Forward declaring an enum in C++

by

Forward declaration of enums is possible since C++11. Previously, the reason enum types couldn’t be forward declared was because the size of the enumeration depended on its contents. As long as the size of the enumeration is specified by the application, it can be forward declared:

enum Enum1;                     // Illegal in C++03 and C++11; no size is explicitly specified.
enum Enum2 : unsigned int;      // Legal in C++11.
enum class Enum3;               // Legal in C++11, because enum class declarations have a default type of "int".
enum class Enum4: unsigned int; // Legal C++11.
enum Enum2 : unsigned short;    // Illegal in C++11, because Enum2 was previously declared with a different type.

More Related Contents:

  1. Referring to c++ enums [closed]
  2. c++ Making a code that displays equations and keep getting the “expression must have integral or unscoped enum type” error
  3. Why is enum class preferred over plain enum?
  4. Is there a simple way to convert C++ enum to string?
  5. How to easily map c++ enums to strings
  6. C++: Print out enum value as text
  7. C++ string to enum
  8. Should I use #define, enum or const?
  9. Are C++ enums signed or unsigned?
  10. Enumerate over an enum in C++
  11. String to enum in C++
  12. Is it possible to determine if a type is a scoped enumeration type?
  13. How can I output the value of an enum class in C++11
  14. What is the underlying type of a c++ enum?
  15. Extending enums in C++?
  16. The usage of anonymous enums
  17. Pros and cons of using nested C++ classes and enumerations?
  18. Difference between Enum and Define Statements
  19. How to check if enum value is valid?
  20. Detect when multiple enum items map to same value
  21. Enum vs Strongly typed enum
  22. Why do you use typedef when declaring an enum in C++?
  23. what is the size of an enum type data in C++?
  24. Equivalent of “using namespace X” for scoped enumerations?
  25. generating random enums
  26. namespaces for enum types – best practices
  27. Do C++ enums Start at 0?
  28. Why must an enumeration’s size be provided when it is forward declared?
  29. Signedness of enum in C/C99/C++/C++x/GNU C/GNU C99
  30. How can I extend a lexical cast to support enumerated types?

Leave a Comment