[PATCH] PCI: rpaphp: Avoid a sometimes-uninitialized warning
Christophe Leroy
christophe.leroy at c-s.fr
Tue Jun 4 16:24:39 AEST 2019
Quoting Nathan Chancellor <natechancellor at gmail.com>:
> 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
>
> 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.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/504
> Fixes: 2fcf3ae508c2 ("hotplug/drc-info: Add code to search
> ibm,drc-info property")
> Signed-off-by: Nathan Chancellor <natechancellor at gmail.com>
> ---
> drivers/pci/hotplug/rpaphp_core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/hotplug/rpaphp_core.c
> b/drivers/pci/hotplug/rpaphp_core.c
> index bcd5d357ca23..07b56bf2886f 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, fndit = 0;
Not sure fndit is needed at all. Looking into the full function code,
fndit only serves as doing a single action. That action could be done
in the loop directly, see below
And while you are at it, I guess you should also handle the
initialisation of cell_drc_name.
In the current code, it looks like content of cell_drc_name is
undefined when doing the strcmp when fndit is not 1.
>
> info = of_find_property(dn->parent, "ibm,drc-info", NULL);
> if (info == NULL)
> --
> 2.22.0.rc2
diff --git a/drivers/pci/hotplug/rpaphp_core.c
b/drivers/pci/hotplug/rpaphp_core.c
index bcd5d357ca23..87113419a44f 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)
@@ -248,14 +248,10 @@ static int rpaphp_check_drc_props_v2(struct
device_node *dn, char *drc_name,
if (my_index > drc.last_drc_index)
continue;
- fndit = 1;
+ /* Found it */
+ 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))) &&
Christophe
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