rust/src/libcore/failure.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.

//! Failure support for libcore
//!
//! The core library cannot define failure, but it does *declare* failure. This
//! means that the functions inside of libcore are allowed to fail, but to be
//! useful an upstream crate must define failure for libcore to use. The current
//! interface for failure is:
//!
//!     fn begin_unwind(fmt: &fmt::Arguments, file: &str, line: uint) -> !;
//!
//! This definition allows for failing with any general message, but it does not
//! allow for failing with a `~Any` value. The reason for this is that libcore
//! is not allowed to allocate.
//!
//! This module contains a few other failure functions, but these are just the
//! necessary lang items for the compiler. All failure is 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_doc)]

#[cfg(not(test))]
use str::raw::c_str_to_static_slice;
use fmt;

#[cold] #[inline(never)] // this is the slow path, always
#[lang="fail_"]
#[cfg(not(test))]
fn fail_(expr: *u8, file: *u8, line: uint) -> ! {
    unsafe {
        let expr = c_str_to_static_slice(expr as *i8);
        let file = c_str_to_static_slice(file as *i8);
        format_args!(|args| -> () {
            begin_unwind(args, file, line);
        }, "{}", expr);

        loop {}
    }
}

#[cold]
#[lang="fail_bounds_check"]
#[cfg(not(test))]
fn fail_bounds_check(file: *u8, line: uint, index: uint, len: uint) -> ! {
    let file = unsafe { c_str_to_static_slice(file as *i8) };
    format_args!(|args| -> () {
        begin_unwind(args, file, line);
    }, "index out of bounds: the len is {} but the index is {}", len, index);
    loop {}
}

#[cold]
pub fn begin_unwind(fmt: &fmt::Arguments, file: &'static str, line: uint) -> ! {
    // FIXME: this should be a proper lang item, it should not just be some
    //        undefined symbol sitting in the middle of nowhere.
    #[allow(ctypes)]
    extern { fn rust_begin_unwind(fmt: &fmt::Arguments, file: &'static str,
                                  line: uint) -> !; }
    unsafe { rust_begin_unwind(fmt, file, line) }
}