| Message ID | 20190306123717.5334-1-leon@kernel.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [rdma-rc,v1] overflow: Fix -Wtype-limits compilation warnings | expand |
On Wed, Mar 06, 2019 at 02:37:17PM +0200, Leon Romanovsky wrote: > From: Leon Romanovsky <leonro@mellanox.com> > > Attempt to use check_shl_overflow() with inputs of unsigned type > produces the following compilation warnings. > > drivers/infiniband/hw/mlx5/qp.c: In function _set_user_rq_size_: > ./include/linux/overflow.h:230:6: warning: comparison of unsigned > expression >= 0 is always true [-Wtype-limits] > _s >= 0 && _s < 8 * sizeof(*d) ? _s : 0; \ > ^~ > drivers/infiniband/hw/mlx5/qp.c:5820:6: note: in expansion of macro _check_shl_overflow_ > if (check_shl_overflow(rwq->wqe_count, rwq->wqe_shift, > &rwq->buf_size)) > ^~~~~~~~~~~~~~~~~~ > ./include/linux/overflow.h:232:26: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits] > (_to_shift != _s || *_d < 0 || _a < 0 || \ > ^ > drivers/infiniband/hw/mlx5/qp.c:5820:6: note: in expansion of macro _check_shl_overflow_ > if (check_shl_overflow(rwq->wqe_count, rwq->wqe_shift, &rwq->buf_size)) > ^~~~~~~~~~~~~~~~~~ > ./include/linux/overflow.h:232:36: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits] > (_to_shift != _s || *_d < 0 || _a < 0 || \ > ^ > drivers/infiniband/hw/mlx5/qp.c:5820:6: note: in expansion of macro _check_shl_overflow_ > if (check_shl_overflow(rwq->wqe_count, rwq->wqe_shift,&rwq->buf_size)) > ^~~~~~~~~~~~~~~~~~ > > Fixes: 0c66847793d1 ("overflow.h: Add arithmetic shift helper") > Signed-off-by: Leon Romanovsky <leonro@mellanox.com> > Changelog v0->v1: > * fixed wrong checks > include/linux/overflow.h | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/include/linux/overflow.h b/include/linux/overflow.h > index 40b48e2133cb..a47fb6046c0a 100644 > +++ b/include/linux/overflow.h > @@ -227,10 +227,10 @@ > typeof(d) _d = d; \ > u64 _a_full = _a; \ > unsigned int _to_shift = \ > - _s >= 0 && _s < 8 * sizeof(*d) ? _s : 0; \ > + (_s == 0 || _s > 0) && _s < 8 * sizeof(*d) ? _s : 0; \ I think this is just trading a tautological compare gcc happens to know about today (_s >= 0) with one it currently doesn't (_s == 0 || _s > 0) Maybe cc the various people that helped review this macro and see if we can find another solution? Jason
On Wed, Mar 06, 2019 at 04:44:04PM +0000, Jason Gunthorpe wrote: > On Wed, Mar 06, 2019 at 02:37:17PM +0200, Leon Romanovsky wrote: > > From: Leon Romanovsky <leonro@mellanox.com> > > > > Attempt to use check_shl_overflow() with inputs of unsigned type > > produces the following compilation warnings. > > > > drivers/infiniband/hw/mlx5/qp.c: In function _set_user_rq_size_: > > ./include/linux/overflow.h:230:6: warning: comparison of unsigned > > expression >= 0 is always true [-Wtype-limits] > > _s >= 0 && _s < 8 * sizeof(*d) ? _s : 0; \ > > ^~ > > drivers/infiniband/hw/mlx5/qp.c:5820:6: note: in expansion of macro _check_shl_overflow_ > > if (check_shl_overflow(rwq->wqe_count, rwq->wqe_shift, > > &rwq->buf_size)) > > ^~~~~~~~~~~~~~~~~~ > > ./include/linux/overflow.h:232:26: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits] > > (_to_shift != _s || *_d < 0 || _a < 0 || \ > > ^ > > drivers/infiniband/hw/mlx5/qp.c:5820:6: note: in expansion of macro _check_shl_overflow_ > > if (check_shl_overflow(rwq->wqe_count, rwq->wqe_shift, &rwq->buf_size)) > > ^~~~~~~~~~~~~~~~~~ > > ./include/linux/overflow.h:232:36: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits] > > (_to_shift != _s || *_d < 0 || _a < 0 || \ > > ^ > > drivers/infiniband/hw/mlx5/qp.c:5820:6: note: in expansion of macro _check_shl_overflow_ > > if (check_shl_overflow(rwq->wqe_count, rwq->wqe_shift,&rwq->buf_size)) > > ^~~~~~~~~~~~~~~~~~ > > > > Fixes: 0c66847793d1 ("overflow.h: Add arithmetic shift helper") > > Signed-off-by: Leon Romanovsky <leonro@mellanox.com> > > Changelog v0->v1: > > * fixed wrong