path: root/sql/wsrep_var.cc

/* Copyright 2008-2015 Codership Oy <http://www.codership.com>

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111-1301 USA */

#include "wsrep_var.h"

#include <mysqld.h>
#include <sql_class.h>
#include <set_var.h>
#include <sql_acl.h>
#include "wsrep_priv.h"
#include "wsrep_thd.h"
#include "wsrep_xid.h"
#include <my_dir.h>
#include <cstdio>
#include <cstdlib>

ulong   wsrep_reject_queries;

static long wsrep_prev_slave_threads = wsrep_slave_threads;

int wsrep_init_vars()
{
  wsrep_provider        = my_strdup(WSREP_NONE, MYF(MY_WME));
  wsrep_provider_options= my_strdup("", MYF(MY_WME));
  wsrep_cluster_address = my_strdup("", MYF(MY_WME));
  wsrep_cluster_name    = my_strdup(WSREP_CLUSTER_NAME, MYF(MY_WME));
  wsrep_node_name       = my_strdup("", MYF(MY_WME));
  wsrep_node_address    = my_strdup("", MYF(MY_WME));
  wsrep_node_incoming_address= my_strdup(WSREP_NODE_INCOMING_AUTO, MYF(MY_WME));
  wsrep_start_position  = my_strdup(WSREP_START_POSITION_ZERO, MYF(MY_WME));
  return 0;
}

/* This is intentionally declared as a weak global symbol, so that
linking will succeed even if the server is built with a dynamically
linked InnoDB. */
ulong innodb_lock_schedule_algorithm __attribute__((weak));
struct handlerton* innodb_hton_ptr __attribute__((weak));

bool wsrep_on_update (sys_var *self, THD* thd, enum_var_type var_type)
{
  if (var_type == OPT_GLOBAL) {
    // FIXME: this variable probably should be changed only per session
    thd->variables.wsrep_on = global_system_variables.wsrep_on;
  }

  return false;
}

bool wsrep_on_check(sys_var *self, THD* thd, set_var* var)
{
  bool new_wsrep_on= (bool)var->save_result.ulonglong_value;

  if (check_has_super(self, thd, var))
    return true;

  if (new_wsrep_on && innodb_hton_ptr && innodb_lock_schedule_algorithm != 0) {
    my_message(ER_WRONG_ARGUMENTS, " WSREP (galera) can't be enabled "
	    "if innodb_lock_schedule_algorithm=VATS. Please configure"
	    " innodb_lock_schedule_algorithm=FCFS and restart.", MYF(0));
    return true;
  }
  return false;
}

bool wsrep_causal_reads_update (sys_var *self, THD* thd, enum_var_type var_type)
{
  // global setting should not affect session setting.
  // if (var_type == OPT_GLOBAL) {
  //   thd->variables.wsrep_causal_reads = global_system_variables.wsrep_causal_reads;
  // }
  if (thd->variables.wsrep_causal_reads) {
    thd->variables.wsrep_sync_wait |= WSREP_SYNC_WAIT_BEFORE_READ;
  } else {
    thd->variables.wsrep_sync_wait &= ~WSREP_SYNC_WAIT_BEFORE_READ;
  }

  // update global settings too.
  if (global_system_variables.wsrep_causal_reads) {
      global_system_variables.wsrep_sync_wait |= WSREP_SYNC_WAIT_BEFORE_READ;
  } else {
      global_system_variables.wsrep_sync_wait &= ~WSREP_SYNC_WAIT_BEFORE_READ;
  }

  return false;
}

bool wsrep_sync_wait_update (sys_var* self, THD* thd, enum_var_type var_type)
{
  // global setting should not affect session setting.
  // if (var_type == OPT_GLOBAL) {
  //   thd->variables.wsrep_sync_wait = global_system_variables.wsrep_sync_wait;
  // }
  thd->variables.wsrep_causal_reads = thd->variables.wsrep_sync_wait &
          WSREP_SYNC_WAIT_BEFORE_READ;

  // update global settings too
  global_system_variables.wsrep_causal_reads = global_system_variables.wsrep_sync_wait &
          WSREP_SYNC_WAIT_BEFORE_READ;

  return false;
}


/*
  Verify the format of the given UUID:seqno.

