Question

Possible Duplicates:
What does “static” mean in a C program?
Static vs global

What does “static” mean in C, giving the following example: “static struct ……..”?

And what is the diffrence between this and “struct ……” without the “static”?

Answer 1

Outside a function, static makes whatever it’s applied to have file scope. For example:

int a_function(int x) { ... }

This function will have global linkage, and can be accessed by any other object file. You just have to declare it to use it, as is usually done in a header file:

int a_function(int x);

However, if you use static in the definition, then the function is visible only to the source file where it is defined:

static int a_function(int x) { ... }

In that case, other object files can’t access this function. The same applies to variables:

static int x;

This makes x a global variable, visible only within it’s source file. A “static struct” by itself doesn’t do anything, but consider this syntax:

struct {
    int x;
    int y;
} p1, p2;

This declares two global variables (p1 and p2), each of an “anonymous” struct type. If you append static:

static struct {
    int x;
    int y;
} p1, p2;

Then static applies to p1 and p2, making them visible only within their source file.