static violation

[rajkumarmadhani]

I have one doubt..


a.h
static int x;

1.c
#include"a.h"
x=10;
printf("x=%d",x);

2.c
#include"a.h"
x=200;
printf("x=%d",x);

2.c
#include"a.h"
x=x+1;
printf("x=%d",x);


In the above said files static int is delcared in a.h file.this file is included in all 1.c , 2.c 3.c files.And able to compile the code & run it successfully.

But here my question is::

static is local to a.h file,,,but how we are to able access it..Is this static varibale access violation?

[GNU-Fan]

Hi,

"static" was a poor choice for a name in the C standard for this. In this context, it does not mean "unflexible", "constant" or "write-protected". A better choice would have been "local".

Instead it means: Let each "translation unit" have its own variable x. (A translation unit is a .c file together with all .h files it includes.)

[gerard4143]

I don't see your source file where you declare the static variable....

a.c

static int x = 0;

To compile the above

gcc -c a.c

And to compile one of your executables

gcc 1.c a.o -o thefirstone

How does this compile?

Oops, modifying 1.c to the below

1.c

#include <stdio.h>

extern int x;

int main(int argc, char**argv)
{
	x = 1234;
	return 0;
}

I think including a header file with the static declaration includes the static declaration in the main executable...I think.

[rajkumarmadhani]

No no...

static int x;

is declared in a.h header file.

#gcc 1.c 2.c 3.c

[gerard4143]

No no...

static int x;

is declared in a.h header file.

#gcc 1.c 2.c 3.c

But including a.h is the same as writing

static int x;

in each executable which shouldn't produce an error....

[gerard4143]

The result of including a.h is below:

#include <stdio.h>

static int x;/*the result of including a.h is this line*/

int main(int argc, char**argv)
{
	x = 789;
	fprintf(stdout, "x->%d\n", x);
	return 0;
}

Which is a valid C program.

[Cabhan]

gerard4143 is correct. When you run #include FILE, you are actually copying the entire contents of that file into your file. In this instance, each of your .c files has declared its own static int x.

Header files are designed to be included in the source code files. The source code files are designed to define all of the functionality (not always true when using macros, for instance, but usually true).

[rajkumarmadhani]

Yeah that's correct,
Thank you for information.....