On 12/30/2015 12:29 PM, Julia Lawall wrote: > > > On Wed, 30 Dec 2015, Andrzej Hajda wrote: > >> Unsigned expressions cannot be lesser than zero. Presence of comparisons >> 'unsigned (<|<=|>|>=) 0' often indicates a bug, usually wrong type of >> variable. >> The patch beside finding such comparisons tries to eliminate false positives, >> mainly by bypassing range checks. >> >> gcc can detect such comparisons also using -Wtype-limits switch, but it warns >> also in correct cases, making too much noise. >> >> Signed-off-by: Andrzej Hajda <a.ha...@samsung.com> >> --- >> v4: added range check detection, added full check in case value holds a >> result >> of signed function >> v3: added bool type >> v2: added --all-includes option >> --- >> Hi Julia, >> >> This version adds range check detection, as a result false positives are >> almost >> fully eliminated. Most of kernel patches have been already sent and accepted, >> but some new bugs appeared since then. I will prepare bugfixes soon. >> >> I have enountered one issue, the patch does not detect range check in >> drivers/leds/leds-tca6507.c:716: >> if (ret != 0 || reg < 0 || reg >= NUM_LEDS) >> >> Simplified check, responsible for detectin range checks: >> @@ >> expression v, c; >> @@ >> >> * (\( v < 0 \| v <= 0 \)) || (\( v >= c \| v > c \)) >> >> Is it a bug or expected behavior? Maybe consequence of left-to-right >> associativity? > > Yes, it would be an associativity problem. Could you try with || ... > added to the right end of your pattern? That should allow it to let the > disjunctions appear anywhere at top level, but I'm not sure to what extent > it works when the pattern already contains a disjunction. You could also > try > > A || ... || B || ... >
"A || ... || B" does the trick. Regards Andrzej -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
