Discovered issue while testing 
http://porkchop.redhat.com/errata/showrequest.cgi?advisory=2005:543

Ok, I tried this again:
.qa.[root@ia64-4AS ~]# rpm -ivh
/mnt/redhat/beehive/comps/dist/4E/ruby/1.8.1-7.EL4.0/ia64/*
Preparing...                ########################################### [100%]
   1:ruby-libs              ########################################### [ 13%]
   2:ruby                   ########################################### [ 25%]
   3:irb                    ########################################### [ 38%]
   4:ruby-debuginfo         ########################################### [ 50%]
   5:ruby-devel             ########################################### [ 63%]
   6:ruby-docs              ########################################### [ 75%]
   7:ruby-mode              ########################################### [ 88%]
   8:ruby-tcltk             ########################################### [100%]
.qa.[root@ia64-4AS ~]# rpm -ivh
/mnt/redhat/beehive/comps/dist/4E/ruby/1.8.1-7.EL4.0/i386/ruby-libs-1.8.1-7.EL4.0.i386.rpm
Preparing...                ########################################### [100%]
   1:ruby-libs              ########################################### [100%]
*** glibc detected *** double free or corruption (fasttop): 0x6000000000044e90 ***
error: %post(ruby-libs-1.8.1-7.EL4.0.i386) scriptlet failed, exit status 0
.qa.[root@ia64-4AS ~]# rpm -q --scripts ruby-libs.i386
postinstall scriptlet (using /bin/sh):
/sbin/ldconfig
postuninstall scriptlet (using /bin/sh):
/sbin/ldconfig

So I should reassign this to bash or glibc then?

erm, I've tracked this problem down. this was because of lacking of ia32el
package.  here is what I've checked things:

.qa.[root@ia64-4AS ~]# rpm -q bash
bash-3.0-19.2.ia64
bash-3.0-19.2.i386
.qa.[root@ia64-4AS ~]# /emul/ia32-linux/bin/bash
-bash: /emul/ia32-linux/bin/bash: cannot execute binary file
.qa.[root@ia64-4AS ~]# file /emul/ia32-linux/bin/bash
/emul/ia32-linux/bin/bash: ELF 32-bit LSB executable, Intel 80386, version 1
(SYSV), for GNU/Linux 2.2.5, dynamically linked (uses shared libs), stripped
.qa.[root@ia64-4AS ~]# rpm -qf /emul/ia32-linux
file /emul/ia32-linux is not owned by any package
.qa.[root@ia64-4AS ~]# rpm -q ia32el
package ia32el is not installed
.qa.[root@ia64-4AS ~]# rpm -ivh
/mnt/redhat/beehive/comps/dist/4E-lacd-U1/ia32el/1.2-3/ia64/ia32el-1.2-3.ia64.rpm
Preparing...                ########################################### [100%]
   1:ia32el                 ########################################### [100%]
.qa.[root@ia64-4AS ~]#  /emul/ia32-linux/bin/bash
.qa.[root@ia64-4AS ~]# ldconfig
.qa.[root@ia64-4AS ~]# exit
.qa.[root@ia64-4AS ~]# rpm -e ruby-debuginfo ruby-devel ruby-libs.i386 ruby-mode
ruby-libs.ia64 ruby-tcltk ruby irb
.qa.[root@ia64-4AS ~]# rpm -qa | grep ruby
ruby-docs-1.8.1-7.EL4.0.ia64
.qa.[root@ia64-4AS ~]# rpm -e ruby-docs
.qa.[root@ia64-4AS ~]# rpm -ivh
/mnt/redhat/beehive/comps/dist/4E/ruby/1.8.1-7.EL4.0/ia64/* Preparing...       
        ########################################### [100%]
   1:ruby-libs              ########################################### [ 13%]
   2:ruby                   ########################################### [ 25%]
   3:irb                    ########################################### [ 38%]
   4:ruby-debuginfo         ########################################### [ 50%]
   5:ruby-devel             ########################################### [ 63%]
   6:ruby-docs              ########################################### [ 75%]
   7:ruby-mode              ########################################### [ 88%]
   8:ruby-tcltk             ########################################### [100%]
.qa.[root@ia64-4AS ~]# rpm -ivh
/mnt/redhat/beehive/comps/dist/4E/ruby/1.8.1-7.EL4.0/i386/ruby-libs-1.8.1-7.EL4.0.i386.rpm
Preparing...                ########################################### [100%]
   1:ruby-libs              ########################################### [100%]

So this is not a bug at all.

No, this is a bug. You should have a dependency requirement for ia32el if it is
"lacking" at the time of install.

Huh? How? It's impossible since ix86 packages are shared for ix86 itself and
ia64 architectures now and ia32el doesn't work for ix86 and it'd rather not
necessary for ix86 at all. or Are you saying there is any ix86 packages which
requires ia32el? AFAICS there is not.

It should be also impossible because ia32el is in LACD. the package in main
can't makes any dependencies other than its area.

You tell me :-)  You said the problem was lack of ia32el in comment #3.  Usually
when a package is necessary for something else to work correctly it is
considered a dependency.  Based on what I understand you to be saying, ia32el is
"required" to avoid "error: %post(ruby-libs-1.8.1-7.EL4.0.i386) scriptlet
failed."  Is this not the case?

Yes. and I also said it won't be able to be required due to comment #5 and
comment #6 reasons. Why I asked you is you may know a lot about the multilib
stuff than me, because of your job. you should see the same problem when you
removed ia32el from ia64 machine, and trying to install i386 library anything else.

e.g.
.qa.[root@ia64-4AS ~]# rpm -qa | grep i386 | wc -l
202
.qa.[root@ia64-4AS ~]# rpm -q --whatrequires ia32el
no package requires ia32el
.qa.[root@ia64-4AS ~]# for i in `rpm -ql ia32el`; do rpm -q --whatrequires $i; done
no package requires /etc/rc.d/init.d/ia32el
no package requires /usr/lib/ia32el
no package requires /usr/lib/ia32el/ia32exec.bin
no package requires /usr/lib/ia32el/is_ia32el
no package requires /usr/lib/ia32el/libia32x.so
no package requires /usr/lib/ia32el/suid_libia32x.so
no package requires /usr/share/doc/ia32el-1.2
no package requires /usr/share/doc/ia32el-1.2/COPYING
no package requires /usr/share/doc/ia32el-1.2/COPYING.LIBC
no package requires /usr/share/doc/ia32el-1.2/EULA

Although there is a lot of i386 packages installed but no packages required
neither ia32el nor the files in ia32el. it means you can remove ia32el without
any complaints if you like.

Closing this as NOTABUG again.