4 replies to this topic

[csepraveenkumar]

can an array declared as static in one function be accessed by another function by means of pointers?
when a pointer to a variable is passed to a function, is the actual pointer passed or a copy of the pointer?

[dcs]

csepraveenkumar said:

can an array declared as static in one function be accessed by another function by means of pointers?

Yes.

(Try to be a little more specific with 'static' if possible.)

csepraveenkumar said:

when a pointer to a variable is passed to a function, is the actual pointer passed or a copy of the pointer?

Copy. (Assuming C, which only has pass-by-value. C++ can be different.)

[dargueta]

Quote

can an array declared as static in one function be accessed by another function by means of pointers?

Not necessarily. For example:

int main(void)
{
    char *p;
    p = foo();
    bar(p);
    
    return 0;
}

char *foo(void)
{
    char str[] = "abcdef";
    return str;
}

void bar(char *ptr)
{
    //FAIL - PTR DOES NOT EXIST ANYMORE
    printf("%s",ptr);
}

However, this will work (though it's bad style).

int main(void)
{
    char *p;
    p = foo();
    bar(p);
    
    return 0;
}

char *foo(void)
{
    static char str[] = "abcdef";
    return str;
}

void bar(char *ptr)
{
    //This is ok
    printf("%s",ptr);
}

The reason is that local variables declared as static are not stored on the stack as regular locals are, so they're permanent across function calls. A non-static variable is trashed as soon as its containing function returns. The address will still be valid, but it'll point to junk.

[ZekeDragon]

Quote

can an array declared as static in one function be accessed by another function by means of pointers?

I think that's what he was asking. :)

[dargueta]

Eh...it's kinda ambiguous, at least to me. Can't hurt to show examples of both, now can it?