2019-02-26 05:40:07

by Nathan Chancellor

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 <[email protected]>
---
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

2019-02-26 05:44:19

by Nick Desaulniers

Subject: Re: [PATCH] powerpc/xmon: Fix opcode being uninitialized in print_insn_powerpc

On Mon, Feb 25, 2019 at 9:39 PM Nathan Chancellor
<[email protected]> 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 <[email protected]>

haha! (shows office mates). Nice find, and fix!
Reviewed-by: Nick Desaulniers <[email protected]>

> ---
> 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
>


--
Thanks,
~Nick Desaulniers

2019-02-28 09:23:41

by Michael Ellerman

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 <[email protected]>
> Reviewed-by: Nick Desaulniers <[email protected]>

Applied to powerpc next, thanks.

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

cheers