atomic-maybe-uninit

Atomic operations on potentially uninitialized integers.

Motivation

Copying types containing uninitialized bytes (e.g., padding), via the standard library's atomic types is undefined behavior because the copy goes through integers.

This crate provides a way to soundly perform such operations.

Platform Support

Currently, x86, x86_64, ARM (v6+), AArch64, RISC-V, LoongArch64, MIPS32, MIPS64, PowerPC, s390x, and MSP430 are supported.

| targetarch | primitives | load/store | swap | CAS | | ------------------------------------ | --------------------------------------------------- |:----------:|:-----:|:-----:| | x86 | isize,usize,i8,u8,i16,u16,i32,u32,i64,u64 | ✓ | ✓ | ✓ | | x8664 | isize,usize,i8,u8,i16,u16,i32,u32,i64,u64 | ✓ | ✓ | ✓ | | x86_64 (+cmpxchg16b) | i128,u128 | ✓ | ✓ | ✓ | | arm (v6+) | isize,usize,i8,u8,i16,u16,i32,u32 | ✓ | ✓[1] | ✓[1] | | arm (v6+ except for M-profile) [2] | i64,u64 | ✓ | ✓ | ✓ | | aarch64 | isize,usize,i8,u8,i16,u16,i32,u32,i64,u64,i128,u128 | ✓ | ✓ | ✓ | | riscv32 | isize,usize,i8,u8,i16,u16,i32,u32 | ✓ | ✓[1] | ✓[1] | | riscv64 | isize,usize,i8,u8,i16,u16,i32,u32,i64,u64 | ✓ | ✓[1] | ✓[1] | | loongarch64 [3] | isize,usize,i8,u8,i16,u16,i32,u32,i64,u64 | ✓ | ✓ | ✓ | | mips / mips32r6 [4] | isize,usize,i8,u8,i16,u16,i32,u32 | ✓ | ✓ | ✓ | | mips64 / mips64r6 [4] | isize,usize,i8,u8,i16,u16,i32,u32,i64,u64 | ✓ | ✓ | ✓ | | powerpc [4] | isize,usize,i8,u8,i16,u16,i32,u32 | ✓ | ✓ | ✓ | | powerpc64 [4] | isize,usize,i8,u8,i16,u16,i32,u32,i64,u64 | ✓ | ✓ | ✓ | | powerpc64 (pwr8+) [4] [5] | i128,u128 | ✓ | ✓ | ✓ | | s390x [4] | isize,usize,i8,u8,i16,u16,i32,u32,i64,u64,i128,u128 | ✓ | ✓ | ✓ | | msp430 [4] | isize,usize,i8,u8,i16,u16 | ✓ | | |

[1] ARM's atomic RMW operations are not available on v6-m (thumbv6m). RISC-V's atomic RMW operations are not available on targets without the A (or G which means IMAFD) extension such as riscv32i, riscv32imc, etc.
[2] ARMv6+ except for M-profile architecture such as thumbv6m, thumbv7m, etc.
[3] Requires Rust 1.72+.
[4] Requires nightly due to #![feature(asm_experimental_arch)].
[5] target-cpu pwr8, pwr9, or pwr10. powerpc64le is pwr8 by default.

Feel free to submit an issue if your target is not supported yet.

Related Projects

• [portable-atomic]: Portable atomic types including support for 128-bit atomics, atomic float, etc.
• [atomic-memcpy]: Byte-wise atomic memcpy.

License

Licensed under either of Apache License, Version 2.0 or MIT license at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.