Defining an array of structures in C?

Question

main.h

#define  DATA  struct   data
DATA
{
  int id;
  char data;
}

main.c

DATA *listOfData[100];

So at this

Answer 1

This is because you have defined an array of pointers. But you never initialized any of the pointers.

Therefore:

printf(listOfData[5]->data);

will crash (undefined behavior) because you are dereferencing the (invalid) pointer at index 5.

*(And that's a very odd way to define a struct...)

To fix this issue, you will need to allocate for each of the pointers in the array. If you don't actually need it to be an array of pointers, then it might be better to just make it array of the struct itself:

DATA listOfData[100];

and access it as:

listOfData[5].data

Then you don't have to deal with allocating each element.