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From: Nick Desaulniers <ndesaulniers@google.com>
To: Nathan Chancellor <natechancellor@gmail.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
Date: Mon, 3 Jun 2019 14:07:50 -0700	[thread overview]
Message-ID: <CAKwvOdkQzdZezwf51UddFVGQh0mRFMEexr1cMHx=va88T515YQ@mail.gmail.com> (raw)
In-Reply-To: <20190603174323.48251-1-natechancellor@gmail.com>

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:

```
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

  reply	other threads:[~2019-06-03 21:59 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-03 17:43 [PATCH] PCI: rpaphp: Avoid a sometimes-uninitialized warning Nathan Chancellor
2019-06-03 21:07 ` Nick Desaulniers [this message]
2019-06-03 21:51   ` Nathan Chancellor
2019-06-03 22:11 ` [PATCH v2] " Nathan Chancellor
2019-06-04  0:03   ` Tyrel Datwyler
2019-06-27 19:18   ` Nathan Chancellor
2019-06-28  2:57   ` Joel Savitz
2019-07-22  2:43   ` Nathan Chancellor
2019-07-22  4:05     ` Michael Ellerman
2019-08-02  0:11       ` Bjorn Helgaas
2019-08-02 12:24         ` Michael Ellerman
2019-08-10 10:20   ` Michael Ellerman
2019-06-04  6:24 ` [PATCH] " Christophe Leroy

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