Fix for bug #32558: group by null-returning expression with rollup causes crash

Problem: setting Item_func_rollup_const::null_value property to argument's null_value
before (without) the argument evaluation may result in a crash due to wrong null_value.

Fix: use is_null() to set Item_func_rollup_const::null_value instead as it evaluates
the argument if necessary and returns a proper value.


mysql-test/r/olap.result:
  Fix for bug #32558: group by null-returning expression with rollup causes crash
    - test result.
mysql-test/t/olap.test:
  Fix for bug #32558: group by null-returning expression with rollup causes crash
    - test case.
sql/item_func.h:
  Fix for bug #32558: group by null-returning expression with rollup causes crash
    - use args[0]->is_null() to obtain Item_func_rollup_const::null_value 
      instead of args[0]->null_value as it's not set in advance in case of 
      constant functions.

3 files changed, 18 insertions, 1 deletions

diff --git a/mysql-test/r/olap.result b/mysql-test/r/olap.result
index a1d66b11f58..ad04e7304c9 100644
--- a/mysql-test/r/olap.result
+++ b/mysql-test/r/olap.result
@@ -726,3 +726,11 @@ count(a)
 3
 drop table t1;
 ##############################################################
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES(0);
+SELECT 1 FROM t1 GROUP BY (DATE(NULL)) WITH ROLLUP;
+1
+1
+1
+DROP TABLE t1;
+End of 5.0 tests
diff --git a/mysql-test/t/olap.test b/mysql-test/t/olap.test
index 1ac99d9c39f..d1e40024733 100644
--- a/mysql-test/t/olap.test
+++ b/mysql-test/t/olap.test
@@ -367,3 +367,12 @@ select count(a) from t1 group by null with rollup;
 drop table t1;
 --echo ##############################################################
 
+#
+# Bug #32558: group by null-returning expression with rollup causes crash
+#
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES(0);
+SELECT 1 FROM t1 GROUP BY (DATE(NULL)) WITH ROLLUP;
+DROP TABLE t1;
+
+--echo End of 5.0 tests
diff --git a/sql/item_func.h b/sql/item_func.h
index a31294c0395..a5e162f344f 100644
--- a/sql/item_func.h
+++ b/sql/item_func.h
@@ -782,7 +782,7 @@ public:
     max_length= args[0]->max_length;
     decimals=args[0]->decimals; 
     /* The item could be a NULL constant. */
-    null_value= args[0]->null_value;
+    null_value= args[0]->is_null();
   }
 };