  @return
    true                    Fail
    false                   Pass
*/
static
bool wsrep_start_position_verify (const char* start_str)
{
  size_t        start_len;
  wsrep_uuid_t  uuid;
  ssize_t       uuid_len;

  // Check whether it has minimum acceptable length.
  start_len = strlen (start_str);
  if (start_len < 34)
    return true;

  /*
    Parse the input to check whether UUID length is acceptable
    and seqno has been provided.
  */
  uuid_len = wsrep_uuid_scan (start_str, start_len, &uuid);
  if (uuid_len < 0 || (start_len - uuid_len) < 2)
    return true;

  // Separator must follow the UUID.
  if (start_str[uuid_len] != ':')
    return true;

  char* endptr;
  wsrep_seqno_t const seqno __attribute__((unused)) // to avoid GCC warnings
    (strtoll(&start_str[uuid_len + 1], &endptr, 10));

  // Remaining string was seqno.
  if (*endptr == '\0') return false;

  return true;
}


static
bool wsrep_set_local_position(const char* const value, size_t length,
                              bool const sst)
{
  wsrep_uuid_t uuid;
  size_t const uuid_len = wsrep_uuid_scan(value, length, &uuid);
  wsrep_seqno_t const seqno = strtoll(value + uuid_len + 1, NULL, 10);

  if (sst) {
    return wsrep_sst_received (wsrep, uuid, seqno, NULL, 0, false);
  } else {
    // initialization
    local_uuid = uuid;
    local_seqno = seqno;
  }
  return false;
}


bool wsrep_start_position_check (sys_var *self, THD* thd, set_var* var)
{
  char start_pos_buf[FN_REFLEN];

  if ((! var->save_result.string_value.str) ||
      (var->save_result.string_value.length > (FN_REFLEN - 1))) // safety
    goto err;

  memcpy(start_pos_buf, var->save_result.string_value.str,
         var->save_result.string_value.length);
  start_pos_buf[var->save_result.string_value.length]= 0;

  // Verify the format.
  if (wsrep_start_position_verify(start_pos_buf)) return true;

  /*
    As part of further verification, we try to update the value and catch
    errors (if any).
  */
  if (wsrep_set_local_position(var->save_result.string_value.str,
                               var->save_result.string_value.length,
                               true))
  {
    goto err;
  }

  return false;

err:
  my_error(ER_WRONG_VALUE_FOR_VAR, MYF(0), var->var->name.str,
           var->save_result.string_value.str ?
           var->save_result.string_value.str : "NULL");
  return true;
}

bool wsrep_start_position_update (sys_var *self, THD* thd, enum_var_type type)
{
  // Print a confirmation that wsrep_start_position has been updated.
  WSREP_INFO ("wsrep_start_position set to '%s'", wsrep_start_position);
  return false;
}

bool wsrep_start_position_init (const char* val)
{
  if (NULL == val || wsrep_start_position_verify (val))
  {
    WSREP_ERROR("Bad initial value for wsrep_start_position: %s", 
                (val ? val : ""));
    return true;
  }

  if (wsrep_set_local_position (val, strlen(val), false))
  {
    WSREP_ERROR("Failed to set initial wsep_start_position: %s", val);
    return true;
  }

  return false;
}

static int get_provider_option_value(const char* opts,
                                     const char* opt_name,
                                     ulong* opt_value)
{
  int ret= 1;
  ulong opt_value_tmp;
  char *opt_value_str, *s, *opts_copy= my_strdup(opts, MYF(MY_WME));

  if ((opt_value_str= strstr(opts_copy, opt_name)) == NULL)
    goto end;
  opt_value_str= strtok_r(opt_value_str, "=", &s);
  if (opt_value_str == NULL) goto end;
  opt_value_str= strtok_r(NULL, ";", &s);
  if (opt_value_str == NULL) goto end;

  opt_value_tmp= strtoul(opt_value_str, NULL, 10);
  if (errno == ERANGE) goto end;

  *opt_value= opt_value_tmp;
  ret= 0;

end:
  my_free(opts_copy);
  return ret;
}

static bool refresh_provider_options()
{
  DBUG_ASSERT(wsrep);

