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

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Message-ID: <CAKwvOdkQzdZezwf51UddFVGQh0mRFMEexr1cMHx=va88T515YQ@mail.gmail.com>
Date:   Mon, 3 Jun 2019 14:07:50 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     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, LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH] PCI: rpaphp: Avoid a sometimes-uninitialized warning

On Mon, Jun 3, 2019 at 10:44 AM Nathan Chancellor
<natechancellor@...il.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:

```
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...)

-- 
Thanks,
~Nick Desaulniers