sx/examples/concurrency/1820-concurrency-fiber-scheduler-deinit.sx

// Stream B1 (fibers) — `Scheduler.deinit` releases the scheduler's owned heap
// + fd resources, closing the documented bounded leaks (kq fd / heap Tasks /
// List backings). Verified by a tracking `GPA`: deinit drives the live
// allocation count DOWN, and resets the kqueue fd to -1.
//
// Scenario (one run that touches every freed resource):
//   - a SLEEPER fiber `sleep(5)`s              → exercises the `timers` List
//   - a READER fiber `block_on_fd`s a pipe     → exercises the kqueue fd + the
//                                                `io_waiters` List
//   - a WRITER fiber writes 3 bytes            → makes the pipe readable
//   - two `go` tasks compute 42 / 7            → exercise the heap `Task`s +
//                                                the `task_allocs` List
// After `run()` drains all of it, `deinit()` frees: the 2 heap Tasks, the
// `timers` / `io_waiters` / `task_allocs` List backings, and CLOSES the kqueue
// fd (resetting `kq` to -1). The Fibers were already reaped during `run()`.
//
// WHAT IT PROVES (the contract; numbers below are the snapshot):
//   - `freed by deinit: N` — live allocations reclaimed by `deinit` (> 0).
//   - `live after deinit` — the RESIDUAL. This is NOT zero and NOT a bug: it is
//     exactly the documented closure-env leak — one heap env per `spawn`/`go`
//     that sx cannot free (the runtime has no name for the env pointer). deinit
//     reclaims everything it CAN; the env residual is a language limitation.
//   - `kq open after run: 1` then `kq after deinit: -1` — the lazily-opened
//     kqueue fd was genuinely open after the fd round and is closed by deinit.
//   - `read: 3 [97 98 99]` — the fd path actually ran (reader blocked, woke via
//     kqueue, read 'a' 'b' 'c'), so the kq we close is a real, used fd.
//
// Counts are captured into locals BEFORE any `print` — `print` itself allocates
// format temporaries through the same GPA, which would otherwise pollute the
// reading.
//
// aarch64-macOS-pinned (`.build {"target":"macos"}`, matches host → runs
// end-to-end): sched.sx's switch asm + the kqueue path are per-arch/Apple.
#import "modules/std.sx";
sched :: #import "modules/std/sched.sx";

// Raw libc fd primitives — canonical signatures (the extern dedupe rejects a
// divergent re-binding of the same C symbol). `close` matches sched.sx's own.
pipe   :: (fds: *i32) -> i32 extern libc "pipe";
read   :: (fd: i32, buf: [*]u8, count: usize) -> isize extern libc "read";
write  :: (fd: i32, buf: [*]u8, count: usize) -> isize extern libc "write";
close  :: (fd: i32) -> i32 extern libc "close";

S :: struct {
    read_n: i64;
    bytes: [8]u8;
    read_done: bool;
}

main :: () -> i64 {
    st : S = .{ read_n = 0, read_done = false };   // bytes[] zero-filled; read() fills it

    fds : [2]i32 = ---;
    if pipe(@fds[0]) != 0 {
        print("1820: pipe() failed\n");
        return 1;
    }
    read_fd := fds[0];
    write_fd := fds[1];

    // Captured under the GPA scope; printed after it closes.
    after_run     : i64 = 0;
    after_deinit  : i64 = 0;
    kq_open_run   : bool = false;
    kq_after      : i32 = 0;

    gpa := mem.GPA.init();
    push Context.{ allocator = xx gpa, data = null } {
        s := sched.Scheduler.init();
        ps := @s; pst := @st;

        // SLEEPER — arms a virtual-time timer, then parks.
        ps.spawn(() => { ps.sleep(5); });

        // READER — blocks on the empty pipe until kqueue reports it readable.
        mk_reader :: (ps: *sched.Scheduler, pst: *S, rfd: i32) {
            ps.spawn(() => {
                ps.block_on_fd(rfd, true);
                n := read(rfd, xx @pst.bytes[0], xx 3);
                pst.read_n = xx n;
                pst.read_done = true;
            });
        }
        // WRITER — writes 'a' 'b' 'c', making the pipe readable.
        mk_writer :: (ps: *sched.Scheduler, wfd: i32) {
            ps.spawn(() => {
                buf : [3]u8 = ---;
                buf[0] = xx 97; buf[1] = xx 98; buf[2] = xx 99;
                write(wfd, xx @buf[0], xx 3);
            });
        }
        mk_reader(ps, pst, read_fd);
        mk_writer(ps, write_fd);

        // Two async tasks — heap Tasks tracked for deinit to free.
        ps.go(() -> i64 => 42);
        ps.go(() -> i64 => 7);

        ps.run();

        after_run   = gpa.alloc_count;
        kq_open_run = s.kq >= 0;
        ps.deinit();
        after_deinit = gpa.alloc_count;
        kq_after     = s.kq;
    }

    print("read: {} [", st.read_n);
    i := 0;
    while i < st.read_n {
        if i > 0 { print(" "); }
        print("{}", st.bytes[i]);
        i = i + 1;
    }
    print("]\n");
    print("freed by deinit: {}\n", after_run - after_deinit);
    print("live after deinit: {}\n", after_deinit);
    print("kq open after run: {}\n", kq_open_run);
    print("kq after deinit: {}\n", kq_after);

    close(read_fd);
    close(write_fd);
    return 0;
}