Why Do Empty C Classes Have a Non-Zero Size?

The Enigma Behind Non-Zero Size of Empty C Classes

In C , the notion that an empty class would occupy no memory may seem intuitive. However, this assumption is challenged by the peculiar behavior where even classes devoid of any members exhibit a non-zero size. Why does this apparent paradox exist?

As it turns out, the C standard explicitly forbids objects and their corresponding classes from having a size of zero. This stipulation stems from the inherent requirement to differentiate between distinct objects that potentially share the same memory space.

The standard ensures this distinction by mandating that all classes, regardless of their content, must have a minimum size of one. This prevents two disparate objects from having identical memory addresses, as such a condition would lead to unpredictable and undesired behavior.

Consequently, even when a class is devoid of any user-defined data members, it inherently contains implementation details such as virtual function tables and pointer members. These essential components contribute to the class's size, albeit invisible to the user, thus causing even empty classes to occupy a non-zero amount of memory.

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