CODEWITHSUNDEEP
c++inheritanceconstructordestructor
Azodious
Azodious

Reputation: 13872

Inheritance hierarchy: Constructor & Destructor execution sequence

Here http://www.parashift.com/c++-faq-lite/multiple-inheritance.html section [25.14] says

The very first constructors to be executed are the virtual base classes anywhere in the hierarchy.

I tried to verify it using following program:

           A (pure virtual)
           |
           B
           |
           C
(virtual)/   \ (virtual)
       E       D
         \   /
           F
           |
           G (pure virtual)
           |
           H

each class has a c'tor and virtual d'tor. the output is as follows:

A
B
C
E
D
F
G
H
~H
~G
~F
~D
~E
~C
~B
~A
Press any key to continue . . .

but as per quote virtual base classes constructors should be executed first.

what did I understand wrong?

EDIT: To clear my question, As per my understanding this behaviour has nothing to do with whether a base class is virtual or not. but quote insists on Virtual Base class. am I clear or something fishy there?

Upvotes: 6

Views: 1098

Answers (1)

Eran
Eran

Reputation: 22020

Virtual base classes cannot be constructed if the classes they inherit from are not constructed first. So in your case, non-virtual base classes are constructed because the virtual ones depend on them: C can't be constructed until A and Bare. Therefore, A and B are indeed constructed before C, even though C is virtually inherited.

Upvotes: 6

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