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CodeSonar® 9.2p0 CONFIDENTIAL CodeSecure Inc
C and C++

LANG.STRUCT.ALIGNAS.IAS : Inconsistent Alignment Specifications

Summary

An object (variable or a field) is declared with multiple alignment specifications that are not consistent.

For the sake of this check:

This class is a strict subset of Use of Alignas.

See also Too Many Alignment Specifiers.

Properties

Class Name Inconsistent Alignment Specifications
Significance reliability
Mnemonic LANG.STRUCT.ALIGNAS.IAS
Categories
MisraC2025 MisraC2025:1.4 Emergent language features shall not be used
  MisraC2025:8.15 All declarations of an object with an explicit alignment specification shall specify the same alignment
MisraC2023 MisraC2023:1.4 Emergent language features shall not be used
  MisraC2023:8.15 All declarations of an object with an explicit alignment specification shall specify the same alignment
Misra2012 Misra2012:1.4 Emergent language features shall not be used
  Misra2012:8.15 All declarations of an object with an explicit alignment specification shall specify the same alignment
CERT-C CERT-C:MSC23-C Beware of vendor-specific library and language differences
Availability Available for C and C++.
Enabling Checks for this warning class are disabled by default, and require the unnormalized C ASTs for the project. To enable them, add the following WARNING_FILTER rule and RETAIN_UNNORMALIZED_C_AST specification to the project configuration file. 
RETAIN_UNNORMALIZED_C_AST = Yes
WARNING_FILTER += allow class="Inconsistent Alignment Specifications"
Note that retaining the unnormalized ASTs will increase the disk space used to store the project representation, and may make the analysis take longer.

Example 

/* LANG.STRUCT.ALIGNAS.IAS.c */

#include "LANG.STRUCT.ALIGNAS.IAS.h"

alignas(8) int hc_same_const;                        /* ('Use of Alignas' warning issued when enabled) */
alignas(4) int hc_diff_const;                        /* ('Use of Alignas' warning issued when enabled) */
alignas(2*4) int hc_same_const_exp;                  /* ('Use of Alignas' warning issued when enabled) */
int hc_one_spec;                                /* 'Inconsistent Alignment Specifications' warning issued here:
                                                 * - explicit alignment specified in .h file, but none here
                                                 */
alignas(4) int hc_type_const;                        /* ('Use of Alignas' warning issued when enabled) */
alignas(alignof(int)) int hc_type_alignof_type;      /* ('Use of Alignas' and 'Use of Alignof' warnings issued when enabled) */

/* LANG.STRUCT.ALIGNAS.IAS.h */

#include <stdalign.h>

extern alignas(8) int h_one_spec;                      /* ok: single declaration; single alignas specification
                                                        * ('Use of Alignas' warning issued when enabled)
                                                        */
extern alignas(8) alignas(4) int h_diff_const; /* 'Inconsistent Alignment Specifications' warning issued here
                                                * - two different alignments in the same declaration
                                                * ('Too Many Alignment Specifiers' and 'Use of Alignas' warnings
                                                * also issued when enabled)
                                                */
extern alignas(8) int hc_same_const;                   /* ok: alignment specified in .c file is 8
                                                        * ('Use of Alignas' warning issued when enabled)
                                                        */
extern alignas(8) int hc_diff_const;           /* 'Inconsistent Alignment Specifications' warning issued here
                                                * - alignment specified in .c file is 4
                                                * ('Use of Alignas' warning also issued when enabled)
                                                */
extern alignas(8) int hc_same_const_exp;               /* ok: alignment specified in .c file is 2*4 (==8)
                                                        * ('Use of Alignas' warning issued when enabled)
                                                        */
extern alignas(8) int hc_one_spec;

extern alignas(int) int hc_type_const;         /* 'Inconsistent Alignment Specifications' warning issued here
                                                * - alignment specified in .c file is 4
                                                * - a warning is issued even if the alignment of int is 4
                                                * ('Use of Alignas' warning also issued when enabled)
                                                */
extern alignas(int) int hc_type_alignof_type;  /* 'Inconsistent Alignment Specifications' warning issued here
                                                * - alignment specified in .c file is alignof(int)
                                                * ('Use of Alignas' warning also issued when enabled)
                                                */

Relevant Configuration File Parameters

The following configuration file parameters affect checks for this warning class.

 

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