# - If the content differ the new file is used
# - If they are equal no change, and no timestamp update
define filechk
+ $(check-FORCE)
$(Q)set -e; \
mkdir -p $(dir $@); \
trap "rm -f $(dot-target).tmp" EXIT; \
# PHONY targets skipped in both cases.
newer-prereqs = $(filter-out $(PHONY),$?)
-if-changed-cond = $(newer-prereqs)$(cmd-check)
+# It is a typical mistake to forget the FORCE prerequisite. Check it here so
+# no more breakage will slip in.
+check-FORCE = $(if $(filter FORCE, $^),,$(warning FORCE prerequisite is missing))
+
+if-changed-cond = $(newer-prereqs)$(cmd-check)$(check-FORCE)
# Execute command if command has changed or prerequisite(s) are updated.
if_changed = $(if $(if-changed-cond), \