mirror of
https://github.com/torvalds/linux
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913ab9780f
To print the pathname that will be used by shell in the current environment, 'command -v' is a standardized way. [1] 'which' is also often used in scripts, but it is less portable. When I worked on commitbd55f96fa9("kbuild: refactor cc-cross-prefix implementation"), I was eager to use 'command -v' but it did not work. (The reason is explained below.) I kept 'which' as before but got rid of '> /dev/null 2>&1' as I thought it was no longer needed. Sorry, I was wrong. It works well on my Ubuntu machine, but Alexey Brodkin reports noisy warnings on CentOS7 when 'which' fails to find the given command in the PATH environment. $ which foo which: no foo in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin) Given that behavior of 'which' depends on system (and it may not be installed by default), I want to try 'command -v' once again. The specification [1] clearly describes the behavior of 'command -v' when the given command is not found: Otherwise, no output shall be written and the exit status shall reflect that the name was not found. However, we need a little magic to use 'command -v' from Make. $(shell ...) passes the argument to a subshell for execution, and returns the standard output of the command. Here is a trick. GNU Make may optimize this by executing the command directly instead of forking a subshell, if no shell special characters are found in the command and omitting the subshell will not change the behavior. In this case, no shell special character is used. So, Make will try to run it directly. However, 'command' is a shell-builtin command, then Make would fail to find it in the PATH environment: $ make ARCH=m68k defconfig make: command: Command not found make: command: Command not found make: command: Command not found In fact, Make has a table of shell-builtin commands because it must ask the shell to execute them. Until recently, 'command' was missing in the table. This issue was fixed by the following commit: | commit 1af314465e5dfe3e8baa839a32a72e83c04f26ef | Author: Paul Smith <psmith@gnu.org> | Date: Sun Nov 12 18:10:28 2017 -0500 | | * job.c: Add "command" as a known shell built-in. | | This is not a POSIX shell built-in but it's common in UNIX shells. | Reported by Nick Bowler <nbowler@draconx.ca>. Because the latest release is GNU Make 4.2.1 in 2016, this commit is not included in any released versions. (But some distributions may have back-ported it.) We need to trick Make to spawn a subshell. There are various ways to do so: 1) Use a shell special character '~' as dummy $(shell : ~; command -v $(c)gcc) 2) Use a variable reference that always expands to the empty string (suggested by David Laight) $(shell command$${x:+} -v $(c)gcc) 3) Use redirect $(shell command -v $(c)gcc 2>/dev/null) I chose 3) to not confuse people. The stderr would not be polluted anyway, but it will provide extra safety, and is easy to understand. Tested on Make 3.81, 3.82, 4.0, 4.1, 4.2, 4.2.1 [1] http://pubs.opengroup.org/onlinepubs/9699919799/utilities/command.html Fixes:bd55f96fa9("kbuild: refactor cc-cross-prefix implementation") Cc: linux-stable <stable@vger.kernel.org> # 5.1 Reported-by: Alexey Brodkin <abrodkin@synopsys.com> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Tested-by: Alexey Brodkin <abrodkin@synopsys.com>
347 lines
13 KiB
Text
347 lines
13 KiB
Text
# 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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###
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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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# 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),_,$(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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# 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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# - 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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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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$(kecho) ' 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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# cc-cross-prefix
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# Usage: CROSS_COMPILE := $(call cc-cross-prefix, m68k-linux-gnu- m68k-linux-)
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# Return first <prefix> where a <prefix>gcc is found in PATH.
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# If no gcc found in PATH with listed prefixes return nothing
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#
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# Note: '2>/dev/null' is here to force Make to invoke a shell. Otherwise, it
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# would try to directly execute the shell builtin 'command'. This workaround
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# should be kept for a long time since this issue was fixed only after the
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# GNU Make 4.2.1 release.
