Re: Addresses of Subprograms (was: New GNAT ports)

[ok@goanna.cs.rmit.EDU.AU (Richard A. O'Keefe)]

kilgallen@eisner.decus.org (Larry Kilgallen) writes:
[There is a distinction between the "address" of a subprogram,
 meaning "what do I use for an indirect call"
 and the "address" of a subprogram,
 meaning "where does the executable code start".
 He cites the Alpha VMS and Macintosh 68k environments as examples,
 and asks
]
>Do other operating systems have this separation, and which is the
>"true" meaning for specifying the address of a subprogram from an
>Ada perspective ?

The Apollo systems did this too.  I never used Aegis, but the UNIX
systems they shipped had C function pointers being pointers to
indirect blocks, the actual code being elsewhere.  It was actually
a pain for us (Quintus) because we wanted to put a certain procedure
at a particular address (so we could use 16-bit addresses on a 68k)
and you could never expect a procedure to be in the same place twice
running.

Lisp systems have often done this (the "slow link" / "fast link"
distinction) in order to support run-time redefinition of procedures.

What do the Ada->J-code compilers do?

-- 
My tertiary education cost a quarter of a million in lost income
(assuming close-to-minimum wage); why make students pay even more?
Richard A. O'Keefe; http://www.cs.rmit.edu.au/%7Eok; RMIT Comp.Sci.