How to use a uarray.array object in C?

[TsXor]

There seems to be no present api.

[dlech]

Generally, for any object that implements the buffer protocol (bytes, bytearray, array, etc.), you use mp_get_buffer_raise() to get the underlying C buffer from the object.

[TsXor]

Something is "referenced" in MicroPython if there is live pointer to that object. A live pointer is a pointer that can be found in memory starting at either any one of the root pointers, the stack, or any CPU registers, that points to a GC object. Once a live object is found, all word-aligned pointers in the memory of that object are then tried...and recursively so. (It's very simple! Yes it does mean sometimes you end up marking an object live that isn't, but you never miss anything).

mp_obj_t ptr_pool[0];
mp_obj_new_list(0, ptr_pool);
mp_store_global(MP_QSTR__ptr_pool, MP_OBJ_FROM_PTR(&ptr_pool));

and I put some pointers into ptr_pool with mp_obj_list_append, can this action keeps the data that these pointers point to from being recycled?

[dlech]

In the code you shared, ptr_pool is allocated on the stack instead of from the heap so will no longer be valid after the function where it was allocated exits. Also, it has zero size, so it isn't really allocating anything.

I think what you meant instead is:

mp_obj_t obj_pool = mp_obj_new_list(0, NULL);
mp_store_global(MP_QSTR__obj_pool, obj_pool);

You can also use MP_REGISTER_ROOT_POINTER instead if you have a fixed number of objects to keep track of and don't want to expose the object in the Python globals.

[TsXor]

Something is "referenced" in MicroPython if there is live pointer to that object. A live pointer is a pointer that can be found in memory starting at either any one of the root pointers, the stack, or any CPU registers, that points to a GC object. Once a live object is found, all word-aligned pointers in the memory of that object are then tried...and recursively so. (It's very simple! Yes it does mean sometimes you end up marking an object live that isn't, but you never miss anything).

I thought about it again, can "reference" be simpler, like this:

// globally
# define POOL_INIT_SIZE 64
mp_obj_t ptr_pool = (mp_obj_t)m_malloc(POOL_INIT_SIZE * sizeof(mp_obj_t));

// in init function
mp_store_global(MP_QSTR__ptr_pool, ptr_pool);

// in some functions
ptr_pool[x] = ptr;

When a part of memory can be found starting from a root pointer, it is not target of GC?

void *root_ptr ----> void *ptr1 ----> void *ptr2 ----> ... ----> void *ptrn ---> some memory

[TsXor]

I'm not using MP_REGISTER_ROOT_POINTER because I'm using the lvgl version, and the result of a lookup showed that it lacked py/make_root_pointers.py, which parses this statement.

[jimmo]

I thought about it again, can "reference" be simpler, like this:

Yes. But this is exactly what m_tracked_calloc does, so I'd recommend using that instead.

When a part of memory can be found starting from a root pointer, it is not target of GC?

Yes exactly.

I'm not using MP_REGISTER_ROOT_POINTER because

In that case you should use MICROPY_PORT_ROOT_POINTERS in mpconfigport.h (this was replaced by MP_REGISTER_ROOT_POINTER) or m_tracked_calloc.