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@@ -16,6 +16,33 @@ use frame::Frame;
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#[cfg(feature = "fde-custom")]
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pub use find_fde::custom_eh_frame_finder;
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+// Helper function to turn `save_context` which takes function pointer to a closure-taking function.
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+fn with_context<T, F: FnOnce(&mut Context) -> T>(f: F) -> T {
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+ use core::mem::ManuallyDrop;
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+
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+ union Data<T, F> {
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+ f: ManuallyDrop<F>,
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+ t: ManuallyDrop<T>,
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+ }
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+
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+ extern "C" fn delegate<T, F: FnOnce(&mut Context) -> T>(ctx: &mut Context, ptr: *mut ()) {
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+ // SAFETY: This function is called exactly once; it extracts the function, call it and
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+ // store the return value. This function is `extern "C"` so we don't need to worry about
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+ // unwinding past it.
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+ unsafe {
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+ let data = &mut *ptr.cast::<Data<T, F>>();
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+ let t = ManuallyDrop::take(&mut data.f)(ctx);
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+ data.t = ManuallyDrop::new(t);
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+ }
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+ }
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+
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+ let mut data = Data {
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+ f: ManuallyDrop::new(f),
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+ };
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+ save_context(delegate::<T, F>, ptr::addr_of_mut!(data).cast());
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+ unsafe { ManuallyDrop::into_inner(data.t) }
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+}
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+
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#[repr(C)]
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pub struct UnwindException {
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pub exception_class: u64,
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@@ -125,53 +152,52 @@ macro_rules! try2 {
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pub extern "C-unwind" fn _Unwind_RaiseException(
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exception: &mut UnwindException,
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) -> UnwindReasonCode {
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- let saved_ctx = save_context();
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-
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- // Phase 1: Search for handler
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- let mut ctx = saved_ctx.clone();
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- let mut signal = false;
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- loop {
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- if let Some(frame) = try1!(Frame::from_context(&ctx, signal)) {
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- if let Some(personality) = frame.personality() {
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- let result = personality(
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- 1,
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- UnwindAction::SEARCH_PHASE,
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- exception.exception_class,
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- exception,
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- &mut UnwindContext {
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- frame: Some(&frame),
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- ctx: &mut ctx,
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- signal,
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- },
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- );
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-
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- match result {
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- UnwindReasonCode::CONTINUE_UNWIND => (),
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- UnwindReasonCode::HANDLER_FOUND => {
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- break;
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+ with_context(|saved_ctx| {
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+ // Phase 1: Search for handler
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+ let mut ctx = saved_ctx.clone();
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+ let mut signal = false;
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+ loop {
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+ if let Some(frame) = try1!(Frame::from_context(&ctx, signal)) {
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+ if let Some(personality) = frame.personality() {
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+ let result = personality(
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+ 1,
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+ UnwindAction::SEARCH_PHASE,
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+ exception.exception_class,
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+ exception,
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+ &mut UnwindContext {
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+ frame: Some(&frame),
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+ ctx: &mut ctx,
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+ signal,
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+ },
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+ );
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+
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+ match result {
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+ UnwindReasonCode::CONTINUE_UNWIND => (),
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+ UnwindReasonCode::HANDLER_FOUND => {
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+ break;
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+ }
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+ _ => return UnwindReasonCode::FATAL_PHASE1_ERROR,
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}
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- _ => return UnwindReasonCode::FATAL_PHASE1_ERROR,
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}
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- }
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- ctx = try1!(frame.unwind(&ctx));
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- signal = frame.is_signal_trampoline();
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- } else {
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- return UnwindReasonCode::END_OF_STACK;
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+ ctx = try1!(frame.unwind(&ctx));
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+ signal = frame.is_signal_trampoline();
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+ } else {
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+ return UnwindReasonCode::END_OF_STACK;
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+ }
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}
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- }
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- // Disambiguate normal frame and signal frame.
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- let handler_cfa = ctx[Arch::SP] - signal as usize;
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- exception.private_1 = None;
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- exception.private_2 = handler_cfa;
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+ // Disambiguate normal frame and signal frame.
