Patch for BUG#30472: libmysql doesn't reset charset,

insert_id after succ. mysql_change_user() call.

See also WL 4066.
  
This bug reveals two problems:
  - the problem on the client side which was described originally;
  - the problem in protocol / the server side: connection context
    on client and server should be like after mysql_real_connect()
    and be consistent. The server however just resets character
    set variables to the global defaults.

The fix seems to be as follows:
  - extend the protocol so that the client be able to send
    character set information in COM_CHANGE_USER command;
  - change the server so that it understands client character set
    in the command;
  - change the client:
    - reset character set to the default value (which has been
      read from the configuration);
    - send character set in COM_CHANGE_USER command.

client/client_priv.h

@@ -82,3 +82,7 @@ enum options_client
   OPT_DEBUG_INFO, OPT_DEBUG_CHECK, OPT_COLUMN_TYPES, OPT_ERROR_LOG_FILE,
   OPT_WRITE_BINLOG, OPT_MAX_CLIENT_OPTION
 };
+
+C_MODE_START
+extern int mysql_init_character_set(MYSQL *mysql);
+C_MODE_END

libmysql/libmysql.c

@@ -685,14 +685,25 @@ int cli_read_change_user_result(MYSQL *mysql, char *buff, const char *passwd)
   return 0;
 }
 
-
 my_bool	STDCALL mysql_change_user(MYSQL *mysql, const char *user,
 				  const char *passwd, const char *db)
 {
   char buff[512],*end=buff;
   int rc;
+  CHARSET_INFO *saved_cs= mysql->charset;
+
   DBUG_ENTER("mysql_change_user");
 
+  /* Get the connection-default character set. */
+
+  if (mysql_init_character_set(mysql))
+  {
+    mysql->charset= saved_cs;
+    DBUG_RETURN(TRUE);
+  }
+
+  /* Use an empty string instead of NULL. */
+
   if (!user)
     user="";
   if (!passwd)
@@ -721,6 +732,14 @@ my_bool	STDCALL mysql_change_user(MYSQL *mysql, const char *user,
   /* Add database if needed */
   end= strmov(end, db ? db : "") + 1;
 
+  /* Add character set number. */
+
+  if (mysql->server_capabilities & CLIENT_SECURE_CONNECTION)
+  {
+    *end= (uchar) mysql->charset->number;
+    ++end;
+  }
+
   /* Write authentication package */
   simple_command(mysql,COM_CHANGE_USER, (uchar*) buff, (ulong) (end-buff), 1);
 
@@ -743,6 +762,11 @@ my_bool	STDCALL mysql_change_user(MYSQL *mysql, const char *user,
     mysql->passwd=my_strdup(passwd,MYF(MY_WME));
     mysql->db=    db ? my_strdup(db,MYF(MY_WME)) : 0;
   }
+  else
+  {
+    mysql->charset= saved_cs;
+  }
+
   DBUG_RETURN(rc);
 }
 

mysql-test/t/mysql_client_test.test

@@ -8,8 +8,8 @@
 # server or run mysql-test-run --debug mysql_client_test and check
 # var/log/mysql_client_test.trace
 
---exec echo "$MYSQL_CLIENT_TEST" > $MYSQLTEST_VARDIR/log/mysql_client_test.log 2>&1
---exec $MYSQL_CLIENT_TEST --getopt-ll-test=25600M >> $MYSQLTEST_VARDIR/log/mysql_client_test.log 2>&1
+--exec echo "$MYSQL_CLIENT_TEST" > $MYSQLTEST_VARDIR/log/mysql_client_test.out.log 2>&1
+--exec $MYSQL_CLIENT_TEST --getopt-ll-test=25600M >> $MYSQLTEST_VARDIR/log/mysql_client_test.out.log 2>&1
 
 # End of 4.1 tests
 echo ok;

sql/sql_parse.cc

@@ -876,7 +876,13 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
       my_message(ER_UNKNOWN_COM_ERROR, ER(ER_UNKNOWN_COM_ERROR), MYF(0));
       break;
     }
-    db_length= packet_end - db - 1; /* do not count the trailing '\0'  */
+    db_length= strlen(db);
+
+    uint cs_number= 0;
+
+    if (db + db_length < packet_end)
+      cs_number= (uchar) *(db + db_length + 1);
+
     /* Convert database name to utf8 */
     db_buff[copy_and_convert(db_buff, sizeof(db_buff)-1,
                              system_charset_info, db, db_length,
@@ -921,6 +927,12 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
 #endif /* NO_EMBEDDED_ACCESS_CHECKS */
       x_free((uchar*) save_db);
       x_free((uchar*)  save_security_ctx.user);
+
+      if (cs_number)
+      {
+        thd_init_client_charset(thd, cs_number);
+        thd->update_charset();
+      }
     }
     break;
   }

tests/mysql_client_test.c

@@ -119,6 +119,8 @@ static void client_disconnect(void);
 
