diff options
| author | Masahiro Yamada <masahiroy@kernel.org> | 2022-12-29 18:15:01 +0900 |
|---|---|---|
| committer | Masahiro Yamada <masahiroy@kernel.org> | 2023-01-22 23:43:33 +0900 |
| commit | ee2162bd4fe85a62dcd3b9133fd0c537ae2eb3c5 (patch) | |
| tree | afb5efd76b899888940f207786914ae3943a4c7d | |
| parent | 92215e7a801da7b89037a185c98f5ebb86a415b9 (diff) | |
kbuild: add more comments for KBUILD_NOCMDDEP=1
The cmd-check for KBUILD_NOCMDDEP=1 may not be clear until you see
commit c4d5ee13984f ("kbuild: make KBUILD_NOCMDDEP=1 handle empty
built-in.o").
When a phony target (i.e. FORCE) is the only prerequisite, Kbuild
uses a tricky way to detect that the target does not exist.
Add more comments.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
| -rw-r--r-- | scripts/Kbuild.include | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include index 1a7514f49089..4648ab8f11d4 100644 --- a/scripts/Kbuild.include +++ b/scripts/Kbuild.include @@ -170,9 +170,13 @@ cmd = @$(if $(cmd_$(1)),set -e; $($(quiet)log_print) $(delete-on-interrupt) $(cm ifneq ($(KBUILD_NOCMDDEP),1) # Check if both commands are the same including their order. Result is empty # string if equal. User may override this check using make KBUILD_NOCMDDEP=1 +# If the target does not exist, the *.cmd file should not be included so +# $(savedcmd_$@) gets empty. Then, target will be built even if $(newer-prereqs) +# happens to become empty. cmd-check = $(filter-out $(subst $(space),$(space_escape),$(strip $(savedcmd_$@))), \ $(subst $(space),$(space_escape),$(strip $(cmd_$1)))) else +# We still need to detect missing targets. cmd-check = $(if $(strip $(savedcmd_$@)),,1) endif @@ -186,6 +190,8 @@ make-cmd = $(call escsq,$(subst $(pound),$$(pound),$(subst $$,$$$$,$(cmd_$(1)))) # Find any prerequisites that are newer than target or that do not exist. # PHONY targets skipped in both cases. +# If there is no prerequisite other than phony targets, $(newer-prereqs) becomes +# empty even if the target does not exist. cmd-check saves this corner case. newer-prereqs = $(filter-out $(PHONY),$?) # It is a typical mistake to forget the FORCE prerequisite. Check it here so |