1  #include <dlfcn.h>
       2  #include <mcheck.h>
       3  #include <stdio.h>
       4  #include <stdlib.h>
       5  
       6  int
       7  main (void)
       8  {
       9    void *h1;
      10    void *h2;
      11    int (*fp) (void);
      12    int *vp;
      13  
      14    mtrace ();
      15  
      16    /* Open the two objects.  */
      17    h1 = dlopen ("reldepmod1.so", RTLD_LAZY | RTLD_GLOBAL);
      18    if (h1 == NULL)
      19      {
      20        printf ("cannot open reldepmod1.so: %s\n", dlerror ());
      21        exit (1);
      22      }
      23    h2 = dlopen ("reldepmod2.so", RTLD_LAZY);
      24    if (h2 == NULL)
      25      {
      26        printf ("cannot open reldepmod2.so: %s\n", dlerror ());
      27        exit (1);
      28      }
      29  
      30    /* Get the address of the variable in reldepmod1.so.  */
      31    vp = dlsym (h1, "some_var");
      32    if (vp == NULL)
      33      {
      34        printf ("cannot get address of \"some_var\": %s\n", dlerror ());
      35        exit (1);
      36      }
      37  
      38    *vp = 42;
      39  
      40    /* Get the function `call_me' in the second object.  This has a
      41       dependency which is resolved by a definition in reldepmod1.so.  */
      42    fp = dlsym (h2, "call_me");
      43    if (fp == NULL)
      44      {
      45        printf ("cannot get address of \"call_me\": %s\n", dlerror ());
      46        exit (1);
      47      }
      48  
      49    /* Call the function.  */
      50    if (fp () != 0)
      51      {
      52        puts ("function \"call_me\" returned wrong result");
      53        exit (1);
      54      }
      55  
      56    /* Now close the first object.  If must still be around since we have
      57       an implicit dependency.  */
      58    if (dlclose (h1) != 0)
      59      {
      60        printf ("closing h1 failed: %s\n", dlerror ());
      61        exit (1);
      62      }
      63  
      64    /* Try calling the function again.  This will fail if the first object
      65       got unloaded.  */
      66    if (fp () != 0)
      67      {
      68        puts ("second call of function \"call_me\" returned wrong result");
      69        exit (1);
      70      }
      71  
      72    /* Now close the second file as well.  */
      73    if (dlclose (h2) != 0)
      74      {
      75        printf ("closing h2 failed: %s\n", dlerror ());
      76        exit (1);
      77      }
      78  
      79    /* Finally, open the first object again.   */
      80    h1 = dlopen ("reldepmod1.so", RTLD_LAZY | RTLD_GLOBAL);
      81    if (h1 == NULL)
      82      {
      83        printf ("cannot open reldepmod1.so the second time: %s\n", dlerror ());
      84        exit (1);
      85      }
      86  
      87    /* And get the variable address again.  */
      88    vp = dlsym (h1, "some_var");
      89    if (vp == NULL)
      90      {
      91        printf ("cannot get address of \"some_var\" the second time: %s\n",
      92  	      dlerror ());
      93        exit (1);
      94      }
      95  
      96    /* The variable now must have its original value.  */
      97    if (*vp != 0)
      98      {
      99        puts ("variable \"some_var\" not reset");
     100        exit (1);
     101      }
     102  
     103    /* Close the first object again, we are done.  */
     104    if (dlclose (h1) != 0)
     105      {
     106        printf ("closing h1 failed: %s\n", dlerror ());
     107        exit (1);
     108      }
     109  
     110    return 0;
     111  }