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From: quenelle@ssiwest.UUCP (Chris Quenelle)
Newsgroups: comp.windows.x
Subject: (none)
Message-ID: <9005291632.AA06491@ssiwest.com>
Date: 29 May 90 16:32:13 GMT
Article-I.D.: ssiwest.9005291632.AA06491
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 54

Subject: Re: LD_LIBRARY_PATH woes


WARNING: Much of what you are about to read could be regarded as a flame.
 If you have a sensitive disposition, you may want to skip this posting.


> Just copy the OpenWindows dynamic libraries into /usr/lib ...

This was one of the things I wanted to avoid.
Due to the fact that we have several file servers, several network
servers and workstations on three sub-nets, copying the libraries
into /usr/lib would not only take up a lot of extra space, but it
would also be very hard to maintain when we upgraded OS versions etc.

> The secret is the loader's use
> of major and minor version numbers. The major version of the library that
> gets loaded must match the major version the program was compiled with. The
> loader uses the highest minor version available. The MIT libraries are
> major version 4, and the OpenWindows libraries are major version 0.

In some perhaps-as-yet-unreleased version of OpenWindows which 
may-or-may-not exist somewhere, but which we have, the release comes
with symbolic links for libraries with a major version number of 4
for libXt and libX, the same as the MIT released X version numbers.
This means that in order to run an OW tool with OW libraries,
the OpenWindows directory has to be FIRST in your LD_LIBRARY_PATH
and in order to run an MIT X tool with the MIT X libraries, the MIT
directory has to be FIRST in your LD_LIBRARY_PATH.  I've recently
run into a problem with xterm giving me a segmentation violation when
it was compiled with MIT X, but dynamically linked with OW libX/libXt.
This is evidence to me that it is important to get the right one.

> So when you run a program, everything works fine since
> the OpenWindows program were compiled with version 0 libraries and the
> MIT programs with version 4. The only possible gotcha is when you want to
> compile a program to use the OpenWindows libraries, you have to use
> (for example) -lX11.0 instead of -lX11.

Which means that after using imake, you have to go in and modify
the Makefiles by hand ?  Yuck.

> Take a look at the manual pages ld(1) and ldd(1)

I've read the man pages, and also the manual section on
using Shared Libraries.  It's a very complicated mechanism,
and, in my opinion, not thought out enough to be flexible.

--chris

@---@  Chris Quenelle   ( X-Rat )     (415) 373-8023      \|/ Supercomputer   
\.X./  ...!uunet!ssi!quenelle                             -+-----Systems----- 
 \ /   ssiwest!quenelle@lll-lcc.llnl.gov                  /|\      Inc.       
==o==  Nothing the God of Bio-Mechanics wouldn't let you in heaven for ?