[cfe-dev] [GSoC] Interested in idea: "Find null smart pointer dereferences with the Static Analyzer"

[Nithin Vadukkumchery Rajendrakumar via cfe-dev]

Hi Artem,

Thank you very much for this detailed information and help.
I will checkout the existing checkers you mentioned and try to get a better
understanding of the problem.

----
Regards,
Nithin.VR


On Mon, Mar 9, 2020 at 2:30 AM Artem Dergachev <noqnoqneo at gmail.com> wrote:

> Hey!
>
> Welcome. Let's see.
>
> Nullability checker isn't the one that you're looking for. It's a
> different beast that governs hunt for null dereferences via so-called
> "nullability annotations". Like, a language extension is provided
> through which the programmer can tell the analyzer which variables /
> functions may or may not hold / produce null pointers, and the analyzer
> checks whether it makes sense how these nullable and non-null values
> propagate from one function to another. So it's the same problem but a
> different technique. It is targeted mostly at finding crashes in
> Objective-C apps that pass a lot of pointers around across many
> user-defined functions.
>
> The proposed GSoC project is of a different nature: we want to teach the
> static analyzer about a very specific C++ API, but we want to teach it
> much more thoroughly. It's not enough to know that
> std::unique_ptr::operator->() may occasionally return a null pointer;
> we'd much rather know when exactly does it return a null pointer (eg.,
> if the smart pointer is freshly default-constructed).
>
> If you want to study existing checkers, check out:
> - MoveChecker - the use-after-move checker which already finds *some*
> null smart pointer dereferences, given that they're guaranteed to be
> null after move.
> - SmartPtrChecker currently does almost nothing, but that's probably
> where you put your code into :)
> - IteratorChecker is a large ongoing pioneer project to find iterator
> and container related bugs such as dereferencing vector.end(). It's the
> closest thing to what you'll be implementing, but its handling of C++
> objects is outdated and overly complicated because some new facilities
> for C++ support (mostly the ones explained in the second half of
> https://www.youtube.com/watch?v=4n3l-ZcDJNY)  weren't in place yet when
> it all started.
>
> Once you understand the project a bit better and like it, the next step
> is to discuss here (in this mailing list) what is the best way to
> implement the checker. The ultimate outcome of this discussion will be a
> so-called "GSoC proposal". It's a few pages of text that you write, post
> here for more discussion, and eventually upload to the GSoC website.
> According to the GSoC timeline, the proposal should be submitted by the
> end of March. The proposal summarizes how *you* understand the project
> and how *you* plan to tackle it during the summer.
>
> Good luck on your GSoC path!
> Artem.
>
>
> On 3/7/20 3:40 PM, Nithin Vadukkumchery Rajendrakumar via cfe-dev wrote:
> >
> > Greetings,
> >
> >
> > I am interested to participate in GSoC 2020. I am particularly
> > interested in the project idea "Find null smart pointer dereferences
> > with the Static Analyzer". I am doing my masters in computer science
> > and interested in program analysis and verification. I thought
> > GSoC2020 will be a wonderful opportunity to learn more about Clang
> > Static Analyzer and contribute.
> >
> >
> > I have started reading about smart pointers in C++ to get a good grasp
> > of the concepts. Also, has some experience in implementing Clang
> > Static Analyzer simple checks(similar to SimpleStreamChecker) from the
> > tutorials. I read through few available tutorials and have some basic
> > idea about Control Flow Graph, Exploded Graph and Symbolic Values. I
> > have read the paper "A memory model for static analysis of C programs"
> > to get some theoretical background. I also started looking into
> > NullabilityChecker.cpp
> > <
> https://github.com/llvm/llvm-project/blob/master/clang/lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp> to
>
> > understand the codebase.
> >
> > I would like to know is this the right place to look?
> >
> > Could anyone please help me on what should I do next?
> >
> > ----
> > Thanks & Regards,
> > Nithin
> >
> > _______________________________________________
> > cfe-dev mailing list
> > cfe-dev at lists.llvm.org
> > https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>
>
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