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bors merged 1 commit into from
Aug 27, 2024
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exit: explain our expectations for the exit handlers registered in a Rust program #129581

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9 changes: 9 additions & 0 deletions library/std/src/process.rs
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Expand Up @@ -2296,6 +2296,15 @@ impl Child {
/// }
/// ```
///
/// In its current implementation, this function will execute exit handlers registered with `atexit`
/// as well as other platform-specific exit handlers (e.g. `fini` sections of ELF shared objects).
/// This means that Rust requires that all exit handlers are safe to execute at any time. In
/// particular, if an exit handler cleans up some state that might be concurrently accessed by other
/// threads, it is required that the exit handler performs suitable synchronization with those
/// threads. (The alternative to this requirement would be to not run exit handlers at all, which is
/// considered undesirable. Note that returning from `main` also calls `exit`, so making `exit` an
/// unsafe operation is not an option.)

@RalfJung RalfJung Aug 25, 2024

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@comex sketched an approach a Rust library could take when wrapping a C library with a problematic destructor, to still uphold this requirement. I don't know what the conclusion was regarding whether this would actually work, and I am not sure if it's worth spelling that out in these docs -- this seems more like something to go into some book on Rust FFI advice.

///
/// ## Platform-specific behavior
///
/// **Unix**: On Unix-like platforms, it is unlikely that all 32 bits of `exit`
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