py/modthread: Return thread id from start_new_thread().

In CPython, `_thread.start_new_thread()` returns an ID that is the same ID
that is returned by `_thread.get_ident()`.  The current MicroPython
implementation of `_thread.start_new_thread()` always returns `None`.

This modifies the required functions to return a value. The native thread
id is returned since this can be used for interop with other functions, for
example, `pthread_kill()` on *nix. `_thread.get_ident()` is also modified
to return the native thread id so that the values match and avoids the need
for a separate `native_id` attribute.

Fixes issue #12153.

Signed-off-by: David Lechner <david@pybricks.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/py/mpthread.h b/py/mpthread.h
index e611ef4c1..f335cc029 100644
--- a/py/mpthread.h
+++ b/py/mpthread.h
@@ -40,7 +40,8 @@ struct _mp_state_thread_t;
 
 struct _mp_state_thread_t *mp_thread_get_state(void);
 void mp_thread_set_state(struct _mp_state_thread_t *state);
-void mp_thread_create(void *(*entry)(void *), void *arg, size_t *stack_size);
+mp_uint_t mp_thread_create(void *(*entry)(void *), void *arg, size_t *stack_size);
+mp_uint_t mp_thread_get_id(void);
 void mp_thread_start(void);
 void mp_thread_finish(void);
 void mp_thread_mutex_init(mp_thread_mutex_t *mutex);