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

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Date:   Fri, 21 Jun 2019 07:29:48 +0000
From:   Joel Stanley <joel@....id.au>
To:     Mathieu Malaterre <malat@...ian.org>
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

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

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
>