Why can’t I do polymorphism with normal variables?

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The answer is copy semantics.

When you pass an object by value in C++, e.g. printArea(Shape shape) a copy is made of the object you pass. And if you pass a derived class to this function, all that’s copied is the base class Shape. If you think about it, there’s no way the compiler could do anything else.

Shape shapeCopy = circle;

shapeCopy was declared as a Shape, not a Circle, so all the compiler can do is construct a copy of the Shape part of the object.

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  3. Why doesn’t polymorphism work without pointers/references?
  4. What is a reference variable in C++?
  5. Reason to Pass a Pointer by Reference in C++?
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  8. C++ standard: dereferencing NULL pointer to get a reference? [duplicate]
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  10. how does the ampersand(&) sign work in c++? [duplicate]
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  12. Passing references to pointers in C++
  13. Difference between pointer to a reference and reference to a pointer
  14. What’s the meaning of * and & when applied to variable names?
  15. error: invalid initialization of non-const reference of type ‘int&’ from an rvalue of type ‘int’
  16. What is the difference between std::reference_wrapper and a simple pointer?
  17. Why doesn’t reference-to-member exist in C++?
  18. Confusion about pointers and references in C++
  19. C++: difference between ampersand “&” and asterisk “*” in function/method declaration?
  20. Why do some people prefer “T const&” over “const T&”?
  21. dereferencing a pointer when passing by reference
  22. Static global variables in C++
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  24. Where ampersand “&” can be put when passing argument by reference?
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