Static pointers to histograms and adding operation

kame · February 23, 2005, 8:05am

Dear ROOT developers,

I am using version 4.02/00 on RedHat Linux 9.
The following script causes a crash after executed 10 times or so.

— start —
#include “TH1.h”

TH1F *h;
TH1F *h2;
TH1F *h3;

void test()
{
if (h) h->Delete();
if (h2) h2->Delete();
if (h3) h3->Delete();

h = new TH1F(“h”, “”, 100, 0, 100);
h2 = (TH1F *) h->Clone(“h2”);
h3 = (TH1F *) h->Clone(“h3”);

// do something

*h3 = *h + *h2;

}
— end —

root [0] .L test.C++
Info in TUnixSystem::ACLiC: creating shared library /home/kameoka/macros/root/test_C.so
root [1] test()
root [2] test()
root [3] test()
root [4] test()
root [5] test()
root [6] test()
root [7] test()
root [8] test()
root [9] test()
root [10] test()

*** Break *** segmentation violation
Generating stack trace…
0x4121d5d8 in from /lib/i686/libc.so.6
0x401a2e68 in TList::Remove(TObject*) + 0x36 from /usr/local/cern/root-4.02.00/lib/libCore.so
0x401a0d1a in THashList::Remove(TObject*) + 0x46 from /usr/local/cern/root-4.02.00/lib/libCore.so
0x408ff899 in TH1::~TH1 not-in-charge + 0x141 from /usr/local/cern/root-4.02.00/lib/libHist.so
0x409141ab in TH1F::~TH1F in-charge deleting + 0x71 from /usr/local/cern/root-4.02.00/lib/libHist.so
0x40147d65 in TObject::Delete(char const*) + 0x41 from /usr/local/cern/root-4.02.00/lib/libCore.so
0x41b9c62e in test() + 0x36 from /home/kameoka/macros/root/test_C.so
0x41b9c858 in from /home/kameoka/macros/root/test_C.so
0x407078e7 in G__call_cppfunc + 0x266 from /usr/local/cern/root-4.02.00/lib/libCint.so
0x406f6fde in G__interpret_func + 0x706 from /usr/local/cern/root-4.02.00/lib/libCint.so
0x406df1c5 in G__getfunction + 0x1954 from /usr/local/cern/root-4.02.00/lib/libCint.so
0x406d6176 in G__getitem + 0x5f1 from /usr/local/cern/root-4.02.00/lib/libCint.so
0x406d4d5e in G__getexpr + 0x783e from /usr/local/cern/root-4.02.00/lib/libCint.so
0x4071ca5e in G__exec_function + 0x1d5 from /usr/local/cern/root-4.02.00/lib/libCint.so
0x407236ab in G__exec_statement + 0x23eb from /usr/local/cern/root-4.02.00/lib/libCint.so
0x406bdf3b in G__exec_tempfile_core + 0x2ce from /usr/local/cern/root-4.02.00/lib/libCint.so
0x406be118 in G__exec_tempfile_fp + 0x22 from /usr/local/cern/root-4.02.00/lib/libCint.so
0x4072b93e in G__process_cmd + 0x45f7 from /usr/local/cern/root-4.02.00/lib/libCint.so
0x401ac419 in TCint::ProcessLine(char const*, TInterpreter::EErrorCode*) + 0xa9 from /usr/local/cern/root-4.02.00/lib/libCore.so
0x4010bdec in TApplication::ProcessLine(char const*, bool, int*) + 0x670 from /usr/local/cern/root-4.02.00/lib/libCore.so
0x4109f069 in TRint::HandleTermInput() + 0x1dd from /usr/local/cern/root-4.02.00/lib/libRint.so
0x4109deda in TTermInputHandler::Notify() + 0x24 from /usr/local/cern/root-4.02.00/lib/libRint.so
0x4109f9e2 in TTermInputHandler::ReadNotify() + 0x12 from /usr/local/cern/root-4.02.00/lib/libRint.so
0x40235397 in TUnixSystem::CheckDescriptors() + 0x143 from /usr/local/cern/root-4.02.00/lib/libCore.so
0x40234287 in TUnixSystem::DispatchOneEvent(bool) + 0x161 from /usr/local/cern/root-4.02.00/lib/libCore.so
0x4016f5a8 in TSystem::InnerLoop() + 0x18 from /usr/local/cern/root-4.02.00/lib/libCore.so
0x4016f54d in TSystem::Run() + 0x6f from /usr/local/cern/root-4.02.00/lib/libCore.so
0x4010c860 in TApplication::Run(bool) + 0x32 from /usr/local/cern/root-4.02.00/lib/libCore.so
0x4109eb65 in TRint::Run(bool) + 0x327 from /usr/local/cern/root-4.02.00/lib/libRint.so
0x0804886d in main + 0x71 from /usr/local/cern/root-4.02.00/bin/root.exe
0x4120aa07 in __libc_start_main + 0xc7 from /lib/i686/libc.so.6
0x0804876d in _Unwind_Resume + 0x31 from /usr/local/cern/root-4.02.00/bin/root.exe

