As a preface, I'm using eclipse c++ as an IDE. And I'm using the c++0x11 standard. (So I can use mutex's) I'm very new to C++ but have done some C before and am very familiar with Java programming. Also, I know .h is usually not a type for C++ files.
I'm trying to include a private object member of stellad::KeyHook in my class stellad::Dispatcher and I get the following errors when building:
Building file: ../src/KeyHook.cpp
Invoking: GCC C++ Compiler
g++ -std=c++0x -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP -MF"src/KeyHook.d" -MT"src/KeyHook.d" -o "src/KeyHook.o" "../src/KeyHook.cpp"
In file included from ../src/KeyHook.h:10:0,
from ../src/KeyHook.cpp:8:
../src/Dispatcher.h:23:11: error: ‘KeyHook’ in namespace ‘stellad’ does not name a type
stellad::KeyHook keyhook;
^
src/subdir.mk:21: recipe for target 'src/KeyHook.o' failed
make: *** [src/KeyHook.o] Error 1
A lot of lines have been removed to reduce noise, such as unnecessary includes, prototypes and function declarations.
Dispatcher.h
/*
* Dispatcher.h
*/
#ifndef DISPATCHER_H_
#define DISPATCHER_H_
#include "KeyHook.h"
namespace stellad {
class Dispatcher {
private:
..
stellad::KeyHook keyhook;
public:
Dispatcher();
virtual ~Dispatcher();
..
};
} /* namespace stellad */
int main(int argc, const char* argv[]);
#endif /* DISPATCHER_H_ */
KeyHook.h
/*
* KeyHook.h
*/
#ifndef KEYHOOK_H_
#define KEYHOOK_H_
#include "Dispatcher.h"
namespace stellad {
class KeyHook{
private:
..
public:
KeyHook();
virtual ~KeyHook();
..
};
} /* namespace stellad */
#endif /* KEYHOOK_H_ */
It's caused by each file including the other.
If the first included is KeyHook.h, then before any declarations it includes Dispatcher.h. That includes KeyHook.h again but it finds that KEYHOOK_H_ is already defined and does not declare anything. Then the headers look like this:
// #include "KeyHook.h" from KeyHook.cpp
// #define KEYHOOK_H_
// #include "Dispatcher.h" from KeyHook.h
// #define DISPATCHER_H_
// #include "KeyHook.h" from Dispatcher.h
// KEYHOOK_H_ already declared
// end of #include "KeyHook.h" from Dispatcher.h
namespace stellad {
class Dispatcher {
private:
..
stellad::KeyHook keyhook; // KeyHook not declared here
public:
Dispatcher();
virtual ~Dispatcher();
..
};
} /* namespace stellad */
int main(int argc, const char* argv[]);
// end of #include "Dispatcher.h" from KeyHook.h
namespace stellad {
class KeyHook{
private:
..
public:
KeyHook();
virtual ~KeyHook();
..
};
} /* namespace stellad */
To solve this, you need to break the cyclic inclusion. KeyHook does not require Dispatcher, simply remove #include "Dispatcher.h" from it.