Re: [dpdk-dev] [PATCH v1] app/test: zcd needs to be initialised to fix gcc compile error

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

<snip>

> 
> Hi Honnappa,
> 
> Sorry about the delayed reply.
No problem, thank you.

> The build error trace is below, the build command used was: CC=gcc meson --
> optimization=1 --werror build1; ninja -C build1 I am not sure how I could fix
> this issue without initialising zcd.
> 
> [2339/2407] Compiling C object app/test/dpdk-
> test.p/test_ring_mt_peek_stress_zc.c.o
> FAILED: app/test/dpdk-test.p/test_ring_mt_peek_stress_zc.c.o
> gcc -Iapp/test/dpdk-test.p -Iapp/test -I../app/test -Ilib/librte_acl -
> I../lib/librte_acl -I. -I.. -Iconfig -I../config -Ilib/librte_eal/include -
> I../lib/librte_eal/include -Ilib/librte_eal/linux/include -
> I../lib/librte_eal/linux/include -Ilib/librte_eal/x86/include -
> I../lib/librte_eal/x86/include -Ilib/librte_eal/common -
> I../lib/librte_eal/common -Ilib/librte_eal -I../lib/librte_eal -Ilib/librte_kvargs -
> I../lib/librte_kvargs -Ilib/librte_metrics -I../lib/librte_metrics -
> Ilib/librte_telemetry -I../lib/librte_telemetry -Idrivers/bus/pci -
> I../drivers/bus/pci -I../drivers/bus/pci/linux -Ilib/librte_pci -I../lib/librte_pci -
> Idrivers/bus/vdev -I../drivers/bus/vdev -Ilib/librte_bitratestats -
> I../lib/librte_bitratestats -Ilib/librte_ethdev -I../lib/librte_ethdev -
> Ilib/librte_net -I../lib/librte_net -Ilib/librte_mbuf -I../lib/librte_mbuf -
> Ilib/librte_mempool -I../lib/librte_mempool -Ilib/librte_ring -I../lib/librte_ring
> -Ilib/librte_meter -I../lib/librte_meter -Ilib/librte_bpf -I../lib/librte_bpf -
> Ilib/librte_cfgfile -I../lib/librte_cfgfile -Ilib/librte_cmdline -I../lib/librte_cmdline
> -Ilib/librte_cryptodev -I../lib/librte_cryptodev -Ilib/librte_distributor -
> I../lib/librte_distributor -Ilib/librte_efd -I../lib/librte_efd -Ilib/librte_hash -
> I../lib/librte_hash -Ilib/librte_rcu -I../lib/librte_rcu -Ilib/librte_eventdev -
> I../lib/librte_eventdev -Ilib/librte_timer -I../lib/librte_timer -Ilib/librte_fib -
> I../lib/librte_fib -Ilib/librte_rib -I../lib/librte_rib -Ilib/librte_flow_classify -
> I../lib/librte_flow_classify -Ilib/librte_table -I../lib/librte_table -Ilib/librte_port
> -I../lib/librte_port -Ilib/librte_sched -I../lib/librte_sched -Ilib/librte_ip_frag -
> I../lib/librte_ip_frag -Ilib/librte_kni -I../lib/librte_kni -Ilib/librte_lpm -
> I../lib/librte_lpm -Ilib/librte_graph -I../lib/librte_graph -Ilib/librte_ipsec -
> I../lib/librte_ipsec -Ilib/librte_security -I../lib/librte_security -
