linux-kernel - Re: powerpc/xmon: Fix opcode being uninitialized in print_insn

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Message-Id: <4496VZ4JGRz9s9L@ozlabs.org>
Date:   Thu, 28 Feb 2019 20:21:10 +1100 (AEDT)
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     Nathan Chancellor <natechancellor@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Joel Stanley <joel@....id.au>
Subject: Re: powerpc/xmon: Fix opcode being uninitialized in print_insn_powerpc

On Tue, 2019-02-26 at 05:38:55 UTC, Nathan Chancellor wrote:
> When building with -Wsometimes-uninitialized, Clang warns:
> 
> arch/powerpc/xmon/ppc-dis.c:157:7: warning: variable 'opcode' is used
> uninitialized whenever 'if' condition is false
> [-Wsometimes-uninitialized]
>   if (cpu_has_feature(CPU_FTRS_POWER9))
>       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> arch/powerpc/xmon/ppc-dis.c:167:7: note: uninitialized use occurs here
>   if (opcode == NULL)
>       ^~~~~~
> arch/powerpc/xmon/ppc-dis.c:157:3: note: remove the 'if' if its
> condition is always true
>   if (cpu_has_feature(CPU_FTRS_POWER9))
>   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> arch/powerpc/xmon/ppc-dis.c:132:38: note: initialize the variable
> 'opcode' to silence this warning
>   const struct powerpc_opcode *opcode;
>                                      ^
>                                       = NULL
> 1 warning generated.
> 
> This warning seems to make no sense on the surface because opcode is set
> to NULL right below this statement. However, there is a comma instead of
> semicolon to end the dialect assignment, meaning that the opcode
> assignment only happens in the if statement. Properly terminate that
> line so that Clang no longer warns.
> 
> Fixes: 5b102782c7f4 ("powerpc/xmon: Enable disassembly files (compilation changes)")
> Link: https://github.com/ClangBuiltLinux/linux/issues/390
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/e7140639b1de65bba435a6bd772d1349

cheers