c++ - Cast a void pointer to a struct or memcpy to new struct?

I am passing a void * as an
argument to a function foo(void* parm) which calls function
bar(STmyStruct* parm)
Should I cast the void pointer
to STmyStruct* or create a new struct, memcpy what the
void* points to and then pass a pointer to that
struct?

I guess solution A is more
efficient?

A: foo(void*
            parm)
 {
 bar((STmyStruct*) parm)

            }

B: foo(void* parm)
 {
 STmyStruct
            myStr;

 memcpy(&myStr, parm, sizeof(STmyStruct));

            bar(&myStr)
 }


bar(STmyStruct*
            mystr);