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Fix std.HashMap.remove returning incorrect KV

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Now returns a copy of the removed kv instead of a pointer to the removed kv. The removed kv gets overwritten when shifting the hash map after the removal, so returning a pointer to it will have another kv's values in it after the return.

This bug had some nasty downstream effects in things like BufSet and BufMap where delete would free a still in-use KV and leave the actually removed KV un-free'd.
This commit is contained in:
Ryan Liptak 2019-04-06 14:15:12 -07:00 committed by Andrew Kelley
parent 6715c54cc6
commit 6a78b315b2
1 changed files with 7 additions and 3 deletions
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10
std/hash_map.zig
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@ -175,7 +175,7 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
return hm.get(key) != null; return hm.get(key) != null;
} }
pub fn remove(hm: *Self, key: K) ?*KV { pub fn remove(hm: *Self, key: K) ?KV {
if (hm.entries.len == 0) return null; if (hm.entries.len == 0) return null;
hm.incrementModificationCount(); hm.incrementModificationCount();
const start_index = hm.keyToIndex(key); const start_index = hm.keyToIndex(key);
@ -189,13 +189,14 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
if (!eql(entry.kv.key, key)) continue; if (!eql(entry.kv.key, key)) continue;
const removed_kv = entry.kv;
while (roll_over < hm.entries.len) : (roll_over += 1) { while (roll_over < hm.entries.len) : (roll_over += 1) {
const next_index = (start_index + roll_over + 1) % hm.entries.len; const next_index = (start_index + roll_over + 1) % hm.entries.len;
const next_entry = &hm.entries[next_index]; const next_entry = &hm.entries[next_index];
if (!next_entry.used or next_entry.distance_from_start_index == 0) { if (!next_entry.used or next_entry.distance_from_start_index == 0) {
entry.used = false; entry.used = false;
hm.size -= 1; hm.size -= 1;
return &entry.kv; return removed_kv;
} }
entry.* = next_entry.*; entry.* = next_entry.*;
entry.distance_from_start_index -= 1; entry.distance_from_start_index -= 1;
@ -371,7 +372,10 @@ test "basic hash map usage" {
testing.expect(map.contains(2)); testing.expect(map.contains(2));
testing.expect(map.get(2).?.value == 22); testing.expect(map.get(2).?.value == 22);
_ = map.remove(2);
const rmv1 = map.remove(2);
testing.expect(rmv1.?.key == 2);
testing.expect(rmv1.?.value == 22);
testing.expect(map.remove(2) == null); testing.expect(map.remove(2) == null);
testing.expect(map.get(2) == null); testing.expect(map.get(2) == null);
} }