Consider:

auto foo(T)(T a) {
	T b;  // Error: cannot access frame pointer of main.X
	b.data[] = 1;
	return b;
}

void main() {
	struct X {
		this(int) {}
		int[4096] data;
	}
	foo(X());	
}

Note the error is because you cannot construct the main.X object without a frame pointer.

You could do `T b = a` here to get a's frame pointer, but it would also copy all of a's data, which is expensive and unnecessary.

Is there a way to only copy a's frame pointer into b?

(Note: this is just an illustrative example, real problem here: https://issues.dlang.org/show_bug.cgi?id=13935)

On 01/06/15 23:14, Peter Alexander via Digitalmars-d-learn wrote:
> auto foo(T)(T a) {
>     T b;  // Error: cannot access frame pointer of main.X
>     b.data[] = 1;
>     return b;
> }
> 
> void main() {
>     struct X {
>         this(int) {}
>         int[4096] data;
>     }
>     foo(X());
> }
> 
> Note the error is because you cannot construct the main.X object without a frame pointer.
> 
> You could do `T b = a` here to get a's frame pointer, but it would also copy all of a's data, which is expensive and unnecessary.
> 
> Is there a way to only copy a's frame pointer into b?

The obvious hack would be

    T b = void;
    b.tupleof[$-1] = a.tupleof[$-1];

but you probably don't want to do it like that...

> (Note: this is just an illustrative example, real problem here: https://issues.dlang.org/show_bug.cgi?id=13935)

That shows a static struct, so I'm not sure it's the same problem.

artur

On Tuesday, 6 January 2015 at 23:32:25 UTC, Artur Skawina via
> That shows a static struct, so I'm not sure it's the same problem.

static structs with template alias parameters to local symbols count as nested structs.

Your solution would likely work, but yes, I'm looking for something less hacky :-)