| //! Panic support for core |
| //! |
| //! The core library cannot define panicking, but it does *declare* panicking. This |
| //! means that the functions inside of core are allowed to panic, but to be |
| //! useful an upstream crate must define panicking for core to use. The current |
| //! interface for panicking is: |
| //! |
| //! ``` |
| //! fn panic_impl(pi: &core::panic::PanicInfo<'_>) -> ! |
| //! # { loop {} } |
| //! ``` |
| //! |
| //! This definition allows for panicking with any general message, but it does not |
| //! allow for failing with a `Box<Any>` value. (`PanicInfo` just contains a `&(dyn Any + Send)`, |
| //! for which we fill in a dummy value in `PanicInfo::internal_constructor`.) |
| //! The reason for this is that core is not allowed to allocate. |
| //! |
| //! This module contains a few other panicking functions, but these are just the |
| //! necessary lang items for the compiler. All panics are funneled through this |
| //! one function. The actual symbol is declared through the `#[panic_handler]` attribute. |
| |
| #![allow(dead_code, missing_docs)] |
| #![unstable( |
| feature = "core_panic", |
| reason = "internal details of the implementation of the `panic!` and related macros", |
| issue = "none" |
| )] |
| |
| use crate::fmt; |
| use crate::panic::{Location, PanicInfo}; |
| |
| // First we define the two main entry points that all panics go through. |
| // In the end both are just convenience wrappers around `panic_impl`. |
| |
| /// The entry point for panicking with a formatted message. |
| /// |
| /// This is designed to reduce the amount of code required at the call |
| /// site as much as possible (so that `panic!()` has as low an impact |
| /// on (e.g.) the inlining of other functions as possible), by moving |
| /// the actual formatting into this shared place. |
| // If panic_immediate_abort, inline the abort call, |
| // otherwise avoid inlining because of it is cold path. |
| #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)] |
| #[cfg_attr(feature = "panic_immediate_abort", inline)] |
| #[track_caller] |
| #[lang = "panic_fmt"] // needed for const-evaluated panics |
| #[rustc_do_not_const_check] // hooked by const-eval |
| #[rustc_const_unstable(feature = "core_panic", issue = "none")] |
| pub const fn panic_fmt(fmt: fmt::Arguments<'_>) -> ! { |
| if cfg!(feature = "panic_immediate_abort") { |
| super::intrinsics::abort() |
| } |
| |
| // NOTE This function never crosses the FFI boundary; it's a Rust-to-Rust call |
| // that gets resolved to the `#[panic_handler]` function. |
| extern "Rust" { |
| #[lang = "panic_impl"] |
| fn panic_impl(pi: &PanicInfo<'_>) -> !; |
| } |
| |
| let pi = PanicInfo::internal_constructor(Some(&fmt), Location::caller(), true); |
| |
| // SAFETY: `panic_impl` is defined in safe Rust code and thus is safe to call. |
| unsafe { panic_impl(&pi) } |
| } |
| |
| /// Like `panic_fmt`, but for non-unwinding panics. |
| /// |
| /// Has to be a separate function so that it can carry the `rustc_nounwind` attribute. |
| #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)] |
| #[cfg_attr(feature = "panic_immediate_abort", inline)] |
| #[track_caller] |
| // This attribute has the key side-effect that if the panic handler ignores `can_unwind` |
| // and unwinds anyway, we will hit the "unwinding out of nounwind function" guard, |
| // which causes a "panic in a function that cannot unwind". |
| #[rustc_nounwind] |
| pub fn panic_nounwind_fmt(fmt: fmt::Arguments<'_>) -> ! { |
| if cfg!(feature = "panic_immediate_abort") { |
| super::intrinsics::abort() |
| } |
| |
| // NOTE This function never crosses the FFI boundary; it's a Rust-to-Rust call |
| // that gets resolved to the `#[panic_handler]` function. |
| extern "Rust" { |
| #[lang = "panic_impl"] |
| fn panic_impl(pi: &PanicInfo<'_>) -> !; |
| } |
| |
| // PanicInfo with the `can_unwind` flag set to false forces an abort. |
| let pi = PanicInfo::internal_constructor(Some(&fmt), Location::caller(), false); |
| |
| // SAFETY: `panic_impl` is defined in safe Rust code and thus is safe to call. |
| unsafe { panic_impl(&pi) } |
| } |
| |
| // Next we define a bunch of higher-level wrappers that all bottom out in the two core functions |
| // above. |
| |
| /// The underlying implementation of core's `panic!` macro when no formatting is used. |
| // 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_const_unstable(feature = "core_panic", issue = "none")] |
| #[lang = "panic"] // needed by codegen for panic on overflow and other `Assert` MIR terminators |
| pub const fn panic(expr: &'static str) -> ! { |
| // Use Arguments::new_v1 instead of format_args!("{expr}") to potentially |
| // reduce size overhead. The format_args! macro uses str's Display trait to |
| // write expr, which calls Formatter::pad, which must accommodate string |
| // truncation and padding (even though none is used here). Using |
| // Arguments::new_v1 may allow the compiler to omit Formatter::pad from the |
