Fix false-positive ASAN detection with the stack profiler on win64

base/profiler/native_stack_sampler_win.cc

Index: base/profiler/native_stack_sampler_win.cc
diff --git a/base/profiler/native_stack_sampler_win.cc b/base/profiler/native_stack_sampler_win.cc
index 063374f19d5b1edfd7d758d98e4047a1b8d67bd6..acf9717c7c9b82ad98f62545ae530d3390df920a 100644
--- a/base/profiler/native_stack_sampler_win.cc
+++ b/base/profiler/native_stack_sampler_win.cc
@@ -319,7 +319,7 @@ void SuspendThreadAndRecordStack(
     void* stack_copy_buffer,
     size_t stack_copy_buffer_size,
     std::vector<RecordedFrame>* stack,
-    NativeStackSamplerTestDelegate* test_delegate) {
+    NativeStackSamplerTestDelegate* test_delegate) NO_SANITIZE("address") {
   DCHECK(stack->empty());
 
   CONTEXT thread_context = {0};
@@ -353,8 +353,17 @@ void SuspendThreadAndRecordStack(
     if (PointsToGuardPage(bottom))
       return;
 
+#if defined(ADDRESS_SANITIZER)

[Mike Wittman, 2016/11/17 01:57:54]

nit: can we encapsulate this ifdef in its own function? This is the most
important block of code in the profiler and having the ifdef here detracts from
readability.

[etienneb, 2016/11/17 19:29:54]

Done.

+    // The following loop is an inlined version of memcpy. The code must be
+    // inlined to avoid instrumentation when using ASAN (memory sanitizer). The
+    // stack profiler is generating false positive when walking the stack.
+    for (size_t pos = 0; pos < top - bottom; ++pos)
+      reinterpret_cast<char*>(stack_copy_buffer)[pos] =
+          reinterpret_cast<const char*>(bottom)[pos];
+#else
     std::memcpy(stack_copy_buffer, reinterpret_cast<const void*>(bottom),
                 top - bottom);
+#endif
   }
 
   if (test_delegate)
@@ -385,7 +394,7 @@ class NativeStackSamplerWin : public NativeStackSampler {
     // reserved stack size is 1 MB and Chrome Windows threads currently always
     // use the default, but this allows for expansion if it occurs. The size
     // beyond the actual stack size consists of unallocated virtual memory pages
-    // so carries little cost (just a bit of wated address space).
+    // so carries little cost (just a bit of wasted address space).
     kStackCopyBufferSize = 2 * 1024 * 1024
   };