Code review request for 6371401: java.math.BigInteger.shift(Integer.MIN_VALUE) throws StackOverflowError

[Joseph D. Darcy]

Hello.

Please review this simple improvement in handling an exceptional 
condition in BigInteger.  A stack overflow on an argument of 
BigInteger.shitf{Left, Right}(Integer.MIN_VALUE) is handled as an 
explicit ArithmeticException, the same exception used throughout 
BigInteger for other invalid inputs.

Patch below; webrev at
http://cr.openjdk.java.net/~darcy/6371401.0/

Thanks,

-Joe

--- old/src/share/classes/java/math/BigInteger.java    2009-10-19 
17:37:36.000000000 -0700
+++ new/src/share/classes/java/math/BigInteger.java    2009-10-19 
17:37:35.000000000 -0700
@@ -2051,6 +2051,8 @@
      *
      * @param  n shift distance, in bits.
      * @return {@code this << n}
+     * @throws ArithmeticException if the shift distance is {@code
+     *         Integer.MIN_VALUE}.
      * @see #shiftRight
      */
     public BigInteger shiftLeft(int n) {
@@ -2058,8 +2060,13 @@
             return ZERO;
         if (n==0)
             return this;
-        if (n<0)
-            return shiftRight(-n);
+        if (n<0) {
+            if (n == Integer.MIN_VALUE) {
+                throw new ArithmeticException("Shift distance of 
Integer.MIN_VALUE not supported.");
+            } else {
+                return shiftRight(-n);
+            }
+        }
 
         int nInts = n >>> 5;
         int nBits = n & 0x1f;
@@ -2097,13 +2104,20 @@
      *
      * @param  n shift distance, in bits.
      * @return {@code this >> n}
+     * @throws ArithmeticException if the shift distance is {@code
+     *         Integer.MIN_VALUE}.
      * @see #shiftLeft
      */
     public BigInteger shiftRight(int n) {
         if (n==0)
             return this;
-        if (n<0)
-            return shiftLeft(-n);
+        if (n<0) {
+            if (n == Integer.MIN_VALUE) {
+                throw new ArithmeticException("Shift distance of 
Integer.MIN_VALUE not supported.");
+            } else {
+                return shiftLeft(-n);
+            }
+        }
 
         int nInts = n >>> 5;
         int nBits = n & 0x1f;
--- /dev/null    2009-07-06 20:02:10.000000000 -0700
+++ new/test/java/math/BigInteger/ExtremeShiftingTests.java    
2009-10-19 17:37:36.000000000 -0700
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2009 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License 
version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+/*
+ * @test
+ * @bug 6371401
+ * @summary Tests of shiftLeft and shiftRight on Integer.MIN_VALUE
+ * @author Joseph D. Darcy
+ */
+import java.math.*;
+import static java.math.BigInteger.*;
+
+public class ExtremeShiftingTests {
+    public static void main(String... args) {
+        try {
+            ONE.shiftLeft(Integer.MIN_VALUE);
+            throw new RuntimeException("Should not reach here.");
+        } catch (ArithmeticException ae) {
+            ; // Expected
+        }
+
+        try {
+            ONE.shiftRight(Integer.MIN_VALUE);
+            throw new RuntimeException("Should not reach here.");
+        } catch (ArithmeticException ae) {
+            ; // Expected
+        }
+    }
+}