s3c6410_U-boot Makefile分析(一)

U-boot Makefile分析(一)

VERSION = 2011 PATCHLEVEL = 09 SUBLEVEL = EXTRAVERSION = ifneq "$(SUBLEVEL)" "" U_BOOT_VERSION = $(VERSION).$(PATCHLEVEL).$(SUBLEVEL)$(EXTRAVERSION) else U_BOOT_VERSION = $(VERSION).$(PATCHLEVEL)$(EXTRAVERSION) endif TIMESTAMP_FILE = $(obj)include/timestamp_autogenerated.h VERSION_FILE = $(obj)include/version_autogenerated.h	定义U-boot版本号变量U_BOOT_VERSION、时间戳头文件TIMESTAMP_FILE及版本信息头文件VERSION_FILE
HOSTARCH := $(shell uname -m | \          sed -e s/i.86/x86/ \              -e s/sun4u/sparc64/ \              -e s/arm.*/arm/ \              -e s/sa110/arm/ \              -e s/ppc64/powerpc/ \              -e s/ppc/powerpc/ \              -e s/macppc/powerpc/\              -e s/sh.*/sh/)   HOSTOS := $(shell uname -s | tr '[:upper:]' '[:lower:]' | \              sed -e 's/\(cygwin\).*/cygwin/')	定义利用shell函数初始化主机（Host）架构变量HOSTARCH、主机操作系统变量HOSTOS，可能的话使用sed编辑器替换成标准名字
# Set shell to bash if possible, otherwise fall back to sh SHELL := $(shell if [ -x "$$BASH" ]; then echo $$BASH; \          else if [ -x /bin/bash ]; then echo /bin/bash; \          else echo sh; fi; fi)
export        HOSTARCH HOSTOS SHELL	转化自定义变量 HOSTARCH HOSTOS SHELL成系统环境变量
# Deal with colliding definitions from tcsh etc. VENDOR=	？
######################################################################### # Allow for silent builds ifeq (,$(findstring s,$(MAKEFLAGS))) XECHO = echo else XECHO = : endif   #########################################################################	当make使用–s参数时，不打印一些过程信息
ifdef O ifeq ("$(origin O)", "command line") BUILD_DIR := $(O) endif endif   ifneq ($(BUILD_DIR),) saved-output := $(BUILD_DIR)   # Attempt to create a output directory. $(shell [ -d ${BUILD_DIR} ] || mkdir -p ${BUILD_DIR})   # Verify if it was successful. BUILD_DIR := $(shell cd $(BUILD_DIR) && /bin/pwd) $(if $(BUILD_DIR),,$(error output directory "$(saved-output)" does not exist)) endif # ifneq ($(BUILD_DIR),)   OBJTREE             := $(if $(BUILD_DIR),$(BUILD_DIR),$(CURDIR)) SPLTREE              := $(OBJTREE)/spl SRCTREE             := $(CURDIR) TOPDIR                := $(SRCTREE) LNDIR                  := $(OBJTREE) export        TOPDIR SRCTREE OBJTREE SPLTREE   MKCONFIG          := $(SRCTREE)/mkconfig export MKCONFIG   ifneq ($(OBJTREE),$(SRCTREE)) REMOTE_BUILD  := 1 export REMOTE_BUILD endif	Makefile支持编译的*.o文件存储在源文件之外的其它路径下，当make 命令行中有定义路径变量O，makefile脚本从命令行中提取出*.o文件路径BUILD_DIR。
OBJTREE             := $(if $(BUILD_DIR),$(BUILD_DIR),$(CURDIR)) SPLTREE              := $(OBJTREE)/spl SRCTREE             := $(CURDIR) TOPDIR                := $(SRCTREE) LNDIR                  := $(OBJTREE) export        TOPDIR SRCTREE OBJTREE SPLTREE	初始化一些路径变量