rusty_alloc 0.4.0

//! M3 span-lifecycle gates. This file is its own process, and everything runs
//! in ONE test fn, so the global heap's counters are fully deterministic here
//! (unlike the parallel suites).

use rusty_alloc::alloc::{expand, free, malloc, realloc, stats, usable_size, zalloc};

#[test]
fn span_lifecycle_and_realloc() {
    // --- Large path basics -------------------------------------------------
    let s0 = stats();
    let p = malloc(1024 * 1024); // 1 MiB → 16-slice span
    assert!(!p.is_null());
    // SAFETY: live 1 MiB block.
    unsafe {
        assert!(usable_size(p) >= 1024 * 1024);
        p.write(7);
        p.add(1024 * 1024 - 1).write(8);
    }
    let s1 = stats();
    assert_eq!(s1.large_allocs - s0.large_allocs, 1, "large path not taken");

    // --- Span reclamation: free + realloc similar size must NOT grow the
    // segment count (the span is reused first-fit) ---------------------------
    // SAFETY: live block freed once.
    unsafe { free(p) };
    let s2 = stats();
    assert_eq!(
        s2.pages_retired - s1.pages_retired,
        1,
        "large span not retired"
    );
    let q = malloc(900 * 1024);
    assert!(!q.is_null());
    let s3 = stats();
    assert_eq!(
        s3.segments, s2.segments,
        "reclaimed span not reused — new segment allocated"
    );
    // SAFETY: live block.
    unsafe { free(q) };

    // --- zalloc over a RECYCLED span must be re-zeroed ----------------------
    let d = malloc(2 * 1024 * 1024);
    // SAFETY: live block, dirtied then freed.
    unsafe {
        core::ptr::write_bytes(d, 0xAB, 2 * 1024 * 1024);
        free(d);
    }
    let z = zalloc(2 * 1024 * 1024);
    assert!(!z.is_null());
    // SAFETY: live zeroed block.
    unsafe {
        for i in (0..2 * 1024 * 1024).step_by(4096) {
            assert_eq!(
                z.add(i).read(),
                0,
                "recycled span leaked dirty bytes at +{i}"
            );
        }
        free(z);
    }

    // --- Binned page retire: burst-free a size class, pages return ---------
    let s4 = stats();
    let blocks: Vec<*mut u8> = (0..2000).map(|_| malloc(2048)).collect();
    let s5 = stats();
    assert!(
        s5.pages_fresh - s4.pages_fresh >= 2,
        "burst should carve several pages"
    );
    for &b in &blocks {
        // SAFETY: tracked live blocks.
        unsafe { free(b) };
    }
    let s6 = stats();
    assert!(
        s6.pages_retired - s5.pages_retired >= (s5.pages_fresh - s4.pages_fresh) - 1,
        "empty pages not retired (one may stay warm): fresh {} retired {}",
        s5.pages_fresh - s4.pages_fresh,
        s6.pages_retired - s5.pages_retired
    );

    // --- Coalescing observable: after retiring everything, a full-segment
    // large alloc must fit in the SAME segment count -------------------------
    let big = malloc(12 * 1024 * 1024);
    assert!(!big.is_null());
    let s7 = stats();
    assert_eq!(
        s7.segments, s6.segments,
        "coalescing failed — 12 MiB span needed a new segment"
    );
    // SAFETY: live block.
    unsafe { free(big) };

    // --- realloc semantics --------------------------------------------------
    let r = malloc(100);
    // SAFETY: live blocks; realloc contract followed throughout.
    unsafe {
        core::ptr::write_bytes(r, 0x5A, 100);
        // Grow within the same bin (112B usable): in place. Asserted by
        // POINTER IDENTITY (the behaviour callers depend on) AND the counter.
        let s_ip0 = stats().realloc_in_place;
        let r2 = realloc(r, 112);
        assert_eq!(r2, r, "grow-within-usable must stay in place");
        assert_eq!(stats().realloc_in_place - s_ip0, 1);
        // Grow across bins: moves, prefix preserved.
        let r3 = realloc(r2, 4096);
        assert!(!r3.is_null());
        for i in 0..100 {
            assert_eq!(r3.add(i).read(), 0x5A, "realloc lost prefix at {i}");
        }
        // Shrink far below half: moves to a smaller class.
        let r4 = realloc(r3, 16);
        assert!(!r4.is_null());
        assert_eq!(r4.read(), 0x5A);
        assert!(usable_size(r4) < 4096);
        // expand: in-place only.
        assert_eq!(expand(r4, 8), r4);
        assert!(expand(r4, 1 << 20).is_null(), "expand must never move");
        free(r4);
    }

    // --- segment map -------------------------------------------------------
    let m = malloc(64);
    assert!(rusty_alloc::alloc::is_in_heap_region(m));
    let stack_local = 0u8;
    assert!(!rusty_alloc::alloc::is_in_heap_region(&stack_local));
    // SAFETY: live block.
    unsafe { free(m) };

    // --- strict leak accounting for this whole test ------------------------
    let end = stats();
    assert_eq!(
        end.allocs - s0.allocs,
        end.frees - s0.frees,
        "leak inside span lifecycle test"
    );
}

// NOTE: exactly one #[test] lives in this file on purpose — the counter
// asserts above need a process where no other test races the global heap.
// The realloc storm lives in alloc_core.rs with the other parallel-safe tests.