[16.0.X] Backport root: Segmentation violation in the TTree::Merge method

[akritkbehera]

Updating Root as discussed in #10263 (comment)

backport of #10263

[cmsbuild]

A new Pull Request was created by @akritkbehera for branch IB/CMSSW_16_0_X/master.

@akritkbehera, @cmsbuild, @iarspider, @raoatifshad, @smuzaffar can you please review it and eventually sign? Thanks.
@ftenchini, @mandrenguyen, @sextonkennedy you are the release manager for this.
cms-bot commands are listed here

[cmsbuild]

cms-bot internal usage

[akritkbehera]

Please test

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-a04fc6/50436/summary.html
COMMIT: cc55f3f
CMSSW: CMSSW_16_0_X_2026-01-05-1100/el8_amd64_gcc13
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week1/cms-sw/cmsdist/10264/50436/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

Summary:

• You potentially added 13 lines to the logs
• ROOTFileChecks: Some differences in event products or their sizes found
• Reco comparison results: 8 differences found in the comparisons
• Reco comparison had 4 failed jobs
• DQMHistoTests: Total files compared: 53
• DQMHistoTests: Total histograms compared: 4280553
• DQMHistoTests: Total failures: 3
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 4280530
• DQMHistoTests: Total skipped: 20
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 52 files compared)
• Checked 227 log files, 198 edm output root files, 53 DQM output files
• TriggerResults: no differences found

[smuzaffar]

+externals

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next IB/CMSSW_16_0_X/master IBs (tests are also fine). This pull request will now be reviewed by the release team before it's merged. @mandrenguyen, @ftenchini, @sextonkennedy (and backports should be raised in the release meeting by the corresponding L2)

[smuzaffar]

@cms-sw/orp-l2 , this is backport of latest root 6.36 changes which contain fix for Segmentation violation in the TTree::Merge method ( root-project/root#20706 )

Feel free to include it for next 16.0.X IBs and next CMSSW_16_0 release