[PATCH] jffs, clang: avoid some warnings of used uninitialized ptr

[Sebastian Huber]

On 05/10/2018 12:44, Daniel Hellstrom wrote:
>
> On 2018-10-05 09:41, Sebastian Huber wrote:
>> On 05/10/2018 09:38, Daniel Hellstrom wrote:
>>>
>>> On 2018-10-05 09:34, Sebastian Huber wrote:
>>>> On 05/10/2018 09:25, Daniel Hellstrom wrote:
>>>>> On 2018-10-05 09:12, Sebastian Huber wrote:
>>>>>> On 05/10/2018 08:57, Daniel Hellstrom wrote:
>>>>>>> This fixes the following test failures on LEON3 UP/SMP when
>>>>>>> built using clang compiler:
>>>>>>>   * fsjffs2gc01
>>>>>>>   * jffs2_fserror
>>>>>>>   * jffs2_fspermission
>>>>>>>   * jffs2_fsrdwr
>>>>>>>   * jffs2_fstime
>>>>>>
>>>>>> The problem is probably in the 
>>>>>> rbtree_postorder_for_each_entry_safe(). Coverity Scan has also an 
>>>>>> issue with this macro. It is on my todo list. Please do not check 
>>>>>> in this patch.
>>>>> Ok I will not push it. Yes I was also thinking so. To use 
>>>>> offsetof() macro could be an option maybe, however the node type 
>>>>> input is not known to the rbtree_postorder_for_each_entry_safe() 
>>>>> function even though it only used from jffs2 code. 
>>>>
>>>> The Linux code uses typeof. We could do this also:
>>>>
>>>> diff --git a/cpukit/include/linux/rbtree.h 
>>>> b/cpukit/include/linux/rbtree.h
>>>> index 53c777e8c1..8fc575240f 100644
>>>> --- a/cpukit/include/linux/rbtree.h
>>>> +++ b/cpukit/include/linux/rbtree.h
>>>> @@ -126,12 +126,12 @@ static inline struct rb_node *rb_parent( 
>>>> struct rb_node *node )
>>>>    for ( \
>>>>      node = _RBTree_Postorder_first( \
>>>>        (RBTree_Control *) root, \
>>>> -      (size_t) ( (char *) &node->field - (char *) node ) \
>>>> +      offsetof( __typeof__( *node ), field ) \
>>>>      ); \
>>>>      node != NULL && ( \
>>>>        next = _RBTree_Postorder_next( \
>>>>          &node->field, \
>>>> -        (size_t) ( (char *) &node->field - (char *) node ) \
>>>> +        offsetof( __typeof__( *node ), field ) \
>>>>        ), \
>>>>        node != NULL \
>>>>      ); \
>>>>
>>>> It shouldn't be a big problem since at least GCC and clang supports 
>>>> it. It is also a standard C++ operator. It is already used in
>>>>
>>>> cpukit/libfs/src/jffs2/include/linux/list.h
>>>
>>> Ok, I will give it a try.
>>>
>>
>> Thanks, please try this patch:
>>
>> https://lists.rtems.org/pipermail/devel/2018-October/023181.html
>
> Yes I can confirm it fixed all the 5 tests on gr712rc with clang. It 
> also removed the two warnings in jffs2 code related.
>
> I have updated my patch to only include the third warning fix then:
>
> ---
>  cpukit/libfs/src/jffs2/src/readinode.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/cpukit/libfs/src/jffs2/src/readinode.c 
> b/cpukit/libfs/src/jffs2/src/readinode.c
> index 519b0d6..ecdf335 100644
> --- a/cpukit/libfs/src/jffs2/src/readinode.c
> +++ b/cpukit/libfs/src/jffs2/src/readinode.c
> @@ -35,7 +35,7 @@ static int check_node_data(struct jffs2_sb_info *c, 
> struct jffs2_tmp_dnode_info
>      struct jffs2_raw_node_ref *ref = tn->fn->raw;
>      int err = 0, pointed = 0;
>      struct jffs2_eraseblock *jeb;
> -    unsigned char *buffer;
> +    unsigned char *buffer = NULL;
>      uint32_t crc, ofs, len;
>      size_t retlen; 

What is this for a warning? Some sort of uninitialized variable warning? 
This code is identical to the Linux upstream. This is probably a clang bug.

-- 
Sebastian Huber, embedded brains GmbH

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