Memory leak with dynamic array

[bearophile]

Joseph Wakeling:

> Can anyone advise? :-)

Dynamic arrays in D are not black boxes, they are an abstraction that leaks a lot, so you must know how dynamic arrays are implemented. Recently the implementation of dynamic arrays being changed, has someone a link to a description of how they work now?

Few notes on your code: there is no need to import std.array into that little program. Often there is no need to add an "uint" inside the foreach. I suggest to put a space after every comma. I also suggest you to write big numbers like this: 5_000_000 because they can avoid some mistakes.

>From the little I know about the new arrays this doesn't work anymore, zeroing the length produces a deallocation:
x.length = 5_000_000;
x.length = 0;

So a basic strategy to face your problem is to not let the GC work:


import std.stdio: writefln;

void main() {
    auto x = new real[5_000_000];

    foreach (i; 0 .. 1_000) {
        int x_len = 0;

        foreach (j; 0 .. 5_000_000) {
            x[x_len] = j;
            x_len++;
        }

        writefln("At iteration %u, x has %u elements.", i, x_len);
    }
}


When the GC is not good enough one thing you can do is to manage the memory in a less automatic way...

Bye,
bearophile