On 12/11/19 5:50 PM, Marek Polacek wrote:
On Fri, Nov 22, 2019 at 04:11:53PM -0500, Jason Merrill wrote:
On 11/8/19 4:24 PM, Marek Polacek wrote:
2) [class.cdtor] says that when a dynamic_cast is used in a constructor or
destructor and the operand of the dynamic_cast refers to the object under
construction or destruction, this object is considered to be a most derived
object.
This means that during the 'tor the vtable pointer refers to the type_info
for that class and the offset-to-top is 0. Can you use that?
I can't seem to: For e.g.
struct C : A, C2 { A *c = dynamic_cast<A*>(static_cast<C2*>(this)); };
the object under construction is C, the call to __dynamic_cast will be
__dynamic_cast (SAVE_EXPR <&((struct C *) this)->D.2119>, &_ZTI2C2, &_ZTI1A, -2)
here, OBJ is f.D.2156.D.2119 and ctx->global->ctor_object is f.D.2156. So OBJ
refers to the object under construction.
But I don't see C anywhere; CLASSTYPE_TYPEINFO_VAR of OBJTYPE is _ZTI2C2.
Am I looking into the wrong place?
Evaluating build_vfield_ref (obj, objtype) will give you the vtable
pointer, in this case &_ZTV1C + 40. And then you can get C from
DECL_CONTEXT (_ZTV1C).
Or get_tinfo_decl_dynamic (obj) will give you the type_info.
Jason
