Fix undefined behavior in base/numerics

base/numerics/safe_numerics_unittest.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <limits>
 #include <type_traits>
 
@@ skipping 205 matching lines @@
   CheckedNumeric<Dst> checked_dst = 1;
   TEST_EXPECTED_VALUE(2, checked_dst += 1);
   checked_dst = 1;
   TEST_EXPECTED_VALUE(0, checked_dst -= 1);
   checked_dst = 1;
   TEST_EXPECTED_VALUE(1, checked_dst *= 1);
   checked_dst = 1;
   TEST_EXPECTED_VALUE(1, checked_dst /= 1);
 
   // Generic negation.
-  TEST_EXPECTED_VALUE(0, -CheckedNumeric<Dst>());
-  TEST_EXPECTED_VALUE(-1, -CheckedNumeric<Dst>(1));
-  TEST_EXPECTED_VALUE(1, -CheckedNumeric<Dst>(-1));
-  TEST_EXPECTED_VALUE(static_cast<Dst>(DstLimits::max() * -1),
-                      -CheckedNumeric<Dst>(DstLimits::max()));
+  if (DstLimits::is_signed) {
+    TEST_EXPECTED_VALUE(0, -CheckedNumeric<Dst>());
+    TEST_EXPECTED_VALUE(-1, -CheckedNumeric<Dst>(1));
+    TEST_EXPECTED_VALUE(1, -CheckedNumeric<Dst>(-1));
+    TEST_EXPECTED_VALUE(static_cast<Dst>(DstLimits::max() * -1),
+                        -CheckedNumeric<Dst>(DstLimits::max()));
+  }
 
   // Generic absolute value.
   TEST_EXPECTED_VALUE(0, CheckedNumeric<Dst>().Abs());
   TEST_EXPECTED_VALUE(1, CheckedNumeric<Dst>(1).Abs());
   TEST_EXPECTED_VALUE(DstLimits::max(),
                       CheckedNumeric<Dst>(DstLimits::max()).Abs());
 
   // Generic addition.
   TEST_EXPECTED_VALUE(1, (CheckedNumeric<Dst>() + 1));
   TEST_EXPECTED_VALUE(2, (CheckedNumeric<Dst>(1) + 1));
   TEST_EXPECTED_VALUE(0, (CheckedNumeric<Dst>(-1) + 1));
   TEST_EXPECTED_SUCCESS(CheckedNumeric<Dst>(DstLimits::min()) + 1);
   TEST_EXPECTED_FAILURE(CheckedNumeric<Dst>(DstLimits::max()) +
                         DstLimits::max());
 
   // Generic subtraction.
   TEST_EXPECTED_VALUE(-1, (CheckedNumeric<Dst>() - 1));
   TEST_EXPECTED_VALUE(0, (CheckedNumeric<Dst>(1) - 1));
   TEST_EXPECTED_VALUE(-2, (CheckedNumeric<Dst>(-1) - 1));
   TEST_EXPECTED_SUCCESS(CheckedNumeric<Dst>(DstLimits::max()) - 1);
 
   // Generic multiplication.
   TEST_EXPECTED_VALUE(0, (CheckedNumeric<Dst>() * 1));
   TEST_EXPECTED_VALUE(1, (CheckedNumeric<Dst>(1) * 1));
-  TEST_EXPECTED_VALUE(-2, (CheckedNumeric<Dst>(-1) * 2));
   TEST_EXPECTED_VALUE(0, (CheckedNumeric<Dst>(0) * 0));
   TEST_EXPECTED_VALUE(0, (CheckedNumeric<Dst>(-1) * 0));
   TEST_EXPECTED_VALUE(0, (CheckedNumeric<Dst>(0) * -1));
   TEST_EXPECTED_FAILURE(CheckedNumeric<Dst>(DstLimits::max()) *
                         DstLimits::max());
+  if (DstLimits::is_signed) {
+    TEST_EXPECTED_VALUE(-2, (CheckedNumeric<Dst>(-1) * 2));
+  }
 
   // Generic division.
   TEST_EXPECTED_VALUE(0, CheckedNumeric<Dst>() / 1);
   TEST_EXPECTED_VALUE(1, CheckedNumeric<Dst>(1) / 1);
   TEST_EXPECTED_VALUE(DstLimits::min() / 2,
                       CheckedNumeric<Dst>(DstLimits::min()) / 2);
   TEST_EXPECTED_VALUE(DstLimits::max() / 2,
                       CheckedNumeric<Dst>(DstLimits::max()) / 2);
 
   TestSpecializedArithmetic<Dst>(dst, line);
@@ skipping 480 matching lines @@
 
   CheckedNumeric<int> too_large = std::numeric_limits<int>::max();
   EXPECT_TRUE(too_large.IsValid());
   too_large += d;
   EXPECT_FALSE(too_large.IsValid());
   too_large -= d;
   EXPECT_FALSE(too_large.IsValid());
   too_large /= d;
   EXPECT_FALSE(too_large.IsValid());
 }