Question

I just came across some code which declares a struct within a C++ class as follows:

struct T 
{
       int data;
       T* next;
} array[0];

What does this kind of declaration do? What effect does putting “array[0]” at the end of the struct defintion have?

Answer 1

Ahh, it’s almost a “flexible array member”.

It was formalized in C99, but it’s an old C trick that creates a dynamic array. Allocate more memory for the object and you can store more elements in the array.

I think the use of a specific 0 there is a compromise, as actual [] flexible arrays were not in C89 or C++. The more canonical legacy use of this pattern is ...[1].