how to set pointer to a memory to NULL using memset?

Question

I have a structure ``` typedef struct my_s { int x; ... } my_T; my_t * p_my_t; ``` I want to set the address of `p_my_t` to `NULL` and so far this is how I've tried to do this: ``` memset (&p_my_t, 0, sizeof(my_t*)) ``` This doesn't not look right to me though. What is the correct way of doing this? Amendment to question - asking a radically more complex question: Here is what I am trying to do: - Two processes, A and B - malloc p_my_t in A, B has N threads and can access it - Start deleting in A but I can not simply free it since threads in B may still using it. - So I call a function, pass address of p_my_t to B to set its address to NULL in B so no other threads in B can use anymore - After call back from B, I then free memory in A NB: there is no standard way to manage memory allocations via shared memory between processes. You will have to do some rather careful thinking about what is going on.

Accepted Answer

Don't use `memset` to initialize a null pointer as this will set the memory to all bits zero which is not guaranteed to be the representation of a null pointer, just do this:

```
p_my_t = NULL;
```

or the equivalent:

```
p_my_t = 0;
```

how to set pointer to a memory to NULL using memset?

Solution

Problem