The prevalence of memory leak bugs has led to the development of a number of debugging tools to detect unreachable memory. Plumbr is a popular memory leak detection tool for. Rational Purify or other memory leak tool for C#. I used to develop C++ and used Rational Purify for memory leak. If not, do I have to use its memory profiler to detect memory leaks? Wednesday, November 21. Even if you use some specific tools like Purify, these tools will report you a lot of suspicious data. Usualy the memory leaks messages are a good way to do this debug because when you have no message. Buy a IBM Rational Purify for Windows - Software Subscription and Support Renewal or other Developer Tools Software at CDW.com. Performance:Leak Tools. Jump to: navigation, search. This documentation has moved to MDN. What links here; Related changes; Special pages; Printable version; Permanent link; Page information. Visual Leak Detector - Enhanced Memory Leak Detection for Visual C++Table of Contents. Introduction. Visual C++ provides built- in memory leak detection, but its capabilities are minimal at best. This memory leak detector was created as a free alternative to the built- in memory leak detector provided with Visual C++. Here are some of Visual Leak Detector's features, none of which exist in the built- in detector: Provides a complete stack trace for each leaked block, including source file and line number information when available. Other after- market leak detectors for Visual C++ are already available. But most of the really popular ones, like Purify and Bounds. Checker, are very expensive. A few free alternatives exist, but they're often too intrusive, restrictive, or unreliable. Purify: Fast Detection of Memory Leaks and Access Errors This paper describes Purify, a software testing and quality assurance tool that detects memory leaks and access errors. Purify inserts additional checking instructions. Tool Mentors > Rational Purify Tool Mentors > Detecting Run-Time Errors Using Rational Purify and Rational PurifyPlus (UNIX). Purify reports memory leaks. Purify opens your source code in your. Here are some key advantages that Visual Leak Detector has over many other free alternatives: Visual Leak Detector is cleanly packaged as an easy- to- use library. You don't need to compile its source code to use it. And you only need to make minor additions to your own source code to integrate it with your program. Visual Leak Detector is licensed free of charge as a service to the Windows developer community. What's New? 1. 4 November 2. A new beta version has been posted. This version fixes a few bugs, most notably a deadlock bug and a couple of failed assertion bugs that were identified in the 1. Note that the beta version does not have the same limitations of the 1. Whereas 1. 0 can only detect leaks resulting from new or malloc, the beta can detect many different classes of leaks. Please also note that the article below describes the inner workings of the 1. Because the beta version might change significantly before the next official release, the article will not be updated to reflect the design of the beta version until the official release is complete. Using Visual Leak Detector. This section briefly describes the basics of using Visual Leak Detector (VLD). For a more in- depth discussion of the configuration options, runtime APIs, and a discussion of the more advanced usage scenarios (such as using VLD with DLLs), please see the full documentation included in the downloadable Zip files. To use VLD with your project, follow these simple steps: Copy the VLD library (*. Visual C++ installation's . It's best, but not absolutely required, to include this header before any other header files, except for stdafx. If the source file, include stdafx. VLD will detect memory leaks in your program whenever you run the debug version under the Visual C++ debugger. A report of all the memory leaks detected will be displayed in the debugger's output window when your program exits. Double- clicking on a source file's line number in the memory leak report will take you to that file and line in the editor window, allowing easy navigation of the code path leading up to the allocation that resulted in a memory leak. Note: When you build release versions of your program, VLD will not be linked into the executable. So it is safe to leave vld. Doing so will not result in any performance degradation or any other undesirable overhead. Making a Memory Leak Detector. The goal of Visual Leak Detector was to build a better replacement for the memory leak detector built- in to Visual C++. With that in mind, I set out to use the same method used by the built- in detector, namely the CRT Debug Heap. But this new detector would provide enhancements - - primarily full stack traces, which can be extremely helpful for finding and fixing leaks. The Built- In Detector. The built- in detector is pretty simple really. When a program is exiting, the CRT runs a bunch of cleanup code after main returns. If the built- in detector is enabled, then it runs a memory leak check as part of the cleanup procedure. The memory leak check simply looks at the debug heap: if there are any user blocks still allocated on the debug heap, then they must be memory leaks. The debug version of malloc stores the file and line number that allocated each block in the block's header at the time it is allocated. When the built- in detector identifies a memory leak, it simply peers inside the block header to get the file and line number. It then reports that information to the debugger where it is displayed. Note that the built- in detector detects leaks without doing any monitoring of allocations or frees. It simply