From f20a6c70fb7a1b9bf1b855e6d1e711c1afd6bb48 Mon Sep 17 00:00:00 2001
From: Noratrieb <48135649+Noratrieb@users.noreply.github.com>
Date: Sun, 16 Mar 2025 21:32:41 +0100
Subject: [PATCH] make `_Unwind_Action` a type alias, not enum

It's bitflags in practice, so an enum is unsound, as an enum must only
have the described values. The x86_64 psABI declares it as a `typedef
int _Unwind_Action`, which seems reasonable. I made a newtype first but
that was more annoying than just a typedef. We don't really use this
value for much other than a short check.
---
 library/std/src/sys/personality/gcc.rs |  4 ++--
 library/unwind/src/libunwind.rs        | 17 +++++++----------
 library/unwind/src/unwinding.rs        | 17 +++++++----------
 3 files changed, 16 insertions(+), 22 deletions(-)

diff --git a/library/std/src/sys/personality/gcc.rs b/library/std/src/sys/personality/gcc.rs
index cd2c7899f4b..9a5b3b2fd19 100644
--- a/library/std/src/sys/personality/gcc.rs
+++ b/library/std/src/sys/personality/gcc.rs
@@ -220,7 +220,7 @@ cfg_if::cfg_if! {
                     Ok(action) => action,
                     Err(_) => return uw::_URC_FATAL_PHASE1_ERROR,
                 };
-                if actions as i32 & uw::_UA_SEARCH_PHASE as i32 != 0 {
+                if actions & uw::_UA_SEARCH_PHASE != 0 {
                     match eh_action {
                         EHAction::None | EHAction::Cleanup(_) => uw::_URC_CONTINUE_UNWIND,
                         EHAction::Catch(_) | EHAction::Filter(_) => uw::_URC_HANDLER_FOUND,
@@ -230,7 +230,7 @@ cfg_if::cfg_if! {
                     match eh_action {
                         EHAction::None => uw::_URC_CONTINUE_UNWIND,
                         // Forced unwinding hits a terminate action.
-                        EHAction::Filter(_) if actions as i32 & uw::_UA_FORCE_UNWIND as i32 != 0 => uw::_URC_CONTINUE_UNWIND,
+                        EHAction::Filter(_) if actions & uw::_UA_FORCE_UNWIND != 0 => uw::_URC_CONTINUE_UNWIND,
                         EHAction::Cleanup(lpad) | EHAction::Catch(lpad) | EHAction::Filter(lpad) => {
                             uw::_Unwind_SetGR(
                                 context,
diff --git a/library/unwind/src/libunwind.rs b/library/unwind/src/libunwind.rs
index 1a640bbde71..1283c8e3a01 100644
--- a/library/unwind/src/libunwind.rs
+++ b/library/unwind/src/libunwind.rs
@@ -125,16 +125,13 @@ if #[cfg(any(target_vendor = "apple", target_os = "netbsd", not(target_arch = "a
     //
     // 32-bit ARM on iOS/tvOS/watchOS use either DWARF/Compact unwinding or
     // "setjmp-longjmp" / SjLj unwinding.
-    #[repr(C)]
-    #[derive(Copy, Clone, PartialEq)]
-    pub enum _Unwind_Action {
-        _UA_SEARCH_PHASE = 1,
-        _UA_CLEANUP_PHASE = 2,
-        _UA_HANDLER_FRAME = 4,
-        _UA_FORCE_UNWIND = 8,
-        _UA_END_OF_STACK = 16,
-    }
-    pub use _Unwind_Action::*;
+    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_FORCE_UNWIND: c_int = 8;
+    pub const _UA_END_OF_STACK: c_int = 16;
 
     #[cfg_attr(
         all(feature = "llvm-libunwind", any(target_os = "fuchsia", target_os = "linux", target_os = "xous")),
diff --git a/library/unwind/src/unwinding.rs b/library/unwind/src/unwinding.rs
index 1b94005ab6c..ba425803303 100644
--- a/library/unwind/src/unwinding.rs
+++ b/library/unwind/src/unwinding.rs
@@ -2,16 +2,13 @@
 
 use core::ffi::{c_int, c_void};
 
-#[repr(C)]
-#[derive(Copy, Clone, PartialEq)]
-pub enum _Unwind_Action {
-    _UA_SEARCH_PHASE = 1,
-    _UA_CLEANUP_PHASE = 2,
-    _UA_HANDLER_FRAME = 4,
-    _UA_FORCE_UNWIND = 8,
-    _UA_END_OF_STACK = 16,
-}
-pub use _Unwind_Action::*;
+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_FORCE_UNWIND: c_int = 8;
+pub const _UA_END_OF_STACK: c_int = 16;
 
 #[repr(C)]
 #[derive(Debug, Copy, Clone, PartialEq)]