Processing /home/alitrain/train-steer/extract_syswatch.C... E-TFile::TFile: file syswatch.root does not exist #0 0x00007f101c48a89e in waitpid () from /lib64/libc.so.6 #1 0x00007f101c41c4e9 in do_system () from /lib64/libc.so.6 #2 0x00007f1020a83c2b in TUnixSystem::Exec (shellcmd=, this=0x2106570) at /alice/.sw/SOURCES/ROOT/v6-14-04/v6-14-04/core/unix/src/TUnixSystem.cxx:2119 #3 TUnixSystem::StackTrace (Python Exception Installation error: gdb.execute_unwinders function is missing: #4 0x00007f1016bf4f55 in cling::MultiplexInterpreterCallbacks::PrintStackTrace (Python Exception Installation error: gdb.execute_unwinders function is missing: #5 0x00007f1016bf49db in cling_runtime_internal_throwIfInvalidPointer (Python Exception Installation error: gdb.execute_unwinders function is missing: #6 0x00007f102141d79e in ?? () #7 0x00000000000f06f0 in ?? () #8 0x0000000005c5ace0 in ?? () #9 0x00007f101c76c120 in ?? () from /lib64/libc.so.6 #10 0x00000000000e6320 in ?? () #11 0x0000000000000001 in ?? () #12 0x000000001c456c88 in ?? () #13 0x0000000000000000 in ?? () E-HandleInterpreterException: Trying to dereference null pointer or trying to call routine taking non-null arguments. Execution of your code was aborted. In file included from input_line_33:1: /home/alitrain/train-steer/extract_syswatch.C:28:26: warning: null passed to a callee that requires a non-null argument [-Wnonnull] TTree *tree = (TTree*) gFile->Get("syswatch"); ^~~~~ /cvmfs/alice.cern.ch/el6-x86_64/Packages/ROOT/v6-14-04-4/include/TFile.h:325:15: note: expanded from macro 'gFile' #define gFile (TFile::CurrentFile()) ^~~~~~~~~~~~~~~~~~~~~~