Memory debug tools

However, as already mentioned, the tool requires you to use a source-code debugger like GDB. Developer: Valgrind Developers Reviewed version: 3. Valgrind is a suite that provides several tools for debugging and profiling Linux programs.

The most popular Valgrind tool is Memcheck, a memory-error detector that can detect issues such as memory leaks, invalid memory access, uses of undefined values and problems related to allocation and deallocation of heap memory. This release of the suite 3. In addition, it also "backports fixes for all reported missing AArch64 ARMv8 instructions and syscalls from the trunk.

Memcheck, like all other Valgrind tools, is basically a command line utility. Note: You don't need to mention Memcheck anywhere in the command line because it's the default Valgrind tool. However, you do need to initially compile your program with the -g option -- which adds debugging information -- so that Memcheck's error messages include exact line numbers.

What I really like about Memcheck is that it provides a lot of command line options such as the --leak-check option mentioned above , allowing you to not only control how the tool works but also how it produces the output. For example, you can enable the --track-origins option to see information on the sources of uninitialized data in your program.

Enabling the --show-mismatched-frees option will let Memcheck match the memory allocation and deallocation techniques. If a mismatch is detected, an error is reported. But the best part, especially for beginners, is that the tool even produces suggestions about which command line option the user should use to make the output more meaningful.

Another useful feature of Memcheck is that it lets you create suppression files , allowing you to suppress certain errors that you can't fix at the moment -- this way you won't be reminded of them every time the tool is run.

It's worth mentioning that there already exists a default suppression file that Memcheck reads to suppress errors in the system libraries, such as the C library, that come pre-installed with your OS. For those seeking advanced functionality, it's worth knowing that Memcheck can also detect memory errors in programs that use custom memory allocators. In addition, it also provides monitor commands that can be used while working with Valgrind's built-in gdbserver, as well as a client request mechanism that allows you not only to tell the tool facts about the behavior of your program, but make queries as well.

While there's no denying that Memcheck can save you a lot of debugging time and frustration, the tool uses a lot of memory, and so can make your program execution significantly slower around 20 to 30 times, according to the documentation. Aside from this, there are some other limitations, too. We welcome contributions to Dr. We use the same code review and workflow as for DynamoRIO. Downloading Dr. Memory Dr. Memory Performance Dr.

If dbg is a Debugger instance, and dbg. You can retrieve the current log by calling dbg. It produces a count of those items, broken down by various criteria. If dbg is a Debugger instance, you can call dbg.

Memory instance, which inherits the following accessor properties from its prototype:. A boolean value indicating whether this Debugger. Memory instance is capturing the JavaScript execution stack when each Object is allocated.

This accessor property has both a getter and setter: assigning to it enables or disables the allocation site tracking. Reading the accessor produces true if the Debugger is capturing stacks for Object allocations, and false otherwise.

Allocation site tracking is initially disabled in a new Debugger. Assignment is fallible: if the Debugger cannot track allocation sites, it throws an Error instance. You can retrieve the allocation site for a given object with the Debugger. A number between 0 and 1 that indicates the probability with which each new allocation should be entered into the allocations log.

Memory inherits accessor properties that store handler functions for SpiderMonkey to call when given events occur in debuggee code. The handler functions receive the Debugger. Memory hooks. On a new Debugger. Use this command to clear the GFlag settings once you are done. For more information, see GFlags Commands. By default, the amount of stack trace data that Windows gathers is limited to 32 MB on an x86 processor, and 64 MB on an x64 processor. If you must increase the size of this database, choose the Image File tab in the GFlags graphical interface, type the process name, press the TAB key, check the Stack Backtrace Megs check box, type a value in MB in the associated text box, and then select Apply.

Increase this database only when necessary, because it may deplete limited Windows resources. When you no longer need the larger size, return this setting to its original value. If you changed any flags on the System Registry tab, you must restart Windows to make these changes effective. If you changed any flags on the Image File tab, you must restart the process to make the changes effective.

Changes to the Kernel Flags tab are effective immediately, but they are lost the next time Windows restarts. Before using UMDH, you must have access to the proper symbols for your application. Set this variable equal to a path containing the symbols for your application. If you also include a path to Windows symbols, the analysis may be more complete. The syntax for this symbol path is the same as that used by the debugger; for details, see Symbol Path.

In addition, to assure accurate results, you must disable BSTR caching.