Bug #28550 "Potential bugs related to the return type of the CHAR function".

  
Since, as of MySQL 5.0.15, CHAR() arguments larger than 255 are converted into multiple result bytes, a single CHAR() argument can now take up to 4 bytes. This patch fixes Item_func_char::fix_length_and_dec() to take this into account.
  
This patch also fixes a regression introduced by the patch for bug21513. As now we do not always have the 'name' member of Item set for Item_hex_string and Item_bin_string, an own print() method has been added to Item_hex_string so that it could correctly be printed by Item_func::print_args().

mysql-test/r/func_str.result

@@ -726,7 +726,7 @@ t1	CREATE TABLE `t1` (
   `oct(130)` varchar(64) NOT NULL default '',
   `conv(130,16,10)` varchar(64) NOT NULL default '',
   `hex(130)` varchar(6) NOT NULL default '',
-  `char(130)` varbinary(1) NOT NULL default '',
+  `char(130)` varbinary(4) NOT NULL default '',
   `format(130,10)` varchar(4) NOT NULL default '',
   `left(_latin2'a',1)` varchar(1) character set latin2 NOT NULL default '',
   `right(_latin2'a',1)` varchar(1) character set latin2 NOT NULL default '',
@@ -2153,4 +2153,14 @@ SUBSTR(a,1,len)
 ba
 
 DROP TABLE t1;
+CREATE TABLE t1 AS SELECT CHAR(0x414243) as c1;
+SELECT HEX(c1) from t1;
+HEX(c1)
+414243
+DROP TABLE t1;
+CREATE VIEW v1 AS SELECT CHAR(0x414243) as c1;
+SELECT HEX(c1) from v1;
+HEX(c1)
+414243
+DROP VIEW v1;
 End of 5.0 tests

mysql-test/t/func_str.test

@@ -1124,4 +1124,16 @@ SELECT SUBSTR(a,1,len) FROM t1;
 
 DROP TABLE t1; 
 
+#
+# Bug #28850: Potential bugs related to the return type of the CHAR function
+#
+
+CREATE TABLE t1 AS SELECT CHAR(0x414243) as c1;
+SELECT HEX(c1) from t1;
+DROP TABLE t1;
+
+CREATE VIEW v1 AS SELECT CHAR(0x414243) as c1;
+SELECT HEX(c1) from v1;
+DROP VIEW v1;
+
 --echo End of 5.0 tests

sql/item.cc

@@ -4807,6 +4807,19 @@ warn:
 }
 
 
+void Item_hex_string::print(String *str)
+{
+  char *end= (char*) str_value.ptr() + str_value.length(),
+       *ptr= end - min(str_value.length(), sizeof(longlong));
+  str->append("0x");
+  for (; ptr != end ; ptr++)
+  {
+    str->append(_dig_vec_lower[((uchar) *ptr) >> 4]);
+    str->append(_dig_vec_lower[((uchar) *ptr) & 0x0F]);
+  }
+}
+
+
 bool Item_hex_string::eq(const Item *arg, bool binary_cmp) const
 {
   if (arg->basic_const_item() && arg->type() == type())

sql/item.h

@@ -1858,6 +1858,7 @@ public:
   enum_field_types field_type() const { return MYSQL_TYPE_VARCHAR; }
   // to prevent drop fixed flag (no need parent cleanup call)
   void cleanup() {}
+  void print(String *str);
   bool eq(const Item *item, bool binary_cmp) const;
   virtual Item *safe_charset_converter(CHARSET_INFO *tocs);
 };

sql/item_strfunc.h

@@ -534,7 +534,7 @@ public:
   String *val_str(String *);
   void fix_length_and_dec() 
   {
-    max_length= arg_count * collation.collation->mbmaxlen;
+    max_length= arg_count * 4;
   }
   const char *func_name() const { return "char"; }
 };