  WSREP_DEBUG("refresh_provider_options: %s", 
              (wsrep_provider_options) ? wsrep_provider_options : "null");
  char* opts= wsrep->options_get(wsrep);
  if (opts)
  {
    wsrep_provider_options_init(opts);
    get_provider_option_value(wsrep_provider_options,
                              (char*)"repl.max_ws_size",
                              &wsrep_max_ws_size);
    free(opts);
  }
  else
  {
    WSREP_ERROR("Failed to get provider options");
    return true;
  }
  return false;
}

static int wsrep_provider_verify (const char* provider_str)
{
  MY_STAT   f_stat;
  char path[FN_REFLEN];

  if (!provider_str || strlen(provider_str)== 0)
    return 1;

  if (!strcmp(provider_str, WSREP_NONE))
    return 0;

  if (!unpack_filename(path, provider_str))
    return 1;

  /* check that provider file exists */
  memset(&f_stat, 0, sizeof(MY_STAT));
  if (!my_stat(path, &f_stat, MYF(0)))
  {
    return 1;
  }
  return 0;
}

bool wsrep_provider_check (sys_var *self, THD* thd, set_var* var)
{
  char wsrep_provider_buf[FN_REFLEN];

  if ((! var->save_result.string_value.str) ||
      (var->save_result.string_value.length > (FN_REFLEN - 1))) // safety
    goto err;

  memcpy(wsrep_provider_buf, var->save_result.string_value.str,
         var->save_result.string_value.length);
  wsrep_provider_buf[var->save_result.string_value.length]= 0;

  if (!wsrep_provider_verify(wsrep_provider_buf)) return 0;

err:
  my_error(ER_WRONG_VALUE_FOR_VAR, MYF(0), var->var->name.str,
           var->save_result.string_value.str ?
           var->save_result.string_value.str : "NULL");
  return 1;
}

bool wsrep_provider_update (sys_var *self, THD* thd, enum_var_type type)
{
  bool rcode= false;

  bool wsrep_on_saved= thd->variables.wsrep_on;
  thd->variables.wsrep_on= false;

  WSREP_DEBUG("wsrep_provider_update: %s", wsrep_provider);

  /* stop replication is heavy operation, and includes closing all client 
     connections. Closing clients may need to get LOCK_global_system_variables
     at least in MariaDB.

     Note: releasing LOCK_global_system_variables may cause race condition, if 
     there can be several concurrent clients changing wsrep_provider
  */
  mysql_mutex_unlock(&LOCK_global_system_variables);
  wsrep_stop_replication(thd);
  mysql_mutex_lock(&LOCK_global_system_variables);

  if (wsrep_inited == 1)
    wsrep_deinit(false);

  char* tmp= strdup(wsrep_provider); // wsrep_init() rewrites provider
                                     //when fails

  if (wsrep_init())
  {
    my_error(ER_CANT_OPEN_LIBRARY, MYF(0), tmp, my_error, "wsrep_init failed");
    rcode = true;
  }
  free(tmp);

  // we sure don't want to use old address with new provider
  wsrep_cluster_address_init(NULL);
  wsrep_provider_options_init(NULL);

  thd->variables.wsrep_on= wsrep_on_saved;

  refresh_provider_options();

  return rcode;
}

void wsrep_provider_init (const char* value)
{
  WSREP_DEBUG("wsrep_provider_init: %s -> %s", 
              (wsrep_provider) ? wsrep_provider : "null", 
              (value) ? value : "null");
  if (NULL == value || wsrep_provider_verify (value))
  {
    WSREP_ERROR("Bad initial value for wsrep_provider: %s",
                (value ? value : ""));
    return;
  }

  if (wsrep_provider) my_free((void *)wsrep_provider);
  wsrep_provider = my_strdup(value, MYF(0));
}

bool wsrep_provider_options_check(sys_var *self, THD* thd, set_var* var)
{
  if (wsrep == NULL)
  {
    my_message(ER_WRONG_ARGUMENTS, "WSREP (galera) not started", MYF(0));
    return true;
  }
  return false;
}

bool wsrep_provider_options_update(sys_var *self, THD* thd, enum_var_type type)
{
  DBUG_ASSERT(wsrep);
  wsrep_status_t ret= wsrep->options_set(wsrep, wsrep_provider_options);
  if (ret != WSREP_OK)
  {
    WSREP_ERROR("Set options returned %d", ret);
    refresh_provider_options();
    return true;
  }
  return refresh_provider_options();
}

