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Share _Unwind_Exception definition between native and wasm #159785

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5951005
Introduce types module for types shared between libunwind and wasm
bjorn3 Jul 10, 2026
46b319e
Remove a cfg_select! where the api doesn't change
bjorn3 Jul 10, 2026
f5260df
Remove aborting Emscripten personality function
bjorn3 Jul 19, 2026
0ccc68e
Remove a bunch of unused bindings from the unwind crate
bjorn3 Jul 19, 2026
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21 changes: 0 additions & 21 deletions library/std/src/sys/personality/emcc.rs
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This file was deleted.

3 changes: 0 additions & 3 deletions library/std/src/sys/personality/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,9 +14,6 @@ mod dwarf;

#[cfg(not(any(test, doctest)))]
cfg_select! {
target_os = "emscripten" => {
mod emcc;
}
any(target_env = "msvc", target_family = "wasm", target_os = "motor") => {
// This is required by the compiler to exist (e.g., it's a lang item),
// but it's never actually called by the compiler because
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2 changes: 2 additions & 0 deletions library/unwind/src/lib.rs
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Expand Up @@ -37,8 +37,10 @@ cfg_select! {
) => {
mod libunwind;
pub use libunwind::*;
mod types;
}
target_family = "wasm" => {
mod types;
mod wasm;
pub use wasm::*;
}
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120 changes: 17 additions & 103 deletions library/unwind/src/libunwind.rs
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Expand Up @@ -8,69 +8,12 @@ pub use unwinding::custom_eh_frame_finder::{
EhFrameFinder, FrameInfo, FrameInfoKind, set_custom_eh_frame_finder,
};

#[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 use crate::types::*;

pub type _Unwind_Exception_Class = u64;
pub type _Unwind_Word = *const u8;
pub type _Unwind_Ptr = *const u8;
pub type _Unwind_Trace_Fn =
extern "C" fn(ctx: *mut _Unwind_Context, arg: *mut c_void) -> _Unwind_Reason_Code;

pub const unwinder_private_data_size: usize = cfg_select! {
target_arch = "x86" => 5,
all(target_arch = "x86_64", not(any(target_os = "windows", target_os = "cygwin"))) => 2,
all(target_arch = "x86_64", any(target_os = "windows", target_os = "cygwin")) => 6,
all(target_arch = "arm", not(target_vendor = "apple")) => 20,
all(target_arch = "arm", target_vendor = "apple") => 5,
all(target_arch = "aarch64", target_pointer_width = "64", not(target_os = "windows")) => 2,
all(target_arch = "aarch64", target_pointer_width = "64", target_os = "windows") => 6,
all(target_arch = "aarch64", target_pointer_width = "32") => 5,
target_arch = "m68k" => 2,
any(target_arch = "mips", target_arch = "mips32r6") => 2,
target_arch = "csky" => 2,
any(target_arch = "mips64", target_arch = "mips64r6") => 2,
any(target_arch = "powerpc", target_arch = "powerpc64") => 2,
target_arch = "s390x" => 2,
any(target_arch = "sparc", target_arch = "sparc64") => 2,
any(target_arch = "riscv64", target_arch = "riscv32") => 2,
all(target_family = "wasm", target_os = "emscripten") => 20,
all(target_arch = "wasm32", any(target_os = "linux", target_os = "wasi")) => 2,
target_arch = "hexagon" => 5,
any(target_arch = "loongarch32", target_arch = "loongarch64") => 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],
}

// Check the size of _Unwind_Exception against the source of thruth when using the unwinding crate.
#[cfg(target_os = "xous")]
const _: () = {
assert!(size_of::<unwinding::abi::UnwindException>() == size_of::<_Unwind_Exception>());
};

pub enum _Unwind_Context {}

pub type _Unwind_Exception_Cleanup_Fn =
Option<extern "C" fn(unwind_code: _Unwind_Reason_Code, exception: *mut _Unwind_Exception)>;

// FIXME: The `#[link]` attributes on `extern "C"` block marks those symbols declared in
// the block are reexported in dylib build of std. This is needed when build rustc with
// feature `llvm-libunwind`, as no other cdylib will provided those _Unwind_* symbols.
Expand Down Expand Up @@ -110,10 +53,10 @@ cfg_select! {
pub type _Unwind_Action = c_int;

pub const _UA_SEARCH_PHASE: c_int = 1;
pub const _UA_CLEANUP_PHASE: c_int = 2;
pub const _UA_HANDLER_FRAME: c_int = 4;
//pub const _UA_CLEANUP_PHASE: c_int = 2;
//pub const _UA_HANDLER_FRAME: c_int = 4;
pub const _UA_FORCE_UNWIND: c_int = 8;
pub const _UA_END_OF_STACK: c_int = 16;
//pub const _UA_END_OF_STACK: c_int = 16;

#[cfg_attr(
all(feature = "llvm-libunwind", any(target_os = "fuchsia", target_os = "linux")),
Expand All @@ -122,11 +65,9 @@ cfg_select! {
unsafe extern "C" {
pub fn _Unwind_GetGR(ctx: *mut _Unwind_Context, reg_index: c_int) -> _Unwind_Word;
pub fn _Unwind_SetGR(ctx: *mut _Unwind_Context, reg_index: c_int, value: _Unwind_Word);
pub fn _Unwind_GetIP(ctx: *mut _Unwind_Context) -> _Unwind_Word;
pub fn _Unwind_SetIP(ctx: *mut _Unwind_Context, value: _Unwind_Word);
pub fn _Unwind_GetIPInfo(ctx: *mut _Unwind_Context, ip_before_insn: *mut c_int)
-> _Unwind_Word;
pub fn _Unwind_FindEnclosingFunction(pc: *mut c_void) -> *mut c_void;
}

}
Expand Down Expand Up @@ -213,12 +154,6 @@ cfg_select! {
(&raw mut value) as *mut c_void); }
}

pub unsafe fn _Unwind_GetIP(ctx: *mut _Unwind_Context)
-> _Unwind_Word {
let val = unsafe { _Unwind_GetGR(ctx, UNWIND_IP_REG) };
val.map_addr(|v| v & !1)
}

pub unsafe fn _Unwind_SetIP(ctx: *mut _Unwind_Context,
value: _Unwind_Word) {
// Propagate thumb bit to instruction pointer
Expand All @@ -232,45 +167,24 @@ cfg_select! {
-> _Unwind_Word {
unsafe {
*ip_before_insn = 0;
_Unwind_GetIP(ctx)
let val = unsafe { _Unwind_GetGR(ctx, UNWIND_IP_REG) };

@tmiasko tmiasko Jul 25, 2026 •
edited by rustbot
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   warning: unnecessary `unsafe` block
     --> /rustc/39f1d7da58b7277d3ac42f851507082654e56a2e/library/unwind/src/libunwind.rs:170:27
      |
  168 |             unsafe {
      |             ------ because it's nested under this `unsafe` block
  169 |                 *ip_before_insn = 0;
  170 |                 let val = unsafe { _Unwind_GetGR(ctx, UNWIND_IP_REG) };
      |                           ^^^^^^ unnecessary `unsafe` block

View changes since the review

val.map_addr(|v| v & !1)
}
}

// This function also doesn't exist on Android or ARM/Linux, so make it a no-op
pub unsafe fn _Unwind_FindEnclosingFunction(pc: *mut c_void) -> *mut c_void {
pc
}
}
}

cfg_select! {
all(target_vendor = "apple", not(target_os = "watchos"), target_arch = "arm") => {
// 32-bit ARM Apple (except for watchOS armv7k specifically) uses SjLj and
// does not provide _Unwind_Backtrace()
unsafe extern "C-unwind" {
pub fn _Unwind_SjLj_RaiseException(e: *mut _Unwind_Exception) -> _Unwind_Reason_Code;
}

