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rustc assumes that regular `extern "Rust"` functions unwind only if the `unwind` panic runtime is linked. `throw` was annotated as such, but unwound unconditionally. This could cause UB when a crate built with `-C panic=abort` called `throw` from `core` built with `-C panic=unwind`, since no terminator was added to handle the panic arising from calling an allegedly non-unwinding `extern "Rust"` function. rustc was taught to recognize this condition since https://github.com/rust-lang/rust/pull/144225 and prevented such linkage, but this caused regressions in https://github.com/rust-lang/rust/issues/148246, since this meant that Emscripten projects could not be built with `-C panic=abort` without recompiling std. The most straightforward solution would be to move `throw` into the `panic_unwind` crate, so that it's only compiled if the panic runtime is guaranteed to be `unwind`, but this is messy due to our architecture. Instead, move it into `unwind::wasm`, which is only compiled for bare-metal targets that default to `panic = "abort"`, rendering the issue moot.
core::arch - Rust's core library architecture-specific intrinsics
The core::arch module implements architecture-dependent intrinsics (e.g. SIMD).
Usage
core::arch is available as part of libcore and it is re-exported by
libstd. Prefer using it via core::arch or std::arch than via this crate.
Using core::arch via this crate requires nightly Rust, and it can (and does)
break often. The only cases in which you should consider using it via this crate
are:
-
if you need to re-compile
core::archyourself, e.g., with particular target-features enabled that are not enabled forlibcore/libstd. Note: if you need to re-compile it for a non-standard target, please prefer usingxargoand re-compilinglibcore/libstdas appropriate instead of using this crate. -
using some features that might not be available even behind unstable Rust features. We try to keep these to a minimum. If you need to use some of these features, please open an issue so that we can expose them in nightly Rust and you can use them from there.
Documentation
- Documentation - i686
- Documentation - x86_64
- Documentation - arm
- Documentation - aarch64
- Documentation - powerpc
- Documentation - powerpc64
- How to get started
- How to help implement intrinsics
License
core_arch is primarily distributed under the terms of both the MIT license and
the Apache License (Version 2.0), with portions covered by various BSD-like
licenses.
See LICENSE-APACHE, and LICENSE-MIT for details.
Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in core_arch by you, as defined in the Apache-2.0 license,
shall be dual licensed as above, without any additional terms or conditions.