Why Are Zero-Length Arrays Problematic in C/C ?

Zero-Length Arrays in C/C : A Puzzling Error

Although defining an array of size zero may seem innocuous, it can lead to unexpected consequences in C/C . According to the ISO C standard (9899:2011 6.7.6.2), an array must have a size greater than zero.

This restriction applies to both plain arrays and variable length arrays (VLAs). In the case of VLAs, the expression determining the size of the array must have a value greater than or equal to one. If this expression evaluates to zero or a negative number, the behavior is undefined.

Despite this clear requirement, some compilers, such as GCC, do not complain when you define a zero-length array. This may be due to support for legacy code that has not been updated to use the newer array syntax with square brackets ([]). However, it is essential to understand that defining a zero-length array is an error.

Defining such an array does not result in a valid data structure. Attempting to use the array in any way will lead to undefined behavior and potential crashes. It is crucial to ensure that your code always defines arrays with valid, positive sizes.

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