Headers and Include

[Roundthecorner]

I read the "Headers and Includes" article and wanted to try it out, but my compiler gives me an error, and I have no idea why. I use Code::Blocks and the GNU GCC Compiler.

All my files are in the same folder

//myclass.h
#ifndef MYCLASS_H_INCLUDED
#define MYCLASS_H_INCLUDED

class MyClass
{
public:
  void foo();
  int bar;
};

#endif // MYCLASS_H_INCLUDED 

next one

//myclass.cpp
#include "myclass.h"

void MyClass::foo()
{
}
int main(){}

I tried to do it without the main-function like in the article, but i get the error "undefined refrence to WinMain@16"
and the last piece of code

//main.cpp
#include "myclass.h"  // defines MyClass

int main()
{
  MyClass a; // no longer produces an error, because MyClass is defined
  a.foo();
  return 0;
}

Now i compiled the myclass.cpp but when compiling main.cpp it gives me "undefined refrence to Myclass::foo()"

I have no Idea what's going on.

[3qX21hU5]

You can only have one entry point in your program (Only one int main()).

Delete int main inside your myclass.cpp

[Roundthecorner]

Now myclass.cpp does not compile "undefined refrence to WinMain@16" and the main.cpp gives me the same error.
Do you think it's maybe a code::blocks problem? Should I go to the CB Forum?

[giblit]

Maybe because you have no constructor for your class and you are trying to construct one on line 6 in your main function.

[Disch]

You set up your project incorrectly.

You have it set up to be a Win32 application instead of a console application. As a result, it's looking for "WinMain" as the entry point instead of "main".

Go in your project settings and find out where that option is (I don't remember where it is in C::B) -- it should be like a drop box with several options, one of which being "Console application" or something to that effect.

If you change that setting to be a console app, the original code you posted should work just fine.

Either that... or scrap this project entirely, start a new one, and make sure you choose the console option in the setup wizard.

Or if you don't want a console app, get rid of main() entirely and replace it with WinMain:

int WINAPI WinMain(HINSTANCE inst, HINSTANCE prev, LPSTR cmd, int show)
{
   // program starts here -- but be warned there is no console

   return 0;
}

[TheIdeasMan]

giblit wrote:

Maybe because you have no constructor for your class and you are trying to construct one on line 6 in your main function.

The compiler creates a default constructor and uses it when no constructor is provided - so it shouldn't be a source of error in this particular situation.

Confusingly however, this is an error:

MyClass a();

because there is no MyClass() constructor.

Having said that, IMO it is usually a good idea to provide a constructor - one normally needs to initialise variables with an initialiser list.

[Disch]

I just want to reiterate that this has nothing to do with the constructor or the class, or his header.

This is strictly a problem with the entry point.

@Roundthecorner: Your code is fine. You just need to tell C::B that you are making a console program and not a WinAPI program. Right now it thinks you are doing the latter which is why you're getting the error.

[giblit]

Did not know that they create a constructor by default if non provided. I always had a constructor because I find it odd to create an object without actually creating one seems to me like he is just using it as a container or something where a namespace might be more handy.

[Roundthecorner]

Thank you all very much (especially Disch). Works like a charm now. =) It's time to start my very first bigger project^^