[RF] Crash doing HistFactory Workspace combination

[TomasDado]

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Description

We see a very weird crash related to combining workspaces that indiviallu are both valid and give sensible results. The crash seems to be related to some histograms missing/being nullpointers, see the stack trace:

[#2] PROGRESS:HistFactory -- 
-----------------------------------------
    Entering combination
-----------------------------------------


 *** Break *** segmentation violation



===========================================================
There was a crash.
This is the entire stack trace of all threads:
===========================================================
#0  __internal_syscall_cancel (a1=63588, a2=140730114203688, a3=0, a4=0, a5=0, a6=0, nr=61) at ./nptl/cancellation.c:40
#1  __syscall_cancel (a1=63588, a2=a2
entry=140730114203688, a3=a3
entry=0, a4=a4
entry=0, a5=a5
entry=0, a6=a6
entry=0, nr=61) at ./nptl/cancellation.c:75
#2  0x00007c07e671c98f in __GI___wait4 (pid=<optimized out>, stat_loc=stat_loc
entry=0x7ffe48776028, options=options
entry=0, usage=usage
entry=0x0) at ../sysdeps/unix/sysv/linux/wait4.c:30
#3  0x00007c07e671c9db in __GI___waitpid (pid=<optimized out>, stat_loc=stat_loc
entry=0x7ffe48776028, options=options
entry=0) at ./posix/waitpid.c:38
#4  0x00007c07e665c32d in do_system (line=<optimized out>) at ../sysdeps/posix/system.c:172
#5  0x00007c07e8126ce7 in TUnixSystem::Exec (this=0x5a2d403032f0, shellcmd=<optimized out>) at /home/tomas/ROOT_DEBUG/root_src/core/unix/src/TUnixSystem.cxx:2157
#6  TUnixSystem::StackTrace (this=0x5a2d403032f0) at /home/tomas/ROOT_DEBUG/root_src/core/unix/src/TUnixSystem.cxx:2448
#7  0x00007c07e8126668 in TUnixSystem::DispatchSignals (this=0x5a2d403032f0, sig=kSigSegmentationViolation) at /home/tomas/ROOT_DEBUG/root_src/core/unix/src/TUnixSystem.cxx:3668
#8  <signal handler called>
#9  0x00007c07e71bba94 in RooDataSet::loadValuesFromSlices (this=this
entry=0x7ffe4878b190, indexCat=..., slices=std::map with 8 elements = {...}, rangeName=rangeName
entry=0x0, cutVar=cutVar
entry=0x0, cutSpec=cutSpec
entry=0x0) at /home/tomas/ROOT_DEBUG/root_src/roofit/roofitcore/src/RooDataSet.cxx:1669
#10 0x00007c07e71ba718 in RooDataSet::RooDataSet (this=this
entry=0x7ffe4878b190, name=..., title=..., vars=..., arg1=..., arg2=..., arg3=..., arg4=..., arg5=..., arg6=..., arg7=..., arg8=...) at /home/tomas/ROOT_DEBUG/root_src/roofit/roofitcore/src/RooDataSet.cxx:463
#11 0x00007c07e596679c in RooStats::HistFactory::HistoToWorkspaceFactoryFast::MakeCombinedModel (this=this
entry=0x7ffe4878b680, ch_names=std::vector of length 8, capacity 8 = {...}, chs=std::vector of length 8, capacity 8 = {...}) at /home/tomas/ROOT_DEBUG/root_src/roofit/histfactory/src/HistoToWorkspaceFactoryFast.cxx:1556
#12 0x00007c07e5968b8e in RooStats::HistFactory::HistoToWorkspaceFactoryFast::MakeCombinedModel (measurement=..., config=...) at /home/tomas/ROOT_DEBUG/root_src/roofit/histfactory/src/HistoToWorkspaceFactoryFast.cxx:295
#13 0x00007c07e596903a in RooStats::HistFactory::HistoToWorkspaceFactoryFast::MakeCombinedModel (measurement=...) at /home/tomas/ROOT_DEBUG/root_src/roofit/histfactory/src/HistoToWorkspaceFactoryFast.cxx:253
#14 0x00007c07e86609fe in MultiFit::CombineWS (this=this
entry=0x5a2d41fe0470) at /home/tomas/TRExFitter/Root/MultiFit.cc:308
#15 0x00007c07e8661505 in MultiFit::SaveCombinedWS (this=this
entry=0x5a2d41fe0470) at /home/tomas/TRExFitter/Root/MultiFit.cc:340
#16 0x00005a2d0f43aa50 in FitExample (opt="mw", configFile="combined_Asimov.config", options="") at /home/tomas/TRExFitter/util/trex-fitter.cc:137
#17 0x00005a2d0f436d90 in main (argc=3, argv=0x7ffe4878c698) at /home/tomas/TRExFitter/util/trex-fitter.cc:703

Reproducer

void mwe() {
  TFile* rootFile1 = TFile::Open("asimov_scaled_2.946_combined_asimov_scaled_2.946_model.root","read");
  std::unique_ptr<RooStats::HistFactory::Measurement> meas(dynamic_cast<RooStats::HistFactory::Measurement*>(rootFile1-> Get("asimov_scaled_2.946")));

  TFile* rootFile2 = TFile::Open("multiclass1RCbinary0RC_PCBTforWZ_final_SysScaledLumi100tWZ_combined_multiclass1RCbinary0RC_PCBTforWZ_final_SysScaledLumi100tWZ_model.root","read");
  std::unique_ptr<RooStats::HistFactory::Measurement> meas2(dynamic_cast<RooStats::HistFactory::Measurement*>(rootFile2-> Get("multiclass1RCbinary0RC_PCBTforWZ_final_SysScaledLumi100tWZ")));

  auto channels = meas2->GetChannels();
  for (auto& channel : channels) {
      if (!meas->HasChannel(channel.GetName())) meas->AddChannel(channel);
  }
  RooStats::HistFactory::HistoToWorkspaceFactoryFast factory(*meas);
  std::unique_ptr<RooWorkspace> ws(factory.MakeCombinedModel(*meas));
}

Note the input workspaces are considered confidential, but they have been shared with @guitargeek.

ROOT version

ROOT Version: 6.39.01
Built for linuxx8664gcc on Jan 29 2026, 07:58:17
From heads/master@v6-39-01-856-gee341853130

Installation method

Built from source

Operating system

Ubuntu 25.10

Additional context

No response