rust/tests/codegen/unwind-extern-exports.rs

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// compile-flags: -C opt-level=0
// ignore-wasm32-bare compiled with panic=abort by default
// needs-unwind
#![crate_type = "lib"]
rustc: Fill out remaining parts of C-unwind ABI This commit intends to fill out some of the remaining pieces of the C-unwind ABI. This has a number of other changes with it though to move this design space forward a bit. Notably contained within here is: * On `panic=unwind`, the `extern "C"` ABI is now considered as "may unwind". This fixes a longstanding soundness issue where if you `panic!()` in an `extern "C"` function defined in Rust that's actually UB because the LLVM representation for the function has the `nounwind` attribute, but then you unwind. * Whether or not a function unwinds now mainly considers the ABI of the function instead of first checking the panic strategy. This fixes a miscompile of `extern "C-unwind"` with `panic=abort` because that ABI can still unwind. * The aborting stub for non-unwinding ABIs with `panic=unwind` has been reimplemented. Previously this was done as a small tweak during MIR generation, but this has been moved to a separate and dedicated MIR pass. This new pass will, for appropriate functions and function calls, insert a `cleanup` landing pad for any function call that may unwind within a function that is itself not allowed to unwind. Note that this subtly changes some behavior from before where previously on an unwind which was caught-to-abort it would run active destructors in the function, and now it simply immediately aborts the process. * The `#[unwind]` attribute has been removed and all users in tests and such are now using `C-unwind` and `#![feature(c_unwind)]`. I think this is largely the last piece of the RFC to implement. Unfortunately I believe this is still not stabilizable as-is because activating the feature gate changes the behavior of the existing `extern "C"` ABI in a way that has no replacement. My thinking for how to enable this is that we add support for the `C-unwind` ABI on stable Rust first, and then after it hits stable we change the behavior of the `C` ABI. That way anyone straddling stable/beta/nightly can switch to `C-unwind` safely.
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#![feature(c_unwind)]
// Make sure these all do *not* get the attribute.
// We disable optimizations to prevent LLVM from inferring the attribute.
// CHECK-NOT: nounwind
// "C" ABI
rustc: Fill out remaining parts of C-unwind ABI This commit intends to fill out some of the remaining pieces of the C-unwind ABI. This has a number of other changes with it though to move this design space forward a bit. Notably contained within here is: * On `panic=unwind`, the `extern "C"` ABI is now considered as "may unwind". This fixes a longstanding soundness issue where if you `panic!()` in an `extern "C"` function defined in Rust that's actually UB because the LLVM representation for the function has the `nounwind` attribute, but then you unwind. * Whether or not a function unwinds now mainly considers the ABI of the function instead of first checking the panic strategy. This fixes a miscompile of `extern "C-unwind"` with `panic=abort` because that ABI can still unwind. * The aborting stub for non-unwinding ABIs with `panic=unwind` has been reimplemented. Previously this was done as a small tweak during MIR generation, but this has been moved to a separate and dedicated MIR pass. This new pass will, for appropriate functions and function calls, insert a `cleanup` landing pad for any function call that may unwind within a function that is itself not allowed to unwind. Note that this subtly changes some behavior from before where previously on an unwind which was caught-to-abort it would run active destructors in the function, and now it simply immediately aborts the process. * The `#[unwind]` attribute has been removed and all users in tests and such are now using `C-unwind` and `#![feature(c_unwind)]`. I think this is largely the last piece of the RFC to implement. Unfortunately I believe this is still not stabilizable as-is because activating the feature gate changes the behavior of the existing `extern "C"` ABI in a way that has no replacement. My thinking for how to enable this is that we add support for the `C-unwind` ABI on stable Rust first, and then after it hits stable we change the behavior of the `C` ABI. That way anyone straddling stable/beta/nightly can switch to `C-unwind` safely.
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pub extern "C-unwind" fn foo_unwind() {}
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// "Rust"
// (`extern "Rust"` could be removed as all `fn` get it implicitly; we leave it in for clarity.)
rustc: Fill out remaining parts of C-unwind ABI This commit intends to fill out some of the remaining pieces of the C-unwind ABI. This has a number of other changes with it though to move this design space forward a bit. Notably contained within here is: * On `panic=unwind`, the `extern "C"` ABI is now considered as "may unwind". This fixes a longstanding soundness issue where if you `panic!()` in an `extern "C"` function defined in Rust that's actually UB because the LLVM representation for the function has the `nounwind` attribute, but then you unwind. * Whether or not a function unwinds now mainly considers the ABI of the function instead of first checking the panic strategy. This fixes a miscompile of `extern "C-unwind"` with `panic=abort` because that ABI can still unwind. * The aborting stub for non-unwinding ABIs with `panic=unwind` has been reimplemented. Previously this was done as a small tweak during MIR generation, but this has been moved to a separate and dedicated MIR pass. This new pass will, for appropriate functions and function calls, insert a `cleanup` landing pad for any function call that may unwind within a function that is itself not allowed to unwind. Note that this subtly changes some behavior from before where previously on an unwind which was caught-to-abort it would run active destructors in the function, and now it simply immediately aborts the process. * The `#[unwind]` attribute has been removed and all users in tests and such are now using `C-unwind` and `#![feature(c_unwind)]`. I think this is largely the last piece of the RFC to implement. Unfortunately I believe this is still not stabilizable as-is because activating the feature gate changes the behavior of the existing `extern "C"` ABI in a way that has no replacement. My thinking for how to enable this is that we add support for the `C-unwind` ABI on stable Rust first, and then after it hits stable we change the behavior of the `C` ABI. That way anyone straddling stable/beta/nightly can switch to `C-unwind` safely.
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pub fn bar() {}