about STATIC function

[dv007]

Any C expert out there could explain in detail about what different between STATIC function and
non-STATIC function?
For example in the file, Display.c, below

#include <stdio.h>
#include "display.h"
/* prototypes */
static void showA(); /*this is static function*/
void showB(); /*this is non-static fun.*/

/* function definition */
static void showA()
{
printf("Hola, I am from the Moon!");
}
void showB()
{
printf("Hello!, I am from Mercury planet");
}
Thank you in advance.
DV007

[sean345]

ShowA because it is static can ony be call from a function inside Display.c. Because ShowB is nonstatic it can be called from any module or source file in the project.

- Sean

[Prelude]

A static function can only be used in the source file that it was defined in. The static keyword means that it has file scope and cannot be used externally. A function has external linkage by default, so the programmer has to take action if they want it to be invisible to outside forces.

-Prelude

[dv007]

Thanx Sean+Prelude but talking about code efficience are they both the same???
The return address of both functions are allocated on STACK segment when called? or static function is on global segment (BSS segment I guess), and non-static function is on the STACK?
Again, thanx

[dv007]

Anyway, you guys's help are faster than speed of
light
DV007

[Prelude]

>but talking about code efficience are they both the same???
There may be an increase in efficiency when a function has file linkage, but I would imagine that in any practical sense they would be the same.

-Prelude

[Unregistered]

I am not an expert but I think both static and non-static functions
are allocated on STACK segment. Are you confuse with static
and non-static data. Static variable is put on Data segment while
non-static local variable is on STACK, but not apply to function.

BUD-WISER

[Prelude]

>I am not an expert but I think both static and non-static functions are allocated on STACK segment.
Correct, somewhat. The functions themselves are not popped onto the stack, activation records for them are. An activation record is a data structure which contains all of the information needed to invoke a function and maintain the call chain for previous functions. Also, the activation records may not even be on the stack. It's far more efficient to keep as much as possible of the activation record in registers. But for most practical uses, you can consider all functions themselves to be placed on the stack.

-Prelude