What a Rule Looks Like
target … : prerequisites …
recipe
A target is usually the name of a file that is generated by a program; examples of targets are executable or object files. A target can also be the name of an action to carry out, such as ‘clean’ (see Phony Targets).
A prerequisite is a file that is used as input to create the target. A target often depends on several files.
A recipe is an action that make carries out.
target:目标文件
prerequites:前提条件，意思就是如果要执行目标文件下的recipe，prerequites的存在是必须条件。
recipe：即是shell的命令
make carries out.target:目标文件
prerequites:前提条件，意思就是如果要执行目标文件下的recipe，prerequites的存在是必须条件。
recipe：即是shell的命令
Automatic Variables
These variables have values computed afresh for each rule that is executed, based on the target and prerequisites of the rule.In this example, you would use ‘$@’ for the object file name and ‘$<’ for the source file name.It’s very important that you recognize the limited scope in which automatic variable values are available: they only have values within the recipe. In particular, you cannot use them anywhere within the target list of a rule; they have no value there and will expand to the empty string. Also, they cannot be accessed directly within the prerequisite list of a rule.
ps:When it is time to execute recipes to update a target, they are executed by invoking a new sub-shell for each line of the recipe, unless the
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接下来我修改了Makefile，使得它能通过编译main.c成二进制文件到tests/main，通过./main输出结果：
1 CC=gcc
2 CFLAGS =-std=c99 -pedantic -Wextra -Wall -Werror
3 LDFLAGS=-shared -fPIC
4 TARGET=libmalloc.so
5 CHECK=check
6
7 SRC= ./src/metadata.c ./src/malloc.c \
8 ./src/calloc.c
9 OBJ=$(SRC=.c:.o)
告诉makefile把.c文件转为.o
10 RM = rm -fr
11
12
13 #target $@, object $^, first dependency file $<
14 $(TARGET):$(OBJ)
15 $(CC) $(LDFLAGS) -o $@ $(SRC)
编译libmalloc.so，首先所有的.o文件要存在
16
17 main:
18 #$(MAKE) -C test （意思：如果有子makefile在test文件夹里，命令一起执行）
19 $(CC) $(CFLAGS) -o tests/main src/main.c
单独编译main函数
20
21 check:all
22 all:$(TARGET) $(OBJ) main
23 LD_PRELOAD=./libmalloc.so ./tests/main
LD_PRELOAD是把自己的库替换系统提供的库，使得文件用的是我自己同名的malloc
24 .PHONY: clean
25 clean:
26 $(RM) $(OBJ) $(TARGET) \
27 $(RM) a.out tests/main
http://blog.csdn.net/liang13664759/article/details/1771246
Makefile 全面讲解
http://ccckmit.wikidot.com/code:c0p
build parse tree实例
GNU make: Secondary Expansion
make rules 和 implicit rule search
.ONESHELL special target is in effect (see Using One Shell) (In practice, make may take shortcuts that do not affect the results.)//-------------------------------------------------------------------------------------------------------------------------------
接下来我修改了Makefile，使得它能通过编译main.c成二进制文件到tests/main，通过./main输出结果：
1 CC=gcc
2 CFLAGS =-std=c99 -pedantic -Wextra -Wall -Werror
3 LDFLAGS=-shared -fPIC
4 TARGET=libmalloc.so
5 CHECK=check
6
7 SRC= ./src/metadata.c ./src/malloc.c \
8 ./src/calloc.c
9 OBJ=$(SRC=.c:.o)
告诉makefile把.c文件转为.o
10 RM = rm -fr
11
12
13 #target $@, object $^, first dependency file $<
14 $(TARGET):$(OBJ)
15 $(CC) $(LDFLAGS) -o $@ $(SRC)
编译libmalloc.so，首先所有的.o文件要存在
16
17 main:
18 #$(MAKE) -C test （意思：如果有子makefile在test文件夹里，命令一起执行）
19 $(CC) $(CFLAGS) -o tests/main src/main.c
单独编译main函数
20
21 check:all
22 all:$(TARGET) $(OBJ) main
23 LD_PRELOAD=./libmalloc.so ./tests/main
LD_PRELOAD是把自己的库替换系统提供的库，使得文件用的是我自己同名的malloc
24 .PHONY: clean
25 clean:
26 $(RM) $(OBJ) $(TARGET) \
27 $(RM) a.out tests/main
http://blog.csdn.net/liang13664759/article/details/1771246
Makefile 全面讲解
http://ccckmit.wikidot.com/code:c0p
build parse tree实例
GNU make: Secondary Expansion
make rules 和 implicit rule search
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