MISRA C:2012  Rule-10.5:  (Advisory)			The value of an expression should not be cast to an inappropriate essential type

Amplification:

The casts which should be avoided are shown in the following table, where values are cast (explicitly converted) to the essential type category of the first column.

Essential type category	from
to	Boolean	character	enum	signed	unsigned	floating
Boolean		Avoid	Avoid	Avoid	Avoid	Avoid
character	Avoid					Avoid
enum	Avoid	Avoid	Avoid*	Avoid	Avoid	Avoid
signed	Avoid
unsigned	Avoid
floating	Avoid	Avoid

* Note that an enumerated type may be cast to an enumerated type provided that the cast is to the same essential enumerated type. Such casts are redundant.

Casting from void to any other type is not permitted as it results in undefined behaviour. This is covered by Rule 1.3

Exception:

An integer constant expression with the value 0 or 1 of either signedness may be cast to a type which is defined as essentially Boolean. This allows the implementation of non-C99 Boolean models.

Example Code:

#pragma PRQA_MESSAGES_OFF 3112,3408

#include "misra.h"
#include "m3cmex.h"


extern int16_t rule_1005( void )
{
    (BL)bla;                                    /*      */
    (PC)bla;                                    /* 4301 */
    (N1)bla;                                    /* 4302 */
    (SI)bla;                                    /* 4303 */
    (UI)bla;                                    /* 4304 */
    (FT)bla;                                    /* 4305 */

    (BL)pca;                                    /* 4310 */
    (PC)pca;                                    /*      */
    (N1)pca;                                    /* 4312 */
    (SI)pca;                                    /*      */
    (UI)pca;                                    /*      */
    (FT)pca;                                    /* 4315 */

    (BL)n1a;                                    /* 4320 */
    (PC)n1a;                                    /*      */
    (N2)n1a;                                    /* 4322 */
    (SI)n1a;                                    /*      */
    (UI)n1a;                                    /*      */
    (FT)n1a;                                    /*      */

    (BL)sia;                                    /* 4330 */
    (PC)sia;                                    /*      */
    (N1)sia;                                    /* 4332 */
    (SI)sia;                                    /*      */
    (UI)sia;                                    /*      */
    (FT)sia;                                    /*      */

    (BL)uia;                                    /* 4340 */
    (PC)uia;                                    /*      */
    (N1)uia;                                    /* 4342 */
    (SI)uia;                                    /*      */
    (UI)uia;                                    /*      */
    (FT)uia;                                    /*      */

    (BL)fta;                                    /* 4350 */
    (PC)fta;                                    /* 4351 */
    (N1)fta;                                    /* 4352 */
    (SI)fta;                                    /*      */
    (UI)fta;                                    /*      */
    (FT)fta;                                    /*      */

    return 0;
}

QAC messages that encompass this guideline:

4301	An expression of 'essentially Boolean' type (%1s) is being cast to character type '%2s'.
4302	An expression of 'essentially Boolean' type (%1s) is being cast to enum type '%2s'.
4303	An expression of 'essentially Boolean' type (%1s) is being cast to signed type '%2s'.
4304	An expression of 'essentially Boolean' type (%1s) is being cast to unsigned type '%2s'.
4305	An expression of 'essentially Boolean' type (%1s) is being cast to floating type '%2s'.
4310	An expression of 'essentially character' type (%1s) is being cast to Boolean type, '%2s'.
4312	An expression of 'essentially character' type (%1s) is being cast to enum type, '%2s'.
4315	An expression of 'essentially character' type (%1s) is being cast to floating type, '%2s'.
4320	An expression of 'essentially enum' type (%1s) is being cast to Boolean type, '%2s'.
4322	An expression of 'essentially enum' type (%1s) is being cast to a different enum type, '%2s'.
4330	An expression of 'essentially signed' type (%1s) is being cast to Boolean type '%2s'.
4332	An expression of 'essentially signed' type (%1s) is being cast to enum type, '%2s'.
4340	An expression of 'essentially unsigned' type (%1s) is being cast to Boolean type '%2s'.
4342	An expression of 'essentially unsigned' type (%1s) is being cast to enum type '%2s'.
4350	An expression of 'essentially floating' type (%1s) is being cast to Boolean type '%2s'.
4351	An expression of 'essentially floating' type (%1s) is being cast to character type '%2s'.
4352	An expression of 'essentially floating' type (%1s) is being cast to enum type, '%2s'.

(c) The Motor Industry Research Association, 2012

QA C Source Code Analyser 8.1.2 MISRA C:2012 Compliance Module 1.0 © 2013 Programming Research www.programmingresearch.com

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