When my experience with Slackware was still limited I often run into problems when installing some program (from source) that needed some library that was just one or two points higher than the one I got. Now I'd look for the package that contains that library on slackware.com (the current package browser is at packages.slackware.com) and install a more recent version from source.
In short: check for the package in the FILELIST.TXT of slackware-current; go to source and download the files for that package to a folder for compiling; su root to execute the buildscript (sh ./some_buildscript) and finish with upgradepkg /tmp/some_new_package.
If you don't know the name of the package your obsolete library lives in, cd to /var/log/packages and do grep -i name_of_your_lib to find out. If you get no result, the lib might not ship with regular Slackware at all, but mabye slackbuilds.org has it.
While trying to install from slackware-current from source is what I opt for now, in the past I might do the trick of symlinking the library I did not have, to the older version I did have. That might work, but might brake things as well. I was reminded of this, when I tried to install pyqt4 in Slackware 13.7. It failed with:
configure.py: error: '/usr/bin/qmake-qt4' "is not a file"
Which turned out a somewhat cryptic way of telling me that qmake-qt4 was not on my system, even though qt4 was installed. After some G*gling I followed a suggestion somewhere that there where naming conflicts with qmake (which I had) and versions of qt. So, I symlinked qmake-qt4 to qmake. BTW /usr/bin/qmake on my system was already a symbolic link to /usr/lib/qt/bin/qmake, so I used that:
su root; ln -s /usr/lib/qt/bin/qmake /usr/bin/qmake-qt4
That worked, but compiling failed anyway, after 20 minutes or so me checking whether it was done or not, with a whole bunch other errors, which I won't paste here since I have no idea how to begin solving them. Maybe it was because I had to use a more recent version of pyqt than the one the slackbuilds script had used (original source no longer available)? Testing that idea I tried a package of pyqt from elsewhere that was of the same version the slackbuild script had used, and got this:
Determining the layout of your Qt installation...
This is the GPL version of PyQt 4.4.4 (licensed under the GNU General Public
License) for Python 2.6.4 on linux2.
Error: This version of PyQt and the Desktop edition of Qt have incompatible licenses.
Really? Why do I want that qt stuff anyway! Well, I wanted to try ReText which depended on it, but now I think about it, I never liked any of that way-to-commercial-qt stuff anyway. So far, I stayed away from it, now I am resolved to keep it that way.
Update: I had to surrender to qt when I wanted to use Anki. Sigh.
