Rollup of 7 pull requests #92934
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Rollup of 7 pull requests #92934
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And to remove possibility of panics while changing the panic handler, because that resulted in a double panic.
Useful for thin wrapper attributes that are best passed as value instead of reference.
includes minor refactorings
Implement `panic::update_hook`
Add a new function `panic::update_hook` to allow creating panic hooks that forward the call to the previously set panic hook, without race conditions. It works by taking a closure that transforms the old panic hook into a new one, while ensuring that during the execution of the closure no other thread can modify the panic hook. This is a small function so I hope it can be discussed here without a formal RFC, however if you prefer I can write one.
Consider the following example:
```rust
let prev = panic::take_hook();
panic::set_hook(Box::new(move |info| {
println!("panic handler A");
prev(info);
}));
```
This is a common pattern in libraries that need to do something in case of panic: log panic to a file, record code coverage, send panic message to a monitoring service, print custom message with link to github to open a new issue, etc. However it is impossible to avoid race conditions with the current API, because two threads can execute in this order:
* Thread A calls `panic::take_hook()`
* Thread B calls `panic::take_hook()`
* Thread A calls `panic::set_hook()`
* Thread B calls `panic::set_hook()`
And the result is that the original panic hook has been lost, as well as the panic hook set by thread A. The resulting panic hook will be the one set by thread B, which forwards to the default panic hook. This is not considered a big issue because the panic handler setup is usually run during initialization code, probably before spawning any other threads.
Using the new `panic::update_hook` function, this race condition is impossible, and the result will be either `A, B, original` or `B, A, original`.
```rust
panic::update_hook(|prev| {
Box::new(move |info| {
println!("panic handler A");
prev(info);
})
});
```
I found one real world use case here: https://github.com/dtolnay/proc-macro2/blob/988cf403e741aadfd5340bbf67e35e1062a526aa/src/detection.rs#L32 the workaround is to detect the race condition and panic in that case.
The pattern of `take_hook` + `set_hook` is very common, you can see some examples in this pull request, so I think it's natural to have a function that combines them both. Also using `update_hook` instead of `take_hook` + `set_hook` reduces the number of calls to `HOOK_LOCK.write()` from 2 to 1, but I don't expect this to make any difference in performance.
### Unresolved questions:
* `panic::update_hook` takes a closure, if that closure panics the error message is "panicked while processing panic" which is not nice. This is a consequence of holding the `HOOK_LOCK` while executing the closure. Could be avoided using `catch_unwind`?
* Reimplement `panic::set_hook` as `panic::update_hook(|_prev| hook)`?
feat: rustc_pass_by_value lint attribute Useful for thin wrapper attributes that are best passed as value instead of reference. Fixes rust-lang#76935
…cs, r=camelid rustdoc: fix intra-link for generic trait impls fixes rust-lang#92662 r? ````@camelid````
…ron1011 Remove some unnecessary uses of `FieldDef::ident` Followup from rust-lang#92533. cc ````@Aaron1011```` ````@petrochenkov````
remove unused FIXME rust-lang#56935 seems to be fixed.
rustdoc: remove hand-rolled isatty This PR replaces bindings to the platform-specific isatty APIs with the `isatty` crate, as done elsewhere in the repository.
Move expr- and item-related pretty printing functions to modules Currently *compiler/rustc_ast_pretty/src/pprust/state.rs* is 2976 lines on master. The `tidy` limit is 3000, which is blocking rust-lang#92243. This PR adds a `mod expr;` and `mod item;` to move logic related to those AST nodes out of the single huge file.
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@bors r+ rollup=never p=7 |
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📌 Commit b289c7c has been approved by |
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⌛ Testing commit b289c7c with merge 7210d1cdb5fa7b645cb35ce6174c73dd5bca5acb... |
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The job Click to see the possible cause of the failure (guessed by this bot) |
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💔 Test failed - checks-actions |
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Looks like a spurious failure, same as in #91288 (comment) |
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Successful merges:
panic::update_hook#92598 (Implementpanic::update_hook)FieldDef::ident#92799 (Remove some unnecessary uses ofFieldDef::ident)Failed merges:
r? @ghost
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