[llvm-dev] [EXTERNAL] How to get branch coverage by using 'source-based code coverage'

[LoveZhi Xie via llvm-dev]

Hi, Alan

Really very excited to receive your email and sorry to be slow replying, it
has been exceptionally busy over the last few days ;(

Your explanation made the problem clear to me. So gcov branch coverage
should be called condition coverage and clang region coverage
is branch coverage in fact(also known as *decision/C1*), right?

And llvm/clang will support all the following coverage criteria in future

   - Line coverage
   - Function coverage
   - Branch coverage/region coverage
   - Condition coverage
   - Modified Condition/Decision Coverage

If there is any misunderstanding here, please point it out.

Thanks,
Ted Xie



Phipps, Alan <a-phipps at ti.com> 于2020年4月28日周二 下午10:14写道：

> Hi Ted,
>
>
>
> Presently, branch coverage is not supported in clang source-based code
> coverage, but I am working on implementing branch condition coverage right
> now.  It will track True/False branches for each leaf-level condition,
> including within Boolean expressions comprised of logical operators (“&&”,
> “||”).  Technically, this condition-based coverage is more granular than
> how “branch coverage” is often defined (tracking on that control flow
> decisions allow for all regions to be hit), and is closer to the
> granularity that GCOV provides, but it’s anchored to the source code, won’t
> count “hidden branches”, and isn’t negatively impacted by optimization
> (although the reverse isn’t true: coverage instrumentation may impact
> optimization).
>
>
>
> My work is a step closer to getting us toward Modified Condition/Decision
> Coverage (MC/DC).  I hope to upstream my work within the next few months,
> so unfortunately it won’t help you in the short-term.  Region coverage may
> be enough for what you need if you can ascertain based on the coverage that
> control-flow decisions have evaluated to both true and false, but I’ll let
> others comment here with suggestions.
>
>
>
> -Alan Phipps
>
>
>
> *From:* llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] *On Behalf Of *LoveZhi
> Xie via llvm-dev
> *Sent:* Sunday, April 26, 2020 11:36 AM
> *To:* llvm-dev at lists.llvm.org
> *Subject:* [EXTERNAL] [llvm-dev] How to get branch coverage by using
> 'source-based code coverage'
>
>
>
> Hi, llvm/clang experts
>
>
>
> I need to get the branch coverage for some testing code. But i found gcov
> can't give a expected coverage which may
>
> count some 'hidden branch' in (See stackoverflow answer
> <https://stackoverflow.com/questions/42003783/lcov-gcov-branch-coverage-with-c-producing-branches-all-over-the-place>).
> Instead, I turn to use clang and the 'source-based code coverage' feature
>
> may be a right choice. But i can't find anything to describe branch
> coverage explicitly on the official site
> <https://clang.llvm.org/docs/SourceBasedCodeCoverage.html>.
>
>
>
> So how to use clang to get branch coverage by utilizing 'source-based...'
> feature?  And is *region coverage *equivalent to branch coverage?
>
> (I tested on a simple program and region coverage seems pretty close to
> branch coverage)
>
>
>
> Any help is highly appreciated
>
>
>
> Thanks,
>
> Ted Xie
>
>
>
>
>
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