Memory Leak Detection in C++

Don't put off fixing memory leaks. Make one or more of these convenient tools a part of your development process.

An earlier article [“Memory Leak Detection in Embedded Systems”, LJ, September 2002, available at www.linuxjournal.com/article/6059] discussed the detection of memory leaks when using C as the programming language. This article discusses the problem of detecting memory leaks in C++ programs. The tools discussed here detect application program errors, not kernel memory leaks. All of these tools have been used with the MontaVista Linux Professional Edition 2.1 and 3.0 products, and one of them, dmalloc, ships with MontaVista Linux.

When developing application programs for embedded systems, designers and programmers must take great care with using system memory resources. Unlike workstations, embedded systems have a finite memory source. Typically, no swap area is available to idle programs. When the system uses up all of its resources, nothing is left to do but panic and start over or kill some programs to make room for the needed resources. Therefore, it is important to write programs that do not leak memory. Many tools aid programmers in finding these resource leaks. All of the tools discussed here come with their own test programs.

One method of testing, which I have seen used successfully by application developers, involves using a workstation to develop prototype code and debugging as much as possible on it. Using memory leak tools in this manner is strongly advised. By debugging on a workstation, the application programmer can be assured that the transition to the target processor will be easier. A major reason for using workstations is they are cheap, and everybody involved has one. Targets, on the other hand, are usually few and in great demand.

Most memory leak detection programs are available as full source. They typically have been built on an x86-based platform. Running them on non-x86 targets requires some porting. This porting effort could be as simple as a recompile, link and run, or it could require changing some assembler code from one platform to another. Some of the tools come with hints and suggestions for use in cross-compiling environments.

dmalloc

The author of dmalloc, a tool I covered in detail in the September 2002 article, states that his knowledge of C++ is limited, and thus the C++ detection of memory leaks also is limited. In order to use dmalloc with C++ and threads, it has been necessary to link the application as static.

ccmalloc

The ccmalloc tool is a memory profiler with a simple usage model that supports dynamically linked libraries but not dlopen. It detects memory leaks, multiple de-allocation of the same data, underwrites and overwrites and writes to already de-allocated data. It displays allocation and de-allocation statistics. It is applicable to optimized and stripped code and supports C++. It also provides file and line number information for the whole call chain, not only for the immediate caller of malloc/free, and it supports C++. No recompilation is needed to use ccmalloc; simply link it with -lccmalloc -ldl or ccmalloc.o -ldl. ccmalloc provides efficient representation of call chains, customizable printing of call chains, selective printing of call chains, a compressed log file and a startup file called .ccmalloc. The major documentation is found in a file named ccmalloc.cfg. The test files included with the program provide more documentation. nm and gdb are required to get information about symbols and gzip or to compress log files.

NJAMD

NJAMD is, as the author states, “not just another malloc debugger”. As with most memory allocation debuggers, the standard allocation functions are replaced with new ones that perform various checks as memory is used. Specifically, it looks for dynamic buffer over/underflows and detects memory reuse after it is freed. The library built for NJAMD can be LD_PRELOADed, or it can be linked to the program. It creates a large memory buffer on the first memory allocation, 20MB, and it then carves this up as the program needs memory.

NJAMD can be used alone, with a front end or from within gdb. It has a utility that allows postmortem heap analysis. Another feature allows the application being debugged to skip recompilation; simply preload the library. NJAMD also is capable of tracing leaks in library functions that wrap malloc and free, GUI widget allocators and C++ new and delete. Often a memory leak is not discovered immediately but lurks, waiting to strike at the most visible moment. Tracking this down can take a long time. NJAMD has many environment variables that allow setting varying levels of detection. As with most debugging tools, performance can be an issue with NJAMD, so the tool should be used only during development. Deploying with the tool enabled can result in slower systems.

______________________

Comments

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

The easiest way to prevent

Rammstein's picture

The easiest way to prevent memory leaks is to use ready utils, like Deleaker ( http://deleaker.com/ )

Detecting Memory leak in Visual Studio (Debug mode)

Anonymous's picture

The memory leak information is printed on "Output" window.
[ This advantage is in "Debug" mode only. ]
Example

int _tmain()
{
int* ptr = NULL;

ptr = (int*)malloc(sizeof(int)*20);

for( int i=0; i<20; ++i )
ptr[i] = i;

#ifndef NDEBUG

int flag = _CrtSetDbgFlag(_CRTDBG_REPORT_FLAG); // Get current flag

flag |= _CRTDBG_LEAK_CHECK_DF; // Turn on leak-checking bit

_CrtSetDbgFlag(flag); // Set flag to the new value

#endif

//free(ptr);

printf("\n\nPress Enter...");
getch();
return 0;
}

http://www.mindfiresolutions.com/Detecting-Memory-leak-in-Visual-Studio-...

INSOMNIA :Coding contest

Anonymous's picture

IIT ROORKEE presents INSOMNIA:THE MIDNIGHT PROGRAMMING CONTEST...
www.insomnia.cognizance.org.in
Starts on : 27th March, 9:00 PM

Cash prizes worth Rs.30,000 on stake for 3rd round.

is there are any tools to prevent the memory leaks

newbie's picture

I want to know is any tool for detect the memory leaks which for windows platform and it is able to include in the some other tools (we program are excuted...)

The best one is

Bill Gates's picture

The best one is Deleaker!
Deleaker is a run-time error detection and debugging tool for Visual C++ developers. Deleaker is a really useful add-in for Visual Studio that helps you to analyze programming errors, many of which are unique to Visual C++. With Deleaker you can detect and localize resource leaks such as memory, GDI and USER objects, handles.
http://deleaker.com

all thos tools sucks

Anonymous's picture

the best way to discover memory leaks:
hard core debugging

one more tool for debugging memory leaks-Coverity Prevent

victor louis's picture

You can prevent memory leaks by watching for some common problems. Collection classes, such as hash tables and vectors, are common places to find the cause of a memory leak. This is particularly true if the class has been declared static and exists for the life of the application. . The prevalence of memory leak bugs has led to the development of a number of debugging tools to detect unreachable memory. Coverity Prevent is one of the tool that you can use for fixing these kinds of bugs. Coverity Prevent is also used by the Department of Homeland security to scan many open source projects. You can get more info at http://www.Coverity.com

Webinar
One Click, Universal Protection: Implementing Centralized Security Policies on Linux Systems

As Linux continues to play an ever increasing role in corporate data centers and institutions, ensuring the integrity and protection of these systems must be a priority. With 60% of the world's websites and an increasing share of organization's mission-critical workloads running on Linux, failing to stop malware and other advanced threats on Linux can increasingly impact an organization's reputation and bottom line.

Learn More

Sponsored by Bit9

Webinar
Linux Backup and Recovery Webinar

Most companies incorporate backup procedures for critical data, which can be restored quickly if a loss occurs. However, fewer companies are prepared for catastrophic system failures, in which they lose all data, the entire operating system, applications, settings, patches and more, reducing their system(s) to “bare metal.” After all, before data can be restored to a system, there must be a system to restore it to.

In this one hour webinar, learn how to enhance your existing backup strategies for better disaster recovery preparedness using Storix System Backup Administrator (SBAdmin), a highly flexible bare-metal recovery solution for UNIX and Linux systems.

Learn More

Sponsored by Storix