Fabian Cenedese <Cenedese@xxxxxxxx> writes: >>> << In boilerplate $vtbl_ptr_type, what are the fields delta, index, >>> pfn and delta2 used for? >> >>> >>> So is there somewhere a description of these fields? I would like to >>> get the address of a virtual method of an object (so pObj->vptr->index >>> ->method or something like that). >> >>A virtual table is just a list of function pointers; you can think of >>as a struct whose fields have the type of pointers to functions >>implementing the methods. >> >>Perhaps you are looking at a pointer-to-member? Or a thunk, which is >>a bit of code used for multiple inheritance? >> >>In this context, "delta" is typically the offset from the start of the >>object to the start of the object from which the method is inherited. >>That is, normally delta == 0, but in cases of multiple inheritance it >>may have a non-zero value. >> >>The "index" field is presumably the index into the virtual table. > > Thanks for the information. I don't use multiple inheritance here, > so delta is 0 and index is 8 which is about right (9th entry in vtable). > > Maybe I should have given more info about my problem here. I was > specifically looking for the types and limits of these fields. I already > have a working solution to get method pointers and call them, even for > virtual methods. But I have one case where this fails. The problem seems > to be that the offset between object address and virtual table is bigger > than 0x9000. But the delta2 field seems to be a signed short, so it > can't hold this value bigger 0x7FFF. I was now wondering if this is > really a limitation or if I have to compute things differently. That's why > I was looking for a description of these fields. > >>Sorry, I don't know what pfn or delta2 are without more context. > > pfn should be the address of the normal method, or delta2 should > be the offset to the virtual table. In my case it has a value of -16000, > but that's not the real value, it's also not the limit, it's just some > value I don't know what to do with it. Where does delta2 come from? Where do you see the name? Where do you see the value? As far as I know the compiler never stores the offset between the object address and the virtual table. Ian