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cc-cross-prefix = $(firstword $(foreach c, $(filter-out -%, $(1)), \
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$(if $(shell command -v $(c)gcc 2>/dev/null), $(c))))
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# output directory for tests below
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TMPOUT := $(if $(KBUILD_EXTMOD),$(firstword $(KBUILD_EXTMOD))/)
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# try-run
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# Usage: option = $(call try-run, $(CC)...-o "$$TMP",option-ok,otherwise)
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# Exit code chooses option. "$$TMP" serves as a temporary file and is
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# automatically cleaned up.
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try-run = $(shell set -e; \
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TMP="$(TMPOUT).$$$$.tmp"; \
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TMPO="$(TMPOUT).$$$$.o"; \
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if ($(1)) >/dev/null 2>&1; \
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then echo "$(2)"; \
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else echo "$(3)"; \
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fi; \
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rm -f "$$TMP" "$$TMPO")
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# as-option
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# Usage: cflags-y += $(call as-option,-Wa$(comma)-isa=foo,)
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as-option = $(call try-run,\
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$(CC) $(KBUILD_CFLAGS) $(1) -c -x assembler /dev/null -o "$$TMP",$(1),$(2))
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# as-instr
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# Usage: cflags-y += $(call as-instr,instr,option1,option2)
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as-instr = $(call try-run,\
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printf "%b\n" "$(1)" | $(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" -,$(2),$(3))
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# __cc-option
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# Usage: MY_CFLAGS += $(call __cc-option,$(CC),$(MY_CFLAGS),-march=winchip-c6,-march=i586)
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__cc-option = $(call try-run,\
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$(1) -Werror $(2) $(3) -c -x c /dev/null -o "$$TMP",$(3),$(4))
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# Do not attempt to build with gcc plugins during cc-option tests.
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# (And this uses delayed resolution so the flags will be up to date.)
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CC_OPTION_CFLAGS = $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS))
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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 = $(call __cc-option, $(CC),\
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$(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS),$(1),$(2))
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# hostcc-option
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# Usage: cflags-y += $(call hostcc-option,-march=winchip-c6,-march=i586)
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hostcc-option = $(call __cc-option, $(HOSTCC),\
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$(KBUILD_HOSTCFLAGS) $(HOST_EXTRACFLAGS),$(1),$(2))
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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 = $(call try-run,\
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$(CC) -Werror $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) $(1) -c -x c /dev/null -o "$$TMP",y,n)
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# cc-disable-warning
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# Usage: cflags-y += $(call cc-disable-warning,unused-but-set-variable)
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cc-disable-warning = $(call try-run,\
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$(CC) -Werror $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) -W$(strip $(1)) -c -x c /dev/null -o "$$TMP",-Wno-$(strip $(1)))
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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 [ $(CONFIG_GCC_VERSION)0 $(1) $(2)000 ] && echo $(3) || echo $(4))
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# ld-option
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# Usage: KBUILD_LDFLAGS += $(call ld-option, -X, -Y)
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ld-option = $(call try-run, $(LD) $(KBUILD_LDFLAGS) $(1) -v,$(1),$(2),$(3))
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# ar-option
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# Usage: KBUILD_ARFLAGS := $(call ar-option,D)
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# Important: no spaces around options
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ar-option = $(call try-run, $(AR) rc$(1) "$$TMP",$(1),$(2))
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# ld-version
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# Note this is mainly for HJ Lu's 3 number binutil versions
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ld-version = $(shell $(LD) --version | $(srctree)/scripts/ld-version.sh)
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# ld-ifversion
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# Usage: $(call ld-ifversion, -ge, 22252, y)
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ld-ifversion = $(shell [ $(ld-version) $(1) $(2) ] && echo $(3) || echo $(4))
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######
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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.modbuiltin obj=
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# Usage:
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# $(Q)$(MAKE) $(modbuiltin)=dir
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modbuiltin := -f $(srctree)/scripts/Makefile.modbuiltin 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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###
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# Shorthand for $(Q)$(MAKE) -f scripts/Makefile.headersinst obj=
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# Usage:
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# $(Q)$(MAKE) $(hdr-inst)=dir
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hdr-inst := -f $(srctree)/scripts/Makefile.headersinst obj
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# echo command.
