[cfe-dev] uninitialized variable warning, etc

[Chris Lattner]

On Mar 6, 2009, at 11:45 PM, रजनीश wrote:
> Here are some examples taken from ffmpeg-export-2008-12-18

These are all exactly the sorts of things that the warning was  
designed to catch.  Are spaces really that horrible to use? :)

-Chris


>
>
>
>        s->inter_quant_bias=-(1<<(QUANT_BIAS_SHIFT-2)); //(a - x/4)/x
>
>            for(change=-1; change<=1; change+=2){
>
>        next_dir=-1;
>
>        for(mv=-(16<<f_code); mv<(16<<f_code); mv++){
>
>    c=d=e=-1;
>
>            pred_table[0]=-2;
>
>                lpc[i][j]=-m[(pass-1)&1].coeff[i][j];
>
>
> On Mar 6, 2009, at 11:14 PM, Chris Lattner wrote:
>
>>
>> On Mar 6, 2009, at 2:11 PM, Eli Friedman wrote:
>>
>>> On Thu, Mar 5, 2009 at 6:36 PM,  <rdogra at earthlink.net> wrote:
>>>> test.c: In function ‘main’:
>>>> test.c:8: warning: format ‘%s’ expects type ‘char *’, but  
>>>> argument 2
>>>
>>> There's a TODO in the code to add this check.
>>>
>>>> has type ‘int’
>>>> test.c:7: warning: ‘b’ is used uninitialized in this function
>>>
>>> clang doesn't have a warning like this as part of the default
>>> compilation process, at least for the moment.  There is a separate
>>> analysis module which prints warnings like this, though; see
>>> http://clang.llvm.org/StaticAnalysis.html.
>>
>> Right, note that GCC only produces "dataflow warnings" when  
>> optimizations are enabled though.
>>
>>>> libavcodec/dsputil.c:3966:10: warning: use of unary operator that  
>>>> may
>>>> be intended as compound assignment (-=)
>>>
>>> This warning triggers on a lot of stuff... we should probably  
>>> disable
>>> it by default.
>>
>> What sorts of cases does it trigger on that are false positives?
>>
>> -Chris
>