error:undefined reference

[gaurav.gupta]

Hi
I have included a header file named Flag.h
the file has only this line of code
extern TBool iEnableLogging;

I have included the above header file in some other file.
and have used the iEnableLogging in this file.

But when I build the code it gives me an error :
"undefined reference to iEnableLogging "
Please help me why am I getting this error?
Regards
Gaurav Gupta

[lming]

explanation of extern.

The extern keyword declares a variable or function and specifies that it has external linkage (its name is visible from files other than the one in which it's defined). When modifying a variable, extern specifies that the variable has static duration (it is allocated when the program begins and deallocated when the program ends). The variable or function may be defined in another source file, or later in the same file. Declarations of variables and functions at file scope are external by default.

you need to check whether the corresponding library files is included.

[savaj]

extern is some what similar to forward declaration. If variable declared with extern keyword means that it is defined in some other files. Anyway external variable are global variables, and in symbian use of global variable is not recommanded. Alternatively you can declare this variable at class level (in base class, appview/appui).

[wizard_hu_]

The immediate soultion would be writing "TBool iEnableLogging;" into any .cpp file of yours (without the "extern", and outside of any method-scope). Then you will be able to access that single variable from whereever you have #include-d "Flag.h".
Anyway, use of global variables is discouraged, and the name "iEnableLogging" is mis-leading (it suggests a member variable, "EnableLogging" would be better for a global variable).