[cfe-dev] [RFC][PATCH] Static analyser warning about identical inner condition

[Gábor Horváth]

Hi!

Just a minor note: it might give false positives in case there is a side
effect in the condition that is repeated.

Wouldn't it be better to catch these kind of bugs using the constraint
manager and checking for always true conditions?

Best Regards,
Gábor Horváth

On 8 May 2015 at 10:46, Daniel Marjamäki <Daniel.Marjamaki at evidente.se>
wrote:

>
>
> Hello!
>
> This is just a request for comments.
>
> The patch I attach improves the identicalexpr checker in the static
> analyser. It adds a warning when there is an identical inner condition
> inside a if.
>
> Example code taken from a debian project:
>
>         if(revint)
>         {
>             if(revint)
>
> Testing:
> I scanned 477 debian projects with this checker and got 2 warnings. Both
> are bugs as far as I see. Also, in both these cases the inner conditions
> does not have an 'else' so there is no unreachable code.
>
> I think it would be a good idea to add a heuristic to avoid warnings when
> there is hidden code. For example:
>
>     if (x)
>     {
> #if SOME_FALSE_CONDITION
>         x = dostuff();
> #endif
>         if (x)
>
> But other than that... this checker seems to be reliable imho.
>
>
> A possible further improvement would be to warn also warn if the inner
> condition "overlaps". For instance:
>
>     if (x == 15)
>     {
>         if (x > 0)
>         ...
>
> Any opinions / ideas?
>
> Best regards,
> Daniel Marjamäki
>
>
> ..................................................................................................................
> Daniel Marjamäki Senior Engineer
> Evidente ES East AB  Warfvinges väg 34  SE-112 51 Stockholm  Sweden
>
> Mobile:                 +46 (0)709 12 42 62
> E-mail:                 Daniel.Marjamaki at evidente.se
>
> www.evidente.se
>
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>
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