[Infrastructure] Use -gsplit-dwarf to improve linking

[ktf]

No description provided.

[github-actions]

O2 linter results: ❌ 0 errors, ⚠️ 0 warnings, 🔕 0 disabled

[ktf]

In my minimal test seems to speed up building by 15%.

[alibuild]

Error while checking build/O2Physics/o2 for 7147fe1 at 2026-02-17 12:53:

## sw/BUILD/O2Physics-latest/log
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
ninja: build stopped: subcommand failed.

Full log here.

[vkucera]

@ktf The option -gsplit-dwarf does not seem to take any arguments.

[ktf]

Indeed... It's only supported by Clang... :-/ We can have the version without the option, however it will mean that we have to do some extra juggling to get the debug symbols working.

[vkucera]

Indeed... It's only supported by Clang... :-/ We can have the version without the option, however it will mean that we have to do some extra juggling to get the debug symbols working.

Isn't it enough to just use the Clang version for macOS and the GCC version for Linux?

[ktf]

This is only for linux (Clang and Linux), on macOS the debug symbols are handled in a different way (via .dSYM) and this does not really apply.

The GCC version will need some extra juggling in any case to allow the debugger to find the debug symbols. The nice thing of =single, AFAICT, is that there is still only one file (hence the name). Still, the debug information is completely separate with such an option from the elf layout point of view and the linker does way less heavy lifting to merge multiple objects.

[alibuild]

Error while checking build/O2Physics/o2 for 5a0f145 at 2026-03-06 06:22:

