Compilation error for union

问题

can somebody please explain why the following program causing the compilation problem. I have compiled the source code over VS2013.

#include <iostream>
using namespace std;

// Do not work
union myuni
{
    string str;
};

void main()
{

}

Does union require the fixed length size while declaring it? The same scenario works fine with structure.

回答1:

You cannot have a string in a union as the former contains a constructor.

(Although allowed in C++11 this is not supported in VS2013).

来源：https://stackoverflow.com/questions/22764587/compilation-error-for-union