Problem using STL vector<TCut> in ROOT script

ROOT
1

Hello,

I am trying to use a STL vector of TCut in
a function in a ROOT script:

  TCut cut_ZEl="abs(ZId)==11";

  vector<TCut> cuts;
  cuts.push_back(cut_ZEl);

Upon leaving that function, root crashes with the
message:

the vector is located a function in the file utils.C

From other postings, I conclude that is possible to use
stl vectors in ROOT. Any idea why this crashes?

Thanks,
Vuko

2

Could you post the shortest possible RUNNING script reproducing this problem?

Rene

3

Hi Rene,

[quote=“brun”]Could you post the shortest possible RUNNING script reproducing this problem?

Rene[/quote]

Here we go:


#include "TCut.h"
#include <vector>

TCut gimeFinalCut()
{
  
  TCut cut_WZ_found="WlId!=0 && ZId!=0";  // W and Z candidates are there
  TCut cut_Wl_pt="WlPt>20.";

  std::vector<TCut> cuts;
  cuts.push_back(cut_WZ_found);

  return cuts[0];

}

void test_stl()
{
  TCut c = gimeFinalCut();
  cout << "back \n";

}

Actually, the error i s not the same, but it still crashes:

root [0] .x macro/test_stl.C();
*** glibc detected *** double free or corruption (fasttop): 0x091b44d0 ***

Why is that?

Cheers,
Vuko

4

You are making a basic C++ mistake. When exiting from the function gimeFinalCut thestd::vector that you created inside is automatically deleted.
You should use new instead.

Rene

5

[quote=“brun”]Could you post the shortest possible RUNNING script reproducing this problem?

Rene[/quote]
It’s strange, but I don’t see any fatal mistake in the code :frowning:

[code]#include

test()
{
TCut cut_ZEl(“abs(ZId)==11”);
vector cuts;
cuts.push_back(cut_ZEl);
}[/code]

[quote]root [0] .x /tmp/test.C
*** glibc detected *** /home/anar/ROOT/5.19/bin/root.exe: double free or corruption (!prev): 0x099b1cd0 ***[/quote]

Unfortunately I don’t have currently ROOT debug libraries and can’t really play with the debugger. So maybe I am mistaking, but it seems, a double deletion happens…

6

[quote=“brun”]You are making a basic C++ mistake. When exiting from the function gimeFinalCut thestd::vector that you created inside is automatically deleted.
You should use new instead.

Rene[/quote]
He doesn’t use a reference, so I think it is a copy, which will be returned and even RVO will do its job (copy operation will not be performed - optimized out). So there should be no mistake here, maybe only design things.
Or I’ve just overlooked something?

7

Hi Rene,

I was aware of this, but I don’t see why it is a mistake. The vector
I created was intended only for temporary use within that function.
I knew it would be deleted by leaving the function but why should that
cause a crash? I assume the destructor of vector will delete all its
elements, which is fine with me as well, leaving aside the issue
of performance/speed.

I actually tried to compile and run the very same code, just
replacing TCut with a basic type, e.g. int, or some other simple
class, and it works.

Oh, and in case it matters, I am using root v5.18

Thanks!

Vuko

8

Hi,

CINT has problems with interpreting vector. Please create a dictionary for it by putting the following lines into the file vecTCutDict.C:

[code]#include “TCut.h”
#include

#ifdef MAKECINT
#pragma link C++ class vector+;
#endif
[/code]
and run .L vecTCutDict.C+ .x test.C You can also put the line gROOT->ProcessLine(".L vecTCutDict.C+"); into your test() / gimeFinalCut() function.

Cheers, Axel.