checks > > include/linux/overflow.h | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/include/linux/overflow.h b/include/linux/overflow.h > > index 40b48e2133cb..a47fb6046c0a 100644 > > +++ b/include/linux/overflow.h > > @@ -227,10 +227,10 @@ > > typeof(d) _d = d; \ > > u64 _a_full = _a; \ > > unsigned int _to_shift = \ > > - _s >= 0 && _s < 8 * sizeof(*d) ? _s : 0; \ > > + (_s == 0 || _s > 0) && _s < 8 * sizeof(*d) ? _s : 0; \ > > I think this is just trading a tautological compare gcc happens to > know about today (_s >= 0) with one it currently doesn't (_s == 0 || > _s > 0) > > Maybe cc the various people that helped review this macro and see if > we can find another solution? I would be glad to see other solution, but I don't know such. > > Jason
Kees, Rasmus, Do you have any idea how to fix this warning while we are compiling check_shl_overflow() user with W=1? https://patchwork.kernel.org/patch/10841079/ Thanks On Wed, Mar 06, 2019 at 02:37:17PM +0200, Leon Romanovsky wrote: > From: Leon Romanovsky <leonro@mellanox.com> > > Attempt to use check_shl_overflow() with inputs of unsigned type > produces the following compilation warnings. > > drivers/infiniband/hw/mlx5/qp.c: In function _set_user_rq_size_: > ./include/linux/overflow.h:230:6: warning: comparison of unsigned > expression >= 0 is always true [-Wtype-limits] > _s >= 0 && _s < 8 * sizeof(*d) ? _s : 0; \ > ^~ > drivers/infiniband/hw/mlx5/qp.c:5820:6: note: in expansion of macro _check_shl_overflow_ > if (check_shl_overflow(rwq->wqe_count, rwq->wqe_shift, > &rwq->buf_size)) > ^~~~~~~~~~~~~~~~~~ > ./include/linux/overflow.h:232:26: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits] > (_to_shift != _s || *_d < 0 || _a < 0 || \ > ^ > drivers/infiniband/hw/mlx5/qp.c:5820:6: note: in expansion of macro _check_shl_overflow_ > if (check_shl_overflow(rwq->wqe_count, rwq->wqe_shift, &rwq->buf_size)) > ^~~~~~~~~~~~~~~~~~ > ./include/linux/overflow.h:232:36: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits] > (_to_shift != _s || *_d < 0 || _a < 0 || \ > ^ > drivers/infiniband/hw/mlx5/qp.c:5820:6: note: in expansion of macro _check_shl_overflow_ > if (check_shl_overflow(rwq->wqe_count, rwq->wqe_shift,&rwq->buf_size)) > ^~~~~~~~~~~~~~~~~~ > > Fixes: 0c66847793d1 ("overflow.h: Add arithmetic shift helper") > Signed-off-by: Leon Romanovsky <leonro@mellanox.com> > --- > Changelog v0->v1: > * fixed wrong checks > --- > include/linux/overflow.h | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/include/linux/overflow.h b/include/linux/overflow.h > index 40b48e2133cb..a47fb6046c0a 100644 > --- a/include/linux/overflow.h > +++ b/include/linux/overflow.h > @@ -227,10 +227,10 @@ > typeof(d) _d = d; \ > u64 _a_full = _a; \ > unsigned int _to_shift = \ > - _s >= 0 && _s < 8 * sizeof(*d) ? _s : 0; \ > + (_s == 0 || _s > 0) && _s < 8 * sizeof(*d) ? _s : 0; \ > *_d = (_a_full << _to_shift); \ > - (_to_shift != _s || *_d < 0 || _a < 0 || \ > - (*_d >> _to_shift) != _a); \ > + (_to_shift != _s || !(*_d > 0 || *_d == 0) || \ > + !(_a > 0 || _a == 0) || (*_d >> _to_shift) != _a); \ > }) > > /** > -- > 2.19.1 >
On Wed, 2019-03-06 at 14:37 +0200, Leon Romanovsky wrote: > From: Leon Romanovsky <leonro@mellanox.com> > > Attempt to use check_shl_overflow() with inputs of unsigned type > produces the following compilation warnings. > > drivers/infiniband/hw/mlx5/qp.c: In function _set_user_rq_size_: > ./include/linux/overflow.h:230:6: warning: comparison of unsigned > expression >= 0 is always true [-Wtype-limits] > _s >= 0 && _s < 8 * sizeof(*d) ? _s : 0; \ > ^~ > drivers/infiniband/hw/mlx5/qp.c:5820:6: note: in expansion of macro _check_shl_overflow_ > if (check_shl_overflow(rwq->wqe_count, rwq->wqe_shift, > &rwq->buf_size)) > ^~~~~~~~~~~~~~~~~~ > ./include/linux/overflow.h:232:26: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits] > (_to_shift != _s || *_d < 0 || _a < 0 || \ > ^ > drivers/infiniband/hw/mlx5/qp.c:5820:6: note: in expansion of macro _check_shl_overflow_ > if (check_shl_overflow(rwq->wqe_count, rwq->wqe_shift, &rwq->buf_size)) > ^~~~~~~~~~~~~~~~~~ > ./include/linux/overflow.h:232:36: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits] > (_to_shift != _s || *_d < 0 || _a < 0 || \ > ^ > drivers/infiniband/hw/mlx5/qp.c:5820:6: note: in expansion of macro _check_shl_overflow_ > if (check_shl_overflow(rwq->wqe_count, rwq->wqe_shift,&rwq->buf_size)) > ^~~~~~~~~~~~~~~~~~ > > Fixes: 0c66847793d1 ("overflow.h: Add arithmetic shift helper") > Signed-off-by: Leon Romanovsky <leonro@mellanox.com> > --- > Changelog v0->v1: > * fixed wrong checks > --- > include/linux/overflow.h | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/include/linux/overflow.h b/include/linux/overflow.h > index 40b48e2133cb..a47fb6046c0a 100644 > --- a/include/linux/overflow.h > +++ b/include/linux/overflow.h > @@ -227,10 +227,10 @@ > typeof(d) _d = d; \ > u64 _a_full = _a; \ > unsigned int _to_shift = \ > - _s >= 0 && _s < 8 * sizeof(*d) ? _s : 0; \ > + (_s == 0 || _s > 0) && _s < 8 * sizeof(*d) ? _s : 0; \ > *_d = (_a_full << _to_shift); \ > - (_to_shift != _s || *_d < 0 || _a < 0 || \ > - (*_d >> _to_shift) != _a); \ > + (_to_shift != _s || !(*_d > 0 || *_d == 0) || \ > + !(_a > 0 || _a == 0) || (*_d >> _to_shift) != _a); \ > }) > > /** Reviewed-by: Bart Van Assche <bvanassche@acm.org>
On Wed, 2019-03-06 at 16:44 +0000, Jason Gunthorpe wrote: > On Wed, Mar 06, 2019 at 02:37:17PM +0200, Leon Romanovsky wrote: > > diff --git a/include/linux/overflow.h b/include/linux/overflow.h > > index 40b48e2133cb..a47fb6046c0a 100644 > > +++ b/include/linux/overflow.h > > @@ -227,10 +227,10 @@ > > typeof(d) _d = d; \ > > u64 _a_full = _a; \ > > unsigned int _to_shift = \ > > - _s >= 0 && _s < 8 * sizeof(*d) ? _s : 0; \ > > + (_s == 0 || _s > 0) && _s < 8 * sizeof(*d) ? _s : 0; \ > > I think this is just trading a tautological compare gcc happens to > know about today (_s >= 0) with one it currently doesn't (_s == 0 || > _s > 0) Since it is uncommon to write (_s >= 0) as (_s == 0 || _s > 0) my hope is that the gcc maintainers won't consider it interesting to make gcc report a warning about the latter expression. Bart.
On Thu, Mar 07, 2019 at 08:14:01AM -0800, Bart Van Assche wrote: > On Wed, 2019-03-06 at 16:44 +0000, Jason Gunthorpe wrote: > > On Wed, Mar 06, 2019 at 02:37:17PM +0200, Leon Romanovsky wrote: > > > diff --git a/include/linux/overflow.h b/include/linux/overflow.h > > > index 40b48e2133cb..a47fb6046c0a 100644 > > > +++ b/include/linux/overflow.h > > > @@ -227,10 +227,10 @@ > > > typeof(d) _d = d; \ > > > u64 _a_full = _a; \ > > > unsigned int _to_shift = \ > > > - _s >= 0 && _s < 8 * sizeof(*d) ? _s : 0; \ > > > + (_s == 0 || _s > 0) && _s < 8 * sizeof(*d) ? _s : 0; \ > > > > I think this is just trading a tautological compare gcc happens to > > know about today (_s >= 0) with one it currently doesn't (_s == 0 || > > _s > 0) > > Since it is uncommon to write (_s >= 0) as (_s == 0 || _s > 0) my hope is > that the gcc maintainers won't consider it interesting to make gcc report > a warning about the latter expression. Thanks Bart, Once they do such report, we will find a way to overcome it too. It is unlikely that it will happen in near future. Thanks > > Bart.
diff --git a/include/linux/overflow.h b/include/linux/overflow.h index 40b48e2133cb..a47fb6046c0a 100644 --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -227,10 +227,10 @@ typeof(d) _d = d; \ u64 _a_full = _a; \ unsigned int _to_shift = \ - _s >= 0 && _s < 8 * sizeof(*d) ? _s : 0; \ + (_s == 0 || _s > 0) && _s < 8 * sizeof(*d) ? _s : 0; \ *_d = (_a_full << _to_shift); \ - (_to_shift != _s || *_d < 0 || _a < 0 || \ - (*_d >> _to_shift) != _a); \ + (_to_shift != _s || !(*_d > 0 || *_d == 0) || \ + !(_a > 0 || _a == 0) || (*_d >> _to_shift) != _a); \ }) /**