On 04/14/2015 06:56 PM, Ben Pfaff wrote: > On Tue, Apr 14, 2015 at 03:16:22PM -0700, Andy Zhou wrote: >> On Tue, Apr 14, 2015 at 2:55 PM, Russell Bryant <rbry...@redhat.com> wrote: >>> On 04/14/2015 05:51 PM, Andy Zhou wrote: >>>> Gcc complains about: >>>> lib/perf-counter.c:43:13: error: ignoring return value of 'read', >>>> declared with attribute warn_unused_result [-Werror=unused-result] >>>> read(fd__, counter, sizeof(*counter)); >>>> >>>> Signed-off-by: Andy Zhou <az...@nicira.com> >>>> >>>> --- >>>> v1->v2: Combine two 'if's into using only one. >>>> --- >>>> lib/perf-counter.c | 6 +++--- >>>> 1 file changed, 3 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/lib/perf-counter.c b/lib/perf-counter.c >>>> index 7bd7834..a6e63ac 100644 >>>> --- a/lib/perf-counter.c >>>> +++ b/lib/perf-counter.c >>>> @@ -39,9 +39,9 @@ static int fd__ = 0; >>>> uint64_t >>>> perf_counter_read(uint64_t *counter) >>>> { >>>> - if (fd__ > 0) { >>>> - read(fd__, counter, sizeof(*counter)); >>>> - } else { >>>> + int size = sizeof *counter; >>> >>> Minor nit ... this should be size_t instead of int. >>> >> Thanks, I wlll make the suggested changes. > > I'm pretty sure that using size_t instead of int will actually bust > this. read returns ssize_t, a signed type, and C says that in an > expression like "ssize_t < size_t" the left-hand operand gets > converted to size_t. Thus, if "read" returns -1, it gets converted to > SIZE_MAX, which is not less than sizeof *counter. > > If I'm correct, then size should be declared as int or ssize_t. >
Oops, thanks for catching that, Ben. -- Russell Bryant _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev