I have a root file containing a TTree, of which several branches are TObjArrays containing TH1Ds. When I try to access this from CINT, it works exactly as expected and I can extract and draw the histograms. However, when I try to access it from PyROOT, I get a segfault.
Here’s an example of an interpreter session trying to read the data:
In [1]: _file0 = ROOT.TFile("toy_with_data-run_0-expts_0_0.root")
In [2]: tr = _file0.Get("fitnt")
In [3]: for b in tr.GetListOfBranches():
b.Print()
...:
*Br 0 :best_fit_params : FitParamList *
*Entries : 1 : Total Size= 7302 bytes File Size = 3567 *
*Baskets : 1 : Basket Size= 1280000 bytes Compression= 1.90 *
*............................................................................*
*Br 1 :best_fit_params_fit1 : FitParamList *
*Entries : 1 : Total Size= 7327 bytes File Size = 3572 *
*Baskets : 1 : Basket Size= 1280000 bytes Compression= 1.90 *
*............................................................................*
*Br 2 :best_fit_params_fit2 : FitParamList *
*Entries : 1 : Total Size= 7327 bytes File Size = 3665 *
*Baskets : 1 : Basket Size= 1280000 bytes Compression= 1.85 *
*............................................................................*
*Br 3 :data : TObjArray *
*Entries : 1 : Total Size= 4145 bytes File Size = 877 *
*Baskets : 1 : Basket Size= 1280000 bytes Compression= 4.19 *
*............................................................................*
*Br 4 :best_fit_pdf : TObjArray *
*Entries : 1 : Total Size= 106927 bytes File Size = 27829 *
*Baskets : 1 : Basket Size= 1280000 bytes Compression= 3.82 *
*............................................................................*
*Br 5 :best_fit_pdf_fit1 : TObjArray *
*Entries : 1 : Total Size= 106947 bytes File Size = 27838 *
*Baskets : 1 : Basket Size= 1280000 bytes Compression= 3.82 *
*............................................................................*
*Br 6 :best_fit_pdf_fit2 : TObjArray *
*Entries : 1 : Total Size= 106947 bytes File Size = 27830 *
*Baskets : 1 : Basket Size= 1280000 bytes Compression= 3.82 *
*............................................................................*
In [4]: tr.GetEntries()
Out[4]: 1L
In [5]: tr.GetEntry(0)
Out[5]: 342677
In [6]: tr.data
*** Break *** segmentation violation
===========================================================
There was a crash.
This is the entire stack trace of all threads:
===========================================================
Thread 3 (Thread 0x7f307434a700 (LWP 19363)):
#0 sem_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/sem_wait.S:85
#1 0x0000000000564f1d in ?? ()
#2 0x000000000052c6d5 in PyEval_EvalFrameEx ()
#3 0x000000000055c594 in PyEval_EvalCodeEx ()
#4 0x000000000052ca8d in PyEval_EvalFrameEx ()
#5 0x000000000055c594 in PyEval_EvalCodeEx ()
#6 0x000000000052ca8d in PyEval_EvalFrameEx ()
#7 0x000000000056d0aa in ?? ()
#8 0x000000000052e1e6 in PyEval_EvalFrameEx ()
#9 0x000000000055c594 in PyEval_EvalCodeEx ()
#10 0x000000000052ca8d in PyEval_EvalFrameEx ()
#11 0x000000000052cf32 in PyEval_EvalFrameEx ()
#12 0x000000000052cf32 in PyEval_EvalFrameEx ()
#13 0x000000000056d0aa in ?? ()
#14 0x00000000004d9854 in ?? ()
#15 0x00000000004da20b in PyEval_CallObjectWithKeywords ()
#16 0x00000000005872b2 in ?? ()
#17 0x00007f3077c13182 in start_thread (arg=0x7f307434a700) at pthread_create.c:312
#18 0x00007f307794030d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
Thread 2 (Thread 0x7f30681c4700 (LWP 19375)):
