Linker and Libraries Guide

Versioning an Existing (Non-versioned) Shared Object

Versioning an existing, non-versioned shared object requires extra care. The shared object delivered in a previous software release has made available all its global symbols for others to bind with. Although you can determine the shared object's intended interfaces, others might have discovered and bound to other symbols. Therefore, the removal of any symbols might result in an application's failure on delivery of the new versioned shared object.

The internal versioning of an existing, non-versioned shared object can be achieved if the interfaces can be determined, and applied, without breaking any existing applications. The runtime linker's debugging capabilities can be useful to help verify the binding requirements of various applications. See Debugging Library. However, this determination of existing binding requirements assumes that all users of the shared object are known.

If the binding requirements of an existing, non-versioned shared object cannot be determined, then you should create a new shared object file using a new versioned name. See Coordination of Versioned Filenames. In addition to this new shared object, the original shared object must also be delivered so as to satisfy the dependencies of any existing applications.

If the implementation of the original shared object is to be frozen, then maintaining and delivering the shared object binary might be sufficient. If, however, the original shared object might require updating then an alternative source tree from which to generate the shared object can be more applicable. Updating might be necessary through patches, or because its implementation must evolve to remain compatible with new platforms.