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Code Issues 1 Releases Wiki Activity

Fix undefined behavior (integer overflow) in hash function.

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If an intermediate hash value was 0xFFFFFFFF and we tried to add 1 as a
signed addition, this technically triggers undefined behavior.
This commit is contained in:
Calvin Rose
2025-11-16 08:14:19 -06:00
parent f7d0d065c8
commit b389f01005
1 changed files with 2 additions and 1 deletions
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src/core/value.c
+2 -1
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@@ -322,7 +322,8 @@ int32_t janet_hash(Janet x) {
break;
case JANET_TUPLE:
hash = janet_tuple_hash(janet_unwrap_tuple(x));
hash += (janet_tuple_flag(janet_unwrap_tuple(x)) & JANET_TUPLE_FLAG_BRACKETCTOR) ? 1 : 0;
uint32_t inc = (janet_tuple_flag(janet_unwrap_tuple(x)) & JANET_TUPLE_FLAG_BRACKETCTOR) ? 1 : 0;
hash = (int32_t)((uint32_t)hash + inc); /* avoid overflow undefined behavior */
break;
case JANET_STRUCT:
hash = janet_struct_hash(janet_unwrap_struct(x));