kbuild: make cc-version available in kbuild files
Move $(CC) support functions to Kbuild.include so they are available in the kbuild files. In addition the following was done: o as-option documented in Documentation/kbuild/makefiles.txt o Moved documentation to new section to match new scope of functions o added cc-ifversion used to conditionally select a text string dependent on actual $(CC) version o documented cc-ifversion o change so Kbuild.include is read before the kbuild file Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
This commit is contained in:
Sam Ravnborg
parent
b39927cf4c
commit
20a468b513
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@ -17,6 +17,7 @@ This document describes the Linux kernel Makefiles.
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--- 3.8 Command line dependency
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--- 3.9 Dependency tracking
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--- 3.10 Special Rules
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--- 3.11 $(CC) support functions
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=== 4 Host Program support
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--- 4.1 Simple Host Program
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@ -38,7 +39,6 @@ This document describes the Linux kernel Makefiles.
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--- 6.6 Commands useful for building a boot image
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--- 6.7 Custom kbuild commands
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--- 6.8 Preprocessing linker scripts
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--- 6.9 $(CC) support functions
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=== 7 Kbuild Variables
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=== 8 Makefile language
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@ -385,6 +385,102 @@ more details, with real examples.
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to prerequisites are referenced with $(src) (because they are not
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generated files).
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--- 3.11 $(CC) support functions
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The kernel may be build with several different versions of
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$(CC), each supporting a unique set of features and options.
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kbuild provide basic support to check for valid options for $(CC).
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$(CC) is useally the gcc compiler, but other alternatives are
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available.
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as-option
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as-option is used to check if $(CC) when used to compile
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assembler (*.S) files supports the given option. An optional
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second option may be specified if first option are not supported.
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Example:
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#arch/sh/Makefile
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cflags-y += $(call as-option,-Wa$(comma)-isa=$(isa-y),)
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In the above example cflags-y will be assinged the the option
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-Wa$(comma)-isa=$(isa-y) if it is supported by $(CC).
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The second argument is optional, and if supplied will be used
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if first argument is not supported.
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cc-option
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cc-option is used to check if $(CC) support a given option, and not
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supported to use an optional second option.
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Example:
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#arch/i386/Makefile
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cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586)
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In the above example cflags-y will be assigned the option
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-march=pentium-mmx if supported by $(CC), otherwise -march-i586.
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The second argument to cc-option is optional, and if omitted
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cflags-y will be assigned no value if first option is not supported.
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cc-option-yn
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cc-option-yn is used to check if gcc supports a given option
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and return 'y' if supported, otherwise 'n'.
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Example:
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#arch/ppc/Makefile
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biarch := $(call cc-option-yn, -m32)
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aflags-$(biarch) += -a32
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cflags-$(biarch) += -m32
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In the above example $(biarch) is set to y if $(CC) supports the -m32
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option. When $(biarch) equals to y the expanded variables $(aflags-y)
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and $(cflags-y) will be assigned the values -a32 and -m32.
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cc-option-align
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gcc version >= 3.0 shifted type of options used to speify
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alignment of functions, loops etc. $(cc-option-align) whrn used
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as prefix to the align options will select the right prefix:
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gcc < 3.00
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cc-option-align = -malign
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gcc >= 3.00
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cc-option-align = -falign
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Example:
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CFLAGS += $(cc-option-align)-functions=4
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In the above example the option -falign-functions=4 is used for
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gcc >= 3.00. For gcc < 3.00 -malign-functions=4 is used.
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cc-version
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cc-version return a numerical version of the $(CC) compiler version.
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The format is <major><minor> where both are two digits. So for example
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gcc 3.41 would return 0341.
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cc-version is useful when a specific $(CC) version is faulty in one
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area, for example the -mregparm=3 were broken in some gcc version
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even though the option was accepted by gcc.
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Example:
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#arch/i386/Makefile
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cflags-y += $(shell \
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if [ $(call cc-version) -ge 0300 ] ; then \
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echo "-mregparm=3"; fi ;)
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In the above example -mregparm=3 is only used for gcc version greater
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than or equal to gcc 3.0.
