Merge salvation.intern.azundris.com:/home/tnurnberg/21913/my41-21913

into  salvation.intern.azundris.com:/home/tnurnberg/21913/my50-21913

21913: DATE_FORMAT() Crashes mysql server if I use it through mysql-connector-j driver.

Variable character_set_results can legally be NULL (for "no conversion.")
This could result in a NULL deref that crashed the server.  Fixed.

(Although ran some additional precursory tests to see whether I could break
anything else, but no breakage so far.)


mysql-test/r/func_time.result:
  Bug#21913: DATE_FORMAT() Crashes mysql server if I use it through mysql-connector-j driver.
  
  Prove DATE_FORMAT() no longer crashes the server when character_set_results is
  NULL (which is a legal value and means, "no conversion").
mysql-test/t/func_time.test:
  Bug#21913: DATE_FORMAT() Crashes mysql server if I use it through mysql-connector-j driver.
  
  Prove DATE_FORMAT() no longer crashes the server when character_set_results is
  NULL (which is a legal value and means, "no conversion").
sql/sql_string.cc:
  Bug#21913: DATE_FORMAT() Crashes mysql server if I use it through mysql-connector-j driver.
  
  Avoid NULL deref in my_charset_same() -- if !to_cs, we won't need to compare
  because it is magic for, "no conversion."

mysql-test/r/func_time.result

@@ -960,3 +960,15 @@ id	day	id	day
 3	2005-07-01	3	2005-07-15
 DROP TABLE t1,t2;
 set time_zone= @@global.time_zone;
+SET NAMES latin1;
+SET character_set_results = NULL;
+SHOW VARIABLES LIKE 'character_set_results';
+Variable_name	Value
+character_set_results	
+CREATE TABLE testBug8868 (field1 DATE, field2 VARCHAR(32) CHARACTER SET BINARY);
+INSERT INTO testBug8868 VALUES ('2006-09-04', 'abcd');
+SELECT DATE_FORMAT(field1,'%b-%e %l:%i%p') as fmtddate, field2 FROM testBug8868;
+fmtddate	field2
+Sep-4 12:00AM	abcd
+DROP TABLE testBug8868;
+SET NAMES DEFAULT;

mysql-test/t/func_time.test

@@ -534,3 +534,21 @@ DROP TABLE t1,t2;
 
 # Restore timezone to default
 set time_zone= @@global.time_zone;
+
+#
+# 21913: DATE_FORMAT() Crashes mysql server if I use it through
+#        mysql-connector-j driver.
+#
+
+SET NAMES latin1;
+SET character_set_results = NULL;
+SHOW VARIABLES LIKE 'character_set_results';
+
+CREATE TABLE testBug8868 (field1 DATE, field2 VARCHAR(32) CHARACTER SET BINARY);
+INSERT INTO testBug8868 VALUES ('2006-09-04', 'abcd');
+
+SELECT DATE_FORMAT(field1,'%b-%e %l:%i%p') as fmtddate, field2 FROM testBug8868;
+
+DROP TABLE testBug8868;
+
+SET NAMES DEFAULT;

sql/sql_string.cc

@@ -248,6 +248,10 @@ bool String::copy(const char *str,uint32 arg_length, CHARSET_INFO *cs)
    0  No conversion needed
    1  Either character set conversion or adding leading  zeros
       (e.g. for UCS-2) must be done
+
+  NOTE
+  to_cs may be NULL for "no conversion" if the system variable
+  character_set_results is NULL.
 */
 
 bool String::needs_conversion(uint32 arg_length,
@@ -256,7 +260,8 @@ bool String::needs_conversion(uint32 arg_length,
 			      uint32 *offset)
 {
   *offset= 0;
-  if ((to_cs == &my_charset_bin) || 
+  if (!to_cs ||
+      (to_cs == &my_charset_bin) || 
       (to_cs == from_cs) ||
       my_charset_same(from_cs, to_cs) ||
       ((from_cs == &my_charset_bin) &&