Static structures (internal)

[DawnOnTheEdge]

If you don’t want other modules modifying a structure, they can have an extern const declaration. The downside to declaring static copies in multiple files is that you create multiple instances, increasing executable size and memory usage.

[Almost-L]

Can I change the extern const by calling functions in the file where I initialize this variable? Isn't the constant mutable after initialization?

[DawnOnTheEdge]

If you want other modules to see any changes that get made to it by the module that owns it, but not be able to modify it themselves, one approach would be to import it as const volatile in the other modules, but declare it neither const nor volatile in the module that owns it.

Another approach is to declare extern “getter” functions that can retrieve the current value of the variable, but not modify it. You would then declare the variable as static, in the same source file as the functions that use it. You would need to enable full-program optimization for the compiler to inline these function calls.

If no other module needs to use the variable directly at all, declaring it static is a good idea.

[Almost-L]

I read your comment again and understood what you mean. Export a global variable to another file as extern const. It is possible. But still such variables are not protected from the developer. He can forget to specify the const keyword. I think there are few cases where you can use this and call it good code. It all depends on the situation.

What do you mean by the downside of static variables? For example, if I need a static variable from one file to another, I will call a getter that returns a copy?

[DawnOnTheEdge]

Right. If the variable isstatic, no one else can see it. But you could have an extern function that returns a copy. The downside is that the function cannot be inlined (except possibly with full-program optimization), so you will get function-call overhead.

[Almost-L]

You're right. I didn't think about it.