Question

I use a global variable (an object of a class) and define it as follows:

//foo.h
extern class_name obj_name;
//foo.cpp
class_name obj_name("directory of a .ttf file");

I included foo.h in my main.cpp where my main() function resides.

The problem is that I am not very comfortable with initializing it there , since it is not inside a function. It’s out in the open. I would have preferred calling an “init()” function that initializes the object like:

object_name = class_name(parameters);

from the main() function.

But the class is a 3rd party one and it doesn’t accept objects being created without us providing parameters for the constructor. Maybe it doesn’t have a default no-parameter constructor.

Is it good coding style to do what I did above?

Answer 1

No.

Don’t use globals in C++ without very good reason.

• You’ll run into the “static initialisation order fiasco”.
• You’ll get ugly spaghetti code.
• Your code will be difficult to test.

This is especially true if your global is of a 3rd party type.

Consider using something nicer like a factory method allowing lazy initialization.
Or just pass the object around to functions that need it.

Also consider wrapping that 3rd party class with your own – only providing the minimal interfaces needed to test it, and use a pointer to that abstract base class. (Or if the 3rd party library supports it – use the most minimal interface they provide that you can get away with using)