[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 <redacted>
---
 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

On Mon, Feb 25, 2019 at 9:39 PM Nathan Chancellor
[off-list ref] 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 <redacted>

haha! (shows office mates).  Nice find, and fix!
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

-- 
Thanks,
~Nick Desaulniers

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 <redacted>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

Applied to powerpc next, thanks.

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

cheers