| //! Implementation of various bits and pieces of the `panic!` macro and |
| //! associated runtime pieces. |
| //! |
| //! Specifically, this module contains the implementation of: |
| //! |
| //! * Panic hooks |
| //! * Executing a panic up to doing the actual implementation |
| //! * Shims around "try" |
| |
| #![deny(unsafe_op_in_unsafe_fn)] |
| |
| use crate::panic::BacktraceStyle; |
| use core::panic::{BoxMeUp, Location, PanicInfo}; |
| |
| use crate::any::Any; |
| use crate::fmt; |
| use crate::intrinsics; |
| use crate::mem::{self, ManuallyDrop}; |
| use crate::process; |
| use crate::sync::atomic::{AtomicBool, Ordering}; |
| use crate::sync::{PoisonError, RwLock}; |
| use crate::sys::stdio::panic_output; |
| use crate::sys_common::backtrace; |
| use crate::sys_common::thread_info; |
| use crate::thread; |
| |
| #[cfg(not(test))] |
| use crate::io::set_output_capture; |
| // make sure to use the stderr output configured |
| // by libtest in the real copy of std |
| #[cfg(test)] |
| use realstd::io::set_output_capture; |
| |
| // Binary interface to the panic runtime that the standard library depends on. |
| // |
| // The standard library is tagged with `#![needs_panic_runtime]` (introduced in |
| // RFC 1513) to indicate that it requires some other crate tagged with |
| // `#![panic_runtime]` to exist somewhere. Each panic runtime is intended to |
| // implement these symbols (with the same signatures) so we can get matched up |
| // to them. |
| // |
| // One day this may look a little less ad-hoc with the compiler helping out to |
| // hook up these functions, but it is not this day! |
| #[allow(improper_ctypes)] |
| extern "C" { |
| fn __rust_panic_cleanup(payload: *mut u8) -> *mut (dyn Any + Send + 'static); |
| } |
| |
| #[allow(improper_ctypes)] |
| extern "Rust" { |
| /// `payload` is passed through another layer of raw pointers as `&mut dyn Trait` is not |
| /// FFI-safe. `BoxMeUp` lazily performs allocation only when needed (this avoids allocations |
| /// when using the "abort" panic runtime). |
| fn __rust_start_panic(payload: *mut &mut dyn BoxMeUp) -> u32; |
| } |
| |
| /// This function is called by the panic runtime if FFI code catches a Rust |
| /// panic but doesn't rethrow it. We don't support this case since it messes |
| /// with our panic count. |
| #[cfg(not(test))] |
| #[rustc_std_internal_symbol] |
| extern "C" fn __rust_drop_panic() -> ! { |
| rtabort!("Rust panics must be rethrown"); |
| } |
| |
| /// This function is called by the panic runtime if it catches an exception |
| /// object which does not correspond to a Rust panic. |
| #[cfg(not(test))] |
| #[rustc_std_internal_symbol] |
| extern "C" fn __rust_foreign_exception() -> ! { |
| rtabort!("Rust cannot catch foreign exceptions"); |
| } |
| |
| enum Hook { |
| Default, |
| Custom(Box<dyn Fn(&PanicInfo<'_>) + 'static + Sync + Send>), |
| } |
| |
| impl Hook { |
| #[inline] |
| fn into_box(self) -> Box<dyn Fn(&PanicInfo<'_>) + 'static + Sync + Send> { |
| match self { |
| Hook::Default => Box::new(default_hook), |
| Hook::Custom(hook) => hook, |
| } |
| } |
| } |
| |
| impl Default for Hook { |
| #[inline] |
| fn default() -> Hook { |
| Hook::Default |
| } |
| } |
| |
| static HOOK: RwLock<Hook> = RwLock::new(Hook::Default); |
| |
| /// Registers a custom panic hook, replacing any that was previously registered. |
| /// |
| /// The panic hook is invoked when a thread panics, but before the panic runtime |
| /// is invoked. As such, the hook will run with both the aborting and unwinding |
| /// runtimes. The default hook prints a message to standard error and generates |
| /// a backtrace if requested, but this behavior can be customized with the |
| /// `set_hook` and [`take_hook`] functions. |
| /// |
| /// [`take_hook`]: ./fn.take_hook.html |
