c++/6830: Virtual table layout: wrong vcall/vbase order for primary base class
Wed Jul 3 13:25:00 GMT 2002
not a bug. You are misinterpreting the ABI spec.
(you do know about the -fdump-class-hierarchy flag don't you?) Anyway.
The V::g thunk in S's vtable uses a vcall offset that you should consider
part of S's vtable (not P's, the overridden class). So the vcall offset
is at a lower index than the vbase offsets.
This is the bit from 2.5.2 in the ABI (my emphasis)
Virtual call (vcall) offsets are used to perform ... These entries are
allocated in the virtual table for the *virtual* base class that is *most
immediately derived* from the base class containing the overridden.
Here the most immediately derived virtual base on the path from P->S->V is S.
The (ia32) vtable for V is and should be
12 vbase offset V to R
4 vbase offset V to S
0 offset to top
TI type info
.... primary vptr here
v::g final overrider
... start of secondary vtable (that for S)
-4 vcall offset (to V) for V::g thunk
8 vbase offset S to R
-4 offset to top
TI type info
vthunk(-4) to V::g
Dr Nathan Sidwell :: http://www.codesourcery.com :: CodeSourcery LLC
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