std::string not working in anonymous union

[garob]

This code here:

enum variableType {real, str};
struct variable
{
  enum variableType type;
  union{
    double realValue;
    std::string stringValue;
  };
};

makes these errors:

member `std::string variable::<anonymous union>::stringValue' with constructor not allowed in union
member `std::string variable::<anonymous union>::stringValue' with destructor not allowed in union
member `std::string variable::<anonymous union>::stringValue' with copy assignment operator not allowed in union 

can somebody explain why please?

[helios]

Unlike C, C++ doesn't allow non-basic types in unions. You'll have to make it an std::string * and create the object dynamically.

[Bazzy]

Unlike C, C++ doesn't allow non-basic types in unions.

C doesn't have non-POD types...