##### 3.2.3.3 Some more or less clever ideas

You know the situation. The program is prepared for debugging and in all debugging sessions it runs well. But once it is started without debugging the error shows up. A typical example is a memory leak that becomes visible only when we turn off the debugging. If you foresee such situations you can still win. Simply use something equivalent to the following little program:

         #include <mcheck.h>
         #include <signal.h>

         static void
         enable (int sig)
         {
           mtrace ();
           signal (SIGUSR1, enable);
         }

         static void
         disable (int sig)
         {
           muntrace ();
           signal (SIGUSR2, disable);
         }

         int
         main (int argc, char *argv[])
         {
           ...

           signal (SIGUSR1, enable);
           signal (SIGUSR2, disable);

           ...
         }

I.e., the user can start the memory debugger any time s/he wants if the program was started with `MALLOC_TRACE` set in the environment. The output will of course not show the allocations which happened before the first signal but if there is a memory leak this will show up nevertheless.