library/panic_unwind/src/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(issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/")]
  17 #![feature(core_intrinsics)]
  18 #![feature(lang_items)]
  19 #![feature(nll)]
  20 #![feature(panic_unwind)]
  21 #![feature(staged_api)]
  22 #![feature(std_internals)]
  23 #![feature(unwind_attributes)]
  24 #![feature(abi_thiscall)]
  25 #![feature(rustc_attrs)]
  26 #![panic_runtime]
  27 #![feature(panic_runtime)]
  28 // `real_imp` is unused with Miri, so silence warnings.
  29 #![cfg_attr(miri, allow(dead_code))]
  30
  31 use alloc::boxed::Box;
  32 use core::any::Any;
  33 use core::panic::BoxMeUp;
  34
  35 cfg_if::cfg_if! {
  36     if #[cfg(target_os = "emscripten")] {
  37         #[path = "emcc.rs"]
  38         mod real_imp;
  39     } else if #[cfg(target_os = "hermit")] {
  40         #[path = "hermit.rs"]
  41         mod real_imp;
  42     } else if #[cfg(target_env = "msvc")] {
  43         #[path = "seh.rs"]
  44         mod real_imp;
  45     } else if #[cfg(any(
  46         all(target_family = "windows", target_env = "gnu"),
  47         target_os = "psp",
  48         target_family = "unix",
  49         all(target_vendor = "fortanix", target_env = "sgx"),
  50     ))] {
  51         // Rust runtime's startup objects depend on these symbols, so make them public.
  52         #[cfg(all(target_os="windows", target_arch = "x86", target_env="gnu"))]
  53         pub use real_imp::eh_frame_registry::*;
  54         #[path = "gcc.rs"]
  55         mod real_imp;
  56     } else {
  57         // Targets that don't support unwinding.
  58         // - arch=wasm32
  59         // - os=none ("bare metal" targets)
  60         // - os=uefi
  61         // - nvptx64-nvidia-cuda
  62         // - arch=avr
  63         #[path = "dummy.rs"]
  64         mod real_imp;
  65     }
  66 }
  67
  68 cfg_if::cfg_if! {
  69     if #[cfg(miri)] {
  70         // Use the Miri runtime.
  71         // We still need to also load the normal runtime above, as rustc expects certain lang
  72         // items from there to be defined.
  73         #[path = "miri.rs"]
  74         mod imp;
  75     } else {
  76         // Use the real runtime.
  77         use real_imp as imp;
  78     }
  79 }
  80
  81 extern "C" {
  82     /// Handler in libstd called when a panic object is dropped outside of
  83     /// `catch_unwind`.
  84     fn __rust_drop_panic() -> !;
  85
  86     /// Handler in libstd called when a foreign exception is caught.
  87     fn __rust_foreign_exception() -> !;
  88 }
  89
  90 mod dwarf;
  91
  92 #[rustc_std_internal_symbol]
  93 #[allow(improper_ctypes_definitions)]
  94 pub unsafe extern "C" fn __rust_panic_cleanup(payload: *mut u8) -> *mut (dyn Any + Send + 'static) {
  95     Box::into_raw(imp::cleanup(payload))
  96 }
  97
  98 // Entry point for raising an exception, just delegates to the platform-specific
  99 // implementation.
 100 #[rustc_std_internal_symbol]
 101 #[unwind(allowed)]
 102 pub unsafe extern "C" fn __rust_start_panic(payload: *mut &mut dyn BoxMeUp) -> u32 {
 103     let payload = Box::from_raw((*payload).take_box());
 104
 105     imp::panic(payload)
 106 }