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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 <[email protected]>
This commit is contained in:
Sam Ravnborg
parent
b39927cf4c
commit
20a468b513
4 changed files with 136 additions and 102 deletions
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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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