[metadata]
id = "EXP35-C"
type = "rule"
category = "EXP"
number = 35
title = "Do not modify objects with temporary lifetime"
description = """
The C11 Standard [ISO/IEC 9899:2011] introduced a new term:temporary lifetime.
This term still remains in the C23 Standard. Modifying an object with temporary
lifetime isundefined behavior. According to subclause 6.2.4, paragraph 8
[ISO/IEC 9899:2024] This definition differs from the C99 Standard (which defines
modifying the result of a function call or accessing it after the next sequence
point as undefined behavior) because a temporary object's lifetime ends when the
evaluation containing the full expression or full declarator ends, so the result
of a function call can be accessed. This extension to the lifetime of a
temporary also removes a quiet change to C90 and improves compatibility with
C++. C functions may not return arrays; however, functions can return a pointer
to an array or astructorunionthat contains arrays.Consequently, in any version
of C, if a function call returns by value astructorunioncontaining an array, do
not modify those arrays within the expression containing the function call.In
C99 and older, do not access an array returned by a function after the next
sequence point or after the evaluation of the containing full expression or full
declarator ends.
"""
severity = "Low"
likelihood = "Probable"
priority = "P6"
level = "L2"
cert_version = "2016 Edition (Wiki)"
last_modified = "May 06, 2025"
[rules.cert_c.EXP35-C]
enabled = true
[references]
wiki = "https://wiki.sei.cmu.edu/confluence/display/c/EXP35-C.+Do+not+modify+objects+with+temporary+lifetime"