mirror of https://github.com/rust-lang/rust
69 lines
2.4 KiB
Rust
69 lines
2.4 KiB
Rust
//! A shim for libunwind implemented in terms of the native wasm `throw` instruction.
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#![allow(nonstandard_style)]
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#[repr(C)]
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#[derive(Debug, Copy, Clone, PartialEq)]
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pub enum _Unwind_Reason_Code {
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_URC_NO_REASON = 0,
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_URC_FOREIGN_EXCEPTION_CAUGHT = 1,
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_URC_FATAL_PHASE2_ERROR = 2,
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_URC_FATAL_PHASE1_ERROR = 3,
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_URC_NORMAL_STOP = 4,
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_URC_END_OF_STACK = 5,
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_URC_HANDLER_FOUND = 6,
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_URC_INSTALL_CONTEXT = 7,
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_URC_CONTINUE_UNWIND = 8,
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_URC_FAILURE = 9, // used only by ARM EHABI
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}
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pub use _Unwind_Reason_Code::*;
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pub type _Unwind_Exception_Class = u64;
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pub type _Unwind_Word = *const u8;
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pub const unwinder_private_data_size: usize = 2;
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#[repr(C)]
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pub struct _Unwind_Exception {
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pub exception_class: _Unwind_Exception_Class,
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pub exception_cleanup: _Unwind_Exception_Cleanup_Fn,
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pub private: [_Unwind_Word; unwinder_private_data_size],
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}
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pub type _Unwind_Exception_Cleanup_Fn =
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Option<extern "C" fn(unwind_code: _Unwind_Reason_Code, exception: *mut _Unwind_Exception)>;
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pub unsafe fn _Unwind_DeleteException(exception: *mut _Unwind_Exception) {
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if let Some(exception_cleanup) = unsafe { (*exception).exception_cleanup } {
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exception_cleanup(_URC_FOREIGN_EXCEPTION_CAUGHT, exception);
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}
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}
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pub unsafe fn _Unwind_RaiseException(exception: *mut _Unwind_Exception) -> _Unwind_Reason_Code {
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#[cfg(panic = "unwind")]
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extern "C" {
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/// LLVM lowers this intrinsic to the `throw` instruction.
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// FIXME(coolreader18): move to stdarch
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#[link_name = "llvm.wasm.throw"]
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fn wasm_throw(tag: i32, ptr: *mut u8) -> !;
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}
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// The wasm `throw` instruction takes a "tag", which differentiates certain
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// types of exceptions from others. LLVM currently just identifies these
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// via integers, with 0 corresponding to C++ exceptions and 1 to C setjmp()/longjmp().
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// Ideally, we'd be able to choose something unique for Rust, but for now,
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// we pretend to be C++ and implement the Itanium exception-handling ABI.
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cfg_if::cfg_if! {
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// for now, unless we're -Zbuild-std with panic=unwind, never codegen a throw.
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if #[cfg(panic = "unwind")] {
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wasm_throw(0, exception.cast())
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} else {
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let _ = exception;
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#[cfg(target_arch = "wasm32")]
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core::arch::wasm32::unreachable();
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#[cfg(target_arch = "wasm64")]
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core::arch::wasm64::unreachable();
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}
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}
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}
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