 #define DIE_UNLESS(expr) \
         ((void) ((expr) ? 0 : (die(__FILE__, __LINE__, #expr), 0)))
+#define DIE_IF(expr) \
+        ((void) ((expr) ? (die(__FILE__, __LINE__, #expr), 0) : 0))
 #define DIE(expr) \
         die(__FILE__, __LINE__, #expr)
 
@@ -177,8 +179,8 @@ if (stmt == 0) \
 DIE_UNLESS(stmt == 0);\
 }
 
-#define mytest(x) if (!x) {myerror(NULL);DIE_UNLESS(FALSE);}
-#define mytest_r(x) if (x) {myerror(NULL);DIE_UNLESS(FALSE);}
+#define mytest(x) if (!(x)) {myerror(NULL);DIE_UNLESS(FALSE);}
+#define mytest_r(x) if ((x)) {myerror(NULL);DIE_UNLESS(FALSE);}
 
 
 /* A workaround for Sun Forte 5.6 on Solaris x86 */
@@ -16649,6 +16651,175 @@ static void test_bug29306()
 
   DBUG_VOID_RETURN;
 }
+/*
+  Bug#30472: libmysql doesn't reset charset, insert_id after succ.
+  mysql_change_user() call row insertions.
+*/
+
+static void bug30472_retrieve_charset_info(MYSQL *con,
+                                           char *character_set_name,
+                                           char *character_set_client,
+                                           char *character_set_results,
+                                           char *collation_connection)
+{
+  MYSQL_RES *rs;
+  MYSQL_ROW row;
+
+  /* Get the cached client character set name. */
+
+  strcpy(character_set_name, mysql_character_set_name(con));
+
+  /* Retrieve server character set information. */
+
+  DIE_IF(mysql_query(con, "SHOW VARIABLES LIKE 'character_set_client'"));
+  DIE_UNLESS(rs= mysql_store_result(con));
+  DIE_UNLESS(row= mysql_fetch_row(rs));
+  strcpy(character_set_client, row[1]);
+  mysql_free_result(rs);
+
+  DIE_IF(mysql_query(con, "SHOW VARIABLES LIKE 'character_set_results'"));
+  DIE_UNLESS(rs= mysql_store_result(con));
+  DIE_UNLESS(row= mysql_fetch_row(rs));
+  strcpy(character_set_results, row[1]);
+  mysql_free_result(rs);
+
+  DIE_IF(mysql_query(con, "SHOW VARIABLES LIKE 'collation_connection'"));
+  DIE_UNLESS(rs= mysql_store_result(con));
+  DIE_UNLESS(row= mysql_fetch_row(rs));
+  strcpy(collation_connection, row[1]);
+  mysql_free_result(rs);
+}
+
+static void test_bug30472()
+{
+  MYSQL con;
+
+  char character_set_name_1[MY_CS_NAME_SIZE];
+  char character_set_client_1[MY_CS_NAME_SIZE];
+  char character_set_results_1[MY_CS_NAME_SIZE];
+  char collation_connnection_1[MY_CS_NAME_SIZE];
+
+  char character_set_name_2[MY_CS_NAME_SIZE];
+  char character_set_client_2[MY_CS_NAME_SIZE];
+  char character_set_results_2[MY_CS_NAME_SIZE];
+  char collation_connnection_2[MY_CS_NAME_SIZE];
+
+  char character_set_name_3[MY_CS_NAME_SIZE];
+  char character_set_client_3[MY_CS_NAME_SIZE];
+  char character_set_results_3[MY_CS_NAME_SIZE];
+  char collation_connnection_3[MY_CS_NAME_SIZE];
+
+  char character_set_name_4[MY_CS_NAME_SIZE];
+  char character_set_client_4[MY_CS_NAME_SIZE];
+  char character_set_results_4[MY_CS_NAME_SIZE];
+  char collation_connnection_4[MY_CS_NAME_SIZE];
+
+  /* Create a new connection. */
+
+  DIE_UNLESS(mysql_init(&con));
+
+  DIE_UNLESS(mysql_real_connect(&con,
+                                opt_host,
+                                opt_user,
+                                opt_password,
+                                opt_db ? opt_db : "test",
+                                opt_port,
+                                opt_unix_socket,
+                                CLIENT_FOUND_ROWS));
+
+  /* Retrieve character set information. */
+
+  bug30472_retrieve_charset_info(&con,
+                                 character_set_name_1,
+                                 character_set_client_1,
+                                 character_set_results_1,
