Fix overflow bug in histogram sample data structures

base/metrics/histogram_unittest.cc

Index: base/metrics/histogram_unittest.cc
diff --git a/base/metrics/histogram_unittest.cc b/base/metrics/histogram_unittest.cc
index 2fadc304415e4fc96b5478bdad712cc2e2a30e21..e03f5aaf95ec3b7567dce74ed6d68aacd8bf3f2a 100644
--- a/base/metrics/histogram_unittest.cc
+++ b/base/metrics/histogram_unittest.cc
@@ -245,7 +245,7 @@ TEST_F(HistogramTest, AddCountTest) {
   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));
@@ -253,12 +253,37 @@ TEST_F(HistogramTest, AddCountTest) {
   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;
@@ -358,7 +383,7 @@ 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));