Makefile 语法分析 第一部分 VERSION = 2 # 给变量VERSION 赋值 PATCHLEVEL = 6 # 给变量PATCHLEVEL 赋值 SUBLEVEL = 22 # 给变量SUBLEVEL 赋值 EXTRAVERSION = .6 # 给变量EXTRAVERSION 赋值 NAME = Holy Dancing Manatees, Batman! # 给变量NAME 赋值 # *DOCUMENTATION* # To see a list of typical targets execute "make help" # More info can be located in ./README # Comments in this file are targeted only to the developer, do not # expect to learn how to build the kernel reading this file. # Do not: # o use make's built-in rules and variables # (this increases performance and avoid hard-to-debug behavour); # o print "Entering directory ..."; MAKEFLAGS += -rR --no-print-directory # 操作符“+=”的作用是给变量（“+=”前面的MAKEFLAGS）追加值。 # 如果变量（“+=”前面的MAKEFLAGS）之前没有定义过，那么，“+=”会自动变成“=”； # 如果前面有变量（“+=”前面的MAKEFLAGS）定义，那么“+=”会继承于前次操作的赋值符； # 如果前一次的是“:=”，那么“+=”会以“:=”作为其赋值符 # 在执行 make 时的命令行选项参数被通过变量 “MAKEFLAGS”传递给子目录下的make 程序。 # 对于这个变量除非使用指示符“unexport”对它们进行声明，它们在整个 make 的执行过程中始终被自动的传递给所有的子 make。 # 还有个特殊变量SHELL 与 MAKEFLAGS 一样，默认情况（没有用“unexport”声明）下在整个make 的执行过程中被自动的传递给所有的子 make。 # # -rR --no-print-directory # -r disable the built-in impilict rules. # -R disable the built-in variable setttings. # --no-print-directory。 # We are using a recursive build, so we need to do a little thinking # to get the ordering right. # # Most importantly: sub-Makefiles should only ever modify files in # their own directory. If in some directory we have a dependency on # a file in another dir (which doesn't happen often, but it's often # unavoidable when linking the built-in.o targe...
