--- 3.8 Command line dependency
--- 3.9 Dependency tracking
--- 3.10 Special Rules
+ --- 3.11 $(CC) support functions
=== 4 Host Program support
--- 4.1 Simple Host Program
--- 6.6 Commands useful for building a boot image
--- 6.7 Custom kbuild commands
--- 6.8 Preprocessing linker scripts
- --- 6.9 $(CC) support functions
=== 7 Kbuild Variables
=== 8 Makefile language
to prerequisites are referenced with $(src) (because they are not
generated files).
+--- 3.11 $(CC) support functions
+
+ The kernel may be build with several different versions of
+ $(CC), each supporting a unique set of features and options.
+ kbuild provide basic support to check for valid options for $(CC).
+ $(CC) is useally the gcc compiler, but other alternatives are
+ available.
+
+ as-option
+ as-option is used to check if $(CC) when used to compile
+ assembler (*.S) files supports the given option. An optional
+ second option may be specified if first option are not supported.
+
+ Example:
+ #arch/sh/Makefile
+ cflags-y += $(call as-option,-Wa$(comma)-isa=$(isa-y),)
+
+ In the above example cflags-y will be assinged the the option
+ -Wa$(comma)-isa=$(isa-y) if it is supported by $(CC).
+ The second argument is optional, and if supplied will be used
+ if first argument is not supported.
+
+ cc-option
+ cc-option is used to check if $(CC) support a given option, and not
+ supported to use an optional second option.
+
+ Example:
+ #arch/i386/Makefile
+ cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586)
+
+ In the above example cflags-y will be assigned the option
+ -march=pentium-mmx if supported by $(CC), otherwise -march-i586.
+ The second argument to cc-option is optional, and if omitted
+ cflags-y will be assigned no value if first option is not supported.
+
+ cc-option-yn
+ cc-option-yn is used to check if gcc supports a given option
+ and return 'y' if supported, otherwise 'n'.
+
+ Example:
+ #arch/ppc/Makefile
+ biarch := $(call cc-option-yn, -m32)
+ aflags-$(biarch) += -a32
+ cflags-$(biarch) += -m32
+
+ In the above example $(biarch) is set to y if $(CC) supports the -m32
+ option. When $(biarch) equals to y the expanded variables $(aflags-y)
+ and $(cflags-y) will be assigned the values -a32 and -m32.
+
+ cc-option-align
+ gcc version >= 3.0 shifted type of options used to speify
+ alignment of functions, loops etc. $(cc-option-align) whrn used
+ as prefix to the align options will select the right prefix:
+ gcc < 3.00
+ cc-option-align = -malign
+ gcc >= 3.00
+ cc-option-align = -falign
+
+ Example:
+ CFLAGS += $(cc-option-align)-functions=4
+
+ In the above example the option -falign-functions=4 is used for
+ gcc >= 3.00. For gcc < 3.00 -malign-functions=4 is used.
+
+ cc-version
+ cc-version return a numerical version of the $(CC) compiler version.
+ The format is <major><minor> where both are two digits. So for example
+ gcc 3.41 would return 0341.
+ cc-version is useful when a specific $(CC) version is faulty in one
+ area, for example the -mregparm=3 were broken in some gcc version
+ even though the option was accepted by gcc.
+
+ Example:
+ #arch/i386/Makefile
+ cflags-y += $(shell \
+ if [ $(call cc-version) -ge 0300 ] ; then \
+ echo "-mregparm=3"; fi ;)
+
+ In the above example -mregparm=3 is only used for gcc version greater
+ than or equal to gcc 3.0.
+
+ cc-ifversion
+ cc-ifversion test the version of $(CC) and equals last argument if
+ version expression is true.
+
+ Example:
+ #fs/reiserfs/Makefile
+ EXTRA_CFLAGS := $(call cc-ifversion, -lt, 0402, -O1)
+
+ In this example EXTRA_CFLAGS will be assigned the value -O1 if the
+ $(CC) version is less than 4.2.
+ cc-ifversion takes all the shell operators:
+ -eq, -ne, -lt, -le, -gt, and -ge
+ The third parameter may be a text as in this example, but it may also
+ be an expanded variable or a macro.
+
=== 4 Host Program support
architecture specific files.
---- 6.9 $(CC) support functions
-
- The kernel may be build with several different versions of
- $(CC), each supporting a unique set of features and options.
- kbuild provide basic support to check for valid options for $(CC).
- $(CC) is useally the gcc compiler, but other alternatives are
- available.
-
- cc-option
- cc-option is used to check if $(CC) support a given option, and not
- supported to use an optional second option.
-
- Example:
- #arch/i386/Makefile
- cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586)
-
- In the above example cflags-y will be assigned the option
- -march=pentium-mmx if supported by $(CC), otherwise -march-i586.
- The second argument to cc-option is optional, and if omitted
- cflags-y will be assigned no value if first option is not supported.
-
- cc-option-yn
- cc-option-yn is used to check if gcc supports a given option
- and return 'y' if supported, otherwise 'n'.
-
- Example:
- #arch/ppc/Makefile
- biarch := $(call cc-option-yn, -m32)
- aflags-$(biarch) += -a32
- cflags-$(biarch) += -m32
-
- In the above example $(biarch) is set to y if $(CC) supports the -m32
- option. When $(biarch) equals to y the expanded variables $(aflags-y)
- and $(cflags-y) will be assigned the values -a32 and -m32.
-
- cc-option-align
- gcc version >= 3.0 shifted type of options used to speify
- alignment of functions, loops etc. $(cc-option-align) whrn used
- as prefix to the align options will select the right prefix:
- gcc < 3.00
- cc-option-align = -malign
- gcc >= 3.00
- cc-option-align = -falign
-
- Example:
- CFLAGS += $(cc-option-align)-functions=4
-
- In the above example the option -falign-functions=4 is used for
- gcc >= 3.00. For gcc < 3.00 -malign-functions=4 is used.
-
- cc-version
- cc-version return a numerical version of the $(CC) compiler version.
- The format is <major><minor> where both are two digits. So for example
- gcc 3.41 would return 0341.
- cc-version is useful when a specific $(CC) version is faulty in one
- area, for example the -mregparm=3 were broken in some gcc version
- even though the option was accepted by gcc.
-
- Example:
- #arch/i386/Makefile
- cflags-y += $(shell \
- if [ $(call cc-version) -ge 0300 ] ; then \
- echo "-mregparm=3"; fi ;)
-
- In the above example -mregparm=3 is only used for gcc version greater
- than or equal to gcc 3.0.
-
-
=== 7 Kbuild Variables
The top Makefile exports the following variables:
projects / powerpc.git / blobdiff