+# A semicolon‐separated list of regular expressions which paths should be required to match when finding files.
+FINDFILTERONLY :=
+
+# A semicolon‐separated list of regular expressions for paths which should be filtered out when finding files.
+FINDFILTEROUT :=
+
+# A semicolon‐separated list of regular expressions for paths which paths should be required to match when finding includes.
+#
+# This is generally only useful when `SRCDIR´ and `INCLUDEDIR´ point to the same location.
+# In that situation, this variable can be used to select certain files as includes, leaving the others to be recognized as sources instead.
+#
+# Otherwise, appropriately constructing `FINDFILTERONLY´ to look at the base directory of the files it finds should be sufficient.
+FINDINCLUDEFILTERONLY :=
+
+# A semicolon‐separated list of regular expressions for paths which should be filtered out in addition to those in `FINDFILTEROUT´ when finding includes.
+#
+# This is generally only useful when `SRCDIR´ and `INCLUDEDIR´ point to the same location.
+# In that situation, this variable can be used to exclude certain files from being recognized as includes, which will make them recognized as sources instead.
+#
+# Otherwise, appropriately constructing `FINDFILTEROUT´ to look at the base directory of the files it finds should be sufficient.
+FINDINCLUDEFILTEROUT :=
+
+# If not empty, the regular expression provided by `FINDFILTERONLY´ is an extended regular expression.
+FINDFILTERONLYEXTENDED :=
+
+# If not empty, the regular expression provided by `FINDFILTEROUT´ is an extended regular expression.
+#
+# By default, this matches `FINDFILTERONLYEXTENDED´
+FINDFILTEROUTEXTENDED := $(FINDFILTERONLYEXTENDED)
+
+# If not empty, the regular expression provided by `FINDFILTEROUT´ is an extended regular expression.
+#
+# By default, this matches `FINDFILTERONLYEXTENDED´
+FINDINCLUDEFILTERONLYEXTENDED := $(FINDFILTERONLYEXTENDED)
+
+# If not empty, the regular expression provided by `FINDINCLUDEFILTEROUT´ is an extended regular expression.
+#
+# By default, this matches `FINDFILTEROUTEXTENDED´
+FINDINCLUDEFILTEROUTEXTENDED := $(and $(FINDFILTERONLYEXTENDED),$(FINDFILTEROUTEXTENDED),1)
+