c++中如何链接头文件
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how to link header files in c++
提问by siri
I'm new to programming in C++ with header files. This is my current code:
我是 C++ 中带有头文件的编程新手。这是我当前的代码：
//a.h
#ifndef a_H
#define a_H
namespace hello
{
class A
{
int a;
public:
void setA(int x);
int getA();
};
}
#endif
//a.cpp
#include "a.h"
namespace hello
{
A::setA(int x)
{
a=x;
}
int A::getA()
{
return a;
}
}
//ex2.cpp
#include "a.h"
#include<iostream>
using namespace std;
namespace hello
{
A* a1;
}
using namespace hello;
int main()
{
a1=new A();
a1->setA(10);
cout<<a1->getA();
return 1;
}
When I try to compile it with g++ ex2.cpp, I get this error:
当我尝试使用 编译它时g++ ex2.cpp，出现此错误：
In function `main':
ex2.cpp:(.text+0x33): undefined reference to `hello::A::setA(int)'
ex2.cpp:(.text+0x40): undefined reference to `hello::A::getA()'
collect2: ld returned 1 exit status
Why isn't it working, and how can I fix it?
为什么它不起作用，我该如何解决？
回答by sbi
You don't link header files. You link object files, which are created by compiling .cppfiles. You need to compile all your source files and pass the resulting object files to the linker.
您不链接头文件。您链接目标文件，这些文件是通过编译.cpp文件创建的。您需要编译所有源文件并将生成的目标文件传递给链接器。
From the error message it seems you're using GCC. If so, I think you can dog++ ex2.cpp a.cpp
to have it compile both .cppfiles and invoke the linker with the resulting object files.
从错误消息看来，您正在使用 GCC。如果是这样，我认为您可以g++ ex2.cpp a.cpp
让它编译这两个.cpp文件并使用生成的目标文件调用链接器。
回答by Oliver Charlesworth
You need to compile and link bothsource files, e.g.:
您需要编译和链接两个源文件，例如：
g++ ex2.cpp a.cpp -o my_program
回答by Nikolai Fetissov
You need to compile and then link both source (.cpp) files:
您需要编译然后链接两个源 ( .cpp) 文件：
g++ -Wall -pedantic -g -o your_exe a.cpp ex2.cpp
回答by codaddict
Currently you are compiling and linking only ex2.cppbut this file has makes use of class def and function calls present in a.cppso you need to compile and link a.cppas well as:
目前您仅在编译和链接，ex2.cpp但此文件使用了类定义和函数调用，a.cpp因此您需要编译和链接a.cpp以及：
g++ ex2.cpp a.cpp
The above command will compile the source file(.cpp) into object files and link them to give you the a.outexecutable.
上面的命令会将源文件( .cpp)编译成目标文件并链接它们以提供a.out可执行文件。
