#include <iostream>

typedef int& (tyProc)(int& x_p0);

int* testVarRet(int& x) {
  return &x;
}

void testProcTypeParam(tyProc prc) {
  int x = 123;
  auto T1 = prc(x);
  T1 = 321;
  std::cout << x << std::endl;
}

int main()
{
  testProcTypeParam(testVarRet);
}

#include <iostream>

int& foo(int& x) {
  return x;
}

int main()
{
    int x = 100;
    auto y = foo(x);            // y is int
    decltype(auto) z = foo(x);  // z is int&
    y = 123;
    std::cout << x << ", " << y << std::endl;   // 100, 123
    z = 456;
    std::cout << x << ", " << z << std::endl;   // 456, 456

    int a = 1;
    decltype(auto) b = a;       // b is int
    decltype(auto) c = (a);     // c is int&
    b = 2;
    std::cout << a << ", " << b << std::endl;   // 1, 2
    c = 3;
    std::cout << a << ", " << c << std::endl;   // 3, 3
}