What happens if I define a 0-size array in C/C++?

Question

Just curious, what actually happens if I define a zero-length array int array[0]; in code? GCC doesn\'t complain at all.

Sample Program

Answer 1

An array cannot have zero size.

ISO 9899:2011 6.7.6.2:

If the expression is a constant expression, it shall have a value greater than zero.

The above text is true both for a plain array (paragraph 1). For a VLA (variable length array), the behavior is undefined if the expression's value is less than or equal to zero (paragraph 5). This is normative text in the C standard. A compiler is not allowed to implement it differently.

gcc -std=c99 -pedantic gives a warning for the non-VLA case.