And also in QtXmlPatterns (now also retired).

Just for the record, Xalan-C is even less maintained than libxslt. It had no releases for over a decade, and I made a final 1.12 release in 2020 adding CMake support, since the existing builds had bitrotted significantly, along with a number of outstanding bugfixes.

I initiated its removal to the Apache attic in 2022 in https://marc.info/?l=xalan-c-users&m=165593638018553&w=2 and the vote to do this was in https://marc.info/?t=166514497300001&r=1&w=2&n=20. It has now gone nearly four years without any commits being made.

It's a great shame we are now in a situation where there is only a single proprietary implementation of the very latest version of the standard, but even the open-source 1.x implementations are fading fast. These technologies have fallen out of favour, and the the size and complexity of the standards is such that it's a non-trivial undertaking to keep them maintained or create a modern reimplementation.