Updated MallocHooks to collect stack traces when memory is allocated.

runtime/vm/malloc_hooks_test.cc

Index: runtime/vm/malloc_hooks_test.cc
diff --git a/runtime/vm/malloc_hooks_test.cc b/runtime/vm/malloc_hooks_test.cc
index 5054a5047dd0f09c6f4de145c68b79e9b8676740..55f1752230cf1f7efb5c081bf07818530e4aea57 100644
--- a/runtime/vm/malloc_hooks_test.cc
+++ b/runtime/vm/malloc_hooks_test.cc
@@ -6,10 +6,14 @@
 
 #if defined(DART_USE_TCMALLOC) && !defined(PRODUCT)
 
+#include <execinfo.h>

[Cutch, 2017/02/08 00:28:54]

This is a cross platform test file. backtrace/execinfo.h is not portable.

[bkonyi, 2017/02/08 01:37:05]

This was more here for me to check that my implementation was correct. I'll
remove it and the below test before actually landing.

[zra, 2017/02/08 17:42:55]

Not sure how portable this is. Should this be gated on TARGET_OS_LINUX?

[bkonyi, 2017/02/09 21:22:46]

Yes, it probably should. However, DART_USE_TCMALLOC is only defined when
building for Linux since nothing else supports tcmalloc at this point, so this
should be fine for now at least.

+
 #include "platform/assert.h"
 #include "vm/class_finalizer.h"
 #include "vm/globals.h"
 #include "vm/malloc_hooks.h"
+#include "vm/native_symbol.h"
+#include "vm/profiler.h"
 #include "vm/symbols.h"
 #include "vm/unit_test.h"
 
@@ -75,6 +79,58 @@ UNIT_TEST_CASE(FreeUnseenMemoryMallocHookTest) {
   MallocHooks::TearDown();
 }
 
+// Helper used to add another frame to the stack before allocating.
+char* AllocationHelper(void* stack_trace[32]) {
+  backtrace(stack_trace, 32);
+  return static_cast<char*>(malloc(16 * sizeof(char)));
+}
+
+VM_UNIT_TEST_CASE(StackTraceMallocHookTest) {
+  MallocHooks::ResetStats();
+  ASSERT(OSThread::DoesCurrentThreadExist());
+
+  const intptr_t first_frame_count = 6;
+  void* stack_trace[32];
+
+  // Perform the memory allocation and grab the stack trace created by
+  // backtrace() for comparison purposes.
+  char* var = AllocationHelper(stack_trace);
+
+  // Update top pc of the stack trace to match the location that malloc was
+  // called in AllocationHelper. The rest of the pcs should match without any
+  // changes.
+  stack_trace[0] =
+      reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(stack_trace[0]) + 15);
+
+  Sample* sample = MallocHooks::GetSample(var);
+  ASSERT(sample != NULL);
+
+  intptr_t frame_count = 0;
+  while (sample != NULL) {

[Cutch, 2017/02/08 00:28:53]

This test might not be necessary. We have tests which verify the the stack
walkers work.

[bkonyi, 2017/02/08 01:37:05]

Makes sense. I'll remove it before actually landing.

+    for (uintptr_t i = 0; i < 8; ++i) {
+      // Cease comparisons after we pass the frame for main.
+      if (sample->At(i) == 0) {
+        break;
+      }
+
+      // The first 6 frames in the stack trace we generate are all from the
+      // memory allocation. The frame for AllocationHelper is the 7th element,
+      // so we skip checking all the frames before that.
+      if (frame_count >= first_frame_count) {
+        EXPECT_EQ(reinterpret_cast<uword>(
+                      stack_trace[frame_count - first_frame_count]),
+                  sample->At(i));
+      }
+      ++frame_count;
+    }
+
+    if (!sample->is_continuation_sample()) {
+      break;
+    }
+    sample = Profiler::sample_buffer()->At(sample->continuation_index());
+  }
+}
+
 };  // namespace dart
 
 #endif  // defined(DART_USE_TCMALLOC) && !defined(PRODUCT)