I feel that the combination of static pointers to histograms and adding operation for them is related to the problem.
Could you kindly tell me what is the point ?

–
Kame

brun · February 23, 2005, 9:14am

Change your code to:
#include “TH1.h”

TH1F *h=0;
TH1F *h2=0;
TH1F *h3=0;

void kame()
{
if (h) delete h;
if (h2) delete h2;
if (h3) delete h3;

h = new TH1F(“h”, “”, 100, 0, 100);
h2 = (TH1F *) h->Clone(“h2”);
h3 = (TH1F *) h->Clone(“h3”);

// do something

*h3 = *h + *h2;

}

Rene

kame · February 23, 2005, 9:39am

Thank you for your reply.

I modified the script as you told, but it also crashed after 7 times executions.

root [8] test()

*** Break *** segmentation violation
Generating stack trace…
0x4121d5d8 in from /lib/i686/libc.so.6
0x401a164a in THashTable::FindObject(TObject const*) const + 0x66 from /usr/local/cern/root-4.02.00/lib/libCore.so
0x401a0d02 in THashList::Remove(TObject*) + 0x2e from /usr/local/cern/root-4.02.00/lib/libCore.so
0x408ff899 in TH1::~TH1 not-in-charge + 0x141 from /usr/local/cern/root-4.02.00/lib/libHist.so
0x409141ab in TH1F::~TH1F in-charge deleting + 0x71 from /usr/local/cern/root-4.02.00/lib/libHist.so
0x41b9c664 in test() + 0x6c from /home/kameoka/macros/root/test_C.so
0x41b9c84c in from /home/kameoka/macros/root/test_C.so
0x407078e7 in G__call_cppfunc + 0x266 from /usr/local/cern/root-4.02.00/lib/libCint.so
0x406f6fde in G__interpret_func + 0x706 from /usr/local/cern/root-4.02.00/lib/libCint.so
0x406df1c5 in G__getfunction + 0x1954 from /usr/local/cern/root-4.02.00/lib/libCint.so
0x406d6176 in G__getitem + 0x5f1 from /usr/local/cern/root-4.02.00/lib/libCint.so
0x406d4d5e in G__getexpr + 0x783e from /usr/local/cern/root-4.02.00/lib/libCint.so
0x4071ca5e in G__exec_function + 0x1d5 from /usr/local/cern/root-4.02.00/lib/libCint.so
0x407236ab in G__exec_statement + 0x23eb from /usr/local/cern/root-4.02.00/lib/libCint.so
0x406bdf3b in G__exec_tempfile_core + 0x2ce from /usr/local/cern/root-4.02.00/lib/libCint.so
0x406be118 in G__exec_tempfile_fp + 0x22 from /usr/local/cern/root-4.02.00/lib/libCint.so
0x4072b93e in G__process_cmd + 0x45f7 from /usr/local/cern/root-4.02.00/lib/libCint.so
0x401ac419 in TCint::ProcessLine(char const*, TInterpreter::EErrorCode*) + 0xa9 from /usr/local/cern/root-4.02.00/lib/libCore.so
0x4010bdec in TApplication::ProcessLine(char const*, bool, int*) + 0x670 from /usr/local/cern/root-4.02.00/lib/libCore.so
0x4109f069 in TRint::HandleTermInput() + 0x1dd from /usr/local/cern/root-4.02.00/lib/libRint.so
0x4109deda in TTermInputHandler::Notify() + 0x24 from /usr/local/cern/root-4.02.00/lib/libRint.so
0x4109f9e2 in TTermInputHandler::ReadNotify() + 0x12 from /usr/local/cern/root-4.02.00/lib/libRint.so
0x40235397 in TUnixSystem::CheckDescriptors() + 0x143 from /usr/local/cern/root-4.02.00/lib/libCore.so
0x40234287 in TUnixSystem::DispatchOneEvent(bool) + 0x161 from /usr/local/cern/root-4.02.00/lib/libCore.so
0x4016f5a8 in TSystem::InnerLoop() + 0x18 from /usr/local/cern/root-4.02.00/lib/libCore.so
0x4016f54d in TSystem::Run() + 0x6f from /usr/local/cern/root-4.02.00/lib/libCore.so
0x4010c860 in TApplication::Run(bool) + 0x32 from /usr/local/cern/root-4.02.00/lib/libCore.so
0x4109eb65 in TRint::Run(bool) + 0x327 from /usr/local/cern/root-4.02.00/lib/libRint.so
0x0804886d in main + 0x71 from /usr/local/cern/root-4.02.00/bin/root.exe
0x4120aa07 in __libc_start_main + 0xc7 from /lib/i686/libc.so.6
0x0804876d in _Unwind_Resume + 0x31 from /usr/local/cern/root-4.02.00/bin/root.exe

