14f7f4b7bf
Thereby, we also allow accessing thread::current before main: as the runtime no longer tries to install its own handle, this will no longer trigger an abort. Rather, the name returned from name will only be "main" after the runtime initialization code has run, but I think that is acceptable. This new approach also requires some changes to the signal handling code, as calling `thread::current` would now allocate when called on the main thread, which is not acceptable. I fixed this by adding a new function (`with_current_name`) that performs all the naming logic without allocation or without initializing the thread ID (which could allocate on some platforms).
902 lines
32 KiB
Rust
902 lines
32 KiB
Rust
//! Implementation of various bits and pieces of the `panic!` macro and
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//! associated runtime pieces.
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//!
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//! Specifically, this module contains the implementation of:
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//!
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//! * Panic hooks
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//! * Executing a panic up to doing the actual implementation
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//! * Shims around "try"
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#![deny(unsafe_op_in_unsafe_fn)]
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use core::panic::{Location, PanicPayload};
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// make sure to use the stderr output configured
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// by libtest in the real copy of std
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#[cfg(test)]
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use realstd::io::try_set_output_capture;
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use crate::any::Any;
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#[cfg(not(test))]
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use crate::io::try_set_output_capture;
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use crate::mem::{self, ManuallyDrop};
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use crate::panic::{BacktraceStyle, PanicHookInfo};
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use crate::sync::atomic::{AtomicBool, Ordering};
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use crate::sync::{PoisonError, RwLock};
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use crate::sys::backtrace;
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use crate::sys::stdio::panic_output;
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use crate::{fmt, intrinsics, process, thread};
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// This forces codegen of the function called by panic!() inside the std crate, rather than in
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// downstream crates. Primarily this is useful for rustc's codegen tests, which rely on noticing
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// complete removal of panic from generated IR. Since begin_panic is inline(never), it's only
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// codegen'd once per crate-graph so this pushes that to std rather than our codegen test crates.
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//
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// (See https://github.com/rust-lang/rust/pull/123244 for more info on why).
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//
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// If this is causing problems we can also modify those codegen tests to use a crate type like
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// cdylib which doesn't export "Rust" symbols to downstream linkage units.
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#[unstable(feature = "libstd_sys_internals", reason = "used by the panic! macro", issue = "none")]
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#[doc(hidden)]
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#[allow(dead_code)]
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#[used(compiler)]
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pub static EMPTY_PANIC: fn(&'static str) -> ! =
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begin_panic::<&'static str> as fn(&'static str) -> !;
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// Binary interface to the panic runtime that the standard library depends on.
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//
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// The standard library is tagged with `#![needs_panic_runtime]` (introduced in
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// RFC 1513) to indicate that it requires some other crate tagged with
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// `#![panic_runtime]` to exist somewhere. Each panic runtime is intended to
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// implement these symbols (with the same signatures) so we can get matched up
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// to them.
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//
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// One day this may look a little less ad-hoc with the compiler helping out to
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// hook up these functions, but it is not this day!
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#[allow(improper_ctypes)]
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extern "C" {
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fn __rust_panic_cleanup(payload: *mut u8) -> *mut (dyn Any + Send + 'static);
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}
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extern "Rust" {
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/// `PanicPayload` lazily performs allocation only when needed (this avoids
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/// allocations when using the "abort" panic runtime).
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fn __rust_start_panic(payload: &mut dyn PanicPayload) -> u32;
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}
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/// This function is called by the panic runtime if FFI code catches a Rust
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/// panic but doesn't rethrow it. We don't support this case since it messes
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/// with our panic count.
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#[cfg(not(test))]
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#[rustc_std_internal_symbol]
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extern "C" fn __rust_drop_panic() -> ! {
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rtabort!("Rust panics must be rethrown");
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}
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/// This function is called by the panic runtime if it catches an exception
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/// object which does not correspond to a Rust panic.
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#[cfg(not(test))]
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#[rustc_std_internal_symbol]
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extern "C" fn __rust_foreign_exception() -> ! {
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rtabort!("Rust cannot catch foreign exceptions");
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}
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#[derive(Default)]
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enum Hook {
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#[default]
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Default,
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Custom(Box<dyn Fn(&PanicHookInfo<'_>) + 'static + Sync + Send>),
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}
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impl Hook {
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#[inline]
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fn into_box(self) -> Box<dyn Fn(&PanicHookInfo<'_>) + 'static + Sync + Send> {
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match self {
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Hook::Default => Box::new(default_hook),
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Hook::Custom(hook) => hook,
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}
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}
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}
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static HOOK: RwLock<Hook> = RwLock::new(Hook::Default);
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/// Registers a custom panic hook, replacing the previously registered hook.