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+ let handler_cfa = ctx[Arch::SP] - signal as usize;
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+ exception.private_1 = None;
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+ exception.private_2 = handler_cfa;
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- let mut ctx = saved_ctx;
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- let code = raise_exception_phase2(exception, &mut ctx, handler_cfa);
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- match code {
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- UnwindReasonCode::INSTALL_CONTEXT => unsafe { restore_context(&ctx) },
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- _ => code,
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- }
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+ let code = raise_exception_phase2(exception, saved_ctx, handler_cfa);
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+ match code {
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+ UnwindReasonCode::INSTALL_CONTEXT => unsafe { restore_context(saved_ctx) },
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+ _ => code,
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+ }
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+ })
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}
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fn raise_exception_phase2(
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@@ -225,16 +251,16 @@ pub extern "C-unwind" fn _Unwind_ForcedUnwind(
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stop: UnwindStopFn,
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stop_arg: *mut c_void,
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) -> UnwindReasonCode {
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- let mut ctx = save_context();
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+ with_context(|ctx| {
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+ exception.private_1 = Some(stop);
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+ exception.private_2 = stop_arg as _;
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- exception.private_1 = Some(stop);
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- exception.private_2 = stop_arg as _;
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-
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- let code = force_unwind_phase2(exception, &mut ctx, stop, stop_arg);
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- match code {
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- UnwindReasonCode::INSTALL_CONTEXT => unsafe { restore_context(&ctx) },
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- _ => code,
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- }
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+ let code = force_unwind_phase2(exception, ctx, stop, stop_arg);
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+ match code {
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+ UnwindReasonCode::INSTALL_CONTEXT => unsafe { restore_context(ctx) },
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+ _ => code,
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+ }
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+ })
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}
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fn force_unwind_phase2(
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@@ -304,21 +330,21 @@ fn force_unwind_phase2(
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#[inline(never)]
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#[no_mangle]
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pub extern "C-unwind" fn _Unwind_Resume(exception: &mut UnwindException) -> ! {
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- let mut ctx = save_context();
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-
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- let code = match exception.private_1 {
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- None => {
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- let handler_cfa = exception.private_2;
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- raise_exception_phase2(exception, &mut ctx, handler_cfa)
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- }
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- Some(stop) => {
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- let stop_arg = exception.private_2 as _;
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- force_unwind_phase2(exception, &mut ctx, stop, stop_arg)
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- }
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- };
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- assert!(code == UnwindReasonCode::INSTALL_CONTEXT);
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+ with_context(|ctx| {
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+ let code = match exception.private_1 {
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+ None => {
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+ let handler_cfa = exception.private_2;
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+ raise_exception_phase2(exception, ctx, handler_cfa)
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+ }
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+ Some(stop) => {
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+ let stop_arg = exception.private_2 as _;
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+ force_unwind_phase2(exception, ctx, stop, stop_arg)
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+ }
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+ };
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+ assert!(code == UnwindReasonCode::INSTALL_CONTEXT);
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- unsafe { restore_context(&ctx) }
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+ unsafe { restore_context(ctx) }
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+ })
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}
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#[inline(never)]
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@@ -331,13 +357,13 @@ pub extern "C-unwind" fn _Unwind_Resume_or_Rethrow(
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Some(v) => v,
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};
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- let mut ctx = save_context();
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+ with_context(|ctx| {
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+ let stop_arg = exception.private_2 as _;
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+ let code = force_unwind_phase2(exception, ctx, stop, stop_arg);
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+ assert!(code == UnwindReasonCode::INSTALL_CONTEXT);
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- let stop_arg = exception.private_2 as _;
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- let code = force_unwind_phase2(exception, &mut ctx, stop, stop_arg);
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- assert!(code == UnwindReasonCode::INSTALL_CONTEXT);
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-
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- unsafe { restore_context(&ctx) }
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+ unsafe { restore_context(ctx) }
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+ })
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}
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#[no_mangle]
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@@ -353,36 +379,38 @@ pub extern "C-unwind" fn _Unwind_Backtrace(
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trace: UnwindTraceFn,
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trace_argument: *mut c_void,
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) -> UnwindReasonCode {
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- let mut ctx = save_context();
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- let mut signal = false;
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- let mut skipping = cfg!(feature = "hide-trace");
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-
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- loop {
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- let frame = try1!(Frame::from_context(&ctx, signal));
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- if !skipping {
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- let code = trace(
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- &mut UnwindContext {
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- frame: frame.as_ref(),
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- ctx: &mut ctx,
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- signal,
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- },
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- trace_argument,
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- );
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- match code {
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- UnwindReasonCode::NO_REASON => (),
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- _ => return UnwindReasonCode::FATAL_PHASE1_ERROR,
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+ with_context(|ctx| {
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+ let mut ctx = ctx.clone();
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+ let mut signal = false;
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+ let mut skipping = cfg!(feature = "hide-trace");
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+
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+ loop {
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+ let frame = try1!(Frame::from_context(&ctx, signal));
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+ if !skipping {
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+ let code = trace(
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+ &mut UnwindContext {
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+ frame: frame.as_ref(),
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+ ctx: &mut ctx,
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+ signal,
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+ },
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+ trace_argument,
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+ );
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+ match code {
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+ UnwindReasonCode::NO_REASON => (),
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+ _ => return UnwindReasonCode::FATAL_PHASE1_ERROR,
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+ }
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}
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- }
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- if let Some(frame) = frame {
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- if skipping {
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- if frame.initial_address() == _Unwind_Backtrace as usize {
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- skipping = false;
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+ if let Some(frame) = frame {
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+ if skipping {
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+ if frame.initial_address() == _Unwind_Backtrace as usize {
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+ skipping = false;
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+ }
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}
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+ ctx = try1!(frame.unwind(&ctx));
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+ signal = frame.is_signal_trampoline();
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+ } else {
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+ return UnwindReasonCode::END_OF_STACK;
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}
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- ctx = try1!(frame.unwind(&ctx));
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- signal = frame.is_signal_trampoline();
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- } else {
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- return UnwindReasonCode::END_OF_STACK;
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}
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- }
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+ })
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}
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Gary Guo