// Atomic($T).swap — atomic exchange (LLVM atomicrmw xchg): store the new value,
// return the OLD one. Stream A (atomics) A.3. Single-thread.
// Covers swap at BOTH comptime (#run) and runtime — they must agree.
#import "modules/std.sx";
#import "modules/std/atomic.sx";

c_swap :: () -> i64 { a := Atomic(i64).init(7); old := a.swap(42, .seq_cst); return old * 100 + a.load(.seq_cst); }
G_SWAP :: #run c_swap();   // 742 (old 7, now 42)

main :: () {
    a := Atomic(i64).init(7);
    old := a.swap(42, .acq_rel);
    print("swap old: {}\n", old);              // 7
    print("swap now: {}\n", a.load(.acquire)); // 42
    print("comptime swap: {}\n", G_SWAP);      // 742 (matches runtime)
}