cpp-id-data.h (UC): Was U, conflicts with U...
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=b6baa67d7947f

Index: libcpp/include/cpp-id-data.h
--- libcpp/include/cpp-id-data.h.orig
+++ libcpp/include/cpp-id-data.h
@@ -22,7 +22,7 @@ Foundation, 51 Franklin Street, Fifth Floor, Boston, M
 typedef unsigned char uchar;
 #endif
 
-#define U (const unsigned char *)  /* Intended use: U"string" */
+#define UC (const unsigned char *)  /* Intended use: UC"string" */
 
 /* Chained list of answers to an assertion.  */
 struct answer GTY(())
