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Subject[PATCH] kbuild: consistently decide when to rebuild a target
Date
From: Sam Ravnborg <sam@mars.ravnborg.org>

Consistently decide when to rebuild a target across all of
if_changed, if_changed_dep, if_changed_rule.
PHONY targets are now treated alike (ignored) for all targets

While add it make Kbuild.include almost readable by factoring out a few
bits to some common variables and reuse this in Makefile.build.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
---
scripts/Kbuild.include | 52 ++++++++++++++++++++++++++++--------------------
scripts/Makefile.build | 5 +++--
usr/Makefile | 2 ++
3 files changed, 35 insertions(+), 24 deletions(-)
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 2180c88..7a18353 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -8,9 +8,13 @@ empty :=
space := $(empty) $(empty)

###
+# Name of target with a '.' as filename prefix. foo/bar.o => foo/.bar.o
+dot-target = $(dir $@).$(notdir $@)
+
+###
# The temporary file to save gcc -MD generated dependencies must not
# contain a comma
-depfile = $(subst $(comma),_,$(@D)/.$(@F).d)
+depfile = $(subst $(comma),_,$(dot-target).d)

###
# filename of target with directory and extension stripped
@@ -113,40 +117,44 @@ # See Documentation/kbuild/makefiles.txt
ifneq ($(KBUILD_NOCMDDEP),1)
# Check if both arguments has same arguments. Result in empty string if equal
# User may override this check using make KBUILD_NOCMDDEP=1
-arg-check = $(strip $(filter-out $(1), $(2)) $(filter-out $(2), $(1)) )
+arg-check = $(strip $(filter-out $(cmd_$(1)), $(cmd_$@)) \
+ $(filter-out $(cmd_$@), $(cmd_$(1))) )
endif

# echo command. Short version is $(quiet) equals quiet, otherwise full command
echo-cmd = $(if $($(quiet)cmd_$(1)), \
echo ' $(call escsq,$($(quiet)cmd_$(1)))';)

+# >'< substitution is for echo to work,
+# >$< substitution to preserve $ when reloading .cmd file
+# note: when using inline perl scripts [perl -e '...$$t=1;...']
+# in $(cmd_xxx) double $$ your perl vars
make-cmd = $(subst \#,\\\#,$(subst $$,$$$$,$(call escsq,$(cmd_$(1)))))

-# function to only execute the passed command if necessary
-# >'< substitution is for echo to work, >$< substitution to preserve $ when reloading .cmd file
-# note: when using inline perl scripts [perl -e '...$$t=1;...'] in $(cmd_xxx) double $$ your perl vars
+# Find any prerequisites that is newer than target or that does not exist.
+# PHONY targets skipped in both cases.
+any-prereq = $(filter-out $(PHONY),$?) $(filter-out $(PHONY) $(wildcard $^),$^)
+
+# Execute command if command has changed or prerequisitei(s) are updated
#
-if_changed = $(if $(strip $(filter-out $(PHONY),$?) \
- $(call arg-check, $(cmd_$(1)), $(cmd_$@)) ), \
- @set -e; \
- $(echo-cmd) $(cmd_$(1)); \
- echo 'cmd_$@ := $(make-cmd)' > $(@D)/.$(@F).cmd)
+if_changed = $(if $(strip $(any-prereq) $(arg-check)), \
+ @set -e; \
+ $(echo-cmd) $(cmd_$(1)); \
+ echo 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd)

# execute the command and also postprocess generated .d dependencies
# file
-if_changed_dep = $(if $(strip $(filter-out $(PHONY),$?) \
- $(filter-out FORCE $(wildcard $^),$^) \
- $(call arg-check, $(cmd_$(1)), $(cmd_$@)) ), \
- @set -e; \
- $(echo-cmd) $(cmd_$(1)); \
- scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(@D)/.$(@F).tmp; \
- rm -f $(depfile); \
- mv -f $(@D)/.$(@F).tmp $(@D)/.$(@F).cmd)
+if_changed_dep = $(if $(strip $(any-prereq) $(arg-check) ), \
+ @set -e; \
+ $(echo-cmd) $(cmd_$(1)); \
+ scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).tmp;\
+ rm -f $(depfile); \
+ mv -f $(dot-target).tmp $(dot-target).cmd)

# Usage: $(call if_changed_rule,foo)
# will check if $(cmd_foo) changed, or any of the prequisites changed,
# and if so will execute $(rule_foo)
-if_changed_rule = $(if $(strip $(filter-out $(PHONY),$?) \
- $(call arg-check, $(cmd_$(1)), $(cmd_$@)) ),\
- @set -e; \
- $(rule_$(1)))
+if_changed_rule = $(if $(strip $(any-prereq) $(arg-check) ), \
+ @set -e; \
+ $(rule_$(1)))
+
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 3cb445c..e2ad2dc 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -191,9 +191,10 @@ define rule_cc_o_c
$(call echo-cmd,checksrc) $(cmd_checksrc) \
$(call echo-cmd,cc_o_c) $(cmd_cc_o_c); \
$(cmd_modversions) \
- scripts/basic/fixdep $(depfile) $@ '$(call make-cmd,cc_o_c)' > $(@D)/.$(@F).tmp; \
+ scripts/basic/fixdep $(depfile) $@ '$(call make-cmd,cc_o_c)' > \
+ $(dot-target).tmp; \
rm -f $(depfile); \
- mv -f $(@D)/.$(@F).tmp $(@D)/.$(@F).cmd
+ mv -f $(dot-target).tmp $(dot-target).cmd
endef

# Built-in and composite module parts
diff --git a/usr/Makefile b/usr/Makefile
index e938242..2c8f362 100644
--- a/usr/Makefile
+++ b/usr/Makefile
@@ -3,6 +3,8 @@ # kbuild file for usr/ - including initr
#

klibcdirs:;
+PHONY += klibcdirs
+

# Generate builtin.o based on initramfs_data.o
obj-y := initramfs_data.o
--
1.4.1.rc2.gfc04
-
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