Cloning DynamicStructs

[Vaci]

Hi,

Should it be possible to use capnp::clone() to copy a DynamicStruct? 

This code currently doesn't compile:

#include <capnp/dynamic.h>

#include <capnp/message.h>

#include "foo.capnp.h"

int main() {

  capnp::MallocMessageBuilder mb;

  auto root = mb.initRoot<Foo>();

  auto a = root.asReader();

  auto a2 = capnp::clone(a); // succeeds

  auto b = capnp::toDynamic(a);

  auto b2 = capnp::clone(b); // fails

}

...but I'm not clear what it is about DynamicStructs that make them less copyable?

Cheers,

Vaci

[Kenton Varda]

No, there's no fundamental limitation here. I think we just need an overload of `clone()` for this that accounts for the subtle API differences with `DynamicStruct`, e.g. passing the `Schema` in various places.

-Kenton

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[Vaci]

I (eventually) figured out the very obvious solution -  just cast the DynamicStruct back to an AnyStruct, (which is clonable), and keep track of the schema elsewhere!