Memory leak with dynamic array

[Joseph Wakeling]

Hello all,

This one is another 'oh God it doesn't work like C++' query ... :-)

I've been having a problem with a memory leak that I've tied down to a dynamic
array that is repeatedly resized to zero and then extended within a loop.  The
following code gives a minimal example:

////////////////////////////////////////////////////////////////////
import std.array;
import std.stdio;

void main()
{
    real[] x;

    x.length = 5000000;

    foreach(uint i;0..100) {
        x.length = 0;

        foreach(uint j;0..5000000)
            x ~= j;

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

If I run this on my system, the memory usage explodes within a very short
time, despite the fact that the length of the array is set early on, so the
memory should all be reserved.  The writefln() command confirms that the
actual number of elements always stays within the original bounds set.

I'm guessing this is down to concatenation ~ working differently from C++
vectors' push_back() command.  I have also tried using the Appender and its
put() command, but the same result happens.

I even tried moving the array declaration within the first foreach() loop, and
putting an explicit delete at the end, but to no avail.

Can anyone advise? :-)

Thanks & best wishes,

    -- Joe