Track the 'awaiter return' call stack use it to detect uncaught exceptions in async functions

runtime/vm/compiler.cc

Index: runtime/vm/compiler.cc
diff --git a/runtime/vm/compiler.cc b/runtime/vm/compiler.cc
index fae6a677ded1d9d3f0458006dd78f5b924861b16..940b18d6ed32f9a7c1d8513201e58fcaf6a9d8c4 100644
--- a/runtime/vm/compiler.cc
+++ b/runtime/vm/compiler.cc
@@ -543,6 +543,31 @@ void CompileParsedFunctionHelper::FinalizeCompilation(
       Code::Handle(Code::FinalizeCode(function, assembler, optimized()));
   code.set_is_optimized(optimized());
   code.set_owner(function);
+#if !defined(PRODUCT)

[rmacnak, 2017/02/23 17:50:56]

if (FLAG_support_debugger)

[Cutch, 2017/02/24 20:19:21]

Done.

+  ZoneGrowableArray<TokenPosition>* await_token_positions =
+      flow_graph->await_token_positions();
+  if (await_token_positions != NULL) {
+    Smi& token_pos_value = Smi::Handle(zone);
+    if (await_token_positions->length() > 0) {
+      const Array& await_to_token_map = Array::Handle(
+          zone, Array::New(await_token_positions->length(), Heap::kOld));
+      ASSERT(!await_to_token_map.IsNull());
+      for (intptr_t i = 0; i < await_token_positions->length(); i++) {
+        TokenPosition token_pos = await_token_positions->At(i).FromSynthetic();
+        if (!token_pos.IsReal()) {
+          // Some async machinary uses sentinel values. Map them to
+          // no source position.
+          token_pos_value = Smi::New(TokenPosition::kNoSourcePos);
+        } else {
+          token_pos_value = Smi::New(token_pos.value());
+        }
+        await_to_token_map.SetAt(i, token_pos_value);
+      }
+      code.SetAwaitTokenPositions(await_to_token_map);
+    }
+  }
+#endif  // !defined(PRODUCT)
+
   if (!function.IsOptimizable()) {
     // A function with huge unoptimized code can become non-optimizable
     // after generating unoptimized code.