1 //! Panic support in the standard library.
3 #![stable(feature = "std_panic", since = "1.9.0")]
6 use crate::collections;
8 use crate::sync::{Mutex, RwLock};
9 use crate::thread::Result;
12 #[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")]
13 #[allow_internal_unstable(libstd_sys_internals, const_format_args)]
14 #[cfg_attr(not(test), rustc_diagnostic_item = "std_panic_2015_macro")]
15 #[rustc_macro_transparency = "semitransparent"]
16 pub macro panic_2015 {
18 $crate::rt::begin_panic("explicit panic")
20 ($msg:expr $(,)?) => ({
21 $crate::rt::begin_panic($msg)
23 ($fmt:expr, $($arg:tt)+) => ({
24 $crate::rt::begin_panic_fmt(&$crate::const_format_args!($fmt, $($arg)+))
29 #[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")]
30 pub use core::panic::panic_2021;
32 #[stable(feature = "panic_hooks", since = "1.10.0")]
33 pub use crate::panicking::{set_hook, take_hook};
35 #[stable(feature = "panic_hooks", since = "1.10.0")]
36 pub use core::panic::{Location, PanicInfo};
38 #[stable(feature = "catch_unwind", since = "1.9.0")]
39 pub use core::panic::{AssertUnwindSafe, RefUnwindSafe, UnwindSafe};
41 /// Panic the current thread with the given message as the panic payload.
43 /// The message can be of any (`Any + Send`) type, not just strings.
45 /// The message is wrapped in a `Box<'static + Any + Send>`, which can be
46 /// accessed later using [`PanicInfo::payload`].
48 /// See the [`panic!`] macro for more information about panicking.
49 #[stable(feature = "panic_any", since = "1.51.0")]
52 pub fn panic_any<M: 'static + Any + Send>(msg: M) -> ! {
53 crate::panicking::begin_panic(msg);
56 #[stable(feature = "catch_unwind", since = "1.9.0")]
57 impl<T: ?Sized> UnwindSafe for Mutex<T> {}
58 #[stable(feature = "catch_unwind", since = "1.9.0")]
59 impl<T: ?Sized> UnwindSafe for RwLock<T> {}
61 #[stable(feature = "unwind_safe_lock_refs", since = "1.12.0")]
62 impl<T: ?Sized> RefUnwindSafe for Mutex<T> {}
63 #[stable(feature = "unwind_safe_lock_refs", since = "1.12.0")]
64 impl<T: ?Sized> RefUnwindSafe for RwLock<T> {}
66 // https://github.com/rust-lang/rust/issues/62301
67 #[stable(feature = "hashbrown", since = "1.36.0")]
68 impl<K, V, S> UnwindSafe for collections::HashMap<K, V, S>
76 /// Invokes a closure, capturing the cause of an unwinding panic if one occurs.
78 /// This function will return `Ok` with the closure's result if the closure
79 /// does not panic, and will return `Err(cause)` if the closure panics. The
80 /// `cause` returned is the object with which panic was originally invoked.
82 /// It is currently undefined behavior to unwind from Rust code into foreign
83 /// code, so this function is particularly useful when Rust is called from
84 /// another language (normally C). This can run arbitrary Rust code, capturing a
85 /// panic and allowing a graceful handling of the error.
87 /// It is **not** recommended to use this function for a general try/catch
88 /// mechanism. The [`Result`] type is more appropriate to use for functions that
89 /// can fail on a regular basis. Additionally, this function is not guaranteed
90 /// to catch all panics, see the "Notes" section below.
92 /// The closure provided is required to adhere to the [`UnwindSafe`] trait to ensure
93 /// that all captured variables are safe to cross this boundary. The purpose of
94 /// this bound is to encode the concept of [exception safety][rfc] in the type
95 /// system. Most usage of this function should not need to worry about this
96 /// bound as programs are naturally unwind safe without `unsafe` code. If it
97 /// becomes a problem the [`AssertUnwindSafe`] wrapper struct can be used to quickly
98 /// assert that the usage here is indeed unwind safe.
100 /// [rfc]: https://github.com/rust-lang/rfcs/blob/master/text/1236-stabilize-catch-panic.md
104 /// Note that this function **might not catch all panics** in Rust. A panic in
105 /// Rust is not always implemented via unwinding, but can be implemented by
106 /// aborting the process as well. This function *only* catches unwinding panics,
107 /// not those that abort the process.
109 /// Also note that unwinding into Rust code with a foreign exception (e.g.
110 /// an exception thrown from C++ code) is undefined behavior.
117 /// let result = panic::catch_unwind(|| {
118 /// println!("hello!");
120 /// assert!(result.is_ok());
122 /// let result = panic::catch_unwind(|| {
123 /// panic!("oh no!");
125 /// assert!(result.is_err());
127 #[stable(feature = "catch_unwind", since = "1.9.0")]
128 pub fn catch_unwind<F: FnOnce() -> R + UnwindSafe, R>(f: F) -> Result<R> {
129 unsafe { panicking::r#try(f) }
132 /// Triggers a panic without invoking the panic hook.
134 /// This is designed to be used in conjunction with [`catch_unwind`] to, for
135 /// example, carry a panic across a layer of C code.
139 /// Note that panics in Rust are not always implemented via unwinding, but they
140 /// may be implemented by aborting the process. If this function is called when
141 /// panics are implemented this way then this function will abort the process,
142 /// not trigger an unwind.
149 /// let result = panic::catch_unwind(|| {
150 /// panic!("oh no!");
153 /// if let Err(err) = result {
154 /// panic::resume_unwind(err);
157 #[stable(feature = "resume_unwind", since = "1.9.0")]
158 pub fn resume_unwind(payload: Box<dyn Any + Send>) -> ! {
159 panicking::rust_panic_without_hook(payload)
162 /// Make all future panics abort directly without running the panic hook or unwinding.
164 /// There is no way to undo this; the effect lasts until the process exits or
165 /// execs (or the equivalent).
169 /// This function is particularly useful for calling after `libc::fork`. After `fork`, in a
170 /// multithreaded program it is (on many platforms) not safe to call the allocator. It is also
171 /// generally highly undesirable for an unwind to unwind past the `fork`, because that results in
172 /// the unwind propagating to code that was only ever expecting to run in the parent.
174 /// `panic::always_abort()` helps avoid both of these. It directly avoids any further unwinding,
175 /// and if there is a panic, the abort will occur without allocating provided that the arguments to
176 /// panic can be formatted without allocating.
181 /// #![feature(panic_always_abort)]
184 /// panic::always_abort();
186 /// let _ = panic::catch_unwind(|| {
187 /// panic!("inside the catch");
190 /// // We will have aborted already, due to the panic.
193 #[unstable(feature = "panic_always_abort", issue = "84438")]
194 pub fn always_abort() {
195 crate::panicking::panic_count::set_always_abort();