commit 2a39621c1343f4c29c69647d151441d171fb3e7b
Author: Alexander Barkov <bar@mariadb.org>
Date:   Tue Apr 19 16:56:41 2016 +0400

    MDEV-9745 Crash with CASE WHEN TRUE THEN COALESCE(CAST(NULL AS UNSIGNED)) ELSE 4 END

diff --git a/mysql-test/r/case.result b/mysql-test/r/case.result
index 3852da5..274d5da 100644
--- a/mysql-test/r/case.result
+++ b/mysql-test/r/case.result
@@ -231,3 +231,16 @@ case t1.f1 when '00:00:00' then 1 end
 1
 NULL
 drop table t1;
+#
+# MDEV-9745 Crash with CASE WHEN TRUE THEN COALESCE(CAST(NULL AS UNSIGNED)) ELSE 4 END
+#
+CREATE TABLE t1 SELECT CASE WHEN TRUE THEN COALESCE(CAST(NULL AS UNSIGNED)) ELSE 4 END AS a;
+DESCRIBE t1;
+Field	Type	Null	Key	Default	Extra
+a	decimal(1,0)	YES		NULL	
+DROP TABLE t1;
+CREATE TABLE t1 SELECT CASE WHEN TRUE THEN COALESCE(CAST(NULL AS UNSIGNED)) ELSE 40 END AS a;
+DESCRIBE t1;
+Field	Type	Null	Key	Default	Extra
+a	decimal(2,0)	YES		NULL	
+DROP TABLE t1;
diff --git a/mysql-test/t/case.test b/mysql-test/t/case.test
index f536f55..c127836 100644
--- a/mysql-test/t/case.test
+++ b/mysql-test/t/case.test
@@ -193,3 +193,12 @@ insert t1 values ('00:00:00'),('00:01:00');
 select case t1.f1 when '00:00:00' then 1 end from t1;
 drop table t1;
 
+--echo #
+--echo # MDEV-9745 Crash with CASE WHEN TRUE THEN COALESCE(CAST(NULL AS UNSIGNED)) ELSE 4 END
+--echo #
+CREATE TABLE t1 SELECT CASE WHEN TRUE THEN COALESCE(CAST(NULL AS UNSIGNED)) ELSE 4 END AS a;
+DESCRIBE t1;
+DROP TABLE t1;
+CREATE TABLE t1 SELECT CASE WHEN TRUE THEN COALESCE(CAST(NULL AS UNSIGNED)) ELSE 40 END AS a;
+DESCRIBE t1;
+DROP TABLE t1;
diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index 81688f3..08281c5 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -3101,17 +3101,7 @@ void Item_func_case::fix_length_and_dec()
   }
   else
   {
-    collation.set_numeric();
-    max_length=0;
-    decimals=0;
-    unsigned_flag= TRUE;
-    for (uint i= 0; i < ncases; i+= 2)
-      agg_num_lengths(args[i + 1]);
-    if (else_expr_num != -1) 
-      agg_num_lengths(args[else_expr_num]);
-    max_length= my_decimal_precision_to_length_no_truncation(max_length +
-                                                             decimals, decimals,
-                                               unsigned_flag);
+    fix_attributes(agg, nagg);
   }
   
   /*
@@ -3342,19 +3332,32 @@ void Item_func_coalesce::fix_length_and_dec()
 {
   cached_field_type= agg_field_type(args, arg_count);
   agg_result_type(&cached_result_type, args, arg_count);
+  fix_attributes(args, arg_count);
+}
+
+
+/**
+  Rename this to Item_hybrid_func::fix_attributes() when mering to 10.1
+*/
+void Item_func_hybrid_result_type::fix_attributes(Item **items, uint nitems)
+{
   switch (cached_result_type) {
   case STRING_RESULT:
-    if (count_string_result_length(cached_field_type, args, arg_count))
+    if (count_string_result_length(field_type(),
+                                   items, nitems))
       return;          
     break;
   case DECIMAL_RESULT:
-    count_decimal_length();
+    collation.set_numeric();
+    count_decimal_length(items, nitems);
     break;
   case REAL_RESULT:
-    count_real_length();
+    collation.set_numeric();
+    count_real_length(items, nitems);
     break;
   case INT_RESULT:
-    count_only_length(args, arg_count);
+    collation.set_numeric();
+    count_only_length(items, nitems);
     decimals= 0;
     break;
   case ROW_RESULT:
diff --git a/sql/item_func.cc b/sql/item_func.cc
index 252ca9e..bd6553d 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -641,16 +641,16 @@ void Item_func::count_datetime_length(Item **item, uint nitems)
   result length/precision depends on argument ones.
 */
 
