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ee2162bd4f
The cmd-check for KBUILD_NOCMDDEP=1 may not be clear until you see
commit c4d5ee1398 ("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>
280 lines
10 KiB
Plaintext
280 lines
10 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0
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####
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# kbuild: Generic definitions
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# Convenient variables
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comma := ,
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quote := "
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squote := '
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empty :=
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space := $(empty) $(empty)
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space_escape := _-_SPACE_-_
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pound := \#
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define newline
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endef
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###
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# Comparison macros.
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# Usage: $(call test-lt, $(CONFIG_LLD_VERSION), 150000)
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#
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# Use $(intcmp ...) if supported. (Make >= 4.4)
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# Otherwise, fall back to the 'test' shell command.
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ifeq ($(intcmp 1,0,,,y),y)
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test-ge = $(intcmp $(strip $1)0, $(strip $2)0,,y,y)
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test-gt = $(intcmp $(strip $1)0, $(strip $2)0,,,y)
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else
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test-ge = $(shell test $(strip $1)0 -ge $(strip $2)0 && echo y)
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test-gt = $(shell test $(strip $1)0 -gt $(strip $2)0 && echo y)
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endif
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test-le = $(call test-ge, $2, $1)
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test-lt = $(call test-gt, $2, $1)
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###
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# Name of target with a '.' as filename prefix. foo/bar.o => foo/.bar.o
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dot-target = $(dir $@).$(notdir $@)
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###
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# Name of target with a '.tmp_' as filename prefix. foo/bar.o => foo/.tmp_bar.o
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tmp-target = $(dir $@).tmp_$(notdir $@)
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###
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# The temporary file to save gcc -MMD generated dependencies must not
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# contain a comma
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depfile = $(subst $(comma),_,$(dot-target).d)
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###
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# filename of target with directory and extension stripped
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basetarget = $(basename $(notdir $@))
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###
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# real prerequisites without phony targets
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real-prereqs = $(filter-out $(PHONY), $^)
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###
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# Escape single quote for use in echo statements
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escsq = $(subst $(squote),'\$(squote)',$1)
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###
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# Quote a string to pass it to C files. foo => '"foo"'
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stringify = $(squote)$(quote)$1$(quote)$(squote)
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###
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# The path to Kbuild or Makefile. Kbuild has precedence over Makefile.
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kbuild-dir = $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
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kbuild-file = $(or $(wildcard $(kbuild-dir)/Kbuild),$(kbuild-dir)/Makefile)
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###
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# Read a file, replacing newlines with spaces
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#
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# Make 4.2 or later can read a file by using its builtin function.
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ifneq ($(filter-out 3.% 4.0 4.1, $(MAKE_VERSION)),)
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read-file = $(subst $(newline),$(space),$(file < $1))
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else
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read-file = $(shell cat $1 2>/dev/null)
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endif
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###
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# Easy method for doing a status message
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kecho := :
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quiet_kecho := echo
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silent_kecho := :
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kecho := $($(quiet)kecho)
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###
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# filechk is used to check if the content of a generated file is updated.
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# Sample usage:
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#
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# filechk_sample = echo $(KERNELRELEASE)
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# version.h: FORCE
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# $(call filechk,sample)
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#
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# The rule defined shall write to stdout the content of the new file.
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# The existing file will be compared with the new one.
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# - If no file exist it is created
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# - If the content differ the new file is used
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# - If they are equal no change, and no timestamp update
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define filechk
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$(check-FORCE)
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$(Q)set -e; \
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mkdir -p $(dir $@); \
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trap "rm -f $(dot-target).tmp" EXIT; \
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{ $(filechk_$(1)); } > $(dot-target).tmp; \
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if [ ! -r $@ ] || ! cmp -s $@ $(dot-target).tmp; then \
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$(kecho) ' UPD $@'; \
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mv -f $(dot-target).tmp $@; \
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fi
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endef
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###
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# Shorthand for $(Q)$(MAKE) -f scripts/Makefile.build obj=
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# Usage:
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# $(Q)$(MAKE) $(build)=dir
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build := -f $(srctree)/scripts/Makefile.build obj
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###
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# Shorthand for $(Q)$(MAKE) -f scripts/Makefile.dtbinst obj=
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# Usage:
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# $(Q)$(MAKE) $(dtbinst)=dir
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dtbinst := -f $(srctree)/scripts/Makefile.dtbinst obj
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###
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# Shorthand for $(Q)$(MAKE) -f scripts/Makefile.clean obj=
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# Usage:
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# $(Q)$(MAKE) $(clean)=dir
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clean := -f $(srctree)/scripts/Makefile.clean obj
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# pring log
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#
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# If quiet is "silent_", print nothing and sink stdout
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# If quiet is "quiet_", print short log
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# If quiet is empty, print short log and whole command
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silent_log_print = exec >/dev/null;
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quiet_log_print = $(if $(quiet_cmd_$1), echo ' $(call escsq,$(quiet_cmd_$1)$(why))';)
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log_print = echo '$(pound) $(call escsq,$(or $(quiet_cmd_$1),cmd_$1 $@)$(why))'; \
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echo ' $(call escsq,$(cmd_$1))';
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# Delete the target on interruption
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#
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# GNU Make automatically deletes the target if it has already been changed by
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# the interrupted recipe. So, you can safely stop the build by Ctrl-C (Make
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# will delete incomplete targets), and resume it later.
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#
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# However, this does not work when the stderr is piped to another program, like
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# $ make >&2 | tee log
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# Make dies with SIGPIPE before cleaning the targets.
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#
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# To address it, we clean the target in signal traps.
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#
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# Make deletes the target when it catches SIGHUP, SIGINT, SIGQUIT, SIGTERM.
