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Fail compilation on targets w/o soundness proof #404

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15 changes: 15 additions & 0 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -214,6 +214,21 @@ mod zerocopy {
pub(crate) use crate::*;
}

#[cfg(not(any(
target_arch = "i686",
target_arch = "x86",
target_arch = "x86_64",
target_arch = "arm",
target_arch = "aarch64",
)))]
compile_error!(
r#"Zerocopy has not been proven sound on this architecture.

This doesn't mean that it is unsound - just that we haven't gotten around to
proving it sound. If you need support for this architecture, let us know and
we'll prioritize it: https://github.com/google/zerocopy/issues/383"#
);
Comment on lines +224 to +230
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Re. this:

TODO: Figure out how to make sure we block the next minor version release on adding back all of the targets that people actually rely on.

We could potentially take the initial, weaker step of merely warning on unproven architectures:

Suggested change
compile_error!(
r#"Zerocopy has not been proven sound on this architecture.
This doesn't mean that it is unsound - just that we haven't gotten around to
proving it sound. If you need support for this architecture, let us know and
we'll prioritize it: https://github.com/google/zerocopy/issues/383"#
);
const _: () = {
#[deprecated = r#"Zerocopy has not been proven sound on this architecture.
This doesn't mean that it is unsound - just that we haven't gotten around to
proving it sound. If you need support for this architecture, let us know and
we'll prioritize it: https://github.com/google/zerocopy/issues/383"#]
const _WARNING: () = ();
#[warn(deprecated)]
_WARNING
};

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I think there's almost certainly merit in providing an escape hatch for weird architectures, too:

Suggested change
compile_error!(
r#"Zerocopy has not been proven sound on this architecture.
This doesn't mean that it is unsound - just that we haven't gotten around to
proving it sound. If you need support for this architecture, let us know and
we'll prioritize it: https://github.com/google/zerocopy/issues/383"#
);
#[cfg(not(ZEROCOPY_ALLOW_EXPERIMENTAL_ARCH))]
compile_error!(
r#"Zerocopy has not been proven sound on this architecture.
This doesn't mean that it is unsound - just that we haven't gotten around to
proving it sound. If you need support for this architecture, let us know and
we'll prioritize it: https://github.com/google/zerocopy/issues/383
You can temporarily enable this architecture by setting:
export RUSTFLAGS="--cfg ZEROCOPY_ALLOW_EXPERIMENTAL_ARCH"
"#
);
#[cfg(ZEROCOPY_ALLOW_EXPERIMENTAL_ARCH)]
const _: () = {
#[deprecated = r#"If you need support for this architecture, let us know and
we'll prioritize it: https://github.com/google/zerocopy/issues/383"#]
const _WARNING: () = ();
#[warn(deprecated)]
_WARNING
};


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When an architecture is expressly unsupported, we should report asmuch:

Suggested change
#[cfg(target_arch = "spirv")]
compile_error!(
r#"Zerocopy is not sound on this architecture. SPIRV's memory model
prohibits freely reinterpreting memory. If you believe this limitation is
incorrect, let us know: https://github.com/google/zerocopy/issues/383"#
);

#[rustversion::nightly]
#[cfg(all(test, not(__INTERNAL_USE_ONLY_NIGHLTY_FEATURES_IN_TESTS)))]
const _: () = {
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