CODEWITHSUNDEEP
c++pointers
nf313743
nf313743

Reputation: 4237

Delete pointer error

I'm confused as to why after I have created a pointer and try to delete it I receive and error message. The following is some condensed code I've been working with:

func()
{
  ptree *resultTree = new ptree;
  resultTree = &getNodeptree(pt);
  delete resultTree;
}

ptree& getNodeptree (ptree &pt)  
{
  BOOST_FOREACH(ptree::value_type &v, pt.get_child("root"))
  {
    ptree &temp = v.second;
    return temp;
  }
}

From my understanding resultTree still needs to be deleted because it's memory is still on the heap. However, trying to do that produces:

*** glibc detected *** /home/nathan/Programming/Project_Code/MyBoostXmlTest/Debug/MyBoostXmlTest: free(): invalid pointer: 0x00000000018347b8 ***

Can someone explain why calling delete produces an error in this instance?

Upvotes: 0

Views: 3291

Answers (2)

juanchopanza
juanchopanza

Reputation: 227548

When you delete resultTree, you are deleting the memory passed to you from the function call to getNodeptree. And you are failing to delete the memory from the explicit call to new.

func()
{
  ptree *resultTree = new ptree; // you will need to delete this one
  resultTree = &getNodeptree(pt); // now it points to something else!
  delete resultTree; // now you delete something you shouldn't
}

Since getNodeptree returns a reference, you really shouldn't be deleting that.

Upvotes: 4

Mark B
Mark B

Reputation: 96301

You do need to delete the memory, but you overwrite the address you allocated when you reassign the pointer in resultTree = &getNodeptree(pt);. I can't understand what's supposed to be happening so I'm afraid I can't offer a suggestion at this time.

Upvotes: 2

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