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Date:   Mon, 3 Jun 2019 14:51:36 -0700
From:   Nathan Chancellor <natechancellor@gmail.com>
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     Tyrel Datwyler <tyreld@linux.ibm.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Bjorn Helgaas <bhelgaas@google.com>, linux-pci@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, LKML <linux-kernel@vger.kernel.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH] PCI: rpaphp: Avoid a sometimes-uninitialized warning
Message-ID: <20190603215136.GA45181@archlinux-epyc>
References: <20190603174323.48251-1-natechancellor@gmail.com>
 <CAKwvOdkQzdZezwf51UddFVGQh0mRFMEexr1cMHx=va88T515YQ@mail.gmail.com>
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Hi Nick,

On Mon, Jun 03, 2019 at 02:07:50PM -0700, Nick Desaulniers wrote:
> On Mon, Jun 3, 2019 at 10:44 AM Nathan Chancellor
> <natechancellor@gmail.com> wrote:
> > Looking at the loop in a vacuum as clang would, fndit could be
> > uninitialized if entries was ever zero or the if statement was
> > always true within the loop. Regardless of whether or not this
> > warning is a problem in practice, "found" variables should always
> > be initialized to false so that there is no possibility of
> > undefined behavior.
> 
> Thanks for the patch Nathan.  fndit isn't really being used for
> anything other than a print statement outside of the loop.  How about:

Thank you for the review, this seems reasonable. I will send a v2
shortly.

> 
> ```
> diff --git a/drivers/pci/hotplug/rpaphp_core.c
> b/drivers/pci/hotplug/rpaphp_core.c
> index bcd5d357ca23..c3899ee1db99 100644
> --- a/drivers/pci/hotplug/rpaphp_core.c
> +++ b/drivers/pci/hotplug/rpaphp_core.c
> @@ -230,7 +230,7 @@ static int rpaphp_check_drc_props_v2(struct
> device_node *dn, char *drc_name,
>   struct of_drc_info drc;
>   const __be32 *value;
>   char cell_drc_name[MAX_DRC_NAME_LEN];
> - int j, fndit;
> + int j;
> 
>   info = of_find_property(dn->parent, "ibm,drc-info", NULL);
>   if (info == NULL)
> @@ -245,17 +245,13 @@ static int rpaphp_check_drc_props_v2(struct
> device_node *dn, char *drc_name,
> 
>   /* Should now know end of current entry */
> 
> - if (my_index > drc.last_drc_index)
> - continue;
> -
> - fndit = 1;
> - break;
> + /* Found it */
> + if (my_index <= drc.last_drc_index) {
> + sprintf(cell_drc_name, "%s%d", drc.drc_name_prefix,
> + my_index);
> + break;
> + }
>   }
> - /* Found it */
> -
> - if (fndit)
> - sprintf(cell_drc_name, "%s%d", drc.drc_name_prefix,
> - my_index);
> 
>   if (((drc_name == NULL) ||
>        (drc_name && !strcmp(drc_name, cell_drc_name))) &&
> ```
> (not sure my tabs were pasted properly in the above...)

Doesn't look like it but no worries.

Thanks,
Nathan