portmaster-tauri-tao-patch

Patched copy of tauri-apps/tao 0.32.8, the windowing library of the Tauri UI framework, used by the Portmaster desktop UI on Windows.

This is a temporary fix for a reference-count race that crashes the Portmaster UI. It is not a maintained fork and is only needed until an upstream release contains a fix.

The upstream README is kept as README.upstream.md.

Why this exists

Portmaster issues:

• safing/portmaster#2185 (v2.1.19)
• safing/portmaster#2255 (v2.2.3)

Symptom: portmaster.exe (the Tauri UI process) dies randomly on Windows with Illegal instruction (0xc000001d), often preceded by STATUS_HEAP_CORRUPTION (0xc0000374).

Mechanism: tauri_runtime_wry::Context derives Clone and contains tao's EventLoopWindowTarget. On Windows that struct holds the event-loop runner behind Rc<EventLoopRunner>, a plain non-atomic reference count. Tauri clones Context on every AppHandle, Window or Webview clone, from any thread. Two threads cloning at the same instant lose an update, the runner is freed while still in use, and the next clone aborts.

Upstream tracking:

• Issue: tauri-apps/tauri#15408
• Tauri-side fix (open): tauri-apps/tauri#15411
• tao-side fix, same change as here (closed unmerged): tauri-apps#1334

What is changed

Branch portmaster/windows-atomic-refcount-0.32.8 is upstream tag tao-v0.32.8 plus our commits: the code change and this documentation. The authoritative list of changes is the diff against the tag:

https://github.com/safing/portmaster-tauri-tao-patch/compare/tao-v0.32.8...portmaster/windows-atomic-refcount-0.32.8

Code changes, all marked with // PORTMASTER PATCH comments:

File	Change
src/platform_impl/windows/event_loop/runner.rs	type EventLoopRunnerShared<T> = Rc<EventLoopRunner<T>> becomes Arc<...>; import rc::Rc becomes sync::Arc
src/platform_impl/windows/event_loop.rs	Rc::new(EventLoopRunner::new(..)) becomes Arc::new(..); unused rc::Rc import removed
src/lib.rs	adds pub const PORTMASTER_PATCH_LEVEL: u32 = 1; (marker, see below)

Only the reference count becomes atomic. The runner keeps its Cell and RefCell interior and stays non-Send and non-Sync. Nothing else in tao is touched. Linux and macOS code paths are unchanged.

version in Cargo.toml stays 0.32.8 on purpose: Cargo only accepts a [patch] whose version matches the one in the consumer's lock file.

How Portmaster uses it

In desktop/tauri/src-tauri/Cargo.toml, pinned to a commit so the built code cannot change under a force push:

[patch.crates-io]
tao = { git = "https://github.com/safing/portmaster-tauri-tao-patch", rev = "<commit>" }

Portmaster also asserts the marker constant at compile time, reached through tauri_runtime_wry::tao so it is guaranteed to be the tao that Tauri compiles against:

const _: () = assert!(tauri_runtime_wry::tao::PORTMASTER_PATCH_LEVEL == 1);

If a dependency update makes Cargo drop the patch, the constant disappears and the Portmaster build fails instead of silently shipping the unpatched crate.

Is this patch still needed?

1. Check whether tauri-apps/tauri#15411 or an equivalent change is in a released tauri-runtime-wry or tao: https://v2.tauri.app/release/tauri-runtime-wry/all-versions/, https://v2.tauri.app/release/tao/all-versions/.
2. Practical test in the Portmaster repository: remove the [patch.crates-io] entry and the marker assertion, build the debug UI with cargo build --profile dev (Cargo re-resolves tao from crates.io by itself) and start it with the command-line flag --verify-tao-patch. The debug build contains a stress test that clones the app handle from four threads. An unpatched tao crashes within seconds; a fixed one keeps logging still alive lines. The guard, the stress hook and the full description live in desktop/tauri/src-tauri/src/windows_tao_patch.rs in the Portmaster repository.

Making a patch branch for a newer tao

Needed when Portmaster upgrades Tauri and the new Tauri requires a newer tao, while upstream still has no fix. The idea: start from the new upstream release tag and put our commits (the code change and this documentation) on top of it. The example uses tao 0.37.1; replace the version with the one Tauri needs.

1. Get the upstream release tag into this repository. The fork does not track upstream tags, so fetch the one tag explicitly (--no-tags keeps all other upstream tags out).

   git remote add upstream https://github.com/tauri-apps/tao.git   # once per clone
   git fetch upstream tag tao-v0.37.1 --no-tags

2. Create the new patch branch from that tag.

   git checkout -b portmaster/windows-atomic-refcount-0.37.1 tao-v0.37.1

3. Copy the patch commits from the previous patch branch onto it. The previous branch is its upstream tag plus our commits, so the range "everything after the old tag up to the old branch" is exactly those commits, no hashes needed:

   git cherry-pick tao-v0.32.8..portmaster/windows-atomic-refcount-0.32.8

   If the cherry-pick reports a conflict, the upstream lines moved; apply the change by hand (it is two lines, see "What is changed") and continue with git cherry-pick --continue.

4. Check that it compiles for Windows, then tag the result.

   cargo check
   git tag tao-v0.37.1-portmaster.1

5. Push three things in one go: the branch, our new tag, and the upstream release tag. The upstream tag is pushed because the fork does not have it otherwise, and GitHub's compare view against it needs it.

   git push origin portmaster/windows-atomic-refcount-0.37.1 tao-v0.37.1-portmaster.1 tao-v0.37.1

6. On GitHub, set the new branch as the default branch so this README stays the one visitors see. In Portmaster, point [patch.crates-io] at the new commit.

Bump PORTMASTER_PATCH_LEVEL (here and in Portmaster's guard) only if the patch content itself changes, not for a plain re-base.

When upstream ships the fix

Portmaster drops the [patch] entry, the marker assertion and the windows_tao_patch.rs module, and upgrades to the fixed Tauri release. Portmaster commits made before that keep referencing this repository at a pinned commit.

License

tao is licensed under Apache-2.0 (see LICENSE). The changes in this repository are published under the same license.