u-boot Makefile分析 -- (2)

来源：互联网发布：mac如何设置用户名编辑：程序博客网时间：2024/05/01 13:32

[Author: Bo Shen <voice.shen@gmail.com>]

[u-boot: 2014.01-rc1, e03c76c30342797a25ef9350e51c8daa0b56f1df]

1. 一些参数的export

101 OBJTREE         := $(if $(BUILD_DIR),$(BUILD_DIR),$(CURDIR))102 SPLTREE         := $(OBJTREE)/spl103 TPLTREE         := $(OBJTREE)/tpl104 SRCTREE         := $(CURDIR)105 TOPDIR          := $(SRCTREE)106 LNDIR           := $(OBJTREE)107 export  TOPDIR SRCTREE OBJTREE SPLTREE TPLTREE108 109 MKCONFIG        := $(SRCTREE)/mkconfig110 export MKCONFIG111 112 ifneq ($(OBJTREE),$(SRCTREE))113 REMOTE_BUILD    := 1114 export REMOTE_BUILD115 endif116 117 # $(obj) and (src) are defined in config.mk but here in main Makefile118 # we also need them before config.mk is included which is the case for119 # some targets like unconfig, clean, clobber, distclean, etc.120 ifneq ($(OBJTREE),$(SRCTREE))121 obj := $(OBJTREE)/122 src := $(SRCTREE)/123 else124 obj :=125 src :=126 endif127 export obj src128 129 # Make sure CDPATH settings don't interfere130 unexport CDPATH

101: Makefile中if的使用：$(if <condition>, <then-part>, <else-part>). 相当于C语言中的if-then-else. 其中BUILD_DIR在前面判断过，CURDIR是Makefile中的一个特殊参数，表示当前目录。所以，此句含义是决定使用BUILD_DIR还是CURDIR.

102~107: 做一些赋值，然后export这些变量。

109: 得到mkconfig，并且export。

112~115: 判断是否是本地编译，导致的结果是编译生成的object文件是否与源代码在同一目录。

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