Merge mysql.com:/home/ram/work/mysql-5.1-maint

into  mysql.com:/home/ram/work/b31615/b31615.5.1

mysql-test/r/ctype_ucs.result

@@ -811,6 +811,14 @@ quote(name)
 ????????
 ????????????????
 drop table bug20536;
+set names ucs2;
+ERROR 42000: Variable 'character_set_client' can't be set to the value of 'ucs2'
+set names ucs2 collate ucs2_bin;
+ERROR 42000: Variable 'character_set_client' can't be set to the value of 'ucs2'
+set character_set_client= ucs2;
+ERROR 42000: Variable 'character_set_client' can't be set to the value of 'ucs2'
+set character_set_client= concat('ucs', substr('2', 1));
+ERROR 42000: Variable 'character_set_client' can't be set to the value of 'ucs2'
 End of 4.1 tests
 CREATE TABLE t1 (a varchar(64) character set ucs2, b decimal(10,3));
 INSERT INTO t1 VALUES ("1.1", 0), ("2.1", 0);

mysql-test/t/ctype_ucs.test

@@ -547,6 +547,18 @@ select quote(name) from bug20536;
 
 drop table bug20536;
 
+#
+# Bug #31615: crash after set names ucs2 collate xxx
+#
+--error 1231
+set names ucs2;
+--error 1231
+set names ucs2 collate ucs2_bin;
+--error 1231
+set character_set_client= ucs2;
+--error 1231
+set character_set_client= concat('ucs', substr('2', 1));
+
 --echo End of 4.1 tests
 
 #

sql/set_var.cc

@@ -164,7 +164,8 @@ static sys_var_character_set_sv	sys_character_set_server(&vars, "character_set_s
 sys_var_const_str       sys_charset_system(&vars, "character_set_system",
                                            (char *)my_charset_utf8_general_ci.name);
 static sys_var_character_set_database	sys_character_set_database(&vars, "character_set_database");
-static sys_var_character_set_sv sys_character_set_client(&vars, "character_set_client",
+static sys_var_character_set_client sys_character_set_client(&vars, 
+                                        "character_set_client",
                                         &SV::character_set_client,
                                         &default_charset_info);
 static sys_var_character_set_sv sys_character_set_connection(&vars, "character_set_connection",
@@ -1861,6 +1862,21 @@ CHARSET_INFO **sys_var_character_set_sv::ci_ptr(THD *thd, enum_var_type type)
 }
 
 
+bool sys_var_character_set_client::check(THD *thd, set_var *var)
+{
+  if (sys_var_character_set_sv::check(thd, var))
+    return 1;
+  /* Currently, UCS-2 cannot be used as a client character set */
+  if (var->save_result.charset->mbminlen > 1)
+  {
+    my_error(ER_WRONG_VALUE_FOR_VAR, MYF(0), name, 
+             var->save_result.charset->csname);
+    return 1;
+  }
+  return 0;
+}
+
+
 CHARSET_INFO ** sys_var_character_set_database::ci_ptr(THD *thd,
 						       enum_var_type type)
 {
@@ -2290,6 +2306,13 @@ uchar *sys_var_log_output::value_ptr(THD *thd, enum_var_type type,
 
 int set_var_collation_client::check(THD *thd)
 {
+  /* Currently, UCS-2 cannot be used as a client character set */
+  if (character_set_client->mbminlen > 1)
+  {
+    my_error(ER_WRONG_VALUE_FOR_VAR, MYF(0), "character_set_client",
+             character_set_client->csname);
+    return 1;
+  }
   return 0;
 }
 

sql/set_var.h

@@ -667,6 +667,20 @@ public:
 };
 
 
+class sys_var_character_set_client: public sys_var_character_set_sv
+{
+public:
+  sys_var_character_set_client(sys_var_chain *chain, const char *name_arg,
+                               CHARSET_INFO *SV::*offset_arg,
+                               CHARSET_INFO **global_default_arg,
+                               bool is_nullable= 0)
+    : sys_var_character_set_sv(chain, name_arg, offset_arg, global_default_arg,
+                               is_nullable)
+  { }
+  bool check(THD *thd, set_var *var);
+};
+
+
 class sys_var_character_set_database :public sys_var_character_set
 {
 public: