Thread: typecasting?

Sheesh I'm just full of questions.

I got a question about typecasting in one particular instance. I know that normally you'd typecast like this:

(type)command

Right? Well, they use a malloc command with a * next to the typecast, like this:

struct list {
int x;
struct *next;
};

struct list *root;
struct list *pointer;
struct list *new;

new = (list*) malloc (sizeof (struct list));

Can anyone tell me what the * is next to the typecast for? Would the malloc command have worked even without a typecast?

>> Can anyone tell me what the * is next to the typecast for?

malloc() returns the address of the allocated memory (a pointer to the memory), so it is casted to the appropriate pointer type.

>> Would the malloc command have worked even without a typecast?

In C programming the malloc would've worked. In C you don't need to cast malloc().

If malloc only returns one type of data, can you think of any reason why the writer of that program would typecast malloc?

It has to do with making your program type-safe. IOW, making sure that someting gets casted to the correct type and not relying on the compiler.

>> can you think of any reason why the writer of that program would typecast malloc?

It probably increases code readability. Other than that, it's just a style of programming IMO.

But malloc doesn't return void does it? I guess I can live with it just being the writer's own style, but I still don't understand what the * was doing next to the cast. Why not just go like this:

(list)malloc(sizeof(struct list));

?

I don't get what the dillyoh is with the *. If you're typecasting a pointer, wouldn't you put it like this:

(*list)



???

>> If you're typecasting a pointer, wouldn't you put it like this: (*list)

No, whenever pointers are involved, the statement/expression/declaration/whatever is always read from right to left.

Here are a few examples of how the code is read.

Code:

int *i_ptr;            //i_ptr is a pointer to an int
float *f_ptr;         //f_ptr is a pointer to a float
char **c_pptr;     //c_pptr is a pointer to a pointer to a char 
void *function();  //function returns a pointer to void

So, to cast malloc(), the indirection operator, *, is placed after the type. So in this case :
(list*)malloc(sizeof(struct list));

malloc() would be casted to a pointer to list.