compile.el contains this line:

       (: "[ skipping " (+ ".") " ]")

I think this should be:

       (: "[ skipping " (+ (regexp ".")) " ]")

A typical error message is:

boost/container/detail/flat_tree.hpp:589:25:   [ skipping 5 instantiation contexts, use -ftemplate-backtrace-limit=0 to disable ]

This is diagnosed as 'error' and not 'note'.