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From: jdh@bu-pub.bu.edu (Jason Heirtzler)
Newsgroups: comp.sys.sgi
Subject: so, you want to use a shared library?
Keywords: don't try this at home, folks
Message-ID: <61580@bu.edu.bu.edu>
Date: 30 Jul 90 02:37:06 GMT
Sender: news@bu.edu.bu.edu
Reply-To: jdh@bu-pub.bu.edu (Jason Heirtzler)
Organization: Boston University, Scientific Computing and Visualization Group
Lines: 47

Two questions:

	Has anyone (besides SGI) built their own shared libraries in IRIX?

	Did you enjoy it?

There's all kinds of nasty prerequisites and special conditions before you
can build your very own shared library.  Let me quote The Book:

	[ choosing a data and text region address ]

	"Each region should be on a 4M boundry.  The two regions should
	be adjacent, with the address of the text region lower than the
	address of the data region.  The regions should be at the highest
	address possible below 0x0c000000."

This isn't too bad, but then it goes on to say how you're likely to have
address conflicts if you try to link a program and use your shared library
and another shared library:

	"If you plan to release a library, you must consult with concerned
	parties to agree on a region address."

Every 3rd party developer? That's going to be one heck of a conference call.

Had enough?  No?  Then take a look at that branch table you gotta build
for every function you include in your library.  Not tough to do, but these
are the things computers should do themselves.

Or here's another:

	"External symbols have fixed addresses.  If an external symbol
	moves, you have to relink all a.out files that use the library.
	This restriction applies to both text and data symbols."

Anyways, you get the idea.  To contrast, none of this is necessary with
shared libraries in SunOS.  They're clean and fairly simple.  There's no
such thing as a "shared library specification file."  They also have major
and minor revision levels for the libraries and the newest version always
chosen (at run time, according to specific rules) for you.

Will these (sysV style?) shared libraries be changing?  Are we poor
customers stuck until/if IRIX becomes sysV R4 based?  What about then?

-------------------------------------------------------------------
Jason Heirtzler           (617) 353-2780       jdh@bu-pub.bu.edu
Information Technology    Boston University    ..!bu.edu!bu-pub!jdh