Solved

unable to delete Dll memory from an executable

Posted on 2008-06-18
2
232 Views
Last Modified: 2013-12-14
Hi,
Following is the situation:
I have a dynamic library which has a static method and creates and returns a pointer to the class  object.
I load this library from an executable, call the static method and try deleting the pointer. It complains with the following:
Debug assertion failed.
Expression: _CrtValidHeapPointer(pUserData)

I need to know why is this happening?
Please guide to me any relevant article which might be useful for understanding this topic.

cheers,
tushar.


// Header file for my library : mylib.h
 

#ifndef MYLIB_H

#define MYLIB_H
 

#ifdef MYLIB_EXPORTS

	#define DllExport __declspec(dllexport)

#else

	#define DllExport __declspec(dllimport)

#endif // MYLIB_EXPORTS
 
 

class MyLib

	{

	public:

		DllExport static MyLib* New();

		DllExport ~MyLib();

	private:

		DllExport MyLib();

	};
 
 

//Implementation of mylib.cpp//

DllExport MyLib* MyLib::New()

	{

	MyLib* mylib = new MyLib();

	return mylib;

	}
 

MyLib::MyLib()

	{}
 

MyLib::~MyLib()

	{}
 

// Executable implementation

#include "mylib.h"
 

int main()

{

MyLib* mylib = MyLib::New();

delete mylib; // this delete gives problem

}

Open in new window

0
Comment
Question by:tusharganguli
2 Comments
 
LVL 40

Accepted Solution

by:
evilrix earned 250 total points
Comment Utility
You can only delete heap in the module it was allocated. This is because each module has its own heap. Uf you've allocated the heap in the DLL the DLL should also expose a function to allow pointer to the heap to be pass back in so it can be released.

http://blogs.msdn.com/oldnewthing/archive/2006/09/15/755966.aspx
0
 
LVL 2

Author Closing Comment

by:tusharganguli
Comment Utility
Thanks a lot for the explanation, and apologies for not aceepting this solution earlier, just have lost touch with EE for a long while now :-). Although I did understand the run time concept of memory allocation, but if you could still provide some links for understanding why is there such a discrepancy? what exactly do we mean by runtime being different? is this a phenomena only with windows dll or even linux libraries have these problems?
Would appreciate any further links or recommendation of books, I am eager to know what exactly is happening here.
0

Featured Post

Maximize Your Threat Intelligence Reporting

Reporting is one of the most important and least talked about aspects of a world-class threat intelligence program. Here’s how to do it right.

Join & Write a Comment

Suggested Solutions

C++ Properties One feature missing from standard C++ that you will find in many other Object Oriented Programming languages is something called a Property (http://www.experts-exchange.com/Programming/Languages/CPP/A_3912-Object-Properties-in-C.ht…
Many modern programming languages support the concept of a property -- a class member that combines characteristics of both a data member and a method.  These are sometimes called "smart fields" because you can add logic that is applied automaticall…
The viewer will learn how to use the return statement in functions in C++. The video will also teach the user how to pass data to a function and have the function return data back for further processing.
The viewer will be introduced to the member functions push_back and pop_back of the vector class. The video will teach the difference between the two as well as how to use each one along with its functionality.

763 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

9 Experts available now in Live!

Get 1:1 Help Now