Fix overflow bug in histogram sample data structures

base/metrics/histogram_unittest.cc

 // Copyright (c) 2012 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 "base/metrics/histogram.h"
 
 #include <limits.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 227 matching lines @@
 // Test the AddCount function.
 TEST_F(HistogramTest, AddCountTest) {
   const size_t kBucketCount = 50;
   Histogram* histogram = static_cast<Histogram*>(
       Histogram::FactoryGet("AddCountHistogram", 10, 100, kBucketCount,
                             HistogramBase::kNoFlags));
 
   histogram->AddCount(20, 15);
   histogram->AddCount(30, 14);
 
-  scoped_ptr<SampleVector> samples = histogram->SnapshotSampleVector();
+  scoped_ptr<HistogramSamples> samples = histogram->SnapshotSamples();
   EXPECT_EQ(29, samples->TotalCount());
   EXPECT_EQ(15, samples->GetCount(20));
   EXPECT_EQ(14, samples->GetCount(30));
 
   histogram->AddCount(20, 25);
   histogram->AddCount(30, 24);
 
-  scoped_ptr<SampleVector> samples2 = histogram->SnapshotSampleVector();
+  scoped_ptr<HistogramSamples> samples2 = histogram->SnapshotSamples();
   EXPECT_EQ(78, samples2->TotalCount());
   EXPECT_EQ(40, samples2->GetCount(20));
   EXPECT_EQ(38, samples2->GetCount(30));
 }
 
+// Test the AddCount function with large sample values.
+TEST_F(HistogramTest, AddCountLargeTest) {

[Alexei Svitkine (slow), 2016/01/22 22:33:03]

Nit: Maybe AddCount_LargeValuesDontOverflow

And same for the others. (No need to have the word "Test" in the name of the
unit test - even though I know the previous tests do this. Also, no need for the
comment above it.

[bcf, 2016/01/22 22:46:14]

Done.

+  const size_t kBucketCount = 50;
+  Histogram* histogram = static_cast<Histogram*>(
+      Histogram::FactoryGet("AddCountHistogram", 10, 1000000000, kBucketCount,
+                            HistogramBase::kNoFlags));
+
+  histogram->AddCount(200000000, 15);
+  histogram->AddCount(300000000, 14);
+
+  scoped_ptr<HistogramSamples> samples = histogram->SnapshotSamples();
+  EXPECT_EQ(29, samples->TotalCount());
+  EXPECT_EQ(15, samples->GetCount(200000000));
+  EXPECT_EQ(14, samples->GetCount(300000000));
+
+  histogram->AddCount(200000000, 25);
+  histogram->AddCount(300000000, 24);
+
+  scoped_ptr<HistogramSamples> samples2 = histogram->SnapshotSamples();
+  EXPECT_EQ(78, samples2->TotalCount());
+  EXPECT_EQ(40, samples2->GetCount(200000000));
+  EXPECT_EQ(38, samples2->GetCount(300000000));
+  EXPECT_EQ(19400000000LL, samples2->sum());
+}
+
 // Make sure histogram handles out-of-bounds data gracefully.
 TEST_F(HistogramTest, BoundsTest) {
   const size_t kBucketCount = 50;
   Histogram* histogram = static_cast<Histogram*>(
       Histogram::FactoryGet("Bounded", 10, 100, kBucketCount,
                             HistogramBase::kNoFlags));
 
   // Put two samples "out of bounds" above and below.
   histogram->Add(5);
   histogram->Add(-50);
@@ skipping 79 matching lines @@
   // But we can't spot a corruption if it is compensated for.
   snapshot->counts_[1] += 100;
   EXPECT_EQ(HistogramBase::NO_INCONSISTENCIES,
             histogram->FindCorruption(*snapshot));
 }
 
 TEST_F(HistogramTest, CorruptBucketBounds) {
   Histogram* histogram = static_cast<Histogram*>(
       Histogram::FactoryGet("Histogram", 1, 64, 8, HistogramBase::kNoFlags));
 
-  scoped_ptr<SampleVector> snapshot = histogram->SnapshotSampleVector();
+  scoped_ptr<HistogramSamples> snapshot = histogram->SnapshotSamples();
   EXPECT_EQ(HistogramBase::NO_INCONSISTENCIES,
             histogram->FindCorruption(*snapshot));
 
   BucketRanges* bucket_ranges =
       const_cast<BucketRanges*>(histogram->bucket_ranges());
   HistogramBase::Sample tmp = bucket_ranges->range(1);
   bucket_ranges->set_range(1, bucket_ranges->range(2));
   bucket_ranges->set_range(2, tmp);
   EXPECT_EQ(
       HistogramBase::BUCKET_ORDER_ERROR | HistogramBase::RANGE_CHECKSUM_ERROR,
@@ skipping 159 matching lines @@
   // CustomHistogram needs at least 1 valid range.
   custom_ranges.clear();
   custom_ranges.push_back(0);
   EXPECT_DEATH(CustomHistogram::FactoryGet("BadRangesCustom3", custom_ranges,
                                            HistogramBase::kNoFlags),
                "");
 }
 #endif
 
 }  // namespace base