| /// |
| /// The hook is provided with a `PanicInfo` struct which contains information |
| /// about the origin of the panic, including the payload passed to `panic!` and |
| /// the source code location from which the panic originated. |
| /// |
| /// The panic hook is a global resource. |
| /// |
| /// # Panics |
| /// |
| /// Panics if called from a panicking thread. |
| /// |
| /// # Examples |
| /// |
| /// The following will print "Custom panic hook": |
| /// |
| /// ```should_panic |
| /// use std::panic; |
| /// |
| /// panic::set_hook(Box::new(|_| { |
| /// println!("Custom panic hook"); |
| /// })); |
| /// |
| /// panic!("Normal panic"); |
| /// ``` |
| #[stable(feature = "panic_hooks", since = "1.10.0")] |
| pub fn set_hook(hook: Box<dyn Fn(&PanicInfo<'_>) + 'static + Sync + Send>) { |
| if thread::panicking() { |
| panic!("cannot modify the panic hook from a panicking thread"); |
| } |
| |
| let new = Hook::Custom(hook); |
| let mut hook = HOOK.write().unwrap_or_else(PoisonError::into_inner); |
| let old = mem::replace(&mut *hook, new); |
| drop(hook); |
| // Only drop the old hook after releasing the lock to avoid deadlocking |
| // if its destructor panics. |
| drop(old); |
| } |
| |
| /// Unregisters the current panic hook, returning it. |
| /// |
| /// *See also the function [`set_hook`].* |
| /// |
| /// [`set_hook`]: ./fn.set_hook.html |
| /// |
| /// If no custom hook is registered, the default hook will be returned. |
| /// |
| /// # Panics |
| /// |
| /// Panics if called from a panicking thread. |
| /// |
| /// # Examples |
| /// |
| /// The following will print "Normal panic": |
| /// |
| /// ```should_panic |
| /// use std::panic; |
| /// |
| /// panic::set_hook(Box::new(|_| { |
| /// println!("Custom panic hook"); |
| /// })); |
| /// |
| /// let _ = panic::take_hook(); |
| /// |
| /// panic!("Normal panic"); |
| /// ``` |
| #[must_use] |
| #[stable(feature = "panic_hooks", since = "1.10.0")] |
| pub fn take_hook() -> Box<dyn Fn(&PanicInfo<'_>) + 'static + Sync + Send> { |
| if thread::panicking() { |
| panic!("cannot modify the panic hook from a panicking thread"); |
| } |
| |
| let mut hook = HOOK.write().unwrap_or_else(PoisonError::into_inner); |
| let old_hook = mem::take(&mut *hook); |
| drop(hook); |
| |
| old_hook.into_box() |
| } |
| |
| /// Atomic combination of [`take_hook`] and [`set_hook`]. Use this to replace the panic handler with |
| /// a new panic handler that does something and then executes the old handler. |
| /// |
| /// [`take_hook`]: ./fn.take_hook.html |
| /// [`set_hook`]: ./fn.set_hook.html |
| /// |
| /// # Panics |
| /// |
| /// Panics if called from a panicking thread. |
| /// |
| /// # Examples |
| /// |
| /// The following will print the custom message, and then the normal output of panic. |
| /// |
| /// ```should_panic |
| /// #![feature(panic_update_hook)] |
| /// use std::panic; |
| /// |
| /// // Equivalent to |
| /// // let prev = panic::take_hook(); |
| /// // panic::set_hook(move |info| { |
| /// // println!("..."); |
| /// // prev(info); |
| /// // ); |
| /// panic::update_hook(move |prev, info| { |
| /// println!("Print custom message and execute panic handler as usual"); |
| /// prev(info); |
| /// }); |
| /// |
| /// panic!("Custom and then normal"); |
| /// ``` |
| #[unstable(feature = "panic_update_hook", issue = "92649")] |
| pub fn update_hook<F>(hook_fn: F) |
| where |
| F: Fn(&(dyn Fn(&PanicInfo<'_>) + Send + Sync + 'static), &PanicInfo<'_>) |
| + Sync |
| + Send |
| + 'static, |
| { |
| if thread::panicking() { |
| panic!("cannot modify the panic hook from a panicking thread"); |
| } |
| |
| let mut hook = HOOK.write().unwrap_or_else(PoisonError::into_inner); |
| let prev = mem::take(&mut *hook).into_box(); |
