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..1226c6921a807ed3be2d354d2a8f36d3e88fd333 100644
--- a/runtime/vm/malloc_hooks_test.cc
+++ b/runtime/vm/malloc_hooks_test.cc
@@ -6,11 +6,15 @@
 
 #if defined(DART_USE_TCMALLOC) && !defined(PRODUCT)
 
+#if defined(TARGET_OS_LINUX)
+#include <execinfo.h>
+#endif  // defined(TARGET_OS_LINUX)
+
 #include "platform/assert.h"
-#include "vm/class_finalizer.h"
 #include "vm/globals.h"
 #include "vm/malloc_hooks.h"
-#include "vm/symbols.h"
+#include "vm/profiler.h"
+#include "vm/profiler_service.h"
 #include "vm/unit_test.h"
 
 namespace dart {
@@ -56,7 +60,7 @@ UNIT_TEST_CASE(FreeUnseenMemoryMallocHookTest) {
   EXPECT_EQ(0L, MallocHooks::heap_allocated_memory_in_bytes());
 
   const intptr_t buffer_size = 10;
-  volatile char* buffer = new char[buffer_size];
+  char* buffer = new char[buffer_size];
   MallocHookTestBufferInitializer(buffer, buffer_size);
 
   EXPECT_EQ(1L, MallocHooks::allocation_count());
@@ -75,6 +79,91 @@ UNIT_TEST_CASE(FreeUnseenMemoryMallocHookTest) {
   MallocHooks::TearDown();
 }
 
+
+VM_UNIT_TEST_CASE(StackTraceMallocHookSimpleTest) {
+  MallocHooks::ResetStats();
+  ASSERT(MallocHooks::ProfilingEnabled());
+
+  char* var = static_cast<char*>(malloc(16 * sizeof(char)));
+  Sample* sample = MallocHooks::GetSample(var);
+  EXPECT(sample != NULL);
+
+  free(var);
+  sample = MallocHooks::GetSample(var);
+  EXPECT(sample == NULL);
+}
+
+
+ISOLATE_UNIT_TEST_CASE(StackTraceMallocHookSimpleJSONTest) {
+  MallocHooks::ResetStats();
+  ASSERT(MallocHooks::ProfilingEnabled());
+  ClearProfileVisitor cpv(Isolate::Current());
+  Profiler::sample_buffer()->VisitSamples(&cpv);
+
+  char* var = static_cast<char*>(malloc(16 * sizeof(char)));
+  JSONStream js;
+  ProfilerService::PrintNativeAllocationJSON(&js, Profile::kNoTags, -1, -1);
+  const char* json = js.ToCString();
+
+  // Check that all the stack frames from the current down to main are actually
+  // present in the profile. This is just a simple sanity check to make sure
+  // that the ProfileTrie has a representation of the stack trace collected when
+  // var is allocated. More intense testing is already done in profiler_test.cc.
+  EXPECT_SUBSTRING("\"dart::Dart_TestStackTraceMallocHookSimpleJSONTest()\"",
+                   json);
+  EXPECT_SUBSTRING("\"dart::TestCase::Run()\"", json);
+  EXPECT_SUBSTRING("\"dart::TestCaseBase::RunTest()\"", json);
+  EXPECT_SUBSTRING("\"main\"", json);
+
+  free(var);
+}
+
+
+#if defined(TARGET_OS_LINUX)

[Cutch, 2017/02/15 08:21:00]

Not sure if this OS_LINUX test is a good idea

[bkonyi, 2017/02/16 00:28:28]

After reading the comments below, I agree with you. There's too much platform
specific stuff that could go wrong in this test. I've removed the test and added
one that's less brittle.

+// 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(MallocHooks::ProfilingEnabled());
+
+  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]) + 10);

[Cutch, 2017/02/15 08:21:00]

this won't be the same across MIPS/ARM/ARM64/etc

+
+  Sample* sample = MallocHooks::GetSample(var);
+  ASSERT(sample != NULL);
+
+  while (sample != NULL) {
+    for (uintptr_t i = 0; i < 8; ++i) {

[Cutch, 2017/02/15 08:21:00]

Where did 8 come from?

+      // Cease comparisons after we pass the frame for main.
+      if (sample->At(i) == 0) {
+        break;
+      }
+      EXPECT_EQ(reinterpret_cast<uword>(stack_trace[i]), sample->At(i));
+    }
+
+    if (!sample->is_continuation_sample()) {
+      break;
+    }
+    sample = Profiler::sample_buffer()->At(sample->continuation_index());
+  }
+  free(var);
+}
+#endif  // defined(TARGET_OS_LINUX)
+
 };  // namespace dart
 
 #endif  // defined(DART_USE_TCMALLOC) && !defined(PRODUCT)