oMT7620N httpd_new的Makefile学习
/opt/ralink-toolchains/buildroot-gcc342/bin/mipsel-linux-uclibc-gcc -o httpd main.o httpd.o basic.o ej.o cgi_main.o cgi_object.o cgi_util. o cgi_cmd.o cgi_dump.o cgi_upload.o -Wl,-rpath, -L/home/wudi/origin/trunk/targets/MT7620N/fs.install/lib -L/home/wudi/origin/trunk/targets /MT7620N/fs.install/lib/private -L/home/wudi/origin/trunk/targets/MT7620N/fs.install/lib/public -lcms_dal -lcms_msg -lcms_util -lcms_boardctl -lcrypt -lutil -ldl -lcms_core -lnanoxml -ldl -lmdm -lc
EXE = httpd
$(EXE): $(OBJS)
$(CC) -o $@ $^ -Wl, -rpath, $(CMS_LIB_RPATH), $(CMS_LIB_PATH), $(LIBS)
#Include the rule for making dependcy files.
#The "-" in front of the second include suppresses
#error messages when make cannot find the .d files.
#It will just regenerate them.
#See Section 4.14 of Gnu make.
include $(BUILD_DIR)/make.deprules
-incude $(OBJS:.o=.d)
.o文件的生成是在-include $(OBJS:.o=.d)这一步生成的，按上述的英文描述， 在没有.d存在的时候，
仅仅是生成.d文件而没有报错。
.d的规则是在make.deprules中定义的。
1. make.common中
(1)
ifndef TOOLCHAIN_TOP
TOOLCHAIN_TOP = /opt/toolchains/uclibc-crosstools-gcc-4.4.2.1
endif
CFLAGS = $(CMS_COMPILE_FLAGS) $(CUSTOM_CFLAGS) $(ALLOWED_INCLUDE_PATHS) $(CMS_WLAN_FLAGS)
CFLAGS += -I$(TOOLCHAIN)/include -L$(TOOLCHAIN)/lib
CFLAGS += $(BRCM_WERROR_CFLAGS)
CFLAGS += DP$(PROFILE)
(2)
MT7620N profile中
TOOLCHAIN_TOP_DIR="/opt/ralink-toolchains/buildroot-gcc342"
UCLIBC=y
(3)
make.common中
ifeq ($(strip $(MT7620N)), y)
TOOLCHAIN_TOP = $(TOOLCHAIN_TOP_DIR: "%"=%)
TOOLCHAIN = $(TOOLCHAIN_TOP)
LIBDIR = $(TOOLCHAIN_TOP)/lib
USRLIBDIR = $(TOOLCHAIN_TOP)/usr/lib
EXTRALIBDIR = $(TOOLCHAIN_TOP)/LIB
EXTRAINCDIR = $(TOOLCHAIN)/usr/lib/gcc/mips-linux-uclibc/4.4.2/include
LIB_PATH = $(TOOLCHAIN_TOP)/lib
LIBCDIR = $(TOOLCHAIN_TOP)/lib
export BRCM_WERROR_CFLAGS :=
BRCM_COMMON_FLAGS :=
export BRCM_APP_CFLAGS := $(BRCM_COMMON_FLAGS)
export BRCM_SO_CFLAGS := $(BRCM_COMMON_FLAGS)
CROSS_COMPILE = $(TOOLCHAIN)/bin/mipsel-linux-uclibc-
ACTURAL_KERNEL_DIR = mt7620/linux-2.6.36.x
endif
AR = $(CROSS_COMPILE)ar
AS = $(CROSS_COMPILE)as
LD = $(CROSS_COMPILE)ld
CC = $(CROSS_COMPILE)gcc
CXX = $(CROSS_COMPILE)g++
CPP = $(CROSS_COMPILE)cpp
NM = $(CROSS_COMPILE)nm
STRIP = $(CROSS_COMPILE)strip
SSTRIP = $(CROSS_COMPILE)sstrip
OBJCOPY = $(CROSS_COMPILE)objcopy
OBJDUMP = $(CROSS_COMPILE)objdump
RANLIB = $(CROSS_COMPILE)ranlib
export TOOLCHAIN_TIP TOOLCHAIN LEGACY_TOOLCHAIN CROSS_COMPILE \
AR AS LD CC CXX CPP NM STRIP SSTRIP OBJCOPY OBJDUMP RANLIB \
LIB_PATH LIBDIR USRLIBDIR EXTRALIBDIR EXTRAINCDIR LIBCDIR BUILD_GDBSERVER
2. httpd_new的Makefile中
all dynamic install: $(EXE) generic_exe_install cpall_html
EXE = httpd
$(EXE): $(OBJS)
$(CC) -o $@ $^ -Wl, -rpath, $(CMS_LIB_RPATH), $(CMS_LIB_PATH), $(LIBS)
（1） CC在make.common中定义了， 是toolchain下的gcc
(2) $@-目标文件，$^所有依赖的文件， $<第一个依赖的文件。
(3) -Wl(man ld), -W warning options,
-Wl, option, Linker Option
Linker Options
object-file-name -l(library), -nostartfiles -nodefaultlibs, -nostdlib, -pie, -rdynamic, -s, -static, -static-libgcc, -static-libstdc++,
-shared, -shared-libgcc, -symboic, -T (script), -Wl, option, -Xlinker (option), -u (symbol)
Note: if the linker is being invoked indirectly, via a compiler driver (e.g. gcc), then all the linker command line options
