Memory leak with dynamic array

[Steven Schveighoffer]

On Mon, 12 Apr 2010 15:36:19 -0400, Joseph Wakeling  
<joseph.wakeling at webdrake.net> wrote:

> Joseph Wakeling wrote:
>> (Actually I'm still having some issues with this, despite using
>> assumeSafeAppend, but more on that in a separate email.)
>
> ... solved; it's interesting to note that assumeSafeAppend has to be
> used in _exactly_ the same scope as the append ~= itself.
>
> e.g. with this loop, the memory blows up:
>
>     ////////////////////////////////////////////////////////////////
>     foreach(uint i;0..100) {
>         x.length = 0;
>
>         assumeSafeAppend(x);
>
>         foreach(uint j;0..5000)
>             foreach(uint k;0..1000)
>                 x ~= j*k;
>
>         writefln("At iteration %u, x has %u elements.",i,x.length);
>     }
>     ////////////////////////////////////////////////////////////////

This should work as you expect.  Can you produce a full code example?  Are  
you reserving space in x before-hand?

>
> ... while with this one it's OK:
>
>     ////////////////////////////////////////////////////////////////
>     foreach(uint i;0..100) {
>         x.length = 0;
>
>         foreach(uint j;0..5000) {
>             foreach(uint k;0..1000) {
>                 assumeSafeAppend(x);
>                 x ~= j*k;
>             }
>         }
>
>         writefln("At iteration %u, x has %u elements.",i,x.length);
>     }
>     ////////////////////////////////////////////////////////////////

The first assumeSafeAppend is the only one that matters.  Subsequent ones  
are wasted cycles.  I'm unsure why this one works and the other doesn't.   
Again, I need full compilable examples.

-Steve