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#![doc( test(attr(deny(warnings))), test(attr(allow(bare_trait_objects, unknown_lints))) )] #![allow( unknown_lints, renamed_and_removed_lints, intra_doc_link_resolution_failure, broken_itra_doc_links )] //! Library for easier and safe Unix signal handling //! //! Unix signals are inherently hard to handle correctly, for several reasons: //! //! * They are a global resource. If a library wants to set its own signal handlers, it risks //! disturbing some other library. It is possible to chain the previous signal handler, but then //! it is impossible to remove the old signal handlers from the chains in any practical manner. //! * They can be called from whatever thread, requiring synchronization. Also, as they can //! interrupt a thread at any time, making most handling race-prone. //! * According to the POSIX standard, the set of functions one may call inside a signal handler is //! limited to very few of them. To highlight, mutexes (or other locking mechanisms) and memory //! allocation and deallocation is *not* allowed. //! //! This library aims to solve some of the problems. It provides a global registry of actions //! performed on arrival of signals. It is possible to register multiple actions for the same //! signal and it is possible to remove the actions later on. If there was a previous signal //! handler when the first action for a signal is registered, it is chained (but the original one //! can't be removed). //! //! The main function of the library is [`register`](fn.register.html). //! //! It also offers several common actions one might want to register, implemented in the correct //! way. They are scattered through submodules and have the same limitations and characteristics as //! the [`register`](fn.register.html) function. Generally, they work to postpone the action taken //! outside of the signal handler, where the full freedom and power of rust is available. //! //! Unlike other Rust libraries for signal handling, this should be flexible enough to handle all //! the common and useful patterns. //! //! The library avoids all the newer fancy signal-handling routines. These generally have two //! downsides: //! //! * They are not fully portable, therefore the library would have to contain *both* the //! implementation using the basic routines and the fancy ones. As signal handling is not on the //! hot path of most programs, this would not bring any actual benefit. //! * The other routines require that the given signal is masked in all application's threads. As //! the signals are not masked by default and a new thread inherits the signal mask of its //! parent, it is possible to guarantee such global mask by masking them before any threads //! start. While this is possible for an application developer to do, it is not possible for a //! a library. //! //! # Warning //! //! Even with this library, you should thread with care. It does not eliminate all the problems //! mentioned above. //! //! Also, note that the OS may collate multiple instances of the same signal into just one call of //! the signal handler. Furthermore, some abstractions implemented here also naturally collate //! multiple instances of the same signal. The general guarantee is, if there was at least one //! signal of the given number delivered, an action will be taken, but it is not specified how many //! times ‒ signals work mostly as kind of „wake up now“ nudge, if the application is slow to wake //! up, it may be nudged multiple times before it does so. //! //! # Signal limitations //! //! OS limits still apply ‒ it is not possible to redefine certain signals (eg. `SIGKILL` or //! `SIGSTOP`) and it is probably a *very* stupid idea to touch certain other ones (`SIGSEGV`, //! `SIGFPE`, `SIGILL`). Therefore, this library will panic if any attempt at manipulating these is //! made. There are some use cases for redefining the latter ones, but these are not well served by //! this library and you really *really* have to know what you're doing and are generally on your //! own doing that. //! //! # Signal masks //! //! As the library uses `sigaction` under the hood, signal masking works as expected (eg. with //! `pthread_sigmask`). This means, signals will *not* be