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Rollup merge of #130077 - madsmtm:watchos-arm-unwind, r=workingjubilee

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Fix linking error when compiling for 32-bit watchOS

In https://github.com/rust-lang/rust/pull/124494 (or https://github.com/rust-lang/rust/pull/124748), I mistakenly conflated "not SjLj" to mean "ARM EHABI", which isn't true, 32-bit watchOS uses a third unwinding method called "DWARF CFI".

So this PR is effectively a revert of https://github.com/rust-lang/rust/pull/124494, with a few more comments explaining what's going on.

Fixes https://github.com/rust-lang/rust/issues/130071.

r? Mark-Simulacrum (since you reviewed the original)
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Jubilee 2024-09-11 15:53:22 -07:00 • committed by GitHub
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3 changed files with 18 additions and 14 deletions
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6
library/std/src/sys/personality/dwarf/eh.rs
View file

@ -54,10 +54,10 @@ pub enum EHAction {
Terminate,
}
/// 32-bit Apple ARM uses SjLj exceptions, except for watchOS.
/// 32-bit ARM Darwin platforms uses SjLj exceptions.
///
/// I.e. iOS and tvOS, as those are the only Apple OSes that used 32-bit ARM
/// devices.
/// The exception is watchOS armv7k (specifically that subarchitecture), which
/// instead uses DWARF Call Frame Information (CFI) unwinding.
///
/// <https://github.com/llvm/llvm-project/blob/llvmorg-18.1.4/clang/lib/Driver/ToolChains/Darwin.cpp#L3107-L3119>
pub const USING_SJLJ_EXCEPTIONS: bool =

13
library/std/src/sys/personality/gcc.rs
View file

@ -95,14 +95,15 @@ const UNWIND_DATA_REG: (i32, i32) = (4, 5); // a0, a1
cfg_if::cfg_if! {
if #[cfg(all(
target_arch = "arm",
not(all(target_vendor = "apple", not(target_os = "watchos"))),
not(target_os = "netbsd"),
))] {
target_arch = "arm",
not(target_vendor = "apple"),
not(target_os = "netbsd"),
))] {
/// personality fn called by [ARM EHABI][armeabi-eh]
///
/// Apple 32-bit ARM (but not watchOS) uses the default routine instead
/// since it uses "setjmp-longjmp" unwinding.
/// 32-bit ARM on iOS/tvOS/watchOS does not use ARM EHABI, it uses
/// either "setjmp-longjmp" unwinding or DWARF CFI unwinding, which is
/// handled by the default routine.
///
/// [armeabi-eh]: https://web.archive.org/web/20190728160938/https://infocenter.arm.com/help/topic/com.arm.doc.ihi0038b/IHI0038B_ehabi.pdf
#[lang = "eh_personality"]