Fix CAST(1.0e+300 TO SIGNED). (Bug #13344)

mysql-test/r/cast.result:
  Update results
mysql-test/t/cast.test:
  Add regression test
sql/item.h:
  Cap Item_real::val_int() to LONGLONG_MIN and LONGLONG_MAX.

mysql-test/r/cast.result

@@ -252,3 +252,6 @@ cast(repeat('1',20) as signed)
 -7335632962598440505
 Warnings:
 Warning	1105	Cast to signed converted positive out-of-range integer to it's negative complement
+select cast(1.0e+300 as signed int);
+cast(1.0e+300 as signed int)
+9223372036854775807

mysql-test/t/cast.test

@@ -143,4 +143,9 @@ select cast(concat('184467440','73709551615') as signed);
 select cast(repeat('1',20) as unsigned);
 select cast(repeat('1',20) as signed);
 
+#
+# Bug #13344: cast of large decimal to signed int not handled correctly
+#
+select cast(1.0e+300 as signed int);
+
 # End of 4.1 tests

sql/item.h

@@ -703,6 +703,14 @@ public:
   longlong val_int()
   {
     DBUG_ASSERT(fixed == 1);
+    if (value <= (double) LONGLONG_MIN)
+    {
+       return LONGLONG_MIN;
+    }
+    else if (value >= (double) (ulonglong) LONGLONG_MAX)
+    {
+      return LONGLONG_MAX;
+    }
     return (longlong) (value+(value > 0 ? 0.5 : -0.5));
   }
   String *val_str(String*);