Justification

Constant expressions enable tooling to check if indexing is in the defined array range. Also, compile time undefined array size can lead to uncontrollable excessive stack usage.

Example 1

#define CCBB_ARRAY_LEN  3
#define CCBB_ARRAY_SIZE (CCBB_ARRAY_LEN + 1)

static char ccbb_array[CCBB_ARRAY_SIZE] = ""; /* RIGHT */

Example 2

static void ccbb_f(int s)
{
   int a[s]; /* WRONG: array size depends on param.*/
   ...
}

Note

Allocate an array dynamically when using large arrays (> 1kB).