void wsrep_provider_options_init(const char* value)
{
  if (wsrep_provider_options && wsrep_provider_options != value) 
    my_free((void *)wsrep_provider_options);
  wsrep_provider_options = (value) ? my_strdup(value, MYF(0)) : NULL;
}

bool wsrep_reject_queries_update(sys_var *self, THD* thd, enum_var_type type)
{
    switch (wsrep_reject_queries) {
        case WSREP_REJECT_NONE:
            WSREP_INFO("Allowing client queries due to manual setting");
            break;
        case WSREP_REJECT_ALL:
            WSREP_INFO("Rejecting client queries due to manual setting");
            break;
        case WSREP_REJECT_ALL_KILL:
            wsrep_close_client_connections(FALSE);
            WSREP_INFO("Rejecting client queries and killing connections due to manual setting");
            break;
        default:
          WSREP_INFO("Unknown value for wsrep_reject_queries: %lu",
                     wsrep_reject_queries);
            return true;
    }
    return false;
}

static int wsrep_cluster_address_verify (const char* cluster_address_str)
{
  /* There is no predefined address format, it depends on provider. */
  return 0;
}

bool wsrep_cluster_address_check (sys_var *self, THD* thd, set_var* var)
{
  char addr_buf[FN_REFLEN];

  if ((! var->save_result.string_value.str) ||
      (var->save_result.string_value.length >= sizeof(addr_buf))) // safety
    goto err;

  strmake(addr_buf, var->save_result.string_value.str,
          MY_MIN(sizeof(addr_buf)-1, var->save_result.string_value.length));

  if (!wsrep_cluster_address_verify(addr_buf))
    return 0;

 err:
  my_error(ER_WRONG_VALUE_FOR_VAR, MYF(0), var->var->name.str,
           var->save_result.string_value.str ?
           var->save_result.string_value.str : "NULL");
  return 1;
}

bool wsrep_cluster_address_update (sys_var *self, THD* thd, enum_var_type type)
{
  bool wsrep_on_saved;

  /* Do not proceed if wsrep provider is not loaded. */
  if (!wsrep)
  {
    WSREP_INFO("wsrep provider is not loaded, can't re(start) replication.");
    return false;
  }

  wsrep_on_saved= thd->variables.wsrep_on;
  thd->variables.wsrep_on= false;

  /* stop replication is heavy operation, and includes closing all client 
     connections. Closing clients may need to get LOCK_global_system_variables
     at least in MariaDB.

     Note: releasing LOCK_global_system_variables may cause race condition, if 
     there can be several concurrent clients changing wsrep_provider
  */
  mysql_mutex_unlock(&LOCK_global_system_variables);
  wsrep_stop_replication(thd);

  /*
    Unlock and lock LOCK_wsrep_slave_threads to maintain lock order & avoid
    any potential deadlock.
  */
  mysql_mutex_unlock(&LOCK_wsrep_slave_threads);
  mysql_mutex_lock(&LOCK_global_system_variables);
  mysql_mutex_lock(&LOCK_wsrep_slave_threads);

  if (wsrep_start_replication())
  {
    wsrep_create_rollbacker();
    wsrep_create_appliers(wsrep_slave_threads);
  }

  thd->variables.wsrep_on= wsrep_on_saved;

  return false;
}

void wsrep_cluster_address_init (const char* value)
{
  WSREP_DEBUG("wsrep_cluster_address_init: %s -> %s", 
              (wsrep_cluster_address) ? wsrep_cluster_address : "null", 
              (value) ? value : "null");

  my_free((void*) wsrep_cluster_address);
  wsrep_cluster_address= my_strdup(value ? value : "", MYF(0));
}

