C2065 undeclared identifier while assigning a define to an int

Question

Hi, I have a small problem with a define. I want to assign it to an integer variable but the compiler says it's undeclared.

Here's what the code looks like: defines.h

#ifndef DEFINES_H
#define DEFINES_H

#define MYDEFINE 2

#endif

myclass.h

namespace mynamespace {
class myClass {
    int someFunction();
};
}

myclass.cxx

#include "defines.h"
#include "myclass.h"
namespace mynamespace {
int myClass::someFunction() {
    int var = MYDEFINE;
    return 0;
}
}

In the line with the int assignment the compiler error takes place. I also tried to use another define, defined in the same header file as above, as a function parameter with the same effect. Any ideas? Thanks in advance.

I know using defines is kinda bad habit, but I only extend an existing project and I try to stay in their design ways.

EDIT: The error message simply is: Fehler 1 error C2065: 'MYDEFINE': nichtdeklarierter Bezeichner ... As you might see this is not the real source code, but I think I was very careful while putting together the question.

EDIT2: Thanks for the hint with the #warning. There were 2 files with the same name in different folders. I've no idea why the compiler didn't bring this up. Anyway, it works now. Thanks.

Answer 1

Some other header file also uses DEFINES_H?

One argument for #pragma once...

Answer 2

You should check whether the symbol MYDEFINE is really defined.

Check whether the header file where it is declared is really included (and compiled). Use #warning near the define to make sure it is compiled for myclass.cxx:

#ifndef DEFINES_H
#define DEFINES_H

#define MYDEFINE 2
#warning My define is defined

#endif

If it is not compiling (you'll not find the warning message in compilation log), make a search for DEFINES_H. It might be already defined somewhere else.

Answer 3

Let's put it all together:

    #ifndef DEFINES_H
    #define DEFINES_H
    #define MYDEFINE 2
    #endif

    namespace mynamespace {
    class myClass {
        int someFunction();
    };    // note ; missing in your code
    }

    namespace mynamespace {
    int myClass::someFunction() {
        int var = MYDEFINE;
        return 0;
    }

This compiles with no errors, so there is something wrong in your #includes.

Answer 4

It's probably complaining about you not having declared your class. Try #including "myclass.h"

Edit:

Oh, missing ';' after your class declaration.

Answer 5

You need to see what the preprocessor is doing to your code - try compiling myclass.cxx with the -P flag and examining the .i file so generated.