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03/08/2006 at 07:08PM PST, ID: 21766511
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8.6

double free or corruption

Asked by chsalvia in C++ Programming Language

Tags: free, double, corruption

I'm getting this error at runtime:

*** glibc detected *** double free or corruption (fasttop): 0x0804a008 ***
Aborted

This happens when an instance of one class encapsulates and assigns an instance of another class.

I tried to narrow down the problem using a debugger, and it seems the error is produced because somehow I call delete[] on an already deleted pointer in the class destructor.  At least, I think that's the problem - but I'm not sure HOW that's happening.  I was finally able to create a very simplified test program that reproduces the exact problem so I could post it here without posting hundreds of lines of code.  Here it is:

// BEGIN CODE

class Buffer
{
      char* buffer;
      int len;

      void init(char* str)
      {
            len = strlen(str);
            buffer = new char[len+1];
            memcpy(buffer,str,len);
      }

      public:
            Buffer(char* str)      { init(str); }

            ~Buffer() { delete[] buffer; } // <--- this destructor is causing the problem, but why?
      
};

class Class2
{
       Buffer buf;

      public:
            Class2(Buffer& buffer) : buf(buffer) { }
            ~Class2() { };
};

int main()
{
      Buffer buf = "abcdefghijklmnopqrstuvwxyz";
      Class2 c2(buf);
}

// END CODE
[+][-]03/08/06 07:24 PM, ID: 16141206

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[+][-]03/08/06 07:27 PM, ID: 16141218

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[+][-]03/08/06 07:28 PM, ID: 16141220

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[+][-]03/08/06 07:29 PM, ID: 16141227

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[+][-]03/08/06 07:30 PM, ID: 16141232

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[+][-]03/08/06 07:30 PM, ID: 16141235

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[+][-]03/08/06 07:32 PM, ID: 16141244

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About this solution

Zone: C++ Programming Language
Tags: free, double, corruption
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Solution Provided By: rajeev_devin
Participating Experts: 4
Solution Grade: A
 
 
 
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