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Asked: 2026-05-11T12:30:03+00:00

I have a small problem with a define. I want to assign it to

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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 a 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.

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1 Answer

  1. 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.

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