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Removed UnwindSafe bounds

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After thinking about this more and more, I've come to realize that
forcing UnwindSafe is not the intention of the bound on catch_unwind.
This should have been evident to me by the fact that thread::spawn does
not require UnwindSafe, yet it catches panics. The key qualifier I wasn't
noticing was that the design of the trait is to prevent *easily*
observing invariant states.

Since this panic catch results in dropping and then subsequently closing
everything that was passed to it, it fits the same general shape as
thread::spawn, so I'm removing the bounds.
This commit is contained in:
Jonathan Johnson 2023-12-20 08:50:21 -08:00
parent ebcff2bb4f
commit de899cf546
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1 changed files with 9 additions and 5 deletions
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14
src/window.rs
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@ -1,6 +1,6 @@
use std::collections::HashSet; use std::collections::HashSet;
use std::ops::{Deref, DerefMut}; use std::ops::{Deref, DerefMut};
use std::panic::{AssertUnwindSafe, UnwindSafe}; use std::panic::AssertUnwindSafe;
use std::path::PathBuf; use std::path::PathBuf;
use std::sync::{mpsc, Arc}; use std::sync::{mpsc, Arc};
use std::thread; use std::thread;
@ -405,6 +405,12 @@ where
{ {
let proxy = self.app.proxy.clone(); let proxy = self.app.proxy.clone();
let window_id = self.window.id(); let window_id = self.window.id();
// We assert unwind safety here due to internal types on some platforms
// in winit use dyn trait objects that do not specify unwind safety.
// However, in this situation we are not recovering the window itself.
// The panic will cause us to ask winit to close the window. There is no
// recovery for a panic inside of a window, the only question is whether
// the entire app panics or not.
let possible_panic = std::panic::catch_unwind(AssertUnwindSafe(move || { let possible_panic = std::panic::catch_unwind(AssertUnwindSafe(move || {
let mut behavior = Behavior::initialize(&mut self, context); let mut behavior = Behavior::initialize(&mut self, context);
while !self.close && self.process_messages_until_redraw(&mut behavior) { while !self.close && self.process_messages_until_redraw(&mut behavior) {
@ -417,7 +423,6 @@ where
// chance to be freed. // chance to be freed.
})); }));
//
if let Err(panic) = possible_panic { if let Err(panic) = possible_panic {
let _result = proxy.send_event(EventLoopMessage::WindowPanic(window_id)); let _result = proxy.send_event(EventLoopMessage::WindowPanic(window_id));
std::panic::resume_unwind(panic) std::panic::resume_unwind(panic)
@ -743,7 +748,7 @@ enum TimeUntilRedraw {
/// consumers of the libraries. This trait provides functions for each of the /// consumers of the libraries. This trait provides functions for each of the
/// events a window may receive, enabling the type to react and update its /// events a window may receive, enabling the type to react and update its
/// state. /// state.
pub trait WindowBehavior<AppMessage>: UnwindSafe + Sized + 'static pub trait WindowBehavior<AppMessage>: Sized + 'static
where where
AppMessage: Message, AppMessage: Message,
{ {
@ -751,8 +756,7 @@ where
/// ///
/// This allows providing data to the window from the thread that is opening /// This allows providing data to the window from the thread that is opening
/// the window without requiring that `WindowBehavior` also be `Send`. /// the window without requiring that `WindowBehavior` also be `Send`.
type Context: Send + UnwindSafe; type Context: Send;
/// Returns a new window builder for this behavior. When the window is /// Returns a new window builder for this behavior. When the window is
/// initialized, a default [`Context`](Self::Context) will be passed. /// initialized, a default [`Context`](Self::Context) will be passed.
fn build<App>(app: &App) -> WindowBuilder<'_, Self, App, AppMessage> fn build<App>(app: &App) -> WindowBuilder<'_, Self, App, AppMessage>