1 //! Panic support for libcore
3 //! The core library cannot define panicking, but it does *declare* panicking. This
4 //! means that the functions inside of libcore are allowed to panic, but to be
5 //! useful an upstream crate must define panicking for libcore to use. The current
6 //! interface for panicking is:
10 //! fn panic_impl(fmt: fmt::Arguments, file_line_col: &(&'static str, u32, u32)) -> !
14 //! This definition allows for panicking with any general message, but it does not
15 //! allow for failing with a `Box<Any>` value. The reason for this is that libcore
16 //! is not allowed to allocate.
18 //! This module contains a few other panicking functions, but these are just the
19 //! necessary lang items for the compiler. All panics are funneled through this
20 //! one function. Currently, the actual symbol is declared in the standard
21 //! library, but the location of this may change over time.
23 #![allow(dead_code, missing_docs)]
24 #![unstable(feature = "core_panic",
25 reason = "internal details of the implementation of the `panic!` \
30 use panic::{Location, PanicInfo};
33 // never inline unless panic_immediate_abort to avoid code
34 // bloat at the call sites as much as possible
35 #[cfg_attr(not(feature="panic_immediate_abort"),inline(never))]
37 pub fn panic(expr_file_line_col: &(&'static str, &'static str, u32, u32)) -> ! {
38 if cfg!(feature = "panic_immediate_abort") {
39 unsafe { super::intrinsics::abort() }
42 // Use Arguments::new_v1 instead of format_args!("{}", expr) to potentially
43 // reduce size overhead. The format_args! macro uses str's Display trait to
44 // write expr, which calls Formatter::pad, which must accommodate string
45 // truncation and padding (even though none is used here). Using
46 // Arguments::new_v1 may allow the compiler to omit Formatter::pad from the
47 // output binary, saving up to a few kilobytes.
48 let (expr, file, line, col) = *expr_file_line_col;
49 panic_fmt(fmt::Arguments::new_v1(&[expr], &[]), &(file, line, col))
53 #[cfg_attr(not(feature="panic_immediate_abort"),inline(never))]
54 #[lang = "panic_bounds_check"]
55 fn panic_bounds_check(file_line_col: &(&'static str, u32, u32),
56 index: usize, len: usize) -> ! {
57 if cfg!(feature = "panic_immediate_abort") {
58 unsafe { super::intrinsics::abort() }
61 panic_fmt(format_args!("index out of bounds: the len is {} but the index is {}",
62 len, index), file_line_col)
66 #[cfg_attr(not(feature="panic_immediate_abort"),inline(never))]
67 #[cfg_attr( feature="panic_immediate_abort" ,inline)]
68 pub fn panic_fmt(fmt: fmt::Arguments, file_line_col: &(&'static str, u32, u32)) -> ! {
69 if cfg!(feature = "panic_immediate_abort") {
70 unsafe { super::intrinsics::abort() }
73 // NOTE This function never crosses the FFI boundary; it's a Rust-to-Rust call
74 #[allow(improper_ctypes)] // PanicInfo contains a trait object which is not FFI safe
76 #[lang = "panic_impl"]
77 fn panic_impl(pi: &PanicInfo) -> !;
80 let (file, line, col) = *file_line_col;
81 let pi = PanicInfo::internal_constructor(
83 Location::internal_constructor(file, line, col),
85 unsafe { panic_impl(&pi) }