Bug#11765923 58937: MANY VALGRIND ERRORS AFTER GROUPING BY RESULT OF DECIMAL COLUMN FUNCTION

Bug#11764671  57533: UNINITIALISED VALUES IN COPY_AND_CONVERT (SQL_STRING.CC) WITH CERTAIN CHA
When ROUND evaluates decimal result it uses Item::decimal
value as fraction value for the result. In some cases
Item::decimal is greater than real result fraction value
and uninitialised memory of result(decimal) buffer can be
used in further calculations. Issue is introduced by
Bug33143 fix. The fix is to remove erroneous assignment.

mysql-test/r/func_math.result

@@ -518,4 +518,26 @@ CREATE TABLE t1 SELECT CEIL(LINESTRINGFROMWKB(1) DIV NULL);
 DROP TABLE t1;
 CREATE TABLE t1 SELECT FLOOR(LINESTRINGFROMWKB(1) DIV NULL);
 DROP TABLE t1;
+#
+# Bug#11765923  58937: MANY VALGRIND ERRORS AFTER GROUPING BY RESULT OF DECIMAL COLUMN FUNCTION
+#
+CREATE TABLE t1(f1 DECIMAL(22,1));
+INSERT INTO t1 VALUES (0),(1);
+SELECT ROUND(f1, f1) FROM t1;
+ROUND(f1, f1)
+0.0
+1.0
+SELECT ROUND(f1, f1) FROM t1 GROUP BY 1;
+ROUND(f1, f1)
+0.0
+1.0
+DROP TABLE t1;
+#
+# Bug#11764671  57533: UNINITIALISED VALUES IN COPY_AND_CONVERT (SQL_STRING.CC) WITH CERTAIN CHA
+#
+SELECT ROUND(LEAST(15, -4939092, 0.2704), STDDEV('a'));
+ROUND(LEAST(15, -4939092, 0.2704), STDDEV('a'))
+-4939092.0000
+Warnings:
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
 End of 5.1 tests

mysql-test/t/func_math.test

@@ -333,4 +333,20 @@ DROP TABLE t1;
 CREATE TABLE t1 SELECT FLOOR(LINESTRINGFROMWKB(1) DIV NULL);
 DROP TABLE t1;
 
+--echo #
+--echo # Bug#11765923  58937: MANY VALGRIND ERRORS AFTER GROUPING BY RESULT OF DECIMAL COLUMN FUNCTION
+--echo #
+
+CREATE TABLE t1(f1 DECIMAL(22,1));
+INSERT INTO t1 VALUES (0),(1);
+SELECT ROUND(f1, f1) FROM t1;
+SELECT ROUND(f1, f1) FROM t1 GROUP BY 1;
+DROP TABLE t1;
+
+--echo #
+--echo # Bug#11764671  57533: UNINITIALISED VALUES IN COPY_AND_CONVERT (SQL_STRING.CC) WITH CERTAIN CHA
+--echo #
+
+SELECT ROUND(LEAST(15, -4939092, 0.2704), STDDEV('a'));
+
 --echo End of 5.1 tests

sql/item_func.cc

@@ -2122,10 +2122,7 @@ my_decimal *Item_func_round::decimal_op(my_decimal *decimal_value)
   if (!(null_value= (args[0]->null_value || args[1]->null_value ||
                      my_decimal_round(E_DEC_FATAL_ERROR, value, (int) dec,
                                       truncate, decimal_value) > 1))) 
-  {
-    decimal_value->frac= decimals;
     return decimal_value;
-  }
   return 0;
 }