"pointer being freed was not allocated"

Question

#include <iostream>
#include <fstream>
#include <cmath>
#include <string>
#include <sstream>

using namespace std;

class CFile {
public:
    CFile(string filename); 
    ~CFile();               
    void ReadFile();         
    void WriteFile(string outputFilename);   
    void Calculate();   
    string  m_filename;
    int     m_numberInput;
    double* m_xData;         
    double* m_yData;
    int     m_numberOutput;
    double* m_xDataOut;     
    double* m_yDataOut;
};

CFile::CFile(string filename)
{
    m_filename = filename;
    string line;             
    ifstream myfile(m_filename.c_str());

    if (myfile.is_open())     
    {
        getline(myfile,line);    
        myfile.close();          
        stringstream Str;        
        Str << line; 
        Str >> m_numberInput;
        m_xData = new double[m_numberInput];  
        m_yData = new double[m_numberInput];
        cout << sizeof(m_xData) / sizeof(m_xData[0]) << endl;
    }
    else cout << "Unable to open file.\n";  
}

CFile::~CFile()
{ 
    delete[] m_xData; 
    delete[] m_yData;                                  
    m_xData = 0;                                 
    m_yData = 0;
    delete[] m_xDataOut; 
    delete[] m_yDataOut;                                  
    m_xDataOut = 0;                                 
    m_yDataOut = 0;
}

void CFile::ReadFile()
{
    ifstream infile(m_filename.c_str());
    string line;

    if (infile.is_open())
    {
        int x, y, i = 0;

        while (getline(infile,line))
        {
            infile >> x >> y;
            m_xData[i] = x;
            m_yData[i] = y;
            i++;
        }
        infile.close();
    }
    else cout << "Unable to open file.\n"; 
}

void CFile::WriteFile(string outputFilename)
{
    ofstream outfile(outputFilename.c_str());

    if (outfile.is_open())
    {
        for(int i=0; i < m_numberInput; i++)
            outfile << m_xDataOut[i] << " " << m_yDataOut[i] << endl;

        outfile.close();
    }
    else cout << "Unable to open file.\n"; 
}

void CFile::Calculate()
{
    m_xDataOut = new double[m_numberInput]; 
    m_yDataOut = new double[m_numberInput];

    for(int i=0; i < m_numberInput; i++)
    {
        m_xDataOut[i] = m_xData[i];
        m_yDataOut[i] = sqrt(m_yData[i]);
    }
}


int main()
{
    CFile file("Input.dat");
    file.ReadFile(); 
    file.Calculate(); 
    file.WriteFile("Output.dat");
    file.~CFile();
}

The error message is as follows:

main(11915,0x7fff77d3d310) malloc: *** error for object 0x7f8a99403940: pointer 
being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
Abort trap: 6

This is code which ironically worked well some weeks ago. I change OS and compilers and now it doesn't anymore. I read about this error in other threads, but couldn't really understand how to use the solutions on my code. The code reads in a data file, does sth. with it and then writes the changed values into another file. Where is the allocation error? Thank you very much in advance for your help! :-)

Answer 1

Your Destructor is called twice. You call it explicitly, and it is also called when exiting main(). You should remove your explicit destrcutor call.

Answer 2

Two problems:

• You don't necessarily initialise all four pointers, in which case it's not safe to apply delete to them. You can fix this by initialising them to null before doing anything; or, better still, replace them with std::vector<double> so you don't have to mess around with delete at all. That will also fix the class's invalid copy semantics (it breaks the Rule of Three) and the potential memory leaks if construction fails.
• You're calling the destructor manually (file.~CFile(), at the end of main). Don't do that: the destructor is called automatically when the program leaves the variable's scope, and it's an error to call it twice.

Answer 3

As @claptrap pointed out your memory managements were also buggy.

1. You should migrate to std::vector<double> rather than raw double arrays and pointers. You can think of vec.resize(N) as a variant of new double[N] which never needs an explicit delete[].

2. If you are on Linux, it's a good practice to run your program under valgrind which automatically traces memomry allocations/deallocations and points out any invalid memory operations. I bet your Linux distro has a pre-compiled package for it.

   • http://valgrind.org/docs/manual/quick-start.html

Answer 4

This here is causing the issue

  delete[] m_xDataOut; 
  delete[] m_yDataOut;    

you have not initialized the pointers in your constructor