Problem deleting TList of TCanvases

ROOT
1

Dear support,

in my case in one root session i am creating and deleting TList of TCanvas, TH1, THStack and when i try to use TTList::Delete() from time to time i get errors like this

#8  0x000000002ee27da0 in ?? ()                                                                                                                                                                                                                                                                                                                                                                                                             
#9  0x00007fcec3fe6159 in TList::RecursiveRemove(TObject*) () from /usr/lib64/root/libCore.so.6.38                                                                                                                                                                                                                                                                                                                                          
#10 0x00007fcec31e7c03 in TTree::RecursiveRemove(TObject*) () from /usr/lib64/root/libTree.so.6.38                                                                                                                                                                                                                                                                                                                                          
#11 0x00007fcec3fd9df5 in THashList::RecursiveRemove(TObject*) () from /usr/lib64/root/libCore.so.6.38                                                                                                                                                                                                                                                                                                                                      
#12 0x00007fcec3fe6435 in TList::RecursiveRemove(TObject*) () from /usr/lib64/root/libCore.so.6.38                                                                                                                                                                                                                                                                                                                                          
#13 0x00007fcec3fd9df5 in THashList::RecursiveRemove(TObject*) () from /usr/lib64/root/libCore.so.6.38                                                                                                                                                                                                                                                                                                                                      
#14 0x00007fcec3f7d33a in TROOT::RecursiveRemove(TObject*) () from /usr/lib64/root/libCore.so.6.38                                                                                                                                                                                                                                                                                                                                          
#15 0x00007fcec3488211 in TPave::~TPave() () from /usr/lib64/root/libGraf.so.6.38                                                                                                                                                                                                                                                                                                                                                           
#16 0x00007fcec348a895 in TPaveText::~TPaveText() () from /usr/lib64/root/libGraf.so.6.38                                                                                                                                                                                                                                                                                                                                                   
#17 0x00007fcec3fe4fe1 in TList::Clear(char const*) () from /usr/lib64/root/libCore.so.6.38                                                                                                                                                                                                                                                                                                                                                 
#18 0x00007fcec32f54cf in TPad::Close(char const*) () from /usr/lib64/root/libGpad.so.6.38                                                                                                                                                                                                                                                                                                                                                  
#19 0x00007fcec32f5899 in TPad::~TPad() () from /usr/lib64/root/libGpad.so.6.38                                                                                                                                                                                                                                                                                                                                                             
#20 0x00007fcec32f5a85 in TPad::~TPad() () from /usr/lib64/root/libGpad.so.6.38                                                                                                                                                                                                                                                                                                                                                             
#21 0x00007fcec3fe4fe1 in TList::Clear(char const*) () from /usr/lib64/root/libCore.so.6.38                                                                                                                                                                                                                                                                                                                                                 
#22 0x00007fcec32f54cf in TPad::Close(char const*) () from /usr/lib64/root/libGpad.so.6.38
#23 0x00007fcec32d82fc in TCanvas::Close(char const*) () from /usr/lib64/root/libGpad.so.6.38
#24 0x00007fcec32cf953 in TCanvas::Destructor() () from /usr/lib64/root/libGpad.so.6.38
#25 0x00007fcec32d2b6c in TCanvas::~TCanvas() () from /usr/lib64/root/libGpad.so.6.38
#26 0x00007fcec32d2bb5 in TCanvas::~TCanvas() () from /usr/lib64/root/libGpad.so.6.38
#27 0x00007fcec3fe8908 in TList::Delete(char const*) () from /usr/lib64/root/libCore.so.6.38
#28 0x00007fcec3fe4bdd in TList::Clear(char const*) () from /usr/lib64/root/libCore.so.6.38
#29 0x00007fcec3fda6da in TList::~TList() () from /usr/lib64/root/libCore.so.6.38
#30 0x00007fcec3fda875 in TList::~TList() () from /usr/lib64/root/libCore.so.6.38
#31 0x00007fcea15fa533 in ?? ()
#32 0x000000000000001f in ?? ()
#33 0x00007fff92418378 in ?? ()
#34 0x0000000000000004 in ?? ()
#35 0x00007f006e61654d in ?? ()
#36 0x000000000000001f in ?? ()
#37 0x0000000000000000 in ?? ()

I dont have simple macro to reproduce it yet, but i wanted to start discussion about it so we can interact and find the way how to correctly delete TList of TCanvas and other objects

Thanks

Martin

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ROOT Version: 6.38.00
Platform: Any
Compiler: g++ (GCC) 15.2.1 20251211

2

Dear @mvala ,

Thanks for reaching out! Do you need to manually delete the TList and other objects? Could we envision a way to ensure that only automatic memory management is applied via stack-based variables and std::unique_ptrs? There may be something missing even afterwards, but starting with that will give us a clear state to work from.

Cheers,
Vincenzo

3

Let’s start by this scenario. I am using TTree and i have one branch TList and i add different histogram, canvases, hstacks and so (i might add canvas and inside one histogram and addtionally i can added to the list), what is inside list i dont have control, because user is doing this. I fill TTree with many entries. When i am reading back by simple call many tree→GetEntry(...) i am getting memory leak. So, i tried to delete list before calling tree→GetEntry(...) . Here is part of source code
https://gitlab.com/ndmspc/ndmspc/-/blob/develop/core/NTreeBranch.cxx?ref_type=heads#L125

Since simple doing list→Delete() causing me double deletes, i let copilot to generate some function and he made one which i am using now

https://gitlab.com/ndmspc/ndmspc/-/blob/develop/base/NUtils.cxx?ref_type=heads#L1798

4

Dear @mvala ,

That looks like a lot of work just to workaround this double-delete issue, I hope we can improve the situation together!

I’m trying to understand how we could work towards a reproducer. Just to start with, you mention you have a TList branch and then you add histograms and other objects to this branch. Could this be some pseudo-code that would serve as a starting point for a reproducer?


auto f = std::make_unique<TFile>();
auto t = std::make_unique<TTree>();

TList l{};
t->Branch("mylist", &l);

for (n in n_entries){
    // Modify l, add objects to it
    t->Fill();
}

What would you add to this pseudo code to make it look like your example?
Cheers,
Vincenzo