undefined reference to WinMain@16 or similar 'unusual' main() entry point reference (especially for visual-studio).
You may have missed to choose the right project type with your actual IDE. The IDE may want to bind e.g. Windows Application projects to such entry point function (as specified in the missing reference above), instead of the commonly used int main(int argc, char** argv); signature.
If your IDE supports Plain Console Projects you might want to choose this project type, instead of a windows application project.
Here are case1 and case2 handled in more detail from a real world problem.