3.2.4.3 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.