Index: lib/libc/gen/basename.3
===================================================================
--- lib/libc/gen/basename.3
+++ lib/libc/gen/basename.3
@@ -61,8 +61,16 @@
 returns a pointer to internal storage space allocated on the first call
 that will be overwritten
 by subsequent calls.
+.Pp
+Other vendor implementations of
+.Fn basename
+may store their result in the provided buffer,
+making it safe to use in multithreaded applications.
+Future versions of
+.Fx
+will follow this approach as well.
 .Fn basename_r
-is therefore preferred for threaded applications.
+will then be obsolete.
 .Sh RETURN VALUES
 On successful completion,
 .Fn basename
Index: lib/libc/gen/dirname.3
===================================================================
--- lib/libc/gen/dirname.3
+++ lib/libc/gen/dirname.3
@@ -56,10 +56,11 @@
 .Pp
 Other vendor implementations of
 .Fn dirname
-may modify the contents of the string passed to
-.Fn dirname ;
-this should be taken into account when writing code which calls this function
-if portability is desired.
+may store their result in the provided buffer,
+making it safe to use in multithreaded applications.
+Future versions of
+.Fx
+will follow this approach as well.
 .Sh RETURN VALUES
 On successful completion,
 .Fn dirname