src/libcore/panicking.rs

// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! 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:
//!
//! ```ignore
//! fn panic_impl(fmt: fmt::Arguments, &(&'static str, uint)) -> !;
//! ```
//!
//! This definition allows for panicking with any general message, but it does not
//! allow for failing with a `Box<Any>` value. 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. Currently, the actual symbol is declared in the standard
//! library, but the location of this may change over time.

#![allow(dead_code, missing_docs)]

use fmt;

#[cold] #[inline(never)] // this is the slow path, always
#[lang="panic"]
pub fn panic(expr_file_line: &(&'static str, &'static str, uint)) -> ! {
    let (expr, file, line) = *expr_file_line;
    panic_fmt(format_args!("{}", expr), &(file, line))
}

#[cold] #[inline(never)]
#[lang="panic_bounds_check"]
fn panic_bounds_check(file_line: &(&'static str, uint),
                     index: uint, len: uint) -> ! {
    panic_fmt(format_args!("index out of bounds: the len is {} but the index is {}",
                           len, index), file_line)
}

#[cold] #[inline(never)]
pub fn panic_fmt(fmt: fmt::Arguments, file_line: &(&'static str, uint)) -> ! {
    #[allow(improper_ctypes)]
    extern {
        #[lang = "panic_fmt"]
        fn panic_impl(fmt: fmt::Arguments, file: &'static str, line: uint) -> !;
    }
    let (file, line) = *file_line;
    unsafe { panic_impl(fmt, file, line) }
}