Weird C++ error, unqualified ID, redeclaration - c++

Question

I want to create a project, I have 3 files, a test.cpp, something.h and a something.cpp. here they are:
test.cpp:
#include <bits/stdc++.h>
#define f cin
#define g cout
#include "something.h"
using namespace std;
int main(void)
{
int x;
register(x);
return 0;
}
something.h:
#ifndef __SOMETHING__H_
#define __SOMETHING__H_
#include <bits/stdc++.h>
void register(int x);
#endif
something.cpp:
#include "something.h"
void register(int x)
{
std::cout << x << '\n';
}
And here is the error I get:
In file included from test.cpp:4:0:
something.h:5:15: error: expected unqualified-id before ‘int’
void register(int x);
^~~
something.h:5:15: error: expected ‘)’ before ‘int’
test.cpp: In function ‘int main()’:
test.cpp:10:15: error: ISO C++ forbids declaration of ‘x’ with no type [-fpermissive]
register(x);
^
test.cpp:10:15: error: redeclaration of ‘int x’
test.cpp:9:9: note: ‘int x’ previously declared here
int x;
^
In file included from something.cpp:1:0:
something.h:5:15: error: expected unqualified-id before ‘int’
void register(int x);
^~~
something.h:5:15: error: expected ‘)’ before ‘int’
something.cpp:3:15: error: expected unqualified-id before ‘int’
void register(int x)
^~~
something.cpp:3:15: error: expected ‘)’ before ‘int’
Why does it tell me that I redefine x? When I just want to call register with it's value.

Answer 1

register is a reserved word in C++. Therefore, you have to give another (unreserved) name.
more information: Register keyword in C++ - Stack Overflow