CSCE 434 Lecture 29

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Lecture Slides

Display vs. Access Links

Tradeoffs for one over other justified by:

• frequency of non-local accesses
• average lexical nesting depth
• ratio of calls to non-local access

Conventional wisdom:

• few registers = access links
• lots of registers = global display
• shallow average nesting = frame-based display

Parameter Passing

• Call by Value: no side-effects (apart from return value)
• Call by Reference: cannot guarantee that callee will not modify shared memory space

Variable argument length: caller can pass number of arguments as first parameter

Memory Management

alloc(k)

allocate a block of at least $k$ bytes in the free space pool, removes it from the pool, and returns its address

free(p)

places the block pointed to by $p$ back in the pool of free space for allocation

marks memory space as dead (guaranteed not to be used again as the same code)

Different Allocation schemes