Object arrays in D

[Steven Schveighoffer]

On Wed, 11 Apr 2012 13:07:54 -0400, Johannes Pfau <nospam at example.com>  
wrote:

> Am Tue, 10 Apr 2012 20:28:28 +0200
> schrieb Marco Leise <Marco.Leise at gmx.de>:
>
>> Am Tue, 10 Apr 2012 07:35:31 -0400
>> schrieb "Steven Schveighoffer" <schveiguy at yahoo.com>:
>>
>> > Destructors are strictly for cleaning up resources that *AREN'T*
>> > allocated by the GC.  For example anything created with C's malloc,
>> > or an open file descriptor, etc.
>>
>> This I think is a very good advice to beginners. Short and precise.
>> It is much more fun to use a new language when you can also free your
>> mind from some archaic concepts now and then :)
>>
>
> That's a dangerous advice though: You can create lots of file
> descriptors without allocating much memory. So in the worst case you
> run out of file-descriptors long before the GC calls your destructor.

This is not "dangerous" advice.  Freeing resources you own that are not  
yet freed is perfectly acceptable, and IMO, good practice.  If you own a  
resource, and it's not closed manually, you have an obligation to free  
it.  If you create a class that owns a file descriptor, and don't close it  
in the destructor, then it leaves the possibility that you have destroyed  
all references to the file descriptor, but left it open, thereby leaking  
it.

Yes, it is advisable that when you are creating unlimited numbers of  
file-descriptor owning classes, that you manually close them.  But the  
destructor is a perfectly good place to do that.

I once wrote an application that relied on the GC to close file  
descriptors, and it never ran out of file descriptors.

-Steve