new c++ error with file - c++

Question

I am 100% new at c++ so bear with me :)
I am getting an error with this file and not sure why. any help is appreciated.
#include <iostream>
using namespace std;
int main()
{
cout << "hi" << endl;
return 0;
}
------------ Build: Debug in 1600 (compiler: GNU GCC Compiler)-------------
g++ -o bin/Debug/1600 obj/Debug/main.o obj/Debug/src/test.o obj/Debug/test03.o
duplicate symbol _main in:
obj/Debug/main.o
obj/Debug/test03.o
ld: 1 duplicate symbol for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Answer 1

From the source files symbols are created. main in the .cpp file becomes _main as a symbol. During linking there can be only one main function, hence only one _main symbol is expected and allowed.
You have three object files that were created:
obj/Debug/main.o which contains main
obj/Debug/src/test.o
obj/Debug/test03.o which also contains main
Probably because you have a .cpp file for each of them and the command line or IDE you are using asked for them all to be compiled.
duplicate symbol _main
The text above is telling you that the linker (trying to make sense of all the compiled object (.o) files) found more than one main.
So the solution is to look at your IDE settings and remove the other files (or at least remove main from the other files) because you are only interested in compiling the one source file.

Answer 2

Its hard to tell what you're running from the question.
Here is how to build a simple C++ program using gcc
In
my_program.cpp
#include <iostream>
using namespace std;
int main()
{
cout << "hi" << endl;
return 0;
}
To compile to object files type
g++ -c my_program.cpp
To link (you'd normally have more files here)
g++ -o my_program my_program.o
So, this isn't very fun so most people use a build system like make, cmake, msbuild or whatever the CLion IDE uses.