Simple memory leak detector for -O0 code or unit test mode

[alexveden]

It would be great to have very simple memory leak check in allocators when doing debug builds. It simply tracks a number of allocs and number of frees via simple global variable counter.

In a warning message, c3c may advise compiling and run with --sanitize=address to find out exact place of memory leak.

I have similar in C:

const Allocator_i*
AllocatorGeneric_create(void)
{
#ifndef NDEBUG
    memset(&allocator__generic_data.stats, 0, sizeof(allocator__generic_data.stats));
#endif
    return &allocator__generic_data.base;
}

const Allocator_i*
AllocatorGeneric_destroy(void)
{
    allocator__generic_data.magic = 0;

#ifndef NDEBUG
    allocator_generic_s* a = &allocator__generic_data;
    // NOTE: this message only shown if no DNDEBUG
    if (a->stats.n_allocs != a->stats.n_free) {
        log$debug(
            "Allocator: Possible memory leaks/double free: memory allocator->allocs() [%u] != allocator->free() [%u] count! \n",
            a->stats.n_allocs,
            a->stats.n_free
        );
    }
    memset(&allocator__generic_data.stats, 0, sizeof(allocator__generic_data.stats));
#endif

    return NULL;
}

static void*
allocator_generic__malloc(usize size)
{
#ifndef NDEBUG
    allocator__generic_data.stats.n_allocs++;
#endif
    return malloc(size);
}

static void
allocator_generic__free(void* ptr)
{
#ifndef NDEBUG
    if (ptr != NULL) {
        allocator__generic_data.stats.n_free++;
    }
#endif
    free(ptr);
}

[lerno]

What do you think about @assert_leaks?

[lerno]

And of course the tracking heap allocator.

[alexveden]

And of course the tracking heap allocator.

That's cool. Also --sanitize=address track leaks with full stack print.

But these tools require special flags or developer efforts to enable them. I'm proposing to have lightweight and unintrusive rough checks for debug builds (or maybe on tests) enabled by default. Emitting just one warning message about possible leaks.

[lerno]

Tracking allocations (necessary for leak detection) is a bit overkill for debug builds, however it could certainly be implemented (easily!) for tests by simply using the Tracking Allocator for running tests.

[alexveden]

Do you mean maybe replacing it here, in test runner?

[lerno]

The @pool stays, but the tracking allocator wraps the @pool