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# So, we cover them, and also SIGPIPE just in case.
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#
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# Of course, this is unneeded for phony targets.
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delete-on-interrupt = \
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$(if $(filter-out $(PHONY), $@), \
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$(foreach sig, HUP INT QUIT TERM PIPE, \
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trap 'rm -f $@; trap - $(sig); kill -s $(sig) $$$$' $(sig);))
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# print and execute commands
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cmd = @$(if $(cmd_$(1)),set -e; $($(quiet)log_print) $(delete-on-interrupt) $(cmd_$(1)),:)
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###
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# if_changed - execute command if any prerequisite is newer than
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# target, or command line has changed
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# if_changed_dep - as if_changed, but uses fixdep to reveal dependencies
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# including used config symbols
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# if_changed_rule - as if_changed but execute rule instead
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# See Documentation/kbuild/makefiles.rst for more info
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ifneq ($(KBUILD_NOCMDDEP),1)
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# Check if both commands are the same including their order. Result is empty
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# string if equal. User may override this check using make KBUILD_NOCMDDEP=1
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# If the target does not exist, the *.cmd file should not be included so
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# $(savedcmd_$@) gets empty. Then, target will be built even if $(newer-prereqs)
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# happens to become empty.
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cmd-check = $(filter-out $(subst $(space),$(space_escape),$(strip $(savedcmd_$@))), \
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$(subst $(space),$(space_escape),$(strip $(cmd_$1))))
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else
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# We still need to detect missing targets.
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cmd-check = $(if $(strip $(savedcmd_$@)),,1)
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endif
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# Replace >$< with >$$< to preserve $ when reloading the .cmd file
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# (needed for make)
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# Replace >#< with >$(pound)< to avoid starting a comment in the .cmd file
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# (needed for make)
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# Replace >'< with >'\''< to be able to enclose the whole string in '...'
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# (needed for the shell)
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make-cmd = $(call escsq,$(subst $(pound),$$(pound),$(subst $$,$$$$,$(cmd_$(1)))))
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# Find any prerequisites that are newer than target or that do not exist.
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# PHONY targets skipped in both cases.
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# If there is no prerequisite other than phony targets, $(newer-prereqs) becomes
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# empty even if the target does not exist. cmd-check saves this corner case.
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newer-prereqs = $(filter-out $(PHONY),$?)
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# It is a typical mistake to forget the FORCE prerequisite. Check it here so
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# no more breakage will slip in.
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check-FORCE = $(if $(filter FORCE, $^),,$(warning FORCE prerequisite is missing))
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if-changed-cond = $(newer-prereqs)$(cmd-check)$(check-FORCE)
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# Execute command if command has changed or prerequisite(s) are updated.
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if_changed = $(if $(if-changed-cond),$(cmd_and_savecmd),@:)
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cmd_and_savecmd = \
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$(cmd); \
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printf '%s\n' 'savedcmd_$@ := $(make-cmd)' > $(dot-target).cmd
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# Execute the command and also postprocess generated .d dependencies file.
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if_changed_dep = $(if $(if-changed-cond),$(cmd_and_fixdep),@:)
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cmd_and_fixdep = \
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$(cmd); \
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scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).cmd;\
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rm -f $(depfile)
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# Usage: $(call if_changed_rule,foo)
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# Will check if $(cmd_foo) or any of the prerequisites changed,
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# and if so will execute $(rule_foo).
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if_changed_rule = $(if $(if-changed-cond),$(rule_$(1)),@:)
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###
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# why - tell why a target got built
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# enabled by make V=2
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# Output (listed in the order they are checked):
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# (1) - due to target is PHONY
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# (2) - due to target missing
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# (3) - due to: file1.h file2.h
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# (4) - due to command line change
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# (5) - due to missing .cmd file
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# (6) - due to target not in $(targets)
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# (1) PHONY targets are always build
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# (2) No target, so we better build it
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# (3) Prerequisite is newer than target
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# (4) The command line stored in the file named dir/.target.cmd
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# differed from actual command line. This happens when compiler
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# options changes
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# (5) No dir/.target.cmd file (used to store command line)
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# (6) No dir/.target.cmd file and target not listed in $(targets)
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# This is a good hint that there is a bug in the kbuild file
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ifneq ($(findstring 2, $(KBUILD_VERBOSE)),)
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_why = \
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$(if $(filter $@, $(PHONY)),- due to target is PHONY, \
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$(if $(wildcard $@), \
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$(if $(newer-prereqs),- due to: $(newer-prereqs), \
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$(if $(cmd-check), \
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$(if $(savedcmd_$@),- due to command line change, \
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$(if $(filter $@, $(targets)), \
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- due to missing .cmd file, \
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- due to $(notdir $@) not in $$(targets) \
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) \
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) \
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) \
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), \
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- due to target missing \
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) \
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)
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why = $(space)$(strip $(_why))
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endif
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###############################################################################
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# delete partially updated (i.e. corrupted) files on error
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.DELETE_ON_ERROR:
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# do not delete intermediate files automatically
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#
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# .NOTINTERMEDIATE is more correct, but only available on newer Make versions.
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# Make 4.4 introduced .NOTINTERMEDIATE, and it appears in .FEATURES, but the
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# global .NOTINTERMEDIATE does not work. We can use it on Make > 4.4.
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# Use .SECONDARY for older Make versions, but "newer-prereq" cannot detect
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# deleted files.
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ifneq ($(and $(filter notintermediate, $(.FEATURES)),$(filter-out 4.4,$(MAKE_VERSION))),)
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.NOTINTERMEDIATE:
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else
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.SECONDARY:
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endif
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