Using the Memory Debugger (The GNU C Library)

#### 3.2.4.2 Example program excerpts ¶

Even though the tracing functionality does not influence the runtime behavior of the program it is not a good idea to call `mtrace` in all programs. Just imagine that you debug a program using `mtrace` and all other programs used in the debugging session also trace their `malloc` calls. The output file would be the same for all programs and thus is unusable. Therefore one should call `mtrace` only if compiled for debugging. A program could therefore start like this:

    #include <mcheck.h>

    int
    main (int argc, char *argv[])
    {
    #ifdef DEBUGGING
      mtrace ();
    #endif
      ...
    }

This is all that is needed if you want to trace the calls during the whole runtime of the program. Alternatively you can stop the tracing at any time with a call to `muntrace`. It is even possible to restart the tracing again with a new call to `mtrace`. But this can cause unreliable results since there may be calls of the functions which are not called. Please note that not only the application uses the traced functions, also libraries (including the C library itself) use these functions.

This last point is also why it is not a good idea to call `muntrace` before the program terminates. The libraries are informed about the termination of the program only after the program returns from `main` or calls `exit` and so cannot free the memory they use before this time.

So the best thing one can do is to call `mtrace` as the very first function in the program and never call `muntrace`. So the program traces almost all uses of the `malloc` functions (except those calls which are executed by constructors of the program or used libraries).