A fix (Bug #5291: float -> string, truncation, sometimes without warning).

mysql-test/r/type_float.result

@@ -137,6 +137,8 @@ t1	CREATE TABLE `t1` (
 drop table t1;
 create table t1 (c20 char);
 insert into t1 values (5000.0);
+Warnings:
+Warning	1265	Data truncated for column 'c20' at row 1
 drop table t1;
 create table t1 (f float(54));
 ERROR 42000: Incorrect column specifier for column 'f'

sql/field.cc

@@ -4297,7 +4297,7 @@ if (field_length < 32 && fabs(nr) < log_10[field_length]-1)
     like inserting 500.0 in char(1)
   */
   DBUG_ASSERT(field_length < 5 || length <= field_length+1);
-  return store((const char *)buff, min(length, field_length), charset());
+  return store((const char *) buff, length, charset());
 }