Compiler Error C2864

'member-name' : a static data member with an in-class initializer must have non-volatile const integral type

Remarks

To initialize a static data member that's defined as volatile, non-const, or not an integral type, use a member-definition statement. They can't be initialized in a declaration.

Example

This example generates C2864:

// C2864.cpp
// compile with: /c
class B  {
private:
   int a = 3;   // OK
   static int b = 3;   // C2864
   volatile static int c = 3;   // C2864
   volatile static const int d = 3;   // C2864
   static const long long e = 3;   // OK
   static const double f = 3.33;   // C2864
};

This example shows how to fix C2864:

// C2864b.cpp
// compile with: /c
class C  {
private:
   int a = 3;
   static int b; // = 3; C2864
   volatile static int c; // = 3; C2864
   volatile static const int d; // = 3; C2864
   static const long long e = 3;
   static const double f; // = 3.33; C2864
};

// Initialize static volatile, non-const, or non-integral
// data members when defined, not when declared:
int C::b = 3;
volatile int C::c = 3;
volatile const int C::d = 3;
const double C::f = 3.33;