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Subject: Re: [PATCH 04/21] powerpc: Mark both tmp variables as unused
To:     Mathieu Malaterre <malat@debian.org>,
        Michael Ellerman <mpe@ellerman.id.au>
Cc:     linux-kernel@vger.kernel.org, Paul Mackerras <paulus@samba.org>,
        Jiri Slaby <jslaby@suse.com>, linuxppc-dev@lists.ozlabs.org
References: <20180225172236.29650-1-malat@debian.org>
 <20180225172236.29650-5-malat@debian.org>
From:   Christophe LEROY <christophe.leroy@c-s.fr>
Message-ID: <3f881ec2-eb0f-77e6-f1c5-95530b8f84ad@c-s.fr>
Date:   Wed, 14 Mar 2018 11:38:13 +0100
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Le 25/02/2018 à 18:22, Mathieu Malaterre a écrit :
> Since the value of `tmp` is never intended to be read, declare both `tmp`
> variables as unused. Fix warning (treated as error in W=1):

What about using fault_in_pages_readable() instead ?

Christophe

> 
>    CC      arch/powerpc/kernel/signal_32.o
> arch/powerpc/kernel/signal_32.c: In function ‘sys_swapcontext’:
> arch/powerpc/kernel/signal_32.c:1048:16: error: variable ‘tmp’ set but not used [-Werror=unused-but-set-variable]
>    unsigned char tmp;
>                  ^~~
> arch/powerpc/kernel/signal_32.c: In function ‘sys_debug_setcontext’:
> arch/powerpc/kernel/signal_32.c:1234:16: error: variable ‘tmp’ set but not used [-Werror=unused-but-set-variable]
>    unsigned char tmp;
>                  ^~~
> cc1: all warnings being treated as errors
> 
> Signed-off-by: Mathieu Malaterre <malat@debian.org>
> ---
>   arch/powerpc/kernel/signal_32.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
> index a46de0035214..492f03451877 100644
> --- a/arch/powerpc/kernel/signal_32.c
> +++ b/arch/powerpc/kernel/signal_32.c
> @@ -1045,7 +1045,7 @@ long sys_swapcontext(struct ucontext __user *old_ctx,
>   		     struct ucontext __user *new_ctx,
>   		     int ctx_size, int r6, int r7, int r8, struct pt_regs *regs)
>   {
> -	unsigned char tmp;
> +	unsigned char tmp __maybe_unused;
>   	int ctx_has_vsx_region = 0;
>   
>   #ifdef CONFIG_PPC64
> @@ -1231,7 +1231,7 @@ int sys_debug_setcontext(struct ucontext __user *ctx,
>   {
>   	struct sig_dbg_op op;
>   	int i;
> -	unsigned char tmp;
> +	unsigned char tmp __maybe_unused;
>   	unsigned long new_msr = regs->msr;
>   #ifdef CONFIG_PPC_ADV_DEBUG_REGS
>   	unsigned long new_dbcr0 = current->thread.debug.dbcr0;
>