Improve company productivity with a Business Account.Sign Up

x
?
Solved

unable to delete Dll memory from an executable

Posted on 2008-06-18
2
Medium Priority
?
244 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 750 total points
ID: 21820235
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
ID: 31468671
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

Free Tool: ZipGrep

ZipGrep is a utility that can list and search zip (.war, .ear, .jar, etc) archives for text patterns, without the need to extract the archive's contents.

One of a set of tools we're offering as a way to say thank you for being a part of the community.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

Go is an acronym of golang, is a programming language developed Google in 2007. Go is a new language that is mostly in the C family, with significant input from Pascal/Modula/Oberon family. Hence Go arisen as low-level language with fast compilation…
Basic understanding on "OO- Object Orientation" is needed for designing a logical solution to solve a problem. Basic OOAD is a prerequisite for a coder to ensure that they follow the basic design of OO. This would help developers to understand the b…
This tutorial covers a step-by-step guide to install VisualVM launcher in eclipse.
The viewer will learn how to synchronize PHP projects with a remote server in NetBeans IDE 8.0 for Windows.

606 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