1  #include <stdio.h>
       2  
       3  void sub0(void);
       4  void c_sub0(void (*sub)(void));
       5  void c_sub1(int (*func)(int));
       6  
       7  extern void abort(void);
       8  
       9  int main(int argc, char **argv)
      10  {
      11    printf("hello from C main\n");
      12    
      13    sub0();
      14    return 0;
      15  }
      16  
      17  void c_sub0(void (*sub)(void))
      18  {
      19    printf("hello from c_sub0\n");
      20    sub();
      21    
      22    return;
      23  }
      24  
      25  void c_sub1(int (*func)(int))
      26  {
      27    int retval;
      28    
      29    printf("hello from c_sub1\n");
      30  
      31    retval = func(10);
      32    if(retval != 10)
      33    {
      34      fprintf(stderr, "Fortran function did not return expected value!\n");
      35      abort();
      36    }
      37  
      38    return;
      39  }