Something

char *tmp_availchan = NULL, *tmp_availorig = NULL, *tmp_availstatus = NULL;

                                        if (tmp_availchan)
                                        {
                                                strcat(tmp_availchan, "&");
                                                strcat(tmp_availorig, "&");
                                                strcat(tmp_availstatus, "&");
                                        }
                                        //tmp_availchan = (char*) realloc (tmp_availchan, 512 * sizeof(char));
                                        tmp_availchan = ast_realloc(tmp_availchan, 512 * sizeof(char));
                                        strcat(tmp_availchan, tempchan->name);

                                        snprintf(tmp, sizeof(tmp), "%s/%s", tech, number);
                                        tmp_availorig = ast_realloc(tmp_availorig, 512 * sizeof(char));
                                        strcat(tmp_availorig, tmp);

                                        snprintf(tmp, sizeof(tmp), "%d", status);
                                        tmp_availstatus = ast_realloc(tmp_availstatus, 512 * sizeof(char));
                                        strcat(tmp_availstatus, tmp);

                                        //ast_hangup(tempchan);
                                        tempchan = NULL;
                                        res += 1;

                                        if (!option_all_avail)
                                                break;