1 Programming Languages Storage Management Cao Hoaøng Truï Khoa Coâng Ngheä Thoâng Tin Ñaïi Hoïc Baùch Khoa TP. HCM

2 Storage Management Major run-time elements requiring storage Major operations requiring storage to be allocated/freed Storage management phases Storage management techniques

3 Run-time elements Code segments System run-time programs  library routines  storage management routines User-defined data structures Subprogram return points

4 Run-time elements Referencing environments Temporaries in expression evaluation Temporaries in parameter transmission Input-output buffers Miscellaneous system data

5 Run-time operations Subprogram call and return operations Data structure creation and destruction operations Component insertion and deletion operations

6 Storage Management Phases 1.Initial allocation: allocating free storage 2.Recovery: recovering unused storage  garbage collection 3.Compaction and reuse:  compaction: to construct large blocks  reuse: as initial allocation

7 Storage Management Techniques 1.Static storage management 2.Stack-based storage management 3.Heap storage management  fixed-size elements  variable-size elements

8 Static Storage Management Static allocation: allocation that remains fixed through out execution.

9 Stack-based Storage Management First Allocated - Last Freed. Simple storage recovery, compaction and reuse. Not applicable if storage needs to be allocated/freed at arbitrary points.

10 Heap Storage Management Heap: a block of storage within which data are allocated/freed in an arbitrary manner.

11 heap head initial free-space list heap head

12 heap (storage allocated by NEW) typical Pascal memory organization subprogram code segments and system run-time routines (statically allocated) stack bottom activation records free space heap bottom