Track async causal stack traces

runtime/lib/stacktrace.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "lib/stacktrace.h"
 #include "vm/bootstrap_natives.h"
+#include "vm/debugger.h"
 #include "vm/exceptions.h"
+#include "vm/native_entry.h"
 #include "vm/object_store.h"
 #include "vm/runtime_entry.h"
 #include "vm/stack_frame.h"
+#include "vm/stack_trace.h"
 
 namespace dart {
 
-static void IterateFrames(const GrowableObjectArray& code_list,
-                          const GrowableObjectArray& pc_offset_list,
-                          int skip_frames) {
+DECLARE_FLAG(bool, show_invisible_frames);
+DEFINE_FLAG(int,
+            max_async_stack_trace_frames,
+            96,
+            "Maximum number of asynchronous stack traces frames remembered in "
+            "an asynchronous function activation");
+
+static RawStackTrace* CurrentSyncStackTrace(Thread* thread, Isolate* isolate) {

[rmacnak, 2017/01/26 18:05:57]

isolate parameter not used

[siva, 2017/01/26 19:26:23]

Thread is available here, you could extract the zone and use it for all the
handle creations here and in other functions in this file.

[Cutch, 2017/01/31 23:45:30]

Done.

[Cutch, 2017/01/31 23:45:30]

Done.

+  const Function& null_function = Function::Handle();
+  const intptr_t skip_frames = 1;

[siva, 2017/01/26 19:26:22]

maybe document which frame is skipped

[Cutch, 2017/01/31 23:45:30]

Done.

+
+  // Determine how big the stack trace is.
+  const intptr_t stack_trace_length =
+      StackTraceUtils::CountFrames(skip_frames, null_function);
+
+  // Allocate once.
+  const Array& code_array = Array::Handle(Array::New(stack_trace_length));
+  const Array& pc_offset_array = Array::Handle(Array::New(stack_trace_length));
+
+  // Collect the frames.
+  const intptr_t collected_frames_count = StackTraceUtils::CollectFrames(
+      code_array, pc_offset_array, 0, stack_trace_length, skip_frames);
+
+  ASSERT(collected_frames_count == stack_trace_length);
+
+  return StackTrace::New(code_array, pc_offset_array);

[siva, 2017/01/26 19:26:23]

Do you think there stack traces are going to be living for a while (i.e will
survive new gen GCs) could consider allocating in old space if so.

Not sure about it though.

[Cutch, 2017/01/31 23:45:30]

Acknowledged.

+}
+
+
+static RawStackTrace* CurrentStackTrace(
+    Thread* thread,
+    Isolate* isolate,

[rmacnak, 2017/01/26 18:05:57]

isolate parameter not used

[Cutch, 2017/01/31 23:45:30]

Done.

+    bool for_async_function,
+    intptr_t skip_frames = 1,
+    bool sane_async_stacks = FLAG_sane_async_stacks) {
+  if (!sane_async_stacks) {
+    // Return the synchronous stack trace.
+    return CurrentSyncStackTrace(thread, isolate);
+  }
+
+  Code& code = Code::Handle();

[rmacnak, 2017/01/26 18:05:57]

Handle(zone)

[Cutch, 2017/01/31 23:45:30]

Done (here and elsewhere).

+  Smi& offset = Smi::Handle();
+  Function& async_function = Function::Handle();
+  Array& async_code_array = Array::Handle();
+  Array& async_pc_offset_array = Array::Handle();
+
+  const intptr_t async_stack_trace_length =
+      StackTraceUtils::ExtractAsyncStackTraceInfo(
+          thread, &async_function, &async_code_array, &async_pc_offset_array);
+
+  // Determine the size of the stack trace.
+  const intptr_t extra_frames = for_async_function ? 1 : 0;
+  const intptr_t synchronous_stack_trace_length =
+      StackTraceUtils::CountFrames(skip_frames, async_function);
+
+  const intptr_t complete_length = async_stack_trace_length +
+                                   synchronous_stack_trace_length +
+                                   extra_frames;  // For the asynchronous gap.
+
+  // We only truncate the stack trace when collecting for asynchronous
+  // stack traces.
+  const bool truncate_stack_trace =
+      for_async_function || (async_stack_trace_length > 0);
+
+  const intptr_t capacity =
+      (!truncate_stack_trace ||
+       (FLAG_max_async_stack_trace_frames > complete_length))
+          ? complete_length
+          : FLAG_max_async_stack_trace_frames;
+
+  // Allocate memory for the stack trace.
+  const Array& code_array = Array::Handle(Array::New(capacity));
+  const Array& pc_offset_array = Array::Handle(Array::New(capacity));
+
+  intptr_t write_cursor = 0;
+  if (for_async_function) {
+    // Place the asynchronous gap marker at the top of the stack trace.
+    code = StubCode::AsynchronousGapMarker_entry()->code();
+    ASSERT(!code.IsNull());
+    offset = Smi::New(0);
+    code_array.SetAt(write_cursor, code);
+    pc_offset_array.SetAt(write_cursor, offset);
+    write_cursor++;
+  }
+
+  const intptr_t sync_frames_to_collect =
+      (synchronous_stack_trace_length < (capacity - write_cursor))
+          ? synchronous_stack_trace_length
+          : capacity - write_cursor;
+
+  // Append the synchronous stack trace.
+  const intptr_t collected_frames_count =
+      StackTraceUtils::CollectFrames(code_array, pc_offset_array, write_cursor,
+                                     sync_frames_to_collect, skip_frames);
+
+  write_cursor += collected_frames_count;
+
+  // Append the asynchronous stack trace.
+  if (async_stack_trace_length > 0) {
+    ASSERT(!async_code_array.IsNull());
+    ASSERT(!async_pc_offset_array.IsNull());
+    for (intptr_t i = 0; i < async_stack_trace_length; i++) {
+      if (write_cursor == capacity) {
+        break;
+      }
+      if (async_code_array.At(i) == Code::null()) {
+        break;
+      }
+      code = Code::RawCast(async_code_array.At(i));

