| author |  Robbie Lyman <rb.lymn@gmail.com> 2026-08-03 14:35:39-04:00 |
| committer |  Andrew Kelley <andrew@ziglang.org> 2026-08-05 02:55:26+02:00 |
| log | ce96dcceab7731f63534425f1d25bfe9be014847 |
| tree | ee6bc33a44874fcca256632c8edbbae170b2c6a8 |
| parent | 9688e6e6208910b3e8dce5a6b93ea743fd46a575 |
fix(Io.Dispatch): node = .{}, mutex deinit, wrong canceled
In most of the file `node: std.DoublyLinkedList.Node` is
default-initialized as `.{}` rather than `undefined`. I don't believe
this resolves any crashes for me, but it seems incorrect.
If `backing_allocator_needs_mutex` is `true` and the backing allocator
has been used nontrivially; for example in creating a `Group`, the
current `Dispatch.deinit()` code segfaults. Since the error also goes away
when `backing_allocator_needs_mutex` is false, I believe remembering to
call `deinit()` on the mutex is the fix.
Canceling a sleep call currently crashes because of a soundness issue:
The `@fieldParentPtr` type punning in `SleepWaiter.canceled` cannot be
replaced by `Futex.Waiter.canceled`. For me, the failure winds up being in
`waiter.remove()` meeting a node whose `prev` field is mostly `0xaa`,
which made this one a real pain to fix.1 files changed, 3 insertions(+), 2 deletions(-)
lib- std
lib/std/Io/Dispatch.zig+3-2
| ... | ... | @@ -580,6 +580,7 @@ pub fn deinit(ev: *Evented) void { |
| 580 | 580 | ev.stderr_mutex.deinit(); |
| 581 | 581 | for (&ev.futexes) |*futex| futex.deinit(); |
| 582 | 582 | ev.exit_semaphore.as_object().release(); |
| 583 | ev.backing_allocator_mutex.deinit(); | |
| 583 | 584 | ev.backing_allocator.free(ev.main_loop_stack[0..main_loop_stack_size]); |
| 584 | 585 | ev.queue.as_object().release(); |
| 585 | 586 | } |
| ... | ... | @@ -825,7 +826,7 @@ const Mutex = struct { |
| 825 | 826 | sleeper: Sleeper = undefined, |
| 826 | 827 | cancelable: Cancelable, |
| 827 | 828 | mutex: *Mutex, |
| 828 | node: std.DoublyLinkedList.Node = undefined, | |
| 829 | node: std.DoublyLinkedList.Node = .{}, | |
| 829 | 830 | |
| 830 | 831 | fn add(context: ?*anyopaque) callconv(.c) void { |
| 831 | 832 | const waiter: *Waiter = @ptrCast(@alignCast(context)); |
| ... | ... | @@ -4714,7 +4715,7 @@ fn sleep(userdata: ?*anyopaque, timeout: Io.Timeout) Io.Cancelable!void { |
| 4714 | 4715 | return ev.yield(.{ .after = ev.timeFromTimeout(timeout) }); |
| 4715 | 4716 | }; |
| 4716 | 4717 | var waiter: SleepWaiter = .{ |
| 4717 | .cancelable = .{ .queue = queue, .cancel = &Futex.Waiter.canceled }, | |
| 4718 | .cancelable = .{ .queue = queue, .cancel = &SleepWaiter.canceled }, | |
| 4718 | 4719 | .timer = timer, |
| 4719 | 4720 | }; |
| 4720 | 4721 | timer.as_object().set_context(&waiter); |