Question

I have created a server program, and a certain error has occurred twice where the function ‘clock()’ has returned a negative value (and crashed the server). Both times it occurred when the program had been running for more than 100 hours, on a Windows 32-bit VPS.

Here’s the setup I have in main.cpp (cut where appropriate):

while (1) {
    Sleep(STEP);

            //execute main code like connection handling, AI, etc.

    //check for clock error
    if (clock() < 0) {
        //error saved here

                //close server
        return 0;
    }
}

That’s it, pretty simple. clock() is used throughout the rest of the program extensively, so when it glitches up like this it causes a lot of problems.

I am wondering, why does it return a negative value, and how can I fix it?

Thanks.

Answer 1

According to Microsoft’s documentation it can return -1 if “the amount of elapsed time is unavailable”. Unfortunately they don’t explain how the time would be unavailable.

The definition of clock_t is long which is a 32-bit signed value – it can hold 2**31 before it overflows. The value of CLOCKS_PER_SECOND is 1000, so it should be good for 596 hours.