| *hook = Hook::Custom(Box::new(move |info| hook_fn(&prev, info))); |
| } |
| |
| fn default_hook(info: &PanicInfo<'_>) { |
| // If this is a double panic, make sure that we print a backtrace |
| // for this panic. Otherwise only print it if logging is enabled. |
| let backtrace = if panic_count::get_count() >= 2 { |
| BacktraceStyle::full() |
| } else { |
| crate::panic::get_backtrace_style() |
| }; |
| |
| // The current implementation always returns `Some`. |
| let location = info.location().unwrap(); |
| |
| let msg = match info.payload().downcast_ref::<&'static str>() { |
| Some(s) => *s, |
| None => match info.payload().downcast_ref::<String>() { |
| Some(s) => &s[..], |
| None => "Box<dyn Any>", |
| }, |
| }; |
| let thread = thread_info::current_thread(); |
| let name = thread.as_ref().and_then(|t| t.name()).unwrap_or("<unnamed>"); |
| |
| let write = |err: &mut dyn crate::io::Write| { |
| let _ = writeln!(err, "thread '{name}' panicked at '{msg}', {location}"); |
| |
| static FIRST_PANIC: AtomicBool = AtomicBool::new(true); |
| |
| match backtrace { |
| Some(BacktraceStyle::Short) => { |
| drop(backtrace::print(err, crate::backtrace_rs::PrintFmt::Short)) |
| } |
| Some(BacktraceStyle::Full) => { |
| drop(backtrace::print(err, crate::backtrace_rs::PrintFmt::Full)) |
| } |
| Some(BacktraceStyle::Off) => { |
| if FIRST_PANIC.swap(false, Ordering::SeqCst) { |
| let _ = writeln!( |
| err, |
| "note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace" |
| ); |
| } |
| } |
| // If backtraces aren't supported, do nothing. |
| None => {} |
| } |
| }; |
| |
| if let Some(local) = set_output_capture(None) { |
| write(&mut *local.lock().unwrap_or_else(|e| e.into_inner())); |
| set_output_capture(Some(local)); |
| } else if let Some(mut out) = panic_output() { |
| write(&mut out); |
| } |
| } |
| |
| #[cfg(not(test))] |
| #[doc(hidden)] |
| #[unstable(feature = "update_panic_count", issue = "none")] |
| pub mod panic_count { |
| use crate::cell::Cell; |
| use crate::sync::atomic::{AtomicUsize, Ordering}; |
| |
| pub const ALWAYS_ABORT_FLAG: usize = 1 << (usize::BITS - 1); |
| |
| // Panic count for the current thread. |
| thread_local! { static LOCAL_PANIC_COUNT: Cell<usize> = const { Cell::new(0) } } |
| |
| // Sum of panic counts from all threads. The purpose of this is to have |
| // a fast path in `count_is_zero` (which is used by `panicking`). In any particular |
| // thread, if that thread currently views `GLOBAL_PANIC_COUNT` as being zero, |
| // then `LOCAL_PANIC_COUNT` in that thread is zero. This invariant holds before |
| // and after increase and decrease, but not necessarily during their execution. |
| // |
| // Additionally, the top bit of GLOBAL_PANIC_COUNT (GLOBAL_ALWAYS_ABORT_FLAG) |
| // records whether panic::always_abort() has been called. This can only be |
| // set, never cleared. |
| // panic::always_abort() is usually called to prevent memory allocations done by |
| // the panic handling in the child created by `libc::fork`. |
| // Memory allocations performed in a child created with `libc::fork` are undefined |
| // behavior in most operating systems. |
| // Accessing LOCAL_PANIC_COUNT in a child created by `libc::fork` would lead to a memory |
| // allocation. Only GLOBAL_PANIC_COUNT can be accessed in this situation. This is |
| // sufficient because a child process will always have exactly one thread only. |
| // See also #85261 for details. |
| // |
| // This could be viewed as a struct containing a single bit and an n-1-bit |
| // value, but if we wrote it like that it would be more than a single word, |
| // and even a newtype around usize would be clumsy because we need atomics. |
| // But we use such a tuple for the return type of increase(). |
| // |
| // Stealing a bit is fine because it just amounts to assuming that each |