pub use _Unwind_SjLj_RaiseException as _Unwind_RaiseException;
}
_ => {
#[cfg_attr(
all(feature = "llvm-libunwind", any(target_os = "fuchsia", target_os = "linux")),
link(name = "unwind", kind = "static", modifiers = "-bundle")
)]
unsafe extern "C-unwind" {
pub fn _Unwind_RaiseException(exception: *mut _Unwind_Exception) -> _Unwind_Reason_Code;
}
#[cfg_attr(
all(feature = "llvm-libunwind", any(target_os = "fuchsia", target_os = "linux")),
link(name = "unwind", kind = "static", modifiers = "-bundle")
)]
unsafe extern "C" {
pub fn _Unwind_Backtrace(trace: _Unwind_Trace_Fn,
trace_argument: *mut c_void)
-> _Unwind_Reason_Code;
}
}
#[cfg_attr(
all(feature = "llvm-libunwind", any(target_os = "fuchsia", target_os = "linux")),
link(name = "unwind", kind = "static", modifiers = "-bundle")
)]
unsafe extern "C-unwind" {
// 32-bit ARM Apple (except for watchOS armv7k specifically) uses SjLj
#[cfg_attr(
all(target_vendor = "apple", not(target_os = "watchos"), target_arch = "arm"),
link_name = "_Unwind_SjLj_RaiseException"
)]
pub fn _Unwind_RaiseException(exception: *mut _Unwind_Exception) -> _Unwind_Reason_Code;
}

cfg_select! {
Expand Down
59 changes: 59 additions & 0 deletions library/unwind/src/types.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,59 @@
#![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 = cfg_select! {
target_arch = "x86" => 5,
all(target_arch = "x86_64", not(any(target_os = "windows", target_os = "cygwin"))) => 2,
all(target_arch = "x86_64", any(target_os = "windows", target_os = "cygwin")) => 6,
all(target_arch = "arm", not(target_vendor = "apple")) => 20,
all(target_arch = "arm", target_vendor = "apple") => 5,
all(target_arch = "aarch64", target_pointer_width = "64", not(target_os = "windows")) => 2,
all(target_arch = "aarch64", target_pointer_width = "64", target_os = "windows") => 6,
all(target_arch = "aarch64", target_pointer_width = "32") => 5,
target_arch = "m68k" => 2,
any(target_arch = "mips", target_arch = "mips32r6") => 2,
target_arch = "csky" => 2,
any(target_arch = "mips64", target_arch = "mips64r6") => 2,
any(target_arch = "powerpc", target_arch = "powerpc64") => 2,
target_arch = "s390x" => 2,
any(target_arch = "sparc", target_arch = "sparc64") => 2,
any(target_arch = "riscv64", target_arch = "riscv32") => 2,
all(target_family = "wasm", target_os = "emscripten") => 20,
target_family = "wasm" => 2,
target_arch = "hexagon" => 5,
any(target_arch = "loongarch32", target_arch = "loongarch64") => 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],
}

// Check the size of _Unwind_Exception against the source of truth when using the unwinding crate.
#[cfg(target_os = "xous")]
const _: () = {
assert!(size_of::<unwinding::abi::UnwindException>() == size_of::<_Unwind_Exception>());
};

pub type _Unwind_Exception_Cleanup_Fn =
Option<extern "C" fn(unwind_code: _Unwind_Reason_Code, exception: *mut _Unwind_Exception)>;
31 changes: 1 addition & 30 deletions library/unwind/src/wasm.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,36 +26,7 @@ core::arch::global_asm!(
"__cpp_exception:",
);

#[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 use crate::types::*;

pub unsafe fn _Unwind_DeleteException(exception: *mut _Unwind_Exception) {
if let Some(exception_cleanup) = unsafe { (*exception).exception_cleanup } {
Expand Down
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