+                                 collation_connnection_1);
+
+  /* Switch client character set. */
+
+  DIE_IF(mysql_set_character_set(&con, "utf8"));
+
+  /* Retrieve character set information. */
+
+  bug30472_retrieve_charset_info(&con,
+                                 character_set_name_2,
+                                 character_set_client_2,
+                                 character_set_results_2,
+                                 collation_connnection_2);
+
+  /*
+    Check that
+      1) character set has been switched and
+      2) new character set is different from the original one.
+  */
+
+  DIE_UNLESS(strcmp(character_set_name_2, "utf8") == 0);
+  DIE_UNLESS(strcmp(character_set_client_2, "utf8") == 0);
+  DIE_UNLESS(strcmp(character_set_results_2, "utf8") == 0);
+  DIE_UNLESS(strcmp(collation_connnection_2, "utf8_general_ci") == 0);
+
+  DIE_UNLESS(strcmp(character_set_name_1, character_set_name_2) != 0);
+  DIE_UNLESS(strcmp(character_set_client_1, character_set_client_2) != 0);
+  DIE_UNLESS(strcmp(character_set_results_1, character_set_results_2) != 0);
+  DIE_UNLESS(strcmp(collation_connnection_1, collation_connnection_2) != 0);
+
+  /* Call mysql_change_user() with the same username, password, database. */
+
+  DIE_IF(mysql_change_user(&con,
+                           opt_user,
+                           opt_password,
+                           opt_db ? opt_db : "test"));
+
+  /* Retrieve character set information. */
+
+  bug30472_retrieve_charset_info(&con,
+                                 character_set_name_3,
+                                 character_set_client_3,
+                                 character_set_results_3,
+                                 collation_connnection_3);
+
+  /* Check that character set information has been reset. */
+
+  DIE_UNLESS(strcmp(character_set_name_1, character_set_name_3) == 0);
+  DIE_UNLESS(strcmp(character_set_client_1, character_set_client_3) == 0);
+  DIE_UNLESS(strcmp(character_set_results_1, character_set_results_3) == 0);
+  DIE_UNLESS(strcmp(collation_connnection_1, collation_connnection_3) == 0);
+
+  /* Change connection-default character set in the client. */
+
+  con.options.charset_name= my_strdup("utf8", MYF(MY_FAE));
+
+  /*
+    Call mysql_change_user() in order to check that new connection will
+    have UTF8 character set on the client and on the server.
+  */
+
+  DIE_IF(mysql_change_user(&con,
+                           opt_user,
+                           opt_password,
+                           opt_db ? opt_db : "test"));
+
+  /* Retrieve character set information. */
+
+  bug30472_retrieve_charset_info(&con,
+                                 character_set_name_4,
+                                 character_set_client_4,
+                                 character_set_results_4,
+                                 collation_connnection_4);
+
+  /* Check that we have UTF8 on the server and on the client. */
+
+  DIE_UNLESS(strcmp(character_set_name_4, "utf8") == 0);
+  DIE_UNLESS(strcmp(character_set_client_4, "utf8") == 0);
+  DIE_UNLESS(strcmp(character_set_results_4, "utf8") == 0);
+  DIE_UNLESS(strcmp(collation_connnection_4, "utf8_general_ci") == 0);
+
+  /* That's it. Cleanup. */
+
+  mysql_close(&con);
+}
+
+
 /*
   Read and parse arguments and MySQL options from my.cnf
 */
@@ -16943,6 +17114,7 @@ static struct my_tests_st my_tests[]= {
   { "test_bug29692", test_bug29692 },
   { "test_bug29306", test_bug29306 },
   { "test_change_user", test_change_user },
+  { "test_bug30472", test_bug30472 },
   { 0, 0 }
 };