Makefile将源文件从不同目录构建到同一对象目录中 [英] Makefile builds source files from different directories into the same object directory

问题描述

我有一个C项目，其目录布局是这样的

I have a c project with directory layout like this

src1
    -a.c
    -b.c
src2
    -c.c
    -d.c
objects

我正在尝试将a/b/c/d编译为目标文件并将其保存到objects目录中，这是我的Makefile的一部分.

I'm trying to compile a/b/c/d into objects files and saved them into objects directory and here is part of my Makefile.

src1 = src1/
src1 = src2/
obj = objects/
src1_files = a.c b.c
src2_files = c.c d.c
source_files = $(addprefix $(src1), $(src1_files)) $(addprefix $(src1), $(src2_files)) 
objects := $(addprefix $(obj), $(src1_files:.c=.o)) $(addprefix $(obj), $(src2_files:.c=.o))

$(obj)%.o: $(source_files)
    $(CC) $(CFLAGS) -c $< -o $@

all: $(objects)

但是，当我尝试运行make时，却得到了以下内容.

However when I try to run make, I got the following.

gcc -Wall -c src1/a.c -o objects/a.o
gcc -Wall -c src1/a.c -o objects/b.o
gcc -Wall -c src1/a.c -o objects/c.o
gcc -Wall -c src1/a.c -o objects/d.o

有人知道为什么要这么做吗?

Anyone knows why is it doing that?

推荐答案

在阅读答案费利克斯·帕尔曼(Felix Palmen)之后，尤其是最后一句话

After having read the answer of Felix Palmen, especially the last sentence

如果您真的希望直接在对象目录中找到对象，则需要两种模式规则，一种匹配src1中的源，另一种匹配src2中的源.

If you really want the objects directly in your objects directory, you need two pattern rules, one matching the sources in src1 and one matching the sources in src2.

出于好奇，我相应地修改了Makefile:

I modified the Makefile accordingly (out of curiosity):

src1 = src1/
src2 = src2/
obj = objects/
src1_files = a.c b.c
src2_files = c.c d.c
source_files = $(addprefix $(src1), $(src1_files)) $(addprefix $(src2), $(src2_files)) 
objects := $(addprefix $(obj), $(src1_files:.c=.o)) $(addprefix $(obj), $(src2_files:.c=.o))

$(obj)%.o: src1/%.c
    $(CC) $(CFLAGS) -c $< -o $@

$(obj)%.o: src2/%.c
    $(CC) $(CFLAGS) -c $< -o $@

all: $(objects)

我在cygwin的bash中进行了测试:

I tested in bash on cygwin:

$ mkdir src1 src2 objects

$ touch src1/a.c src1/b.c src2/c.c src2/d.c

$ make
cc  -c src1/a.c -o objects/a.o
cc  -c src1/b.c -o objects/b.o
cc  -c src2/c.c -o objects/c.o
cc  -c src2/d.c -o objects/d.o

$ 

...而且有效.

(我省略了有关构建objects目录的详细信息，只是手动创建的.)

(I left out the detail about building the objects directory – just created it manually).

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