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///
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/// The panic hook is invoked when a thread panics, but before the panic runtime
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/// is invoked. As such, the hook will run with both the aborting and unwinding
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/// runtimes.
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///
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/// The default hook, which is registered at startup, prints a message to standard error and
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/// generates a backtrace if requested. This behavior can be customized using the `set_hook` function.
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/// The current hook can be retrieved while reinstating the default hook with the [`take_hook`]
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/// function.
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///
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/// [`take_hook`]: ./fn.take_hook.html
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///
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/// The hook is provided with a `PanicHookInfo` struct which contains information
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/// about the origin of the panic, including the payload passed to `panic!` and
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/// the source code location from which the panic originated.
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///
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/// The panic hook is a global resource.
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///
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/// # Panics
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///
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/// Panics if called from a panicking thread.
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///
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/// # Examples
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///
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/// The following will print "Custom panic hook":
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///
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/// ```should_panic
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/// use std::panic;
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///
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/// panic::set_hook(Box::new(|_| {
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/// println!("Custom panic hook");
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/// }));
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///
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/// panic!("Normal panic");
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/// ```
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#[stable(feature = "panic_hooks", since = "1.10.0")]
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pub fn set_hook(hook: Box<dyn Fn(&PanicHookInfo<'_>) + 'static + Sync + Send>) {
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if thread::panicking() {
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panic!("cannot modify the panic hook from a panicking thread");
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}
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let new = Hook::Custom(hook);
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let mut hook = HOOK.write().unwrap_or_else(PoisonError::into_inner);
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let old = mem::replace(&mut *hook, new);
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drop(hook);
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// Only drop the old hook after releasing the lock to avoid deadlocking
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// if its destructor panics.
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drop(old);
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}
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/// Unregisters the current panic hook and returns it, registering the default hook
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/// in its place.
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///
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/// *See also the function [`set_hook`].*
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///
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/// [`set_hook`]: ./fn.set_hook.html
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///
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/// If the default hook is registered it will be returned, but remain registered.
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///
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/// # Panics
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///
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/// Panics if called from a panicking thread.
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///
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/// # Examples
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///
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/// The following will print "Normal panic":
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///
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/// ```should_panic
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/// use std::panic;
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///
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/// panic::set_hook(Box::new(|_| {
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/// println!("Custom panic hook");
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/// }));
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///
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/// let _ = panic::take_hook();
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///
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/// panic!("Normal panic");
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/// ```
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#[must_use]
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#[stable(feature = "panic_hooks", since = "1.10.0")]
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pub fn take_hook() -> Box<dyn Fn(&PanicHookInfo<'_>) + 'static + Sync + Send> {
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if thread::panicking() {
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panic!("cannot modify the panic hook from a panicking thread");
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}
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let mut hook = HOOK.write().unwrap_or_else(PoisonError::into_inner);
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let old_hook = mem::take(&mut *hook);
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drop(hook);
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old_hook.into_box()
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}
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/// Atomic combination of [`take_hook`] and [`set_hook`]. Use this to replace the panic handler with
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/// a new panic handler that does something and then executes the old handler.
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///
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/// [`take_hook`]: ./fn.take_hook.html
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/// [`set_hook`]: ./fn.set_hook.html
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///
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/// # Panics
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///
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/// Panics if called from a panicking thread.
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///
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/// # Examples
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///
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/// The following will print the custom message, and then the normal output of panic.
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///
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/// ```should_panic
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/// #![feature(panic_update_hook)]
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/// use std::panic;
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///
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/// // Equivalent to
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/// // let prev = panic::take_hook();
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/// // panic::set_hook(move |info| {
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/// // println!("...");
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/// // prev(info);
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/// // );
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/// panic::update_hook(move |prev, info| {
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/// println!("Print custom message and execute panic handler as usual");
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/// prev(info);
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/// });
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///
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/// panic!("Custom and then normal");
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/// ```
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#[unstable(feature = "panic_update_hook", issue = "92649")]
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pub fn update_hook<F>(hook_fn: F)
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where
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F: Fn(&(dyn Fn(&PanicHookInfo<'_>) + Send + Sync + 'static), &PanicHookInfo<'_>)
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+ Sync
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+ Send
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+ 'static,
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{
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if thread::panicking() {
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panic!("cannot modify the panic hook from a panicking thread");
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}
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let mut hook = HOOK.write().unwrap_or_else(PoisonError::into_inner);
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let prev = mem::take(&mut *hook).into_box();
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*hook = Hook::Custom(Box::new(move |info| hook_fn(&prev, info)));
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}
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/// The default panic handler.
