C ++如何将主类与头文件链接？

Question

This is as basic as it gets but I have a header file Test.h with a function prototype. Then a source code file with the function definition, Test.cpp. Lastly I have my Main.cpp file that calls the function in Test.cpp. The problem is that I get an error in Main.cpp stating that function1 is undefined. Can you see what I'm doing wrong?

Test.h

int function1(int);

Test.cpp

#include "Test.h"
#include <iostream>

int main(){
}

int function1(int i){
    std::cout << "fuction1(" << i << ")" << std::endl << "Returns: 1" << std::endl;

    return 1;
}

Main.cpp

#include <iostream>
#include "Test.h"

int main(){

    function1(5);
}

Also Test.cpp didn't compile until I added a main() function. I'm pretty fluent in java and this seems to contradict my thinking. In java I would only have one main method which is found in my main class. Other classes have a constructor. Please help me make this connection from java to c++.

Answer 1

You have to tell the compiler what it should link.

Firstly, remove the definition of main() in test.cpp because trying to put multiple non-static main() in global namespace in one executable will lead to link error.

Then, use your compiler properly. For example, if you use GCC,

g++ -o Main Main.cpp Test.cpp

or

g++ -c -o Main.o Main.cpp
g++ -c -o Test.o Test.cpp
g++ -o Main Main.o test.o