C ++编译错误：ld：找不到架构x86_64的符号clang：错误：链接器命令失败，退出代码为1（使用-v查看调用）

Question

Could someone please explain what am I doing wrong here? I am using macOS Here are the codes:

//test.h

#include <iostream>
#include <string>
class Test 
{
public:
    Test (std::string, std::string, int);

private:
    std::string par1;
    std::string par2;
    int par3;
};

//test.cpp

#include <string>
#include <string>
#include "test.h"

using namespace std;

Test::Test (string first, string second, int third)
{
    par1 = first;
    par2 = second;
    par3 = third;
}

//mainTest.cpp

#include <string>
#include <iostream>
#include "test.h"

using namespace std;

int main()
{
    Test test1 ("A", "B", 2);
}

The command I use to compile is :

g++ mainTest.cpp -o mainTest

Here is the error I got:

Undefined symbols for architecture x86_64:
  "Test::Test(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, int)", referenced from:
      _main in mainTest-056a8f.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

I have searched stackoverflow and google but I still can not figure what I did wrong. Thanks a lot

Answer 1

You didn't link with the test.o .

g++ -c test.cpp -o test.o
g++ mainTest.cpp test.o -o mainTest

or you can do them both at once:

g++ maintest.cpp test.cpp -o mainTest