How to use extern in namespace?

Question

I am working on creating rLog for assembly as a DLL under windows, and I was getting undefined character errors related to some global characters in the rlog namespace. In particular, this is in RLogChannel.cpp:

namespace rlog {
...
  RLogChannel *_RLDebugChannel   = GetGlobalChannel( "debug",   Log_Debug );
  RLogChannel *_RLInfoChannel    = GetGlobalChannel( "info",    Log_Info );
  RLogChannel *_RLWarningChannel = GetGlobalChannel( "warning", Log_Warning );
  RLogChannel *_RLErrorChannel   = GetGlobalChannel( "error",   Log_Error );
...
 };

I suggested that the problem was that 1) they were not exported and 2) they were not declared in the header, so that other things could access them. So I added __declspec (dllexport) to them (via the RLOG_DECL macro), and in the header:

namespace rlog {
...
  RLOG_DECL extern RLogChannel *_RLDebugChannel;
  RLOG_DECL extern RLogChannel *_RLInfoChannel;
  RLOG_DECL extern RLogChannel *_RLWarningChannel;
  RLOG_DECL extern RLogChannel *_RLErrorChannel;
...
};

But no matter how I declare the variables in RLogChannel.cpp, I get an override error, even though my externing they are in the header ... What is the right way to do this? It sounds like it should be easy, but I can't wrap my head around me.

Edit: error message

  Error 12  error C2086: 'rlog::RLogChannel *rlog::_RLDebugChannel' : redefinition  rlog-1.4\rlog\RLogChannel.cpp   45  rlog

( 4 )

: , , , ( MSVC...), , -

Answer 1

- . , .

. , rlog.c rlog.h

--- (rlog.h) ---
#ifdef RLOG_DEFINES
#define EXTERN
#else
#define EXTERN extern
#endif


namespace rlog {
...
  RLOG_DECL EXTERN RLogChannel *_RLDebugChannel;
  RLOG_DECL EXTERN RLogChannel *_RLInfoChannel;
  RLOG_DECL EXTERN RLogChannel *_RLWarningChannel;
  RLOG_DECL EXTERN RLogChannel *_RLErrorChannel;
...
};


--- (rlog.c) ---
#define RLOG_DEFINES
#include "rlog.h"

...

--- (other .c files) ---
#include "rlog.h"

, , , , . , , extern ​​ ? . , .

, .

Answer 2

, . , ( :

--- (rlog.h) ---
#ifdef RLOG_DEFINES
#define RLOG_DECL __declspec(dllexport)
#else
#define RLOG_DECL __declspec(dllimport)
#endif


namespace rlog {
...
  RLOG_DECL extern RLogChannel *_RLDebugChannel;
  RLOG_DECL extern RLogChannel *_RLInfoChannel;
  RLOG_DECL extern RLogChannel *_RLWarningChannel;
  RLOG_DECL extern RLogChannel *_RLErrorChannel;
...
};


--- (rlog.c) ---
#define RLOG_DEFINES
#include "rlog.h"

namespace rlog {
...
  __declspec(dllexport) RLogChannel *_RLDebugChannel   = GetGlobalChannel( "debug",   Log_Debug );
  __declspec(dllexport) RLogChannel *_RLInfoChannel    = GetGlobalChannel( "info",    Log_Info );
  __declspec(dllexport) RLogChannel *_RLWarningChannel = GetGlobalChannel( "warning", Log_Warning );
  __declspec(dllexport) RLogChannel *_RLErrorChannel   = GetGlobalChannel( "error",   Log_Error );
...
 };


--- (other .c files) ---
#include "rlog.h"

. DLL, dllexport, , . , , dllimport.

, Maciej Jablonski