How do I express conflicts?

A conflict means that a certain combination of packages and package features will not work. A number of conflict conditions can be expressed:

Note that such error conditions should only be added if there is absolutely no chance to get the combination of packages and features running. For example, in the case of multi-threaded programs it is often possible to add wrappers around unsafe libraries to fix the incompatibility.

It is not possible to express incompatibilities between package versions. Such incompatibilities should be detected when software is installed, not when it is used.