On Saturday, February 11, 2012 10:51:36 H. S. Teoh wrote:
> This brings up an interesting point: what does the GC do if you have an
> array that's continually appended to, and also shrunk from the front?
> That is:
>
> ubyte[] buf;
> while ( ... ) {
> consumeData(buf[0]);
> buf = buf[1 .. $];
>
> ubyte x = getMoreData();
> buf ~= x;
> }
>
> Will such a program "leak memory" in the sense that the memory chunk
> allocated to buf will grow larger and larger, even though its initial
> segment is never accessed again? Or is the GC smart enough to only
> reallocate the needed size when the memory chunk is moved (at some point
> when it has no more space to append x)?
>
> If the GC is smart enough, then this kind of construct could be used
> instead of copying overlapping ranges.
The memory blocks don't grow. When an array no longer has enough room to
increase its size, and you append to it, a new block is allocated, and the
array is moved to there. Any slices which refer to the original block still
refer to it. And when a garbage collection cycle is run and a memory block has
no references to it, it's collected. The only "leaking" that occurs is that
once no more slices refer to a particular portion of a memory block, that
portion is no longer accessible until the block has been recycled.
If you haven't read this article yet, you really should:
http://www.dsource.org/projects/dcollections/wiki/ArrayArticle
- Jonathan M Davis
