MC/DC support for gcov?

[Martin Liška]

On 3/31/22 16:55, Sebastian Huber wrote:
> Hello,
> 
> gcov supports currently branch coverage. Some projects require modified condition/decision coverage (MC/DC):
> 
> https://en.wikipedia.org/wiki/Modified_condition/decision_coverage
> 
> In general, 100% branch coverage does not imply 100% MC/DC coverage:
> 
> https://www.adacore.com/uploads_gems/Couverture_ERTS-2012.pdf
> 
> The paper contains a criterion under which 100% branch coverage implies 100% MC/DC coverage:
> 
> "Theorem 1 If the BDD of a decision D is a tree (with
> only one path from the root to any condition node),
> then BDD edge coverage implies MCDC"
> 
> The BDD is the Binary Decision Diagram. I have no idea how the compiler and the coverage supports works in GCC. Is this BDD available for the coverage support and could the coverage support check for this property and then for example add it to the gcov information? If the BDD of a decision is not a tree, then we would have to record which paths through the BDD are covered to get the MC/DC coverage. This would require extra storage and instrumentation. According to the paper, the BDD is usually a tree in real world applications. Does this sound like feasible feature for GCC? Could it be even a GSoC project?
> 
> Kind regards,
>      Sebastian
> 

Hi.

There's a patch review for the feature:
https://gcc.gnu.org/pipermail/gcc-patches/2022-March/592065.html

Martin