> Ilib/librte_latencystats -I../lib/librte_latencystats -Ilib/librte_member -
> I../lib/librte_member -Ilib/librte_node -I../lib/librte_node -Ilib/librte_pipeline
> -I../lib/librte_pipeline -Ilib/librte_rawdev -I../lib/librte_rawdev -
> Ilib/librte_reorder -I../lib/librte_reorder -Ilib/librte_stack -I../lib/librte_stack -
> Idrivers/mempool/ring -I../drivers/mempool/ring -Idrivers/mempool/stack -
> I../drivers/mempool/stack -Idrivers/event/skeleton -
> I../drivers/event/skeleton -Idrivers/net/bonding -I../drivers/net/bonding -
> Idrivers/net/ring -I../drivers/net/ring -Ilib/librte_power -I../lib/librte_power -
> Ilib/librte_pdump -I../lib/librte_pdump -Idrivers/crypto/scheduler -
> I../drivers/crypto/scheduler -fdiagnostics-color=always -pipe -
> D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Werror -O1 -include
> rte_config.h -Wextra -Wcast-qual -Wdeprecated -Wformat-nonliteral -
> Wformat-security -Wmissing-declarations -Wmissing-prototypes -Wnested-
> externs -Wold-style-definition -Wpointer-arith -Wsign-compare -Wstrict-
> prototypes -Wundef -Wwrite-strings -Wno-packed-not-aligned -Wno-missing-
> field-initializers -march=native -mno-avx512f -DALLOW_EXPERIMENTAL_API -
> Wno-format-truncation -D_GNU_SOURCE -fno-strict-aliasing -
> DALLOW_INTERNAL_API -MD -MQ app/test/dpdk-
> test.p/test_ring_mt_peek_stress_zc.c.o -MF app/test/dpdk-
> test.p/test_ring_mt_peek_stress_zc.c.o.d -o app/test/dpdk-
> test.p/test_ring_mt_peek_stress_zc.c.o -c
> ../app/test/test_ring_mt_peek_stress_zc.c
> In file included from ../app/test/test_ring_mt_peek_stress_zc.c:5:
> ../app/test/test_ring_stress_impl.h: In function 'test_worker':
> ../app/test/test_ring.h:82:3: error: 'zcd.n1' may be used uninitialized in this
> function [-Werror=maybe-uninitialized]
>    test_ring_mem_copy(zcd->ptr2, src,
>    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>       esize, num - zcd->n1);
>       ~~~~~~~~~~~~~~~~~~~~~
> ../app/test/test_ring_mt_peek_stress_zc.c:32:26: note: 'zcd.n1' was declared
> here
>   struct rte_ring_zc_data zcd;
>                           ^~~
> In file included from ../app/test/test_ring_mt_peek_stress_zc.c:5:
> ../app/test/test_ring.h:67:2: error: '*((void *)&zcd+8)' may be used
> uninitialized in this function [-Werror=maybe-uninitialized]
>   memcpy(dst, src, sz);
>   ^~~~~~~~~~~~~~~~~~~~
> ../app/test/test_ring_mt_peek_stress_zc.c:32:26: note: '*((void *)&zcd+8)'
> was declared here
I remember seeing a similar error in test_ring_st_peek_stress_zc.c.
In the file test_ring_mt_peek_stress_zc.c, after the call to enqueue/dequeue API calls, we have:
"n = (m == n) ? n : 0;"

