Prevent calling internal metrics code with invalid values.

base/metrics/histogram.cc

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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.
 
 // Histogram is an object that aggregates statistics, and can summarize them in
 // various forms, including ASCII graphical, HTML, and numerically (as a
 // vector of numbers corresponding to each of the aggregating buckets).
 // See header file for details and examples.
 
 #include "base/metrics/histogram.h"
 
@@ skipping 75 matching lines @@
                                  size_t bucket_count,
                                  Flags flags) {
   Histogram* histogram(NULL);
 
   // Defensive code.
   if (minimum < 1)
     minimum = 1;
   if (maximum > kSampleType_MAX - 1)
     maximum = kSampleType_MAX - 1;
 
+  DCHECK_GT(maximum, minimum);
+  DCHECK_GT((Sample) bucket_count, 2);
+  DCHECK_LE((Sample) bucket_count, maximum - minimum + 2);
+
   if (!StatisticsRecorder::FindHistogram(name, &histogram)) {
     // Extra variable is not needed... but this keeps this section basically
     // identical to other derived classes in this file (and compiler will
     // optimize away the extra variable.
     // To avoid racy destruction at shutdown, the following will be leaked.
     Histogram* tentative_histogram =
         new Histogram(name, minimum, maximum, bucket_count);
     tentative_histogram->InitializeBucketRange();
     tentative_histogram->SetFlags(flags);
     histogram =
@@ skipping 702 matching lines @@
                                        Sample maximum,
                                        size_t bucket_count,
                                        Flags flags) {
   Histogram* histogram(NULL);
 
   if (minimum < 1)
     minimum = 1;
   if (maximum > kSampleType_MAX - 1)
     maximum = kSampleType_MAX - 1;
 
+  DCHECK_GT(maximum, minimum);
+  DCHECK_GT((Sample) bucket_count, 2);
+  DCHECK_LE((Sample) bucket_count, maximum - minimum + 2);
+
   if (!StatisticsRecorder::FindHistogram(name, &histogram)) {
     // To avoid racy destruction at shutdown, the following will be leaked.
     LinearHistogram* tentative_histogram =
         new LinearHistogram(name, minimum, maximum, bucket_count);
     tentative_histogram->InitializeBucketRange();
     tentative_histogram->SetFlags(flags);
     histogram =
         StatisticsRecorder::RegisterOrDeleteDuplicate(tentative_histogram);
   }
 
@@ skipping 487 matching lines @@
 
 // static
 StatisticsRecorder::HistogramMap* StatisticsRecorder::histograms_ = NULL;
 // static
 StatisticsRecorder::RangesMap* StatisticsRecorder::ranges_ = NULL;
 // static
 base::Lock* StatisticsRecorder::lock_ = NULL;
 // static
 bool StatisticsRecorder::dump_on_exit_ = false;
 }  // namespace base