[U-Boot] [PATCH] arm, ubifs: fix gcc5.x compiler warning

[Heiko Schocher <hs@denx.de>]

Hello Jeroen,

Am 30.11.2015 um 10:20 schrieb Jeroen Hofstee:
> Hello Heiko,
>
> On 30-11-15 08:47, Heiko Schocher wrote:
>> compiling U-Boot for openrd_base_defconfig with
>> gcc 5.x shows the following warning:
>>
>>    CC      fs/ubifs/super.o
>> In file included from fs/ubifs/ubifs.h:35:0,
>>                   from fs/ubifs/super.c:37:
>> fs/ubifs/super.c: In function 'atomic_inc':
>> ./arch/arm/include/asm/atomic.h:55:2: warning: 'flags' is used uninitialized in this function
>> [-Wuninitialized]
>>    local_irq_save(flags);
>>    ^
>> fs/ubifs/super.c: In function 'atomic_dec':
>> ./arch/arm/include/asm/atomic.h:64:2: warning: 'flags' is used uninitialized in this function
>> [-Wuninitialized]
>>    local_irq_save(flags);
>>    ^
>>    CC      fs/ubifs/sb.o
>> [...]
>>    CC      fs/ubifs/lpt.o
>> In file included from include/linux/bitops.h:123:0,
>>                   from include/common.h:20,
>>                   from include/ubi_uboot.h:17,
>>                   from fs/ubifs/ubifs.h:37,
>>                   from fs/ubifs/lpt.c:35:
>> fs/ubifs/lpt.c: In function 'test_and_set_bit':
>> ./arch/arm/include/asm/bitops.h:57:2: warning: 'flags' is used uninitialized in this function
>> [-Wuninitialized]
>>    local_irq_save(flags);
>>    ^
>>    CC      fs/ubifs/lpt_commit.o
>> In file included from include/linux/bitops.h:123:0,
>>                   from include/common.h:20,
>>                   from include/ubi_uboot.h:17,
>>                   from fs/ubifs/ubifs.h:37,
>>                   from fs/ubifs/lpt_commit.c:26:
>> fs/ubifs/lpt_commit.c: In function 'test_and_set_bit':
>> ./arch/arm/include/asm/bitops.h:57:2: warning: 'flags' is used uninitialized in this function
>> [-Wuninitialized]
>>    local_irq_save(flags);
>>    ^
>>    CC      fs/ubifs/scan.o
>>    CC      fs/ubifs/lprops.o
>>    CC      fs/ubifs/tnc.o
>> In file included from include/linux/bitops.h:123:0,
>>                   from include/common.h:20,
>>                   from include/ubi_uboot.h:17,
>>                   from fs/ubifs/ubifs.h:37,
>>                   from fs/ubifs/tnc.c:30:
>> fs/ubifs/tnc.c: In function 'test_and_set_bit':
>> ./arch/arm/include/asm/bitops.h:57:2: warning: 'flags' is used uninitialized in this function
>> [-Wuninitialized]
>>    local_irq_save(flags);
>>    ^
>>    CC      fs/ubifs/tnc_misc.o
>>
>> Fix it.
>>
>> Signed-off-by: Heiko Schocher <hs@denx.de>
>> ---
>>
>>   arch/arm/include/asm/atomic.h | 14 +++++++-------
>>   arch/arm/include/asm/bitops.h |  4 ++--
>>   2 files changed, 9 insertions(+), 9 deletions(-)
>>
>> diff --git a/arch/arm/include/asm/atomic.h b/arch/arm/include/asm/atomic.h
>> index 34c07fe..9b79506 100644
>> --- a/arch/arm/include/asm/atomic.h
>> +++ b/arch/arm/include/asm/atomic.h
>> @@ -32,7 +32,7 @@ typedef struct { volatile int counter; } atomic_t;
>>   static inline void atomic_add(int i, volatile atomic_t *v)
>>   {
>> -    unsigned long flags;
>> +    unsigned long flags = 0;
>>       local_irq_save(flags);
>>       v->counter += i;
>> @@ -41,7 +41,7 @@ static inline void atomic_add(int i, volatile atomic_t *v)
>
> Since flags is an "out" argument, something else must be wrong.
> There should be no need to initialize it, since local_irq_save should
> do that afaik.

yes, you are right, it should be, but gcc 5.x seems to have problems
with it ... compiled code size for the openrd_base config is same with
my patch ...

Hmm... for the openrd_base compile local_irq_save() is used from:
arch/arm/thumb1/include/asm/proc-armv/system.h

with:
static inline void local_irq_save(
         unsigned long flags __attribute__((unused)))
{
         __asm__ __volatile__ ("" : : : "memory");
}

flasg marked as unused ... seems correct to me, but I have
no idea, why gcc 5.x prints a warning ... any ideas?

bye,
Heiko
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