I have created a CLog class for logging during program execution and, next to the declaration of CxApp theApp; because that way I can be pretty sure none of the other files will have started running yet, I have declared CLog g_TheLog; This comes up in the list of global variables, so I ought to be able to access it from anywhere, right? And, indeed, I can access it from xApp.cpp. But every time I try and access it from elsewhere, eg. with g_TheLog.AddToLog("Some message"); I am informed that g_TheLog is an undeclared identifier, and the left of .AddToLog() must point to a class, struct or union. In other words, it doesn''t recognise the global variable. But it WILL fill in the AddToLog() or whatever when I type g_TheLog. so Visual Studio knows what I mean even if the compiler doesn''t! Anyone have any clue what is going on here?

In any file that needs to use the global do:


extern CLog g_TheLog;

This basic question is answered far too often. I''m lazy, so here''s an example:

  /* A.c*/int Fish = 12345;  

/* A.h (without inclusion guards, you can do those)
*/
extern int Fish;
[/source]

  /* Something.c*/#include "A.h"  

Now you can use Fish in Something.c.

Thanks everyone. As it happens, this question has been answered in another recent thread, but with a weird title so I didn''t read it until after posting this, so I guess you''re right, NullAndVoid! Sorry for taking up your time, thankyou both!

Study this code:


----------------------------------

// File: clog.h
class Clog {
...
};
extern CLog g_TheLog;

----------------------------------

// File: CLog.c
#include "clog.h"
CLog g_TheLog;

--------------------------------

// Any other C++ source file that uses g_TheLog
#include "clog.h"
void
aFunction (){
g_TheLog.AddToLog("in aFunction().\n");
}