在同一个 header 文件中声明、初始化和使用全局变量

Question

I am actually trying to use a variable that is initialized in a header file(say xh) and want to use same variable inside inlined code in the same header file. The same variable is modified in another file (say yc). How can i do this? I would like to know a good way of doing this.

Answer 1

Using the extern reserved word.

Never create variables in '.h' files, it's a bad practice that leads to bugs. Instead, declare them as extern everywhere you need to use them and declare the variable itself only in a single '.c' file where it will be instantiated, and linked to from all the other places you use it.

Answer 2

You can declare the global variable in the header file as extern , and then define it inside a code-module (ie, ".c" file). That way you won't end up with multiple definition errors thrown by the linker.

So for example in your header file, a globally available int named my_global_var would have a declaration in ah file that looks like:

extern int my_global_var;

Then inside a single.c file somewhere you would define and initialize it:

int my_global_var = 0;

Now you can use my_global_var in any other code module that includes the appropriate header file and links with the proper.c file containing the definition of the global variable.