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| author | Mazdak Farrokhzad <twingoow@gmail.com> | 2019-05-22 18:08:13 +0200 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2019-05-22 18:08:13 +0200 |
| commit | 7cd8d3d8d00bcadb32a4243f33b91c7b89af7a69 (patch) | |
| tree | b167a1dabb4ded350807e1245a9b99dfd5019938 /src/libsyntax | |
| parent | 37ff5d388f8c004ca248adb635f1cc84d347eda0 (diff) | |
| parent | a31dc8e3b153ac3073f9fb14d8e523a350fe10f2 (diff) | |
| download | rust-7cd8d3d8d00bcadb32a4243f33b91c7b89af7a69.tar.gz rust-7cd8d3d8d00bcadb32a4243f33b91c7b89af7a69.zip | |
Rollup merge of #60300 - mjbshaw:ffi_types, r=rkruppe
Allow null-pointer-optimized enums in FFI if their underlying representation is FFI safe I'm not sure if this requires an RFC. I attempted to start [a discussion on internals.rust-lang.org](https://internals.rust-lang.org/t/options-ffi-safety-and-guarantees-for-abi-compatibility-with-nonnull-optimizations/9784) and when no one really objected I figured I'd go ahead and try implementing this. This allows types like `Option<NonZeroU8>` to be used in FFI without triggering the `improper_ctypes` lint. This works by changing the `is_repr_nullable_ptr` function to consider an enum `E` to be FFI-safe if: - `E` has no explicit `#[repr(...)]`. - It only has two variants. - One of those variants is empty (meaning it has no fields). - The other variant has only one field. - That field is one of the following: - `&T` - `&mut T` - `extern "C" fn` - `core::num::NonZero*` - `core::ptr::NonNull<T>` - `#[repr(transparent)] struct` wrapper around one of the types in this list. - The size of `E` and its field are both known and are both the same size (implying `E` is participating in the nonnull optimization). This logic seems consistent with [the Rust nomicon](https://doc.rust-lang.org/nomicon/repr-rust.html).
Diffstat (limited to 'src/libsyntax')
| -rw-r--r-- | src/libsyntax/feature_gate.rs | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs index 5b1a9bb739f..b27f5b1495c 100644 --- a/src/libsyntax/feature_gate.rs +++ b/src/libsyntax/feature_gate.rs @@ -1134,6 +1134,13 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[ is just used to enable niche optimizations in libcore \ and will never be stable", cfg_fn!(rustc_attrs))), + (sym::rustc_nonnull_optimization_guaranteed, Whitelisted, template!(Word), + Gated(Stability::Unstable, + sym::rustc_attrs, + "the `#[rustc_nonnull_optimization_guaranteed]` attribute \ + is just used to enable niche optimizations in libcore \ + and will never be stable", + cfg_fn!(rustc_attrs))), (sym::rustc_regions, Normal, template!(Word), Gated(Stability::Unstable, sym::rustc_attrs, "the `#[rustc_regions]` attribute \ |