This is present as the code was copied from existing code. I do not see why this line is required. Can you please try to remove this line and see if it works?

>   struct rte_ring_zc_data zcd;
>                           ^~~
> In file included from ../app/test/test_ring_mt_peek_stress_zc.c:5:
> ../app/test/test_ring.h:67:2: error: 'zcd' may be used uninitialized in this
> function [-Werror=maybe-uninitialized]
>   memcpy(dst, src, sz);
>   ^~~~~~~~~~~~~~~~~~~~
> ../app/test/test_ring_mt_peek_stress_zc.c:32:26: note: 'zcd' was declared
> here
>   struct rte_ring_zc_data zcd;
>                           ^~~
> In file included from ../app/test/test_ring_mt_peek_stress_zc.c:5:
> ../app/test/test_ring.h:63:11: error: 'zcd.n1' may be used uninitialized in this
> function [-Werror=maybe-uninitialized]
>   sz = num * sizeof(void *);
>        ~~~~^~~~~~~~~~~~~~~~
> ../app/test/test_ring_mt_peek_stress_zc.c:14:26: note: 'zcd.n1' was declared
> here
>   struct rte_ring_zc_data zcd;
>                           ^~~
> In file included from ../app/test/test_ring_mt_peek_stress_zc.c:5:
> ../app/test/test_ring.h:67:2: error: '*((void *)&zcd+8)' may be used
> uninitialized in this function [-Werror=maybe-uninitialized]
>   memcpy(dst, src, sz);
>   ^~~~~~~~~~~~~~~~~~~~
> ../app/test/test_ring_mt_peek_stress_zc.c:14:26: note: '*((void *)&zcd+8)'
> was declared here
>   struct rte_ring_zc_data zcd;
>                           ^~~
> In file included from ../app/test/test_ring_mt_peek_stress_zc.c:5:
> ../app/test/test_ring.h:67:2: error: 'zcd' may be used uninitialized in this
> function [-Werror=maybe-uninitialized]
>   memcpy(dst, src, sz);
>   ^~~~~~~~~~~~~~~~~~~~
> ../app/test/test_ring_mt_peek_stress_zc.c:14:26: note: 'zcd' was declared
> here
>   struct rte_ring_zc_data zcd;
>                           ^~~
> cc1: all warnings being treated as errors [2340/2407] Compiling C object
> drivers/libtmp_...ontx2.a.p/event_octeontx2_otx2_worker_dual.c.o
> ninja: build stopped: subcommand failed.
> 
> Thanks,
> Conor.
> 
> > From: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
> > Sent: Wednesday 4 November 2020 18:48
> > To: Walsh, Conor <conor.walsh@intel.com>; Ananyev, Konstantin
> > <konstantin.ananyev@intel.com>
> > Cc: dev@dpdk.org; Chen, LingliX <linglix.chen@intel.com>; nd
> > <nd@arm.com>; Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>;
> nd
> > <nd@arm.com>
> > Subject: RE: [PATCH v1] app/test: zcd needs to be initialised to fix
> > gcc compile error
> >
> > Hi Conor,
> > 	Thanks for the patch.
> >
> > <snip>
> >
> > >
> > > When DPDK is compiled with gcc < 9 with the optimization level set
> > > to 1 gcc sees zcd in test_ring.h as possibly being uninitialised. To
> > > correct this error
> > zcd
> > > has been initialised to {0} in test_ring_mt_peek_stress_zc.c.
> > >
> > > Signed-off-by: Conor Walsh <conor.walsh@intel.com>
> > > ---
> > >  app/test/test_ring_mt_peek_stress_zc.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/app/test/test_ring_mt_peek_stress_zc.c
> > > b/app/test/test_ring_mt_peek_stress_zc.c
> > > index 7e0bd511a7..ba0acf237c 100644
> > > --- a/app/test/test_ring_mt_peek_stress_zc.c
> > > +++ b/app/test/test_ring_mt_peek_stress_zc.c
> > > @@ -11,7 +11,7 @@ _st_ring_dequeue_bulk(struct rte_ring *r, void
> > > **obj, uint32_t n,
> > >  	uint32_t *avail)
> > >  {
> > >  	uint32_t m;
> > > -	struct rte_ring_zc_data zcd;
> > > +	struct rte_ring_zc_data zcd = {0};
> > I faced similar problems when I created this test case. I refrained
> > from doing this initialization as it might mask the problems in the
> > library. Is it possible to identify which path in the library is
> > actually resulting in this error? I would prefer to fix that instead.
> >
> > >
> > >  	m = rte_ring_dequeue_zc_bulk_start(r, n, &zcd, avail);
> > >  	n = (m == n) ? n : 0;
> > > @@ -29,7 +29,7 @@ _st_ring_enqueue_bulk(struct rte_ring *r, void *
> > const
> > > *obj, uint32_t n,
> > >  	uint32_t *free)
> > >  {
> > >  	uint32_t m;
> > > -	struct rte_ring_zc_data zcd;
> > > +	struct rte_ring_zc_data zcd = {0};
> > >
> > >  	m = rte_ring_enqueue_zc_bulk_start(r, n, &zcd, free);
> > >  	n = (m == n) ? n : 0;
> > > --
> > > 2.25.1