extmod/moduselect: Conditionally compile select().

This adds #if MICROPY_PY_USELECT_SELECT around the uselect.select()
function. According to the docs, this function is only for CPython
compatibility and should not normally be used. So we can disable it
and save a few bytes of flash space where possible.

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

extmod/moduselect.c

@@ -107,6 +107,7 @@ STATIC mp_uint_t poll_map_poll(mp_map_t *poll_map, size_t *rwx_num) {
     return n_ready;
 }
 
+#if MICROPY_PY_USELECT_SELECT
 // select(rlist, wlist, xlist[, timeout])
 STATIC mp_obj_t select_select(size_t n_args, const mp_obj_t *args) {
     // get array data from tuple/list arguments
@@ -173,6 +174,7 @@ STATIC mp_obj_t select_select(size_t n_args, const mp_obj_t *args) {
     }
 }
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_select_select_obj, 3, 4, select_select);
+#endif // MICROPY_PY_USELECT_SELECT
 
 typedef struct _mp_obj_poll_t {
     mp_obj_base_t base;
@@ -355,7 +357,9 @@ MP_DEFINE_CONST_FUN_OBJ_0(mp_select_poll_obj, select_poll);
 
 STATIC const mp_rom_map_elem_t mp_module_select_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_uselect) },
+    #if MICROPY_PY_USELECT_SELECT
     { MP_ROM_QSTR(MP_QSTR_select), MP_ROM_PTR(&mp_select_select_obj) },
+    #endif
     { MP_ROM_QSTR(MP_QSTR_poll), MP_ROM_PTR(&mp_select_poll_obj) },
     { MP_ROM_QSTR(MP_QSTR_POLLIN), MP_ROM_INT(MP_STREAM_POLL_RD) },
     { MP_ROM_QSTR(MP_QSTR_POLLOUT), MP_ROM_INT(MP_STREAM_POLL_WR) },

py/mpconfig.h

@@ -1316,6 +1316,13 @@ typedef double mp_float_t;
 #define MICROPY_PY_USELECT (0)
 #endif
 
+// Whether to enable the select() function in the "uselect" module (baremetal
+// implementation). This is present for compatibility but can be disabled to
+// save space.
+#ifndef MICROPY_PY_USELECT_SELECT
+#define MICROPY_PY_USELECT_SELECT (1)
+#endif
+
 // Whether to provide "utime" module functions implementation
 // in terms of mp_hal_* functions.
 #ifndef MICROPY_PY_UTIME_MP_HAL