Re: Storing interfaces as void[]

[David Zhang via Digitalmars-d-learn]

On Friday, 12 March 2021 at 17:46:22 UTC, Imperatorn wrote:
On Friday, 12 March 2021 at 17:37:43 UTC, David  Zhang wrote:
I want to store interfaces as untyped void[], then cast them 
back to the interface at a later time. However, it appears to 
produce garbage values on get().

Is this even possible, and if so, what is happening here? The 
alternative would be a struct { CheckedPtr self; api_fns.... }

e.g.

void register(I)(I i) {
  auto mem = new void[](I.sizeof);
  memcpy(mem.ptr, cast(void*) i, I.sizeof);

  // CheckedPtr includes a hash of fullyQualifiedName
  map[i.get_name()] = CheckedPtr!I(mem.ptr);
}

I get(I)() {
  // basically cast(I) p
  return map[I.get_name()].as!I();
}

Have you tried using Variant or jsvar 
(https://code.dlang.org/packages/arsd-official%3Ajsvar)? 🤔

It doesn't appear to support interfaces, see opAssign at line 682.

It occurs to me that I.sizeof == 8 which is just enough for the 
vtbl, but not enough for an implementation ptr. Maybe it's a 
pointer to a {self, vtbl} pair? SomeClass.sizeof == 16, which is 
enough storage for both...