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#[optimize(size)]
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fn default_hook(info: &PanicHookInfo<'_>) {
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// If this is a double panic, make sure that we print a backtrace
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// for this panic. Otherwise only print it if logging is enabled.
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let backtrace = if info.force_no_backtrace() {
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None
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} else if panic_count::get_count() >= 2 {
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BacktraceStyle::full()
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} else {
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crate::panic::get_backtrace_style()
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};
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// The current implementation always returns `Some`.
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let location = info.location().unwrap();
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let msg = payload_as_str(info.payload());
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let write = #[optimize(size)]
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|err: &mut dyn crate::io::Write| {
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// Use a lock to prevent mixed output in multithreading context.
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// Some platforms also require it when printing a backtrace, like `SymFromAddr` on Windows.
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let mut lock = backtrace::lock();
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thread::with_current_name(|name| {
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let name = name.unwrap_or("<unnamed>");
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// Try to write the panic message to a buffer first to prevent other concurrent outputs
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// interleaving with it.
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let mut buffer = [0u8; 512];
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let mut cursor = crate::io::Cursor::new(&mut buffer[..]);
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let write_msg = |dst: &mut dyn crate::io::Write| {
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// We add a newline to ensure the panic message appears at the start of a line.
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writeln!(dst, "\nthread '{name}' panicked at {location}:\n{msg}")
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};
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if write_msg(&mut cursor).is_ok() {
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let pos = cursor.position() as usize;
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let _ = err.write_all(&buffer[0..pos]);
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} else {
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// The message did not fit into the buffer, write it directly instead.
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let _ = write_msg(err);
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};
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});
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static FIRST_PANIC: AtomicBool = AtomicBool::new(true);
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match backtrace {
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// SAFETY: we took out a lock just a second ago.
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Some(BacktraceStyle::Short) => {
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drop(lock.print(err, crate::backtrace_rs::PrintFmt::Short))
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}
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Some(BacktraceStyle::Full) => {
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drop(lock.print(err, crate::backtrace_rs::PrintFmt::Full))
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}
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Some(BacktraceStyle::Off) => {
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if FIRST_PANIC.swap(false, Ordering::Relaxed) {
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let _ = writeln!(
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err,
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"note: run with `RUST_BACKTRACE=1` environment variable to display a \
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backtrace"
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);
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if cfg!(miri) {
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let _ = writeln!(
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err,
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"note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` \
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for the environment variable to have an effect"
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);
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}
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}
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}
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// If backtraces aren't supported or are forced-off, do nothing.
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None => {}
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}
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};
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if let Ok(Some(local)) = try_set_output_capture(None) {
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write(&mut *local.lock().unwrap_or_else(|e| e.into_inner()));
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try_set_output_capture(Some(local)).ok();
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} else if let Some(mut out) = panic_output() {
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write(&mut out);
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}
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}
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#[cfg(not(test))]
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#[doc(hidden)]
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#[cfg(feature = "panic_immediate_abort")]
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#[unstable(feature = "update_panic_count", issue = "none")]
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pub mod panic_count {
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/// A reason for forcing an immediate abort on panic.
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#[derive(Debug)]
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pub enum MustAbort {
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AlwaysAbort,
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PanicInHook,
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}
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#[inline]
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pub fn increase(run_panic_hook: bool) -> Option<MustAbort> {
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None
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}
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#[inline]
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pub fn finished_panic_hook() {}
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#[inline]
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pub fn decrease() {}
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#[inline]
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pub fn set_always_abort() {}
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// Disregards ALWAYS_ABORT_FLAG
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#[inline]
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#[must_use]
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pub fn get_count() -> usize {
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0
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}
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#[must_use]
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#[inline]
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pub fn count_is_zero() -> bool {
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true
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}
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}
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#[cfg(not(test))]
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#[doc(hidden)]
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#[cfg(not(feature = "panic_immediate_abort"))]
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#[unstable(feature = "update_panic_count", issue = "none")]
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pub mod panic_count {
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use crate::cell::Cell;
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use crate::sync::atomic::{AtomicUsize, Ordering};
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const ALWAYS_ABORT_FLAG: usize = 1 << (usize::BITS - 1);
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/// A reason for forcing an immediate abort on panic.
