Question

I’m stuck with this annoying segmentation fault when checking if a pointer is 0. This is the problematic code:

bool egammaMVACalib::checkTree()
{
   // Not a TChain
   cout << "a" << endl;
   assert(m_tree);      // crash on line 751 (this one)
   cout << "B" << endl;

m_tree is a data member of egammaMVACalib of type TTree* so I really don’t understand why an assert(m_tree) can raise a segmentation violation. This is the output with the stack trace

a
19:07:25 30574 Wrk-0.9 | *** Break ***: segmentation violation

===========================================================
There was a crash.
This is the entire stack trace of all threads:
===========================================================
#0  0x000000361869a4d5 in waitpid () from /lib64/libc.so.6
#1  0x000000361863c481 in do_system () from /lib64/libc.so.6
#2  0x00002ac5099cb322 in TUnixSystem::StackTrace() ()
    from /usr/local/proof/root/lib/libCore.so
#3  0x00002ac5099c7fea in TUnixSystem::DispatchSignals(ESignals) ()
    from /usr/local/proof/root/lib/libCore.so
#4  <signal handler called>
#5  egammaMVACalib::checkTree (this=0x0) at ../Root/egammaMVACalib.cxx:751
#6  0x00002ac5117e5563 in egammaMVACalib::LoadVariables (this=0x1, index=0)
    at ../Root/egammaMVACalib.cxx:492

Answer 1

If you look at frame #5 your this pointer is null. Which means the problem started there. Seg fault at the assertion is merely the repurcusion of that !