/* wsrep_cluster_name cannot be NULL or an empty string. */
bool wsrep_cluster_name_check (sys_var *self, THD* thd, set_var* var)
{
  if (!var->save_result.string_value.str ||
      (var->save_result.string_value.length == 0))
  {
    my_error(ER_WRONG_VALUE_FOR_VAR, MYF(0), var->var->name.str,
             (var->save_result.string_value.str ?
              var->save_result.string_value.str : "NULL"));
    return 1;
  }
  return 0;
}

bool wsrep_cluster_name_update (sys_var *self, THD* thd, enum_var_type type)
{
  return 0;
}

bool wsrep_node_name_check (sys_var *self, THD* thd, set_var* var)
{
  // TODO: for now 'allow' 0-length string to be valid (default)
  if (!var->save_result.string_value.str)
  {
    my_error(ER_WRONG_VALUE_FOR_VAR, MYF(0), var->var->name.str,
             (var->save_result.string_value.str ?
              var->save_result.string_value.str : "NULL"));
    return 1;
  }
  return 0;
}

bool wsrep_node_name_update (sys_var *self, THD* thd, enum_var_type type)
{
  return 0;
}

// TODO: do something more elaborate, like checking connectivity
bool wsrep_node_address_check (sys_var *self, THD* thd, set_var* var)
{
  char addr_buf[FN_REFLEN];

  if ((! var->save_result.string_value.str) ||
      (var->save_result.string_value.length > (FN_REFLEN - 1))) // safety
    goto err;

  memcpy(addr_buf, var->save_result.string_value.str,
         var->save_result.string_value.length);
  addr_buf[var->save_result.string_value.length]= 0;

  // TODO: for now 'allow' 0-length string to be valid (default)
  return 0;

err:
  my_error(ER_WRONG_VALUE_FOR_VAR, MYF(0), var->var->name.str,
           var->save_result.string_value.str ?
           var->save_result.string_value.str : "NULL");
  return 1;
}

bool wsrep_node_address_update (sys_var *self, THD* thd, enum_var_type type)
{
  return 0;
}

void wsrep_node_address_init (const char* value)
{
  if (wsrep_node_address && strcmp(wsrep_node_address, value))
    my_free ((void*)wsrep_node_address);

  wsrep_node_address = (value) ? my_strdup(value, MYF(0)) : NULL;
}

static void wsrep_slave_count_change_update ()
{
  wsrep_slave_count_change = (wsrep_slave_threads - wsrep_prev_slave_threads);
  WSREP_DEBUG("Change on slave threads: New %lu old %lu difference %lu",
	  wsrep_slave_threads, wsrep_prev_slave_threads, wsrep_slave_count_change);
  wsrep_prev_slave_threads = wsrep_slave_threads;
}

bool wsrep_slave_threads_update (sys_var *self, THD* thd, enum_var_type type)
{
  wsrep_slave_count_change_update();
  if (wsrep_slave_count_change > 0)
  {
    wsrep_create_appliers(wsrep_slave_count_change);
    wsrep_slave_count_change = 0;
  }
  return false;
}

bool wsrep_desync_check (sys_var *self, THD* thd, set_var* var)
{
  if (wsrep == NULL)
  {
    my_message(ER_WRONG_ARGUMENTS, "WSREP (galera) not started", MYF(0));
    return true;
  }

  bool new_wsrep_desync= (bool) var->save_result.ulonglong_value;
  if (wsrep_desync == new_wsrep_desync) {
    if (new_wsrep_desync) {
      push_warning (thd, Sql_condition::WARN_LEVEL_WARN,
                   ER_WRONG_VALUE_FOR_VAR,
                   "'wsrep_desync' is already ON.");
    } else {
      push_warning (thd, Sql_condition::WARN_LEVEL_WARN,
                   ER_WRONG_VALUE_FOR_VAR,
                   "'wsrep_desync' is already OFF.");
    }
    return false;
  }
  wsrep_status_t ret(WSREP_WARNING);
  if (new_wsrep_desync) {
    ret = wsrep->desync (wsrep);
    if (ret != WSREP_OK) {
      WSREP_WARN ("SET desync failed %d for schema: %s, query: %s",
                  ret, thd->get_db(), thd->query());
      my_error (ER_CANNOT_USER, MYF(0), "'desync'", thd->query());
      return true;
    }
  } else {
    ret = wsrep->resync (wsrep);
    if (ret != WSREP_OK) {
      WSREP_WARN ("SET resync failed %d for schema: %s, query: %s", ret,
                  thd->get_db(), thd->query());
      my_error (ER_CANNOT_USER, MYF(0), "'resync'", thd->query());
      return true;
    }
  }
  return false;
}

