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//! Panic support in the standard library. #![stable(feature = "core_panic_info", since = "1.41.0")] use crate::any::Any; use crate::fmt; #[doc(hidden)] #[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")] #[allow_internal_unstable(core_panic)] #[rustc_diagnostic_item = "core_panic_2015_macro"] #[rustc_macro_transparency = "semitransparent"] pub macro panic_2015 { () => ( $crate::panicking::panic("explicit panic") ), ($msg:literal $(,)?) => ( $crate::panicking::panic($msg) ), ($msg:expr $(,)?) => ( $crate::panicking::panic_str($msg) ), ($fmt:expr, $($arg:tt)+) => ( $crate::panicking::panic_fmt($crate::format_args!($fmt, $($arg)+)) ), } #[doc(hidden)] #[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")] #[allow_internal_unstable(core_panic)] #[rustc_diagnostic_item = "core_panic_2021_macro"] #[rustc_macro_transparency = "semitransparent"] pub macro panic_2021 { () => ( $crate::panicking::panic("explicit panic") ), ($($t:tt)+) => ( $crate::panicking::panic_fmt($crate::format_args!($($t)+)) ), } /// A struct providing information about a panic. /// /// `PanicInfo` structure is passed to a panic hook set by the [`set_hook`] /// function. /// /// [`set_hook`]: ../../std/panic/fn.set_hook.html /// /// # Examples /// /// ```should_panic /// use std::panic; /// /// panic::set_hook(Box::new(|panic_info| { /// if let Some(s) = panic_info.payload().downcast_ref::<&str>() { /// println!("panic occurred: {:?}", s); /// } else { /// println!("panic occurred"); /// } /// })); /// /// panic!("Normal panic"); /// ``` #[lang = "panic_info"] #[stable(feature = "panic_hooks", since = "1.10.0")] #[derive(Debug)] pub struct PanicInfo<'a> { payload: &'a (dyn Any + Send), message: Option<&'a fmt::Arguments<'a>>, location: &'a Location<'a>, } impl<'a> PanicInfo<'a> { #[unstable( feature = "panic_internals", reason = "internal details of the implementation of the `panic!` and related macros", issue = "none" )] #[doc(hidden)] #[inline] pub fn internal_constructor( message: Option<&'a fmt::Arguments<'a>>, location: &'a Location<'a>, ) -> Self { struct NoPayload; PanicInfo { location, message, payload: &NoPayload } } #[unstable( feature = "panic_internals", reason = "internal details of the implementation of the `panic!` and related macros", issue = "none" )] #[doc(hidden)] #[inline] pub fn set_payload(&mut self, info: &'a (dyn Any + Send)) { self.payload = info; } /// Returns the payload associated with the panic. /// /// This will commonly, but not always, be a `&'static str` or [`String`]. /// /// [`String`]: ../../std/string/struct.String.html /// /// # Examples /// /// ```should_panic /// use std::panic; /// /// panic::set_hook(Box::new(|panic_info| { /// if let Some(s) = panic_info.payload().downcast_ref::<&str>() { /// println!("panic occurred: {:?}", s); /// } else { /// println!("panic occurred"); /// } /// })); /// /// panic!("Normal panic"); /// ``` #[stable(feature = "panic_hooks", since = "1.10.0")] pub fn payload(&self) -> &(dyn Any + Send) { self.payload } /// If the `panic!` macro from the `core` crate (not from `std`) /// was used with a formatting string and some additional arguments, /// returns that message ready to be used for example with [`fmt::write`] #[unstable(feature = "panic_info_message", issue = "66745")] pub fn message(&self) -> Option<&fmt::Arguments<'_>> { self.message } /// Returns information about the location from which the panic originated, /// if available. /// /// This method will currently always return [`Some`], but this may change /// in future versions. /// /// # Examples /// /// ```should_panic /// use std::panic; /// /// panic::set_hook(Box::new(|panic_info| { /// if let Some(location) = panic_info.location() { /// println!("panic occurred in file '{}' at line {}", /// location.file(), /// location.line(), /// ); /// } else { /// println!("panic occurred but can't get location information..."); /// } /// })); /// /// panic!("Normal panic"); /// ``` #[stable(feature = "panic_hooks", since = "1.10.0")] pub fn location(&self) -> Option<&Location<'_>> { // NOTE: If this is changed to sometimes return None, // deal with that case in std::panicking::default_hook and std::panicking::begin_panic_fmt. Some(&self.location) } } #[stable(feature = "panic_hook_display", since = "1.26.0")] impl fmt::Display for PanicInfo<'_> { fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result { formatter.write_str("panicked at ")?; if let Some(message) = self.message { write!(formatter, "'{}', ", message)? } else if let Some(payload) = self.payload.downcast_ref::<&'static str>() { write!(formatter, "'{}', ", payload)? } // NOTE: we cannot use downcast_ref::<String>() here // since String is not available in libcore! // The payload is a String when `std::panic!` is called with multiple arguments, // but in that case the message is also available. self.location.fmt(formatter) } } /// A struct containing information about the location of a panic. /// /// This structure is created by [`PanicInfo::location()`]. /// /// # Examples /// /// ```should_panic /// use std::panic; /// /// panic::set_hook(Box::new(|panic_info| { /// if let Some(location) = panic_info.location() { /// println!("panic occurred in file '{}' at line {}", location.file(), location.line()); /// } else { /// println!("panic occurred but can't get location information..."); /// } /// })); /// /// panic!