Realloc is not resizing array of pointers

Question

I keep passing in and returning the dirs_later_array. When I get to \"new_size=...\" in the else block, I end up with new_size of 2 the second time around. So far so good.

Answer 1

Your sizeof(struct dirs_later*) should be changed to sizeof(struct dirs_later) - as before!

Also the sizeof is a compile time feature. You need a structure like this to hold the size

struct my_dirs
   struct dirs_later *dirs;
   int size;
};

Initialise it like this

struct my_dirs directories;
directories.size = 0;
directories.dirs = NULL;

Then to add (note realloc can take NULL as a parameter

directories.dirs = realloc(directories.dirs,
                           (++directories.size) * sizeof(struct dirs_later));

This would also simplify your code.

Answer 2

Operator sizeof is a compile time feature and it only checks the static size of an expression. So for pointer it only returns the size of that pointer which is 4 on your platform. sizeof does not measure the size of a dynamically allocated data. There is no standard feature in C to get the size of dynamically allocated data.