linux-kernel - [PATCH] powerpc/xmon: Fix opcode being uninitialized in print_insn

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Date:   Mon, 25 Feb 2019 22:38:55 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Joel Stanley <joel@....id.au>,
        Nathan Chancellor <natechancellor@...il.com>
Subject: [PATCH] powerpc/xmon: Fix opcode being uninitialized in print_insn_powerpc

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>
---
 arch/powerpc/xmon/ppc-dis.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/xmon/ppc-dis.c b/arch/powerpc/xmon/ppc-dis.c
index 9deea5ee13f6..27f1e6415036 100644
--- a/arch/powerpc/xmon/ppc-dis.c
+++ b/arch/powerpc/xmon/ppc-dis.c
@@ -158,7 +158,7 @@ int print_insn_powerpc (unsigned long insn, unsigned long memaddr)
     dialect |= (PPC_OPCODE_POWER5 | PPC_OPCODE_POWER6 | PPC_OPCODE_POWER7
 		| PPC_OPCODE_POWER8 | PPC_OPCODE_POWER9 | PPC_OPCODE_HTM
 		| PPC_OPCODE_ALTIVEC | PPC_OPCODE_ALTIVEC2
-		| PPC_OPCODE_VSX | PPC_OPCODE_VSX3),
+		| PPC_OPCODE_VSX | PPC_OPCODE_VSX3);
 
   /* Get the major opcode of the insn.  */
   opcode = NULL;
-- 
2.21.0