Skip to main content


Showing posts from January, 2009

How To Prove Code Review is Important

The infamous Zune 30GB failures were traced to a leapyear issue, and apparently they use some code we can see in the Freescale codebase. Take a look at the following sample of code, which determines the year from the day number (counting from January 1, 1980). I don't know about you, but the infinite loop is immediately obvious.  On a leapyear, the main loop continues when days = 366  and the incrementing is never reached, because days > 366  fails. Am I naive to think that even a casual code review would have caught this in a moment? year = ORIGINYEAR; /* = 1980 */ while (days > 365) { if (IsLeapYear(year)) { if (days > 366) { days -= 366; year += 1; } } else { days -= 365; year += 1; } } UPDATE: Fixed formatting issues. It looked fine when I posted it, honest!