[rmacnak, 2017/01/26 18:05:57]

code ^= async_code_array.At(i)

[Cutch, 2017/01/31 23:45:30]

Done.

+      offset = Smi::RawCast(async_pc_offset_array.At(i));

[rmacnak, 2017/01/26 18:05:57]

offset ^=

[Cutch, 2017/01/31 23:45:30]

Done.

+      code_array.SetAt(write_cursor, code);
+      pc_offset_array.SetAt(write_cursor, offset);
+      write_cursor++;
+    }
+  }
+
+  return StackTrace::New(code_array, pc_offset_array);
+}
+
+
+RawStackTrace* GetStackTraceForException() {
+  Thread* thread = Thread::Current();
+  Isolate* isolate = thread->isolate();
+  return CurrentStackTrace(thread, isolate, false, 0);
+}
+
+
+DEFINE_NATIVE_ENTRY(StackTrace_current, 0) {
+  return CurrentStackTrace(thread, isolate, false);
+}
+
+
+DEFINE_NATIVE_ENTRY(StackTrace_forAsyncMethod, 0) {
+  return CurrentStackTrace(thread, isolate, true);
+}
+
+
+DEFINE_NATIVE_ENTRY(StackTrace_clearAsyncThreadStackTrace, 0) {
+  thread->clear_async_stack_trace();
+  return Object::null();
+}
+
+
+DEFINE_NATIVE_ENTRY(StackTrace_setAsyncThreadStackTrace, 1) {
+  GET_NON_NULL_NATIVE_ARGUMENT(StackTrace, stack_trace,
+                               arguments->NativeArgAt(0));
+  thread->set_async_stack_trace(stack_trace);
+  return Object::null();
+}
+
+
+static void AppendFrames(const GrowableObjectArray& code_list,
+                         const GrowableObjectArray& pc_offset_list,
+                         int skip_frames) {
   StackFrameIterator frames(StackFrameIterator::kDontValidateFrames);
   StackFrame* frame = frames.NextFrame();
   ASSERT(frame != NULL);  // We expect to find a dart invocation frame.
   Code& code = Code::Handle();
   Smi& offset = Smi::Handle();
   while (frame != NULL) {
     if (frame->IsDartFrame()) {
       if (skip_frames > 0) {
         skip_frames--;
       } else {
         code = frame->LookupDartCode();
         offset = Smi::New(frame->pc() - code.PayloadStart());
         code_list.Add(code);
         pc_offset_list.Add(offset);
       }
     }
     frame = frames.NextFrame();
   }
 }
 
+
 // Creates a StackTrace object from the current stack.
 //
 // Skips the first skip_frames Dart frames.
 const StackTrace& GetCurrentStackTrace(int skip_frames) {
   const GrowableObjectArray& code_list =
       GrowableObjectArray::Handle(GrowableObjectArray::New());
   const GrowableObjectArray& pc_offset_list =
       GrowableObjectArray::Handle(GrowableObjectArray::New());
-  IterateFrames(code_list, pc_offset_list, skip_frames);
+  AppendFrames(code_list, pc_offset_list, skip_frames);
   const Array& code_array = Array::Handle(Array::MakeArray(code_list));
   const Array& pc_offset_array =
       Array::Handle(Array::MakeArray(pc_offset_list));
   const StackTrace& stacktrace =
       StackTrace::Handle(StackTrace::New(code_array, pc_offset_array));
   return stacktrace;
 }
 
+
 // An utility method for convenient printing of dart stack traces when
 // inside 'gdb'. Note: This function will only work when there is a
 // valid exit frame information. It will not work when a breakpoint is
 // set in dart code and control is got inside 'gdb' without going through
 // the runtime or native transition stub.
 void _printCurrentStackTrace() {
   const StackTrace& stacktrace = GetCurrentStackTrace(0);
   OS::PrintErr("=== Current Trace:\n%s===\n", stacktrace.ToCString());
 }
 
+
 // Like _printCurrentStackTrace, but works in a NoSafepointScope.
 void _printCurrentStackTraceNoSafepoint() {
   StackFrameIterator frames(StackFrameIterator::kDontValidateFrames);
   StackFrame* frame = frames.NextFrame();
   while (frame != NULL) {
-    OS::Print("%s\n", frame->ToCString());
+    OS::PrintErr("%s\n", frame->ToCString());
     frame = frames.NextFrame();
   }
 }
 
-DEFINE_NATIVE_ENTRY(StackTrace_current, 0) {
-  const StackTrace& stacktrace = GetCurrentStackTrace(1);
-  return stacktrace.raw();
-}
-
 }  // namespace dart