OpenGL and SFML Clock not restarting correctly - c++

Question

I am currently working making a maze game with OpenGL.
I want to create a timer to keep track of the time that the user spends completing each maze. I am using the SFML Clock to try to keep track of this time.
I have the following set up for the first maze:
maze.draw();
if(mazeOneIteration == 1){
mazeOneIteration++;
mazeOneClock.restart();
}
char timeStr1[100];
char levelStr[100];
sprintf(levelStr, "Level: %d", levelNum);
sprintf(timeStr1, "Time: %.2fs", mazeOneClock.getElapsedTime().asSeconds());
//std::cout << timeStr1 << std::endl;
std::cout << mazeOneClock.getElapsedTime().asSeconds() << std::endl;
glUniformMatrix4fv(modelLoc, 1, GL_FALSE, glm::value_ptr(glm::mat4(1.0)));
box.draw();
text.setFontSize(20);
text.draw("User: zsloan112" , 20, 15);
text.draw(levelStr, getSize().x - 100, getSize().y - 20);
text.draw(timeStr1, 20, getSize().y - 20);
Since this is running in my game loop this block of code is being run 60 times per second, so I only one to restart and set the clock to 0 the very first time it is ran, hence the if statement restarting the clock.
My issue is that when I use sprintf to insert the time into the timeStr1 and it is displayed the time stays at 0 seconds.
How would I get the clock to correctly restart once the first time this block of code is executed, then continue to count the time?

Answer 1

I'm going to provide you with a bit of criticism on your code. I you where applying for a job and showed me this code, I wouldn't hire you.
You using sprintf. This is a particularly bad sign. Not only are you using sprintf, you're also using it with a fixed size array of char. While it's probably going to be fine in this example, it's indicative of a deeper problem. In C++, you should never find any of the s*printf functions -- there's simply no use for it. Instead just use std::string. It will allow you to do exactly what you need without any potential problems:
Replace:
char timeStr1[100];
char levelStr[100];
sprintf(levelStr, "Level: %d", levelNum);
sprintf(timeStr1, "Time: %.2fs", mazeOneClock.getElapsedTime().asSeconds());
With:
auto const levelStr = "Level: "s + std::to_string(level);
auto const timeStr1 = "Time: "s + mazeOneClock.getElapsedTime().asSeconds();
Second, look into std::chrono. Not because it's better per say, but simply because it's part of the standard library. SFML is from before std::chrono existed, so it's no surprise that it has it's own clock, but you should stick to the standard library when you have no reason not to.
When you're trying to measure elapsed time, std::chrono::steady_clock should be your default option.
Things to read:
http://en.cppreference.com/w/cpp/string
http://en.cppreference.com/w/cpp/chrono/steady_clock