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Static variable become global???

 
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Franck26



Joined: 29 Dec 2007
Posts: 122
Location: Ireland

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Static variable become global???
PostPosted: Thu Mar 20, 2008 5:59 am     Reply with quote

Hello,
I don't know if my definition of a static variable is correct or not, but for me a static variable which is declared on a .c file is not accessible by the other .c files...
Am I right?

My problem is that I have declared a static variable at the top of a .c file (not inside a function) and it seems that my others .c files are able to access to this variable...
Is it normal?

example:

main.c:
Code:
#include <main.h>
#include <File1.c>
#include <File2.c>

void main()
{
   
   while(1)
   {
      ChangeVariable();
   }
}


file1.c:
Code:
static unsigned int Penguin;


file2.c:
Code:
void ChangeVariable(void)
{
   Penguin = 12;
}


When I do that there is no error and the variable Penguin is load with 12.
If in the main.c I include first file2.c and file1.c, the Penguin variable is not found and an error is generated. (which is normal).

Compiler: PCD 4.069.

Thanks for any comments.

Franck.
Ttelmah
Guest







PostPosted: Thu Mar 20, 2008 6:11 am     Reply with quote

Nothing to do with being static.
In C, any variable, that is declared _outside_ of any function, _is_ global. Declare your static variables, inside function declarations, and they become local static variables.
This is standard C syntax.
Remember 'include' files, are not separate programs. They are simply treated as if they are typed in at the point they are loaded.

Best Wishes
gribas



Joined: 21 Feb 2008
Posts: 21

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PostPosted: Thu Mar 20, 2008 6:51 am     Reply with quote

Hi Franck26,

The 'static' keyword isolates global variables from different compilation units. It also prevents a local function variable from being initialized twice.

I guess you only have one compilation unit. Use #module to achieve what you want.
Franck26



Joined: 29 Dec 2007
Posts: 122
Location: Ireland

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PostPosted: Thu Mar 20, 2008 8:01 am     Reply with quote

Hi,
Thanks for your answer.

I understand now: till now I was always working with several compilation units, but since I am using CCS, I was not able to do it...

I've tried the #module, it's working fine.

Thanks a lot.

Franck.
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