4f1933620f
The kbuild system takes advantage of an incorrect behavior in GNU make. Once this behavior is fixed, all files in the kernel rebuild every time, even if nothing has changed. This patch ensures kbuild works with both the incorrect and correct behaviors of GNU make. For more details on the incorrect behavior, see: http://lists.gnu.org/archive/html/bug-make/2006-03/msg00003.html Changes in this patch: - Keep all targets that are to be marked .PHONY in a variable, PHONY. - Add .PHONY: $(PHONY) to mark them properly. - Remove any $(PHONY) files from the $? list when determining whether targets are up-to-date or not. Signed-off-by: Paul Smith <psmith@gnu.org> Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
144 lines
4.8 KiB
Plaintext
144 lines
4.8 KiB
Plaintext
####
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# kbuild: Generic definitions
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# Convinient variables
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comma := ,
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squote := '
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empty :=
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space := $(empty) $(empty)
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###
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# The temporary file to save gcc -MD generated dependencies must not
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# contain a comma
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depfile = $(subst $(comma),_,$(@D)/.$(@F).d)
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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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# filechk is used to check if the content of a generated file is updated.
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# Sample usage:
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# define filechk_sample
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# echo $KERNELRELEASE
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# endef
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# version.h : Makefile
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# $(call filechk,sample)
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# The rule defined shall write to stdout the content of the new file.
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# The existing file will be compared with the new one.
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# - If no file exist it is created
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# - If the content differ the new file is used
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# - If they are equal no change, and no timestamp update
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# - stdin is piped in from the first prerequisite ($<) so one has
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# to specify a valid file as first prerequisite (often the kbuild file)
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define filechk
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$(Q)set -e; \
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echo ' CHK $@'; \
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mkdir -p $(dir $@); \
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$(filechk_$(1)) < $< > $@.tmp; \
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if [ -r $@ ] && cmp -s $@ $@.tmp; then \
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rm -f $@.tmp; \
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else \
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echo ' UPD $@'; \
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mv -f $@.tmp $@; \
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fi
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endef
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######
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# gcc support functions
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# See documentation in Documentation/kbuild/makefiles.txt
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# as-option
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# Usage: cflags-y += $(call as-option, -Wa$(comma)-isa=foo,)
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as-option = $(shell if $(CC) $(CFLAGS) $(1) -Wa,-Z -c -o /dev/null \
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-xassembler /dev/null > /dev/null 2>&1; then echo "$(1)"; \
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else echo "$(2)"; fi ;)
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# cc-option
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# Usage: cflags-y += $(call cc-option, -march=winchip-c6, -march=i586)
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cc-option = $(shell if $(CC) $(CFLAGS) $(1) -S -o /dev/null -xc /dev/null \
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> /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
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# cc-option-yn
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# Usage: flag := $(call cc-option-yn, -march=winchip-c6)
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cc-option-yn = $(shell if $(CC) $(CFLAGS) $(1) -S -o /dev/null -xc /dev/null \
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> /dev/null 2>&1; then echo "y"; else echo "n"; fi;)
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# cc-option-align
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# Prefix align with either -falign or -malign
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cc-option-align = $(subst -functions=0,,\
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$(call cc-option,-falign-functions=0,-malign-functions=0))
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# cc-version
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# Usage gcc-ver := $(call cc-version, $(CC))
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cc-version = $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-version.sh \
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$(if $(1), $(1), $(CC)))
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# cc-ifversion
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# Usage: EXTRA_CFLAGS += $(call cc-ifversion, -lt, 0402, -O1)
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cc-ifversion = $(shell if [ $(call cc-version, $(CC)) $(1) $(2) ]; then \
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echo $(3); fi;)
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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 $(if $(KBUILD_SRC),$(srctree)/)scripts/Makefile.build obj
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# If quiet is set, only print short version of command
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cmd = @$(echo-cmd) $(cmd_$(1))
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# Add $(obj)/ for paths that is not absolute
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objectify = $(foreach o,$(1),$(if $(filter /%,$(o)),$(o),$(obj)/$(o)))
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###
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# if_changed - execute command if any prerequisite is newer than
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# target, or command line has changed
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# if_changed_dep - as if_changed, but uses fixdep to reveal dependencies
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# including used config symbols
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# if_changed_rule - as if_changed but execute rule instead
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# See Documentation/kbuild/makefiles.txt for more info
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ifneq ($(KBUILD_NOCMDDEP),1)
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# Check if both arguments has same arguments. Result in empty string if equal
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# User may override this check using make KBUILD_NOCMDDEP=1
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arg-check = $(strip $(filter-out $(1), $(2)) $(filter-out $(2), $(1)) )
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endif
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# echo command. Short version is $(quiet) equals quiet, otherwise full command
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echo-cmd = $(if $($(quiet)cmd_$(1)), \
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echo ' $(call escsq,$($(quiet)cmd_$(1)))';)
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make-cmd = $(subst \#,\\\#,$(subst $$,$$$$,$(call escsq,$(cmd_$(1)))))
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# function to only execute the passed command if necessary
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# >'< substitution is for echo to work, >$< substitution to preserve $ when reloading .cmd file
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# note: when using inline perl scripts [perl -e '...$$t=1;...'] in $(cmd_xxx) double $$ your perl vars
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#
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if_changed = $(if $(strip $(filter-out $(PHONY),$?) \
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$(call arg-check, $(cmd_$(1)), $(cmd_$@)) ), \
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@set -e; \
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$(echo-cmd) $(cmd_$(1)); \
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echo 'cmd_$@ := $(make-cmd)' > $(@D)/.$(@F).cmd)
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# execute the command and also postprocess generated .d dependencies
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# file
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if_changed_dep = $(if $(strip $(filter-out $(PHONY),$?) \
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$(filter-out FORCE $(wildcard $^),$^) \
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$(call arg-check, $(cmd_$(1)), $(cmd_$@)) ), \
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@set -e; \
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$(echo-cmd) $(cmd_$(1)); \
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scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(@D)/.$(@F).tmp; \
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rm -f $(depfile); \
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mv -f $(@D)/.$(@F).tmp $(@D)/.$(@F).cmd)
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# Usage: $(call if_changed_rule,foo)
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# will check if $(cmd_foo) changed, or any of the prequisites changed,
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# and if so will execute $(rule_foo)
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if_changed_rule = $(if $(strip $(filter-out $(PHONY),$?) \
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$(call arg-check, $(cmd_$(1)), $(cmd_$@)) ),\
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@set -e; \
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$(rule_$(1)))
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