The following code block will cause a segfault (root 5.27 and gcc 4.1.2):
TChain* c1 = new TChain("data");
c1->Add("data*.root");
TChain* c2 = new TChain("cuts");
c2->Add("cuts*.root");
c1->AddFriend(c2);
c1->Draw("varincutstree");
c1->RemoveFriend(c2);
delete c2;
c1->SetBranchStatus("*",0);
It seems c1 still has some reference to the branches in c2 even after the friend is removed (and it is removed from the ListOfFriends).
Until a bugfix happens, is there a reasonably convenient workaround? The use case is that my dataset is broken up into trees with interesting data and trees that are only really used to generate cuts. So I want to temporarily add the cut trees as friends just to generate a TEntryList, then get rid of them.
This is corrected in the trunk (revision 46069) and in the v5-34 patch branch (v5.34/02 will be released at the end of the week and will include this fix).
Apriori to somewhat work around the problem you should just need:parent->GetTree()->RemoveFriend( friendChain->GetTree() );