takes a snapshot of the heap just before the process terminates and determines if there are any leaks based on that snapshot. A snapshot of the heap only tells us if there are leaks; it does not tell us how they were leaked. Clearly, to determine the . But to obtain a stack trace, we need to be able to monitor every allocation on- the- fly at runtime. This is what will distinguish our leak detector from the built- in one. Allocation Hooking. Luckily for us, Microsoft has provided an easy way to monitor every allocation made from the debug heap: allocation hooks. An allocation hook is simply a user- supplied callback function that will be called just before each allocation is made from the debug heap. Microsoft has provided a function, . When the debug heap calls the allocation hook, one of the arguments passed is an ID number that uniquely identifies each allocation - - it's basically a serial number for each memory block allocated. There's not enough room in the memory block header for us to record any information directly in it, but we can use this unique ID number as a key to map each block to any data that we want to record. Walking the Stack. Now that we have a way to be notified every time a block is allocated, as well as a way to uniquely identify each allocation, all that's left to do is to record the call stack each time an allocation occurs. We could conceivably attempt to unwind the stack ourselves using inline assembly. But stack frames can be organized in different ways, depending on compiler optimizations and calling conventions, so it could become complicated to do it that way. Once again, Microsoft has provided us with a tool to help us out. This time it is a function that we can call iteratively to walk the stack, frame by frame. That function is Stack. Walk. 64. It is part of the Debug Help Library (dbghelp. As long as we provide it with the information that it needs to establish a starting . Each time Stack. Walk. STACKFRAME6. 4 structure that can be reused as input for the next call to Stack. Walk. 64. It can be repeatedly called this way until the end of the stack is reached. Initializing the Memory Leak Detector. We now have the beginnings of a better memory leak detector. We can monitor every allocation, and for each allocation monitored, we can obtain and record a stack trace. The only challenge that remains is to ensure that the allocation hook function is registered with the debug heap as soon as the program starts executing. This can be very simply solved by creating a global instance of a C++ class object. The constructor will run when the program is initialized. From the constructor, we can call . But wait, what if the program we are debugging already has other global C++ class objects that allocate memory? How can we ensure that our constructor will be called first, and that our allocation hook function will be installed before any other global objects are constructed? Unfortunately, the C++ specification does not spell out any rules for deciding in which order to construct global objects. So there are no absolute guarantees that our constructor will be called first. But we can come very close to guaranteeing it. We can leverage a compiler- specific preprocessor directive that explicitly tells the compiler to ensure that our global variable is constructed as soon as possible: #pragma init. This directive tells the compiler to place our global object in the . Objects in this segment are the first to be constructed. Next, objects in the . Generally speaking, no normal user objects should ever be placed in the . We can then examine the heap, just like the built- in detector does. If we find a block on the heap that has not been freed, it is a leak and we can look up its call stack using the unique ID number recorded by our allocation hook function. An STL map would work fine here for mapping the ID number to the call stacks. I didn't use an STL map because I wanted my library to be compatible with both new and old versions of Visual C++. The STL from older versions is incompatible with the newer versions, so I couldn't use STL components. But the good news is that this gave me the opportunity to create a data structure similar in concept to the STL map, but with specific optimizations for use with my memory leak detector. Do you remember that the built- in leak detector peers inside the memory block to get the name of the file and the line number where the block was allocated? Well, all we have for our call stack is a bunch of program addresses. Dumping all those hex numbers to the debugger wouldn't be of much use. To make those addresses more meaningful, we need to translate them to human readable information: files and line numbers (and function names too). Once again, Microsoft comes through with the tools that will help us do our job: the symbol handler APIs. Like Stack. Walk. Debug Help Library. I won't dwell on them in detail here, because there are a lot of them and they're pretty simple to use. They don't require as much ingenuity to use as Stack. Walk. 64 does. We can use two of the symbol handler APIs to get the filenames, line numbers, and function names that we want. The aptly named Sym. Get. Line. From. Addr. Its sister API, Sym. From. Addr translates addresses into symbol names. For program addresses, which are what we have, the corresponding symbol name will be the name of the function containing that program address. Key Parts of the Source Code. In case you got bored with the above section and skipped ahead, I'll summarize it here. In a nutshell, this memory leak detector works like this: A global object is automatically constructed.
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