| // panicking thread consumes at least 2 bytes of address space. |
| static GLOBAL_PANIC_COUNT: AtomicUsize = AtomicUsize::new(0); |
| |
| // Return the state of the ALWAYS_ABORT_FLAG and number of panics. |
| // |
| // If ALWAYS_ABORT_FLAG is not set, the number is determined on a per-thread |
| // base (stored in LOCAL_PANIC_COUNT), i.e. it is the amount of recursive calls |
| // of the calling thread. |
| // If ALWAYS_ABORT_FLAG is set, the number equals the *global* number of panic |
| // calls. See above why LOCAL_PANIC_COUNT is not used. |
| pub fn increase() -> (bool, usize) { |
| let global_count = GLOBAL_PANIC_COUNT.fetch_add(1, Ordering::Relaxed); |
| let must_abort = global_count & ALWAYS_ABORT_FLAG != 0; |
| let panics = if must_abort { |
| global_count & !ALWAYS_ABORT_FLAG |
| } else { |
| LOCAL_PANIC_COUNT.with(|c| { |
| let next = c.get() + 1; |
| c.set(next); |
| next |
| }) |
| }; |
| (must_abort, panics) |
| } |
| |
| pub fn decrease() { |
| GLOBAL_PANIC_COUNT.fetch_sub(1, Ordering::Relaxed); |
| LOCAL_PANIC_COUNT.with(|c| { |
| let next = c.get() - 1; |
| c.set(next); |
| next |
| }); |
| } |
| |
| pub fn set_always_abort() { |
| GLOBAL_PANIC_COUNT.fetch_or(ALWAYS_ABORT_FLAG, Ordering::Relaxed); |
| } |
| |
| // Disregards ALWAYS_ABORT_FLAG |
| #[must_use] |
| pub fn get_count() -> usize { |
| LOCAL_PANIC_COUNT.with(|c| c.get()) |
| } |
| |
| // Disregards ALWAYS_ABORT_FLAG |
| #[must_use] |
| #[inline] |
| pub fn count_is_zero() -> bool { |
| if GLOBAL_PANIC_COUNT.load(Ordering::Relaxed) & !ALWAYS_ABORT_FLAG == 0 { |
| // Fast path: if `GLOBAL_PANIC_COUNT` is zero, all threads |
| // (including the current one) will have `LOCAL_PANIC_COUNT` |
| // equal to zero, so TLS access can be avoided. |
| // |
| // In terms of performance, a relaxed atomic load is similar to a normal |
| // aligned memory read (e.g., a mov instruction in x86), but with some |
| // compiler optimization restrictions. On the other hand, a TLS access |
| // might require calling a non-inlinable function (such as `__tls_get_addr` |
| // when using the GD TLS model). |
| true |
| } else { |
| is_zero_slow_path() |
| } |
| } |
| |
| // Slow path is in a separate function to reduce the amount of code |
| // inlined from `count_is_zero`. |
| #[inline(never)] |
| #[cold] |
| fn is_zero_slow_path() -> bool { |
| LOCAL_PANIC_COUNT.with(|c| c.get() == 0) |
| } |
| } |
| |
| #[cfg(test)] |
| pub use realstd::rt::panic_count; |
| |
| /// Invoke a closure, capturing the cause of an unwinding panic if one occurs. |
| pub unsafe fn r#try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>> { |
| union Data<F, R> { |
| f: ManuallyDrop<F>, |
| r: ManuallyDrop<R>, |
| p: ManuallyDrop<Box<dyn Any + Send>>, |
| } |
| |
| // We do some sketchy operations with ownership here for the sake of |
| // performance. We can only pass pointers down to `do_call` (can't pass |
| // objects by value), so we do all the ownership tracking here manually |
| // using a union. |
| // |
| // We go through a transition where: |
| // |
| // * First, we set the data field `f` to be the argumentless closure that we're going to call. |
| // * When we make the function call, the `do_call` function below, we take |
| // ownership of the function pointer. At this point the `data` union is |
| // entirely uninitialized. |
| // * If the closure successfully returns, we write the return value into the |
| // data's return slot (field `r`). |
| // * If the closure panics (`do_catch` below), we write the panic payload into field `p`. |
| // * Finally, when we come back out of the `try` intrinsic we're |
| // in one of two states: |
| // |
| // 1. The closure didn't panic, in which case the return value was |
| // filled in. We move it out of `data.r` and return it. |