shouled be prefiixed by -Wl, (or whatever is appropriate for the particular compiler) like this:
gcc -Wl, --start-group foo.o bar.o -Wl, --end-group
当链接器被间接调用（如通过编译器gcc）时， 所有连接器的命令选项都需要加上-Wl前缀。 -W warning option, -l linker option.
This is important, because otherwise the compiler program may silently drop the linker options, resulting in a bad link.
Comfusion may also arise when passing options that require values through a driver, as the use of a space between
option and argument acts as seprator, and causes the driver to pass only the option to the linker and the argument
to the compiler. In this case, it is simplest to use the joined forms of both single- and multiple-letter options, such as
gcc foo.o bar.o -Wl, -e(Entry) -Wl, -Map=a.map
-Map=mapfile
Print a link map to the file mapfile. See the description of the -M option, above.
-M
--print-map
Print a link map to the standard output. A link map provides information about the link, including the following:
..Where object files are mapped into memory.
..How common symbols are allocated.
.. All archive members included in the link, with a mention of the symbol which caused the archive member to
brought in.
.. The values assigned to symbols.
-rpath(man ld): Add a directory to the runtime library search path. This is used when linking an ELF executable with shared objects.
All -rapth arguments are concatinated and passed to the runtime linker, which uses them to locate shared
-L (man ld): -L searchdir
Add path searchdir to the list of paths that ld will search for archive libraries and ld control scripts.
Directories specified on the command line are searched before the default directories.
All -L options apply to all -l options, regardless of the order in which the options appear.
-l (man ld): -l namespec
Add the archive or object file spcified by namespec to the list of files to link.
If namespec is of the form :filename, ld will search the library path for a file called filename, otherwise
it will search the library path for a file called libnamespec.a .
On systems which support shared libraries, ld may also search for files other than libnamespec.a .
Specifically, on ELF and SunOS systems ld will search a directory for a library called libnamespec.so before
searching for one called libnamespec.a (By convention, a ".so" extension indicates a shared library). Note
that this behavior does not apply to :filename, which always specifies a file called filename.
make.common中
CMS_LIB_RPATH=
CMS_LIB_PATH = $(patsubst %, -L$(INSTALL_DIR)%, $(subst :, ,$(ALLOWED_LIB_DIRS))
INSTALL_DIR=$(PROFILE_DIR)/fs.install
CMS_COMMON_LIBS := -lcms_util -lcms_broadctl -lcrypt -lutil
CMS_CORE_LIBS := -lcms_core -lnanoxml -ldl -lmdm
httpd_new的Makefile中
LIBS = -lcms_dal -cms_msg $(CMS_COMMON_LIBS) -ldl $(CMS_CORE_LIBS)
AllOWED_LIB_DIRS := /lib:/lib/private:/lib/public
LIBS += -lc
httpd_new的Makefile中：
include $(BUILD_DIR)/make.deprules
-include $(OBJS:.o=.d)
make.deprules中
ifneq ($(MAKECMDGOALS), clean)
%.d: %.c
@set -e; rm -f $@; \
$(CC) -M $(CPPFLAGS) $(CFLAGS) $< > $@.SSSS 2>/dev/null; \
sed '' < $@.SSSS > $@; \
rm -f $@.SSSS
endif
