Re: Stack frames & static predecessors

> [The calling procedure passes in pointers to the stack frames of all
> of the lexically enclosing procedures, a structure known as a display.
> The code to create the display at each call point is tedious but not
> complex, and the techniques have been known since Algol 60, if not
> longer. This used to be a standard topic in compiler texts, at least
> until the academic world switched from Pascal to C. Take a look at the
> x86 ENTER instruction, which is specifically designed to create stack
> frames with displays. -John]


If you are passing the inner function around using a function pointer
(or in Pascal a function parameter), this is not possible, because
your "procedure Bar" is actually a "procedure Bar (var x: integer)" so
to speak. Therefore, the compiler will build on-the-fly (on the stack
likely) the executable code to "add" the initial parameter, and pass a
pointer to the "trampoline" that it has built on the stack.


On the x86, for example, the trampoline may look like


      PUSH [ESP]
      MOV [ESP+4], <static chain pointer>
      JMP Bar


where the static chain pointer is known at trampoline-generation time,
and thus can be written as an immediate.


Paolo

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