Function std::intrinsics::atomic_xsub_relaxed

pub unsafe extern "rust-intrinsic" fn atomic_xsub_relaxed<T>(
    dst: *mut T, 
    src: T
) -> T where
    T: Copy, 

🔬 This is a nightly-only experimental API. (core_intrinsics)

intrinsics are unlikely to ever be stabilized, instead they should be used through stabilized interfaces in the rest of the standard library

从当前值减去，返回前一个值。

通过将 Ordering::Relaxed 作为 order 传递，可以通过 fetch_sub 方法在 atomic 类型上使用此内联函数的稳定版本。 例如， AtomicIsize::fetch_sub.