http://www.mozilla.org/projects/nspr/reference/html/prinrvl.html#21002 says "In C, the difference between any two fields is signed", which is wrong. The guide is correct that "(PRIntervalTime)(PR_IntervalNow() - epoch) > interval" deserves the (PRUint32) cast, but the reason is that PRUint32 will be promoted to signed int (only) on systems where int has more than 32 bits of precision.

This was already fixed in https://developer.mozilla.org/en-US/docs/PR_IntervalNow$compare?to=132922&from=132921 and the old version has been archived to http://www-archive.mozilla.org/projects/nspr/reference/html/prinrvl.html#21002