Memory Leak detection Program without using any tools

I worked for a long time for this article. This program is tested on Sun-Solaris system using gcc compiler.

In market, there are a lot of tools for detecting the memory leaks. Here I made a program which has to include in your source file and it will tell the desired informations to find where memory leaks happen.

There are two files one is findLeak.c and other is findLeak.h . Source file is test.c , this is your program which you want to check memory leaks.

Concept is that when user call library function "malloc or calloc " for allocating dynamic memory, then we have to call our malloc or calloc (In case of my source code 'MyCalloc' function in place of 'calloc' and MyMalloc function in place of 'malloc'). So we have to define malloc to your malloc and in .c file you have to undef malloc and calloc By this way we can call our MyMalloc or MyCalloc function and in this function we will call another function which keeps all info about how much memory allocated. We will do the same for Library function "free" to deallocating memory( In my source file "MyFree" is used in plae of free function).

Now for keeping information, i made a simple singly linked list. which will add info about memory when user call "malloc" or "calloc" function and will also keep information when user call "free" function.

By program you can easily understand.

Heder File : findLeak.h

Code:

#define   uint                 unsigned int 
#define   cchar                const char                     
#define   OutFile             "/home/asadulla/test/MemLeakInfo.txt"   // Just Suppose
#define  MAX_FILENAME_LENGTH   256
#define  calloc(objs, nSize) 	      MyCalloc (objs, nSize, __FILE__, __LINE__)
#define  malloc(nSize) 	    	         MyMalloc (nSize, __FILE__, __LINE__)
#define  free(rMem) 		          MyFree(rMem)

// This structure is keeping info about memory leak

struct InfoMem
{
      //starting address of memory where pointer points 
    void *addr; 
      //Total size of memory in bytes which By malloc 
      //allocates  memory dynamically */
	uint nSize; 
      //Source File Name which you want
      //to  find memory leak information 
	char fileName[MAX_FILENAME_LENGTH]; 
        //Line number of source File due to                                                                             
       // which User forget to deallocate   memory 
	uint lineNumber; 
};
typedef struct InfoMem infoMem;

//This is link list of InfoMem which keeps a List of memory Leak in a source file

struct LeakMem
{
	infoMem memData;     
	struct LeakMem *nxt;   // Next Memory leak Block
};
typedef struct LeakMem leakMem;

// This function is used for writing into file to see the memory leaks summary
void WriteMemLeak(void);

// These two function add information of memory leak information when user 
// calls malloc or calloc
void SubAddMemInfo(void *rMem, uint nSize,  cchar  *file, uint lno);
void SubAdd(infoMem alloc_info);

// These two function remove and deallocated  memory and remove the leak 
//  information when user calls free function
void ResetInfo(uint pos); //erase
void DeleteAll(void); //clear(void);

// This is hidden to user , This function will call when user call malloc function
void *MyMalloc(uint size, cchar *file, uint line);
// This is hidden to user , This function will call when user call calloc function
void *MyCalloc(uint elements, uint size, cchar * file, uint lno);
// This is hidden to user , This function will call when user call free function
void  MyFree(void * mem_ref);

Source File: findLeak.c

Code:

#include	<stdio.h>
#include	<malloc.h>
#include	<string.h>
#include	"findLeak.h"

#undef		malloc
#undef		calloc
#undef 		free


static leakMem * ptr_start = NULL;
static leakMem * ptr_next =  NULL;




// -----------------------------------------------------------
// Name: MyMalloc
// Desc: This is hidden to user. when user call malloc function then 
//       this function will be called.


void *MyMalloc (uint nSize, cchar* file, uint lineNumber)
{
	void * ptr = malloc (nSize);
	if (ptr != NULL) 
	{
		SubAddMemInfo(ptr, nSize, file, lineNumber);
	}
	return ptr;
}

// -----------------------------------------------------------
// Name: MyCalloc
// Desc: This is hidden to user. when user call calloc function then 
//       this function will be called.


void * MyCalloc (uint elements, uint nSize, const char * file, uint lineNumber)
{
	uint tSize;
	void * ptr = calloc(elements , nSize);
	if(ptr != NULL)
	{
		tSize = elements * nSize;
		SubAddMemInfo (ptr, tSize, file, lineNumber);
	}
	return ptr;
}

// -----------------------------------------------------------
// Name: SubAdd
// Desc: It's actually  Adding the Info.


