation can be
used (close to) directly.
I've created an initial attempt at it
https://github.com/cython/cython/pull/3346. This defines a complier
directive so that:
@cython.fastcall_args("*" or "**" or "both")
def function...
is converted to a relatively simple structure type. The tuple equivalent is
typedef struct {
PyObject *const *args;
Py_ssize_t nargs;
} __Pyx_FastcallTuple_obj;
and the dict equivalent a little more complicated is
typedef struct {
PyObject *const *args; // start of the keyword args values
PyObject *object; // either a dict, a tuple or NULL
} __Pyx_FastcallDict_obj;
// exists in one of three states:
// * args is NULL, "object" is NULL, meaning no keyword arguments
// * args is NULL, in which case "object" is actually a dict, and this
just defers to the dict methods
// * args is non-null, kwnames is a tuple
These then support simple operations (indexing, iterating, passing
directly to a fastcall function call etc). For most non-simple
operations they will just be coerced to a Python object with a warning
(but trying to put them in a closure will explicitly fail).
-------------------------------------
I suspect my proposed code is still a bit of a mess, so I'm not looking
for too much scrutiny of that right now. What I'm interested in is:
* is the syntax to use this sensible? (it's probably easily changed)
* is the level of warnings appropriate?
* any operations that I've missed that'd be sensible to support?
* anything else?
David
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