The purpose of D (GC rant, long)

[Sean Kelly]

Dave wrote:
> Sean Kelly wrote:
>> Dave wrote:
>>> Sean Kelly wrote:
>>>> Now that memory is not freed when string.length is set to zero it's 
>>>> quite possible to avoid most reallocations simply by preallocating 
>>>> in buffers before using them (ie. set length to some large number 
>>>> and then 
>>>
>>> I did not know that had been changed.. Is that now part of the 
>>> language 'spec' somewhere as well?
>>
>> No.  It was implemented in 170-172 by request from Derek.  I don't 
>> know the issue number offhand.
>>
>>> I'm betting this has been discussed or at least proposed, but here 
>>> goes again; let's get an array.reserve at least for native arrays 
>>> (that could be implemented as {arr.length = nnn; arr.length = 0;}). 
>>> That way it would make for less of a hack than re/setting the length, 
>>> and also codify it as part of the language.
>>
>> I agree that this would be useful.  Though it would probably be more 
>> like:
>>
>> size_t tmp = arr.length; arr.length = nnn; arr.length = tmp;
>>
> 
> Oops, you're right..
> 
> I was curious as to how much initialization cost. I took the code 
> (bottom) and ran it three times: 1) as-is, 2) with the initialization 
> code in gc._d_newarrayi() commented out and 3) with the initialization 
> code in gcx._malloc() also commented out (along with (2))
...
> One thing I noticed is that for most/all of the _d_new* functions, 
> initialization will be done twice, once in the gcx.malloc and again in 
> the _d_new* function. I believe the extra initialization could be 
> removed in most cases (perhaps with an optional parameter to 
> gcx.malloc()?). Maybe also some syntax to support 'void' initializers 
> for heap allocated arrays?

What initialization in gcx.malloc?  The only call to memset I see has a 
debug flag.  And I believe void initializers already work for arrays.


Sean