One of the interview questions asked me to "write the prototype for a C function that takes an array of exactly 16 integers" and I was wondering what it could be? Maybe a function declaration like this:
void foo(int a[], int len);
Or something else?
And what about if the language was C++ instead?
In C, this requires a pointer to an array of 16 integers:
void special_case(int (*array)[16]);
It would be called with:
int array[16];
special_case(&array);
In C++, you can use a reference to an array, too, as shown in Nawaz's answer. (The question asks for C in the title, and originally only mentioned C++ in the tags.)
Any version that uses some variant of:
void alternative(int array[16]);
ends up being equivalent to:
void alternative(int *array);
which will accept any size of array, in practice.
The question is asked - does special_case()
really prevent a different size of array from being passed. The answer is 'Yes'.
void special_case(int (*array)[16]);
void anon(void)
{
int array16[16];
int array18[18];
special_case(&array16);
special_case(&array18);
}
The compiler (GCC 4.5.2 on MacOS X 10.6.6, as it happens) complains (warns):
$ gcc -c xx.c
xx.c: In function ‘anon’:
xx.c:9:5: warning: passing argument 1 of ‘special_case’ from incompatible pointer type
xx.c:1:6: note: expected ‘int (*)[16]’ but argument is of type ‘int (*)[18]’
$
Change to GCC 4.2.1 - as provided by Apple - and the warning is:
$ /usr/bin/gcc -c xx.c
xx.c: In function ‘anon’:
xx.c:9: warning: passing argument 1 of ‘special_case’ from incompatible pointer type
$
The warning in 4.5.2 is better, but the substance is the same.