[metadata]
id = "STR09-C"
type = "recommendation"
category = "STR"
number = 9
title = "Don't assume numeric values for expressions with type plain character"
description = """
For portable applications, use only the assignment=operator, the equality
operators==and!=, and the unary&operator on plain-character-typed or plain-wide-
character-typed expressions. This practice is recommended because the C Standard
requires only the digit characters (0–9) to have consecutive numerical values.
Consequently, operations that rely on expected values for plain-character- or
plain-wide-character-typed expressions can lead to unexpected behavior. However,
because of the requirement for digit characters, other operators can be used for
them according to the following restrictions:
"""
severity = "Low"
likelihood = "Unlikely"
priority = "P2"
level = "L3"
cert_version = "2016 Edition (Wiki)"
last_modified = "May 20, 2025"
[rules.cert_c.STR09-C]
enabled = true
[references]
wiki = "https://wiki.sei.cmu.edu/confluence/display/c/STR09-C.+Don%27t+assume+numeric+values+for+expressions+with+type+plain+character"