Statically initialize anonymous union in C++

Question

I am trying to statically initialize the following structure in Visual Studio 2010:

struct Data
{
   int x;
   union
   {
      const Data* data;
      struc         


        

Answer 1

You can make this work if all your union types are pointers, by using a void pointer as the first element of the union. All pointers can be converted to a void pointer, so your union can be initialized with an arbitrary pointer type. For the given example, you get:

struct Data
{
   int x;
   union
   {
      const void* unused;
      const Data* data;
      struct {int x; int y; }*; //Not sure this works written like this
      const char* asChar;
      const int*  asInt;
   };
};

static Data d1;
static Data d2 = {2, &d1};
static Data d3 = {1, "Hello, world!"};

The other possibility is to do this in C instead. In C you can specify which part of the union is initialized. Using your original struct (and giving your structure the name asStruct):

static Data d1;
static Data d2 = {2, &d1};
static Data d3 = {3, {.asStruct = {0,0}}