fixed_width_ints.rs

//! This module contains type aliases for C's fixed-width integer types .
//!
//! These aliases are deprecated: use the Rust types instead.

#[deprecated(since = "0.2.55", note = "Use i8 instead.")]
pub type int8_t = i8;
#[deprecated(since = "0.2.55", note = "Use i16 instead.")]
pub type int16_t = i16;
#[deprecated(since = "0.2.55", note = "Use i32 instead.")]
pub type int32_t = i32;
#[deprecated(since = "0.2.55", note = "Use i64 instead.")]
pub type int64_t = i64;
#[deprecated(since = "0.2.55", note = "Use u8 instead.")]
pub type uint8_t = u8;
#[deprecated(since = "0.2.55", note = "Use u16 instead.")]
pub type uint16_t = u16;
#[deprecated(since = "0.2.55", note = "Use u32 instead.")]
pub type uint32_t = u32;
#[deprecated(since = "0.2.55", note = "Use u64 instead.")]
pub type uint64_t = u64;

cfg_if! {
    if #[cfg(all(target_arch = "aarch64", not(target_os = "windows")))] {
        // This introduces partial support for FFI with __int128 and
        // equivalent types on platforms where Rust's definition is validated
        // to match the standard C ABI of that platform.
        //
        // Rust does not guarantee u128/i128 are sound for FFI, and its
        // definitions are in fact known to be incompatible. [0]
        //
        // However these problems aren't fundamental, and are just platform
        // inconsistencies. Specifically at the time of this writing:
        //
        // * For x64 SysV ABIs (everything but Windows), the types are underaligned.
        // * For all Windows ABIs, Microsoft doesn't actually officially define __int128,
        //   and as a result different implementations don't actually agree on its ABI.
        //
        // But on the other major aarch64 platforms (android, linux, ios, macos) we have
        // validated that rustc has the right ABI for these types. This is important because
        // aarch64 uses these types in some fundamental OS types like user_fpsimd_struct,
        // which represents saved simd registers.
        //
        // Any API which uses these types will need to `#[ignore(improper_ctypes)]`
        // until the upstream rust issue is resolved, but this at least lets us make
        // progress on platforms where this type is important.
        //
        // The list of supported architectures and OSes is intentionally very restricted,
        // as careful work needs to be done to verify that a particular platform
        // has a conformant ABI.
        //
        // [0]: https://github.com/rust-lang/rust/issues/54341

        /// C `__int128` (a GCC extension that's part of many ABIs)
        pub type __int128 = i128;
        /// C `unsigned __int128` (a GCC extension that's part of many ABIs)
        pub type __uint128 = u128;
        /// C __int128_t (alternate name for [__int128][])
        pub type __int128_t = i128;
        /// C __uint128_t (alternate name for [__uint128][])
        pub type __uint128_t = u128;

        macro_rules! static_assert_eq {
            ($a:expr, $b:expr) => {
                const _: [(); $a] = [(); $b];
            };
        }

        // NOTE: if you add more platforms to here, you may need to cfg
        // these consts. They should always match the platform's values
        // for `sizeof(__int128)` and `_Alignof(__int128)`.
        const _SIZE_128: usize = 16;
        const _ALIGN_128: usize = 16;

        // Since Rust doesn't officially guarantee that these types
        // have compatible ABIs, we const assert that these values have the
        // known size/align of the target platform's libc. If rustc ever
        // tries to regress things, it will cause a compilation error.
        //
        // This isn't a bullet-proof solution because e.g. it doesn't
        // catch the fact that llvm and gcc disagree on how x64 __int128
        // is actually *passed* on the stack (clang underaligns it for
        // the same reason that rustc *never* properly aligns it).
        static_assert_eq!(core::mem::size_of::<__int128>(), _SIZE_128);
        static_assert_eq!(core::mem::align_of::<__int128>(), _ALIGN_128);

        static_assert_eq!(core::mem::size_of::<__uint128>(), _SIZE_128);
        static_assert_eq!(core::mem::align_of::<__uint128>(), _ALIGN_128);

        static_assert_eq!(core::mem::size_of::<__int128_t>(), _SIZE_128);
        static_assert_eq!(core::mem::align_of::<__int128_t>(), _ALIGN_128);

        static_assert_eq!(core::mem::size_of::<__uint128_t>(), _SIZE_128);
        static_assert_eq!(core::mem::align_of::<__uint128_t>(), _ALIGN_128);
    }
}