bool wsrep_desync_update (sys_var *self, THD* thd, enum_var_type type)
{
  DBUG_ASSERT(wsrep);
  return false;
}

bool wsrep_max_ws_size_check(sys_var *self, THD* thd, set_var* var)
{
  if (wsrep == NULL)
  {
    my_message(ER_WRONG_ARGUMENTS, "WSREP (galera) not started", MYF(0));
    return true;
  }
  return false;
}

bool wsrep_max_ws_size_update (sys_var *self, THD *thd, enum_var_type)
{
  DBUG_ASSERT(wsrep);

  char max_ws_size_opt[128];
  my_snprintf(max_ws_size_opt, sizeof(max_ws_size_opt),
              "repl.max_ws_size=%lu", wsrep_max_ws_size);
  wsrep_status_t ret= wsrep->options_set(wsrep, max_ws_size_opt);
  if (ret != WSREP_OK)
  {
    WSREP_ERROR("Set options returned %d", ret);
    refresh_provider_options();
    return true;
  }
  return refresh_provider_options();
}

static SHOW_VAR wsrep_status_vars[]=
{
  {"connected",         (char*) &wsrep_connected,         SHOW_BOOL},
  {"ready",             (char*) &wsrep_ready,             SHOW_BOOL},
  {"cluster_state_uuid",(char*) &wsrep_cluster_state_uuid,SHOW_CHAR_PTR},
  {"cluster_conf_id",   (char*) &wsrep_cluster_conf_id,   SHOW_LONGLONG},
  {"cluster_status",    (char*) &wsrep_cluster_status,    SHOW_CHAR_PTR},
  {"cluster_size",      (char*) &wsrep_cluster_size,      SHOW_LONG_NOFLUSH},
  {"local_index",       (char*) &wsrep_local_index,       SHOW_LONG_NOFLUSH},
  {"local_bf_aborts",   (char*) &wsrep_show_bf_aborts,    SHOW_SIMPLE_FUNC},
  {"provider_name",     (char*) &wsrep_provider_name,     SHOW_CHAR_PTR},
  {"provider_version",  (char*) &wsrep_provider_version,  SHOW_CHAR_PTR},
  {"provider_vendor",   (char*) &wsrep_provider_vendor,   SHOW_CHAR_PTR},
  {"thread_count",      (char*) &wsrep_running_threads,   SHOW_LONG_NOFLUSH}
};

static int show_var_cmp(const void *var1, const void *var2)
{
  return strcasecmp(((SHOW_VAR*)var1)->name, ((SHOW_VAR*)var2)->name);
}

int wsrep_show_status (THD *thd, SHOW_VAR *var, char *buff,
                       enum enum_var_type scope)
{
  uint i, maxi= SHOW_VAR_FUNC_BUFF_SIZE / sizeof(*var) - 1;
  SHOW_VAR *v= (SHOW_VAR *)buff;

  var->type= SHOW_ARRAY;
  var->value= buff;

  for (i=0; i < array_elements(wsrep_status_vars); i++)
    *v++= wsrep_status_vars[i];

  DBUG_ASSERT(i < maxi);

  if (wsrep != NULL)
  {
    wsrep_stats_var* stats= wsrep->stats_get(wsrep);
    for (wsrep_stats_var *sv= stats;
         i < maxi && sv && sv->name; i++,
           sv++, v++)
    {
      v->name = thd->strdup(sv->name);
      switch (sv->type) {
      case WSREP_VAR_INT64:
        v->value = (char*)thd->memdup(&sv->value._integer64, sizeof(longlong));
        v->type  = SHOW_LONGLONG;
        break;
      case WSREP_VAR_STRING:
        v->value = thd->strdup(sv->value._string);
        v->type  = SHOW_CHAR;
        break;
      case WSREP_VAR_DOUBLE:
        v->value = (char*)thd->memdup(&sv->value._double, sizeof(double));
        v->type  = SHOW_DOUBLE;
        break;
      }
    }
    wsrep->stats_free(wsrep, stats);
  }

  my_qsort(buff, i, sizeof(*v), show_var_cmp);

  v->name= 0;                                   // terminator
  return 0;
}