Bottom line re GC in D

[John Colvin via Digitalmars-d]

On Tuesday, 8 July 2014 at 11:22:42 UTC, John Colvin wrote:
> On Tuesday, 8 July 2014 at 06:23:13 UTC, Jeremy DeHaan wrote:
>
>> I remember that slices was one thing you would no longer have 
>> if you disable the GC, but I can't think of any others.
>
> You can definitely use slices without the GC and they are still 
> awesome without the GC.
> What you cannot do is create them with `new` or call the 
> builtin ~ or ~= (concatenate and append respectively) operators 
> on slices. Slice literals may also cause allocations, but not 
> always:
>
> enum ctA = [3, 4];
>
> void main() @nogc //@nogc is transitive, marking main as @nogc
>                   //enforces no GC activity in the entire 
> program.
> {
>     //these statements are all guaranteed not to GC-allocate
>     int[2] a = [1, 2];
>     assert(a[0] == 1 && a[1] == 2);
>     a = ctA;
>     assert(a[0] == 3 && a[1] == 4);
>     assert(a == [3,4]);
>
>     import core.stdc.stdlib;
>     auto data = cast(int*)calloc(100_000, int.sizeof);
>     auto callocedSlice = data[0 .. 100_000];
>     auto subSlice = callocedSlice[40 .. $ - 600];
>
>     //these cause GC allocation and as such
>     //will not compile in an @nogc function.
> //    int[] s0 = [1, 2];
> //    auto s1 = [3,4];
> }

I should also include this example:

int[10] a = [0,1,2,3,4,5,6,7,8,9]; //a static array, on the stack
auto s = a[]; //a normal slice, backed by stack memory*
auto s1 = a[3 .. 5]; //ditto