On Thu, 7 Mar 2019 16:35:26 -0800 Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote: > On Thu, Mar 7, 2019 at 1:46 PM Nathan Chancellor > <natechancellor@xxxxxxxxx> wrote: > > > > When building with -Wsometimes-uninitialized, Clang warns: > > > > drivers/iio/common/ssp_sensors/ssp_iio.c:95:6: warning: variable > > 'calculated_time' is used uninitialized whenever 'if' condition is false > > [-Wsometimes-uninitialized] > > > > While it isn't wrong, this will never be a problem because > > iio_push_to_buffers_with_timestamp only uses calculated_time > > on the same condition that it is assigned (when scan_timestamp > > is not zero). While iio_push_to_buffers_with_timestamp is marked > > as inline, Clang does inlining in the optimization stage, which > > happens after the semantic analysis phase (plus inline is merely > > a hint to the compiler). > > > > Fix this by just zero initializing calculated_time. > > > > Link: https://github.com/ClangBuiltLinux/linux/issues/394 > > Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx> > > Knowing that the same invariant holds across function boundaries to > protect access of unitialized values and thus undefined behavior > sounds tricky to diagnose accurately. Thanks for the patch. > Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> Applied to the togreg branch of iio.git and pushed out as testing for the autobuilders to play with it. Note this is going to be a while before it hits mainline but as it is a false (if reasonable!) warning I'm not going to rush it in as a fix. Thanks, Jonathan > > > --- > > drivers/iio/common/ssp_sensors/ssp_iio.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/iio/common/ssp_sensors/ssp_iio.c b/drivers/iio/common/ssp_sensors/ssp_iio.c > > index 645f2e3975db..e38f704d88b7 100644 > > --- a/drivers/iio/common/ssp_sensors/ssp_iio.c > > +++ b/drivers/iio/common/ssp_sensors/ssp_iio.c > > @@ -81,7 +81,7 @@ int ssp_common_process_data(struct iio_dev *indio_dev, void *buf, > > unsigned int len, int64_t timestamp) > > { > > __le32 time; > > - int64_t calculated_time; > > + int64_t calculated_time = 0; > > struct ssp_sensor_data *spd = iio_priv(indio_dev); > > > > if (indio_dev->scan_bytes == 0) > > -- > > 2.21.0 > > > >
