On 12/31/2008, MS Zune mp3 players froze up globally. No response to any request, even after reset/reboot. It turns out that such a massive disaster is caused by a simple bug in the rtc.c (real-time clock) module. Here below is the buggy code.
#define ORIGINYEAR 1980 // the begin year
...
...
//------------------------------------------------------------------------------
//
// Function: ConvertDays
//
// Local helper function that split total days since Jan 1, ORIGINYEAR into
// year, month and day
//
// Parameters:
//
// Returns:
// Returns TRUE if successful, otherwise returns FALSE.
//
//------------------------------------------------------------------------------
BOOL ConvertDays(UINT32 days, SYSTEMTIME* lpTime)
{
int dayofweek, month, year;
UINT8 *month_tab;
//Calculate current day of the week
dayofweek = GetDayOfWeek(days);
year = ORIGINYEAR;
while (days > 365)
{
if (IsLeapYear(year))
{
if (days > 366)
{
days -= 366;
year += 1;
}
}
else
{
days -= 365;
year += 1;
}
}
// Determine whether it is a leap year
month_tab = (UINT8 *)((IsLeapYear(year))? monthtable_leap : monthtable);
for (month=0; month<12; month++)
{
if (days <= month_tab[month])
break;
days -= month_tab[month];
}
month += 1;
lpTime->wDay = days;
lpTime->wDayOfWeek = dayofweek;
lpTime->wMonth = month;
lpTime->wYear = year;
return TRUE;
}
Year 2008 is a leap year, it has 366 days. Whoops! It's stuck (days = 366) in the while loop FOREVER.