mirror of
https://github.com/rust-lang/rust.git
synced 2025-05-14 02:49:40 +00:00
65 lines
2.6 KiB
Rust
65 lines
2.6 KiB
Rust
//! A shim for libunwind implemented in terms of the native wasm `throw` instruction.
|
|
|
|
#![allow(nonstandard_style)]
|
|
|
|
#[repr(C)]
|
|
#[derive(Debug, Copy, Clone, PartialEq)]
|
|
pub enum _Unwind_Reason_Code {
|
|
_URC_NO_REASON = 0,
|
|
_URC_FOREIGN_EXCEPTION_CAUGHT = 1,
|
|
_URC_FATAL_PHASE2_ERROR = 2,
|
|
_URC_FATAL_PHASE1_ERROR = 3,
|
|
_URC_NORMAL_STOP = 4,
|
|
_URC_END_OF_STACK = 5,
|
|
_URC_HANDLER_FOUND = 6,
|
|
_URC_INSTALL_CONTEXT = 7,
|
|
_URC_CONTINUE_UNWIND = 8,
|
|
_URC_FAILURE = 9, // used only by ARM EHABI
|
|
}
|
|
pub use _Unwind_Reason_Code::*;
|
|
|
|
pub type _Unwind_Exception_Class = u64;
|
|
pub type _Unwind_Word = *const u8;
|
|
|
|
pub const unwinder_private_data_size: usize = 2;
|
|
|
|
#[repr(C)]
|
|
pub struct _Unwind_Exception {
|
|
pub exception_class: _Unwind_Exception_Class,
|
|
pub exception_cleanup: _Unwind_Exception_Cleanup_Fn,
|
|
pub private: [_Unwind_Word; unwinder_private_data_size],
|
|
}
|
|
|
|
pub type _Unwind_Exception_Cleanup_Fn =
|
|
Option<extern "C" fn(unwind_code: _Unwind_Reason_Code, exception: *mut _Unwind_Exception)>;
|
|
|
|
pub unsafe fn _Unwind_DeleteException(exception: *mut _Unwind_Exception) {
|
|
if let Some(exception_cleanup) = unsafe { (*exception).exception_cleanup } {
|
|
exception_cleanup(_URC_FOREIGN_EXCEPTION_CAUGHT, exception);
|
|
}
|
|
}
|
|
|
|
pub unsafe fn _Unwind_RaiseException(exception: *mut _Unwind_Exception) -> _Unwind_Reason_Code {
|
|
// The wasm `throw` instruction takes a "tag", which differentiates certain
|
|
// types of exceptions from others. LLVM currently just identifies these
|
|
// via integers, with 0 corresponding to C++ exceptions and 1 to C setjmp()/longjmp().
|
|
// Ideally, we'd be able to choose something unique for Rust, but for now,
|
|
// we pretend to be C++ and implement the Itanium exception-handling ABI.
|
|
cfg_if::cfg_if! {
|
|
// panic=abort is default for wasm targets. Because an unknown instruction is a load-time
|
|
// error on wasm, instead of a runtime error like on traditional architectures, we never
|
|
// want to codegen a `throw` instruction, as that would break users using runtimes that
|
|
// don't yet support exceptions. The only time this first branch would be selected is if
|
|
// the user explicitly opts in to wasm exceptions, via -Zbuild-std with -Cpanic=unwind.
|
|
if #[cfg(panic = "unwind")] {
|
|
// corresponds with llvm::WebAssembly::Tag::CPP_EXCEPTION
|
|
// in llvm-project/llvm/include/llvm/CodeGen/WasmEHFuncInfo.h
|
|
const CPP_EXCEPTION_TAG: i32 = 0;
|
|
core::arch::wasm::throw::<CPP_EXCEPTION_TAG>(exception.cast())
|
|
} else {
|
|
let _ = exception;
|
|
core::arch::wasm::unreachable()
|
|
}
|
|
}
|
|
}
|