[cfe-dev] Cross Translational Unit Analysis in Clang Static Analyzer

Fri Mar 31 09:13:38 PDT 2017

Hi Aleksei,

your review would be very highly appreciated in any pace and form. ☺

Thanks,
Daniel

From: Aleksei Sidorin [mailto:a.sidorin at samsung.com]
Sent: 2017. március 31. 18:03
To: Dániel Krupp <daniel.krupp at ericsson.com>; cfe-dev at lists.llvm.org
Subject: Re: [cfe-dev] Cross Translational Unit Analysis in Clang Static Analyzer

Hello Daniel & Gabor. Thank you very much for your work!

I saw the patch and found it mostly familiar for me. But, unfortunately, now I cannot find enough time to make its review (my solutions that were implemented 2 years ago need some revisiting too).

I can try to do this review incrementally, by small chunks, if you are OK with it. But it will still take time. Sorry for this inconvenience.

31.03.2017 18:28, Dániel Krupp via cfe-dev пишет:
Hi All,

at the EuroLLVM’17 conference we presented our results  about a new analysis mode in clang static analyzer: Cross Translational Unit analysis.
See patch https://reviews.llvm.org/D30691
which is based on the work of A. Sidorin et al. http://lists.llvm.org/pipermail/cfe-dev/2015-October/045730.html, but without function summaries and updated to the newest Clang.

The CTU mode allows the analyzer to “inline” function calls that are defined in another TU than the one currently analyzed.
So it allows to find bugs that span multiple source files.
Without this patch the static analyzer engine, when meets an external function call,
cannot reason about the return value of a function (unknown) and the pointed values, references passed to a function as parameter are invalidated.

You can find a full patched clang 4.0 (use it with llvm commit 01609a325b5f85d88e3ab5c7d470409092436cb2 )
https://github.com/dkrupp/clang/tree/ctu-master

We have run the analysis on some reasonably-sized  (ffmpeg, curl, vim, openssl, postgresql) open source C projects and found many additional true positive reports compared to the traditional single TU mode in all projects.
This indicates that this feature would give many new results on any project.

We measured the heap usage, the analysis time and the number of new findings.
You can find the detailed comparison results here:
http://cc.elte.hu/clang-ctu/
In summary, the number of reported bugs is ~1.5-5x times the original single TU analysis, at the cost of 1.5-5x higher analysis time, 1.5-5x max heap usage (roughly in proportion to the increase in the number of reported faults).

The design concept is described shortly in this document: http://cc.elte.hu/clang-ctu/eurollvm17/abstract.pdf

If you would like to try this analysis mode on your project please find the description of the 2 new additional analyzer scripts here:
https://github.com/dkrupp/clang/blob/ctu-master/tools/xtu-build-new/readme.md

Would be  happy to hear your opinion and experiences with this feature and would appreciate your help in reviewing the patch.

Thanks & Regards,
Daniel

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--

Best regards,

Aleksei Sidorin,

SRR, Samsung Electronics
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