katelyn a. martin df45c579de rustc_target: add "unwind" payloads to Abi ... ### Overview This commit begins the implementation work for RFC 2945. For more information, see the rendered RFC [1] and tracking issue [2]. A boolean `unwind` payload is added to the `C`, `System`, `Stdcall`, and `Thiscall` variants, marking whether unwinding across FFI boundaries is acceptable. The cases where each of these variants' `unwind` member is true correspond with the `C-unwind`, `system-unwind`, `stdcall-unwind`, and `thiscall-unwind` ABI strings introduced in RFC 2945 [3]. ### Feature Gate and Unstable Book This commit adds a `c_unwind` feature gate for the new ABI strings. Tests for this feature gate are included in `src/test/ui/c-unwind/`, which ensure that this feature gate works correctly for each of the new ABIs. A new language features entry in the unstable book is added as well. ### Further Work To Be Done This commit does not proceed to implement the new unwinding ABIs, and is intentionally scoped specifically to *defining* the ABIs and their feature flag. ### One Note on Test Churn This will lead to some test churn, in re-blessing hash tests, as the deleted comment in `src/librustc_target/spec/abi.rs` mentioned, because we can no longer guarantee the ordering of the `Abi` variants. While this is a downside, this decision was made bearing in mind that RFC 2945 states the following, in the "Other `unwind` Strings" section [3]: > More unwind variants of existing ABI strings may be introduced, > with the same semantics, without an additional RFC. Adding a new variant for each of these cases, rather than specifying a payload for a given ABI, would quickly become untenable, and make working with the `Abi` enum prone to mistakes. This approach encodes the unwinding information *into* a given ABI, to account for the future possibility of other `-unwind` ABI strings. ### Ignore Directives `ignore-*` directives are used in two of our `*-unwind` ABI test cases. Specifically, the `stdcall-unwind` and `thiscall-unwind` test cases ignore architectures that do not support `stdcall` and `thiscall`, respectively. These directives are cribbed from `src/test/ui/c-variadic/variadic-ffi-1.rs` for `stdcall`, and `src/test/ui/extern/extern-thiscall.rs` for `thiscall`. This would otherwise fail on some targets, see: fcf697f902 ### Footnotes [1]: https://github.com/rust-lang/rfcs/blob/master/text/2945-c-unwind-abi.md [2]: https://github.com/rust-lang/rust/issues/74990 [3]: https://github.com/rust-lang/rfcs/blob/master/text/2945-c-unwind-abi.md#other-unwind-abi-strings		2021-03-09 14:38:29 -05:00
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src	rustc_target: add "unwind" payloads to Abi	2021-03-09 14:38:29 -05:00
Cargo.toml	Update to rustc-demangle 0.1.18	2020-10-21 21:11:11 +01:00