void SubAdd(infoMem alloc_info)
{
	leakMem * mem_leak_info = NULL;
	mem_leak_info = (leakMem *) malloc (sizeof(leakMem));
	mem_leak_info->memData.addr = alloc_info.addr;
	mem_leak_info->memData.nSize = alloc_info.nSize;
	strcpy(mem_leak_info->memData.fileName, alloc_info.fileName); 
	mem_leak_info->memData.lineNumber = alloc_info.lineNumber;
	mem_leak_info->nxt = NULL;

	if (ptr_start == NULL)	
	{
		ptr_start = mem_leak_info;
		ptr_next = ptr_start;
	}
	else {
		ptr_next->nxt = mem_leak_info;
		ptr_next = ptr_next->nxt;				
	}

}



// -----------------------------------------------------------
// Name: ResetInfo
// Desc: It erasing the memory using by List on the basis of info( pos)


void ResetInfo(uint pos)
{

	uint index = 0;
	leakMem * alloc_info, * temp;
	
	if(pos == 0)
	{
		leakMem * temp = ptr_start;
		ptr_start = ptr_start->nxt;
		free(temp);
	}
	else 
	{
		for(index = 0, alloc_info = ptr_start; index < pos; 
			alloc_info = alloc_info->nxt, ++index)
		{
			if(pos == index + 1)
			{
				temp = alloc_info->nxt;
				alloc_info->nxt =  temp->nxt;
				free(temp);
				break;
			}
		}
	}
}

// -----------------------------------------------------------
// Name: DeleteAll
// Desc: It deletes the all elements which resides on List

void DeleteAll()
{
	leakMem * temp = ptr_start;
	leakMem * alloc_info = ptr_start;

	while(alloc_info != NULL) 
	{
		alloc_info = alloc_info->nxt;
		free(temp);
		temp = alloc_info;
	}
}


// -----------------------------------------------------------
// Name: MyFree
// Desc: 


void MyFree(void * mem_ref)
{
		uint loop;
   // if the allocated memory info is part of the list, removes it
	leakMem  *leak_info = ptr_start;
	/* check if allocate memory is in our list */
	for(loop = 0; leak_info != NULL; ++loop, leak_info = leak_info->nxt)
	{
		if ( leak_info->memData.addr == mem_ref )
		{
			ResetInfo(loop);
			break;
		}
	}
	free(mem_ref);
}


// -----------------------------------------------------------
// Name: SubAddMemInfo
// Desc: it also fill the the Info


void SubAddMemInfo (void * mem_ref, uint nSize, cchar * file, uint lineNumber)
{
	infoMem AllocInfo;

	/* fill up the structure with all info */
	memset( &AllocInfo, 0, sizeof ( AllocInfo ) );
	AllocInfo.addr 	= mem_ref;
	AllocInfo.nSize = nSize;
	strncpy(AllocInfo.fileName, file, MAX_FILENAME_LENGTH);
	AllocInfo.lineNumber = lineNumber;
	
	/* SubAdd the above info to a list */
	SubAdd(AllocInfo);
}

// -----------------------------------------------------------
// Name: WriteMemLeak
// Desc: It writes information about Memory leaks in a file 
//       Example: File is as : "/home/asadulla/test/MemLeakInfo.txt"



void WriteMemLeak(void)
{
	uint index;
	leakMem *leak_info;

	FILE * fp_write = fopen(OutFile, "wt");
	char info[1024];

	if(fp_write != NULL)
	{
		sprintf(info, "%s\n", "SUMMARY ABOUT MEMORY LEAKS OF YOUR SOURCE FILE ");
		fwrite(info, (strlen(info) + 1) , 1, fp_write);
		sprintf(info, "%s\n", "-----------------------------------");	
		fwrite(info, (strlen(info) + 1) , 1, fp_write);
		
		for(leak_info = ptr_start; leak_info != NULL; leak_info = leak_info->nxt)
		{

			sprintf(info, "Name of your Source File                 : %s\n", leak_info->memData.fileName);
			fwrite(info, (strlen(info) + 1) , 1, fp_write);

			sprintf(info, "Starting Address                         : %d\n", leak_info->memData.addr);
			fwrite(info, (strlen(info) + 1) , 1, fp_write);

			sprintf(info, " Total size Of memory Leak               : %d bytes\n", leak_info->memData.nSize);			
			fwrite(info, (strlen(info) + 1) , 1, fp_write);

			sprintf(info, "Line Number for which no DeAllocation    : %d\n", leak_info->memData.lineNumber);
			fwrite(info, (strlen(info) + 1) , 1, fp_write);

			sprintf(info, "%s\n", "-----------------------------------");	
			fwrite(info, (strlen(info) + 1) , 1, fp_write);
      fwrite(info, (strlen(info) + 1) , 1, fp_write);
		}
	}	
	DeleteAll();
}

These two files (header file and source file) user has to include in his source file to which user want to find memory leak.