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#[derive(Debug)]
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pub enum MustAbort {
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AlwaysAbort,
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PanicInHook,
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}
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// Panic count for the current thread and whether a panic hook is currently
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// being executed..
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thread_local! {
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static LOCAL_PANIC_COUNT: Cell<(usize, bool)> = const { Cell::new((0, false)) }
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}
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// Sum of panic counts from all threads. The purpose of this is to have
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// a fast path in `count_is_zero` (which is used by `panicking`). In any particular
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// thread, if that thread currently views `GLOBAL_PANIC_COUNT` as being zero,
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// then `LOCAL_PANIC_COUNT` in that thread is zero. This invariant holds before
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// and after increase and decrease, but not necessarily during their execution.
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//
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// Additionally, the top bit of GLOBAL_PANIC_COUNT (GLOBAL_ALWAYS_ABORT_FLAG)
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// records whether panic::always_abort() has been called. This can only be
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// set, never cleared.
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// panic::always_abort() is usually called to prevent memory allocations done by
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// the panic handling in the child created by `libc::fork`.
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// Memory allocations performed in a child created with `libc::fork` are undefined
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// behavior in most operating systems.
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// Accessing LOCAL_PANIC_COUNT in a child created by `libc::fork` would lead to a memory
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// allocation. Only GLOBAL_PANIC_COUNT can be accessed in this situation. This is
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// sufficient because a child process will always have exactly one thread only.
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// See also #85261 for details.
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//
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// This could be viewed as a struct containing a single bit and an n-1-bit
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// value, but if we wrote it like that it would be more than a single word,
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// and even a newtype around usize would be clumsy because we need atomics.
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// But we use such a tuple for the return type of increase().
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//
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// Stealing a bit is fine because it just amounts to assuming that each
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// panicking thread consumes at least 2 bytes of address space.
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static GLOBAL_PANIC_COUNT: AtomicUsize = AtomicUsize::new(0);
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// Increases the global and local panic count, and returns whether an
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// immediate abort is required.
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//
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|
// This also updates thread-local state to keep track of whether a panic
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// hook is currently executing.
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pub fn increase(run_panic_hook: bool) -> Option<MustAbort> {
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let global_count = GLOBAL_PANIC_COUNT.fetch_add(1, Ordering::Relaxed);
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if global_count & ALWAYS_ABORT_FLAG != 0 {
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// Do *not* access thread-local state, we might be after a `fork`.
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return Some(MustAbort::AlwaysAbort);
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}
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LOCAL_PANIC_COUNT.with(|c| {
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let (count, in_panic_hook) = c.get();
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if in_panic_hook {
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return Some(MustAbort::PanicInHook);
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}
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c.set((count + 1, run_panic_hook));
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None
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})
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}
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pub fn finished_panic_hook() {
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LOCAL_PANIC_COUNT.with(|c| {
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let (count, _) = c.get();
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c.set((count, false));
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});
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}
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|
pub fn decrease() {
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GLOBAL_PANIC_COUNT.fetch_sub(1, Ordering::Relaxed);
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|
LOCAL_PANIC_COUNT.with(|c| {
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let (count, _) = c.get();
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|
c.set((count - 1, false));
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});
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}
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|
pub fn set_always_abort() {
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GLOBAL_PANIC_COUNT.fetch_or(ALWAYS_ABORT_FLAG, Ordering::Relaxed);
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}
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// Disregards ALWAYS_ABORT_FLAG
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|
#[must_use]
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|
pub fn get_count() -> usize {
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LOCAL_PANIC_COUNT.with(|c| c.get().0)
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}
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|
// Disregards ALWAYS_ABORT_FLAG
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|
#[must_use]
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|
#[inline]
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|
pub fn count_is_zero() -> bool {
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if GLOBAL_PANIC_COUNT.load(Ordering::Relaxed) & !ALWAYS_ABORT_FLAG == 0 {
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// Fast path: if `GLOBAL_PANIC_COUNT` is zero, all threads
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|
// (including the current one) will have `LOCAL_PANIC_COUNT`
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// equal to zero, so TLS access can be avoided.
