On Friday, 2021-08-13 Masahiro Yamada wrote: > 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 prerequsite -> prerequisite? Successfully found the missing FORCE in arch/x86/entry/vdso/Makefile:135. Tested-by: Nicolas Schier <n.schier@xxxxxx> > +# 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 >
