Size of a bitfield member?

Question

Would anyone know how to extract the size of a bit-field member. The below code naturally gives me the size of an integer, but how do I find out how many bits or b

Answer 1

Here is a little bit tricky generalized version:

#include 
#include 
#include 
#include 
using namespace std;

template 
T umaxof()
{
      T t;
      memset(&t, 0xFF, sizeof(T));
      return t;
}

template 
size_t bitsof(const T& umax)
{
    return bitset(umax).count();
}

int main() 
{
    struct A
    {
        uint32_t bf1:19;
        uint32_t bf2:1;
    };

    cout << bitsof(umaxof().bf1) << "\n";
    cout << bitsof(umaxof().bf2) << "\n";

    return 0;
}

It can be tried out at https://ideone.com/v4BiBH

Note: Works with unsigned bit fields only.