ABI compatibility checker

[D4N]

This is a draft of a job on GitLab CI for the 0.27-maintenance branch that runs abi-compliance-checker to check the difference between the current state and the 0.27 tag. If there are notable differences, then the job fails. It furthermore uploads the report as an artifact for inspection.

Currently this doesn't work correctly yet, as the report doesn't contain any useful information at all. Maybe @cryptomilk can provide some insight to what I've missed?

[codecov]

Codecov Report

Merging #917 into 0.27-maintenance will decrease coverage by 0.41%.
The diff coverage is n/a.

@@                 Coverage Diff                  @@
##           0.27-maintenance     #917      +/-   ##
====================================================
- Coverage             63.36%   62.94%   -0.42%     
====================================================
  Files                   159      157       -2     
  Lines                 23046    21618    -1428     
====================================================
- Hits                  14603    13608     -995     
+ Misses                 8443     8010     -433

Impacted Files	Coverage Δ
include/exiv2/slice.hpp	47.5% <0%> (-44.66%)	⬇️
src/tags.cpp	56.68% <0%> (-22.43%)	⬇️
src/samsungmn_int.cpp	17.14% <0%> (-7.86%)	⬇️
src/olympusmn_int.cpp	19.23% <0%> (-6.81%)	⬇️
src/iptc.cpp	73.06% <0%> (-4.68%)	⬇️
src/image_int.cpp	40% <0%> (-4.24%)	⬇️
src/nikonmn_int.cpp	58.73% <0%> (-4.19%)	⬇️
src/crwimage_int.hpp	70% <0%> (-4.08%)	⬇️
samples/xmpsample.cpp	93.4% <0%> (-3.4%)	⬇️
unitTests/test_slice.cpp	96.92% <0%> (-3.08%)	⬇️
... and 95 more

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[piponazo]

That's a great addition to the project!

[piponazo]

Is it broken when consuming it from a system-package? from conan? both? Would you mind to create a ticket about this? I could check this issue.

[D4N]

It's broken when I checkout the tag directly, not from a system package and haven't tried conan.

[clanmills]

I agree with @piponazo This is a wonderful addition to the CI machinery. Let's enable it on 0.27-maintenance once v0.27.2 has been released and we'll aim to retain that API/ABI for the rest of "the dots".

At the moment, there are 4000 external symbols (from about 26000 in total). I suspect there is an architecture to drastically reduce the API and enable us to add/remove/deprecate interfaces. For example COM (yes, it's ancient Microsoft Technology) uses QueryInterface(UUID) to say "Do you have this Interface". Almost everything in the library could be hidden (from an external point of view).

Perhaps we could introduce a new architecture with v0.28 as the prototype v1.0 API. I wonder how other libraries deal with this?

Pull request has been modified.

[D4N]

Thanks to the amazing help provided by @lvc, I've been able to get this running on GitLab.

The solution to the problem was a bug in abi-dumper that caused issues with the pretty recent version of elfutils that is shipped by Fedora 30. I've worked around this issue by temporarily using the Fedora 29 container.

Let's see what the GitLab stage reports.

[D4N]

Nope, the issue is also present on Fedora 29, I'll have to update the package on Fedora and then this will start working (fingers crossed).

[D4N]

The abi compliance stage on GitLab succeded insofar as it now reports an error as 0.27 and 0.27-maintenance are not binary compatible.

So how should we approach this? Fix the ABI issues or just drop this?

[piponazo]

Great @D4N ! If the issue is easy to solve I would propose to fix it. We can create an issue about the specific issue, target it for the next dot release, and hopefully some of us could dedicate some time to it. If the issue is too complex to solve, then we can discuss more about what to do.