delivered if the signal is masked in all //! program's threads. //! //! By the way, if you do want to modify the signal mask (or do other Unix-specific magic), the //! [nix](https://crates.io/crates/nix) crate offers safe interface to many low-level functions, //! including //! [`pthread_sigmask`](https://docs.rs/nix/0.11.0/nix/sys/signal/fn.pthread_sigmask.html). //! //! # Portability //! //! It should work on any POSIX.1-2001 system, which are all the major big OSes with the notable //! exception of Windows. //! //! Non-standard signals are also supported. Pass the signal value directly from `libc` or use //! the numeric value directly. //! //! ```rust //! use std::sync::Arc; //! use std::sync::atomic::{AtomicBool}; //! let term = Arc::new(AtomicBool::new(false)); //! let _ = signal_hook::flag::register(libc::SIGINT, Arc::clone(&term)); //! ``` //! //! This crate includes a limited support for Windows, based on `signal`/`raise` in the CRT. //! There are differences in both API and behavior: //! //! - `iterator` and `pipe` are not yet implemented. //! - We have only a few signals: `SIGABRT`, `SIGABRT_COMPAT`, `SIGBREAK`, //! `SIGFPE`, `SIGILL`, `SIGINT`, `SIGSEGV` and `SIGTERM`. //! - Due to lack of signal blocking, there's a race condition. //! After the call to `signal`, there's a moment where we miss a signal. //! That means when you register a handler, there may be a signal which invokes //! neither the default handler or the handler you register. //! - Handlers registered by `signal` in Windows are cleared on first signal. //! To match behavior in other platforms, we re-register the handler each time the handler is //! called, but there's a moment where we miss a handler. //! That means when you receive two signals in a row, there may be a signal which invokes //! the default handler, nevertheless you certainly have registered the handler. //! //! Moreover, signals won't work as you expected. `SIGTERM` isn't actually used and //! not all `Ctrl-C`s are turned into `SIGINT`. //! //! Patches to improve Windows support in this library are welcome. //! //! # Examples //! //! ```rust //! extern crate signal_hook; //! //! use std::io::Error; //! use std::sync::Arc; //! use std::sync::atomic::{AtomicBool, Ordering}; //! //! fn main() -> Result<(), Error> { //! let term = Arc::new(AtomicBool::new(false)); //! signal_hook::flag::register(signal_hook::SIGTERM, Arc::clone(&term))?; //! while !term.load(Ordering::Relaxed) { //! // Do some time-limited stuff here //! // (if this could block forever, then there's no guarantee the signal will have any //! // effect). //! # //! # // Hack to terminate the example, not part of the real code. //! # term.store(true, Ordering::Relaxed); //! } //! Ok(()) //! } //! ``` //! //! # Features //! //! * `mio-support`: The [`Signals` iterator](iterator/struct.Signals.html) becomes pluggable into //! mio 0.6. //! * `mio-0_7-support`: The [`Signals` iterator](iterator/struct.Signals.html) becomes pluggable into //! mio 0.7. //! * `tokio-support`: The [`Signals`](iterator/struct.Signals.html) can be turned into //! [`Async`](iterator/struct.Async.html), which provides a `Stream` interface for integration in //! the asynchronous world. #[cfg(feature = "tokio-support")] extern crate futures; extern crate libc; #[cfg(feature = "mio-support")] extern crate mio; #[cfg(any(test, feature = "mio-0_7-support"))] extern crate mio_0_7; extern crate signal_hook_registry; #[cfg(feature = "tokio-support")] extern crate tokio_reactor; pub mod cleanup; pub mod flag; #[cfg(not(windows))] pub mod iterator; #[cfg(not(windows))] pub mod pipe; #[cfg(not(windows))] pub use libc::{ SIGABRT, SIGALRM, SIGBUS, SIGCHLD, SIGCONT, SIGFPE, SIGHUP, SIGILL, SIGINT, SIGIO, SIGKILL, SIGPIPE, SIGPROF, SIGQUIT, SIGSEGV, SIGSTOP, SIGSYS, SIGTERM, SIGTRAP, SIGUSR1, SIGUSR2, SIGWINCH, }; #[cfg(windows)] pub use libc::{SIGABRT, SIGFPE, SIGILL, SIGINT, SIGSEGV, SIGTERM}; // NOTE: they perhaps deserve backport to libc. #[cfg(windows)] /// Same as `SIGABRT`, but the number is compatible to other platforms. pub const SIGABRT_COMPAT: libc::c_int = 6; #[cfg(windows)] /// Ctrl-Break is pressed for Windows Console processes. pub const SIGBREAK: libc::c_int = 21; pub use signal_hook_registry::{register, unregister, SigId, FORBIDDEN};