This code fills a tree with values based their depths. But when traversing the tree, I cannot manage to determine the actual number of children. node->cnt is always 0. I've already tried node->parent->cnt but that gives me lots of warnings in Valgrind.

Anyway, is the tree type I've chosen even appropriate for my purpose?

#include <string.h>
#include <stdio.h>
#include <stdlib.h>

#ifndef NULL
#define NULL ((void *) 0)
#endif

// ----

typedef struct _Tree_Node {
 // data ptr
 void *p;

 // number of nodes
 int cnt;
 struct _Tree_Node *nodes;

 // parent nodes
 struct _Tree_Node *parent;
} Tree_Node;

typedef struct {
 Tree_Node root;
} Tree;

void Tree_Init(Tree *this) {
 this->root.p = NULL;
 this->root.cnt = 0;
 this->root.nodes = NULL;
 this->root.parent = NULL;
}

Tree_Node* Tree_AddNode(Tree_Node *node) {
 if (node->cnt == 0) {
  node->nodes = malloc(sizeof(Tree_Node));
 } else {
  node->nodes = realloc(
   node->nodes,
   (node->cnt + 1) * sizeof(Tree_Node)
  );
 }

 Tree_Node *res = &node->nodes[node->cnt];

 res->p = NULL;
 res->cnt = 0;
 res->nodes = NULL;
 res->parent = node;

 node->cnt++;

 return res;
}

// ----

void handleNode(Tree_Node *node, int depth) {
 int j = depth;

 printf("\n");

 while (j--) {
  printf("    ");
 }

 printf("depth=%d ", depth);

 if (node->p == NULL) {
  goto out;
 }

 printf("value=%s cnt=%d", node->p, node->cnt);

out:
 for (int i = 0; i < node->cnt; i++) {
  handleNode(&node->nodes[i], depth + 1);
 }
}

Tree tree;

int curdepth;
Tree_Node *curnode;

void add(int depth, char *s) {
 printf("%s: depth (%d) > curdepth (%d): %d\n", s, depth, curdepth, depth > curdepth);

 if (depth > curdepth) {
  curnode = Tree_AddNode(curnode);

  Tree_Node *node = Tree_AddNode(curnode);

  node->p = malloc(strlen(s));
  memcpy(node->p, s, strlen(s));

  curdepth++;
 } else {
  while (curdepth - depth > 0) {
   if (curnode->parent == NULL) {
    printf("Illegal nesting\n");
    return;
   }

   curnode = curnode->parent;
   curdepth--;
  }

  Tree_Node *node = Tree_AddNode(curnode);

  node->p = malloc(strlen(s));
  memcpy(node->p, s, strlen(s));
 }
}

void main(void) {
 Tree_Init(&tree);

 curnode = &tree.root;
 curdepth = 0;

 add(0, "1");
 add(1, "1.1");
 add(2, "1.1.1");
 add(3, "1.1.1.1");
 add(4, "1.1.1.1.1");
 add(2, "1.1.2");
 add(0, "2");

 handleNode(&tree.root, 0);
}