[metadata]
id = "MEM36-C"
type = "rule"
category = "MEM"
number = 36
title = "Do not modify the alignment of objects by calling realloc()"
description = """
Do not invokerealloc()to modify the size of allocated objects that have stricter
alignment requirements than those guaranteed bymalloc(). Storage allocated by a
call to the standardaligned_alloc()function, for example, can have stricter than
normal alignment requirements. The C standard requires only that a pointer
returned byrealloc()be suitably aligned so that it may be assigned to a pointer
to any type of object with a fundamental alignment requirement. This
noncompliant code example returns a pointer to allocated memory that has been
aligned to a 4096-byte boundary. If theresizeargument to therealloc()function is
larger than the object referenced byptr, thenrealloc()will allocate new memory
that is suitably aligned so that it may be assigned to a pointer to any type of
object with a fundamental alignment requirement but may not preserve the
stricter alignment of the original object. #include <stdlib.h> void func(void) {
size_t resize = 1024; size_t alignment = 1 << 12; int *ptr; int *ptr1; if (NULL
== (ptr = (int *)aligned_alloc(alignment, sizeof(int)))) { /* Handle error */ }
if (NULL == (ptr1 = (int *)realloc(ptr, resize))) { /* Handle error */ } }
"""
severity = "Low"
likelihood = "Probable"
priority = "P2"
level = "L3"
cert_version = "2016 Edition (Wiki)"
last_modified = "May 05, 2025"
[rules.cert_c.MEM36-C]
enabled = true
[references]
wiki = "https://wiki.sei.cmu.edu/confluence/pages/viewpage.action?pageId=87152255"