bizarre C statement

Question

void test(int x[static 10]);  

int main()  
{  
    int a[]={1,2,3,4,5,6,7,8,9,10,11};  
    test(a);  
    return 0;  
}  

void test(int x[static 10])  
{  
    printf("%d",x[9]);  
}

I was looking for bizarre C statements. I found this one, But could not understand what is the use of static 10 in that statement. Is it same as int x[10]?

Another thing, you can use volatile also, in place of static e.g int x[volatile 10]
Anybody knows what is the use of this kinda declaration?

PS: Compiled using GCC 4.6.3,

score 5 · Answer 1 · answered Jul 17 '13 at 18:06

5

It's a hint for the compiler telling that the x pointer parameter points to the first element of an array of at least 10 elements.

For example:

test(NULL);  // undefined behavior

answered Jul 17 '13 at 18:06

ouah

142,963
15
272
331

is this valid C++? how useful is it in the optimization (ie like inline or better?) - just trying to get more info, thanks – im so confused Jul 17 '13 at 18:08
yeah, but program run without error, warning even if provided arguments are NOT at least 10 – Akash Shende Jul 17 '13 at 18:08
@ChrisCM see my example, passing a `NULL` argument is undefined behavior. – ouah Jul 17 '13 at 18:09
hm.. @ouah as in, compile time check? how does it differ from passing NULL into (int x[]) ? – im so confused Jul 17 '13 at 18:11
@AK4749 even assuming `test` function body is empty, `test(NULL);` is UB. – ouah Jul 17 '13 at 18:12
1

@AK4749 regarding C++, to my knowledge this feature does not exist in C++ – ouah Jul 17 '13 at 18:12
got it - so no compile time safety, but provides runtime optimization possibility at the cost of broadening the scope of UB? Thanks for the clarifications – im so confused Jul 17 '13 at 18:13
what about `int x[volatile]` guys ? – Akash Shende Jul 17 '13 at 18:16
@AkashShende `void foo(int p[volatile 10]);` is equivalent to `void foo(volatile int *p);` – ouah Jul 17 '13 at 18:19

bizarre C statement

1 Answers1