A fix (bug #9837: round(1, 6) delivers wrong value in create table context).

mysql-test/r/func_math.result

+drop table if exists t1;
 select floor(5.5),floor(-5.5);
 floor(5.5)	floor(-5.5)
 5	-6
@@ -126,3 +127,13 @@ Warnings:
 Note	1003	select degrees(pi()) AS `degrees(pi())`,radians(360) AS `radians(360)`
 select rand(rand);
 ERROR 42S22: Unknown column 'rand' in 'field list'
+create table t1 select round(1, 6);
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `round(1, 6)` double(7,6) NOT NULL default '0.000000'
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+select * from t1;
+round(1, 6)
+1.000000
+drop table t1;

mysql-test/t/func_math.test

@@ -2,6 +2,10 @@
 # Test of math functions
 #
 
+--disable_warnings                                                              
+drop table if exists t1;                                                        
+--enable_warnings                                                               
+
 select floor(5.5),floor(-5.5);
 explain extended select floor(5.5),floor(-5.5);
 select ceiling(5.5),ceiling(-5.5);
@@ -58,3 +62,12 @@ explain extended select degrees(pi()),radians(360);
 
 --error 1054
 select rand(rand);
+
+#
+# Bug #9837: problem with round()
+#
+
+create table t1 select round(1, 6);
+show create table t1;
+select * from t1;
+drop table t1;

sql/item_func.cc

@@ -1072,6 +1072,8 @@ void Item_func_round::fix_length_and_dec()
       decimals=0;
     else
       decimals=min(tmp,NOT_FIXED_DEC);
+    if ((tmp= decimals - args[0]->decimals) > 0)
+      max_length+= tmp;
   }
 }