[metadata]
id = "MSC19-C"
type = "recommendation"
category = "MSC"
number = 19
title = 'For functions that return an array, prefer returning an empty array over a null value'
description = '''
Many functions have the option of returning a pointer to an object or returning
NULL if a valid pointer cannot be produced. Some functions return arrays, which
appear like a pointer to an object. However, if a function has the option of
returning an array or indicating that a valid array is not possible, it should
not return NULL . Instead, the function should return an empty array. Often,
code that calls a function that returns an array intends merely to iterate over
the array elements. In this case, the calling code need not change—iterating
over the elements works correctly even if the returned array is empty, so the
calling code need not check the return value for NULL .
This situation is complicated by the fact that C does not keep track of the
length of an array. However, two popular methods have emerged to emulate this
behavior. The first is to wrap the array in a struct with an integer storing the
length. The second is to place a sentinel value at the end of the data in the
array. This second approach is most commonly manifested in null-terminated byte
strings (NTBSs).
'''
severity = "Low"
likelihood = "Unlikely"
priority = "P2"
level = "L3"
cert_version = "2016 Edition (Wiki)"
last_modified = "Unknown"
[rules.cert_c.MSC19-C]
enabled = false
[references]
wiki = "https://cmu-sei.github.io/secure-coding-standards/sei-cert-c-coding-standard/recommendations/miscellaneous-msc/msc19-c"
cwe = []