C++ Multiple definitions error - c++

I'm getting a bunch of errors for a simple c++ hello world program.
#include <iostream>
using namespace std;
int main()
{
cout << "Hello world!" << endl;
return 0;
}
All the solutions iv'e seen for this were just confusing and didn't help. Im using the Code Blocks IDE.

Related

Why does codeblocks ide raise: fatal error: iostream: no such file or directory

when I run this test code:
#include <iostream>
using namespace std;
int main()
{
cout << "Hello world!" << end1;
return 0;
}
with a more than less than around iostream just can't use it on stackover flow.
I got this code from an old book (2014) it might be outdated. I've never used C++ before how do I fix this.

Declaring multiple ifstream makes code crash

I just installed mingw on my Windows 10 computer and wanted to code a program that read two files. I immediately faced a frustrating bug with ifstream: when I declare more than one ifstream, the program seems to crash (nothing is logged although the first line cout some text).
The following code compiles and logs "test" in the console:
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
cout << "test" << endl;
ifstream test;
return 0;
}
The following code compiles but seems to crash at runtime, nothing is logged:
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
cout << "test" << endl;
ifstream test;
ifstream test2;
return 0;
}
I tested the exact same codes on a macOS Mojave and both codes work and log "test".
I guess the issue is related to the g++ installation but I'd like to know what's really happening and how I can fix this on Windows.

Program not executing after instanciating a class from imported library

I'm trying to use the library ZBar to read QRCode with c++. I am not an expert about this language. I have the following problem:
#include <iostream>
#include <zbar.h>
using namespace std;
using namespace zbar;
int main()
{
cout << "Hello World!" << endl;
//Image image;
return 0;
}
This code does actually print the "Hello World" as expected. But if I remove the comment, obtaining the following code:
#include <iostream>
#include <zbar.h>
using namespace std;
using namespace zbar;
int main()
{
cout << "Hello World!" << endl;
Image image;
return 0;
}
Everything is still compiled correctly, with no errors or warnings, but I don't obtain any output!! The program reaches the end without executing any instruction!
I just used this code to semplify, but the problem actually is that, as soon as I add an instruction using classes from zbar, it seems like I am "clearing" the main! How is it possible? What should I do? Thank you!

A lot of mistakes in xiosbase file. Even Hello World doesn't run. C++

I was writing a small program in C++ to translate infix notation to polish notation and RPN, but after running it a ton of mistakes popped up in xiosbase file. I tried to run a simpler code but xiosbase mistakes are still there.I am just starting to code and I have no idea how header files work (and any other file except the one I am writing).
This is Hello World.
#include <iostream>
#include <cstdlib>
using namespace std;
int main()
{
cout << "Hello, world!" << endl;
system("pause");
return 0;
}
and here are all the mistakes I get:
Keep in mind that I am a massive newbie

Using GetCpInfo

I am trying to write a small program to run GetCpInfo, but am getting an identifier not found error . I am including windows.h and using visual studio. IntelliSense is autocomplete for me when I type in GetCp. Here is my code.
#include <iostream>
#include <windows.h>
using namespace std;
int main()
{
LPCPINFO cpinfo;
cout << "Hello World!" << endl;
bool test = GetCpInfo(37, cpinfo);
int x;
cin>>x;
return 0;
}
Two problems:
The function is named GetCPInfo. Remember that the language is case sensitive.
You are passing an uninitialized pointer.
You need the following:
CPINFO cpinfo;
bool succeeded = GetCPInfo(37, &cpinfo);