Use of initialized variable in strtod.c

Joel Sherrill joel.sherrill@oarcorp.com
Wed Mar 15 20:03:00 GMT 2017



On 3/15/2017 2:54 PM, Joel Sherrill wrote:
>
>
> On 3/15/2017 2:31 PM, Jeffrey Walton wrote:
>>> Does Coverity have a way in which in the code it can be marked as OK?  (I'd
>>> expect some '#pragma CoverityIgnore(bits)' or the like ought to be
>>> available.)
>>
>> Yes. You have to provide a modeling file. Also see the Coverity Scan
>> FAQ entry "what is a model" at https://scan.coverity.com/faq.
>
> A model is for odd cases like where you have your
> own memory allocators or synchronization primitives.
>
> I think this is a case for what they call annotations.
> I have never written one of these but I think we would
> have to add a comment something like this ahead of the
> call:
>
> /* coverity[uninit_use_in_call] */

Adding this does result in silencing Coverity on this issue.
It doesn't change the fact that the uninitialized bits
variable is used on the RHS of ULtod() though. :(

> I will try adding that notation but we clearly need
> some guidelines as a project.
>
>> Other projects use them, like Python. See, for example,
>> https://docs.python.org/devguide/coverity.html.
>>
>>> I agree with trying to get rid of the message, but it is worth
>>> bloat to do it?  (It will add instructions to either initialize bits to 0 or
>>> add the else.)
>>
>> If I am parsing things correctly, it seems like the bloat is going the
>> other way: if the code is not needed, then remove it. It will avoid
>> findings like these, and speed up the compile.
>>
>>> I would rather mark something in the code as a false
>>> positive than add code because the tool is not smart enough to know--so we
>>> might differ in philosophy there.
>>
>> Perhaps a better strategy would be to initialize all variables, and
>> then allow the optimizer to remove the unneeded writes. It will ensure
>> a program is in a good state, and avoid findings like these.
>
> I'm a middle of the road guy. I add initialization in cases
> where there are paths where it is used and doesn't otherwise
> get set. I wouldn't automatically initialize everything.
>
> In this case, "bits" is actually used on the RHS multiple
> times in ULtod() so it bothers me that it has an undefined
> value. That means the output of ULtod() is undefined in
> this case.
>
>> Another strategy is to do nothing. In this case, the same findings
>> will waste multiple developer's time, and generate additional mailing
>> list messages.
>
> Agreed.
>
>> I like dark and silent cockpits, so I don't want tools generating
>> findings, and I don't want mailing list messages. I would squash it
>> once and for all and avoid all future problems. But that's just me,
>> and I understand the Newlib project may have a different outlook on
>> things.
>
> +1
>
> There are still 60 others issues. We should do our best to squash
> them permanently. IMO marking them with Coverity specific annotation
> just means that another static analyzer may find the same issue
> in the future. The annotation won't help.
>
>> Jeff
>>
> --joel
>



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