("Normal panic"); /// ``` /// /// # Comparisons /// /// Comparisons for equality and ordering are made in file, line, then column priority. /// Files are compared as strings, not `Path`, which could be unexpected. /// See [`Location::file`]'s documentation for more discussion. #[lang = "panic_location"] #[derive(Copy, Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)] #[stable(feature = "panic_hooks", since = "1.10.0")] pub struct Location<'a> { file: &'a str, line: u32, col: u32, } impl<'a> Location<'a> { /// Returns the source location of the caller of this function. If that function's caller is /// annotated then its call location will be returned, and so on up the stack to the first call /// within a non-tracked function body. /// /// # Examples /// /// ``` /// use std::panic::Location; /// /// /// Returns the [`Location`] at which it is called. /// #[track_caller] /// fn get_caller_location() -> &'static Location<'static> { /// Location::caller() /// } /// /// /// Returns a [`Location`] from within this function's definition. /// fn get_just_one_location() -> &'static Location<'static> { /// get_caller_location() /// } /// /// let fixed_location = get_just_one_location(); /// assert_eq!(fixed_location.file(), file!()); /// assert_eq!(fixed_location.line(), 14); /// assert_eq!(fixed_location.column(), 5); /// /// // running the same untracked function in a different location gives us the same result /// let second_fixed_location = get_just_one_location(); /// assert_eq!(fixed_location.file(), second_fixed_location.file()); /// assert_eq!(fixed_location.line(), second_fixed_location.line()); /// assert_eq!(fixed_location.column(), second_fixed_location.column()); /// /// let this_location = get_caller_location(); /// assert_eq!(this_location.file(), file!()); /// assert_eq!(this_location.line(), 28); /// assert_eq!(this_location.column(), 21); /// /// // running the tracked function in a different location produces a different value /// let another_location = get_caller_location(); /// assert_eq!(this_location.file(), another_location.file()); /// assert_ne!(this_location.line(), another_location.line()); /// assert_ne!(this_location.column(), another_location.column()); /// ``` #[stable(feature = "track_caller", since = "1.46.0")] #[rustc_const_unstable(feature = "const_caller_location", issue = "76156")] #[track_caller] pub const fn caller() -> &'static Location<'static> { crate::intrinsics::caller_location() } } impl<'a> Location<'a> { #![unstable( feature = "panic_internals", reason = "internal details of the implementation of the `panic!` and related macros", issue = "none" )] #[doc(hidden)] pub const fn internal_constructor(file: &'a str, line: u32, col: u32) -> Self { Location { file, line, col } } /// Returns the name of the source file from which the panic originated. /// /// # `&str`, not `&Path` /// /// The returned name refers to a source path on the compiling system, but it isn't valid to /// represent this directly as a `&Path`. The compiled code may run on a different system with /// a different `Path` implementation than the system providing the contents and this library /// does not currently have a different "host path" type. /// /// The most surprising behavior occurs when "the same" file is reachable via multiple paths in /// the module system (usually using the `#[path = "..."]` attribute or similar), which can /// cause what appears to be identical code to return differing values from this function. /// /// # Cross-compilation /// /// This value is not suitable for passing to `Path::new` or similar constructors when the host /// platform and target platform differ. /// /// # Examples /// /// ```should_panic /// use std::panic; /// /// panic::set_hook(Box::new(|panic_info| { /// if let Some(location) = panic_info.location() { /// println!("panic occurred in file '{}'", location.file()); /// } else { /// println!("panic occurred but can't get location information..."); /// } /// })); /// /// panic!("Normal panic"); /// ``` #[stable(feature = "panic_hooks", since = "1.10.0")] pub fn file(&self) -> &str { self.file } /// Returns the line number from which the panic originated. /// /// # Examples /// /// ```should_panic /// use std::panic; /// /// panic::set_hook(Box::new(|panic_info| { /// if let Some(location) = panic_info.location() { /// println!("panic occurred at line {}", location.line()); /// } else { /// println!("panic occurred but can't get location information..."); /// } /// })); /// /// panic!("Normal panic"); /// ``` #[stable(feature = "panic_hooks", since = "1.10.0")] pub fn line(&self) -> u32 { self.line } /// Returns the column from which the panic originated. /// /// # Examples /// /// ```should_panic /// use std::panic; /// /// panic::set_hook(Box::new(|panic_info| { /// if let Some(location) = panic_info.location() { /// println!("panic occurred at column {}", location.column()); /// } else { /// println!("panic occurred but can't get location information..."); /// } /// })); /// /// panic!("Normal panic"); /// ``` #[stable(feature = "panic_col", since = "1.25.0")] pub fn column(&self) -> u32 { self.col } } #[stable(feature = "panic_hook_display", since = "1.26.0")] impl fmt::Display for Location<'_> { fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result { write!(formatter, "{}:{}:{}", self.file, self.line, self.col) } } /// An internal trait used by libstd to pass data from libstd to `panic_unwind` /// and other panic runtimes. Not intended to be stabilized any time soon, do /// not use. #[unstable(feature = "std_internals", issue = "none")] #[doc(hidden)] pub unsafe trait BoxMeUp { /// Take full ownership of the contents. /// The return type is actually `Box<dyn Any + Send>`, but we cannot use `Box` in libcore. /// /// After this method got called, only some dummy default value is left in `self`. /// Calling this method twice, or calling `get` after calling this method, is an error. /// /// The argument is borrowed because the panic runtime (`__rust_start_panic`) only /// gets a borrowed `dyn BoxMeUp`. fn take_box(&mut self) -> *mut (dyn Any + Send); /// Just borrow the contents. fn get(&mut self) -> &(dyn Any + Send); }