PCM file not found while loading an ATLAS library

[krasznaa]

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Description

This is to keep track of this issue "over here" as well. As I promised @bellenot earlier today. 😉

The short version is that after we made one of our tracking libraries depend indirectly (well, it's not actually all that indirectly...) on ROOT (https://gitlab.cern.ch/atlas/athena/-/merge_requests/85842), we now see the following when loading our libActsGeometryLib.so library:

[bash][atspot01]:ATR-32387 > python -c "import ROOT; ROOT.gSystem.Load('libActsGeometryLib')"
Error in <TCling::LoadPCM>: ROOT PCM /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.36.04-6ef4f/x86_64-el9-gcc14-opt/lib/libMatrix_rdict.pcm file does not exist
Info in <TCling::LoadPCM>: In-memory ROOT PCM candidate /cvmfs/atlas-nightlies.cern.ch/repo/sw/main_Athena_x86_64-el9-gcc14-opt/sw/lcg/releases/ROOT/6.36.04-6ef4f/x86_64-el9-gcc14-opt/lib/libASImageGui_rdict.pcm

Info in <TCling::LoadPCM>: In-memory ROOT PCM candidate /cvmfs/atlas-nightlies.cern.ch/repo/sw/main_Athena_x86_64-el9-gcc14-opt/sw/lcg/releases/ROOT/6.36.04-6ef4f/x86_64-el9-gcc14-opt/lib/libASImage_rdict.pcm
...

The library in question seems to be built correctly as much as I can tell. 🤔 CMake directly links it against all the libraries that it needs, and my runtime environment finds all those libraries happily as well.

[bash][atspot01]:ATR-32387 > asetup Athena,main,latest
Using Athena/25.0.52 [cmake] with platform x86_64-el9-gcc14-opt
        at /cvmfs/atlas-nightlies.cern.ch/repo/sw/main_Athena_x86_64-el9-gcc14-opt/2026-02-08T2100
Unchanged: COOL_ORA_ENABLE_ADAPTIVE_OPT=Y
[bash][atspot01]:ATR-32387 > ldd -r /cvmfs/atlas-nightlies.cern.ch/repo/sw/main_Athena_x86_64-el9-gcc14-opt/2026-02-08T2100/Athena/25.0.52/InstallArea/x86_64-el9-gcc14-opt/lib/libActsGeometryLib.so
        linux-vdso.so.1 (0x00007fff4d6df000)
        libActsGeoUtils.so => /cvmfs/atlas-nightlies.cern.ch/repo/sw/main_Athena_x86_64-el9-gcc14-opt/2026-02-08T2100/Athena/25.0.52/InstallArea/x86_64-el9-gcc14-opt/lib/libActsGeoUtils.so (0x00007f565280e000)
        libActsPluginJson.so => /cvmfs/atlas-nightlies.cern.ch/repo/sw/main_Athena_x86_64-el9-gcc14-opt/2026-02-08T2100/AthenaExternals/25.0.52/InstallArea/x86_64-el9-gcc14-opt/lib/libActsPluginJson.so (0x00007f56526f3000)
...
        libbrotlicommon.so.1 => /lib64/libbrotlicommon.so.1 (0x00007f564adf6000)
        libcalg.so => /cvmfs/atlas-nightlies.cern.ch/repo/sw/main_Athena_x86_64-el9-gcc14-opt/2026-02-08T2100/Athena/25.0.52/InstallArea/x86_64-el9-gcc14-opt/lib/libcalg.so (0x00007f564adea000)
        libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f564adbd000)
        libcrypt.so.2 => /lib64/libcrypt.so.2 (0x00007f564ad83000)
        libpcre2-8.so.0 => /lib64/libpcre2-8.so.0 (0x00007f564ace7000)
[bash][atspot01]:ATR-32387 >

If I force-load libGeom.so first, then the error message goes away.

[bash][atspot01]:ATR-32387 > python -c "import ROOT; ROOT.gSystem.Load('libGeom'); ROOT.gSystem.Load('libActsGeometryLib')"
[bash][atspot01]:ATR-32387 >

Finally, I'll try to attach the output of import ROOT; ROOT.gDebug = 10; ROOT.gSystem.Load('libActsGeometryLib') as well, in case that helps. 🤔

Even more description of this issue (accessible to the ROOT developers hopefully) can be found here: https://its.cern.ch/jira/browse/ATEAM-1134

Reproducer

N/A

ROOT version

6.36/04 (LCG_108a_ATLAS_9)

Installation method

LCG

Operating system

EL9

Additional context

debug.log

[ferdymercury]

Maybe a bit related: #16601

Side note: run/install-paths were recently modified by @guitargeek and @hageboeck so maybe the issue is not there or different in newer ROOT versions.

[krasznaa]

Right... I should've checked this already. Indeed, the same code on top of the ROOT main branch is not producing this particular error.

[bash][atspot01]:ATR-32387 > asetup Athena,main--dev3LCG,latest
Using Athena/25.0.52 [cmake] with platform x86_64-el9-gcc15-opt
        at /cvmfs/atlas-nightlies.cern.ch/repo/sw/main--dev3LCG_Athena_x86_64-el9-gcc15-opt/2026-02-08T2100
Unchanged: COOL_ORA_ENABLE_ADAPTIVE_OPT=Y
[bash][atspot01]:ATR-32387 > root-config --version
6.39.01
[bash][atspot01]:ATR-32387 > python -c "import ROOT; ROOT.gSystem.Load('libActsGeometryLib')"
[bash][atspot01]:ATR-32387 >

I guess we'll need to check exactly when this "got fixed". And then see what we do with the LCG version used in our main nightly builds.

[dpiparo]

Thanks @krasznaa for preparing this detailed report. The file name libMatrix_rdict.pcm, as the error points out too, is related to a non-module build of ROOT, which should not be around since a long while in LCG stacks. Would you have an idea from where some kind of remnant of a non-modules build could come from in ATLAS environment?