如何使用Makefile变量作为要包含在g ++命令中的文件? [英] How to use Makefile variables as files to include in g++ command?

问题描述

这是我的问题:我有一个makefile文件，其中包含用于编译项目中所有内容的信息，以使我的生活更轻松，但是最近这让我有些头疼.

Here's my problem : I have a makefile file containing the info to compile everything in my project to make my life easier, but it is giving me some headaches recently.

它可以编译多个文件，例如:

It can compile multiple files, such as this :

objects/io.o: sources/io.cpp
    @g++ -c $< -o $@ -std=c++11
objects/map.o: sources/map.cpp
    @g++ -c $< -o $@ -std=c++11

在makefile的顶部，我有这样声明的变量:

At the top of the makefile, I have variables declared as such :

IO="objects/io.o"
MAP="objects/map.o"
[... other object files ...]
ALL="$(IO) $(MAP) [...]"

当我要编译主文件时，我使用以下命令:

When I want to compile my main file, I use this command :

main.exe: tests/main.cpp
    @g++ $< $(ALL) -o $@ -std=c++11

当我手动编译此问题时(在命令的一行中输入所有内容，而不是使用make main.exe进行编译)，则编译时不会出现问题.

When I compile this problem manually (inputting everything in one line of command, instead of making make main.exe) it compiles without problems.

但是，当我在项目中使用make命令时，会弹出以下错误:

However, when I use the make command for the project, the following error pops up :

clang: error: no such file or directory: 'objects/io.o objects/map.o [...]'
make: *** [main.exe] Error 1

我不能以这种方式使用变量吗?我非常困惑.我知道这些文件都是经过编译的，似乎make实用工具无法理解文件路径.

Can I not use variables this way ? I'm extremely confused. I know for a fact those files are compiled, it just seems the make utility doesn't understand file paths.

推荐答案

我认为问题在于您引用了变量.尝试取消引号，它们将不会扩展单个参数:

I think the problem is that you have quoted your variables. Try unquoting them and they won't expand a single parameter:

ALL = $(obj1) $(obj2) ...

此外，对于那些使用相同编译过程的对象，我通常会定义一条规则:

Also, for those objects which use the same compilation process I generally define a single rule:

obj/%.o: %.cc
    $(GCC) -o $@ -c $< $(FLAGS)

显然，这需要定义额外的变量GCC和FLAGS

Obviously that would require defining the extra variables GCC and FLAGS

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