linux-kernel - Re: [PATCH v2] PCI: rpaphp: Avoid a sometimes-uninitialized warning

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Message-Id: <1561690674-5880-1-git-send-email-jsavitz@redhat.com>
Date:   Thu, 27 Jun 2019 22:57:54 -0400
From:   Joel Savitz <jsavitz@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Joel Savitz <jsavitz@...hat.com>,
        Tyrel Datwyler <tyreld@...ux.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, clang-built-linux@...glegroups.com,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH v2] PCI: rpaphp: Avoid a sometimes-uninitialized warning

>On Mon, Jun 03, 2019 at 03:11:58PM -0700, Nathan Chancellor wrote:
>> When building with -Wsometimes-uninitialized, clang warns:
>> 
>> drivers/pci/hotplug/rpaphp_core.c:243:14: warning: variable 'fndit' is
>> used uninitialized whenever 'for' loop exits because its condition is
>> false [-Wsometimes-uninitialized]
>>         for (j = 0; j < entries; j++) {
>>                     ^~~~~~~~~~~
>> drivers/pci/hotplug/rpaphp_core.c:256:6: note: uninitialized use occurs
>> here
>>         if (fndit)
>>             ^~~~~
>> drivers/pci/hotplug/rpaphp_core.c:243:14: note: remove the condition if
>> it is always true
>>         for (j = 0; j < entries; j++) {
>>                     ^~~~~~~~~~~
>> drivers/pci/hotplug/rpaphp_core.c:233:14: note: initialize the variable
>> 'fndit' to silence this warning
>>         int j, fndit;
>>                     ^
>>                      = 0
>> 
>> fndit is only used to gate a sprintf call, which can be moved into the
>> loop to simplify the code and eliminate the local variable, which will
>> fix this warning.
>> 
>> Link: https://github.com/ClangBuiltLinux/linux/issues/504
>> Fixes: 2fcf3ae508c2 ("hotplug/drc-info: Add code to search ibm,drc-info property")
>> Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
>> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
>> ---
>> 
>> v1 -> v2:
>> 
>> * Eliminate fndit altogether by shuffling the sprintf call into the for
>>   loop and changing the if conditional, as suggested by Nick.
> 
>>  drivers/pci/hotplug/rpaphp_core.c | 18 +++++++-----------
>>  1 file changed, 7 insertions(+), 11 deletions(-)

>> Gentle ping, can someone pick this up?

Looks a good simplification of somewhat convoluted control flow.

Acked-by: Joel Savitz <jsavitz@...hat.com>