C + + Learning Path (10): implementation efficiency introduced by virtual inheritance

This article does not know what name to take, for the moment so called, directly to see the scene to understand. An excerpt from the Deep Exploration of C + + object model

Point3D origin, *pt = &origin;

(1) origin.x = 0;

(2) pt->x = 0

Both of these code execution results are the same, but are there any differences in execution efficiency?

(1) If Point3D is a normal struct, ordinary class, ordinary single inheritance or multiple inheritance, the execution efficiency of member X is exactly the same, because X's position in the class is offset and fixed at compile time (no virtual function is introduced). (2) If Point3D is virtual inherited from a base class, then PT cannot be determined at compile time to point to which class type, that is, cannot determine the offset position of x at compile time. Therefore, this access operation must be deferred to the executor, which can be resolved by an additional indirect boot, and the execution efficiency is slower than (1)

C + + Learning Path (10): implementation efficiency introduced by virtual inheritance