Rollup of 7 pull requests #83119
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Rollup of 7 pull requests #83119
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Background: Over the last year, pidfd support was added to the Linux kernel. This allows interacting with other processes. In particular, this allows waiting on a child process with a timeout in a race-free way, bypassing all of the awful signal-handler tricks that are usually required. Pidfds can be obtained for a child process (as well as any other process) via the `pidfd_open` syscall. Unfortunately, this requires several conditions to hold in order to be race-free (i.e. the pid is not reused). Per `man pidfd_open`: ``` · the disposition of SIGCHLD has not been explicitly set to SIG_IGN (see sigaction(2)); · the SA_NOCLDWAIT flag was not specified while establishing a han‐ dler for SIGCHLD or while setting the disposition of that signal to SIG_DFL (see sigaction(2)); and · the zombie process was not reaped elsewhere in the program (e.g., either by an asynchronously executed signal handler or by wait(2) or similar in another thread). If any of these conditions does not hold, then the child process (along with a PID file descriptor that refers to it) should instead be created using clone(2) with the CLONE_PIDFD flag. ``` Sadly, these conditions are impossible to guarantee once any libraries are used. For example, C code runnng in a different thread could call `wait()`, which is impossible to detect from Rust code trying to open a pidfd. While pid reuse issues should (hopefully) be rare in practice, we can do better. By passing the `CLONE_PIDFD` flag to `clone()` or `clone3()`, we can obtain a pidfd for the child process in a guaranteed race-free manner. This PR: This PR adds Linux-specific process extension methods to allow obtaining pidfds for processes spawned via the standard `Command` API. Other than being made available to user code, the standard library does not make use of these pidfds in any way. In particular, the implementation of `Child::wait` is completely unchanged. Two Linux-specific helper methods are added: `CommandExt::create_pidfd` and `ChildExt::pidfd`. These methods are intended to serve as a building block for libraries to build higher-level abstractions - in particular, waiting on a process with a timeout. I've included a basic test, which verifies that pidfds are created iff the `create_pidfd` method is used. This test is somewhat special - it should always succeed on systems with the `clone3` system call available, and always fail on systems without `clone3` available. I'm not sure how to best ensure this programatically. This PR relies on the newer `clone3` system call to pass the `CLONE_FD`, rather than the older `clone` system call. `clone3` was added to Linux in the same release as pidfds, so this shouldn't unnecessarily limit the kernel versions that this code supports. Unresolved questions: * What should the name of the feature gate be for these newly added methods? * Should the `pidfd` method distinguish between an error occurring and `create_pidfd` not being called?
Improve docs
Merges `if-let` and `if x.is_some() { ... }` blocks
Add Linux-specific pidfd process extensions (take 2) Continuation of rust-lang#77168. I addressed the following concerns from the original PR: - make `CommandExt` and `ChildExt` sealed traits - wrap file descriptors in `PidFd` struct representing ownership over the fd - add `take_pidfd` to take the fd out of `Child` - close fd when dropped Tracking Issue: rust-lang#82971
expand: Resolve and expand inner attributes on out-of-line modules Fixes rust-lang#81661 r? `@Aaron1011`
…ange, r=davidtwco
Validate rustc_layout_scalar_valid_range_{start,end} attributes
Fixes rust-lang#82251, rust-lang#82981.
…avidtwco Improve the wording for the `can't reassign` error Follow-up for rust-lang#71976 (comment). Fixes rust-lang#66736
More precise spans for HIR paths `Ty::assoc_item` is lowered to `<Ty>::assoc_item` in HIR, but `Ty` got span from the whole path. This PR fixes that, and adjusts some diagnostic code that relied on `Ty` having the whole path span. This is a pre-requisite for rust-lang#82868 (we cannot report suggestions like `Tr::assoc` -> `<dyn Tr>::assoc` with the current imprecise spans). r? `@estebank`
Fix typos in `library/core/src/ptr/mod.rs` and `library/std/src/sys_common/thread_local_dtor.rs` adress -> address
…as-schievink
Minor refactoring in try_index_step
Merges `if-let` and `if x.is_some() { ... }` blocks
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Successful merges:
can't reassignerror #83062 (Improve the wording for thecan't reassignerror)library/core/src/ptr/mod.rsandlibrary/std/src/sys_common/thread_local_dtor.rs#83110 (Fix typos inlibrary/core/src/ptr/mod.rsandlibrary/std/src/sys_common/thread_local_dtor.rs)Failed merges:
r? @ghost
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