On Mon, 18 Apr 2011 11:21:46 -0400, Graham Fawcett <fawc...@uwindsor.ca>
wrote:
On Mon, 18 Apr 2011 10:03:10 -0400, Steven Schveighoffer wrote:
On Mon, 18 Apr 2011 09:44:38 -0400, lenochware <lenochw...@gmail.com>
wrote:
== Quote from Steven Schveighoffer (schvei...@yahoo.com)'s article
On Mon, 18 Apr 2011 04:31:26 -0400, %u <lenochw...@gmail.com> wrote:
> Is it necessary free memory allocated for member of structure, like
> in C? I
> suppose not (we have gc). Example:
>
> struct BITMAP {
> (...)
> ubyte[] pixels;
> }
>
> BITMAP* bitmap = new BITMAP;
> bitmap.pixels = new ubyte[100*100];
> (...)
>
> // delete bitmap.pixels; //not necessary?
>
> delete bitmap;
It is not necessary, because pixels will be collected by the GC
sometime in the future. It will *not* free pixel's data by calling
delete on the BITMAP pointer.
Just a note, you may be tempted to use a destructor do effect the
above (as is done in C++ commonly), but this is a very big mistake.
So what is "correct" way to manage structures like BITMAP? Don't bother
with
freeing memory at all?
In most cases yes. Freeing memory manually is dangerous (the compiler
cannot verify that there are no other references to that memory), and
should only be used when optimizing performance, or to workaround
runtime deficiencies like false pointers.
In essence, you should avoid freeing memory unless you know what you are
doing. It's very possible you do know that it's OK.
Would "bitmap.pixels = null;" be a safe compromise? If you know you're
not going to use "pixels" any more, this would mark it as reclaimable,
but any other references to the array will keep it alive.
The recommended alternative to destruction is to use clear, since it runs
the appropriate finalizers, plus sets it to null.
If you delete bitmap, the runtime sets it to null already. So nothing
would be referencing pixels.
But yes, setting to null cannot ever hurt. It does not accomplish any
freeing of memory immediately though.
-Steve