#0 sem_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/sem_wait.S:85
#1 0x00000000005519f0 in ?? ()
#2 0x000000000052c6d5 in PyEval_EvalFrameEx ()
#3 0x000000000056d0aa in ?? ()
#4 0x000000000052e1e6 in PyEval_EvalFrameEx ()
#5 0x000000000052cf32 in PyEval_EvalFrameEx ()
#6 0x000000000052cf32 in PyEval_EvalFrameEx ()
#7 0x000000000056d0aa in ?? ()
#8 0x00000000004d9854 in ?? ()
#9 0x00000000004da20b in PyEval_CallObjectWithKeywords ()
#10 0x00000000005872b2 in ?? ()
#11 0x00007f3077c13182 in start_thread (arg=0x7f30681c4700) at pthread_create.c:312
#12 0x00007f307794030d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
Thread 1 (Thread 0x7f3078026740 (LWP 19362)):
#0 0x00007f30779069d9 in __libc_waitpid (pid=19378, stat_loc=stat_loc
entry=0x7fff5a232380, options=options
entry=0) at ../sysdeps/unix/sysv/linux/waitpid.c:40
#1 0x00007f307788b592 in do_system (line=<optimised out>) at ../sysdeps/posix/system.c:148
#2 0x00007f307216b0d3 in TUnixSystem::StackTrace() () from /home/steve/packages/root/v5_34_18/lib/libCore.so.5.34
#3 0x00007f307216cdbc in TUnixSystem::DispatchSignals(ESignals) () from /home/steve/packages/root/v5_34_18/lib/libCore.so.5.34
#4 <signal handler called>
#5 0x0000000000000000 in ?? ()
#6 0x00007f307213cfa9 in TClass::GetActualClass(void const*) const () from /home/steve/packages/root/v5_34_18/lib/libCore.so.5.34
#7 0x00007f307328807b in PyROOT::BindRootObject(void*, TClass*, bool) () from /home/steve/packages/root/v5_34_18/lib/libPyROOT.so
#8 0x00007f307328375b in PyROOT::TTreeGetAttr(PyROOT::ObjectProxy*, _object*) () from /home/steve/packages/root/v5_34_18/lib/libPyROOT.so
#9 0x00007f307328d65b in PyROOT::im_call(_object*, _object*, _object*) () from /home/steve/packages/root/v5_34_18/lib/libPyROOT.so
#10 0x000000000054a328 in PyObject_CallFunctionObjArgs ()
#11 0x0000000000598b5b in ?? ()
#12 0x00000000004ce73d in ?? ()
#13 0x000000000052c461 in PyEval_EvalFrameEx ()
#14 0x000000000055c594 in PyEval_EvalCodeEx ()
#15 0x00000000005b7392 in PyEval_EvalCode ()
#16 0x00000000005315d8 in PyEval_EvalFrameEx ()
#17 0x000000000055c594 in PyEval_EvalCodeEx ()
#18 0x000000000052ca8d in PyEval_EvalFrameEx ()
#19 0x000000000055c594 in PyEval_EvalCodeEx ()
#20 0x000000000052ca8d in PyEval_EvalFrameEx ()
#21 0x000000000055c594 in PyEval_EvalCodeEx ()
#22 0x000000000052ca8d in PyEval_EvalFrameEx ()
#23 0x000000000055c594 in PyEval_EvalCodeEx ()
#24 0x000000000052ca8d in PyEval_EvalFrameEx ()
#25 0x000000000055c594 in PyEval_EvalCodeEx ()
#26 0x000000000052ca8d in PyEval_EvalFrameEx ()
#27 0x000000000055c594 in PyEval_EvalCodeEx ()
#28 0x000000000052ca8d in PyEval_EvalFrameEx ()
#29 0x000000000056d0aa in ?? ()
#30 0x000000000052e1e6 in PyEval_EvalFrameEx ()
#31 0x000000000055c594 in PyEval_EvalCodeEx ()
#32 0x000000000052ca8d in PyEval_EvalFrameEx ()
#33 0x000000000055c594 in PyEval_EvalCodeEx ()
#34 0x00000000005b7392 in PyEval_EvalCode ()
#35 0x0000000000469663 in ?? ()
#36 0x00000000004699e3 in PyRun_FileExFlags ()
#37 0x0000000000469f1c in PyRun_SimpleFileExFlags ()
#38 0x000000000046ab81 in Py_Main ()
#39 0x00007f3077866ec5 in __libc_start_main (main=0x46ac3f <main>, argc=4, argv=0x7fff5a236398, init=<optimised out>, fini=<optimised out>, rtld_fini=<optimised out>, stack_end=0x7fff5a236388) at libc-start.c:287
#40 0x000000000057497e in _start ()
===========================================================
The lines below might hint at the cause of the crash.
