Archetype::grow leaks previously allocated memory

[ghost]

With this test case on master:

#[test]
fn spawn_batch_unexact() {
    struct Unhint<I>(I);
    impl<I: Iterator> Iterator for Unhint<I> {
        type Item = I::Item;

        fn next(&mut self) -> Option<Self::Item> {
            self.0.next()
        }

        fn size_hint(&self) -> (usize, Option<usize>) {
            (0, None)
        }
    }

    let mut world = World::new();
    world.spawn_batch(Unhint((0..100).map(|x| (x, "abc"))));
    let entities = world
        .query::<&i32>()
        .iter()
        .map(|(_, &x)| x)
        .collect::<Vec<_>>();
    assert_eq!(entities.len(), 100);
}

miri reports:

alloc4621966 (Rust heap, size: 1280, align: 8) {
    0x000 │ ╾a4468557[<11121328>]─╼ 03 00 00 00 00 00 00 00 │ ╾──────╼........
    // ... repeats ...
    0x400 │ 00 00 00 00 01 00 00 00 02 00 00 00 03 00 00 00 │ ................
    0x410 │ 04 00 00 00 05 00 00 00 06 00 00 00 07 00 00 00 │ ................
    // ... repeats ...
    0x4f0 │ 3c 00 00 00 3d 00 00 00 3e 00 00 00 3f 00 00 00 │ <...=...>...?...
}
alloc4468557 (global, size: 3, align: 1) {
    61 62 63                                        │ abc
}
alloc4622641 (global, size: 3, align: 1) {
    61 62 63                                        │ abc
}
// ... repeats ...

cargo-valgrind reports:

       Error Leaked 1.2 kiB
        Info at malloc (vg_replace_malloc.c:307)
             at alloc::alloc::alloc (alloc.rs:80)
             at hecs::archetype::Archetype::grow (archetype.rs:195)
             at hecs::archetype::Archetype::allocate (archetype.rs:159)
             at <hecs::world::SpawnBatchIter<I> as core::iter::traits::iterator::Iterator>::next (world.rs:763)
             at <&mut I as core::iter::traits::iterator::Iterator>::next (iterator.rs:3283)
             at <hecs::world::SpawnBatchIter<I> as core::ops::drop::Drop>::drop (world.rs:748)
             at core::ptr::drop_in_place (mod.rs:184)
             at tests::spawn_batch_unexact (tests.rs:355)
             at tests::spawn_batch_unexact::{{closure}} (tests.rs:340)
             at core::ops::function::FnOnce::call_once (function.rs:232)
             at call_once<(),FnOnce<()>> (boxed.rs:1076)
             at call_once<(),alloc::boxed::Box<FnOnce<()>>> (panic.rs:318)
             at do_call<std::panic::AssertUnwindSafe<alloc::boxed::Box<FnOnce<()>>>,()> (panicking.rs:297)
             at try<(),std::panic::AssertUnwindSafe<alloc::boxed::Box<FnOnce<()>>>> (panicking.rs:274)
             at catch_unwind<std::panic::AssertUnwindSafe<alloc::boxed::Box<FnOnce<()>>>,()> (panic.rs:394)
             at run_test_in_process (lib.rs:541)
             at test::run_test::run_test_inner::{{closure}} (lib.rs:450)
       Error Leaked 2.0 MiB
        Info at malloc (vg_replace_malloc.c:307)
             at alloc::alloc::alloc (alloc.rs:80)
             at hecs::archetype::Archetype::grow (archetype.rs:195)
             at hecs::archetype::Archetype::allocate (archetype.rs:159)
             at hecs::world::World::spawn (world.rs:98)
             at tests::spawn_many (tests.rs:248)
             at tests::spawn_many::{{closure}} (tests.rs:244)
             at core::ops::function::FnOnce::call_once (function.rs:232)
             at call_once<(),FnOnce<()>> (boxed.rs:1076)
             at call_once<(),alloc::boxed::Box<FnOnce<()>>> (panic.rs:318)
             at do_call<std::panic::AssertUnwindSafe<alloc::boxed::Box<FnOnce<()>>>,()> (panicking.rs:297)
             at try<(),std::panic::AssertUnwindSafe<alloc::boxed::Box<FnOnce<()>>>> (panicking.rs:274)
             at catch_unwind<std::panic::AssertUnwindSafe<alloc::boxed::Box<FnOnce<()>>>,()> (panic.rs:394)
             at run_test_in_process (lib.rs:541)
             at test::run_test::run_test_inner::{{closure}} (lib.rs:450)
             at std::sys_common::backtrace::__rust_begin_short_backtrace (backtrace.rs:130)
             at {{closure}}<closure-0,()> (mod.rs:475)
             at call_once<(),closure-0> (panic.rs:318)
             at do_call<std::panic::AssertUnwindSafe<closure-0>,()> (panicking.rs:297)
             at try<(),std::panic::AssertUnwindSafe<closure-0>> (panicking.rs:274)
             at catch_unwind<std::panic::AssertUnwindSafe<closure-0>,()> (panic.rs:394)
             at {{closure}}<closure-0,()> (mod.rs:474)
             at core::ops::function::FnOnce::call_once{{vtable-shim}} (function.rs:232)
             at call_once<(),FnOnce<()>> (boxed.rs:1076)
             at call_once<(),alloc::boxed::Box<FnOnce<()>>> (boxed.rs:1076)
             at std::sys::unix::thread::Thread::new::thread_start (thread.rs:87)
     Summary Leaked 2.0 MiB total

Note that valgrind also reported leaked memory for spawn_many, which is ignored for miri, but it seems likely that both leaks may have the same underlying reason.

[ghost]

Well, seems like this has a simple cause: the old allocation isn't freed in Archetype::grow! self.data = UnsafeCell::new(new_data); merely dropped the pointer, the allocation isn't freed.

[Ralith]

Whoops, thanks for catching that! Will push a fix tonight.

[Ralith]

Fix released in 0.2.15.