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|
//
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|
// In terms of performance, a relaxed atomic load is similar to a normal
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|
// aligned memory read (e.g., a mov instruction in x86), but with some
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|
// compiler optimization restrictions. On the other hand, a TLS access
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|
// might require calling a non-inlinable function (such as `__tls_get_addr`
|
|
// when using the GD TLS model).
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true
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} else {
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|
is_zero_slow_path()
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|
}
|
|
}
|
|
|
|
// 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 == 0)
|
|
}
|
|
}
|
|
|
|
#[cfg(test)]
|
|
pub use realstd::rt::panic_count;
|
|
|
|
/// Invoke a closure, capturing the cause of an unwinding panic if one occurs.
|
|
#[cfg(feature = "panic_immediate_abort")]
|
|
pub unsafe fn r#try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>> {
|
|
Ok(f())
|
|
}
|
|
|
|
/// Invoke a closure, capturing the cause of an unwinding panic if one occurs.
|
|
#[cfg(not(feature = "panic_immediate_abort"))]
|
|
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 = (&raw mut data) 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::catch_unwind` 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::catch_unwind(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]
|
|
#[optimize(size)]
|
|
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::catch_unwind`
|
|
// 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::catch_unwind`
|
|
// expects normal function pointers.
|
|
#[inline]
|
|
#[rustc_nounwind] // `intrinsic::r#try` requires catch fn to be nounwind
|
|
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 core crate (`panic_impl` lang item).
|
|
#[cfg(not(any(test, doctest)))]
|
|
#[panic_handler]
|
|
pub fn begin_panic_handler(info: &core::panic::PanicInfo<'_>) -> ! {
|
|
struct FormatStringPayload<'a> {
|
|
inner: &'a core::panic::PanicMessage<'a>,
|
|
string: Option<String>,
|
|
}
|
|
|
|
impl FormatStringPayload<'_> {
|
|
fn fill(&mut self) -> &mut String {
|
|
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();
|
|
let mut fmt = fmt::Formatter::new(&mut s, fmt::FormattingOptions::new());
|
|
let _err = fmt::Display::fmt(&inner, &mut fmt);
|
|
s
|
|
})
|
|
}
|
|
}
|
|
|
|
unsafe impl PanicPayload for FormatStringPayload<'_> {
|
|
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()
|
|
}
|
|
}
|
|
|
|
impl fmt::Display for FormatStringPayload<'_> {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
if let Some(s) = &self.string {
|
|
f.write_str(s)
|
|
} else {
|
|
fmt::Display::fmt(&self.inner, f)
|
|
}
|
|
}
|
|
}
|
|
|
|
struct StaticStrPayload(&'static str);
|
|
|
|
unsafe impl PanicPayload for StaticStrPayload {
|
|
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
|
|
}
|
|
|
|
fn as_str(&mut self) -> Option<&str> {
|
|
Some(self.0)
|
|
}
|
|
}
|
|
|
|
impl fmt::Display for StaticStrPayload {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
f.write_str(self.0)
|
|
}
|
|
}
|
|
|
|
let loc = info.location().unwrap(); // The current implementation always returns Some
|
|
let msg = info.message();
|
|
crate::sys::backtrace::__rust_end_short_backtrace(move || {
|
|
if let Some(s) = msg.as_str() {
|
|
rust_panic_with_hook(
|
|
&mut StaticStrPayload(s),
|
|
loc,
|
|
info.can_unwind(),
|
|
info.force_no_backtrace(),
|
|
);
|
|
} else {
|
|
rust_panic_with_hook(
|
|
&mut FormatStringPayload { inner: &msg, string: None },
|
|
loc,
|
|
info.can_unwind(),
|
|
info.force_no_backtrace(),
|
|
);
|
|
}
|
|
})
|
|
}
|
|
|
|
/// 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(any(test, doctest)), 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, optimize(size))]
|
|
#[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()
|
|
}
|
|
|
|
struct Payload<A> {
|
|
inner: Option<A>,
|
|
}
|
|
|
|
unsafe impl<A: Send + 'static> PanicPayload for Payload<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(),
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<A: 'static> fmt::Display for Payload<A> {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
match &self.inner {
|
|
Some(a) => f.write_str(payload_as_str(a)),
|
|
None => process::abort(),
|
|
}
|
|
}
|
|
}
|
|
|
|
let loc = Location::caller();
|
|
crate::sys::backtrace::__rust_end_short_backtrace(move || {
|
|
rust_panic_with_hook(
|
|
&mut Payload { inner: Some(msg) },
|
|
loc,
|
|
/* can_unwind */ true,
|
|
/* force_no_backtrace */ false,
|
|
)
|
|
})
|
|
}
|
|
|
|
fn payload_as_str(payload: &dyn Any) -> &str {
|
|
if let Some(&s) = payload.downcast_ref::<&'static str>() {
|
|
s
|
|
} else if let Some(s) = payload.downcast_ref::<String>() {
|
|
s.as_str()
|
|
} else {
|
|
"Box<dyn Any>"
|
|
}
|
|
}
|
|
|
|
/// 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.