| // output binary, saving up to a few kilobytes. |
| panic_fmt(fmt::Arguments::new_v1(&[expr], &[])); |
| } |
| |
| /// Like `panic`, but without unwinding and track_caller to reduce the impact on codesize. |
| #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)] |
| #[cfg_attr(feature = "panic_immediate_abort", inline)] |
| #[lang = "panic_nounwind"] // needed by codegen for non-unwinding panics |
| #[rustc_nounwind] |
| pub fn panic_nounwind(expr: &'static str) -> ! { |
| panic_nounwind_fmt(fmt::Arguments::new_v1(&[expr], &[])); |
| } |
| |
| #[inline] |
| #[track_caller] |
| #[rustc_diagnostic_item = "panic_str"] |
| #[rustc_const_unstable(feature = "core_panic", issue = "none")] |
| pub const fn panic_str(expr: &str) -> ! { |
| panic_display(&expr); |
| } |
| |
| #[inline] |
| #[track_caller] |
| #[rustc_diagnostic_item = "unreachable_display"] // needed for `non-fmt-panics` lint |
| pub fn unreachable_display<T: fmt::Display>(x: &T) -> ! { |
| panic_fmt(format_args!("internal error: entered unreachable code: {}", *x)); |
| } |
| |
| #[inline] |
| #[track_caller] |
| #[lang = "panic_display"] // needed for const-evaluated panics |
| #[rustc_do_not_const_check] // hooked by const-eval |
| #[rustc_const_unstable(feature = "core_panic", issue = "none")] |
| pub const fn panic_display<T: fmt::Display>(x: &T) -> ! { |
| panic_fmt(format_args!("{}", *x)); |
| } |
| |
| #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)] |
| #[cfg_attr(feature = "panic_immediate_abort", inline)] |
| #[track_caller] |
| #[lang = "panic_bounds_check"] // needed by codegen for panic on OOB array/slice access |
| fn panic_bounds_check(index: usize, len: usize) -> ! { |
| if cfg!(feature = "panic_immediate_abort") { |
| super::intrinsics::abort() |
| } |
| |
| panic!("index out of bounds: the len is {len} but the index is {index}") |
| } |
| |
| /// Panic because we cannot unwind out of a function. |
| /// |
| /// This function is called directly by the codegen backend, and must not have |
| /// any extra arguments (including those synthesized by track_caller). |
| #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)] |
| #[cfg_attr(feature = "panic_immediate_abort", inline)] |
| #[lang = "panic_cannot_unwind"] // needed by codegen for panic in nounwind function |
| #[rustc_nounwind] |
| fn panic_cannot_unwind() -> ! { |
| panic_nounwind("panic in a function that cannot unwind") |
| } |
| |
| /// This function is used instead of panic_fmt in const eval. |
| #[lang = "const_panic_fmt"] |
| #[rustc_const_unstable(feature = "core_panic", issue = "none")] |
| pub const fn const_panic_fmt(fmt: fmt::Arguments<'_>) -> ! { |
| if let Some(msg) = fmt.as_str() { |
| panic_str(msg); |
| } else { |
| // SAFETY: This is only evaluated at compile time, which reliably |
| // handles this UB (in case this branch turns out to be reachable |
| // somehow). |
| unsafe { crate::hint::unreachable_unchecked() }; |
| } |
| } |
| |
| #[derive(Debug)] |
| #[doc(hidden)] |
| pub enum AssertKind { |
| Eq, |
| Ne, |
| Match, |
| } |
| |
| /// Internal function for `assert_eq!` and `assert_ne!` macros |
| #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)] |
| #[cfg_attr(feature = "panic_immediate_abort", inline)] |
| #[track_caller] |
| #[doc(hidden)] |
| pub fn assert_failed<T, U>( |
| kind: AssertKind, |
| left: &T, |
| right: &U, |
| args: Option<fmt::Arguments<'_>>, |
| ) -> ! |
| where |
| T: fmt::Debug + ?Sized, |
| U: fmt::Debug + ?Sized, |
| { |
| assert_failed_inner(kind, &left, &right, args) |
| } |
| |
| /// Internal function for `assert_match!` |
| #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)] |
| #[cfg_attr(feature = "panic_immediate_abort", inline)] |
| #[track_caller] |
| #[doc(hidden)] |
| pub fn assert_matches_failed<T: fmt::Debug + ?Sized>( |
| left: &T, |
| right: &str, |
| args: Option<fmt::Arguments<'_>>, |
| ) -> ! { |
| // The pattern is a string so it can be displayed directly. |
| struct Pattern<'a>(&'a str); |
| impl fmt::Debug for Pattern<'_> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.write_str(self.0) |
| } |
| } |
| assert_failed_inner(AssertKind::Match, &left, &Pattern(right), args); |
| } |
| |
| /// Non-generic version of the above functions, to avoid code bloat. |
| #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)] |
| #[cfg_attr(feature = "panic_immediate_abort", inline)] |
| #[track_caller] |
| fn assert_failed_inner( |
| kind: AssertKind, |
| left: &dyn fmt::Debug, |
| right: &dyn fmt::Debug, |
| args: Option<fmt::Arguments<'_>>, |
| ) -> ! { |
| let op = match kind { |
| AssertKind::Eq => "==", |
| AssertKind::Ne => "!=", |
| AssertKind::Match => "matches", |
| }; |
| |
| match args { |
| Some(args) => panic!( |
| r#"assertion failed: `(left {} right)` |
| left: `{:?}`, |
| right: `{:?}`: {}"#, |
| op, left, right, args |
| ), |
| None => panic!( |
| r#"assertion failed: `(left {} right)` |
| left: `{:?}`, |
| right: `{:?}`"#, |
| op, left, right, |
| ), |
| } |
| } |