linux-kernel - Re: [PATCH] crypto: Fix build for clang

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Date:   Fri, 21 Jun 2019 09:44:47 +0200
From:   Mathieu Malaterre <malat@...ian.org>
To:     Joel Stanley <joel@....id.au>
Cc:     Dmitry Kasatkin <dmitry.kasatkin@...el.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Segher Boessenkool <segher@...nel.crashing.org>
Subject: Re: [PATCH] crypto: Fix build for clang

Joel,

On Fri, Jun 21, 2019 at 9:30 AM Joel Stanley <joel@....id.au> wrote:
>
> On Fri, 21 Jun 2019 at 07:13, Mathieu Malaterre <malat@...ian.org> wrote:
> >
> > The header file `longlong.h` makes uses of GNU extensions, this trigger
> > an error when compiling this code with clang. Add a special flag to make
> > clang tolerate this syntax.
>
> Another old copy of longlong.h in the kernel!
>
> This looks similar to another clang related warnings I fixed in the
> powerpc math-emu code. There's an updated version of these macros in
> GCC, and we updated the kernel version to match the GCC version. Can
> you see if a similar change would work here?
>
> https://lore.kernel.org/linuxppc-dev/43BCRQ6ZqDz9s55@ozlabs.org/
> https://git.kernel.org/torvalds/c/b682c8692442711684befe413cf93cf01c5324ea

Great ! Thanks for the pointer. Looks like a much bettter solution in
the long term. Will try asap.

> Cheers,
>
> Joel
>
> >
> > Silence the following warnings triggered using W=1:
> >
> >     CC      lib/mpi/generic_mpih-mul1.o
> >   ../lib/mpi/generic_mpih-mul1.c:37:13: error: invalid use of a cast in a inline asm context requiring an l-value: remove the cast or build with
> >         -fheinous-gnu-extensions
> >                   umul_ppmm(prod_high, prod_low, s1_ptr[j], s2_limb);
> >                   ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >   ../lib/mpi/longlong.h:824:20: note: expanded from macro 'umul_ppmm'
> >           : "=r" ((USItype) ph) \
> >                   ~~~~~~~~~~^~
> >
> > and
> >
> >     CC      lib/mpi/generic_mpih-mul2.o
> >   ../lib/mpi/generic_mpih-mul2.c:36:13: error: invalid use of a cast in a inline asm context requiring an l-value: remove the cast or build with
> >         -fheinous-gnu-extensions
> >                   umul_ppmm(prod_high, prod_low, s1_ptr[j], s2_limb);
> >                   ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >   ../lib/mpi/longlong.h:824:20: note: expanded from macro 'umul_ppmm'
> >           : "=r" ((USItype) ph) \
> >                   ~~~~~~~~~~^~
> >
> >   1 warning generated.
> >     CC      lib/mpi/generic_mpih-mul3.o
> >   ../lib/mpi/generic_mpih-mul3.c:36:13: error: invalid use of a cast in a inline asm context requiring an l-value: remove the cast or build with
> >         -fheinous-gnu-extensions
> >                   umul_ppmm(prod_high, prod_low, s1_ptr[j], s2_limb);
> >                   ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >   ../lib/mpi/longlong.h:824:20: note: expanded from macro 'umul_ppmm'
> >           : "=r" ((USItype) ph) \
> >                   ~~~~~~~~~~^~
> >
> > Or even:
> >
> >   ../lib/mpi/mpih-div.c:99:16: error: invalid use of a cast in a inline asm context requiring an l-value: remove the cast or build with -fheinous-gnu-extensions
> >                                   sub_ddmmss(n1, n0, n1, n0, d1, d0);
> >                                   ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
> >
> > Cc: Joel Stanley <joel@....id.au>
> > Cc: Masahiro Yamada <yamada.masahiro@...ionext.com>
> > Signed-off-by: Mathieu Malaterre <malat@...ian.org>
> > ---
> >  lib/mpi/Makefile | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/lib/mpi/Makefile b/lib/mpi/Makefile
> > index d5874a7f5ff9..de4d96e988a3 100644
> > --- a/lib/mpi/Makefile
> > +++ b/lib/mpi/Makefile
> > @@ -5,6 +5,13 @@
> >
> >  obj-$(CONFIG_MPILIB) = mpi.o
> >
> > +ifdef CONFIG_CC_IS_CLANG
> > +CFLAGS_generic_mpih-mul1.o  += -fheinous-gnu-extensions
> > +CFLAGS_generic_mpih-mul2.o  += -fheinous-gnu-extensions
> > +CFLAGS_generic_mpih-mul3.o  += -fheinous-gnu-extensions
> > +CFLAGS_mpih-div.o  += -fheinous-gnu-extensions
> > +endif
> > +
> >  mpi-y = \
> >         generic_mpih-lshift.o           \
> >         generic_mpih-mul1.o             \
> > --
> > 2.20.1
> >