+# To use this "command" macro, you must first define two shell variables:
+# h: the header, enclosed in <> or ""
+# re: a regular expression that matches IFF something provided by $h is used.
+define _header_without_use
+ h_esc=`echo "$$h"|sed 's/\./\\./g'`; \
+ if $(C_SOURCES) | grep -l '\.c$$' > /dev/null; then \
+ files=$$(grep -l '^# *include '"$$h_esc" \
+ $$($(C_SOURCES) | grep '\.c$$')) && \
+ grep -LE "$$re" $$files | grep . && \
+ { echo "$(ME): the above files include $$h but don't use it" \
+ 1>&2; exit 1; } || :; \
+ else :; \
+ fi
+endef
+