Fix capture of debug information when corruption is detected.

base/metrics/histogram_snapshot_manager.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_snapshot_manager.h"
 
 #include <memory>
 
 #include "base/debug/alias.h"
 #include "base/metrics/histogram_flattener.h"
@@ skipping 105 matching lines @@
   } else {
     // First time this histogram has been seen; datafill.
     sample_info->histogram = histogram;
   }
 
   // Crash if we detect that our histograms have been overwritten.  This may be
   // a fair distance from the memory smasher, but we hope to correlate these
   // crashes with other events, such as plugins, or usage patterns, etc.
   uint32_t corruption = histogram->FindCorruption(*samples);
   if (HistogramBase::BUCKET_ORDER_ERROR & corruption) {
+    // Extract fields useful during debug.
+    const BucketRanges* ranges =
+        static_cast<const Histogram*>(histogram)->bucket_ranges();
+    std::vector<HistogramBase::Sample> ranges_copy;
+    for (size_t i = 0; i < ranges->size(); ++i)
+      ranges_copy.push_back(ranges->range(i));
+    HistogramBase::Sample* ranges_ptr = &ranges_copy[0];
+    const char* histogram_name = histogram->histogram_name().c_str();
+    int32_t flags = histogram->flags();
     // The checksum should have caught this, so crash separately if it didn't.
     CHECK_NE(0U, HistogramBase::RANGE_CHECKSUM_ERROR & corruption);
     CHECK(false);  // Crash for the bucket order corruption.
     // Ensure that compiler keeps around pointers to |histogram| and its
     // internal |bucket_ranges_| for any minidumps.
-    base::debug::Alias(
-        static_cast<const Histogram*>(histogram)->bucket_ranges());
+    base::debug::Alias(&ranges_ptr);
+    base::debug::Alias(&histogram_name);
+    base::debug::Alias(&flags);
   }
   // Checksum corruption might not have caused order corruption.
   CHECK_EQ(0U, HistogramBase::RANGE_CHECKSUM_ERROR & corruption);
 
   // Note, at this point corruption can only be COUNT_HIGH_ERROR or
   // COUNT_LOW_ERROR and they never arise together, so we don't need to extract
   // bits from corruption.
   if (corruption) {
     DLOG(ERROR) << "Histogram: \"" << histogram->histogram_name()
                 << "\" has data corruption: " << corruption;
@@ skipping 28 matching lines @@
 
   histogram_flattener_->InconsistencyDetectedInLoggedCount(discrepancy);
   if (discrepancy > Histogram::kCommonRaceBasedCountMismatch) {
     // Fix logged_samples.
     logged_samples->Subtract(*logged_samples);
     logged_samples->Add(new_snapshot);
   }
 }
 
 }  // namespace base