mail/libc_s

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Date: Wed, 2 Jul 1997 12:08:53 -0400 (EDT)
From: Normand McGuire <norm@connectware.ca>
To: Gordon Matzigkeit <gord@m-tech.ab.ca>
Subject: Re: -lc_s shared libraries
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On 1 Jul 1997, Gordon Matzigkeit wrote:

> Are you sure that on SCO Openserver 5 you need to specify
> /lib/libc.so?  From what I understood about that platform, specifying
> `-lc' (which is what the C compiler does by default) is good enough,
> and links in the shared version if it exists.

>From my experience, definitely. Look below.

> Do you know otherwise?  Can you show the results of specific tests to
> me that would prove your point?

Here is a sample of a session demonstrating this on my system. I show the 
source code, default cc file and three compiles with three a.out file 
sizes. See for yourself:

Script started on Wed Jul  2 11:21:58 1997
$ cat t.c
main()

	{
	printf("Hello, world\n");
	}
$ cat /etc/default/cc
#	@(#) cc.default 20.1 94/12/04 
#	
#	Copyright (C) The Santa Cruz Operation, Inc. 1994-1995.
#	This Module contains Proprietary Information of
#	The Santa Cruz Operation, and should be treated as Confidential.
#
#	Core development /bin/cc reads /etc/default/cc.
#	Cross development /usr/ods30/bin/cc reads /etc/default/crossdevcc.
#	If a prefix is specified, cc reads /etc/default/<prefix>cc instead.
#
FLAGS=
LIBS=
$ cc t.c
$ l a.out
-rwxrwxr-x   1 root     sys        46334 Jul  2 11:22 a.out
$ cc t.c -lc
$ l a.out
-rwxrwxr-x   1 root     sys        46334 Jul  2 11:22 a.out
$ cc t.c /lib/libc.so
$ l a.out
-rwxrwxr-x   1 root     sys         3988 Jul  2 11:22 a.out
$ exit

script done on Wed Jul  2 11:22:32 1997

And believe me, this script session is not a fake.

> The reason I'm asking is that I, too, would like to know how Autoconf
> packages can best take advantage of shared libraries, especially in a
> general, rather than a test-by-test way.

The section of my configure.in script that takes care of shared libraries
is short and not annoying to repeat. You may want to incorporate it into 
the AC_PROG_CC macro or create a new one for it. So far, I've seen only 
two kinds of behaviors regarding shared libraries: if they are not used 
automatically when invoking cc, just include them when linking the 
program. And it worked so far. However, you guys may have a whole lot 
more flavors of system to run on compared to me.

Here is the portion of the shared library check in my configure.in script:

# STEP 2 - Check for libraries

AC_MSG_CHECKING([for libc.so])
if test -r /lib/libc.so; then
    AC_MSG_RESULT([yes (/lib/libc.so)])
    LIBS="$LIBS /lib/libc.so"
elif test -r /usr/lib/libc.so; then
    AC_MSG_RESULT([yes (/usr/lib/libc.so)])
    LIBS="$LIBS /usr/lib/libc.so"
else
    AC_MSG_RESULT(no)
    AC_CHECK_LIB(c_s, main)
    fi

> Could you be more specific when you mention `some other System V Unix
> systems'?  What are their canonical system names (i.e. *-*-sco3.2v4*)?

By 'some other Unix systems' requiring that you explicitely specify the 
shared library name when linking the program, I meant specifically:

o Bull Open Software (Unix System V Release 4, but don't remember if it is x86)

o Interactive Unix System V/386 all versions

o SCO Unix 3.2v4 and SCO OpenServer 5

o Sun Solaris 2.3 / SunOS 5.3

All others that we've compiled and run on will automatically use shared 
libraries when available, namely:

IBM's AIX 3.2.* and 4.*
HP's HPUX 8.*, 9.* and 10.*
DEC Ultrix, OSF/1 and DEC Unix all versions tried
DataGeneral's DGUX all versions tried
Sequent's DYNIX/ptx 2.1 and 4
Linux all versions tried
SGI's Irix all versions tried
NCR and AT&T Unix System V/386 Release 4
Sun Solaris 2.4 (SunOS 5.4) and Solaris 2.5 (SunOS 5.5)
SunOS 4.1*
Unisys Unix System V/386
Unixware all versions

Normand McGuire