Index: sys/sys/cdefs.h
===================================================================
RCS file: /cvsroot/src/sys/sys/cdefs.h,v
retrieving revision 1.151
diff -u -r1.151 cdefs.h
--- sys/sys/cdefs.h	21 Mar 2020 22:45:47 -0000	1.151
+++ sys/sys/cdefs.h	17 Apr 2020 12:12:06 -0000
@@ -173,7 +173,7 @@
 #endif
 #define	__CTASSERT0(x, y, z)	__CTASSERT1(x, y, z)
 #define	__CTASSERT1(x, y, z)	\
-	typedef struct { \
+	typedef struct y ## z ## _struct __unused { \
 		unsigned int y ## z : /*CONSTCOND*/(x) ? 1 : -1; \
 	} y ## z ## _struct __unused