extmod/ure: Fix msvc warning resulting from memset on const char ** pointer

extmod/modure.c

@@ -101,7 +101,8 @@ STATIC mp_obj_t re_exec(bool is_anchored, uint n_args, const mp_obj_t *args) {
     subj.end = subj.begin + len;
     int caps_num = (self->re.sub + 1) * 2;
     mp_obj_match_t *match = m_new_obj_var(mp_obj_match_t, char*, caps_num);
-    memset(match->caps, 0, caps_num * sizeof(char*));
+    // cast is a workaround for a bug in msvc: it treats const char** as a const pointer instead of a pointer to pointer to const char
+    memset((char*)match->caps, 0, caps_num * sizeof(char*));
     int res = re1_5_recursiveloopprog(&self->re, &subj, match->caps, caps_num, is_anchored);
     if (res == 0) {
         m_del_var(mp_obj_match_t, char*, caps_num, match);
@@ -140,7 +141,8 @@ STATIC mp_obj_t re_split(uint n_args, const mp_obj_t *args) {
     mp_obj_t retval = mp_obj_new_list(0, NULL);
     const char **caps = alloca(caps_num * sizeof(char*));
     while (true) {
-        memset(caps, 0, caps_num * sizeof(char*));
+        // cast is a workaround for a bug in msvc: it treats const char** as a const pointer instead of a pointer to pointer to const char
+        memset((char**)caps, 0, caps_num * sizeof(char*));
         int res = re1_5_recursiveloopprog(&self->re, &subj, caps, caps_num, false);
 
         // if we didn't have a match, or had an empty match, it's time to stop