-void Item_func::count_decimal_length()
+void Item_func::count_decimal_length(Item **item, uint nitems)
 {
   int max_int_part= 0;
   decimals= 0;
   unsigned_flag= 1;
-  for (uint i=0 ; i < arg_count ; i++)
+  for (uint i=0 ; i < nitems ; i++)
   {
-    set_if_bigger(decimals, args[i]->decimals);
-    set_if_bigger(max_int_part, args[i]->decimal_int_part());
-    set_if_smaller(unsigned_flag, args[i]->unsigned_flag);
+    set_if_bigger(decimals, item[i]->decimals);
+    set_if_bigger(max_int_part, item[i]->decimal_int_part());
+    set_if_smaller(unsigned_flag, item[i]->unsigned_flag);
   }
   int precision= min(max_int_part + decimals, DECIMAL_MAX_PRECISION);
   fix_char_length(my_decimal_precision_to_length_no_truncation(precision,
@@ -681,19 +681,19 @@ void Item_func::count_only_length(Item **item, uint nitems)
   result length/precision depends on argument ones.
 */
 
-void Item_func::count_real_length()
+void Item_func::count_real_length(Item **item, uint nitems)
 {
   uint32 length= 0;
   decimals= 0;
   max_length= 0;
-  for (uint i=0 ; i < arg_count ; i++)
+  for (uint i=0 ; i < nitems ; i++)
   {
     if (decimals != NOT_FIXED_DEC)
     {
-      set_if_bigger(decimals, args[i]->decimals);
-      set_if_bigger(length, (args[i]->max_length - args[i]->decimals));
+      set_if_bigger(decimals, item[i]->decimals);
+      set_if_bigger(length, (item[i]->max_length - item[i]->decimals));
     }
-    set_if_bigger(max_length, args[i]->max_length);
+    set_if_bigger(max_length, item[i]->max_length);
   }
   if (decimals != NOT_FIXED_DEC)
   {
@@ -811,7 +811,7 @@ void Item_num_op::fix_length_and_dec(void)
   if (r0 == REAL_RESULT || r1 == REAL_RESULT ||
       r0 == STRING_RESULT || r1 ==STRING_RESULT)
   {
-    count_real_length();
+    count_real_length(args, arg_count);
     max_length= float_length(decimals);
     cached_result_type= REAL_RESULT;
   }
diff --git a/sql/item_func.h b/sql/item_func.h
index 33fa49f..9776ec0 100644
--- a/sql/item_func.h
+++ b/sql/item_func.h
@@ -39,6 +39,13 @@ class Item_func :public Item_result_field
     0 means get this number from first argument
   */
   uint allowed_arg_cols;
+
+  void count_only_length(Item **item, uint nitems);
+  void count_real_length(Item **item, uint nitems);
+  void count_decimal_length(Item **item, uint nitems);
+  void count_datetime_length(Item **item, uint nitems);
+  bool count_string_result_length(enum_field_types field_type,
+                                  Item **item, uint nitems);
 public:
   uint arg_count;
   table_map used_tables_cache, not_null_tables_cache;
@@ -146,16 +153,10 @@ class Item_func :public Item_result_field
   virtual void print(String *str, enum_query_type query_type);
   void print_op(String *str, enum_query_type query_type);
   void print_args(String *str, uint from, enum_query_type query_type);
-  void count_only_length(Item **item, uint nitems);
-  void count_real_length();
-  void count_decimal_length();
   inline bool get_arg0_date(MYSQL_TIME *ltime, ulonglong fuzzy_date)
   {
     return (null_value=args[0]->get_date(ltime, fuzzy_date));
   }
-  void count_datetime_length(Item **item, uint nitems);
-  bool count_string_result_length(enum_field_types field_type,
-                                  Item **item, uint nitems);
   inline bool get_arg0_time(MYSQL_TIME *ltime)
   {
     null_value= args[0]->get_time(ltime);
@@ -436,7 +437,7 @@ class Item_func_hybrid_result_type: public Item_func
   }
 protected:
   Item_result cached_result_type;
-
+  void fix_attributes(Item **item, uint nitems);
 public:
   Item_func_hybrid_result_type() :Item_func(), cached_result_type(REAL_RESULT)
   { collation.set_numeric(); }
