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Tue, 26 Nov 2019 12:01:40 -0500 (EST) From: Thomas Monjalon To: "Phil Yang (Arm Technology China)" Cc: dev@dpdk.org, Bruce Richardson , "david.marchand@redhat.com" , "jerinj@marvell.com" , Honnappa Nagarahalli , "Gavin Hu (Arm Technology China)" , "Joyce Kong (Arm Technology China)" , nd , "stable@dpdk.org" Date: Tue, 26 Nov 2019 18:01:38 +0100 Message-ID: <5285313.iaM3IdUqkp@xps> In-Reply-To: References: <1573468461-25972-1-git-send-email-phil.yang@arm.com> <3677391.EzyCDiKdWj@xps> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Subject: Re: [dpdk-dev] [PATCH 1/2] mk: fix unsupported flag error on armhf architercture X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" 12/11/2019 07:40, Phil Yang (Arm Technology China): > > -----Original Message----- > > From: Thomas Monjalon > > Sent: Tuesday, November 12, 2019 2:03 PM > > To: Phil Yang (Arm Technology China) > > Cc: Bruce Richardson ; dev@dpdk.org; > > david.marchand@redhat.com; jerinj@marvell.com; Honnappa Nagarahalli > > ; Gavin Hu (Arm Technology China) > > ; Joyce Kong (Arm Technology China) > > ; nd ; stable@dpdk.org > > Subject: Re: [dpdk-dev] [PATCH 1/2] mk: fix unsupported flag error on armhf > > architercture > > > > 12/11/2019 06:25, Phil Yang (Arm Technology China): > > > From: Bruce Richardson > > > > On Mon, Nov 11, 2019 at 06:34:20PM +0800, Phil Yang wrote: > > > > > The older version (e.g. version 7.4.0 ) of GNU C compiler for the armhf > > > > > architecture doesn't support the flag '-Wno-address-of-packed- > > member', > > > > > so remove this flag for aarch32. > > > > > > > > > > Fixes: a385972c3675 ("mk: disable warning for packed member pointer") > > > > > Cc: stable@dpdk.org > > > > > > > > > > Signed-off-by: Phil Yang > > > > > Reviewed-by: Gavin Hu > > > > > Tested-by: Joyce Kong > > > > > > > > > > --- > > > > > mk/toolchain/gcc/rte.vars.mk | 2 ++ > > > > > 1 file changed, 2 insertions(+) > > > > > > > > > > diff --git a/mk/toolchain/gcc/rte.vars.mk > > b/mk/toolchain/gcc/rte.vars.mk > > > > > index 9fc7041..ec0cbbf 100644 > > > > > --- a/mk/toolchain/gcc/rte.vars.mk > > > > > +++ b/mk/toolchain/gcc/rte.vars.mk > > > > > @@ -100,7 +100,9 @@ WERROR_FLAGS += -Wno-format-truncation > > > > > endif > > > > > > > > > > # disable packed member unalign warnings > > > > > +ifneq ($(CONFIG_RTE_ARCH_ARM), y) > > > > > WERROR_FLAGS += -Wno-address-of-packed-member > > > > > +endif > > > > > > > > > You don't need to do this, as gcc will not complain about this unknown > > flag > > > > unless you have other issues in your code.[1] I think it's better to keep > > the > > > > code clean in this case, otherwise we'll have the code littered with > > > > conditionals for various flags. > > > > > > > > /Bruce > > > > > > > > [1] https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html > > > > "When an unrecognized warning option is requested (e.g., > > > > -Wunknown-warning), GCC emits a diagnostic stating that the option is > > not > > > > recognized. However, if the -Wno- form is used, the behavior is slightly > > > > different: no diagnostic is produced for -Wno-unknown-warning unless > > other > > > > diagnostics are being produced. This allows the use of new -Wno- options > > > > with old compilers, but if something goes wrong, the compiler warns that > > an > > > > unrecognized option is present." > > > > > > Thanks, Bruce. > > > > > > There are thousands of warnings with alignment when compiling for > > ARMv7 (ARMv7 supports unaligned memory access). > > > Without this new flag, the build system works fine for ARMv7. So I add this > > conditional for ARMv7 only. > > > I agree with you we should clean up the code, but it needs a lot of effort to > > achieve that. > > > This patch is going to make the ARMv7 target build successfully during this > > period. > > > > I would go the opposite direction. > > I think we should remove all warnings disablement like "-Wno-something", > > and clean the code. > > Thanks, Thomas. > > I think it is a compiler issue rather than a code defect in this case, as It cannot recognize the '-Waddress-of-packed-member' flag. > "arm-linux-gnueabihf-gcc: error: unrecognized command line option '-Waddress-of-packed-member'" > > > > > If you want to allow building ARMv7, you can just allow warnings as not > > errors. > > So we will still see something is wrong but it won't prevent from building. > > Yes. We did this already, all the alignment issues are emitted as warnings on ARMv7. > Please see these two commits: > 79fa5c2a9992 ("mk: ignore alignment errors for ARMv7") > 6433c19105e8 ("mk: generalize strict alignment warning handling") I don't know what to do with this patch. I think it is not how it should work, but you say your compiler has a real bug. Can you confirm which compiler is it? Does it prevent to compile even with -Wno-error ? Any other opinion?