Bug#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."

1 files changed, 18 insertions, 0 deletions

diff --git a/mysql-test/t/func_time.test b/mysql-test/t/func_time.test
index b232fb14e1e..8a7f8792081 100644
--- a/mysql-test/t/func_time.test
+++ b/mysql-test/t/func_time.test
@@ -358,4 +358,22 @@ create table t1 select now() - now(), curtime() - curtime(),
 show create table t1;
 drop table t1;
 
+#
+# 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;
+
 # End of 4.1 tests