Dissecting Shared Libraries
By Peter Seebach2005-03-22
Learning more about shared libraries
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Users interested in learning more about dynamic linking on Linux have a broad field of options. The GNU compiler and linker tool chain documentation is excellent, although the guts of it are stored in the info format and not mentioned in the standard man pages.
The manual page for ld.so contains a fairly comprehensive list of variables that modify the behavior of the dynamic linker, as well as explanations of the different versions of the dynamic linker that have been used in the past.
Most Linux documentation assumes that all shared libraries are dynamically linked because on Linux systems, they generally are. The work needed to make statically linked shared libraries is substantial and most users don't gain any benefit from it, although the performance difference is noticeable on systems that support the feature.
If you're using a pre-packaged system off the shelf, you probably won't run into very many shared library versions -- the system probably just ships with the ones it was linked against. On the other hand, if you do a lot of updates and source builds, you can end up with many versions of a shared library since old versions get left around "just in case."
As always, if you want to know more, experiment. Remember that nearly everything on a system refers back to those same few shared libraries, so if you break one of the system's core shared libraries, you're going to get to play with some kind of system recovery tool.
Tutorial Pages:
» Get to know your shared library
» How shared libraries work
» Compatibility's not just for relationships
» To debug, first you must know how to compile
» Modifying the dynamic linker search path
» Linking Mozilla
» Learning more about shared libraries
» Resources
First published by IBM DeveloperWorks
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