Linus with some good observations on garbage collection

[Andrei Alexandrescu]

On 4/23/11 1:05 PM, Timon Gehr wrote:
> Andrei Alexandrescu wrote:
>> Allocation and deallocation are not symmetric and as such handling them
>> in a uniform way would be a mistake that perpetuates a poor
>> understanding of the underlying realities of memory allocation and
>> object creation. I suggest you reconsider.
>
> 'char' is completely orthogonal to memory allocation and it still gets handled
> uniformly to it syntactically. So I do not really get the point here.

The point is that some naively believe "new" and "delete" are some 
simple do and undo actions and as such they somehow deserve the same 
level of support. In reality they have dramatically different issues and 
are profoundly asymmetric.

>>> And it discourages people to get informed about
>>> custom allocators etc.
>>
>> I don't see the relationship here.
>
> I cannot imagine that the syntax for them will be particularly nice after the
> removal of 'delete'. Who likes features with unnecessarily clumsy syntax?
>
>> The cost of keeping "delete" in the language is making a rarely-used,
>> dangerous facility with loosely-defined semantics straight inside the
>> language. It reflects poor language design for many reasons.
>>
>> Andrei
>
> I think we are talking about different things. I do _not_ want to use the keyword
> to somehow try to deallocate GC allocated memory. (who would actually want to do
> this anyways?) I want it for custom allocators as in
> http://www.digitalmars.com/d/2.0/memory.html. In that case, the semantics would be
> completely specified by me. Removing the keyword means ruining that use case. You
> can also find a nice, clean and strict semantic specification for delete when
> called on GC memory that works on all platforms and with all GC implementations:
> "do nothing, GC memory is managed automatically." As it is done now, I agree it is
> not particularly nice.
>
> Timon

The class-specific allocators are an exceedingly bad design carried over 
from C++. They will be deprecated from D as well.

Even C++, where the features you are talking about have existed for many 
years, is shunning their use. Good applications make very sparingly use 
of "delete" and virtually none uses class-specific allocators. 
Experience with C++ is the best proof that the delete keyword and 
class-specific allocators have no place in the D programming language.


Andrei