While reading an answer here, I saw this code:

```
char ** v = malloc(0);
while ((r = strtok(s, " ")) != NULL) {
    char ** vv = realloc(v, (n+1)*sizeof(*vv));

```

The thing that bugged me was the call to malloc with an argument of zero. According to the standard, this will return either NULL or a non-NULL pointer that can be successfully passed to free. I know that this does not invoke any problems (except for if you do stuff like `if (v == NULL)` or similar) but is there any practical reason whatsoever to prefer `malloc(0)` instead of `NULL`?

I saw the argument "to indicate the goal of that pointer is to be given to `realloc` later". To me that sounds like a pretty strange argument. I cannot see the value of that convention at all. First because it's an extra function call that's not needed. And second because the value of telling that you will use realloc later seems almost zero. And according to the answers on [this question](https://stackoverflow.com/q/2022335/6699433) it does not seem to be any *technical* benefits whatsoever.

Personally, if I ever felt the need to tell that `realloc` would be used later I'd do this:

```
char **v = NULL; // Will be realloced later

```

or give it a name that makes that intention clear. I would not use a strange unmotivated function call. But IMHO, just initializing it to NULL is a very clear indication that SOMETHING will be done to it later on. I don't see the value of knowing in advance that it's `realloc`. What's next? A convention saying that `malloc(0*0)` indicates that `strdup` will be used later?

So to sum it up, these are the cons that I know of:

* An extra unnecessary function call
* Looks weird if you don't know that it indicates later realloc (and still looks weird to me anyway)
* May return a valid pointer that should not be dereferenced (just strange)
* May allocate memory that you cannot use (quite pointless)
* Less predictable. You may get NULL. You may get something else.

Pros:

* ?

The only sensible explanation I can think of that this habit may come from is that it is something from very early C, before `NULL` became a part of `stddef.h` and calling `malloc(0)` was the only portable way to get a pointer that was guaranteed to be safe to be passed to `free` without allocating anything. Could that be the case?

So is this really an accepted convention for indicating a later realloc? If so, is it a good convention? Does it have any benefits that I fail to see?

There is a related question on SO: [What's the point of malloc(0)?](https://stackoverflow.com/q/2022335/6699433)

### Clarification:

I'm not talking about `malloc(n)` where `n` happens to be zero in some cases. I'm talking about calling `malloc(0)` on purpose.