| Message ID | 1366910944-3033663-16-git-send-email-arnd@arndb.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Arnd, On Thu, Apr 25, 2013 at 1:28 PM, Arnd Bergmann <arnd@arndb.de> wrote: > The newly rewritten get_property() function causes a bogus warning > from gcc-3.8, which cannot figure out that "level" is always > initialized at the point where it gets evaluated: > > drivers/thermal/cpu_cooling.c: In function 'get_property': > drivers/thermal/cpu_cooling.c:189:37: warning: 'level' may be used uninitialized in this function [-Wmaybe-uninitialized] > if (property == GET_FREQ && level == j) { > ^ > > Slightly rearranging the code makes this more obvious and > avoids the warning. > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > Cc: Zhang Rui <rui.zhang@intel.com> > Cc: Amit Daniel kachhap <amit.daniel@samsung.com> Rui has merged a patch that removes this bogus compiler warning: http://git.kernel.org/cgit/linux/kernel/git/rzhang/linux.git/commit/?h=next&id=4469b99743d296e24aefc5f8ed7df1bc9cfbbac8 Though, as not as elegant as your patch, it does the trick. :-) > --- > drivers/thermal/cpu_cooling.c | 17 +++++++++-------- > 1 file changed, 9 insertions(+), 8 deletions(-) > > diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c > index 768b508..34878e6 100644 > --- a/drivers/thermal/cpu_cooling.c > +++ b/drivers/thermal/cpu_cooling.c > @@ -165,10 +165,6 @@ static int get_property(unsigned int cpu, unsigned long input, > return 0; > } > > - if (property == GET_FREQ) > - level = descend ? input : (max_level - input -1); > - > - > for (i = 0, j = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) { > /* ignore invalid entry */ > if (table[i].frequency == CPUFREQ_ENTRY_INVALID) > @@ -186,10 +182,15 @@ static int get_property(unsigned int cpu, unsigned long input, > *output = descend ? j : (max_level - j - 1); > return 0; > } > - if (property == GET_FREQ && level == j) { > - /* get frequency by level */ > - *output = freq; > - return 0; > + > + if (property == GET_FREQ) { > + level = descend ? input : (max_level - input -1); > + > + if (level == j) { > + /* get frequency by level */ > + *output = freq; > + return 0; > + } > } > j++; > } > -- > 1.8.1.2 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
On Thursday 25 April 2013, edubezval@gmail.com wrote: > Rui has merged a patch that removes this bogus compiler warning: > http://git.kernel.org/cgit/linux/kernel/git/rzhang/linux.git/commit/?h=next&id=4469b99743d296e24aefc5f8ed7df1bc9cfbbac8 > > Though, as not as elegant as your patch, it does the trick. :-) Ok, works for me. Looking at the patch however tells me that it has the potential to hide real bugs if the code is ever changed to actually do an uninitialized access. It's not very likely in this case, but I generally recommend not to add any variables at declaration time unless the initialization is to a meaningful value that the code later uses. Arnd
On Thu, 2013-04-25 at 19:28 +0200, Arnd Bergmann wrote: > The newly rewritten get_property() function causes a bogus warning > from gcc-3.8, which cannot figure out that "level" is always > initialized at the point where it gets evaluated: > > drivers/thermal/cpu_cooling.c: In function 'get_property': > drivers/thermal/cpu_cooling.c:189:37: warning: 'level' may be used uninitialized in this function [-Wmaybe-uninitialized] > if (property == GET_FREQ && level == j) { > ^ > > Slightly rearranging the code makes this more obvious and > avoids the warning. > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > Cc: Zhang Rui <rui.zhang@intel.com> > Cc: Amit Daniel kachhap <amit.daniel@samsung.com> we already have a fix for this. please refer to https://patchwork.kernel.org/patch/2454891/ thanks for your patch, Arnd! -rui > --- > drivers/thermal/cpu_cooling.c | 17 +++++++++-------- > 1 file changed, 9 insertions(+), 8 deletions(-) > > diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c > index 768b508..34878e6 100644 > --- a/drivers/thermal/cpu_cooling.c > +++ b/drivers/thermal/cpu_cooling.c > @@ -165,10 +165,6 @@ static int get_property(unsigned int cpu, unsigned long input, > return 0; > } > > - if (property == GET_FREQ) > - level = descend ? input : (max_level - input -1); > - > - > for (i = 0, j = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) { > /* ignore invalid entry */ > if (table[i].frequency == CPUFREQ_ENTRY_INVALID) > @@ -186,10 +182,15 @@ static int get_property(unsigned int cpu, unsigned long input, > *output = descend ? j : (max_level - j - 1); > return 0; > } > - if (property == GET_FREQ && level == j) { > - /* get frequency by level */ > - *output = freq; > - return 0; > + > + if (property == GET_FREQ) { > + level = descend ? input : (max_level - input -1); > + > + if (level == j) { > + /* get frequency by level */ > + *output = freq; > + return 0; > + } > } > j++; > }
diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c index 768b508..34878e6 100644 --- a/drivers/thermal/cpu_cooling.c +++ b/drivers/thermal/cpu_cooling.c @@ -165,10 +165,6 @@ static int get_property(unsigned int cpu, unsigned long input, return 0; } - if (property == GET_FREQ) - level = descend ? input : (max_level - input -1); - - for (i = 0, j = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) { /* ignore invalid entry */ if (table[i].frequency == CPUFREQ_ENTRY_INVALID) @@ -186,10 +182,15 @@ static int get_property(unsigned int cpu, unsigned long input, *output = descend ? j : (max_level - j - 1); return 0; } - if (property == GET_FREQ && level == j) { - /* get frequency by level */ - *output = freq; - return 0; + + if (property == GET_FREQ) { + level = descend ? input : (max_level - input -1); + + if (level == j) { + /* get frequency by level */ + *output = freq; + return 0; + } } j++; }
The newly rewritten get_property() function causes a bogus warning from gcc-3.8, which cannot figure out that "level" is always initialized at the point where it gets evaluated: drivers/thermal/cpu_cooling.c: In function 'get_property': drivers/thermal/cpu_cooling.c:189:37: warning: 'level' may be used uninitialized in this function [-Wmaybe-uninitialized] if (property == GET_FREQ && level == j) { ^ Slightly rearranging the code makes this more obvious and avoids the warning. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Cc: Zhang Rui <rui.zhang@intel.com> Cc: Amit Daniel kachhap <amit.daniel@samsung.com> --- drivers/thermal/cpu_cooling.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-)