1  #include <sys/types.h>
       2  #include <dlfcn.h>
       3  #include <error.h>
       4  #include <mcheck.h>
       5  #include <stdlib.h>
       6  #include <unistd.h>
       7  
       8  pid_t pid, pid2;
       9  
      10  pid_t getpid(void)
      11  {
      12    pid_t (*f)(void);
      13    f = (pid_t (*)(void)) dlsym (RTLD_NEXT, "getpid");
      14    if (f == NULL)
      15      error (EXIT_FAILURE, 0, "dlsym (RTLD_NEXT, \"getpid\"): %s", dlerror ());
      16    return (pid2 = f()) + 26;
      17  }
      18  
      19  int
      20  main (void)
      21  {
      22    pid_t (*f)(void);
      23  
      24    mtrace ();
      25  
      26    f = (pid_t (*)(void)) dlsym (RTLD_DEFAULT, "getpid");
      27    if (f == NULL)
      28      error (EXIT_FAILURE, 0, "dlsym (RTLD_DEFAULT, \"getpid\"): %s", dlerror ());
      29    pid = f();
      30    if (pid != pid2 + 26)
      31      error (EXIT_FAILURE, 0, "main getpid() not called");
      32    return 0;
      33  }