Common MISRA Violations & Fixes

#include 

/* Rule 10.1: Operands shall not be of an inappropriate essential type
   Violation: shifting a signed integer */
int16_t x = 10;
int16_t y = x << 3;   /* VIOLATION: shift of signed type */
/* Fix: */
uint16_t xu = (uint16_t)x;
uint16_t y2 = (uint16_t)(xu << 3u);  /* explicit cast + unsigned shift */

/* Rule 10.3: Value cannot be assigned to narrower essential type
   Violation: assigning uint16 result to uint8 */
uint16_t adc = 1234u;
uint8_t  trunc = adc;  /* VIOLATION: implicit narrowing conversion */
/* Fix: explicit cast with range check */
uint8_t scaled = (uint8_t)(adc >> 4u);  /* explicit: knows upper bits are 0 */

/* Rule 10.4: Both operands of operator in the same essential type category
   Violation: mixing signed/unsigned */
uint32_t len  = 100u;
int32_t  diff = -5;
if (diff < len) { /* VIOLATION: signed/unsigned comparison */ }
/* Fix: */
if ((uint32_t)diff < len) { /* explicit cast; ensure diff >= 0 first */ }

/* Rule 10.8: Value of a composite expression shall not be cast to wider type
   Violation: */
uint8_t a = 200u, b = 100u;
uint32_t bad  = (uint32_t)(a + b);    /* overflow in uint8 before cast! */
uint32_t good = (uint32_t)a + (uint32_t)b;  /* cast before arithmetic */

/* MISRA-C:2012 Deviation Record Example */

/* Rule:    MISRA-C:2012 Rule 11.5 (Advisory)
   Message: A conversion should not be performed from pointer to void
            into pointer to object
   Code:    void *raw = malloc_pool_alloc(64u);
            uint8_t *buf = (uint8_t *)raw;
   Reason:  Memory pool returns void* by design; cast to uint8_t* is required.
            The allocated memory is always correctly aligned for uint8_t.
            This is a deliberate design choice, not an unsafe practice.
   Risk:    Low — alignment guaranteed by pool allocator; usage is bounded.
   Approved: John Smith (SW Lead), 2024-03-15
   Tools:   PC-lint annotation: //lint -e9079 Deviation MISRA_11_5_001           */

/*lint -e9079 [Deviation MISRA_11_5_001: See deviation record DV-MISRA-001] */
void *raw = Pool_Alloc(sizeof(uint8_t) * 64u);
uint8_t *buf = (uint8_t *)raw;
/*lint +e9079 */