Valgrind is a software suite that includes many useful tools, like a memory checker and a cache profiler.

Installation

I'm not really sure how to install this on Windows. I've only installed this on my own machine running Ubuntu 9.10. To install, just open a terminal and type:

• sudo apt-get install valgrind and it should do the rest.

I also find KCacheGrind to be a very useful tool for visualizing the output of Callgrind. Installation instructions can be found here, but I also just used apt-get:

• sudo apt-get install kcachegrind.

Memcheck usage

Memcheck is used for checking for memory leaks and memory errors, and is also useful for debugging segmentation faults. Basic usage of memcheck is:

• Compile your code with -g -O0 flags. -g enables debugging mode and allows memcheck to display line numbers. -O0 compiles with no optimizations; higher levels can be used, but you might get false positives. Memcheck recommends using less than level O2.
  • Note: compiling with these flags can be done by setting the CMAKE_CXX_FLAGS and CMAKE_C_FLAGS variables in the main CMakeLists.txt file. Better yet, set a CMAKE_CXX_FLAGS_DEBUG and CMAKE_C_FLAGS_DEBUG and configure using ccmake to use compile a Debug version.
• Run valgrind [program], where [program] is what you would normally type to run your program, including all flags and arguments. This will give you a summary of memory leaks and basic memory errors.
• If you get memory leaks, try running valgrind --leak-check=full [program] to see exactly where leaks are happening. I believe this will make your program run a lot slower, so you may have to sit around and wait for a while. If it's too slow, try compiling with a higher optimization level.

Here's a nice overview of memcheck in general. Section 4.2 will give you a basic description of all the error messages, while section 4.3 will give you more command line options.

Callgrind usage

Callgrind is used for profiling your program. To use:

• Compile code with -g flag.
• Run valgrind --tool=callgrind [program], where [program] is what you would normally type to run your program, including all flags and arguments.
• A file should be generated in your current working directory called callgrind.out.[pid], where [pid] is the pid of the process you just profiled.
• If you have kCacheGrind installed, you should be able to run the file just by double-clicking it, or type in the console: kcachegrind callgrind.out.[pid].
• If everything worked, you should now get a nice GUI view of your program's profile.
  • "Incl." is the time the function/method takes to run + the time all the functions it calls takes to run.
  • "Self" is the time the function/method takes to run excluding all functions it calls.
  • "Called" is the number of times the function was called.