[cfe-dev] Clang Static Analyzer without scan-build

Wed Jul 31 16:53:08 PDT 2013

On Jul 31, 2013, at 4:39 PM, Aditya Kumar <hiraditya at codeaurora.org> wrote:

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> From: Anna Zaks [mailto:ganna at apple.com] 
> Sent: Wednesday, July 31, 2013 5:05 PM
> To: Aditya Kumar
> Cc: Manuel Klimek; clang-dev Developers; Michele Galante
> Subject: Re: [cfe-dev] Clang Static Analyzer without scan-build
>  
>  
> On Jul 31, 2013, at 2:53 PM, Aditya Kumar <hiraditya at codeaurora.org> wrote:
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> From: Anna Zaks [mailto:ganna at apple.com] 
> Sent: Wednesday, July 31, 2013 3:50 PM
> To: Aditya Kumar
> Cc: Manuel Klimek; clang-dev Developers; Michele Galante
> Subject: Re: [cfe-dev] Clang Static Analyzer without scan-build
>  
>  
> On Jul 31, 2013, at 12:13 PM, Aditya Kumar <hiraditya at codeaurora.org> wrote:
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> I have a preliminary working version of my patch and I ran it through our test framework (>100 MLOC), and it has worked fine.
> To generate the summarized report (index.html) I copied some portions of scan-build and generated the summary.
> I’m planning to write some post-processing program that parses the report-*.html files and stores them in a database.
> Will that be useful?
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> This depends on the workflow you have in mind. What reports the database will contain: ex, the results of the latest build or results of every build... 
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> I think the database might have limited usefulness if you are doing partial builds, at least you don't really know which set of bugs you are looking at.
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> A useful workflow includes running the analyzer as part of continuous integration and storing results of every build. In that scenario, it is useful to only show / highlight the diff of issues or only new issues that the analyzer produces on the latest build. We do not have a very good infrastructure for this, but the first step would be to look at utils/analyzer/CmpRuns.py script and see if it could be useful for you.
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> Thanks for telling me about utils/analyzer/CmpRuns.py.
> By the way, I am totally in favor of having a stand-alone tool like scan-build which makes it easy to run static analyzer separately as a part of
> nightly/weekly builds or by a group of people specially assigned to track down bugs in a software infrastructure. The idea of storing report-statistics in a database could be a useful addition to standalone tools.
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> I thought the main issue for you was that scan-build does not support your build system, so you would not be able to use it as is regardless.
> (I just want to reiterate that I think that improving scan-build/building a better version of it is the right approach as this is currently considered the gateway for all analyzer users.)
> 
> So there are two problems.
> 1.       One software infrastructure which has scons build-system cannot be analyzed with scan-build for now. This is in-fact a general problem with scan-build or any other static analysis enterprise tool that build-system integration is non-trivial. For that I have tried to implement --compile-and-analyze flag. Using this facility, I was able to run clang static analyzer on all programs/test-infrastructure available to us without having to worry about different kinds of build system. What I’m trying to say is we should also have facility to compile-and-analyze within the compiler as well. This will help developers track down potential bugs as quickly as possible. I do not want to touch scan-build because it is written in Perl. Initially I copied some portions of it to generate summarized report, but now I have a C++ implementation which parses all the report-*.html files and generates a summary. I can put my patch up for review if it can be helpful.

It would be great if we could keep just one static analyzer tool/entry point. If that means that scan-build should be rewritten, that's fine (it's actually one of the items on the todo list I've mentioned earlier). 

> 2.       In general I would like to improve/add support for single-entry-point-based static analysis tool. I thought that a facility to store reports at regular intervals (using some database etc.), will be a small (but useful) addition in this direction.

Yes, infrastructure for using the analyzer in a continuous integration setting would be a useful addition. 

