Understanding static variables declaration/initialization in C

Question

I have only one file in my project called test.c; the code below does not compile if I do not define "TRUE". I use vc. I just want to understand the behavior. Please throw some light on this aspect.

#ifdef TRUE
static int a; 
static int a = 1; 
#else 
static int a = 1; 
static int a; 
#endif 

int main (void) 
{ 
    printf("%d\n", a);
    return 0; 
}
-----------------------
#ifdef TRUE     // both ok
int a; 
int a = 1; 
#else           // both ok
int a = 1; 
int a; 
#endif

int main (void) 
{ 
    printf("%d\n", a);
    return 0; 
}

actually pasting the exact error message into your question is generally what you should be doing. — Winston Ewert
– Winston Ewert, Commented Dec 7, 2011 at 15:40

Joe · Accepted Answer · 2011-12-07 15:09:10Z

8

That is because you can not declare a variable after you have defined it. However you may define a variable after you declare it.

#ifdef TRUE
static int a; //Declaring variable a
static int a = 1; //define variable a
#else 
static int a = 1; //define variable a
static int a; //Error! a is already defined so you can not declare it
#endif

answered Dec 7, 2011 at 15:09

Joe

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2 Comments

Dan Fego Over a year ago

Well technically, you may define it after you declare it. :P But +1.

Joe Over a year ago

+1 for your comment, I was seeing variable and thinking struct.

Martin Stam · Accepted Answer · 2011-12-07 15:07:26Z

-3

Apparently, the compiler does not let you redefine a variable that has been initialized..

answered Dec 7, 2011 at 15:07

Martin Stam

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1 Comment

Thomas Over a year ago

you get in hells kitchen if you allow mulitple defines of the same.

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