RDataFrame created from TChain after calling TChain::AddFriend() crashes when trying to plot a variable if MultiThread is enabled

TChain* chain = new TChain();

chain->Add("file.root/myTree");

TChain* fchain = new TChain();

fchain->Add("filez.root/myTree");

chain->AddFriend(fchain);

ROOT::EnableImplicitMT(1);

ROOT::RDataFrame rdf(*chain);

auto h = rdf.Histo1D("px");

h->Draw();

Error in <TFile::GetObjectChecked>: The provided key name is invalid

.

 *** Break *** segmentation violation

===========================================================

There was a crash.

This is the entire stack trace of all threads:

===========================================================

#0  0x00007fefc6b96687 in __GI___waitpid (pid=14397, stat_loc=stat_l

oc

entry=0x7ffcaf4b2c28, options=options

entry=0) at ../sysdeps/unix/sysv/linux/waitpid.c:30

#1  0x00007fefc6b01067 in do_system (line=<optimized out>) at ../sys

deps/posix/system.c:149

#2  0x00007fefc773ae23 in TUnixSystem::StackTrace() () from /home/ma

ssimiliano/root-devel/build_master/lib/libCore.so

#3  0x00007fefc773d814 in TUnixSystem::DispatchSignals(ESignals) () 

from /home/massimiliano/root-devel/build_master/lib/libCore.so

#4  <signal handler called>

#5  0x00007fefb3a05c93 in ROOT::TTreeProcessorMT::Process(std::funct

ion<void (TTreeReader&)>) () from /home/massimiliano/root-devel/buil

d_master/lib/libTreePlayer.so

#6  0x00007fefb3d153f7 in ROOT::Detail::RDF::RLoopManager::RunTreePr

ocessorMT() () from /home/massimiliano/root-devel/build_master/lib/l

ibROOTDataFrame.so

#7  0x00007fefb3d159e5 in ROOT::Detail::RDF::RLoopManager::Run() () 

from /home/massimiliano/root-devel/build_master/lib/libROOTDataFrame

.so

#8  0x00007fefc7fdeb1f in ?? ()

#9  0x00007ffcaf4b5a30 in ?? ()

#10 0x00007ffcaf4b5b28 in ?? ()

#11 0x00007ffcaf4b5a30 in ?? ()

#12 0x00007fefc7fdeb77 in ?? ()

#13 0x00007ffcaf4b5b28 in ?? ()

#14 0x00007ffcaf4b5b28 in ?? ()

#15 0x00007ffcaf4b5a50 in ?? ()

#16 0x00007fefc7fded9c in ?? ()

#17 0x00007ffcaf4b5b60 in ?? ()

#18 0x00007ffcaf4b5b28 in ?? ()

#19 0x00007ffcaf4b5c00 in ?? ()

#20 0x00007fefc7fdd2c4 in ?? ()

#21 0x0000000000000000 in ?? ()

===========================================================

The lines below might hint at the cause of the crash.

You may get help by asking at the ROOT forum http://root.cern.ch/for

um

Only if you are really convinced it is a bug in ROOT then please sub

mit a

report at http://root.cern.ch/bugs Please post the ENTIRE stack trac

e

from above as an attachment in addition to anything else

that might help us fixing this issue.

===========================================================

#5  0x00007fefb3a05c93 in ROOT::TTreeProcessorMT::Process(std::funct

ion<void (TTreeReader&)>) () from /home/massimiliano/root-devel/buil

d_master/lib/libTreePlayer.so

#6  0x00007fefb3d153f7 in ROOT::Detail::RDF::RLoopManager::RunTreePr

ocessorMT() () from /home/massimiliano/root-devel/build_master/lib/l

ibROOTDataFrame.so

#7  0x00007fefb3d159e5 in ROOT::Detail::RDF::RLoopManager::Run() () 

from /home/massimiliano/root-devel/build_master/lib/libROOTDataFrame

.so

#8  0x00007fefc7fdeb1f in ?? ()

#9  0x00007ffcaf4b5a30 in ?? ()

#10 0x00007ffcaf4b5b28 in ?? ()

#11 0x00007ffcaf4b5a30 in ?? ()

#12 0x00007fefc7fdeb77 in ?? ()

#13 0x00007ffcaf4b5b28 in ?? ()

#14 0x00007ffcaf4b5b28 in ?? ()

#15 0x00007ffcaf4b5a50 in ?? ()

#16 0x00007fefc7fded9c in ?? ()

#17 0x00007ffcaf4b5b60 in ?? ()

#18 0x00007ffcaf4b5b28 in ?? ()

#19 0x00007ffcaf4b5c00 in ?? ()

#20 0x00007fefc7fdd2c4 in ?? ()

#21 0x0000000000000000 in ?? ()

===========================================================

ROOT::EnableImplicitMT(1);