Alternative to time() function

Question

MISRA and AUTOSAR do not allow us to use the time() function of <ctime> (and <time.h>).

Rule 18-0-4: The time handling functions of library <ctime> shall not be used.

Is there an alternative to the time() function in C++?

There is the time library <chrono>. But there I didn't find a function that returns the current time like time(). Or am I missing something?

Answer 1

Using the <chrono> header requires a little more involvement than the time function.

You can create a time_point using std::chrono::steady_clock::now(). Subtracting two time_point instances creates a std::duration which reflects the difference in time between the two instances. You can then use a duration_cast to cast this duration to a scale of your choice (microsecond, millisecond etc.) and then use the count member function to get the actual time in unsigned type.

TL;DR You can measure elapsed time between two events by doing this:

const auto start = std::chrono::steady_clock::now(); // event 1
// something happens in between...
const auto end = std::chrono::steady_clock::now(); // event 2
const auto time_elapsed = std::chrono::duration_cast<std::chrono::microseconds>(end-start).count();

Notes:

1. time_elapsed is not a floating-point variable,
2. std::chrono::steady_clock should be preferred to std::chrono::system_clock because the former is a monotonic clock i.e. it will not be adjusted by the OS.