C ++中头文件的结构，并通过Terminal Mac进行编译

Question

I am confused on the structure of header files. In my program, the header file just has a forward declaration of int add(int x, int y); and in the main method, it calls the header file but does not initialize the forward declaration with any return statements, it just assigns the x and y particular values. In other words, how does the main method know what to do with the code inside the header files when the code in the header file does not have any return type. Any help will be greatly appreciated. If it helps, below is the code for the two files:

add.h:

int add(int x, int y); // function prototype for add.h

main.cpp:

#include <iostream>
#include "add.h" // this brings in the declaration for add()

int main()
{
using namespace std;
cout << "The sum of 3 and 4 is " << add(3, 4) << endl;
return 0;
}

and i compile it from Terminal by using g++ add.h main.cpp execution1; ./execution1 g++ add.h main.cpp execution1; ./execution1 and I get this error:

clang: warning: treating 'c-header' input as 'c++-header' when in C++ mode, this behavior is deprecated
clang: error: cannot specify -o when generating multiple output files
-bash: ./execution1: No such file or directory

Answer 1

It's a duplicate, see here: How to compile C++ program by command line on Mac

But you answer...

You can use c++ -c main.cpp , then c++ main.o , it will generate the .exe .

Bye!