MISRA C:2012  Rule-2.2:  (Required)			There shall be no dead code

Amplification:

Any operation that is executed but whose removal would not affect program behaviour constitutes dead code. Operations that are introduced by language extensions are assumed always to have an effect on program behaviour.

Note: The behaviour of an embedded system is often determined not just by the nature of its actions, but also by the time at which they occur.

Note: unreachable code is not dead code as it cannot be executed.

Exception:

A cast to void is assumed to indicate a value that is intentionally not being used. The cast is therefore not dead code itself. It is treated as using its operand which is therefore also not dead code.

Example Code:

#include <stdbool.h>
#include "misra.h"
#include "m3cmex.h"

static int16_t rule_0202a(int16_t p, int16_t q);

extern int16_t rule_0202( void )
{
    s16a = rule_0202a(3, 7);

    return 1;
}

static int16_t rule_0202a(int16_t p, int16_t q)                 /* 2980      */
{
    int16_t x = 0;                                              /* 2981      */
    int16_t y;

    p = 5;
    x = 5;
    y = q;                                                      /* 2983      */

    if (u16a > u16b)
    {
        u16c = u16b % u16a;                                     /* 2985      */
    }

    u16b = u16b & 0x01u;

    if (u16a == 1u)
    {
        u16c = u16a & u16b;                                     /* 2986      */
    }

    if (s16a > 20)
    {
        if (s16a > 10)                                          /* 2995 2991 */
        {
        }

        if (s16a < 5)                                           /* 2996 2992 */
        {
        }
    }

    s16a * s16b, s16c = 1;                                      /* 3110 3417 */
    s16b = 3, s16a * s16b;                                      /* 3426 3417 */

    s16a * s16b;                                                /* 3112      */

    (u32a > u32b) ? s16a = s16b : s16b;                         /* 3425 3226 */

    get_bool() && blb;                                          /* 3427      */

    return p + x;                                               /* 2984      */
}

QAC messages that encompass this guideline:

2980	The value of this function parameter is never used before being modified.
2981	This initialization is redundant. The value of this object is never used before being modified.
2982	This assignment is redundant. The value of this object is never used before being modified.
2983	This assignment is redundant. The value of this object is never subsequently used.
2984	This operation is redundant. The value of the result is always '%1s'.
2985	This operation is redundant. The value of the result is always that of the left-hand operand.
2986	This operation is redundant. The value of the result is always that of the right-hand operand.
2995	The result of this logical operation is always 'true'.
2996	The result of this logical operation is always 'false'.
3110	The left-hand operand of this ',' has no side effects.
3112	This statement has no side-effect - it can be removed.
3425	One branch of this conditional operation is a redundant expression.
3426	Right hand side of comma expression has no side effect and its value is not used.
3427	Right hand side of logical operator has no side effect and its value is not used.

(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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