u-boot中的include/autoconf.mk文件是如何生成的

在Makefile中：

$(obj)include/autoconf.mk: $(obj)include/config.h
  @$(XECHO) Generating $@ ; /
  set -e ; /
  : Extract the config macros ; /
  $(CPP) $(CFLAGS) -DDO_DEPS_ONLY -dM include/common.h | /
    sed -n -f tools/scripts/define2mk.sed > $@

实际执行的命令：

arm-none-linux-gnueabi-gcc -E -g -Os -fno-strict-aliasing -fno-common -ffixed-r8 -msoft-float -D__KERNEL__ -DTEXT_BASE=0xc3e00000 -I/home/zkl/svn/compiled/uboot-1.3.4-m9_v4/include -fno-builtin -ffreestanding -nostdinc -isystem /usr/local/arm/arm-2009q3/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1/include -pipe -DCONFIG_ARM -D__ARM__ -march=armv5te -mabi=apcs-gnu -mno-thumb-interwork -Wall -Wstrict-prototypes -fno-stack-protector -DDO_DEPS_ONLY -dM include/common.h | sed -n -f tools/scripts/define2mk.sed

/^#define CONFIG_[A-Za-z0-9_][A-Za-z0-9_]*/ {
  # Strip the #define prefix
  s/#define *//;              
  # Change to form CONFIG_*=VALUE
  s/  */=/;
  # Drop trailing spaces      
  s/ *$//;
  # drop quotes around string values
  s/="/(.*/)"$/=/1/;          
  # Concatenate string values 
  s/" *"//g;
  # Wrap non-numeral values with quotes
  s/=/(.*/?[^0-9].*/)$/=/"/1/"/; 
  # Change '1' and empty values to "y" (not perfect, but
  # supports conditional compilation in the makefiles
  s/=$/=y/;
  s/=1$/=y/;
  # print the line            
  p                           
}