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py: Fix bug in map lookup of interned string vs non-interned.
Had choice of either interning or forcing full equality comparison, and chose latter. See comments in mp_map_lookup. Addresses issue #523.
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py/map.c
24
py/map.c
@ -98,13 +98,33 @@ STATIC void mp_map_rehash(mp_map_t *map) {
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// MP_MAP_LOOKUP_REMOVE_IF_FOUND behaviour:
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// - returns NULL if not found, else the slot if was found in with key null and value non-null
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mp_map_elem_t* mp_map_lookup(mp_map_t *map, mp_obj_t index, mp_map_lookup_kind_t lookup_kind) {
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// Work out if we can compare just pointers
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bool compare_only_ptrs = map->all_keys_are_qstrs;
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if (compare_only_ptrs) {
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if (MP_OBJ_IS_QSTR(index)) {
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// Index is a qstr, so can just do ptr comparison.
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} else if (MP_OBJ_IS_TYPE(index, &mp_type_str)) {
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// Index is a non-interned string.
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// We can either intern the string, or force a full equality comparison.
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// We chose the latter, since interning costs time and potentially RAM,
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// and it won't necessarily benefit subsequent calls because these calls
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// most likely won't pass the newly-interned string.
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compare_only_ptrs = false;
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} else if (!(lookup_kind & MP_MAP_LOOKUP_ADD_IF_NOT_FOUND)) {
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// If we are not adding, then we can return straight away a failed
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// lookup because we know that the index will never be found.
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return NULL;
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}
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}
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// if the map is a fixed array then we must do a brute force linear search
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if (map->table_is_fixed_array) {
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if (lookup_kind != MP_MAP_LOOKUP) {
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return NULL;
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}
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for (mp_map_elem_t *elem = &map->table[0], *top = &map->table[map->used]; elem < top; elem++) {
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if (elem->key == index || (!map->all_keys_are_qstrs && mp_obj_equal(elem->key, index))) {
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if (elem->key == index || (!compare_only_ptrs && mp_obj_equal(elem->key, index))) {
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return elem;
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}
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}
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@ -148,7 +168,7 @@ mp_map_elem_t* mp_map_lookup(mp_map_t *map, mp_obj_t index, mp_map_lookup_kind_t
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if (avail_slot == NULL) {
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avail_slot = slot;
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}
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} else if (slot->key == index || (!map->all_keys_are_qstrs && mp_obj_equal(slot->key, index))) {
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} else if (slot->key == index || (!compare_only_ptrs && mp_obj_equal(slot->key, index))) {
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// found index
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// Note: CPython does not replace the index; try x={True:'true'};x[1]='one';x
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if (lookup_kind & MP_MAP_LOOKUP_REMOVE_IF_FOUND) {
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15
tests/basics/dict-intern.py
Normal file
15
tests/basics/dict-intern.py
Normal file
@ -0,0 +1,15 @@
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# check that interned strings are compared against non-interned strings
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di = {"key1": "value"}
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# lookup interned string
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k = "key1"
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print(k in di)
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# lookup non-interned string
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k2 = "key" + "1"
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print(k == k2)
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print(k2 in di)
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# lookup non-interned string
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print("".join(['k', 'e', 'y', '1']) in di)
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