QA·C Help - 0317

	0317	[I] Implicit conversion from a pointer to void to a pointer to object type.

Pointers		REFERENCE - ISO:C90-6.3.4 Cast Operators - Semantics

An expression of type 'pointer-to-void' is being implicitly converted to a 'pointer-to-object' type.

'void pointers' should be used with care. A conversion of this kind can only be performed safely if the pointer is correctly aligned for the type of object being pointed to.

Notice that the 'void pointers' returned by library functions malloc, calloc and realloc are guaranteed to be suitably aligned so that they may address an object of any type. Message 0317 is not generated when the value returned by these functions is implicitly converted to a 'pointer-to-object' type.

For example:


/*PRQA S 702,1278,2017,2211,3120,3198,3199,3203,3227,3408,3602 ++*/

#include <stdlib.h>

extern void foo(unsigned char * puc)
{
    void * pvd;
    unsigned int * pui; 
    
    pui = (unsigned int *) puc;                     /* Messages 0310 and 3305 - dangerous */

    pvd = (void *) puc;                             /* Message  0314                      */
    pvd =          puc;                             /* Message  0315                      */

    pui = (unsigned int *) pvd;                     /* Message  0316 - dangerous          */
    pui =                  pvd;                     /* Message  0317 - dangerous          */

    pui = malloc(10u * sizeof(unsigned int));       /*                                    */
    pui = realloc(pui, 20u * sizeof(unsigned int)); /* Message  0315                      */
    free(pui);                                      /* Message  0315                      */
    pui = calloc(10u, sizeof(unsigned int));        /*                                    */
    free(pui);                                      /* Message  0315                      */
}