On 7 January 2012 20:59, bearophile <bearophileh...@lycos.com> wrote:
> Manu:
>
> > The tendency to encourage use of dynamic arrays will be a major problem.
>
> I don't know how much big that problem will be, D dynamic arrays are quite
> handy, but I agree that static arrays need to be encouraged more in D (and
> currently most algorithms of Phobos don't work with static arrays (you need
> to slice them first)).
>
A slice doesn't produce a GC allocation does it?
I thought a slice was just a pointer-length pair. Should live on the
stack/in regs?
...so slicing static arrays shouldn't be a problem right?
> Currently even this code with a stack-allocated fixed size array causes a
> heap allocation (DMD):
>
> void main() {
> int[2] a = [1, 2];
> }
>
> ASM, optimized build:
>
> __Dmain comdat
> push EAX
> push EAX
> mov EAX,offset FLAT:_D12TypeInfo_xAi6__initZ
> push EBX
> push 8
> push 2
> push EAX
> call near ptr __d_arrayliteralTX ; heap allocation
> add ESP,8
> mov EBX,EAX
> mov dword ptr [EAX],1
> mov ECX,EBX
> push EBX
> lea EDX,0Ch[ESP]
> mov dword ptr 4[EBX],2
> push EDX
> call near ptr _memcpy
> add ESP,0Ch
> xor EAX,EAX
> pop EBX
> add ESP,8
> ret
>
What the hell is it allocating?
Surely that's not necessary... that's gotta be fixable?
> I have suggested to add a safer version of VLAs to avoid some
> heap-allocated dynamic arrays:
> http://d.puremagic.com/issues/show_bug.cgi?id=5348
+1!!
I'm surprised this already isn't supported!
