How to get the length of a dynamically created array of structs in C?

Question

I am currently trying to get the length of a dynamically generated array. It is an array of structs:

typedef struct _my_data_ 
{
  unsigned int id;
  double          


        

Answer 1

You're trying to use a pretty well known trick to find the number of elements in an array. Unfortunately arr in your example is not an array, it's a pointer. So what you're getting in your sizeof division is:

sizeof(pointer) / sizeof(structure)

Which is probably always going to be 0.