text: #include <stdlib.h>
  #include <stdio.h>
  #include "uthash.h"
  
  typedef struct hs_t {
      int id;
      int tag;
      UT_hash_handle hh;
  } hs_t;
  
  
  static void pr(hs_t **hdpp)
  {
      hs_t *el, *tmp, *hdp = *hdpp;
      HASH_ITER(hh, hdp, el, tmp) {
          printf("id %d, tag %d\n",el->id,el->tag);
      }
  }
  
  int main()
  {
  
      hs_t *hs_head=NULL, *tmp, *replaced=NULL;
  
      tmp = (hs_t*)malloc(sizeof(hs_t));
      if (tmp == NULL) {
          exit(-1);
      }
      tmp->id = 10;
      tmp->tag = 100;
      HASH_REPLACE_INT(hs_head,id,tmp,replaced);
      if(replaced == NULL) {
          printf("added %d %d\n",tmp->id,tmp->tag);
      } else {
          printf("ERROR, ended up replacing a value, replaced: %p\n",(void*)replaced);
      }
  
      pr(&hs_head);
  
      tmp = (hs_t*)malloc(sizeof(hs_t));
      if (tmp == NULL) {
          exit(-1);
      }
      tmp->id=11;
      tmp->tag = 101;
      HASH_REPLACE_INT(hs_head,id,tmp,replaced);
      if(replaced == NULL) {
          printf("added %d %d\n",tmp->id,tmp->tag);
      } else {
          printf("ERROR, ended up replacing a value, replaced: %p\n",(void*)replaced);
      }
  
      pr(&hs_head);
  
      tmp = (hs_t*)malloc(sizeof(hs_t));
      if (tmp == NULL) {
          exit(-1);
      }
      tmp->id=11;
      tmp->tag = 102;
      HASH_REPLACE_INT(hs_head,id,tmp,replaced);
      if(replaced == NULL) {
          printf("ERROR, exected to replace a value with key: %d\n",tmp->id);
      } else {
          printf("replaced %d that had tag %d with tag %d\n",tmp->id,replaced->tag,tmp->tag);
      }
  
      pr(&hs_head);
  
      return 0;
  }
  