两个struct的动态内存分配，struct A有一个指向struct B的指针

Question

I have two structs A and B. Struct B has pointer in it of the type struct A. Both structs/instances should allocate memory on runtime. The are linear dependent. I posted code which should present my idea, which doesn´t work. Please show me the right way.

#include <stdio.h>
#include <string.h>
#include <stdlib.h> //EXIT_SUCCESS, calloc

struct A
{
 char *name;
 int id;
};

struct B
{
 char *buildingName;
 struct a *ptra;
};


int main()
{

   int employe = 1;
   int NrOfBuildinTemplates = 3;

   struct A *humans;
   struct B *buildings; 

   humans =  calloc(employe, sizeof(struct A));
   buildings = calloc(NrOfBuildinTemplates, sizeof(struct B));

   buildings[0].buildingName = strdup("Building A");
   buildings[1].buildingName = strdup("Building B");
   buildings[2].buildingName = strdup("Building C");


   int count = 100, n = 0;
   for (size_t i = 3; i < count; i++)
   {
      buildings = realloc (buildings, sizeof(struct B) * (i+1));
      buildings[i].buildingName = strdup("Building XYZ");
      buildings[i].ptra = &(humans[n]);
      buildings[i].ptra->name = strdup("NameXYZ"); 
      humans = realloc(humans, sizeof(struct A) * (n+1));
      n++;
   }


   for (size_t i = 3; i < count; i++)
   {
      printf("%s -> %s\n", buildings[i].buildingName, buildings[i].ptra->name);
      n++;
   }
 return 0;
}

Answer 1

  buildings = realloc(buildings, i+1);

This is wrong. It should be:

  buildings = realloc(buildings, sizeof(struct B) * (i+1));

There's a similar issue with this:

  humans = realloc(humans, n+1);

Also, this code is completely baffling. I can't suggest how to fix it because I have no idea what you think it does:

  buildings[i].ptra = (*buildings->ptra) calloc(1, buildings->ptra);
  buildings[i].ptra = &(humans[n]);
  buildings[i].ptra = strdup("NameXYZ");