src/libpanic_unwind/lib.rs

   1 //! Implementation of panics via stack unwinding
   2 //!
   3 //! This crate is an implementation of panics in Rust using "most native" stack
   4 //! unwinding mechanism of the platform this is being compiled for. This
   5 //! essentially gets categorized into three buckets currently:
   6 //!
   7 //! 1. MSVC targets use SEH in the `seh.rs` file.
   8 //! 2. Emscripten uses C++ exceptions in the `emcc.rs` file.
   9 //! 3. All other targets use libunwind/libgcc in the `gcc.rs` file.
  10 //!
  11 //! More documentation about each implementation can be found in the respective
  12 //! module.
  13
  14 #![no_std]
  15 #![unstable(feature = "panic_unwind", issue = "32837")]
  16 #![doc(
  17     html_root_url = "https://doc.rust-lang.org/nightly/",
  18     issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/"
  19 )]
  20 #![feature(core_intrinsics)]
  21 #![feature(lang_items)]
  22 #![feature(libc)]
  23 #![feature(nll)]
  24 #![feature(panic_unwind)]
  25 #![feature(staged_api)]
  26 #![feature(std_internals)]
  27 #![feature(unwind_attributes)]
  28 #![feature(abi_thiscall)]
  29 #![feature(rustc_attrs)]
  30 #![feature(raw)]
  31 #![panic_runtime]
  32 #![feature(panic_runtime)]
  33 // `real_imp` is unused with Miri, so silence warnings.
  34 #![cfg_attr(miri, allow(dead_code))]
  35
  36 use alloc::boxed::Box;
  37 use core::any::Any;
  38 use core::panic::BoxMeUp;
  39
  40 cfg_if::cfg_if! {
  41     if #[cfg(target_os = "emscripten")] {
  42         #[path = "emcc.rs"]
  43         mod real_imp;
  44     } else if #[cfg(target_arch = "wasm32")] {
  45         #[path = "dummy.rs"]
  46         mod real_imp;
  47     } else if #[cfg(target_os = "hermit")] {
  48         #[path = "hermit.rs"]
  49         mod real_imp;
  50     } else if #[cfg(target_env = "msvc")] {
  51         #[path = "seh.rs"]
  52         mod real_imp;
  53     } else {
  54         // Rust runtime's startup objects depend on these symbols, so make them public.
  55         #[cfg(all(target_os="windows", target_arch = "x86", target_env="gnu"))]
  56         pub use real_imp::eh_frame_registry::*;
  57         #[path = "gcc.rs"]
  58         mod real_imp;
  59     }
  60 }
  61
  62 cfg_if::cfg_if! {
  63     if #[cfg(miri)] {
  64         // Use the Miri runtime.
  65         // We still need to also load the normal runtime above, as rustc expects certain lang
  66         // items from there to be defined.
  67         #[path = "miri.rs"]
  68         mod imp;
  69     } else {
  70         // Use the real runtime.
  71         use real_imp as imp;
  72     }
  73 }
  74
  75 extern "C" {
  76     /// Handler in libstd called when a panic object is dropped outside of
  77     /// `catch_unwind`.
  78     fn __rust_drop_panic() -> !;
  79 }
  80
  81 mod dwarf;
  82
  83 #[rustc_std_internal_symbol]
  84 pub unsafe extern "C" fn __rust_panic_cleanup(payload: *mut u8) -> *mut (dyn Any + Send + 'static) {
  85     Box::into_raw(imp::cleanup(payload))
  86 }
  87
  88 // Entry point for raising an exception, just delegates to the platform-specific
  89 // implementation.
  90 #[rustc_std_internal_symbol]
  91 #[unwind(allowed)]
  92 pub unsafe extern "C" fn __rust_start_panic(payload: usize) -> u32 {
  93     let payload = payload as *mut &mut dyn BoxMeUp;
  94     let payload = (*payload).take_box();
  95
  96     imp::panic(Box::from_raw(payload))
  97 }