if_changed, if_changed_dep, and if_changed_rule must have FORCE as a prerequisite so the command line change is detected. Documentation/kbuild/makefiles.rst clearly explains it: Note: It is a typical mistake to forget the FORCE prerequisite. However, not all people read the document, or understand what is written in it. People repeated this mistake over again, and I determined a compelling force is needed. Show a warning if FORCE is missing in the prerequisite of if_changed and friends. Same for filechk. Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> --- scripts/Kbuild.include | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include index c3c975a92318..dd48e68965f8 100644 --- a/scripts/Kbuild.include +++ b/scripts/Kbuild.include @@ -57,6 +57,7 @@ kecho := $($(quiet)kecho) # - 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; \ @@ -130,7 +131,11 @@ make-cmd = $(call escsq,$(subst $(pound),$$(pound),$(subst $$,$$$$,$(cmd_$(1)))) # 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 prerequsite 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), \ -- 2.30.2
