In this Podcast, I talk about the libpng upgrade. If you have any questions, you can reach me at david at linuxcrazy dot com, or on freenode irc, channel #linuxcrazy.
The Gentoo libpng 1.2.x to 1.4.x upgrade didn't go very smoothly. Reason seems to be that libpng usage is odd, it provides both libpng14.* and libpng.* files.
Some packages like to use versioned libs while some other don't and it seems to lead to giant mess in *.la files.
In the past, if a source code package developer wanted to take advantage of the power of shared libraries, he needed to write custom support code for each platform on which his package ran. He also had to design a configuration interface so that the package installer could choose what sort of libraries were built.
GNU Libtool simplifies the developer's job by encapsulating both the platform-specific dependencies, and the user interface, in a single script. gnu Libtool is designed so that the complete functionality of each host type is available via a generic interface, but nasty quirks are hidden from the programmer.
GNU Libtool's consistent interface is reassuring... users don't need to read obscure documentation in order to have their favorite source package build shared libraries. They just run your package configure script (or equivalent), and libtool does all the dirty work.
Libpng Update Tips
SONAME + Shared Libs Explained
irc network freenode channel #linuxcrazy