Fix for bug when zeros are to be prepended to decimal field

mysql-test/r/type_decimal.result

@@ -363,3 +363,9 @@ CREATE TABLE t1 (a_dec DECIMAL(-2,1));
 Too big column length for column 'a_dec' (max = 255). Use BLOB instead
 CREATE TABLE t1 (a_dec DECIMAL(-1,1));
 Too big column length for column 'a_dec' (max = 255). Use BLOB instead
+create table t1(a decimal(10,4));
+insert into t1 values ("+0000100000000");
+select * from t1;
+a
+9999999.9999
+drop table t1;

mysql-test/t/type_decimal.test

@@ -240,3 +240,9 @@ CREATE TABLE t1 (a_dec DECIMAL(-1,0));
 CREATE TABLE t1 (a_dec DECIMAL(-2,1));
 --error 1074
 CREATE TABLE t1 (a_dec DECIMAL(-1,1));
+
+#  Zero prepend overflow bug
+create table t1(a decimal(10,4));
+insert into t1 values ("+0000100000000");
+select * from t1;
+drop table t1;

sql/field.cc

@@ -632,7 +632,7 @@ void Field_decimal::store(const char *from,uint len)
   if (zerofill)
   {
     left_wall=to-1;
-    while (pos != left_wall)			// Fill with zeros
+    while (pos > left_wall)			// Fill with zeros
       *pos--='0';
   }
   else
@@ -640,7 +640,7 @@ void Field_decimal::store(const char *from,uint len)
     left_wall=to+(sign_char != 0)-1;
     if (!expo_sign_char)	// If exponent was specified, ignore prezeros
     {
-      for (;pos != left_wall && pre_zeros_from !=pre_zeros_end;
+      for (;pos > left_wall && pre_zeros_from !=pre_zeros_end;
 	   pre_zeros_from++)
 	*pos--= '0';
     }