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kbuild: warn if FORCE is missing for if_changed(_dep,_rule) and filechk

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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 follow the document.

This mistake occurred again and again, so 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@kernel.org>
Tested-by: Nicolas Schier <n.schier@avm.de>
This commit is contained in:
Masahiro Yamada 2021-08-13 15:30:05 +09:00
parent 6796e80409
commit e1f86d7b4b
1 changed files with 6 additions and 1 deletions
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7
scripts/Kbuild.include
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@ -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 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), \