Return a NULL histogram pointer on construction error

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.
 
 // Test of Histogram class
 
 #include <climits>
 #include <algorithm>
 #include <vector>
 
@@ skipping 425 matching lines @@
   int range;
   EXPECT_TRUE(iter.ReadInt(&range));
   EXPECT_EQ(10, range);
   EXPECT_TRUE(iter.ReadInt(&range));
   EXPECT_EQ(100, range);
 
   // No more data in the pickle.
   EXPECT_FALSE(iter.SkipBytes(1));
 }
 
+TEST_F(HistogramTest, BadConstruction) {
+  HistogramBase* histogram = Histogram::FactoryGet(
+      "BadConstruction", 0, 100, 8,
+      HistogramBase::kNoFlags);
+  EXPECT_TRUE(
+      histogram->HasConstructionArguments(
+          1, 100, 8));
+  histogram->Add(10);
+
+  // Try to get the same histogram name with different arguments.
+  HistogramBase* dummy_histogram = Histogram::FactoryGet(
+      "BadConstruction", 0, 100, 7,
+      HistogramBase::kNoFlags);
+  dummy_histogram->Add(80);
+  dummy_histogram = Histogram::FactoryGet(
+      "BadConstruction", 0, 99, 8,
+      HistogramBase::kNoFlags);
+  dummy_histogram->Add(80);
+
+  scoped_ptr<HistogramSamples> samples = histogram->SnapshotSamples();
+  EXPECT_EQ(1, samples->TotalCount());
+  EXPECT_EQ(1, samples->GetCount(10));
+  EXPECT_EQ(0, samples->GetCount(80));
+
+  HistogramBase* linear_histogram = LinearHistogram::FactoryGet(
+      "BadConstructionLinear", 0, 100, 8,
+      HistogramBase::kNoFlags);
+  EXPECT_TRUE(
+      linear_histogram->HasConstructionArguments(
+          1, 100, 8));
+  linear_histogram->Add(10);
+
+  // Try to get the same histogram name with different arguments.
+  dummy_histogram = LinearHistogram::FactoryGet(
+      "BadConstructionLinear", 0, 100, 7,
+      HistogramBase::kNoFlags);
+  dummy_histogram->Add(80);
+  dummy_histogram = LinearHistogram::FactoryGet(
+      "BadConstructionLinear", 10, 100, 8,
+      HistogramBase::kNoFlags);
+  dummy_histogram->Add(80);
+
+  scoped_ptr<HistogramSamples> l_samples = linear_histogram->SnapshotSamples();
+  EXPECT_EQ(1, l_samples->TotalCount());
+  EXPECT_EQ(1, l_samples->GetCount(10));
+  EXPECT_EQ(0, l_samples->GetCount(80));
+}
+
 #if GTEST_HAS_DEATH_TEST
 // For Histogram, LinearHistogram and CustomHistogram, the minimum for a
 // declared range is 1, while the maximum is (HistogramBase::kSampleType_MAX -
 // 1). But we accept ranges exceeding those limits, and silently clamped to
 // those limits. This is for backwards compatibility.
 TEST(HistogramDeathTest, BadRangesTest) {
   HistogramBase* histogram = Histogram::FactoryGet(
       "BadRanges", 0, HistogramBase::kSampleType_MAX, 8,
       HistogramBase::kNoFlags);
   EXPECT_TRUE(
@@ skipping 28 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