C++ 在C++中包含不同目录中的头文件
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Include header file in different directory in c++
提问by J. Lin
I've been learning c++ and encountered the following question: I have a directory structure like:
我一直在学习 c++ 并遇到以下问题：我有一个目录结构，如：
- current directory
- Makefile
- include
- header.h
- src
- main.cpp
my header.h :
我的 header.h ：
#include <iostream>
using namespace std;
void print_hello();
my main.cpp:
我的 main.cpp：
#include "header.h"
int main(int argc, char const *argv[])
{
print_hello();
return 0;
}
void print_hello()
{
cout<<"hello world"<<endl;
}
my Makefile:
我的生成文件：
CC = g++
OBJ = main.o
HEADER = include/header.h
CFLAGS = -c -Wall
hello: $(OBJ)
$(CC) $(OBJ) -o $@
main.o: src/main.cpp $(HEADER)
$(CC) $(CFLAGS) $< -o $@
clean:
rm -rf *o hello
And the output of make is:
而 make 的输出是：
g++ -c -Wall src/main.cpp -o main.o src/main.cpp:1:20: fatal error: header.h: No such file or directory compilation terminated. Makefile:10: recipe for target 'main.o' failed make: *** [main.o] Error 1
g++ -c -Wall src/main.cpp -o main.o src/main.cpp:1:20: 致命错误: header.h: 没有这样的文件或目录编译终止。Makefile:10: 目标 'main.o' 的配方失败 make: *** [main.o] 错误 1
What mistakes I have made in here. It's frustrating. Really appreciate any advice!
我在这里犯了什么错误。这令人沮丧。真的很感激任何建议！
回答by Lightness Races in Orbit
You told the Makefile that include/header.hmust be present, and you told the C++ source file that it needs header.h… but you did not tell the compiler where such headers live (i.e. in the "include" directory).
你告诉 Makefileinclude/header.h必须存在，你告诉 C++ 源文件它需要header.h......但你没有告诉编译器这些头文件在哪里（即在“include”目录中）。
Do this:
做这个：
CFLAGS = -c -Wall -Iinclude
回答by abhiarora
You can either add a -Ioption to the command line to tell the compiler to look there for header files. If you have header files in include/directory, then this command should work for you.
您可以-I在命令行中添加一个选项来告诉编译器在那里查找头文件。如果include/目录中有头文件，那么这个命令应该对你有用。
gcc -Iinclude/
Since, you are using makefile, you can include this option in CFLAGSmacro in your makefile.
由于您正在使用makefile，您可以CFLAGS在 makefile 的宏中包含此选项。
CFLAGS = -Iinclude/ -c -Wall
OR
或者
You can include header files using #include "../include/header.h".
您可以使用#include "../include/header.h".
回答by daf
Perhaps change your include line:
也许更改您的包含行：
#include "include/header.h"
Assuming that's where your header exists - I'm making that assumption from your makefile
假设那是您的标头所在的位置 - 我是从您的 makefile 中做出这个假设的
