[metadata]
id = "FLP37-C"
type = "rule"
category = "FLP"
number = 37
title = "Do not use object representations to compare floating-point values"
description = """
The object representation for floating-point values is implementation defined.
However, an implementation that defines the__STDC_IEC_559__macro shall conform
to theIEC 60559 floating-point standard and uses what is frequently referred to
asIEEE 754 floating-point arithmetic[ISO/IEC 9899:2024]. The floating-point
object representation used by IEC 60559 is one of the most common floating-point
object representations in use today.
All floating-point object representations use specific bit patterns to encode
the value of the floating-point number being represented. However, equivalence
of floating-point values is not encoded solely by the bit pattern used to
represent the value. For instance, if the floating-point format supports
negative zero values (as IEC 60559 does), the values-0.0and0.0are equivalent and
will compare as equal, but the bit patterns used in the object representation
are not identical. Similarly, if two floating-point values are both (the same)
NaN, they will not compare as equal, despite the bit patterns being identical,
because they are not equivalent.
Do not compare floating-point object representations directly, such as by
callingmemcmp()or its moral equivalents. Instead, the equality operators
(==and!=) should be used to determine if two floating-point values are
equivalent.
"""
severity = "Low"
likelihood = "Unlikely"
priority = "P3"
level = "L3"
cert_version = "2016 Edition (Wiki)"
last_modified = "May 05, 2025"
[rules.cert_c.FLP37-C]
enabled = true
[references]
wiki = "https://wiki.sei.cmu.edu/confluence/display/c/FLP37-C.+Do+not+use+object+representations+to+compare+floating-point+values"
cwe = []