[PATCH][RFC] lib: zstd: resolve maybe-uninitialized warning

[Ahmad Fatoum]

On 14.06.23 11:11, Yegor Yefremov wrote:
> Hi Ahmad,
> 
> On Wed, Jun 14, 2023 at 10:55 AM Ahmad Fatoum <a.fatoum at pengutronix.de> wrote:
>>
>> Hello Yegor,
>>
>> On 14.06.23 10:09, yegorslists at googlemail.com wrote:
>>> From: Yegor Yefremov <yegorslists at googlemail.com>
>>>
>>> Perform memset() at the very beginning of the ZSTD_getFrameParams()
>>> routine.
>>
>> I saw this too a while back and I came to the conclusion that this
>> is a false positive. I wasn't able to reproduce this with
>> GCC 12, but saw it with GCC 11 IIRC.
> 
> You're right. I could reproduce it with GCC 10 but not 12. So, the
> patch can be dropped.

Kernel doesn't have this issue, because they did a wholesale sync
with upstream zstd a while back. We should be doing that for barebox
as well and extend zstd support to PBL and kernel images (currently
only available for ubifs and squashfs).

I attempted this last year:

  https://lore.barebox.org/barebox/20220713100922.1880282-1-a.fatoum@pengutronix.de/

But it had to be reverted because it caused regressions. Might be worth
giving it another shot and fix the issues with v1.

I don't know when I will get around to it, but if you are really
determined to fix the warning, this would be one way forward :-)

Thanks,
Ahmad

> 
> Yegor
> 
>> Cheers,
>> Ahmad
>>
>>>
>>> Signed-off-by: Yegor Yefremov <yegorslists at googlemail.com>
>>> ---
>>>  lib/zstd/decompress.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/lib/zstd/decompress.c b/lib/zstd/decompress.c
>>> index 19bf712881..78df7d660a 100644
>>> --- a/lib/zstd/decompress.c
>>> +++ b/lib/zstd/decompress.c
>>> @@ -207,6 +207,7 @@ static size_t ZSTD_frameHeaderSize(const void *src, size_t srcSize)
>>>  size_t ZSTD_getFrameParams(ZSTD_frameParams *fparamsPtr, const void *src, size_t srcSize)
>>>  {
>>>       const BYTE *ip = (const BYTE *)src;
>>> +     memset(fparamsPtr, 0, sizeof(*fparamsPtr));
>>>
>>>       if (srcSize < ZSTD_frameHeaderSize_prefix)
>>>               return ZSTD_frameHeaderSize_prefix;
>>> @@ -214,7 +215,6 @@ size_t ZSTD_getFrameParams(ZSTD_frameParams *fparamsPtr, const void *src, size_t
>>>               if ((ZSTD_readLE32(src) & 0xFFFFFFF0U) == ZSTD_MAGIC_SKIPPABLE_START) {
>>>                       if (srcSize < ZSTD_skippableHeaderSize)
>>>                               return ZSTD_skippableHeaderSize; /* magic number + skippable frame length */
>>> -                     memset(fparamsPtr, 0, sizeof(*fparamsPtr));
>>>                       fparamsPtr->frameContentSize = ZSTD_readLE32((const char *)src + 4);
>>>                       fparamsPtr->windowSize = 0; /* windowSize==0 means a frame is skippable */
>>>                       return 0;
>>
>> --
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>>
> 

-- 
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