MDEV-14041 Server crashes in String::length on queries with functions and ROLLUP

mysql-test/r/olap.result

@@ -800,5 +800,45 @@ latin1
 binary
 DROP TABLE t;
 #
+# MDEV-14041 Server crashes in String::length on queries with functions and ROLLUP
+#
+CREATE TABLE t1 (i INT);
+INSERT INTO t1 VALUES (1),(2);
+SELECT GET_LOCK( 'foo', 0 );
+GET_LOCK( 'foo', 0 )
+1
+SELECT HEX( RELEASE_LOCK( 'foo' ) ) AS f FROM t1 GROUP BY f WITH ROLLUP;
+f
+NULL
+1
+NULL
+DROP TABLE t1;
+CREATE TABLE t1 (i INT);
+INSERT INTO t1 VALUES (1),(2);
+SELECT i FROM t1 GROUP BY i WITH ROLLUP
+UNION ALL
+SELECT ELT( FOUND_ROWS(), 1 ) f FROM t1 GROUP BY f WITH ROLLUP;
+i
+1
+2
+NULL
+NULL
+NULL
+DROP TABLE t1;
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1),(2);
+SELECT a FROM t1 GROUP BY NULLIF( CONVERT('', DATE), '2015-10-15' ) WITH ROLLUP;
+a
+1
+1
+Warnings:
+Warning	1292	Incorrect datetime value: ''
+Warning	1292	Incorrect datetime value: ''
+Warning	1292	Incorrect datetime value: ''
+Warning	1292	Incorrect datetime value: ''
+Warning	1292	Incorrect datetime value: ''
+Warning	1292	Incorrect datetime value: ''
+DROP TABLE t1;
+#
 # End of 10.1 tests
 #

mysql-test/t/olap.test

@@ -439,6 +439,28 @@ SELECT CHARSET(d) AS f FROM t GROUP BY d WITH ROLLUP;
 DROP TABLE t;
 
 
+--echo #
+--echo # MDEV-14041 Server crashes in String::length on queries with functions and ROLLUP
+--echo #
+
+CREATE TABLE t1 (i INT);
+INSERT INTO t1 VALUES (1),(2);
+SELECT GET_LOCK( 'foo', 0 );
+SELECT HEX( RELEASE_LOCK( 'foo' ) ) AS f FROM t1 GROUP BY f WITH ROLLUP;
+DROP TABLE t1;
+
+CREATE TABLE t1 (i INT);
+INSERT INTO t1 VALUES (1),(2);
+SELECT i FROM t1 GROUP BY i WITH ROLLUP
+UNION ALL
+SELECT ELT( FOUND_ROWS(), 1 ) f FROM t1 GROUP BY f WITH ROLLUP;
+DROP TABLE t1;
+
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1),(2);
+SELECT a FROM t1 GROUP BY NULLIF( CONVERT('', DATE), '2015-10-15' ) WITH ROLLUP;
+DROP TABLE t1;
+
 --echo #
 --echo # End of 10.1 tests
 --echo #

sql/item.h

@@ -663,6 +663,45 @@ class Item: public Value_source,
   SEL_TREE *get_mm_tree_for_const(RANGE_OPT_PARAM *param);
 
   Field *create_tmp_field(bool group, TABLE *table, uint convert_int_length);
+  /* Helper methods, to get an Item value from another Item */
+  double val_real_from_item(Item *item)
+  {
+    DBUG_ASSERT(fixed == 1);
+    double value= item->val_real();
+    null_value= item->null_value;
+    return value;
+  }
+  longlong val_int_from_item(Item *item)
+  {
+    DBUG_ASSERT(fixed == 1);
+    longlong value= item->val_int();
+    null_value= item->null_value;
+    return value;
+  }
+  String *val_str_from_item(Item *item, String *str)
+  {
+    DBUG_ASSERT(fixed == 1);
+    String *res= item->val_str(str);
+    if (res)
+      res->set_charset(collation.collation);
+    if ((null_value= item->null_value))
+      res= NULL;
+    return res;
+  }
+  my_decimal *val_decimal_from_item(Item *item, my_decimal *decimal_value)
+  {
+    DBUG_ASSERT(fixed == 1);
+    my_decimal *value= item->val_decimal(decimal_value);
+    if ((null_value= item->null_value))
+      value= NULL;
+    return value;
+  }
+  bool get_date_from_item(Item *item, MYSQL_TIME *ltime, ulonglong fuzzydate)
+  {
+    bool rc= item->get_date(ltime, fuzzydate);
+    null_value= MY_TEST(rc || item->null_value);
+    return rc;
+  }
   /*
     This method is used if the item was not null but convertion to
     TIME/DATE/DATETIME failed. We return a zero date if allowed,

sql/item_func.h

@@ -1120,10 +1120,13 @@ class Item_func_rollup_const :public Item_func
     name= a->name;
     name_length= a->name_length;
   }
-  double val_real() { return args[0]->val_real(); }
-  longlong val_int() { return args[0]->val_int(); }
-  String *val_str(String *str) { return args[0]->val_str(str); }
-  my_decimal *val_decimal(my_decimal *dec) { return args[0]->val_decimal(dec); }
+  double val_real() { return val_real_from_item(args[0]); }
+  longlong val_int() { return val_int_from_item(args[0]); }
+  String *val_str(String *str) { return val_str_from_item(args[0], str); }
+  my_decimal *val_decimal(my_decimal *dec)
+    { return val_decimal_from_item(args[0], dec); }
+  bool get_date(MYSQL_TIME *ltime, ulonglong fuzzydate)
+    { return get_date_from_item(args[0], ltime, fuzzydate); }
   const char *func_name() const { return "rollup_const"; }
   bool const_item() const { return 0; }
   Item_result result_type() const { return args[0]->result_type(); }