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cc-ifversion
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cc-ifversion test the version of $(CC) and equals last argument if
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version expression is true.
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Example:
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#fs/reiserfs/Makefile
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EXTRA_CFLAGS := $(call cc-ifversion, -lt, 0402, -O1)
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In this example EXTRA_CFLAGS will be assigned the value -O1 if the
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$(CC) version is less than 4.2.
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cc-ifversion takes all the shell operators:
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-eq, -ne, -lt, -le, -gt, and -ge
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The third parameter may be a text as in this example, but it may also
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be an expanded variable or a macro.
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=== 4 Host Program support
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@ -973,74 +1069,6 @@ When kbuild executes the following steps are followed (roughly):
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architecture specific files.
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--- 6.9 $(CC) support functions
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The kernel may be build with several different versions of
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$(CC), each supporting a unique set of features and options.
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kbuild provide basic support to check for valid options for $(CC).
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$(CC) is useally the gcc compiler, but other alternatives are
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available.
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cc-option
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cc-option is used to check if $(CC) support a given option, and not
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supported to use an optional second option.
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Example:
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#arch/i386/Makefile
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cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586)
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In the above example cflags-y will be assigned the option
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-march=pentium-mmx if supported by $(CC), otherwise -march-i586.
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The second argument to cc-option is optional, and if omitted
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cflags-y will be assigned no value if first option is not supported.
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cc-option-yn
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cc-option-yn is used to check if gcc supports a given option
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and return 'y' if supported, otherwise 'n'.
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Example:
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#arch/ppc/Makefile
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biarch := $(call cc-option-yn, -m32)
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aflags-$(biarch) += -a32
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cflags-$(biarch) += -m32
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In the above example $(biarch) is set to y if $(CC) supports the -m32
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option. When $(biarch) equals to y the expanded variables $(aflags-y)
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and $(cflags-y) will be assigned the values -a32 and -m32.
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cc-option-align
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gcc version >= 3.0 shifted type of options used to speify
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alignment of functions, loops etc. $(cc-option-align) whrn used
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as prefix to the align options will select the right prefix:
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gcc < 3.00
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cc-option-align = -malign
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gcc >= 3.00
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cc-option-align = -falign
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Example:
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CFLAGS += $(cc-option-align)-functions=4
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In the above example the option -falign-functions=4 is used for
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gcc >= 3.00. For gcc < 3.00 -malign-functions=4 is used.
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cc-version
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cc-version return a numerical version of the $(CC) compiler version.
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The format is <major><minor> where both are two digits. So for example
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gcc 3.41 would return 0341.
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cc-version is useful when a specific $(CC) version is faulty in one
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area, for example the -mregparm=3 were broken in some gcc version
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even though the option was accepted by gcc.
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Example:
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#arch/i386/Makefile
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cflags-y += $(shell \
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if [ $(call cc-version) -ge 0300 ] ; then \
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echo "-mregparm=3"; fi ;)
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In the above example -mregparm=3 is only used for gcc version greater
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than or equal to gcc 3.0.
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=== 7 Kbuild Variables
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The top Makefile exports the following variables:
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32
Makefile
32
Makefile
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@ -258,38 +258,6 @@ endif
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export quiet Q KBUILD_VERBOSE
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######
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# cc support functions to be used (only) in arch/$(ARCH)/Makefile
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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), $(CC)))
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# Look for make include files relative to root of kernel src
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MAKEFLAGS += --include-dir=$(srctree)
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@ -44,6 +44,43 @@ define filechk
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fi
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endef
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######
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# cc support functions to be used (only) in arch/$(ARCH)/Makefile
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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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@ -10,11 +10,12 @@ __build:
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# Read .config if it exist, otherwise ignore
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-include .config
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include scripts/Kbuild.include
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# The filename Kbuild has precedence over Makefile
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kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
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include $(if $(wildcard $(kbuild-dir)/Kbuild), $(kbuild-dir)/Kbuild, $(kbuild-dir)/Makefile)
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include scripts/Kbuild.include
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include scripts/Makefile.lib
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ifdef host-progs
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