add missing Send + 'static bounds to EventWatchCallback and AudioCallback to avoid soundness hole (#1509)

* add Sync + Send bounds to EventWatchCallback to avoid soundness hole

* add 'static bounds to EventWatchCallback

* update changelog

* add 'static to AudioCallback too

* remove unnecessary Sync bounds on EventWatchCallback and lifetime param on EventWatch

* fix formatting

* update changelog to reflect AudioCallback change

Author: yonzebu

changelog.md

@@ -3,6 +3,8 @@ when upgrading from a version of rust-sdl2 to another.
 
 ### v0.39.0
 
+[PR #1509](https://github.com/Rust-SDL2/rust-sdl2/pull/1509) **BREAKING CHANGE** Add Send + 'static bounds for EventWatchCallback and 'static bound to AudioCallback to avoid soundness hole.
+
 [PR #1506](https://github.com/Rust-SDL2/rust-sdl2/pull/1506) **BREAKING CHANGE** Update crates.io dependencies, update bundled SDL2 to 2.32.10, add whitelist to bindgen to only emit SDL related items, and specifically no platform (or compiler, etc) specific items. Implement the same set of useful derived traits on bitflags types.
 
 ### v0.38.0

src/sdl2/audio.rs

@@ -512,7 +512,7 @@ impl Drop for AudioSpecWAV {
     }
 }
 
-pub trait AudioCallback: Send
+pub trait AudioCallback: Send + 'static
 where
     Self::Channel: AudioFormatNum + 'static,
 {

src/sdl2/event.rs

@@ -246,10 +246,7 @@ impl crate::EventSubsystem {
     ///     dbg!(event);
     /// });
     /// ```
-    pub fn add_event_watch<'a, CB: EventWatchCallback + 'a>(
-        &self,
-        callback: CB,
-    ) -> EventWatch<'a, CB> {
+    pub fn add_event_watch<CB: EventWatchCallback>(&self, callback: CB) -> EventWatch<CB> {
         EventWatch::add(callback)
     }
 }
@@ -2955,26 +2952,24 @@ impl EventSender {
 }
 
 /// A callback trait for [`EventSubsystem::add_event_watch`].
-pub trait EventWatchCallback {
+pub trait EventWatchCallback: Send + 'static {
     fn callback(&mut self, event: Event);
 }
 
 /// An handler for the event watch callback.
 /// One must bind this struct in a variable as long as you want to keep the callback active.
 /// For further information, see [`EventSubsystem::add_event_watch`].
-pub struct EventWatch<'a, CB: EventWatchCallback + 'a> {
+pub struct EventWatch<CB: EventWatchCallback> {
     activated: bool,
     callback: Box<CB>,
-    _phantom: PhantomData<&'a CB>,
 }
 
-impl<'a, CB: EventWatchCallback + 'a> EventWatch<'a, CB> {
-    fn add(callback: CB) -> EventWatch<'a, CB> {
+impl<CB: EventWatchCallback> EventWatch<CB> {
+    fn add(callback: CB) -> EventWatch<CB> {
         let f = Box::new(callback);
         let mut watch = EventWatch {
             activated: false,
             callback: f,
-            _phantom: PhantomData,
         };
         watch.activate();
         watch
@@ -3021,7 +3016,7 @@ impl<'a, CB: EventWatchCallback + 'a> EventWatch<'a, CB> {
     }
 }
 
-impl<'a, CB: EventWatchCallback + 'a> Drop for EventWatch<'a, CB> {
+impl<CB: EventWatchCallback> Drop for EventWatch<CB> {
     fn drop(&mut self) {
         self.deactivate();
     }
@@ -3037,7 +3032,7 @@ extern "C" fn event_callback_marshall<CB: EventWatchCallback>(
     0
 }
 
-impl<F: FnMut(Event)> EventWatchCallback for F {
+impl<F: FnMut(Event) + Send + 'static> EventWatchCallback for F {
     fn callback(&mut self, event: Event) {
         self(event)
     }