| //! Panic support for libcore |
| //! |
| //! The core library cannot define panicking, but it does *declare* panicking. This |
| //! means that the functions inside of libcore are allowed to panic, but to be |
| //! useful an upstream crate must define panicking for libcore 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 libcore 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}; |
| |
| /// The underlying implementation of libcore's `panic!` macro when no formatting is used. |
| #[cold] |
| // 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))] |
| #[track_caller] |
| #[lang = "panic"] // needed by codegen for panic on overflow and other `Assert` MIR terminators |
| pub fn panic(expr: &'static str) -> ! { |
| if cfg!(feature = "panic_immediate_abort") { |
| super::intrinsics::abort() |
| } |
| |
| // 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], &[])); |
| } |
| |
| #[cold] |
| #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))] |
| #[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 {} but the index is {}", len, index) |
| } |
| |
| /// The underlying implementation of libcore's `panic!` macro when formatting is used. |
| #[cold] |
| #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))] |
| #[cfg_attr(feature = "panic_immediate_abort", inline)] |
| #[track_caller] |
| pub 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()); |
| |
| // SAFETY: `panic_impl` is defined in safe Rust code and thus is safe to call. |
| unsafe { panic_impl(&pi) } |
| } |