The standard says in 6.7.6.3:
A declaration of a parameter as ‘‘array of type’’ shall be adjusted to
‘‘qualified pointer to type’’, where the type qualifiers (if any) are
those specified within the [ and ] of the array type derivation. If
the keyword static also appears within the [ and ] of the array type
derivation, then for each call to the function, the value of the
corresponding actual argument shall provide access to the first
element of an array with at least as many elements as specified by the
size expression.
It's a feature introduced in C99. So there you have it: some_array must be at least 7 elements long.
As they say, there can't be a new standard without a new usage for the keyword static.
