Pointer in the definition of a function

Question

I am learning c, however i understand the concept of pointers but here i am having trouble.What is mean by a pointer in the definition of a function. Here v is a local pointer defined within the function so returning it means that only the values will be copied and returned or a pointer to that block will be returned because what i also learnt that local variables have only life time until the function executes. Will someone like to explain, will be a great help.

struct verpl * nieuw (int van, int naar, int aantal, register struct verplaatsing * lijst)
{
   register struct verpl * v = (struct verpl *) alloc(sizeof(struct verpl));
   aNieuw++;
   v->van = van;
   v->naar = naar;
   v->aantal = aantal;
    v->volg = lijst; // plaats het element vooraan in de lijst
     return (v);
}

Function call

 lijst = nieuw (via, huidig->naar, huidig->aantal - 1, lijst);

First of all: remove the`register` s; they can only do harm.(second: remove the cast) — wildplasser, Aug 19 '17 at 13:32
I don't see why you are passing `lijst` as an argument for the function parameter `struct verplaatsing *` but then assigning the function return value to it, which is type `struct verpl *`. They are different types. — Weather Vane, Aug 19 '17 at 13:36
pls divide so long sentence, hard to understand is correctly — Jacek Cz, Aug 19 '17 at 13:36
@WeatherVane there are 3 recursive calls and lijst is self a pointer. — Afraz Salim, Aug 19 '17 at 13:43
I see no recursive call, and that doesn't explain why you use the same variable for two different types. — Weather Vane, Aug 19 '17 at 13:46

score 0 · Accepted Answer · answered Aug 19 '17 at 13:33

0

What is returned is the pointer value returned from alloc().

v is local and returning a pointer pointing to v is not good, but what v is pointing is not local, so returning it is valid.

answered Aug 19 '17 at 13:33

MikeCAT

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`alloc()` ? isn't that `malloc` ? if it's `alloca` then there's a problem. – Jean-François Fabre Aug 19 '17 at 13:35
@Jean-FrançoisFabre `alloc()` exists as non-standard library. [c - alloc, malloc, and alloca — What's the difference? - Stack Overflow](https://stackoverflow.com/questions/32685851/alloc-malloc-and-alloca-whats-the-difference) I don't know if it is typo of `malloc` or `alloca`. – MikeCAT Aug 19 '17 at 13:37
if it's a typo of `alloca` then the code is wrong as it returns a reference on temporary memory. – Jean-François Fabre Aug 19 '17 at 13:40

Pointer in the definition of a function

1 Answers1