Variable-length stack allocated arrays

[Andrei Alexandrescu]

grauzone wrote:
> Andrei Alexandrescu wrote:
>> grauzone wrote:
>>> Andrei Alexandrescu wrote:
>>>> grauzone wrote:
>>>>> Andrei Alexandrescu wrote:
>>>>>> grauzone wrote:
>>>>>>> bearophile wrote:
>>>>>>>> void bar(int n) {
>>>>>>>>   scope int[] a = new int[n]; // stack-allocated
>>>>>>>>   foo(a);
>>>>>>>> }
>>>>>>>
>>>>>>> Why are you making such proposals, when one of the core 
>>>>>>> developers even thought about removing normal "scope"? It's 
>>>>>>> almost 100% guaranteed that nobody will listen.
>>>>>>>
>>>>>>> I personally find it a good idea to find new ways to reduce 
>>>>>>> producing memory garbage. The D GC is slow and bad, so you'd 
>>>>>>> better avoid it.
>>>>>>>
>>>>>>> Let's make this claim: it is impossible to write high performance 
>>>>>>> applications (that need to make use of dynamic memory allocation) 
>>>>>>> in D without resorting to "unsafe" techniques. That would include 
>>>>>>> allocating memory on the stack, or manually freeing memory.
>>>>>>
>>>>>> I write high-performance code in D without resorting to unsafe 
>>>>>> techniques. Much of my code allocates arrays only in the beginning 
>>>>>> and uses them throughout.
>>>>>
>>>>> I intended to exclude this case with applications "that need to 
>>>>> make use of dynamic memory allocation". But I guess this doesn't 
>>>>> apply to programs that only allocate on initialization.
>>>>>
>>>>> So, how about programs that allocate/release memory while doing 
>>>>> computations?
>>>>
>>>> "Oil is found in the minds of men."
>>>
>>> Can you explain what this means in the context of the problem 
>>> mentioned above?
>>
>> It means that if you start with the goal of making high performance 
>> applications safe, you may achieve that. One guaranteed way to not get 
>> there is to start with a claim that it can't be done.
> 
> I just wanted to leave that "claim" for anybody to attack. But in the 
> end, solutions to this problem will only be workarounds, and programs 
> will possibly be more convoluted than their C/C++ counterparts.

C++ doesn't have stack-allocated arrays.

Andrei