id	summary	reporter	owner	description	type	status	priority	milestone	component	version	severity	resolution	keywords	cc
228	rpm: Add legacy runtime packages support	dmik		"Many dynamic libraries use versioning in DLL names to express incompatible ABI changes (i.e. if the old version is named `libxyz1.dll`, the new one becomes `libxyz2.dll` and so on). This way, an old application, built against `libxyz1.dll` continues to work even when `libxyz2.dll` gets installed.

Unfortunately, RPM doesn't normally allow two versions of the same package to co-exist even if the names of provided files differ. So the old DLL (regardless of its name) is removed when a newer package is installed. This obviously breaks old applications.

The traditional solution used by RPM-based systems is to provide legacy packages with different names (like `libxyz-legacy` or `libxyxz-compat` which include old versions and, due to different package names, may co-exist with the newer packages. However, this approach has its pitfalls:

1. A separate .spec file is required for the legacy version (which requires a separate rpmbuild run etc).
2. If you have more than one legacy version to maintain, you will have to come up with as many separate .spec files and unique package names as you have legacy versions.

This is time consuming and boring, given that all you need from the legacy package is the runtime DLL (which is already built, tested and works).

Another possible approach that is also frequently used is to rebuild all applications involving the given software against the new version and release new RPMs for them. But it is also not ideal:

1. There may be quite a lot of such applications.
2. Some applications may be not ready for the new version and require some work.

So this is also time consuming and boring.

This ticket is to introduce a different solution: automatically create legacy sub-packages within the main package that will take previously built DLLs and just repack them. This requires almost zero work from the package maintainer each time when the library ABI changes in an incompatible way.

"	enhancement	closed	major		rpm		low	fixed