--- 3.7 Compilation flags
- EXTRA_CFLAGS, EXTRA_AFLAGS, EXTRA_LDFLAGS, EXTRA_ARFLAGS
+ EXTRA_CFLAGS, EXTRA_AFLAGS, EXTRA_LDFLAGS
All the EXTRA_ variables apply only to the kbuild makefile
where they are assigned. The EXTRA_ variables apply to all
This variable is necessary because the top Makefile owns the
- variable $(CFLAGS) and uses it for compilation flags for the
+ variable $(KBUILD_CFLAGS) and uses it for compilation flags for the
entire tree.
$(EXTRA_AFLAGS) is a similar string for per-directory options
EXTRA_AFLAGS := -traditional
- $(EXTRA_LDFLAGS) and $(EXTRA_ARFLAGS) are similar strings for
- per-directory options to $(LD) and $(AR).
+ $(EXTRA_LDFLAGS) is a string for per-directory options to $(LD).
Example:
#arch/m68k/fpsp040/Makefile
-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.
+ Note: cc-option uses KBUILD_CFLAGS for $(CC) options
cc-option-yn
cc-option-yn is used to check if gcc supports a given option
option. When $(biarch) equals 'y', the expanded variables $(aflags-y)
and $(cflags-y) will be assigned the values -a32 and -m32,
respectively.
+ Note: cc-option-yn uses KBUILD_CFLAGS for $(CC) options
cc-option-align
gcc versions >= 3.0 changed the type of options used to specify
cc-option-align = -falign
Example:
- CFLAGS += $(cc-option-align)-functions=4
+ KBUILD_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.
+ Note: cc-option-align uses KBUILD_CFLAGS for $(CC) options
cc-version
cc-version returns a numerical version of the $(CC) compiler version.
Example:
#arch/s390/Makefile
LDFLAGS := -m elf_s390
- Note: EXTRA_LDFLAGS and LDFLAGS_$@ can be used to further customise
- the flags used. See chapter 7.
+ Note: EXTRA_LDFLAGS can be used to further customise
+ the flags used. See chapter 3.7.
LDFLAGS_MODULE Options for $(LD) when linking modules
#arch/sparc64/Makefile
AFLAGS += -m64 -mcpu=ultrasparc
- CFLAGS $(CC) compiler flags
+ KBUILD_CFLAGS $(CC) compiler flags
Default value - see top level Makefile
Append or modify as required per architecture.
- Often, the CFLAGS variable depends on the configuration.
+ Often, the KBUILD_CFLAGS variable depends on the configuration.
Example:
#arch/i386/Makefile
cflags-$(CONFIG_M386) += -march=i386
- CFLAGS += $(cflags-y)
+ KBUILD_CFLAGS += $(cflags-y)
Many arch Makefiles dynamically run the target C compiler to
probe supported options:
-march=pentium2,-march=i686)
...
# Disable unit-at-a-time mode ...
- CFLAGS += $(call cc-option,-fno-unit-at-a-time)
+ KBUILD_CFLAGS += $(call cc-option,-fno-unit-at-a-time)
...