Thanks, one thing I didn't notice earlier:

+  xsignal1 (Qinvalid_read_syntax,
+            CALLN (Fformat, build_pure_c_string ("\\N{%s}"), name));

This can run Emacs out of pure space unnecessarily.  Use AUTO_STRING instead of
build_pure_c_string.

Also, I've lost track of what this patch is building on. Perhaps send all the
patches next time....