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# Short version is used, if $(quiet) equals `quiet_', otherwise full one.
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echo-cmd = $(if $($(quiet)cmd_$(1)),\
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echo ' $(call escsq,$($(quiet)cmd_$(1)))$(echo-why)';)
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# printing commands
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cmd = @set -e; $(echo-cmd) $(cmd_$(1))
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# Add $(obj)/ for paths that are 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 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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arg-check = $(filter-out $(subst $(space),$(space_escape),$(strip $(cmd_$@))), \
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$(subst $(space),$(space_escape),$(strip $(cmd_$1))))
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else
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arg-check = $(if $(strip $(cmd_$@)),,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 is newer than target or that does not exist.
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# PHONY targets skipped in both cases.
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any-prereq = $(filter-out $(PHONY),$?) $(filter-out $(PHONY) $(wildcard $^),$^)
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# Execute command if command has changed or prerequisite(s) are updated.
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if_changed = $(if $(strip $(any-prereq) $(arg-check)), \
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$(cmd); \
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printf '%s\n' 'cmd_$@ := $(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 $(strip $(any-prereq) $(arg-check)),$(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 $(strip $(any-prereq) $(arg-check)),$(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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ifeq ($(KBUILD_VERBOSE),2)
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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 $(strip $(any-prereq)),- due to: $(any-prereq), \
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$(if $(arg-check), \
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$(if $(cmd_$@),- 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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echo-why = $(call escsq, $(strip $(why)))
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endif
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###############################################################################
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#
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# When a Kconfig string contains a filename, it is suitable for
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# passing to shell commands. It is surrounded by double-quotes, and
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# any double-quotes or backslashes within it are escaped by
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# backslashes.
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#
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# This is no use for dependencies or $(wildcard). We need to strip the
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# surrounding quotes and the escaping from quotes and backslashes, and
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# we *do* need to escape any spaces in the string. So, for example:
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#
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# Usage: $(eval $(call config_filename,FOO))
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#
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# Defines FOO_FILENAME based on the contents of the CONFIG_FOO option,
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# transformed as described above to be suitable for use within the
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# makefile.
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#
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# Also, if the filename is a relative filename and exists in the source
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# tree but not the build tree, define FOO_SRCPREFIX as $(srctree)/ to
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# be prefixed to *both* command invocation and dependencies.
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#
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# Note: We also print the filenames in the quiet_cmd_foo text, and
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# perhaps ought to have a version specially escaped for that purpose.
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# But it's only cosmetic, and $(patsubst "%",%,$(CONFIG_FOO)) is good
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# enough. It'll strip the quotes in the common case where there's no
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# space and it's a simple filename, and it'll retain the quotes when
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# there's a space. There are some esoteric cases in which it'll print
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# the wrong thing, but we don't really care. The actual dependencies
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# and commands *do* get it right, with various combinations of single
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# and double quotes, backslashes and spaces in the filenames.
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#
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###############################################################################
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#
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define config_filename
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ifneq ($$(CONFIG_$(1)),"")
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$(1)_FILENAME := $$(subst \\,\,$$(subst \$$(quote),$$(quote),$$(subst $$(space_escape),\$$(space),$$(patsubst "%",%,$$(subst $$(space),$$(space_escape),$$(CONFIG_$(1)))))))
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ifneq ($$(patsubst /%,%,$$(firstword $$($(1)_FILENAME))),$$(firstword $$($(1)_FILENAME)))
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else
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ifeq ($$(wildcard $$($(1)_FILENAME)),)
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ifneq ($$(wildcard $$(srctree)/$$($(1)_FILENAME)),)
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$(1)_SRCPREFIX := $(srctree)/
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endif
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endif
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endif
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endif
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endef
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#
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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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.SECONDARY:
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