http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57757
--- Comment #4 from Harald van Dijk <harald at gigawatt dot nl> --- It looks like this is a simple matter of adding an extra case in libcpp/lex.c:cpp_avoid_paste, returning true for (CPP_STRING, CPP_NAME) when UDLs are enabled. (I'd attach a working patch instead of a brief one-sentence description, but won't because I unfortunately expect copyright assignment would be a problem.)
