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

Answer 1

What exactly are you trying to do? p_my_t is already a pointer, but you haven't allocated memory for it. If you want to set the pointer to NULL, simply do

p_my_t = NULL;

Trying to dereference this pointer will result in a segmentation fault (or access violation on Windows).

Once the pointer actually pointers to something (e.g. via malloc() or by assigning to it the address of a struct my_T), then you can properly memset() it:

memset(p_my_t, 0, sizeof(struct my_T));

This will zero out the entire structure, setting all fields to zero.