error: uint64_t was not declared in this scope when compiling C++ program

Question

I am trying out a simple program to print the timestamp value of steady_clock as shown below:

#include <iostream>
#include <chrono>
using namespace std;
int main ()
{
  cout << "Hello World! ";
  uint64_t now = duration_cast<milliseconds>(steady_clock::now().time_since_epoch()).count();
  cout<<"Value: " << now << endl;

  return 0;
}

But whenever I am compiling like this g++ -o abc abc.cpp, I am always getting an error:

In file included from /usr/include/c++/4.6/chrono:35:0,
                 from abc.cpp:2:
/usr/include/c++/4.6/bits/c++0x_warning.h:32:2: error: #error This file requires compiler and library support for the upcoming ISO C++ standard, C++0x. This support is currently experimental, and must be enabled with the -std=c++0x or -std=gnu++0x compiler options.
abc.cpp: In function âint main()â:
abc.cpp:7:3: error: âuint64_tâ was not declared in this scope
abc.cpp:7:12: error: expected â;â before ânowâ
abc.cpp:8:22: error: ânowâ was not declared in this scope

Is there anything wrong I am doing?

Answer 1

You should include stdint.h file.

Answer 2

Obviously, I'm not following certain best practices, but just trying to get things working for you

#include <iostream>
#include <chrono>
#include <cstdint> // include this header for uint64_t

using namespace std;
int main ()
{
  {
    using namespace std::chrono; // make symbols under std::chrono visible inside this code block
    cout << "Hello World! ";
    uint64_t now = duration_cast<milliseconds>(steady_clock::now().time_since_epoch()).count();
    cout<<"Value: " << now << endl;
  }

  return 0;
}

and then compile using C++11 enabled (c++0x in your case)

g++ -std=c++0x -o abc abc.cpp