“没有分配被释放的指针”

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