Programming languages storage management

1 Programming Languages Storage Management Cao Hoàng Trụ Khoa Công Nghệ Thông Tin Đại Học Bách 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