Make this construct legal behavior without making it 10x slower than clang/gcc are today: void wat(uint16_t *x, uint16_t *y) { *x = *y; } uint64_t a

Make this construct legal behavior without making it 10x slower than clang/gcc are today: void wat(uint16_t *x, uint16_t *y) { *x = *y; } uint64_t a[100] = { 0 }; wat((uint16_t *)&a[0], (uint16_t *)(((char *)&a[0]) + 1)); When you think you've figured that one out, try this one: uint16_t heh = 0xFFFF; extern uint16_t doesAnything(uint16_t *, uint16_t *); void wat(uint16_t *x, uint16_t *y) { *x = *y + doesAnything(&heh, y); } uint64_t a[2] = { 0 }; wat((uint16_t *)&a[0], (uint16_t *)(((char *)&a[0]) + 1));