Is Defining a Zero-Length Array in C/C Valid and What are the Implications?

Implications of Defining a Zero-Length Array in C/C

Despite the lack of compiler errors in GCC, defining an array of size zero (e.g., int array[0];) is invalid in both C and C . According to ISO 9899:2011 6.7.6.2, the expression representing the array size must be a constant expression with a value greater than zero.

The absence of a warning in GCC may stem from its support for legacy code that used arrays without the [] syntax. However, it's crucial to understand that such arrays are not optimized out.

In C , a zero-length array, also known as an empty array, exists but has no elements. It can be useful in certain situations, such as tail-padding structures for alignment purposes. However, in general, it's not recommended to declare arrays with zero length, as it can lead to undefined behavior and errors.

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