Maybe the least used
feature in all of
C++. Used mostly by
crazed MFC developers and rarely ever practical in
real code. Used to avoid
repetition in
class hierarchies where the lower levels use
multiple inheritance and the higher levels
inherit from the same
base class.
As in : A -> B.
A -> C.
B+C -> D.
Class B and C must derive A
virtually.
See also:
templates as template parameters,
explicit instantiation,
placement new for other obscure features of the language.