Using the Stack to pass parameters

• visual depiction of run-time storage

• heap
  • freelist - list of free space
  • on allocation - memory manager finds space and marks it as used changing freelist
  • on deallocation - memory manager marks space as free changing freelist
  • memory fragmentation - memory fragments into small blocks over lifetime of program
  • garbage collection - coalesce fragments, possibly moving objects (must be careful of pointers when moving!)
• stack
  • clean and efficient support for nested functions and recursion
  • central concept is stack frame (also called activation record), includes
    • visual depiction of frame
    • parameters
    • return address - where to begin execution when function exits
    • dynamic link - pointer to caller's stack frame
    • static link - pointer to lexical parent (for nested functions)
    • return value - where to put the return value
    • local variables
    • local work space - for temporary storage of results
  • function call - push stack frame
  • function exit - pop stack frame
  • visual depiction of stack calls
  
• example

  int x;                 /* static storage */
  
  void main() {
     int y;              /* dynamic stack storage */
     char *str;          /* dynamic stack storage */
    
     str = malloc(100);  /* allocates 100 bytes of dynamic heap storage */
  
     y = foo(23);
     free(str);          /* deallocates 100 bytes of dynamic heap storage */
  }                      /* y and str deallocated as stack frame is popped */
  
  int foo(int z) {       /* z is dynamic stack storage */
     char ch[100];     /* ch is dynamic stack storage */
  
     if (z == 23) foo(7);
     
     return 3;           /* z and ch are deallocated as stack frame is popped,
                            3 put on top of stack  */
  }
  

• at the start of the program
• after the first call to foo
• after the second call to foo

Source of Information