Question

The error obtained:

$ rustc leakyFunction.rs --test
$ ./leakyFunction 

running 1 test
test testForLeakage ... Unreclaimed object found at 0xb6d02d98: ((), (10))
leaked memory in rust main loop (1 objects)
leakyFunction: /home/havvy/rust/src/rt/memory_region.cpp:172:
    memory_region::~memory_region(): Assertion `false' failed.
Aborted (core dumped)

The rust code (reduced testcase):

use std;

type boxedFn = { theFn: fn () -> uint };

fn createClosure (closedUint: uint) -> boxedFn {
    { theFn: fn@ () -> uint { closedUint } }
}

#[test]
fn testForLeakage () {
    let aFn: boxedFn = createClosure(10);

    let myInt: uint = aFn.theFn();

    assert myInt == 10;
}

Why is this leaking memory?

Answer 1

Anytime you see a memory leak, it’s a bug in Rust (unless you are mucking about with native code…and in that case, our leak detectors probably wouldn’t find it). In this case, it’s issue #1896.