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From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.arch,comp.unix.wizards,comp.os.misc
Subject: Re: Shared libraries (Was: Re: Big Programs Hurt Performance)
Message-ID: <29936@sun.uucp>
Date: Sun, 4-Oct-87 00:13:08 EDT
Article-I.D.: sun.29936
Posted: Sun Oct  4 00:13:08 1987
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> Needless to say, the Amiga OS is not Unix, for one thing, Unix isn't
> going to run on a 512K machine with no MMU and two floppies. So they
> don't have to worry about backward compatibility with Version 7 &
> earlier programs written 15 years ago like Sun does :-).

Well, that may have been *part* of the reason the scheme described in the Sun
paper doesn't require libraries to be explicitly opened, but it's not all of
it.  Since you tell the linker which libraries you're linking with, it can
leave information about which shared libraries are needed around for the
startup code to use, so that code can do the opening and attaching for you.
This scheme could *permit* you to open libraries at any time, or close them, if
it wanted, but it doesn't *require* you to do so, regardless of which library
you're using.

Such a scheme follows the dictum "simple things should be simple" (i.e., if you
want to call a routine, you just write a call in your code and tell the linker
which libraries to look in) and "complicated things should be possible" (while
the scheme described in that paper doesn't include a programmatic interface to
the run-time loader, it doesn't prevent such an interface from being provided,
and lists this as a future direction).

(Multics, one of the original systems that provided dynamic linking to shared
libraries, didn't require you to explicitly attach these libraries either.)
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com