MISRA.CAST.VOID_PTR_TO_OBJ_PTR.2012

Conversion performed from a pointer to void to a pointer to an object.

MISRA C 2012 Rule 11.5: A conversion should not be performed from pointer to void into pointer to object

C90 [Undefined 20], C99 [Undefined 22, 34]

Category: Advisory

Analysis: Decidable, Single Translation Unit

Applies to: C90, C99

Rationale

Conversion of a pointer to void into a pointer to object may result in a pointer that is not correctly aligned, resulting in undefined behaviour. It should be avoided where possible but may be necessary, for example when dealing with memory allocation functions. If conversion from a pointer to object into a pointer to void is used, care should be taken to ensure that any pointers produced do not give rise to the undefined behaviour discussed under Rule 11.3.

Exception

A null pointer constant that has type pointer to void may be converted into pointer to object.

Example

uint32_t *p32;
void     *p;
uint16_t *p16;

p   = p32;                /* Compliant - pointer to uint32_t into
                           * pointer to void                       */
p16 = p;                  /* Non-compliant                         */
p   = ( void * ) p16;     /* Compliant                             */
p32 = ( uint32_t * ) p;   /* Non-compliant                         */