Why I fail so bad to check for memory leak with this code?

[Marco Sulla]

On Fri, 22 Jul 2022 at 09:00, Barry <barry at barrys-emacs.org> wrote:
> With code as complex as python’s there will be memory allocations that
occur that will not be directly related to the python code you test.
>
> To put it another way there is noise in your memory allocation signal.
>
> Usually the signal of a memory leak is very clear, as you noticed.
>
> For rare leaks I would use a tool like valgrind.

Thank you all, but I needed a simple decorator to automatize the memory
leak (and segfault) tests. I think that this version is good enough, I hope
that can be useful to someone:

def trace(iterations=100):
    def decorator(func):
        def wrapper():
            print(
                f"Loops: {iterations} - Evaluating: {func.__name__}",
                flush=True
            )

            tracemalloc.start()

            snapshot1 = tracemalloc.take_snapshot().filter_traces(
                (tracemalloc.Filter(True, __file__), )
            )

            for i in range(iterations):
                func()

            gc.collect()

            snapshot2 = tracemalloc.take_snapshot().filter_traces(
                (tracemalloc.Filter(True, __file__), )
            )

            top_stats = snapshot2.compare_to(snapshot1, 'lineno')
            tracemalloc.stop()

            for stat in top_stats:
                if stat.count_diff * 100 > iterations:
                    raise ValueError(f"stat: {stat}")

        return wrapper

    return decorator


If the decorated function fails, you can try to raise the iterations
parameter. I found that in my cases sometimes I needed a value of 200 or 300