| // 2. The closure panicked, in which case the panic payload was |
| // filled in. We move it out of `data.p` and return it. |
| // |
| // Once we stack all that together we should have the "most efficient' |
| // method of calling a catch panic whilst juggling ownership. |
| let mut data = Data { f: ManuallyDrop::new(f) }; |
| |
| let data_ptr = &mut data as *mut _ as *mut u8; |
| // SAFETY: |
| // |
| // Access to the union's fields: this is `std` and we know that the `r#try` |
| // intrinsic fills in the `r` or `p` union field based on its return value. |
| // |
| // The call to `intrinsics::r#try` is made safe by: |
| // - `do_call`, the first argument, can be called with the initial `data_ptr`. |
| // - `do_catch`, the second argument, can be called with the `data_ptr` as well. |
| // See their safety preconditions for more information |
| unsafe { |
| return if intrinsics::r#try(do_call::<F, R>, data_ptr, do_catch::<F, R>) == 0 { |
| Ok(ManuallyDrop::into_inner(data.r)) |
| } else { |
| Err(ManuallyDrop::into_inner(data.p)) |
| }; |
| } |
| |
| // We consider unwinding to be rare, so mark this function as cold. However, |
| // do not mark it no-inline -- that decision is best to leave to the |
| // optimizer (in most cases this function is not inlined even as a normal, |
| // non-cold function, though, as of the writing of this comment). |
| #[cold] |
| unsafe fn cleanup(payload: *mut u8) -> Box<dyn Any + Send + 'static> { |
| // SAFETY: The whole unsafe block hinges on a correct implementation of |
| // the panic handler `__rust_panic_cleanup`. As such we can only |
| // assume it returns the correct thing for `Box::from_raw` to work |
| // without undefined behavior. |
| let obj = unsafe { Box::from_raw(__rust_panic_cleanup(payload)) }; |
| panic_count::decrease(); |
| obj |
| } |
| |
| // SAFETY: |
| // data must be non-NUL, correctly aligned, and a pointer to a `Data<F, R>` |
| // Its must contains a valid `f` (type: F) value that can be use to fill |
| // `data.r`. |
| // |
| // This function cannot be marked as `unsafe` because `intrinsics::r#try` |
| // expects normal function pointers. |
| #[inline] |
| fn do_call<F: FnOnce() -> R, R>(data: *mut u8) { |
| // SAFETY: this is the responsibility of the caller, see above. |
| unsafe { |
| let data = data as *mut Data<F, R>; |
| let data = &mut (*data); |
| let f = ManuallyDrop::take(&mut data.f); |
| data.r = ManuallyDrop::new(f()); |
| } |
| } |
| |
| // We *do* want this part of the catch to be inlined: this allows the |
| // compiler to properly track accesses to the Data union and optimize it |
| // away most of the time. |
| // |
| // SAFETY: |
| // data must be non-NUL, correctly aligned, and a pointer to a `Data<F, R>` |
| // Since this uses `cleanup` it also hinges on a correct implementation of |
| // `__rustc_panic_cleanup`. |
| // |
| // This function cannot be marked as `unsafe` because `intrinsics::r#try` |
| // expects normal function pointers. |
| #[inline] |
| fn do_catch<F: FnOnce() -> R, R>(data: *mut u8, payload: *mut u8) { |
| // SAFETY: this is the responsibility of the caller, see above. |
| // |
| // When `__rustc_panic_cleaner` is correctly implemented we can rely |
| // on `obj` being the correct thing to pass to `data.p` (after wrapping |
| // in `ManuallyDrop`). |
| unsafe { |
| let data = data as *mut Data<F, R>; |
| let data = &mut (*data); |
| let obj = cleanup(payload); |
| data.p = ManuallyDrop::new(obj); |
| } |
| } |
| } |
| |
| /// Determines whether the current thread is unwinding because of panic. |
| #[inline] |
| pub fn panicking() -> bool { |
| !panic_count::count_is_zero() |
| } |
| |
| /// Entry point of panics from the libcore crate (`panic_impl` lang item). |
| #[cfg(not(test))] |
| #[panic_handler] |
