How to use the libc++ GDB pretty-printers

Last year I wrote an article about my attempt so far at a system for testing Natvis files automatically. Here, I wanted to write the equivalent article but for GDB pretty-printers, for which I have an earlier article. As I said in the Natvis testing article: I want the CI to fail if I accidentally break the visualizers. Right now, I only know there’s something wrong if I check with my own eyes, or…