maybe_unused

To prevent warnings from occuring due to unused variables, before the variable type maybe_unused

int main()
{
    [[maybe_unused]] double pi { 3.14159 };
    [[maybe_unused]] double gravity { 9.8 };
    [[maybe_unused]] double phi { 1.61803 };
 
    // the above variables will not generate unused variable warnings
 
    return 0;
}