Why Does an Empty C Class Have a Size of 1 Byte?

Why isn't the Size of an Empty C Class Zero?

Despite its apparent emptiness, an empty class in C occupies a non-zero size. The standard explicitly prohibits objects and their corresponding classes from having a size of 0. This restriction stems from the need to prevent distinct objects from sharing the same memory address.

Take the following code snippet as an example:

<code class="cpp">#include <iostream>

class Test
{
};

int main()
{
    std::cout << sizeof(Test);
    return 0;
}</code>

Unlike your initial intuition that the output would be 0, it will actually return 1. This behavior is attributed to the standard's rule against zero-sized objects.

The underlying reason for this rule is to ensure that distinct objects have unique memory addresses. This is crucial for proper object identification and manipulation. If objects could have a size of 0, it would be possible for two separate objects to occupy the same memory location. This would lead to unpredictable and potentially disastrous consequences in your program.

Therefore, even though an empty class may not contain any visible data members, it still has a minimum size of 1 byte in order to maintain the standard's zero-size prohibition and guarantee the integrity of memory allocation.

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