128. Arithmetic Edge Cases-II

Question.6

A developer needs to compute the difference between two timestamps. Both are uint32_t. The current time may be less than the start time if the timer has wrapped. Which approach correctly handles this?

Option A:

uint32_t elapsed = current - start;  // Unsigned subtraction

Option B:

int32_t elapsed = (int32_t)(current - start);

Option C:

uint32_t elapsed = (current >= start) ?
   current - start : start - current;

Which is correct for a free-running 32-bit timer that wraps around?

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Option A — unsigned subtraction naturally handles wrap-around
Option B — signed cast is needed to detect negative elapsed time
Option C — must check which is larger to avoid underflow
None — timer wrap-around cannot be handled in software

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