[2882/2953] Linking CXX executable stage/bin/o2-analysistutorial-mm-my-example-task
[2883/2953] Building CXX object Tutorials/PWGLF/Strangeness/Derived/Analysis/CMakeFiles/O2Physicsexe-analysistutorial-lf-strangeness-derived-step2.dir/strangeness_derived_step2.cxx.o
[2884/2953] Building CXX object Tutorials/PWGCF/TwoParticleCorrelations/CMakeFiles/O2Physicsexe-analysis-cf-firstcfcorr.dir/src/firstcfcorrelations.cxx.o
[2885/2953] Linking CXX executable stage/bin/o2-analysistutorial-lf-strangeness-derived-step2
[2886/2953] Building CXX object Tutorials/PWGCF/EventPlane/src/CMakeFiles/O2Physicsexe-analysis-cf-spectator-plane-tutorial.dir/spectatorPlaneTutorial.cxx.o
[2887/2953] Linking CXX executable stage/bin/o2-analysis-cf-firstcfcorr
[2888/2953] Building CXX object Tutorials/PWGCF/FlowGenericFramework/src/CMakeFiles/O2Physicsexe-analysis-cf-flow-gfw-tutorial.dir/flowGFWTutorial.cxx.o
[2889/2953] Building CXX object Tutorials/PWGLF/Strangeness/Derived/Analysis/CMakeFiles/O2Physicsexe-analysistutorial-lf-strangeness-derived-step4.dir/strangeness_derived_step4.cxx.o
[2890/2953] Linking CXX executable stage/bin/o2-analysis-cf-spectator-plane-tutorial
[2891/2953] Building CXX object Tutorials/PWGLF/Strangeness/Original/CMakeFiles/O2Physicsexe-analysistutorial-lf-strangeness-step4.dir/strangeness_step4.cxx.o
[2892/2953] Linking CXX executable stage/bin/o2-analysis-cf-flow-gfw-tutorial
[2893/2953] Building CXX object Tutorials/PWGLF/Strangeness/Original/CMakeFiles/O2Physicsexe-analysistutorial-lf-strangeness-step3.dir/strangeness_step3.cxx.o
[2894/2953] Linking CXX executable stage/bin/o2-analysistutorial-lf-strangeness-derived-step4
[2895/2953] Linking CXX executable stage/bin/o2-analysistutorial-lf-strangeness-step4
[2896/2953] Linking CXX executable stage/bin/o2-analysistutorial-lf-strangeness-step3
[2897/2953] Building CXX object EventFiltering/CMakeFiles/O2Physicsexe-analysis-selected-bc-range-task.dir/selectBCRange.cxx.o
[2898/2953] Building CXX object Tutorials/PWGCF/FemtoFramework/CMakeFiles/O2Physicsexe-analysistutorial-cf-femtodream-tutorial-1.dir/src/CFTutorialTask1.cxx.o
[2899/2953] Building CXX object Tutorials/PWGHF/CMakeFiles/O2Physicsexe-analysistutorial-hf-skim-creator-mini.dir/skimCreatorMini.cxx.o
[2900/2953] Linking CXX executable stage/bin/o2-analysis-selected-bc-range-task
[2901/2953] Linking CXX executable stage/bin/o2-analysistutorial-cf-femtodream-tutorial-1
[2902/2953] Linking CXX executable stage/bin/o2-analysistutorial-hf-skim-creator-mini
[2903/2953] Building CXX object Tutorials/PWGCF/FemtoFramework/CMakeFiles/O2Physicsexe-analysistutorial-cf-femtodream-tutorial-3.dir/src/CFTutorialTask3.cxx.o
[2904/2953] Building CXX object Tutorials/PWGCF/FemtoFramework/CMakeFiles/O2Physicsexe-analysistutorial-cf-femtodream-tutorial-4.dir/src/CFTutorialTask4.cxx.o
[2905/2953] Linking CXX executable stage/bin/o2-analysistutorial-cf-femtodream-tutorial-3
[2906/2953] Building CXX object Tutorials/PWGCF/FemtoFramework/CMakeFiles/O2Physicsexe-analysistutorial-cf-femtodream-tutorial-2.dir/src/CFTutorialTask2.cxx.o
[2907/2953] Linking CXX executable stage/bin/o2-analysistutorial-cf-femtodream-tutorial-4
[2908/2953] Linking CXX executable stage/bin/o2-analysistutorial-cf-femtodream-tutorial-2
[2909/2953] Building CXX object Tutorials/PWGHF/CMakeFiles/O2Physicsexe-analysistutorial-hf-task-mini.dir/taskMini.cxx.o
[2910/2953] Building CXX object EventFiltering/CMakeFiles/O2Physicsexe-analysis-central-event-filter-task.dir/cefpTask.cxx.o
[2911/2953] Linking CXX executable stage/bin/o2-analysistutorial-hf-task-mini
[2912/2953] Linking CXX executable stage/bin/o2-analysis-central-event-filter-task
[WARN] Missing configuration json file: full_config.json
[INFO] NucleiFilters not present in the configuration, removing it.
[INFO] DiffractionFilters not present in the configuration, removing it.
[INFO] DqFilters not present in the configuration, removing it.
[INFO] HfFilters not present in the configuration, removing it.
[INFO] CFFilters not present in the configuration, removing it.
[INFO] JetFilters not present in the configuration, removing it.
[INFO] JetHFFilters not present in the configuration, removing it.
[INFO] FullJetFilters not present in the configuration, removing it.
[INFO] StrangenessFilters not present in the configuration, removing it.
[INFO] MultFilters not present in the configuration, removing it.
[INFO] PhotonFilters not present in the configuration, removing it.
[INFO] F1ProtonFilters not present in the configuration, removing it.
[INFO] DoublePhiFilters not present in the configuration, removing it.
[INFO] HeavyNeutralMesonFilters not present in the configuration, removing it.
[INFO] GlobalDimuonFilters not present in the configuration, removing it.
[INFO] H2fromLbFilters not present in the configuration, removing it.
[2913/2953] Building CXX object Tutorials/PWGCF/FemtoFramework/CMakeFiles/O2Physicsexe-analysistutorial-cf-femtodream-tutorial-5.dir/src/CFTutorialTask5.cxx.o
[2914/2953] Linking CXX executable stage/bin/o2-analysistutorial-cf-femtodream-tutorial-5

Full log here.