determining if a void* points to a valid Object

[Sean Kelly]

Luís Marques wrote:
> Hello all,
> 
> I'm making a transition of a code base from C to D. I wish to alleviate 
> the transition by making it gradual, but that requires being able to 
> distinguish D Objects from the existing C structs, given a pointer.
> 
> Could you help me with this please?
> 
> 1. You have a "void *ptr".
> 2. You have a struct NotDObject whose declaration you can control. (e.g. 
> add fields and require that they possess certain values)
> 
> How do you determine with fairly good reliability if ptr points to an 
> Object or to a NotDObject struct?

It would be a horrible hack, but you might be able to test whether the 
location reserved for the vtbl ptr points to a location where vtbls are 
known to reside.  The ABI might be of help here: 
http://www.digitalmars.com/d/abi.html  You will have to ask Walter or do 
some sleuthing to sort out how to determine this address range, however.


Sean