* readlink/realpath (https://austingroupbugs.net/view.php?id=1457)
* find -print0, xargs -0 and read -d (https://austingroupbugs.net/view.php?id=243)
* find -iname (https://austingroupbugs.net/view.php?id=1031
* sed -E (https://austingroupbugs.net/view.php?id=528)
* set -o pipefail (https://austingroupbugs.net/view.php?id=789)
The sed -E option makes it easy to portably use extended regular expressions.
The find -print0, xargs -0, and read -d provide portable ways to securely process lists of files. They were already widely implemented, but now they're officially part of the spec and can be counted on being present in many other places.
Thanks for the improvements on POSIX, I've read many issues and discussions raised by you in the past couple of years.
If fact, I think it was one of yoir comments on make(1)'s dynamic dependency graph that reassured me I had a correct grasp on its execution model!
Finally! It always seemed very strange to me that posix said that shared objects were a thing and provided a rtld API for using them, but never specified how to create them.
It wasn't standardized before, so it didn't "always work" on any implementation.