Cleaned up C++

[John Colvin via Digitalmars-d]

On Thursday, 23 April 2015 at 18:37:47 UTC, Walter Bright wrote:
> On 4/23/2015 1:10 AM, bearophile wrote:
>> Walter Bright:
>>
>>> On 4/22/2015 2:58 PM, bearophile wrote:
>>>> D is less stack-friendly than Ada (and probably Rust too),
>>>
>>> ??
>>
>> In Ada standard library you have safe fixed-size 
>> stack-allocated associative
>> arrays. In D you can't even allocate safely a 
>> dynamically-sized 1D array on the
>> stack, and forget about doing it for 2D. Enough said.
>
> I used to use alloca() here and there, but eventually removed 
> it all. The trouble is, there are three array sizes:
>
>    a) 0
>    b) 1
>    c) arbitrarily large
>
> Dynamic stack allocation works for none of them. What does work 
> is a fixed size stack allocation with failover to using 
> malloc/free, which is what Phobos' scopebuffer does. It's 
> analogous to the "small string optimization".
>
> I don't agree with your assessment at all.

I used to think this was totally wrong, but over time I've come 
to see your point.

The ideal for me would be a dynamically sized stack array (C99 
style, not alloca) with a compile-time maximum size. Then you 
wrap that in a library type that decides/defines what to do when 
the size is exceeded (e.g. move to GC heap a la scopeBuffer), but 
in practice it's not a big win over just stack allocating the 
maximum size all the time (again, like scopeBuffer).