How do I get a variant from a pointer in Delphi?

Question

I need to be able to convert a naked pointer to a variant. I know that the pointer points to a variant, but I can't seem to get it back out. A straight cast (as I pretty much thought) fails:

Result := Variant(FAddress)^

returns a compiler error: [DCC Error] E2089 Invalid typecast

I've scoured the variants.pas unit as well, but nothing jumped out at me.

Obviously I'm missing something. What is the way to do this?

Answer 1

If the pointer points at a Variant, then its type is PVariant. Type-cast it to that, and then dereference:

Result := PVariant(FAddress)^;

Better yet, declare FAddress with the right type to begin with, and then you don't need to typecast:

var
  FAddress: PVariant;

Result := FAddress^;

The compiler considers your attempted type-cast invalid because Variant is a bigger type than Pointer is. The compiler doesn't know where to get the additional data to create a full Variant value. And if the type-cast were valid, the use of the ^ operator isn't allowed on Variants anyway. You might have gotten away with this:

Result := Variant(FAddress^);

I've never liked that; if FAddress is an untyped pointer, then dereferencing it yields a value without any size or type at all, and it's just weird to type-cast such a thing.