Is the copy constructor always called when returning by value in C++ [duplicate]

by

No. The compiler is allowed to elide the call to the copy constructor in some cases. Look up RVO (Return Value Optimization) and NRVO (Named Return Value Optimization). Also, since C++17, this optimization is guaranteed in some cases.

Additionally, if the returned type is movable, the compiler may do a move rather than a copy in some cases.

More Related Contents:

  1. What is the copy-and-swap idiom?
  2. What should main() return in C and C++?
  3. How do I execute a command and get the output of the command within C++ using POSIX?
  4. Dynamically allocating an array of objects
  5. Why should the copy constructor accept its parameter by reference in C++?
  6. What is a converting constructor in C++ ? What is it for?
  7. Why copy constructor is not called in this case?
  8. std::thread pass by reference calls copy constructor
  9. When do we have to use copy constructors?
  10. Which is more efficient: Return a value vs. Pass by reference?
  11. Why is the copy constructor not called?
  12. C++ Compiler Error C2280 “attempting to reference a deleted function” in Visual Studio 2013 and 2015
  13. Return a “NULL” object if search result not found
  14. Why user-defined move-constructor disables the implicit copy-constructor?
  15. Should I return EXIT_SUCCESS or 0 from main()?
  16. How are C++ array members handled in copy control functions?
  17. C++ return value without return statement
  18. C++ template copy constructor on template class
  19. How do I make this C++ object non-copyable?
  20. What’s the most reliable way to prohibit a copy constructor in C++?
  21. constructor invocation mechanism
  22. What’s the use of the private copy constructor in c++
  23. Why is copy constructor called instead of conversion constructor?
  24. How to make a function return a pointer to a function? (C++)
  25. Why is the copy constructor called when we pass an object as an argument by value to a method?
  26. Why am I not provided with a default copy constructor from a volatile?
  27. Copying derived entities using only base class pointers, (without exhaustive testing!) – C++
  28. Why does int main() {} compile?
  29. How do C++ progs get their return value, when a return is not specified in the function?
  30. Why are iostreams not copyable?

Leave a Comment