How to make sure compiler doesn't optimize out pointer variable assigned with main 'c' function?

Consider Hello World program modified to illustrate embedded system Virtual Memory concepts:

#include <stdio.h>

   int bss_var;       /* uninitialized global variable */
   int data_var = 1;  /* initialized global variable */
   
   int main( int argc, char ** argv)
   {
      void *stack_var;    /* Local variable on the stack */
	  
	  stack_var = (void *)main;  /* Don't let the compiler optimize it out */
	  
	  printf("Hello, World! Main is executing at %p\n", stack_var);
	  printf("This address (%p) is in our stack frame\n", &stack_var);
	  
	  /* bss section contains uninitialized data */
	  printf("This address (%p) is in our bss section\n", %bss_var);
	  
	  /* data section contains initialized data */
	  printf("This address (%p) is in our data section\n", &data_var);
	  
	  return 0;
	  
   }

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This program is created in BeagleBoard-xM running some Linux distribution.  This Linux distribution has vi editor and gcc compiler in it.
The line in the above program, "Don't let the compiler optimize it out", how do I make sure compiler doesn't optimize this line of code.  Do I need to compile
with some compiler option?