Hands-On: MISRA-Compliant Module

/* Original code with MISRA violations — identify and fix all of them */
#include "can_buffer.h"

int g_buffer_count = 0;          /* Violation 1: plain int (Rule 6.1 area + 8.5) */
unsigned char g_buffer[100];     /* Violation 2: unsigned char not uint8_t */

int can_buffer_push(unsigned char *data, int len)  /* Violation 3,4: plain int */
{
    if (len > 100)               /* Violation 5: 100 not typed as 100u */
        return -1;               /* Violation 6: missing braces (Rule 15.6) */

    for (int i = 0; i < len; i++) {            /* Violation 7: plain int loop var */
        g_buffer[g_buffer_count + i] = data[i]; /* Violation 8: no bounds check */
    }
    g_buffer_count += len;       /* Violation 9: signed/unsigned arithmetic */
    return 0;
}
/* Violation 10: no function documentation; Dir 4.3 advisory */
/* FIXED VERSION: implement below using MISRA-compliant types and patterns */

/* MISRA Deviation Record: CAN Buffer Module */
/* Module: can_buffer.c  Version: 1.0  Author: Engineer Name  Date: 2024-01-15 */

/* -----------------------------------------------------------------------
   Deviation ID:    DEV-CAN-001
   Rule:            MISRA-C:2012 Rule 11.5 (Advisory)
   Location:        can_buffer.c line 42
   Code:            void *pool = MemPool_Alloc(sizeof(CanFrame_t));
                    CanFrame_t *frame = (CanFrame_t *)pool;
   Justification:   MemPool_Alloc() returns void* by design to provide a
                    type-agnostic memory pool interface. The allocated block
                    is always sizeof(CanFrame_t) bytes, ensuring correct
                    alignment for CanFrame_t. This cast is safe and intentional.
   Risk assessment: Low — size and alignment are correct by design; pool is
                    not externally accessible; no type confusion possible.
   Alternative:     A CanFrame_t-specific allocator would duplicate pool code
                    for each type; rejected on code size grounds.
   Approved by:     Jane Smith (SW Safety Manager), 2024-01-15
   Reviewer:        Bob Jones (MISRA Lead), 2024-01-15
   Tool annotation: //lint -e9079 [DEV-CAN-001]
   ----------------------------------------------------------------------- */

/*lint -e9079 [DEV-CAN-001: void* to CanFrame_t* — see deviation record] */
void *pool = MemPool_Alloc(sizeof(CanFrame_t));
CanFrame_t *frame = (CanFrame_t *)pool;
/*lint +e9079 */

#!/bin/bash
# CI script: run Cppcheck MISRA check; fail if too many violations

SOURCE_DIR="src/"
ADDONS_DIR="/opt/cppcheck/addons"
MISRA_CFG="misra_c_2012.json"

# Run Cppcheck with MISRA addon
cppcheck --addon="$ADDONS_DIR/misra.py"          --addon-python=python3          --enable=all          --inconclusive          --template="{file}:{line}: {severity}: {message} [{id}]"          "$SOURCE_DIR" 2> misra_results.txt

# Count violation categories
MANDATORY=$(grep -c "mandatory" misra_results.txt 2>/dev/null || echo 0)
REQUIRED=$(grep  -c "required"  misra_results.txt 2>/dev/null || echo 0)

echo "MISRA Mandatory violations: $MANDATORY (must be 0)"
echo "MISRA Required violations:  $REQUIRED  (threshold: 10)"

if [ "$MANDATORY" -gt "0" ]; then
    echo "FAIL: Mandatory violations must be fixed"
    exit 1
fi
if [ "$REQUIRED" -gt "10" ]; then
    echo "FAIL: Required violations exceed threshold"
    exit 1
fi
echo "PASS: MISRA check within limits"