ZeroMQ

Detecting Memory Leaks

Any long-running application has to manage memory correctly, or eventually it’ll use up all available memory and crash. If you use a language that handles this automatically for you, congratulations. If you program in C or C++ or any other language where you’re responsible for memory management, here’s a short tutorial on using valgrind, which, among other things, will report on any leaks your programs have:

• To install valgrind, such as on Ubuntu or Debian, issue:

sudo apt-get install valgrind

• By default, ØMQ will cause valgrind to complain a lot. To remove these warnings, create a file called valgrind.supp that contains this:

{
   <socketcall_sendto>
   Memcheck:Param
   socketcall.sendto(msg)
   fun:send
   ...
}
{
   <socketcall_sendto>
   Memcheck:Param
   socketcall.send(msg)
   fun:send
   ...
}

• Fix your applications to exit cleanly after Ctrl-C. For any application that exits by itself, that’s not needed, but for long-running applications, this is essential. Otherwise, valgrind will complain about all currently allocated memory.

• Build your application with -DDEBUG, if it’s not your default setting. That ensures valgrind can tell you exactly where memory is being leaked.

• Finally, run valgrind as follows (all on one line)

valgrind --tool=memcheck --leak-check=full --suppressions=valgrind.supp 
                                  someprog

After fixing any errors it reports, you should get the pleasant message:

==30536== ERROR SUMMARY: 0 errors from 0 contexts...