Coverage calculation for C++ and Rust

[PiotrKorkus]

Currently issues with coverage calculation are observed across different Modules. We need a common solution that can be applied and used in reference_integration.

Problem definition

Mutual

• we need solution that is common and can be reused by everyone
• we need justifications when coverage != 100%, we need mechanisms to justify etc.
• tooling should support platform variants, allows justifications only for specific one, etc.
• tooling should allow easy use to developers and clear information where improvements are needed
• tooling will require certification but there is no other known alternative that will fulfill all our requirements
• tool requirements initially defined in use llvm cov for coverage and justification communication#549

C++

• different frameworks have different statements definition - we need that aligned in SCORE
• bazel coverage is not 100% reliable
• PR with suggested changes as reference use llvm cov for coverage and justification communication#549
• No other alternatives exist for our knowledge right now

Rust

• currently only line coverage is calculated
• ferrocene toolchain supports only Linux (QNX UTs don't work)
• there was a new PR in toolchains to support coverage in QNX @PiotrKorkus to check if that works
  feat: add coverage support to QNX toolchain bazel_cpp_toolchains#62
• other coverages where quoted to ferrocene. Branch coverage would be possible to get with other open-source solutions

It should be possible to use a common tool for generating coverage for both languages.

Next steps

• Get QNX coverage working for C++
• Look into Rust coverage
• Rust and C++ report should have a combined report

[PiotrKorkus]

Hello @antonkri @FScholPer @LittleHuba @4og @pawelrutkaq @nradakovic,
as discussed today in the meeting lets track coverage topic in this issue.

Please update problem definition according to your knowledge, so we can have a breakout session next week and discuss.

[PiotrKorkus]

Metting to be held 18.06 13:00 CET

https://teams.microsoft.com/l/meetup-join/19%3ameeting_OTAxODU4YjMtZWViZi00YjAwLWFjMTctZTI5MmNmNjdmNjg4%40thread.v2/0?context=%7b%22Tid%22%3a%22ab1be58c-0a5a-47f0-8b55-1c095dbd46f5%22%2c%22Oid%22%3a%22afbfab40-763f-4c44-b67c-532be43b15df%22%7d

[PiotrKorkus]

Participants of todays meeting:
@antonkri
@LittleHuba
@4og
@pawelrutkaq
@PiotrKorkus

Issue description was updated during the meeting with discussion points.

[AlexanderLanin]

See also comments from @uwe-martin at https://github.com/orgs/eclipse-score/discussions/236#discussioncomment-17392374 and his attachment https://github.com/user-attachments/files/29213866/20260622.Coverage.issue.pdf

[pahmann]

@OliverHeilwagen and @NicolasFussberger would you kindly take look at it and leave some comments. Do you like it? Is it feasible?

[4og]

I left a reply on @uwe-martin's comment https://github.com/orgs/eclipse-score/discussions/236#discussioncomment-17524343

There is also a long discussion thread in eclipse-score/score_cpp_policies#9