py: Wrap all obj-ptr conversions in MP_OBJ_TO_PTR/MP_OBJ_FROM_PTR.

This allows the mp_obj_t type to be configured to something other than a
pointer-sized primitive type.

This patch also includes additional changes to allow the code to compile
when sizeof(mp_uint_t) != sizeof(void*), such as using size_t instead of
mp_uint_t, and various casts.

unix/modffi.c

@@ -170,12 +170,12 @@ STATIC mp_obj_t return_ffi_value(ffi_arg val, char type)
 
 STATIC void ffimod_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
     (void)kind;
-    mp_obj_ffimod_t *self = self_in;
+    mp_obj_ffimod_t *self = MP_OBJ_TO_PTR(self_in);
     mp_printf(print, "<ffimod %p>", self->handle);
 }
 
 STATIC mp_obj_t ffimod_close(mp_obj_t self_in) {
-    mp_obj_ffimod_t *self = self_in;
+    mp_obj_ffimod_t *self = MP_OBJ_TO_PTR(self_in);
     dlclose(self->handle);
     return mp_const_none;
 }
@@ -205,12 +205,12 @@ STATIC mp_obj_t make_func(mp_obj_t rettype_in, void *func, mp_obj_t argtypes_in)
         nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "Error in ffi_prep_cif"));
     }
 
-    return o;
+    return MP_OBJ_FROM_PTR(o);
 }
 
 STATIC mp_obj_t ffimod_func(mp_uint_t n_args, const mp_obj_t *args) {
     (void)n_args; // always 4
-    mp_obj_ffimod_t *self = args[0];
+    mp_obj_ffimod_t *self = MP_OBJ_TO_PTR(args[0]);
     const char *symname = mp_obj_str_get_str(args[2]);
 
     void *sym = dlsym(self->handle, symname);
@@ -222,7 +222,7 @@ STATIC mp_obj_t ffimod_func(mp_uint_t n_args, const mp_obj_t *args) {
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(ffimod_func_obj, 4, 4, ffimod_func);
 
 STATIC mp_obj_t mod_ffi_func(mp_obj_t rettype, mp_obj_t addr_in, mp_obj_t argtypes) {
-    void *addr = (void*)mp_obj_int_get_truncated(addr_in);
+    void *addr = (void*)MP_OBJ_TO_PTR(mp_obj_int_get_truncated(addr_in));
     return make_func(rettype, addr, argtypes);
 }
 MP_DEFINE_CONST_FUN_OBJ_3(mod_ffi_func_obj, mod_ffi_func);
@@ -267,12 +267,12 @@ STATIC mp_obj_t mod_ffi_callback(mp_obj_t rettype_in, mp_obj_t func_in, mp_obj_t
         nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "ffi_prep_closure_loc"));
     }
 
-    return o;
+    return MP_OBJ_FROM_PTR(o);
 }
 MP_DEFINE_CONST_FUN_OBJ_3(mod_ffi_callback_obj, mod_ffi_callback);
 
 STATIC mp_obj_t ffimod_var(mp_obj_t self_in, mp_obj_t vartype_in, mp_obj_t symname_in) {
-    mp_obj_ffimod_t *self = self_in;
+    mp_obj_ffimod_t *self = MP_OBJ_TO_PTR(self_in);
     const char *rettype = mp_obj_str_get_str(vartype_in);
     const char *symname = mp_obj_str_get_str(symname_in);
 
@@ -285,12 +285,12 @@ STATIC mp_obj_t ffimod_var(mp_obj_t self_in, mp_obj_t vartype_in, mp_obj_t symna
 
     o->var = sym;
     o->type = *rettype;
-    return o;
+    return MP_OBJ_FROM_PTR(o);
 }
 MP_DEFINE_CONST_FUN_OBJ_3(ffimod_var_obj, ffimod_var);
 
 STATIC mp_obj_t ffimod_addr(mp_obj_t self_in, mp_obj_t symname_in) {
-    mp_obj_ffimod_t *self = self_in;
+    mp_obj_ffimod_t *self = MP_OBJ_TO_PTR(self_in);
     const char *symname = mp_obj_str_get_str(symname_in);
 
     void *sym = dlsym(self->handle, symname);
@@ -315,9 +315,9 @@ STATIC mp_obj_t ffimod_make_new(mp_obj_t type_in, mp_uint_t n_args, mp_uint_t n_
         nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(errno)));
     }
     mp_obj_ffimod_t *o = m_new_obj(mp_obj_ffimod_t);
-    o->base.type = type_in;
+    o->base.type = MP_OBJ_TO_PTR(type_in);
     o->handle = mod;
-    return o;
+    return MP_OBJ_FROM_PTR(o);
 }
 
 STATIC const mp_rom_map_elem_t ffimod_locals_dict_table[] = {
@@ -334,19 +334,19 @@ STATIC const mp_obj_type_t ffimod_type = {
     .name = MP_QSTR_ffimod,
     .print = ffimod_print,
     .make_new = ffimod_make_new,
-    .locals_dict = (mp_obj_t)&ffimod_locals_dict,
+    .locals_dict = (mp_obj_dict_t*)&ffimod_locals_dict,
 };
 
 // FFI function
 
 STATIC void ffifunc_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
     (void)kind;
-    mp_obj_ffifunc_t *self = self_in;
+    mp_obj_ffifunc_t *self = MP_OBJ_TO_PTR(self_in);
     mp_printf(print, "<ffifunc %p>", self->func);
 }
 
 STATIC mp_obj_t ffifunc_call(mp_obj_t self_in, mp_uint_t n_args, mp_uint_t n_kw, const mp_obj_t *args) {
-    mp_obj_ffifunc_t *self = self_in;
+    mp_obj_ffifunc_t *self = MP_OBJ_TO_PTR(self_in);
     assert(n_kw == 0);
     assert(n_args == self->cif.nargs);