| pub fn begin_panic_handler(info: &PanicInfo<'_>) -> ! { |
| struct PanicPayload<'a> { |
| inner: &'a fmt::Arguments<'a>, |
| string: Option<String>, |
| } |
| |
| impl<'a> PanicPayload<'a> { |
| fn new(inner: &'a fmt::Arguments<'a>) -> PanicPayload<'a> { |
| PanicPayload { inner, string: None } |
| } |
| |
| fn fill(&mut self) -> &mut String { |
| use crate::fmt::Write; |
| |
| let inner = self.inner; |
| // Lazily, the first time this gets called, run the actual string formatting. |
| self.string.get_or_insert_with(|| { |
| let mut s = String::new(); |
| drop(s.write_fmt(*inner)); |
| s |
| }) |
| } |
| } |
| |
| unsafe impl<'a> BoxMeUp for PanicPayload<'a> { |
| fn take_box(&mut self) -> *mut (dyn Any + Send) { |
| // We do two allocations here, unfortunately. But (a) they're required with the current |
| // scheme, and (b) we don't handle panic + OOM properly anyway (see comment in |
| // begin_panic below). |
| let contents = mem::take(self.fill()); |
| Box::into_raw(Box::new(contents)) |
| } |
| |
| fn get(&mut self) -> &(dyn Any + Send) { |
| self.fill() |
| } |
| } |
| |
| struct StrPanicPayload(&'static str); |
| |
| unsafe impl BoxMeUp for StrPanicPayload { |
| fn take_box(&mut self) -> *mut (dyn Any + Send) { |
| Box::into_raw(Box::new(self.0)) |
| } |
| |
| fn get(&mut self) -> &(dyn Any + Send) { |
| &self.0 |
| } |
| } |
| |
| let loc = info.location().unwrap(); // The current implementation always returns Some |
| let msg = info.message().unwrap(); // The current implementation always returns Some |
| crate::sys_common::backtrace::__rust_end_short_backtrace(move || { |
| if let Some(msg) = msg.as_str() { |
| rust_panic_with_hook(&mut StrPanicPayload(msg), info.message(), loc, info.can_unwind()); |
| } else { |
| rust_panic_with_hook( |
| &mut PanicPayload::new(msg), |
| info.message(), |
| loc, |
| info.can_unwind(), |
| ); |
| } |
| }) |
| } |
| |
| /// This is the entry point of panicking for the non-format-string variants of |
| /// panic!() and assert!(). In particular, this is the only entry point that supports |
| /// arbitrary payloads, not just format strings. |
| #[unstable(feature = "libstd_sys_internals", reason = "used by the panic! macro", issue = "none")] |
| #[cfg_attr(not(test), lang = "begin_panic")] |
| // lang item for CTFE panic support |
| // never inline unless panic_immediate_abort to avoid code |
| // bloat at the call sites as much as possible |
| #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)] |
| #[cfg_attr(feature = "panic_immediate_abort", inline)] |
| #[track_caller] |
| #[rustc_do_not_const_check] // hooked by const-eval |
| pub const fn begin_panic<M: Any + Send>(msg: M) -> ! { |
| if cfg!(feature = "panic_immediate_abort") { |
| intrinsics::abort() |
| } |
| |
| let loc = Location::caller(); |
| return crate::sys_common::backtrace::__rust_end_short_backtrace(move || { |
| rust_panic_with_hook(&mut PanicPayload::new(msg), None, loc, true) |
| }); |
| |
| struct PanicPayload<A> { |
| inner: Option<A>, |
| } |
| |
| impl<A: Send + 'static> PanicPayload<A> { |
| fn new(inner: A) -> PanicPayload<A> { |
| PanicPayload { inner: Some(inner) } |
| } |
| } |
| |
| unsafe impl<A: Send + 'static> BoxMeUp for PanicPayload<A> { |
| fn take_box(&mut self) -> *mut (dyn Any + Send) { |
| // Note that this should be the only allocation performed in this code path. Currently |
| // this means that panic!() on OOM will invoke this code path, but then again we're not |
| // really ready for panic on OOM anyway. If we do start doing this, then we should |
| // propagate this allocation to be performed in the parent of this thread instead of the |
| // thread that's panicking. |
| let data = match self.inner.take() { |
| Some(a) => Box::new(a) as Box<dyn Any + Send>, |
| None => process::abort(), |
| }; |
