C/C++ namespace in header issue - c++

Question

I am trying to implement a Websocket Server. I am using the libwebsockets library.
ConnectionServer.c file has setup code for the library and main() function (I don't see anything of importance to post here.) This file includes 1 file for the received data callback called:
dmserver_callback.cpp.
This file then includes another file (my custom parser file) called:
data_parser.cpp.
This file then includes a file called definitions.h (the source of the problem).
Just bear with me; I understand that including files (daisy chaining; so to speak) probably isn't the best way to do this, and I more than likely should be using header files and such. One question I have is that is this particularly necessary?
To clarify, everything is working as intended until I try to add my own parsing mechanism.
The definitions.h file is as follows:
namespace EngineDefinitions {
enum Version {
Major = 1,
Minor = 2
}; //Version;
namespace Server {
enum enum_Server {
MAX_PLAYERS = 200,
MAX_TABLES = 42, // 3 tables per row.
MAX_TABLE_PLAYERS = 10,
GAME_PORT = 2040, //2042
MAX_PARAMS = 10
}; //Server;
};
namespace Login {
enum enum_Login {
USERNAME = 1,
PASSWORD = 2
}; //Login;
};
};
My error is:
definitions.h(1): error C2061: syntax error : identifier 'EngineDefinitions'
I loaded the exact same header in a new Win32 Console Project in Visual C++ 2010 Express and there it works. The only difference I see is the main file (where int main function resides).
In the project that the header file works is called:
ConectionServer.cpp (C++)
and the main project file that doesn't work is named:
ConnectionServer.c (C)
Does this have something to do with the file being compiled in C vs C++?
I think that the libwebsocket library is coded in C.
I can't recall if I created the project files in exactly the same manner or not.
P.S. Please let me know if there is any other information I can provide to help.
EDIT: I also realize you're not supposed to define types inside a header file (eg: enums).
I DID try to separate the source into .cpp and a header file using the extern enum
with no difference. In fact, got more errors (redefinitions) than I bargained for when trying to use them.

Answer 1

You need to understand that C++ and C are different languages. When you include the header file in a .cpp file, the compiler will try to compile the .h as C++ code. C++ supports namespaces, so everyone is happy. But when you try to include the .h from the .c file (which is what is actually happening if you follow the #includes), the compiler attempts to compile the .h as C code, yet fails because namespaces do not exist in C.
A common way to solve this problem is to use predefined macros. __cplusplus is defined when compiling as C++ code, and not defined when compiling as C code (obviously).
You could do this:
#ifdef __cplusplus
namespace EngineDefinitions {
#endif
enum Version {
Major = 1,
Minor = 2
}; //Version;
#ifdef __cplusplus
namespace Server {
#endif
enum enum_Server {
MAX_PLAYERS = 200,
MAX_TABLES = 42, // 3 tables per row.
MAX_TABLE_PLAYERS = 10,
GAME_PORT = 2040, //2042
MAX_PARAMS = 10
}; //Server;
#ifdef __cplusplus
};
#endif
#ifdef __cplusplus
namespace Login {
#endif
enum enum_Login {
USERNAME = 1,
PASSWORD = 2
}; //Login;
#ifdef __cplusplus
};
#endif
And of course, you lose the ability of namespaces in C anyways.

Answer 2

C does not have namespaces. For Real.

Answer 3

You cannot include a C++ file in a C file (unless it has been prepared for such use). If you then try to compile the C file, it'll try to compile even the C++ file as C. Instead, use separate compilation and header files.
Note that C does not understand namespaces.