Zero-length C-array binds to pointer type

Question

I recently wrote a function template which takes a reference to a C-array:

template 
void foo(T(&c_array)[N]);

Answer 1

The GCC Manual has a whole thing on zero length arrays. This is a GCC extension as is somewhat analogous to incomplete arrays.

Answer 2

Apparently ISO C forbids 0-length arrays, which is probably affecting how GCC tries to compile stuff. See this question for further details! zero length arrays vs. pointers

Answer 3

As arrays must have greater than zero length, if your compiler erroneously accepts a definition of a zero-sized array then you're "safely" outside of the scope of the language standard. There's no need for you to handle the edge case of N == 0.

This is true in C++: 8.3.5 [dcl.array]: If the constant-expression (5.19) is present, it shall be an integral constant expression and its value shall be greater than zero.

Answer 4

Speaking for C (and probably also C++ in this case), defining a zero-length array is undefined behavior, so GCC probably does this because a) nothing's stopping it, and b) it prevents errors like the ones you're trying to avoid.

Answer 5

Zero sized array are only legal in C as the last element of atruct. Anything else is pointless.

Answer 6

Zero-length arrays do not exist in C++. However if they did, here is how you could handle the case:

template <bool B, typename T>
struct disable_if;

template <typename T>
struct disable_if<false, T>
{
    typedef T type;
};

template <class T, size_t N>
typename disable_if<N == 0, void>::type foo(T(&c_array)[N])
{
    std::cout << "inside template\n";
}