virtual method structure

[Ian Lance Taylor]

Fabian Cenedese <Cenedese@indel.ch> writes:

> If I have a virtual method
>
> virtual unsigned long CClass::vMethod();
>
> and do in the source
>
> unsigned long (CClass::*pvm)() = &CClass::vMethod;
>
> then pvm is a structure (or pointer to it) with the elements
> short __delta
> short __index
> union __pfn_or_delta2
>         void* pfn
>         short __delta2
>
> These names come directly out of the debug info, they nowhere appear
> in the project's sources. I do see them in the elf file but I don't know if
> the values are fixed or calculated at runtime.
>
> pvm:(0,50)=s8__delta:(0,8),0,16;__index:(0,8),16,16;__pfn_or_delta2:(0,51)=u4__pfn:(0,52)=*(14,53),0,32;__delta2:(0,8),0,16;;,32,32;;

Wow, stabs debugging information.

Did you mention which version of gcc you are using?  I think you must
be using the old C++ ABI, i.e. a version of gcc earlier than 3.4,
which was released over five years ago.  I don't think I ever knew how
pointer-to-member-functions worked in that ABI.  There is no delta2 in
the current gcc ABI.

Ian