If they do not help you then please submit a bug report at
http://root.cern.ch/bugs. Please post the ENTIRE stack trace
from above as an attachment in addition to anything else
that might help us fixing this issue.
===========================================================
#5 0x0000000000000000 in ?? ()
#6 0x00007f307213cfa9 in TClass::GetActualClass(void const*) const () from /home/steve/packages/root/v5_34_18/lib/libCore.so.5.34
#7 0x00007f307328807b in PyROOT::BindRootObject(void*, TClass*, bool) () from /home/steve/packages/root/v5_34_18/lib/libPyROOT.so
#8 0x00007f307328375b in PyROOT::TTreeGetAttr(PyROOT::ObjectProxy*, _object*) () from /home/steve/packages/root/v5_34_18/lib/libPyROOT.so
#9 0x00007f307328d65b in PyROOT::im_call(_object*, _object*, _object*) () from /home/steve/packages/root/v5_34_18/lib/libPyROOT.so
#10 0x000000000054a328 in PyObject_CallFunctionObjArgs ()
#11 0x0000000000598b5b in ?? ()
#12 0x00000000004ce73d in ?? ()
#13 0x000000000052c461 in PyEval_EvalFrameEx ()
#14 0x000000000055c594 in PyEval_EvalCodeEx ()
#15 0x00000000005b7392 in PyEval_EvalCode ()
#16 0x00000000005315d8 in PyEval_EvalFrameEx ()
#17 0x000000000055c594 in PyEval_EvalCodeEx ()
#18 0x000000000052ca8d in PyEval_EvalFrameEx ()
#19 0x000000000055c594 in PyEval_EvalCodeEx ()
#20 0x000000000052ca8d in PyEval_EvalFrameEx ()
#21 0x000000000055c594 in PyEval_EvalCodeEx ()
#22 0x000000000052ca8d in PyEval_EvalFrameEx ()
#23 0x000000000055c594 in PyEval_EvalCodeEx ()
#24 0x000000000052ca8d in PyEval_EvalFrameEx ()
#25 0x000000000055c594 in PyEval_EvalCodeEx ()
#26 0x000000000052ca8d in PyEval_EvalFrameEx ()
#27 0x000000000055c594 in PyEval_EvalCodeEx ()
#28 0x000000000052ca8d in PyEval_EvalFrameEx ()
#29 0x000000000056d0aa in ?? ()
#30 0x000000000052e1e6 in PyEval_EvalFrameEx ()
#31 0x000000000055c594 in PyEval_EvalCodeEx ()
#32 0x000000000052ca8d in PyEval_EvalFrameEx ()
#33 0x000000000055c594 in PyEval_EvalCodeEx ()
#34 0x00000000005b7392 in PyEval_EvalCode ()
#35 0x0000000000469663 in ?? ()
#36 0x00000000004699e3 in PyRun_FileExFlags ()
#37 0x0000000000469f1c in PyRun_SimpleFileExFlags ()
#38 0x000000000046ab81 in Py_Main ()
#39 0x00007f3077866ec5 in __libc_start_main (main=0x46ac3f <main>, argc=4, argv=0x7fff5a236398, init=<optimised out>, fini=<optimised out>, rtld_fini=<optimised out>, stack_end=0x7fff5a236388) at libc-start.c:287
#40 0x000000000057497e in _start ()
===========================================================The other branches in the file are made with my own classes, and work as expected in both CINT and PyROOT. All 4 TObjArray branches exhibit the same behaviour, working correctly in CINT and segfaulting in PyROOT.
I’m using ROOT v5-34-18.