c static

c static

 

 

static external variable/function:

only visible in local file,

you can define multiple static variable in different source file, and there will be no conflict,

 

static local variable:

variable only init once, and keep the value among multiple function calls,

 

variable default value:

int type default to 0,

 

variable store location:

store in static storage,

 

------

no extern for static

 

you should not use extern on static variable/function,

------

code:

ab.h:

// use extern to declare variable / function
extern int xa;
extern void fone();
extern void fxs();

 

a.c:

#include <stdio.h>
#include "ab.h"

// define variable xa
int xa = 10;

// static variable, only visible to local file
static int xs = 10;

// static function, only visible to local file
static void fxs2() {
	printf("%d\n", xs);
}

void ftwo() {
	// static local variable, default to 0, the init clause only execute once among multiple function calls,
	static int localx;
	static int localy=1000;
	printf("%d,%d\n",localx++,localy++);
}

main() {
	// use function that declare by extern
	fone();
	printf("%d,%d\n",xa, xs);
	fxs();
	fxs2();
	int i;
	for(i=0;i<5;i++) {
		ftwo();
	}
}

 

b.c:

#include <stdio.h>
#include "ab.h"

// static variable, only visible to local file
static int xs = 11;

// define function fone()
void fone() {
	// use variable that declare by extern
	xa = 11;
}
void fxs() {
	printf("%d\n",xs);
}

// static function, only visible to local file
static void fxs2() {
	fxs();
}

command to compile:

gcc a.c b.c

run:

./a.out

------