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std.hash_map: fetchRemove increment available

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To avoid leaking slots, `fetchRemove` must increment `available` (when the "fetch" succeeds).

Without the `available += 1`, the added test `"std.hash_map repeat fetchRemove"` fails with

    run test std-x86-linux-none-Debug: error: thread 432734 panic: integer overflow
    .../zig/lib/std/hash_map.zig:1365:28: 0x6471d5 in getOrPutAssumeCapacityAdapted__anon_47495 (test)
            self.available -= 1;
                           ^
    .../zig/lib/std/hash_map.zig:1308:62: 0x616950 in getOrPutAssumeCapacityContext (test)
            const result = self.getOrPutAssumeCapacityAdapted(key, ctx);
                                                             ^

Alternatively, `fetchRemove` could call `removeByIndex`, though that would entail calling `header()` twice instead of once.
This commit is contained in:
sentientwaffle 2023-06-09 12:52:36 -07:00 committed by Veikka Tuominen
parent 99fe2a23c0
commit f04e65bc09
1 changed files with 25 additions and 0 deletions
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25
lib/std/hash_map.zig
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@ -1113,6 +1113,7 @@ pub fn HashMapUnmanaged(
old_key.* = undefined;
old_val.* = undefined;
self.size -= 1;
self.available += 1;
return result;
}
@ -2193,3 +2194,27 @@ test "std.hash_map removeByPtr 0 sized key" {
try testing.expect(map.count() == 0);
}
test "std.hash_map repeat fetchRemove" {
var map = AutoHashMapUnmanaged(u64, void){};
defer map.deinit(testing.allocator);
try map.ensureTotalCapacity(testing.allocator, 4);
map.putAssumeCapacity(0, {});
map.putAssumeCapacity(1, {});
map.putAssumeCapacity(2, {});
map.putAssumeCapacity(3, {});
// fetchRemove() should make slots available.
var i: usize = 0;
while (i < 10) : (i += 1) {
try testing.expect(map.fetchRemove(3) != null);
map.putAssumeCapacity(3, {});
}
try testing.expect(map.get(0) != null);
try testing.expect(map.get(1) != null);
try testing.expect(map.get(2) != null);
try testing.expect(map.get(3) != null);
}