| Box::into_raw(data) |
| } |
| |
| fn get(&mut self) -> &(dyn Any + Send) { |
| match self.inner { |
| Some(ref a) => a, |
| None => process::abort(), |
| } |
| } |
| } |
| } |
| |
| /// Central point for dispatching panics. |
| /// |
| /// Executes the primary logic for a panic, including checking for recursive |
| /// panics, panic hooks, and finally dispatching to the panic runtime to either |
| /// abort or unwind. |
| fn rust_panic_with_hook( |
| payload: &mut dyn BoxMeUp, |
| message: Option<&fmt::Arguments<'_>>, |
| location: &Location<'_>, |
| can_unwind: bool, |
| ) -> ! { |
| let (must_abort, panics) = panic_count::increase(); |
| |
| // If this is the third nested call (e.g., panics == 2, this is 0-indexed), |
| // the panic hook probably triggered the last panic, otherwise the |
| // double-panic check would have aborted the process. In this case abort the |
| // process real quickly as we don't want to try calling it again as it'll |
| // probably just panic again. |
| if must_abort || panics > 2 { |
| if panics > 2 { |
| // Don't try to print the message in this case |
| // - perhaps that is causing the recursive panics. |
| rtprintpanic!("thread panicked while processing panic. aborting.\n"); |
| } else { |
| // Unfortunately, this does not print a backtrace, because creating |
| // a `Backtrace` will allocate, which we must to avoid here. |
| let panicinfo = PanicInfo::internal_constructor(message, location, can_unwind); |
| rtprintpanic!("{panicinfo}\npanicked after panic::always_abort(), aborting.\n"); |
| } |
| crate::sys::abort_internal(); |
| } |
| |
| let mut info = PanicInfo::internal_constructor(message, location, can_unwind); |
| let hook = HOOK.read().unwrap_or_else(PoisonError::into_inner); |
| match *hook { |
| // Some platforms (like wasm) know that printing to stderr won't ever actually |
| // print anything, and if that's the case we can skip the default |
| // hook. Since string formatting happens lazily when calling `payload` |
| // methods, this means we avoid formatting the string at all! |
| // (The panic runtime might still call `payload.take_box()` though and trigger |
| // formatting.) |
| Hook::Default if panic_output().is_none() => {} |
| Hook::Default => { |
| info.set_payload(payload.get()); |
| default_hook(&info); |
| } |
| Hook::Custom(ref hook) => { |
| info.set_payload(payload.get()); |
| hook(&info); |
| } |
| }; |
| drop(hook); |
| |
| if panics > 1 || !can_unwind { |
| // If a thread panics while it's already unwinding then we |
| // have limited options. Currently our preference is to |
| // just abort. In the future we may consider resuming |
| // unwinding or otherwise exiting the thread cleanly. |
| rtprintpanic!("thread panicked while panicking. aborting.\n"); |
| crate::sys::abort_internal(); |
| } |
| |
| rust_panic(payload) |
| } |
| |
| /// This is the entry point for `resume_unwind`. |
| /// It just forwards the payload to the panic runtime. |
| pub fn rust_panic_without_hook(payload: Box<dyn Any + Send>) -> ! { |
| panic_count::increase(); |
| |
| struct RewrapBox(Box<dyn Any + Send>); |
| |
| unsafe impl BoxMeUp for RewrapBox { |
| fn take_box(&mut self) -> *mut (dyn Any + Send) { |
| Box::into_raw(mem::replace(&mut self.0, Box::new(()))) |
| } |
| |
| fn get(&mut self) -> &(dyn Any + Send) { |
| &*self.0 |
| } |
| } |
| |
| rust_panic(&mut RewrapBox(payload)) |
| } |
| |
| /// An unmangled function (through `rustc_std_internal_symbol`) on which to slap |
| /// yer breakpoints. |
| #[inline(never)] |
| #[cfg_attr(not(test), rustc_std_internal_symbol)] |
| fn rust_panic(mut msg: &mut dyn BoxMeUp) -> ! { |
| let code = unsafe { |
| let obj = &mut msg as *mut &mut dyn BoxMeUp; |
| __rust_start_panic(obj) |
| }; |
| rtabort!("failed to initiate panic, error {code}") |
| } |