external and static in c

[yemista]

Does anyone know what the result is of declaring a variable or function static external? What about external static?

[CodeCat]

Does that even work? They are both linkage declarations so I figure they would conflict and the compiler won't compile the code.

[yemista]

Yes they both work, but I dont know the difference, but there is a difference. External means global and static means local, so together they should conflict but I think it has a special meaning.

[yemista]

hey, im asking the questions here. dont look to me for explanation. What would two opposite keywords make combined?

[Hangin10]

hey, im asking the questions here. dont look to me for explanation. What would two opposite keywords make combined?

Berkus' post is a link...

[Love4Boobies]

Do you even know what those keywords mean?

[DeletedAccount]

. If a function is declared as static it cannot be referenced externally , what's the point of your question ?

Regards
Shrek

[Hangin10]

EDIT: Shrek explains it better below. This post was full of grammatical fail.

[DeletedAccount]

Hi,
extern is used to denote symbols that are not present the current object file and its the duty of the linkage editor (linker ) , to find out the symbol from a different module .

static has two meanings

when used for a variable : The variable maitains its values between function calls , just to give a demonstration , type this program in and find out the output

Code: Select all

#include <stdio.h>
#include <stdlib.h>
void func();
int main()
{
   func();
   func();
   func();
}
void func()
{
   static int var = 0 ;
   var++;
   printf("%d \n " , var );
}

when used for a function :
when used for a function it means that , function has scope restricted to the given file . It provides some sort of isolation .

However all these are very basic and should not be asked at this level .I now really understand Alboin's and Solar's sentiments. Please read a good C book , then your questions will make more sense .

Regards
Shrek

[Creature]

Doesn't she mean what they mean together? Something like

Code: Select all

extern static int foobar;

Which won't compile.

P.S.: I believe I've just advertised foobar2000.

[yemista]

Yes I do mean together. And its he. If extern static int foobar wont compile, static extern int foobar will, and Im wondering what that means.

[yemista]

Ok it looks like it wont compile. I dont know wat I was thinking of, but as soon as I find that example ill put it up.

[Craze Frog]

. If a function is declared as static it cannot be referenced externally , what's the point of your question?

The point is, what the hell does gcc do when you declare the same symbol as both extern and static?
This code is absolute nonsense, yet it compiles cleanly with gcc 4.3.2. At the very least it's nonsense that "static int oups; extern int oups;" compiles while "static extern int oups;" does not.

#include <stdio.h>

static int oups;
extern int oups;

int main (int argc, char *argv[]) {
printf("%d, %d", argc, oups);
return 0;
}

[yemista]

well i guess it does work then

[JamesM]

Why doesn't my code compile?

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const volatile int a = 3.1415f;

I don't understands!

Kthx.