Cleaner fall-back stack capture for --enable-heap-profiling=native.

base/trace_event/heap_profiler_allocation_context_tracker.cc

 // Copyright 2015 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/trace_event/heap_profiler_allocation_context_tracker.h"
 
 #include <algorithm>
 #include <iterator>
 
 #include "base/atomicops.h"
@@ skipping 186 matching lines @@
               StackFrame::FromTraceEventName(stack_frame.trace_event_name);
         }
         break;
       }
     case CaptureMode::NATIVE_STACK:
       {
         // Backtrace contract requires us to return bottom frames, i.e.
         // from main() and up. Stack unwinding produces top frames, i.e.
         // from this point and up until main(). We request many frames to
         // make sure we reach main(), and then copy bottom portion of them.
+#if !defined(OS_NACL)  // We don't build base/debug/stack_trace.cc for NaCl.
+#if BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS)
         const void* frames[128];
         static_assert(arraysize(frames) >= Backtrace::kMaxFrameCount,
                       "not requesting enough frames to fill Backtrace");
-#if BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS) && !defined(OS_NACL)
         size_t frame_count = debug::TraceStackFramePointers(
-            frames,
-            arraysize(frames),
-            1 /* exclude this function from the trace */ );
-#else
-        size_t frame_count = 0;
-        NOTREACHED();
-#endif
+            frames, arraysize(frames),
+            1 /* exclude this function from the trace */);
+#else   // BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS)
+        // Fall-back to capturing the stack with base::debug::StackTrace,
+        // which is likely slower, but more reliable.
+        base::debug::StackTrace stack_trace(Backtrace::kMaxFrameCount);
+        size_t frame_count = 0u;
+        const void* const* frames = stack_trace.Addresses(&frame_count);
+#endif  // BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS)
 
         // Copy frames backwards
         size_t backtrace_capacity = backtrace_end - backtrace;
         int32_t top_frame_index = (backtrace_capacity >= frame_count)
                                       ? 0
                                       : frame_count - backtrace_capacity;
         for (int32_t i = frame_count - 1; i >= top_frame_index; --i) {
           const void* frame = frames[i];
           *backtrace++ = StackFrame::FromProgramCounter(frame);
         }
+#endif  // !defined(OS_NACL)
         break;
       }
   }
 
   ctx->backtrace.frame_count = backtrace - std::begin(ctx->backtrace.frames);
 
   // TODO(ssid): Fix crbug.com/594803 to add file name as 3rd dimension
   // (component name) in the heap profiler and not piggy back on the type name.
   if (!task_contexts_.empty()) {
     ctx->type_name = task_contexts_.back();
   } else if (!pseudo_stack_.empty()) {
     // If task context was unavailable, then the category names are taken from
     // trace events.
     ctx->type_name = pseudo_stack_.back().trace_event_category;
   } else {
     ctx->type_name = nullptr;
   }
 
   return true;
 }
 
 }  // namespace trace_event
 }  // namespace base