Defining static members in C++

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(1.) Why is it not allowed in C++ ?

From Bjarne Stroustrup’s C++ Style and Technique FAQ:

A class is typically declared in a header file and a header file is typically included into many translation units. However, to avoid complicated linker rules, C++ requires that every object has a unique definition. That rule would be broken if C++ allowed in-class definition of entities that needed to be stored in memory as objects.

(2.) Why are const members allowed to
be initialized ?

[dirkgently said it better]

(3.) Does this mean static variables
in C++ are not initialized with 0 as
in C?

As far as I know, as long as you declare the static member var in a .cpp it will be zero-initialized if you don’t specify otherwise:

// in some .cpp
int Test::j; // j = int();

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  2. Stack, Static, and Heap in C++
  3. Static array vs. dynamic array in C++
  4. Static variables initialisation order
  5. Initialize static variables in C++ class?
  6. Defining static const integer members in class definition
  7. Static member initialization in a class template
  8. Prevent static initialization order “fiasco”, C++
  9. Static variables in C++
  10. When are static and global variables initialized?
  11. Are function static variables thread-safe in GCC?
  12. C++ where to initialize static const
  13. Template static variable
  14. How to initialize a static const member in C++?
  15. C++: When (and how) are C++ Global Static Constructors Called?
  16. What makes a static variable initialize only once?
  17. constexpr static member before/after C++17
  18. C++ singleton vs. global static object
  19. Are static fields inherited?
  20. Circular C++ Header Includes
  21. When should I write the keyword ‘static’ before a non-member function?
  22. Accessing static class variables in C++?
  23. static member initialization for specialized template class
  24. How do static variables in lambda function objects work?
  25. Advantages of classes with only static methods in C++
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  27. Should one never use static inline function?
  28. Static global variables in C++
  29. On local and global static variables in C++
  30. C++, static vs. namespace vs. singleton

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