Question

I have created a function to calculate the difference of 2 timeval functions. Here is the basic version of that function.

struct timeval* getDifference(struct timeval* startTime, struct timeval* finishTime)
{
    struct timeval* difference = new struct timeval;
    difference->tv_sec = finishTime->tv_sec - startTime->tv_sec;
    difference->tv_usec = finishTime->tv_usec - startTime->tv_usec;
    return difference;
}

int main()
{
    struct timeval a,b;
    struct timeval* c;
    gettimeofday(&a, NULL);
    usleep(100000);
    gettimeofday(&b, NULL);

    c = getDifference(&a, &b);
 }

What i want to know is if the usage struct timeval* c; safe? or should it be like struct timeval* c = new struct timeval;?

If it is safe then would freeing c free the difference = new struct timeval; allocated inside the function?

Answer 1

I would suggest not using pointers at all in your case. Let the arguments be references have the return be copied:

struct timeval getDifference(const struct timeval& startTime, const struct timeval& finishTime)
{
    struct timeval difference;
    difference.tv_sec = finishTime.tv_sec - startTime.tv_sec;
    difference.tv_usec = finishTime.tv_usec - startTime.tv_usec;
    return difference;
}