关键Makefile 解读

# include the system specific Makefile

＃0 shell uname 为变量

＃1 寻找 ../../目录下的 的相应文件，并释放到当前位置
include ../../Makefile.$(shell uname)

＃依赖关系，default依赖于 all

default: all

all: cmm_setup.o cmm.o
all: cmm_setup.lo cmm.lo

clean:
 -rm -f *.o *.lo Makefile.depend matplc.log

#get warnings, debugging information and optimization

#CFLAGS 给编译器使有的变量，用以设置相关参数
CFLAGS  = -Wall -Wpointer-arith -Wstrict-prototypes -Wwrite-strings
# CFLAGS += -Werror
CFLAGS += -ggdb -O3 -funroll-loops
# Note: if the optimizer crashes, we'll leave out the -O3 for those files

CFLAGS += -I..
CFLAGS += $(PLCSYSTEM_CFLAGS)

#how to make things from other directories if they are missing

＃$（◎D）$@的目录部分，$(@F) $@的文件部分

＃。。、%/% 依赖于 先到相关目录下 再执行MAKE命令

# %表示，无字符或任意字符
../% /%: $(MAKE) -C $(@D) $(@F)

＃多目标依赖

＃MM gun make头文件依赖

# - I include dir

Makefile.depend depend:
 $(CC) -MM -MG -I.. $(PLCSYSTEM_CFLAGS) *.c /
   | perl -pe 's/:/ Makefile.depend:/' > Makefile.depend

include Makefile.depend

# make a shareable object from C source

#$< 依赖目标的第一个文件，如果依赖目标是％则是依赖目标的所有文件

#使用LIBTOOL 工具进行编译
%.lo: %.c
 $(LIBTOOL) --mode=compile $(COMPILE.c) $(OUTPUT_OPTION) $<