When is it time for a 1.0 feature freeze?

Sean Kelly sean at f4.ca
Sun Sep 3 11:03:00 PDT 2006

Stewart Gordon wrote:
> Walter Bright wrote:
> <snip>
>> 1) Few programmers realize that C/C++'s malloc/free/new/delete *never* 
>> (and I emphasize NEVER) return memory to the operating system. All 
>> free/delete do is return memory to the memory pool managed by the 
>> runtime library, not the operating system. In order to actually return 
>> memory to the operating system, one has to write their own memory 
>> management code, which is a significant (and necessarily non-portable) 
>> effort. Hardly anyone does that.
> <snip>
> Never?  I can't believe you've tried every implementation out there, 
> including your own, and found the same.
> Or does the spec forbid free or delete to return memory to the OS?  I 
> can't for the life of me see why this would be.

Memory can only be allocated and freed in pages, and a memory page can 
obviously only be returned to the OS if it is completely empty.  Some 
allocators will do this (HOARD, for example), but they typically try to 
re-use them first.  Generally, only pages used for huge allocations are 
returned to the OS when they are freed, and I think DMD's GC does this 
as well.


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