Compiling C++ code using __float128

I'm trying to use __float128 in my C++ program.

However I'm in trouble with compiling it.

Here is simple c++ code (test.cc):

#include <iostream>
#include <quadmath.h>

using namespace std;

int main(){
  __float128 r=0.0q;
  __float128 exp_d = expq(12.45q);

  cout << "r=" << (double)r << endl;
  cout << "exp_d=" << (double)exp_d << endl;
}

And I compile this code with

g++ test.cc -lquadmath -std=c++11

which comes with following error

error:unable to find numeric literal operator 'operateor"" q'

How can I fix it?