py/obj: Introduce mp_obj_malloc macro to allocate, and set object type.

This is to replace the following:

    mp_foo_obj_t *self = m_new_obj(mp_foo_obj_t);
    self->base.type = &mp_type_foo;

with:

    mp_foo_obj_t *self = mp_obj_malloc(mp_foo_obj_t, &mp_type_foo);

Calling the function is less code than inlining setting the type
everywhere, adds up to ~100 bytes on PYBV11.

It also helps to avoid an easy mistake of forgetting to set the type.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

py/dynruntime.h

@@ -126,6 +126,8 @@ static inline void *m_realloc_dyn(void *ptr, size_t new_num_bytes) {
 #define mp_obj_get_array(o, len, items)     (mp_obj_get_array_dyn((o), (len), (items)))
 #define mp_obj_list_append(list, item)      (mp_fun_table.list_append((list), (item)))
 
+#define mp_obj_malloc_helper(n, t)          (mp_obj_malloc_helper_dyn(n, t))
+
 static inline mp_obj_t mp_obj_new_str_of_type_dyn(const mp_obj_type_t *type, const byte *data, size_t len) {
     if (type == &mp_type_str) {
         return mp_obj_new_str((const char *)data, len);
@@ -163,6 +165,12 @@ static inline mp_obj_t mp_obj_len_dyn(mp_obj_t o) {
     return mp_fun_table.call_function_n_kw(mp_fun_table.load_name(MP_QSTR_len), 1, &o);
 }
 
+static inline void *mp_obj_malloc_helper_dyn(size_t num_bytes, const mp_obj_type_t *type) {
+    mp_obj_base_t *base = (mp_obj_base_t *)m_malloc(num_bytes);
+    base->type = type;
+    return base;
+}
+
 /******************************************************************************/
 // General runtime functions
 

py/obj.c

@@ -37,6 +37,13 @@
 #include "py/stackctrl.h"
 #include "py/stream.h" // for mp_obj_print
 
+// Allocates an object and also sets type, for mp_obj_malloc{,_var} macros.
+void *mp_obj_malloc_helper(size_t num_bytes, const mp_obj_type_t *type) {
+    mp_obj_base_t *base = (mp_obj_base_t *)m_malloc(num_bytes);
+    base->type = type;
+    return base;
+}
+
 const mp_obj_type_t *MICROPY_WRAP_MP_OBJ_GET_TYPE(mp_obj_get_type)(mp_const_obj_t o_in) {
     #if MICROPY_OBJ_IMMEDIATE_OBJS && MICROPY_OBJ_REPR == MICROPY_OBJ_REPR_A
 

py/obj.h

@@ -732,6 +732,12 @@ extern const struct _mp_obj_exception_t mp_const_GeneratorExit_obj;
 
 // General API for objects
 
+// Helper versions of m_new_obj when you need to immediately set base.type.
+// Implementing this as a call rather than inline saves 8 bytes per usage.
+#define mp_obj_malloc(struct_type, obj_type) ((struct_type *)mp_obj_malloc_helper(sizeof(struct_type), obj_type))
+#define mp_obj_malloc_var(struct_type, var_type, var_num, obj_type) ((struct_type *)mp_obj_malloc_helper(sizeof(struct_type) + sizeof(var_type) * (var_num), obj_type))
+void *mp_obj_malloc_helper(size_t num_bytes, const mp_obj_type_t *type);
+
 // These macros are derived from more primitive ones and are used to
 // check for more specific object types.
 // Note: these are kept as macros because inline functions sometimes use much