Re: Memory leakage problem

From:

Lionel B <me@privacy.net>

Newsgroups:

comp.lang.c++

Date:

Thu, 1 May 2008 12:32:59 +0000 (UTC)

Message-ID:

<fvcd9r$2j7$1@south.jnrs.ja.net>

On Thu, 01 May 2008 12:17:50 +0000, luke wrote:

Hi,
my program has a memory leak and I can't handle it. Basically, there are
two classes, class_a and class_b, and one object of each class: class_a
obj_a, and class_b obj_b.

One of the methods of class_a is basically

float* class_a::get_data(int n) {
    float *to_return = new float[n];
    .. //computing entries in to_return
    return to_return;
}

and one of the methods of class_b is basically

void class_b::use_data() {
    float* data;
    data = pointer_to_class_a -> get_data(s) ; .. //using data;
    delete [] data;
}

where s and pointer_to_class_a are members of class_b, and the latter
points to obj_a.
The method use_data() is used many times in the program, and it's the
only place where get_data(int) is used. However, the size of the program
(reported by top in linux)
increases drastically in time (use_data is used many times a second).

What do I do wrong?

Are you sure you're not calling class_a::get_data() elsewhere in the
program and not subsequently deleting its returned pointer?

Otherwise...

(to be honest, there are some other uses of new in
the program, but I don't suppose they are significant).

....maybe they are indeed significant.

Perhaps a debugger could cast some light on this.

In any case, have you considered using std::vector rather than new/delete
in your get_data/use_data functions? Maybe something along the lines of:

class_a
{
  std::vector<float> data;
};

std::vector<float>& class_a::get_data(int n) {
  data.resize(n);
    //compute entries in data
  return data;
}

void class_b::use_data() {
  std::vector<float>& data = pointer_to_class_a -> get_data(s);
    // use data
}

--
Lionel B