LANG.STRUCT.ALIGNAS.IAS : Inconsistent Alignment Specifications

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

For the sake of this check:

The alignment specifications may be all on the same declaration, or on different declarations for the object.

alignas(exp1) and alignas(exp2) are considered to be consistent if exp1 and exp2 are integer constant expressions that evaluate to the same constant.

alignas(exp1) and alignas(exp2) are considered to be inconsistent if exp1 is a type name and exp2 is not identical to exp1, even if they resolve to the same alignment.

A declaration with no alignment specification is considered to be inconsistent with one that has an alignment specification, even if they resolve to the same alignment.

This class is a strict subset of Use of Alignas.

プロパティ

クラス名

Inconsistent Alignment Specifications

日本語クラス名

Inconsistent Alignment Specifications

クラス分類

信頼性 (reliability)

ニーモニック

LANG.STRUCT.ALIGNAS.IAS

カテゴリー

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

対応言語

C および C++ で利用可能です。

有効/無効設定

このワーニングクラスのチェックはデフォルトで無効になっており、プロジェクトには非正規の C向けAST が必要になります。有効にするにはプロジェクト設定ファイル（configuration file）に以下の WARNING_FILTER ルールと RETAIN_UNNORMALIZED_C_AST 設定を追加してください。

RETAIN_UNNORMALIZED_C_AST = Yes
WARNING_FILTER += allow class="Inconsistent Alignment Specifications"

注：非正規化された AST を継続して使用した場合、使用ディスク容量が増加し解析時間が長くなる可能性があります。

例

/* 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)
                                                */

関連のある設定ファイルパラメータ

設定ファイルの以下のパラメータがこのワーニングクラスのチェックに影響します。