Are arrays variable-length by default on C?

Question

I was trying to make an array-based linear list, then I compiled this:

char size = 0;
char testarray[10];

int main() { 
    add('a'); add('b'); add('c');
    add('d'); add('e'); add('f');
    add('g'); add('h'); add('i');
    add('j'); add('k'); add('l');
    add('m'); add('n'); add('o');
    print();
    return 0;
} 

void add(char newchar) {
    testarray[++size] = newchar;
}

void print() {
    char i = 0;
    for (i = 0; i <= size; i++) {
        printf("%c ", testarray[i]);
    }
 }

And compiled it with gcc arraytest.c but the array works just fine. Does that mean arrays are variable-length by default? I thought it was a C99-only feature.

It was compiled under both Gentoo (gcc version 4.5.3 (Gentoo 4.5.3-r2 p1.1, pie-0.4.7) and Ubuntu (gcc version 4.6.1 (Ubuntu/Linaro 4.6.1-9ubuntu3).

Oh, and isn't this a bit dangerous?

Answer 1

No, they aren't variable size. You are just writing past the end of the array and clobbering some other memory. There are just no checks to make that obvious.