MISRA C:2012  Rule-14.2:  (Required)			A for loop shall be well-formed

Amplification:

The three clauses of a for statement are the:

First clause which

• Shall be empty, or
• Shall assign a value to the loop counter, or
• Shall define and initialize the loop counter (C99).

Second clause which

• Shall be an expression that has no persistent side-effects, and
• Shall use the loop counter and optionally loop control flags, and
• Shall not use any other object that is modified in the for loop body.

Third clause which

• Shall be an expression whose only persistent side-effect is to modify the value of the loop counter, and
• Shall not use objects that are modified in the for loop body.

There shall only be one loop counter in a for loop, which shall not be modified in the for loop body.

A loop control flag is defined as a single identifier denoting an object with essentially Boolean type that is used in the Second clause.

The behaviour of a for loop body includes the behaviour of any functions called within that statement.

Exception:

All three clauses may be empty, for ( ; ; ), so as to allow for infinite loops.

Example Code:

#pragma PRQA_MESSAGES_OFF 2982

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

extern int16_t rule_1402( void )
{
    int16_t i;
    int16_t j;

    for (;;)
    {
        if (bla)
        {
            break;
        }
    }

    bla = get_bool();

    for (i = 0; i < 10; ++i)
    {
    }

    i = 0;
    for (     ; i < 10; ++i)
    {
    }

    for (s16a = 0; s16a < 10; ++s16a)                                           /* 2461           */
    {
    }

    j = get_s16();
    for (i = 0; j < 10; ++j)                                                    /* 2462           */
    {
        ++i;
    }

    j = get_s16();
    for (i = 0; i++ < 10; ++j)                                                  /* 2463 3440      */
    {
    }

    for (i = 0; ++i < 10; ++i)                                                  /* 2464 3440      */
    {
    }

    for (i = 0; (i < 10) || bla; ++i)
    {
    }

    for (i = 0; i < 10; ++i)
    {
        ++i;                                                                    /* 2469           */
    }

    for (i = get_s16(); i < s16a; ++j)                                          /* 2471           */
    {
        ++i;
    }

    for (i = 0, j = 5; (i < get_s16()) && (j < 10); ++i, ++j)                   /* 2472 3418 3418 */
    {
    }

    return 1;
}

QAC messages that encompass this guideline:

2461	Loop control variable, %s, has file scope.
2462	The variable initialized in the first expression of this 'for' statement is not the variable identified as the 'loop control variable' (%s).
2463	The variable incremented in the third expression of this 'for' statement is not the variable identified as the 'loop control variable' (%s).
2464	Loop control variable, %s, modified twice in for-loop header.
2467	Loop control variable, %s, is not modified inside loop.
2469	Loop control variable in this 'for' statement, %s, is modified in the body of the loop.
2471	Unable to identify a loop control variable.
2472	More than one possible loop control variable.

(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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