Build fails when #define LV_USE_OS LV_OS_PTHREAD

[ThomasFarstrike]

When changing LV_USE_OS from LV_OS_NONE to LV_OS_PTHREAD in lib/lv_conf.h to enable lv.lock() - lv_lock(), the build fails:

build-standard/lv_mpy.c:21533:61: error: incompatible type for argument 1 of ‘mp_obj_new_int’
21533 |             case MP_QSTR_lock: dest[0] = mp_obj_new_int(data->lock); break; // converting from lv_mutex_t;
|                                                         ~~~~^~~~~~
|                                                             |
|                                                             lv_mutex_t {aka pthread_mutex_t}
In file included from build-standard/lv_mpy.c:20:
../../py/obj.h:974:34: note: expected ‘mp_int_t’ {aka ‘long int’} but argument is of type ‘lv_mutex_t’ {aka ‘pthread_mutex_t’}
974 | mp_obj_t mp_obj_new_int(mp_int_t value);
|                         ~~~~~~~~~^~~~~
build-standard/lv_mpy.c:21548:49: error: incompatible types when assigning to type ‘lv_mutex_t’ {aka ‘pthread_mutex_t’} from type ‘int’
21548 |                 case MP_QSTR_lock: data->lock = (int)mp_obj_get_int(dest[1]); break; // converting to lv_mutex_t;
|                                                 ^
build-standard/lv_mpy.c: In function ‘mp_lv_thread_sync_t_attr’:
build-standard/lv_mpy.c:23880:62: error: incompatible type for argument 1 of ‘mp_obj_new_int’
23880 |             case MP_QSTR_mutex: dest[0] = mp_obj_new_int(data->mutex); break; // converting from pthread_mutex_t;
|                                                          ~~~~^~~~~~~
|                                                              |
|                                                              pthread_mutex_t
../../py/obj.h:974:34: note: expected ‘mp_int_t’ {aka ‘long int’} but argument is of type ‘pthread_mutex_t’
974 | mp_obj_t mp_obj_new_int(mp_int_t value);
|                         ~~~~~~~~~^~~~~
build-standard/lv_mpy.c:23881:61: error: incompatible type for argument 1 of ‘mp_obj_new_int’
23881 |             case MP_QSTR_cond: dest[0] = mp_obj_new_int(data->cond); break; // converting from pthread_cond_t;
|                                                         ~~~~^~~~~~
|                                                             |
|                                                             pthread_cond_t
../../py/obj.h:974:34: note: expected ‘mp_int_t’ {aka ‘long int’} but argument is of type ‘pthread_cond_t’
974 | mp_obj_t mp_obj_new_int(mp_int_t value);
|                         ~~~~~~~~~^~~~~
build-standard/lv_mpy.c:23891:51: error: incompatible types when assigning to type ‘pthread_mutex_t’ from type ‘int’
23891 |                 case MP_QSTR_mutex: data->mutex = (int)mp_obj_get_int(dest[1]); break; // converting to pthread_mutex_t;
|                                                   ^
build-standard/lv_mpy.c:23892:49: error: incompatible types when assigning to type ‘pthread_cond_t’ from type ‘int’
23892 |                 case MP_QSTR_cond: data->cond = (int)mp_obj_get_int(dest[1]); break; // converting to pthread_cond_t;
|                                                 ^

I suspect it just needs a bit of magic sprinkled into python_api_gen_mpy.py but after taking a look, I didn't see it...

[kdschlosser]

the code generation script is not written to handle external specific types like pthread_cond_t and pthread_mutex_t It has no clue what those types are or how to handle them.

if you wanted to try it and see if you can get it to work you can edit the code generator script and add special handling for the pthread types and instead of casting them to an integer you would create a python object using MP_OBJ_FROM_PTR and MP_OBJ_TO_PTR. the C code would look something along the lines of...

the getter code would end up looking like this..

mp_lv_struct_t *container= m_new_obj(mp_lv_struct_t);
container->data = &data->cond;
case MP_QSTR_cond: dest[0] = MP_OBJ_FROM_PTR(container); break; // converting from pthread_cond_t;

and the setter code would end up looking like this...

mp_lv_struct_t *container= MP_OBJ_TO_PTR(dest[1]);
case MP_QSTR_cond: data->cond = (pthread_cond_t)*container->data; break; // converting to pthread_cond_t;

the reason why this happens is because the code generator script uses a "fake" libc collection in order to convert properly. This is done because of the nested nature of libc and if it was used it would be pulling in all kinds of types that would end up having code generated for it.

technically speaking you really don't need to have access to those thread structures. so what can be done is the LVGL header file where the declarations are coming from can be ignored entirely or you can try tweaking the types for pthread_cond_t and pthread_mutex_t in the fake libc header files.

try this...

in the code generator script add the following code at line 100..

class FileAST(c_ast.Node):

    def __init__(self, ext, coord=None):

        for obj in ext[:]:
            if hasattr(obj, 'coord'):
                if obj.coord and obj.coord.file.endswith('lv_pthread.h'):
                    ext.remove(obj)
        
        self.ext = ext
        self.coord = coord

and then add the following at line 165

setattr(c_ast, 'FileAST', FileAST)

that should fix the error.