Access extern variable in C++ from another file

Question

I have a global variable in one of the cpp files, where I am assigning a value to it. Now in order to be able to use it in another cpp file, I am declaring it as extern and this file has multiple functions that use it so I am doing this globally. Now the value of this variable can be accessed in one of the functions and not in the other one. Any suggestions except using it in a header file would be good because I wasted 4 days playing with that.

Answer 1

Sorry, I'm ignoring the request for answers suggesting anything other than the use of header files. This is what headers are for, when you use them correctly... Read carefully:

global.h

#ifndef MY_GLOBALS_H #define MY_GLOBALS_H  // This is a declaration of your variable, which tells the linker this value // is found elsewhere.  Anyone who wishes to use it must include global.h, // either directly or indirectly. extern int myglobalint;  #endif 

global.cpp

#include "global.h"  // This is the definition of your variable.  It can only happen in one place. // You must include global.h so that the compiler matches it to the correct // one, and doesn't implicitly convert it to static. int myglobalint = 0; 

user.cpp

// Anyone who uses the global value must include the appropriate header. #include "global.h"  void SomeFunction() {     // Now you can access the variable.     int temp = myglobalint; } 

Now, when you compile and link your project, you must:

1. Compile each source (.cpp) file into an object file;
2. Link all object files to create your executable / library / whatever.

Using the syntax I have given above, you should have neither compile nor link errors.