new T[size] vs .reserve - alloca

[Nick Treleaven]

On 05/02/2013 22:15, monarch_dodra wrote:
> On Tuesday, 5 February 2013 at 21:14:32 UTC, Nick Treleaven wrote:
>> On 05/02/2013 21:13, Nick Treleaven wrote:
>>> I've just tried it with dmd 2.059 (haven't upgraded yet)
>>
>> sorry, 2.060
>
> Right, it's "alias" being finicky, because "args.length" isn't an actual
> variable (it's a property). The problem is not so much that it can't be
> "read" at compile time, that the compiler doesn't know what to alias to.
>
> I'll file a bug report to try and see if we can't get a better message.

OK, please post the link if/when you file it.

> Use a named variable, or use a manifest constant:

This works, thanks.

> //----
> import std.stdio;
> import core.stdc.stdlib:alloca;
>
> T* stack(T)(void* m = alloca(T.sizeof))
> {
>      return cast(T*)m;
> }
> T[] stack(T, alias N)(void* m = alloca(T.sizeof * N))
> {
>      return (cast(T*)m)[0 .. N];
> }
>
> void main(string[] args)
> {
>      auto n = args.length;
>      int[] arr = stack!(int, n)();
> }
> //----