-this should be taken into account when writing code which calls this function
-if portability is desired.
+if portability is desired,
+this should be taken into account when writing code which calls this function.
+.Sh LEGACY SYNOPSIS
+.Fd #include <libgen.h>
+.Pp
+.Ft char *
+.br
+.Fo dirname
+.Fa "const char *path"
+.Fc ;
+.Pp
+In legacy mode,
+.Fa path
+will not be changed.