Calling virtual functions inside constructors

by

Calling virtual functions from a constructor or destructor is dangerous and should be avoided whenever possible. All C++ implementations should call the version of the function defined at the level of the hierarchy in the current constructor and no further.

The C++ FAQ Lite covers this in section 23.7 in pretty good detail. I suggest reading that (and the rest of the FAQ) for a followup.

Excerpt:

[…] In a constructor, the virtual call mechanism is disabled because overriding from derived classes hasn’t yet happened. Objects are constructed from the base up, “base before derived”.

[…]

Destruction is done “derived class before base class”, so virtual functions behave as in constructors: Only the local definitions are used – and no calls are made to overriding functions to avoid touching the (now destroyed) derived class part of the object.

EDIT Corrected Most to All (thanks litb)

More Related Contents:

  1. C++ “virtual” keyword for functions in derived classes. Is it necessary?
  2. Can I call a base class’s virtual function if I’m overriding it?
  3. C++ virtual function return type
  4. Why do we not have a virtual constructor in C++?
  5. Is the ‘override’ keyword just a check for a overridden virtual method?
  6. What are the differences between overriding virtual functions and hiding non-virtual functions?
  7. Override a member function with different return type
  8. Force all classes to implement / override a ‘pure virtual’ method in multi-level inheritance hierarchy
  9. Calling a virtual function from the constructor
  10. Overriding public virtual functions with private functions in C++
  11. What is this weird colon-member (” : “) syntax in the constructor?
  12. Can I call a constructor from another constructor (do constructor chaining) in C++?
  13. Can a class member function template be virtual?
  14. What is a converting constructor in C++ ? What is it for?
  15. Do built-in types have default constructors?
  16. Conversion constructor vs. conversion operator: precedence
  17. Scope of variables in if statements
  18. How can i use member initialization list to initialize an array?
  19. Do I really need to implement user-provided constructor for const objects?
  20. Can class template constructors have a redundant template parameter list in c++20
  21. What is the performance cost of having a virtual method in a C++ class?
  22. Struct Constructor in C++?
  23. Initializing a union with a non-trivial constructor
  24. Constructor initialization Vs assignment
  25. No matching function for call to Class Constructor
  26. Object oriented programming in Haskell
  27. Using C++ base class constructors?
  28. Performance penalty for working with interfaces in C++?
  29. C++ Member Initializer List
  30. How can I initialize C++ class data members in the constructor?

Leave a Comment