Source File for detecting memory leak is as Here you can gice your own source file and in this source file you have write onle line to include file #include"findLeak.h"


Source File : test.c

Code:

#include<malloc.h>
#include"findLeak.h"

int main()
{
	int *p1 = (int *)malloc(10);  
	int *p2 = (int *)calloc(10, sizeof(int));
    char *p3 = (char *) calloc(15, sizeof(float));
    float *p4 = (float*) malloc(16);
	free(p2);
    WriteMemLeak();
	return 0;
 }

Now user can compile these programmes in a console as :
> g++ test.c findLeak.c
and give a command for run
> ./a.out

then go to you your directory where you have defined a macro "OutFile" and open this defined file and you can see the results.

Output of above source file is as:

Code:

SUMMARY ABOUT MEMORY LEAKS OF YOUR SOURCE FILE 
-----------------------------------
Name of your Source File                 : test.c
Starting Address                         : 184960
 Total size Of memory Leak               : 10 bytes
Line Number for which no DeAllocation    : 7
-----------------------------------
-----------------------------------
Name of your Source File                 : test.c
Starting Address                         : 187104
 Total size Of memory Leak               : 60 bytes
Line Number for which no DeAllocation    : 9
-----------------------------------
-----------------------------------
Name of your Source File                 : test.c
Starting Address                         : 184984
 Total size Of memory Leak               : 16 bytes
Line Number for which no DeAllocation    : 10
-----------------------------------
-----------------------------------

Now you can try to make you own source file just like test.c.

 

Really i hard work for it. I request to all, Just read it then you can have basic idea of PURIFY.

 

Strange!!! Really nice way to detect memory leak in an application.

 

just wana ask what type og programing language should i use for that sample program?

 

u can use "C or C++"

 

great i got some idea bout using c++ but what i wanna know also is what does this memory leak is? does it have something to do would system errors? or slow file retrieval?

 

you can read detail from somewhere about memory leak...

Memory leak occurs in your program when you are allocating memory dynamically(this memory is allocated on heap by operating system when you are calling malloc or calloc in C) and you forget to deallocate that memory. Now this memory will be called as "memory leak" .
Example:

int main()
{
int *p1 = (int *)malloc(10);
}
If your program will go out of scope of integer pointer p1 then memory allocated by pointer p1 will be leak. because you did'nt call free(p1) function.

 

You can search on google. Memory leaks related things you can get anywhere. You are asking very basic question.

 

can you please give me some more details about memory leak

 

suppose there is a function which allocates memory for a temporary variable temp , does some work and then returns temp.

i think there should be a memory leak in this case as i cannot free temp ,right so how can i control memory leak here

 

I think this example will solved your problem.

Code:

#include<malloc.h>

int* fun();
int main()
{
  int *p2 = fun();
  free(p2);
   return 0;
 }

int* fun()
{
  int *p1 = (int *)malloc(10);
  return p1;
}

 

to check memory leak, you can use my program as

Code:

#include<malloc.h>
#include "findLeak.h"


int* fun();
int main()
{
  int *p2 = fun();
  free(p2);
  WriteMemLeak();
  return 0;
 }

int* fun()
{
  int *p1 = (int *)malloc(10);
  return p1;

}

 

that means you want to say that i need to free the memory in the function where i m receiving the value returned by temporary variable.

 

understood and clear

 

I run this program for my application. It's working. Too Cooooooooool.
Thanks asadullah.ansari

 

Excellent asadullah.ansari. I cannt imagine. I am very happy to see this memory leak detector program so simple and understandable.

 

Can you tell me in different languages how to use this program?

 

suppose ive detected memory leaks on my OS as I run that program, what will I do next?
Is there any posible ways to prevent it or get rid of it?

 

You can make my program in binary also.

Beauty of this program is that only one interface you have to use, that is "WriteMemLeak()" only.
If any way other languages support to use C Interface, then you can use it.

 

I am not getting your question.

Is it true what i am understanding that "memory leak is in OS not in your program".
If it is true then your question is
"How to detect memory leak coming in OS by program posted by asadullah.ansari? "

Response me?