array construction without heap alloc

[Frank Benoit]

0ffh schrieb:
> 
> I compiled this using D1 (DMD):
> 
>   void bar( int a, int b )
>   {
>     int[2] arr=[a,b];
>     int brr;
>     int[] crr;
>     crr.length=2;
>     func( arr );
>     printf("%p %p\n",&arr,arr.ptr);
>     printf("%p\n",&brr);
>     printf("%p %p\n",&crr,crr.ptr);
>   }
> 
> It gives me &arr==arr.ptr, which is near &brr and &crr,
> while crr.ptr is somewhere completely different.
> I suppose that kinda proofs it. =)
> Hope it's helpful.
> 
> regards, frank

Sorry, but this does a heap allocation. I forgot to mention how i detect
it. I used obj2asm to get the assembly of the object file. Using the
array literal will cause a call to the d runtime _d_arrayliteralT
function, which uses heap allocation.

On IRC "Hxal" posted a template magic solution. It goes like this:

struct StaticArray(T, size_t S){
	T[S] array;
}
StaticArray!(typeof(T[0]), T.length) staticArray(T...)(T values){
	StaticArray!(typeof(T[0]), T.length) x;
	foreach(i,v; values)
		x.array[i] = v;
	return x;
}

Usage is:

  void bar( int a, int b ){
    func( staticArray( a, b ).array )
  }

I wonder why arrayliterals are allocated on the heap.
You always have the .dup option.