Fix some lurking div by 0s in safe_math_impl.h

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 102 matching lines @@
   TEST_EXPECTED_VALUE(-1, CheckedNumeric<Dst>(-1) % 2);
   TEST_EXPECTED_FAILURE(CheckedNumeric<Dst>(-1) % -2);
   TEST_EXPECTED_VALUE(0, CheckedNumeric<Dst>(DstLimits::min()) % 2);
   TEST_EXPECTED_VALUE(1, CheckedNumeric<Dst>(DstLimits::max()) % 2);
   // Test all the different modulus combinations.
   TEST_EXPECTED_VALUE(0, CheckedNumeric<Dst>(1) % CheckedNumeric<Dst>(1));
   TEST_EXPECTED_VALUE(0, 1 % CheckedNumeric<Dst>(1));
   TEST_EXPECTED_VALUE(0, CheckedNumeric<Dst>(1) % 1);
   CheckedNumeric<Dst> checked_dst = 1;
   TEST_EXPECTED_VALUE(0, checked_dst %= 1);
+  // Test that div by 0 is avoided but returns invalid result.
+  TEST_EXPECTED_FAILURE(CheckedNumeric<Dst>(1) % 0);
 }
 
 // Unsigned integer arithmetic.
 template <typename Dst>
 static void TestSpecializedArithmetic(
     const char* dst,
     int line,
     typename std::enable_if<numeric_limits<Dst>::is_integer &&
                                 !numeric_limits<Dst>::is_signed,
                             int>::type = 0) {
@@ skipping 15 matching lines @@
   TEST_EXPECTED_VALUE(0, CheckedNumeric<Dst>(1) % 1);
   TEST_EXPECTED_VALUE(1, CheckedNumeric<Dst>(1) % 2);
   TEST_EXPECTED_VALUE(0, CheckedNumeric<Dst>(DstLimits::min()) % 2);
   TEST_EXPECTED_VALUE(1, CheckedNumeric<Dst>(DstLimits::max()) % 2);
   // Test all the different modulus combinations.
   TEST_EXPECTED_VALUE(0, CheckedNumeric<Dst>(1) % CheckedNumeric<Dst>(1));
   TEST_EXPECTED_VALUE(0, 1 % CheckedNumeric<Dst>(1));
   TEST_EXPECTED_VALUE(0, CheckedNumeric<Dst>(1) % 1);
   CheckedNumeric<Dst> checked_dst = 1;
   TEST_EXPECTED_VALUE(0, checked_dst %= 1);
+  // Test that div by 0 is avoided but returns invalid result.
+  TEST_EXPECTED_FAILURE(CheckedNumeric<Dst>(1) % 0);
 }
 
 // Floating point arithmetic.
 template <typename Dst>
 void TestSpecializedArithmetic(
     const char* dst,
     int line,
     typename std::enable_if<numeric_limits<Dst>::is_iec559, int>::type = 0) {
   typedef numeric_limits<Dst> DstLimits;
   TEST_EXPECTED_SUCCESS(-CheckedNumeric<Dst>(DstLimits::min()));
@@ skipping 587 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());
 }