Re: scope and/or parameters (beginner)

[Robert Dewar <robert_dewar@my-dejanews.com>]

In article <7et4vr$sdj$1@nnrp1.dejanews.com>,
  dennison@telepath.com wrote:
> It was claimed here at work that nested subroutines
> should be avoided due to the elaboration overhead
> whenever the outer routine is called. That sounds a
> bit shaky to me. Is there a situation where there would
> be a runtime impact of nesting subroutines?

Sounds dubious as a general claim, but there is one
situation in which you will see overhead in GNAT (GNU C)
and that is if you create an access to (use & on) the
nested procedure. In this case a trampoline is built in
the stack, and the overhead can be significant.

In GNAT (but not GNU C) it would be possible to eliminate
this overhead by using fat pointers, and that is on our
optimizations-that-would-be-nice-to-so-sometime list. A
quite long list, which does however, get entries taken
off it frequently for actual implementation.

But note that this overhead is ONLY if the address is
taken, not in the normal case!

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