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> Currently, what I have implemented is the following:
> 1.       compile the programs with a flag e.g., (clang++ --compile-and-analyze <path/to/report-dir> -c test.cpp). This stores all the report-*.html files in report-dir.
> Also, I have created a post-processing program which does the following:
> 1.       parse the report-*.html file and generate index.html. Ensure uniqueness of each report by comparing the sha1 keys (I’m using the linux system call to compute the sha1 keys for now).
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> Uniqueing reports using sha1 of the html file is not robust. Consider what happens when someone adds a line of code to the file containing the report somewhere before the report location.
> Yes, in that case the sha1 will change, but even scan-build follows the same approach. I’ll try to find an alternative solution. Thanks for pointing this out.
> 

Scan build does not do build results comparison. This is why I've suggested the CmpRuns.py script, which does provide a better alternative to what you are doing.

> 2.       populate the table in the database (mysql) with same details. To ensure uniqueness of details I store the sha1 key of report-*.html files along with the bug-details corresponding to each report.
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> Note, when running the analyzer as part of the compilation, one issue you'll have to worry about is the __clang_analyzer__ macro, which is only defined when you run the analyzer and not the compiler.
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> So the way I have defined the action-pipeline is:
> 0: input, "test.cpp", c++
> 1: analyzer, {0}, plist
> 2: input, "test.cpp", c++
> 3: preprocessor, {2}, c++-cpp-output
> 4: compiler, {3}, assembler
> 5: assembler, {4}, object
>   6: linker, {5}, image
> I think, this way the frontend should define the __clang_analyzer__ during analysis and not during the compilation.
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> You probably want to compile before the analysis. The analyzer generally assumes that it runs on code that compiles without errors. (This is also the workflow of scan-build.)
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> That seems to be a better idea. Thanks for the suggestion.
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> -Aditya
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> Anna.
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>  
> From: Manuel Klimek [mailto:klimek at google.com] 
> Sent: Wednesday, July 31, 2013 1:15 PM
> To: Anna Zaks
> Cc: Aditya Kumar; clang-dev Developers; Michele Galante
> Subject: Re: [cfe-dev] Clang Static Analyzer without scan-build
>  
> On Wed, Jul 31, 2013 at 8:07 PM, Anna Zaks <ganna at apple.com> wrote:
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> On Jul 30, 2013, at 2:37 PM, Aditya Kumar <hiraditya at codeaurora.org> wrote:
> 
> 
> 
> 
> I was looking at the same problem and planning to work on it.
> What I’m planning to do is having a compiler flag which enables a user to perform compilation as well as static analysis at the same time,
> and make relevant changes in the clang driver to build a set of ‘Actions’ in the pipeline such that static analysis and compilation takes place simultaneously.
> This will have an overhead on the overall compilation time which is often not the desirable thing. But there is an advantage that this flag can be incorporated in the build-system of software.
> Since the build systems are really good at tracking the files which have changed and compiling only the minimal set of required files,
> the overall turnaround time of static analysis will be very small and user can afford to run static analyzer with every build.
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> Have you looked at how scan-build currently works? It does compile and analyze the source files (clang is called twice). It is also driven by the build system, so we are not reanalyzing files that the build system would not recompile.
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> The main advantage of keeping the scan-build-like interface is that, in the future, we plan to extend the analyzer to perform cross-file(translation unit) analysis. This is why we encourage the use of a single entry point (scan-build) when analyzing a project.
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> Said that, the current implementation of scan-build is hacky and could be improved (see http://clang-analyzer.llvm.org/open_projects.html).
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> For what it's worth, I think the way to do large scale static analysis is to run over each TU in isolation, and output all the information needed to do the global analysis. Then, run the global analysis as a post-processing step, after sharding the information from that first step into parallelizable pieces.
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> Note that I'm not trying to contradict what you said :) Just wanted to throw in some experience. We are currently starting to run the analyzer on our internal code base (see Pavel's work) based on the Tooling/ stuff (clang-check has grown a --analyze flag) and would be very interested in having a system that allows full codebase analysis and still works on ~100MLOC codebases... ;)
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> Cheers,
> /Manuel
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> Cheers,
> Anna.
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> I wanted some feedback if this is a good idea or not.
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> -Aditya
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