Insert Function before and after main function

Source code:

   1: #include<stdio.h>

   2: void myStartupFun (void) __attribute__ ((constructor));

   3: void myCleanupFun (void) __attribute__ ((destructor));

   4:   

   5: /* implementation of myStartupFun */

   6: void myStartupFun (void)

   7: {

   8:     printf ("startup code before main()\n");

   9: }

  10:  

  11: /* implementation of myCleanupFun */

  12: void myCleanupFun (void)

  13: {

  14:     printf ("cleanup code after main()\n");

  15: }

  16:  

  17: int main (void)

  18: {

  19:     printf ("hello\n");

  20:     return 0;

  21: }

 

Just compile the source code, and run, you will find the interesting result.