Index: bsd.options.mk
===================================================================
--- bsd.options.mk	(revision 382833)
+++ bsd.options.mk	(working copy)
@@ -96,6 +96,11 @@
 # ${opt}_QMAKE_OFF		When option is disabled, it will add its content to
 #				the QMAKE_ARGS.
 #
+# ${opt}_IMPLIES		When opt is enabled, options named in IMPLIES will
+#				get enabled too.
+# ${opt}_PREVENTS		When opt is enabled, if any options in PREVENTS are
+#				also enabled, it 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
@@ -387,6 +392,14 @@
 NEW_OPTIONS:=	${NEW_OPTIONS:N${opt}}
 .endfor
 
+## Enable options implied by other options
+# _PREVENTS is handled in bsd.port.mk:pre-check-config
+.for count in ${PORT_OPTIONS}
+.  for opt in ${PORT_OPTIONS}
+PORT_OPTIONS+=	${${opt}_IMPLIES}
+.  endfor
+.endfor
+
 # Finally, add options required by slave ports
 PORT_OPTIONS+=	${OPTIONS_SLAVE}
 
Index: bsd.port.mk
===================================================================
--- bsd.port.mk	(revision 382833)
+++ bsd.port.mk	(working copy)
@@ -5361,6 +5361,18 @@
 .  undef OPTNOCHECK
 .endfor
 .undef multi
+
+.for opt in ${PORT_OPTIONS}
+.  for conflict in ${${opt}_PREVENTS}
+.    if ${PORT_OPTIONS:M${conflict}}
+.      if empty(OPTIONS_WRONG_PREVENTS:M${opt})
+OPTIONS_WRONG_PREVENTS+=	${opt}
+.      endif
+OPTIONS_WRONG_PREVENTS_${opt}+=	${conflict}
+.    endif
+.  endfor
+.endfor
+.undef conflict
 .undef opt
 .endif #pre-check-config
 
@@ -5375,7 +5387,13 @@
 .for radio in ${OPTIONS_WRONG_RADIO}
 	@${ECHO_MSG} "====> You cannot select multiple options from the ${radio} radio"
 .endfor
-.if !empty(OPTIONS_WRONG_MULTI) || !empty(OPTIONS_WRONG_SINGLE) || !empty(OPTIONS_WRONG_RADIO)
+.if defined(OPTIONS_WRONG_PREVENTS)
+	@${ECHO_MSG} "====> Two or more enabled options conflict with each other"
+.  for prevents in ${OPTIONS_WRONG_PREVENTS}
+	@${ECHO_MSG} "=====> Option ${prevents} conflicts with ${OPTIONS_WRONG_PREVENTS_${prevents}} (select only one)"
+.  endfor
+.endif
+.if !empty(OPTIONS_WRONG_MULTI) || !empty(OPTIONS_WRONG_SINGLE) || !empty(OPTIONS_WRONG_RADIO) || !empty(OPTIONS_WRONG_PREVENTS)
 _CHECK_CONFIG_ERROR=	true
 .endif
 .endif # _check-config