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| Original file line number | Diff line number | Diff line change |
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| // This file is part of libfringe, a low-level green threading library. | ||
| // Copyright (c) Amanieu d'Antras <amanieu@gmail.com>, | ||
| // Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or | ||
| // http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or | ||
| // http://opensource.org/licenses/MIT>, at your option. This file may not be | ||
| // copied, modified, or distributed except according to those terms. | ||
| extern crate std; | ||
|
|
||
| use self::std::panic; | ||
| use self::std::boxed::Box; | ||
| use core::any::Any; | ||
| use arch::StackPointer; | ||
|
|
||
| // Marker object that is passed through the stack unwinding | ||
| struct UnwindMarker { | ||
| // We use the CFA address as an identifier so that nested generators are handled | ||
| // correctly. When unwinding, we will want to continue through any number of | ||
| // nested generators until we reach the one identified with a matching CFA address. | ||
| cfa_addr: *mut usize, | ||
| } | ||
| unsafe impl Send for UnwindMarker {} | ||
|
|
||
| // Whether the current platform support unwinding across multiple stacks. | ||
| fn have_cross_stack_unwind() -> bool { | ||
| // - Windows uses SEH for unwinding instead of libunwind. While it may be | ||
| // possible to munge it so support cross-stack unwinding, we stay conservative | ||
| // for now. | ||
| // - iOS on ARM uses setjmp/longjmp instead of DWARF-2 unwinding, which needs | ||
| // to be explicitly saved/restored when switching contexts. | ||
| !(cfg!(windows) || cfg!(all(target_os = "ios", target_arch = "arm"))) | ||
| } | ||
|
|
||
| // Wrapper around the root function of a generator which handles unwinding. | ||
| pub unsafe extern "C" fn unwind_wrapper(arg: usize, sp: StackPointer, cfa_addr: *mut usize, | ||
| f: unsafe fn(usize, StackPointer)) -> Option<Box<Box<Any + Send>>> { | ||
| // Catch any attempts to unwind out of the context. | ||
| match panic::catch_unwind(move || f(arg, sp)) { | ||
| Ok(_) => None, | ||
| Err(err) => { | ||
| // If the unwinding is due to an UnwindMarker, check whether it is intended | ||
| // for us by comparing the CFA of the caller with ours. If it is the same | ||
| // then we can swallow the exception and return to the caller normally. | ||
| if let Some(marker) = err.downcast_ref::<UnwindMarker>() { | ||
| if marker.cfa_addr == cfa_addr { | ||
| return None; | ||
| } | ||
| } | ||
|
|
||
| // Otherwise, propagate the panic to the parent context. | ||
| if have_cross_stack_unwind() { | ||
| panic::resume_unwind(err) | ||
| } else { | ||
| // The assembly code will call start_unwind in the parent context and | ||
| // pass it this Box as parameter. | ||
| Some(Box::new(err)) | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| // Called by asm to start unwinding in the current context with the given | ||
| // exception object. | ||
| pub unsafe extern "C" fn start_unwind(panic: Box<Box<Any + Send>>) -> ! { | ||
| // Use resume_unwind instead of panic! to avoid printing a message. | ||
| panic::resume_unwind(*panic) | ||
| } | ||
|
|
||
| // Get the initial argument to pass to start_unwind, keyed to the address of the | ||
| // CFA slot on the generator stack that is going to be unwound. | ||
| pub fn unwind_arg(cfa_addr: *mut usize) -> usize { | ||
| let marker = UnwindMarker { | ||
| cfa_addr: cfa_addr | ||
| }; | ||
| Box::into_raw(Box::new(Box::new(marker) as Box<Any + Send>)) as usize | ||
| } |
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