-# define isblank(c) \
- (GL_LINK_WARNING ("isblank is unportable - " \
- "use gnulib module isblank for portability"), \
- isblank (c))
+# if HAVE_RAW_DECL_ISBLANK
+_GL_WARN_ON_USE (isblank, "isblank is unportable - "
+ "use gnulib module isblank for portability");
+# endif