2016-01-05 10:49 GMT-03:00 Andrzej Hajda <a.ha...@samsung.com>: > On 01/05/2016 01:59 PM, Geyslan G. Bem wrote: >> Hello, >> >> 2016-01-04 4:45 GMT-03:00 Andrzej Hajda <a.ha...@samsung.com>: >>> 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> >>> --- >>> v6: improved range check detection (according to Julia suggestion) >>> v5: improved range check detection >>> 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 >>> --- >>> .../tests/unsigned_lesser_than_zero.cocci | 76 >>> ++++++++++++++++++++++ >>> 1 file changed, 76 insertions(+) >>> create mode 100644 scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci >>> >>> diff --git a/scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci >>> b/scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci >>> new file mode 100644 >>> index 0000000..b9c7ed8 >>> --- /dev/null >>> +++ b/scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci >>> @@ -0,0 +1,76 @@ >>> +/// Unsigned expressions cannot be lesser than zero. Presence of >>> +/// comparisons 'unsigned (<|<=|>|>=) 0' often indicates a bug, >>> +/// usually wrong type of variable. >>> +/// >>> +/// To reduce number of false positives following tests have been added: >>> +/// - parts of range checks are skipped, eg. "if (u < 0 || u > 15) ...", >>> +/// developers prefer to keep such code, >>> +/// - comparisons "<= 0" and "> 0" are performed only on results of >>> +/// signed functions/macros, >> Why common unsigned comparisons with <= 0 are not being detected? I >> think that it misleads the code reading and induces further bugs. >> Just reading "var <= 0" infers that var can receive signed value. The >> be clear the comparison should be against zero only "var == 0" or >> depending of the context "!var". >> > > Many developers prefer to use "unsigned <= 0" comparison, as more > descriptive > and less fragile. See for example for the last phrase of Linus email[1]. > > [1]: http://permalink.gmane.org/gmane.linux.kernel/2054063
I got it. Tks. > > Regards > Andrzej > -- Regards, Geyslan G. Bem hackingbits.com -- 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/
