Programming Languages Storage Management

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Programming Languages Storage Management

• Cao Hoaøng Truï
• Khoa Coâng Ngheä Thoâng Tin
• Ñaïi Hoïc Baùch Khoa TP. HCM

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Storage Management

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

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Run-time elements

• Code segments
• System run-time programs
• library routines
• storage management routines
• User-defined data structures
• Subprogram return points

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Run-time elements

• Referencing environments
• Temporaries in expression evaluation
• Temporaries in parameter transmission
• Input-output buffers
• Miscellaneous system data

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Run-time operations

• Subprogram call and return operations
• Data structure creation and destruction
  operations
• Component insertion and deletion operations

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Storage Management Phases

• Initial allocation allocating free storage
• Recovery recovering unused storage
• garbage collection
• Compaction and reuse
• compaction to construct large blocks
• reuse as initial allocation

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Storage Management Techniques

• Static storage management
• Stack-based storage management
• Heap storage management
• fixed-size elements
• variable-size elements

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Static Storage Management

• Static allocation allocation that remains fixed
  through out execution.

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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.

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Heap Storage Management

• Heap a block of storage within which data are
  allocated/freed in an arbitrary manner.

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