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, core_panic)]
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 // Special-case the single-argument case for const_panic.
24 ("{}", $arg:expr $(,)?) => ({
25 $crate::rt::panic_display(&$arg)
27 ($fmt:expr, $($arg:tt)+) => ({
28 $crate::rt::panic_fmt($crate::const_format_args!($fmt, $($arg)+))
33 #[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")]
34 pub use core::panic::panic_2021;
36 #[stable(feature = "panic_hooks", since = "1.10.0")]
37 pub use crate::panicking::{set_hook, take_hook};
39 #[unstable(feature = "panic_update_hook", issue = "92649")]
40 pub use crate::panicking::update_hook;
42 #[stable(feature = "panic_hooks", since = "1.10.0")]
43 pub use core::panic::{Location, PanicInfo};
45 #[stable(feature = "catch_unwind", since = "1.9.0")]
46 pub use core::panic::{AssertUnwindSafe, RefUnwindSafe, UnwindSafe};
48 /// Panic the current thread with the given message as the panic payload.
50 /// The message can be of any (`Any + Send`) type, not just strings.
52 /// The message is wrapped in a `Box<'static + Any + Send>`, which can be
53 /// accessed later using [`PanicInfo::payload`].
55 /// See the [`panic!`] macro for more information about panicking.
56 #[stable(feature = "panic_any", since = "1.51.0")]
59 pub fn panic_any<M: 'static + Any + Send>(msg: M) -> ! {
60 crate::panicking::begin_panic(msg);
63 #[stable(feature = "catch_unwind", since = "1.9.0")]
64 impl<T: ?Sized> UnwindSafe for Mutex<T> {}
65 #[stable(feature = "catch_unwind", since = "1.9.0")]
66 impl<T: ?Sized> UnwindSafe for RwLock<T> {}
68 #[stable(feature = "unwind_safe_lock_refs", since = "1.12.0")]
69 impl<T: ?Sized> RefUnwindSafe for Mutex<T> {}
70 #[stable(feature = "unwind_safe_lock_refs", since = "1.12.0")]
71 impl<T: ?Sized> RefUnwindSafe for RwLock<T> {}
73 // https://github.com/rust-lang/rust/issues/62301
74 #[stable(feature = "hashbrown", since = "1.36.0")]
75 impl<K, V, S> UnwindSafe for collections::HashMap<K, V, S>
83 /// Invokes a closure, capturing the cause of an unwinding panic if one occurs.
85 /// This function will return `Ok` with the closure's result if the closure
86 /// does not panic, and will return `Err(cause)` if the closure panics. The
87 /// `cause` returned is the object with which panic was originally invoked.
89 /// It is currently undefined behavior to unwind from Rust code into foreign
90 /// code, so this function is particularly useful when Rust is called from
91 /// another language (normally C). This can run arbitrary Rust code, capturing a
92 /// panic and allowing a graceful handling of the error.
94 /// It is **not** recommended to use this function for a general try/catch
95 /// mechanism. The [`Result`] type is more appropriate to use for functions that
96 /// can fail on a regular basis. Additionally, this function is not guaranteed
97 /// to catch all panics, see the "Notes" section below.
99 /// The closure provided is required to adhere to the [`UnwindSafe`] trait to ensure
100 /// that all captured variables are safe to cross this boundary. The purpose of
101 /// this bound is to encode the concept of [exception safety][rfc] in the type
102 /// system. Most usage of this function should not need to worry about this
103 /// bound as programs are naturally unwind safe without `unsafe` code. If it
104 /// becomes a problem the [`AssertUnwindSafe`] wrapper struct can be used to quickly
105 /// assert that the usage here is indeed unwind safe.
107 /// [rfc]: https://github.com/rust-lang/rfcs/blob/master/text/1236-stabilize-catch-panic.md
111 /// Note that this function **might not catch all panics** in Rust. A panic in
112 /// Rust is not always implemented via unwinding, but can be implemented by
113 /// aborting the process as well. This function *only* catches unwinding panics,
114 /// not those that abort the process.
116 /// Also note that unwinding into Rust code with a foreign exception (e.g.
117 /// an exception thrown from C++ code) is undefined behavior.
124 /// let result = panic::catch_unwind(|| {
125 /// println!("hello!");
127 /// assert!(result.is_ok());
129 /// let result = panic::catch_unwind(|| {
130 /// panic!("oh no!");
132 /// assert!(result.is_err());
134 #[stable(feature = "catch_unwind", since = "1.9.0")]
135 pub fn catch_unwind<F: FnOnce() -> R + UnwindSafe, R>(f: F) -> Result<R> {
136 unsafe { panicking::r#try(f) }
139 /// Triggers a panic without invoking the panic hook.
141 /// This is designed to be used in conjunction with [`catch_unwind`] to, for
142 /// example, carry a panic across a layer of C code.
146 /// Note that panics in Rust are not always implemented via unwinding, but they
147 /// may be implemented by aborting the process. If this function is called when
148 /// panics are implemented this way then this function will abort the process,
149 /// not trigger an unwind.
156 /// let result = panic::catch_unwind(|| {
157 /// panic!("oh no!");
160 /// if let Err(err) = result {
161 /// panic::resume_unwind(err);
164 #[stable(feature = "resume_unwind", since = "1.9.0")]
165 pub fn resume_unwind(payload: Box<dyn Any + Send>) -> ! {
166 panicking::rust_panic_without_hook(payload)
169 /// Make all future panics abort directly without running the panic hook or unwinding.
171 /// There is no way to undo this; the effect lasts until the process exits or
172 /// execs (or the equivalent).
176 /// This function is particularly useful for calling after `libc::fork`. After `fork`, in a
177 /// multithreaded program it is (on many platforms) not safe to call the allocator. It is also
178 /// generally highly undesirable for an unwind to unwind past the `fork`, because that results in
179 /// the unwind propagating to code that was only ever expecting to run in the parent.
181 /// `panic::always_abort()` helps avoid both of these. It directly avoids any further unwinding,
182 /// and if there is a panic, the abort will occur without allocating provided that the arguments to
183 /// panic can be formatted without allocating.
188 /// #![feature(panic_always_abort)]
191 /// panic::always_abort();
193 /// let _ = panic::catch_unwind(|| {
194 /// panic!("inside the catch");
197 /// // We will have aborted already, due to the panic.
200 #[unstable(feature = "panic_always_abort", issue = "84438")]
201 pub fn always_abort() {
202 crate::panicking::panic_count::set_always_abort();