Bit-fields “In-class initialization” results in “error: lvalue required as left operand of assignment”

Question

struct bitfield {
  int i = 0;  // ok
  int j : 8 = 0;  // error: lvalue required as left operand of assignment
};

What is the correct syntax to in

Answer 1

You cannot (in C++11) in-class initialize bitfields.

In MSVC and gcc (with extensions), the anonymous union and struct code lets you get around this a bit.

struct bitfield {
  int i = 0;  // ok
  union {
    uint32_t raw = 0;
    struct {
      int j : 8;
      int x : 3;
    };
  };
};

where we mix a fixed size raw with a union over bitfields, then in-class initialize the raw element.