MDEV-6805 one can set character_set_client to utf32

use the same restriction for character_set_client on the command line
and from SQL.

Also: remove strange hack from thd_init_client_charset() that contradicted
the manual (collation_connection and character_set_result were not always set)

mysql-test/r/ctype_ucs2_def.result

+call mtr.add_suppression("Cannot use ucs2 as character_set_client");
 show variables like 'collation_server';
 Variable_name	Value
 collation_server	ucs2_unicode_ci

mysql-test/r/ctype_ucs2_query_cache.result

+call mtr.add_suppression("Cannot use ucs2 as character_set_client");
 #
 # Start of 5.5 tests
 #

mysql-test/r/ctype_utf16_def.result

+call mtr.add_suppression("Cannot use utf16 as character_set_client");
 SHOW VARIABLES LIKE 'collation_server';
 Variable_name	Value
 collation_server	utf16_general_ci

mysql-test/suite/sys_vars/r/character_set_connection_func.result

@@ -11,7 +11,7 @@ SELECT @@global.character_set_connection;
 utf8
 SELECT @@session.character_set_connection;
 @@session.character_set_connection
-utf8
+latin1
 '#--------------------FN_DYNVARS_011_02-------------------------#'
 'connection default'
 DROP TABLE IF EXISTS t1;

mysql-test/suite/sys_vars/r/character_set_results_func.result

@@ -9,7 +9,7 @@ SELECT @@global.character_set_results;
 utf8
 SELECT @@session.character_set_results;
 @@session.character_set_results
-utf8
+latin1
 '#--------------------FN_DYNVARS_012_02-------------------------#'
 'connection default'
 DROP TABLE IF EXISTS t1;

mysql-test/suite/sys_vars/r/collation_connection_func.result

@@ -9,7 +9,7 @@ SELECT @@global.collation_connection;
 latin1_danish_ci
 SELECT @@session.collation_connection;
 @@session.collation_connection
-latin1_danish_ci
+latin1_swedish_ci
 '#--------------------FN_DYNVARS_015_02-------------------------#'
 'connection default'
 DROP TABLE IF EXISTS t1;

mysql-test/t/ctype_ucs2_def.test

 -- source include/have_ucs2.inc
 
+call mtr.add_suppression("Cannot use ucs2 as character_set_client");
+
 #
 # MySQL Bug#15276: MySQL ignores collation-server
 #

mysql-test/t/ctype_ucs2_query_cache.test

 -- source include/have_query_cache.inc
 -- source include/have_ucs2.inc
 
+call mtr.add_suppression("Cannot use ucs2 as character_set_client");
+
 --echo #
 --echo # Start of 5.5 tests
 --echo #

mysql-test/t/ctype_utf16_def.test

 --source include/have_utf16.inc
+call mtr.add_suppression("Cannot use utf16 as character_set_client");
 
 #
 # Bug #32391  	Character sets: crash with --character-set-server

sql/mysqld.cc

@@ -4268,7 +4268,15 @@ static int init_common_variables()
   global_system_variables.collation_database=	 default_charset_info;
   global_system_variables.collation_connection=  default_charset_info;
   global_system_variables.character_set_results= default_charset_info;
-  global_system_variables.character_set_client=  default_charset_info;
+  if (default_charset_info->mbminlen > 1)
+  {
+    global_system_variables.character_set_client=  &my_charset_latin1;
+    sql_print_warning("Cannot use %s as character_set_client, %s will be used instead",
+                      default_charset_info->csname,
+                      global_system_variables.character_set_client->csname);
+  }
+  else
+    global_system_variables.character_set_client=  default_charset_info;
 
   if (!(character_set_filesystem=
         get_charset_by_csname(character_set_filesystem_name,

sql/sql_connect.cc

@@ -837,14 +837,10 @@ bool thd_init_client_charset(THD *thd, uint cs_number)
    Use server character set and collation if
    - opt_character_set_client_handshake is not set
    - client has not specified a character set
-   - client character set is the same as the servers
    - client character set doesn't exists in server
   */
   if (!opt_character_set_client_handshake ||
-      !(cs= get_charset(cs_number, MYF(0))) ||
-      !my_strcasecmp(&my_charset_latin1,
-                     global_system_variables.character_set_client->name,
-                     cs->name))
+      !(cs= get_charset(cs_number, MYF(0))))
   {
     thd->variables.character_set_client=
       global_system_variables.character_set_client;