@cmpxchgStrong
- @cmpxchgStrong

@cmpxchgStrong

@cmpxchgStrong(comptime T: type, ptr: *T, expected_value: T, new_value: T, success_order: AtomicOrder, fail_order: AtomicOrder) ?T

This function performs a strong atomic compare-and-exchange operation, returning null if the current value is not the given expected value. It’s the equivalent of this code, except atomic:

not_atomic_cmpxchgStrong.zig

fn cmpxchgStrongButNotAtomic(comptime T: type, ptr: *T, expected_value: T, new_value: T) ?T {
    const old_value = ptr.*;
    if (old_value == expected_value) {
        ptr.* = new_value;
        return null;
    } else {
        return old_value;
    }
}

If you are using cmpxchg in a retry loop, @cmpxchgWeak is the better choice, because it can be implemented more efficiently in machine instructions.

T must be a pointer, a bool, a float, an integer or an enum.

@typeInfo(@TypeOf(ptr)).Pointer.alignment must be >= @sizeOf(T).

AtomicOrder can be found with @import("std").builtin.AtomicOrder.