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[FIXED] Memory leak with TClonesArray and std::vector [message #15320] Fri, 23 August 2013 09:36 Go to previous message
Klaus Götzen is currently offline  Klaus Götzen
Messages: 293
Registered: June 2006
Location: GSI
first-grade participant
From: *

this is more a ROOT related question, but maybe somebody from this club has an idea or knows about it.

The problem is that I observed quite a severe memory leak (just looking with 'top' how memory consumption of the job develops), apparently because the RhoCandidate stores the daughter pointers in a std::vector<RhoCandidate*>.

I isolated the problem in a short ROOT macro looking like:

#include "TClonesArray.h"
#include <vector>
#include <iostream>

// very simple class to be used with a TClonesArray
class MyClass: public TObject 
    MyClass() {};
    ~MyClass() {};
    std::vector<int> fVec;

void testtca(int num=100000)
    TClonesArray *tca = new TClonesArray("MyClass",1100);
    for (int i=0;i<num;++i) 
        if ((i%100)==0) cout <<i<<endl;
	for (int  j=0;j<1000;++j) 
	    MyClass *c= new ((*tca)[j]) MyClass();
	    c->fVec.push_back(42); // <-  THIS IS THE BAD GUY!!1

When you run this with 'root -l -b -q testtca.C+' you will see the memory growing very!! fast (be careful, you might want to reduce num).

When you comment out the line with 'push_back(42)' it works perfectly well like you would expect it from a TClonesArray. The interesting part is, that even the 'fVec.clear()' directly after the push_back does not help at all to avoid the problem (most likely because clear() does not really release the allocated memory of the vector). And I think even an appropriate cleanup in the destructor wouldn't really help, since the objects in a TCA are not deleted anyway, right?

I didn't find any way to fix this leak up to now. Does somebody here has an idea how to avoid that problem? Or a solution for a dynamic container for pointers different from std::vector?


[Updated on: Fri, 23 August 2013 17:18] by Moderator

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