various: Work around a few of the clang ubsan diagnostics.

These fixes do not make me proud.

Signed-off-by: Jeff Epler <jepler@gmail.com>

py/bc.c

@@ -147,7 +147,7 @@ static void mp_setup_code_state_helper(mp_code_state_t *code_state, size_t n_arg
     // zero out the local stack to begin with
     memset(code_state_state, 0, n_state * sizeof(*code_state->state));
 
-    const mp_obj_t *kwargs = args + n_args;
+    const mp_obj_t *kwargs = args ? args + n_args : NULL;
 
     // var_pos_kw_args points to the stack where the var-args tuple, and var-kw dict, should go (if they are needed)
     mp_obj_t *var_pos_kw_args = &code_state_state[n_state - 1 - n_pos_args - n_kwonly_args];

py/lexer.c

@@ -910,7 +910,8 @@ mp_lexer_t *mp_lexer_new_from_fd(qstr filename, int fd, bool close_fd) {
 
 #endif
 
-void mp_lexer_free(mp_lexer_t *lex) {
+void mp_lexer_free(void *lex_in) {
+    mp_lexer_t *lex = lex_in;
     if (lex) {
         lex->reader.close(lex->reader.data);
         vstr_clear(&lex->vstr);

py/lexer.h

@@ -198,7 +198,7 @@ mp_lexer_t *mp_lexer_new_from_file(qstr filename);
 mp_lexer_t *mp_lexer_new_from_fd(qstr filename, int fd, bool close_fd);
 #endif
 
-void mp_lexer_free(mp_lexer_t *lex);
+void mp_lexer_free(void *lex);
 void mp_lexer_to_next(mp_lexer_t *lex);
 
 #endif // MICROPY_INCLUDED_PY_LEXER_H

py/map.c

@@ -190,6 +190,7 @@ mp_map_elem_t *MICROPY_WRAP_MP_MAP_LOOKUP(mp_map_lookup)(mp_map_t * map, mp_obj_
 
     // if the map is an ordered array then we must do a brute force linear search
     if (map->is_ordered) {
+        if (map->used) {
             for (mp_map_elem_t *elem = &map->table[0], *top = &map->table[map->used]; elem < top; elem++) {
                 if (elem->key == index || (!compare_only_ptrs && mp_obj_equal(elem->key, index))) {
                     #if MICROPY_PY_COLLECTIONS_ORDEREDDICT
@@ -209,6 +210,7 @@ mp_map_elem_t *MICROPY_WRAP_MP_MAP_LOOKUP(mp_map_lookup)(mp_map_t * map, mp_obj_
                     return elem;
                 }
             }
+        }
         #if MICROPY_PY_COLLECTIONS_ORDEREDDICT
         if (MP_LIKELY(lookup_kind != MP_MAP_LOOKUP_ADD_IF_NOT_FOUND)) {
             return NULL;

py/misc.h

@@ -214,7 +214,7 @@ char *vstr_null_terminated_str(vstr_t *vstr);
 void vstr_add_byte(vstr_t *vstr, byte v);
 void vstr_add_char(vstr_t *vstr, unichar chr);
 void vstr_add_str(vstr_t *vstr, const char *str);
-void vstr_add_strn(vstr_t *vstr, const char *str, size_t len);
+void vstr_add_strn(void *vstr, const char *str, size_t len);
 void vstr_ins_byte(vstr_t *vstr, size_t byte_pos, byte b);
 void vstr_ins_char(vstr_t *vstr, size_t char_pos, unichar chr);
 void vstr_cut_head_bytes(vstr_t *vstr, size_t bytes_to_cut);

py/vm.c

@@ -75,7 +75,7 @@
     } while (0)
 
 #define DECODE_SLABEL \
-    size_t slab; \
+    int slab; \
     do { \
         if (ip[0] & 0x80) { \
             slab = ((ip[0] & 0x7f) | (ip[1] << 7)) - 0x4000; \
@@ -792,7 +792,7 @@ unwind_jump:;
                     if (*(sp - MP_OBJ_ITER_BUF_NSLOTS + 1) == MP_OBJ_NULL) {
                         obj = *(sp - MP_OBJ_ITER_BUF_NSLOTS + 2);
                     } else {
-                        obj = MP_OBJ_FROM_PTR(&sp[-MP_OBJ_ITER_BUF_NSLOTS + 1]);
+                        obj = MP_OBJ_FROM_PTR(sp - MP_OBJ_ITER_BUF_NSLOTS + 1);
                     }
                     mp_obj_t value = mp_iternext_allow_raise(obj);
                     if (value == MP_OBJ_STOP_ITERATION) {
@@ -821,7 +821,7 @@ unwind_jump:;
                 ENTRY(MP_BC_BUILD_TUPLE): {
                     MARK_EXC_IP_SELECTIVE();
                     DECODE_UINT;
-                    sp -= unum - 1;
+                    sp = sp - unum + 1;
                     SET_TOP(mp_obj_new_tuple(unum, sp));
                     DISPATCH();
                 }
@@ -829,7 +829,7 @@ unwind_jump:;
                 ENTRY(MP_BC_BUILD_LIST): {
                     MARK_EXC_IP_SELECTIVE();
                     DECODE_UINT;
-                    sp -= unum - 1;
+                    sp = sp - unum + 1;
                     SET_TOP(mp_obj_new_list(unum, sp));
                     DISPATCH();
                 }

py/vstr.c

@@ -177,7 +177,9 @@ void vstr_add_str(vstr_t *vstr, const char *str) {
     vstr_add_strn(vstr, str, strlen(str));
 }
 
-void vstr_add_strn(vstr_t *vstr, const char *str, size_t len) {
+// The first parameter is declared as `void*` so that it can be used as a `print_strn` function.
+void vstr_add_strn(void *vstr_in, const char *str, size_t len) {
+    vstr_t *vstr = vstr_in;
     vstr_ensure_extra(vstr, len);
     memmove(vstr->buf + vstr->len, str, len);
     vstr->len += len;