Index: bsd.options.mk
===================================================================
--- bsd.options.mk	(revision 358193)
+++ bsd.options.mk	(working copy)
@@ -98,6 +98,10 @@
 # ${opt}_QMAKE_OFF			When option is disabled, it will add its content to
 #							the QMAKE_ARGS.
 #
+# ${opt}_IMPLIES			When option is enabled, options named in its contents will
+# 							be enabled too
+# ${opt}_PRECLUDES			When option is enabled, enabling any of the options
+# 							in its content will produce an error
 # ${opt}_USE=	FOO=bar		When option is enabled, it will  enable
 #							USE_FOO+= bar
 #							If you need more than one option, you can do
@@ -386,6 +390,20 @@
 NEW_OPTIONS:=	${NEW_OPTIONS:N${opt}}
 .endfor
 
+# Enable options implied by other options
+.for opt in ${PORT_OPTIONS}
+PORT_OPTIONS+=	${${opt}_IMPLIES}
+.endfor
+
+# Prevent options that conflict
+.for opt in ${PORT_OPTIONS}
+.  for conflict in ${${opt}_PRECLUDES}
+.    if ${PORT_OPTIONS:M${conflict}}
+IGNORE=	Option ${opt} conflicts with option ${conflict}
+.    endif
+.  endfor
+.endfor
+
 # Finally, add options required by slave ports
 PORT_OPTIONS+=	${OPTIONS_SLAVE}