I upgraded from glibcso 2.1.3 (came with Slackware 7.1) to glibcso 2.2.5 (Slackware 8.1 package) in order to use Opera 7.23.
I had installed glibc 2.1.3 and other packages needed to compile.
After the upgrade I could no longer compile shared programs. I am trying to compile for a group using the older glibcso so don't want to simply upgrade glibc to 2.2.5 to fix this problem.
I therefore deleted all the files from glibcso 2.2.5 (rm /lib/*2.2.5) and ran ldconfig to restore the symlinks to point at 2.1.3.
But now I still cannot compile because something somewhere is still pointing to glibc 2.2.

When I try to compile, or do ldd to determine dependencies, or simply try to run the following
programs (from binutils.tgz, used in compiling):
as nm runlib (and others) I am told:
error in loading shared libraries: libc.so.6: invalid ELF header

When I try to run the following:
perl, db_archive (and other db_), splay I am told:
version 'GLIBC_2.2' not found (required by /lib/libdb.so.3)

I get one of these messages when I try to compile two small programs which I could compile on another system with glibc and glibcso both upgraded.
There is sometimes also a complaint about not finding 2.3.

I ran across one posting here about deleting libpthread* to solve another glibc problem.
Can I try this using a rescue disk? Removepkg glibc and glibcso (at which point nothing works)
then boot with rescue disk, rm libpthread* and reinstall glibcso and glibc.
Instead of a rescue disk I actually have a small ramdisk linux that boots from DOS,
and if I ran installpkg would the package install to the hard drive which I have mounted and cd'd to rather than trying to install to the RAMdisk linux?

I am using a small (basiclinux 2.1) version of Slackware 7.1. Members of our mail list tried to help and are interested in the solution. This is a linux designed to work for beginners.

I could always give up and put back glibcso 2.2.5 and upgrade glibc to match,
but would I then also need to upgrade egcs and binutils and ldlinux?

ouch
you should never play with glibc, libc and glib, at least on slackware and other low package distribution. However, that happen to everyone (that once happened to me) and it is possible to save your box, but that will be hard.

You should reinstall slackware glibc-2.1.3 with the old slackware 7.1 .tgz package.

Another (last chance) way to do is the following : get another harddrive, or something like this (any big enought device will be good I believe). Install a minimal old slackware 7.1 on it, then plug these two harddrive together... and then move everything that may have been altered from the new install to your old one.

It is almost impossible to upgrade glibc on slackware... in fact, slackware is very hard to upgrade at my opinion, I like it much for it flexibility, but soon you have to reinstall. If you really want to give a try, keep in mind that glibc has tons of dependency, you'll have to install glibc, glib, libc, ...
If you suceed, however, let me know