Hi Johan, On Mon, Oct 19, 2015 at 11:51 PM, Johan Hedberg <johan.hedberg@xxxxxxxxx> wrote: > Hi Jakub, > > On Mon, Oct 19, 2015, Jakub Pawlowski wrote: >> On Mon, Oct 19, 2015 at 10:35 PM, Johan Hedberg <johan.hedberg@xxxxxxxxx> wrote: >> > Hi Jakub, >> > >> > On Mon, Oct 19, 2015, Jakub Pawlowski wrote: >> >> due to type promotions in C this code was failing on some platforms. >> >> >> >> src/device.c:2016:8: error: format specifies type 'unsigned short' but the >> >> argument has type 'uint8_t' (aka 'unsigned char') [-Werror,-Wformat] >> >> properties, uuid_str); >> >> ^~~~~~~~~~ >> >> /build/falco/usr/include/bits/stdio2.h:39:7: note: expanded from macro 'sprintf' >> >> __VA_ARGS__) >> >> ^ >> >> --- >> >> src/device.c | 2 +- >> >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> >> >> diff --git a/src/device.c b/src/device.c >> >> index 0d3a655..b4e6d53 100644 >> >> --- a/src/device.c >> >> +++ b/src/device.c >> >> @@ -2015,7 +2015,7 @@ static void store_chrc(struct gatt_db_attribute *attr, void *user_data) >> >> >> >> sprintf(handle, "%04hx", handle_num); >> >> bt_uuid_to_string(&uuid, uuid_str, sizeof(uuid_str)); >> >> - sprintf(value, GATT_CHARAC_UUID_STR ":%04hx:%02hx:%s", value_handle, >> >> + sprintf(value, GATT_CHARAC_UUID_STR ":%04hx:%02x:%s", value_handle, >> >> properties, uuid_str); >> > >> > Wouldn't the right format specifier be %hhx in this case? >> >> So it was compiling fine on my machine, but when it was compiling for >> all possible platforms for ChromeOS those errors came up. >> The very proper thing would be probably to use "PRIu8" from <inttypes.h> >> but then I found good explanation: >> >> ""printf() is a variadic function. Its optional arguments( and only >> those ) get promoted according to default argument promotions( >> 6.5.2.2. p6 ). >> >> Since you are asking for integers, integer promotions are applied in >> this case, and types you mention get promoted to int. ( and not >> unsigned int because C )"" >> source: http://stackoverflow.com/questions/26362386/why-is-the-format-specifier-for-uint8-t-and-uint16-t-the-same-u >> >> so I understand that this uint8_t will get promoted to int, and >> displayed properly. >> I manually tested it for 0, 127, and 255 and looks like it's >> formatting just fine. > > It's a bit unclear from your answer: do you still get warnings/errors > with %hhx or not? Looking at the warning you got: > > "argument has type 'uint8_t' (aka 'unsigned char')" > > and the printf(3): > > "hh A following integer conversion corresponds to a signed char or > unsigned char argument" > > It'd still seem like %hhx shouldn't give a warning. Even though %x might > work too being able to be more specific in the type specification > doesn't seem like a bad thing. Ok, I've build version with %hhx on all platforms we have and it worked well with no warnings. I'll update patch. > > Johan -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