Axel · February 23, 2005, 4:04pm

Hi Kame,
this happens because you’re expecting the h, h2, h3 pointers to “survive” from one call to the next - but that’s not the case. When loading the library they will all be initialized to 0 (according to your lines 3…5), afterwards they wont. So next time you call the function kame(), h, h2, and h3 are uninitialized: they do not point to the histograms from the previous call to kame(). This is not a problem with Cint, it’s C(++) and thus a problem with your code. As a work-around, you can declare your histograms as static:

static TH1F *h=0; static TH1F *h2=0; static TH1F *h3=0;
Axel.

pcanal · February 23, 2005, 6:21pm

Hi,

Actually there is a problem in the TH1F copy constructor.
To work around the problem use

h3->SetDirectory(0); *h3 = *h + *h2;
Note that the result of this code is to have being in a state similiar to having done

*h3 = *h; h3->Add(h2);
In particular, h3 is now named 'h" and not ‘h3’.
To preserve the name you should use

Cheers,
Philippe.

kame · February 24, 2005, 1:40am

Hi Axel,
thank you for your reply.

I don’t think this is wrong C++ code.
If h, h2, h3 are automatic variables, you are right.
But the variables declared out of functions should be always “static” as well as local variables with “static” modifiers,
and C/C++ guarantee to initialize static variables to 0 at the begining of the program.
Actually, the crash occurred although I added “static” modifiers to h, h2, h3.
Am I wrong?

–
Kame

Axel · February 24, 2005, 1:47am

Hi Kame,

[quote=“kame”]I don’t think this is wrong C++ code.[/quote]No, it’s a wrong reply. Sorry about that! As Philippe pointed out, it was a problem with ROOT.
Cheers, Axel.

kame · February 24, 2005, 2:05am

Hi, Philippe.
Thank you for your reply.

I modified the script according to your instruction,
and the problem seems to be fixed.

Thank you very much!

pcanal · February 24, 2005, 4:12am

Please note that the original problem has been solved in the CVS repository.

Cheers,
Philippe