|
|
#[optimize(size)]
|
|
fn rust_panic_with_hook(
|
|
payload: &mut dyn PanicPayload,
|
|
location: &Location<'_>,
|
|
can_unwind: bool,
|
|
force_no_backtrace: bool,
|
|
) -> ! {
|
|
let must_abort = panic_count::increase(true);
|
|
|
|
// Check if we need to abort immediately.
|
|
if let Some(must_abort) = must_abort {
|
|
match must_abort {
|
|
panic_count::MustAbort::PanicInHook => {
|
|
// Don't try to format the message in this case, perhaps that is causing the
|
|
// recursive panics. However if the message is just a string, no user-defined
|
|
// code is involved in printing it, so that is risk-free.
|
|
let message: &str = payload.as_str().unwrap_or_default();
|
|
rtprintpanic!(
|
|
"panicked at {location}:\n{message}\nthread panicked while processing panic. aborting.\n"
|
|
);
|
|
}
|
|
panic_count::MustAbort::AlwaysAbort => {
|
|
// Unfortunately, this does not print a backtrace, because creating
|
|
// a `Backtrace` will allocate, which we must avoid here.
|
|
rtprintpanic!("aborting due to panic at {location}:\n{payload}\n");
|
|
}
|
|
}
|
|
crate::sys::abort_internal();
|
|
}
|
|
|
|
match *HOOK.read().unwrap_or_else(PoisonError::into_inner) {
|
|
// 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 => {
|
|
default_hook(&PanicHookInfo::new(
|
|
location,
|
|
payload.get(),
|
|
can_unwind,
|
|
force_no_backtrace,
|
|
));
|
|
}
|
|
Hook::Custom(ref hook) => {
|
|
hook(&PanicHookInfo::new(location, payload.get(), can_unwind, force_no_backtrace));
|
|
}
|
|
}
|
|
|
|
// Indicate that we have finished executing the panic hook. After this point
|
|
// it is fine if there is a panic while executing destructors, as long as it
|
|
// it contained within a `catch_unwind`.
|
|
panic_count::finished_panic_hook();
|
|
|
|
if !can_unwind {
|
|
// If a thread panics while running destructors or tries to unwind
|
|
// through a nounwind function (e.g. extern "C") then we cannot continue
|
|
// unwinding and have to abort immediately.
|
|
rtprintpanic!("thread caused non-unwinding panic. 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.
|
|
#[cfg_attr(feature = "panic_immediate_abort", inline)]
|
|
pub fn rust_panic_without_hook(payload: Box<dyn Any + Send>) -> ! {
|
|
panic_count::increase(false);
|
|
|
|
struct RewrapBox(Box<dyn Any + Send>);
|
|
|
|
unsafe impl PanicPayload 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
|
|
}
|
|
}
|
|
|
|
impl fmt::Display for RewrapBox {
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
f.write_str(payload_as_str(&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)]
|
|
#[cfg(not(feature = "panic_immediate_abort"))]
|
|
fn rust_panic(msg: &mut dyn PanicPayload) -> ! {
|
|
let code = unsafe { __rust_start_panic(msg) };
|
|
rtabort!("failed to initiate panic, error {code}")
|
|
}
|
|
|
|
#[cfg_attr(not(test), rustc_std_internal_symbol)]
|
|
#[cfg(feature = "panic_immediate_abort")]
|
|
fn rust_panic(_: &mut dyn PanicPayload) -> ! {
|
|
unsafe {
|
|
crate::intrinsics::abort();
|
|
}
|
|
}
|