Is there any current documentation for "external c modules"?

[poWer4aiX]

I want to add an external C based module and started with the documentation found at MicroPython external C modules. It is good as a starting point but lacks of any in depth documentation. After looking around I found the micropython-usermod’s documentation. Unfortunately, when trying to add a class I realized that this seems to be outdated.

Where to find an up-to-date documentation available related to the external C modules?

[shariltumin]

Unfortunately, there isn't much documentation available.

To get a deeper understanding, you just need to read the code. You may also find the files under "micropython/examples/usercmodule" helpful.

This URL, https://mpy-c-gen.oliverrobson.tech/, may be useful for writing the C stub. I hope these are still accurate.

You might also find my repository, https://github.com/shariltumin/c-module-tutorial-micropython, helpful.

[poWer4aiX]

Thanks for the hints. My main concern is how a add a new class? The stubs generator generates the stubs for functions only, but not for generating members of a class.

According the old Working with class documentation, e.g. you provide the "print" member function like this:

const mp_obj_type_t modcapa_two_pin_capa_sensor_type = {
    { &mp_type_type },
    .name = MP_QSTR_modcapa,
    .print = two_pin_capa_sensor_print,
    .make_new = two_pin_capa_sensor_make_new,
    .locals_dict = (mp_obj_dict_t*)&two_pin_capa_sensor_locals_dict,
};

But the structure of the mp_obj_type_t is changed so that is cannot be compiled:

Compressed data not updated
CC ../../../modules4tf/levelsensor/levelsensor.c
../../../modules4tf/levelsensor/levelsensor.c:63:5: error: unknown field 'print' specified in initializer
     .print = two_pin_capa_sensor_print,
     ^
../../../modules4tf/levelsensor/levelsensor.c:63:5: error: initialization makes integer from pointer without a cast [-Werror]

It looks like that the struct was replaced by the new slot based variant in commit cb0ffdd.

  struct _mp_obj_type_t {
  ...
  // Corresponds to __repr__ and __str__ special methods.
- mp_print_fun_t print;
+ uint8_t slot_index_print;

Is there any good candidate to look into, to derive on how to use this new mechanism?

[Carglglz]

Is there any good candidate to look into, to derive on how to use this new mechanism?

@poWer4aiX check

micropython/extmod/modsocket.c

Line 530 in 5f058e9

static MP_DEFINE_CONST_OBJ_TYPE(

static MP_DEFINE_CONST_OBJ_TYPE(
    socket_type,
    MP_QSTR_socket,
    MP_TYPE_FLAG_NONE,
    make_new, socket_make_new,
    protocol, &socket_stream_p,
    locals_dict, &socket_locals_dict,
    print, socket_print
    );

the new way is using this MP_DENIFE_CONST_OBJ_TYPE macro function 👍🏼

[poWer4aiX]

@Carglglz, perfect, thanks a lot for this hint, could easily adapt my code which is working now.