Merge pull request swiftlang#9820 from felipepiovezan/felipe/fix_short_async_backtraces

[lldb][swift] Mark async unwinding plans as SourcedFromCompiler

Author: adrian-prantl

lldb/source/Plugins/LanguageRuntime/Swift/SwiftLanguageRuntime.cpp

@@ -2426,7 +2426,9 @@ SwiftLanguageRuntime::GetRuntimeUnwindPlan(ProcessSP process_sp,
   UnwindPlanSP plan = std::make_shared<UnwindPlan>(lldb::eRegisterKindDWARF);
   plan->AppendRow(row);
   plan->SetSourceName("Swift Transition-to-AsyncContext-Chain");
-  plan->SetSourcedFromCompiler(eLazyBoolNo);
+  // Make this plan more authoritative, so that the unwinding fallback
+  // mechanisms don't kick in and produce a physical backtrace instead.
+  plan->SetSourcedFromCompiler(eLazyBoolYes);
   plan->SetUnwindPlanValidAtAllInstructions(eLazyBoolYes);
   plan->SetUnwindPlanForSignalTrap(eLazyBoolYes);
   return plan;
@@ -2466,7 +2468,9 @@ UnwindPlanSP SwiftLanguageRuntime::GetFollowAsyncContextUnwindPlan(
   UnwindPlanSP plan = std::make_shared<UnwindPlan>(lldb::eRegisterKindDWARF);
   plan->AppendRow(row);
   plan->SetSourceName("Swift Following-AsyncContext-Chain");
-  plan->SetSourcedFromCompiler(eLazyBoolNo);
+  // Make this plan more authoritative, so that the unwinding fallback
+  // mechanisms don't kick in and produce a physical backtrace instead.
+  plan->SetSourcedFromCompiler(eLazyBoolYes);
   plan->SetUnwindPlanValidAtAllInstructions(eLazyBoolYes);
   plan->SetUnwindPlanForSignalTrap(eLazyBoolYes);
   behaves_like_zeroth_frame = true;

lldb/test/API/lang/swift/async/unwind/short_unwind/Makefile

@@ -0,0 +1,3 @@
+SWIFT_SOURCES := main.swift
+SWIFTFLAGS_EXTRAS := -parse-as-library
+include Makefile.rules

lldb/test/API/lang/swift/async/unwind/short_unwind/TestSwiftShortAsyncUnwind.py

@@ -0,0 +1,26 @@
+import lldb
+from lldbsuite.test.decorators import *
+import lldbsuite.test.lldbtest as lldbtest
+import lldbsuite.test.lldbutil as lldbutil
+
+
+class TestSwiftAsyncUnwind(lldbtest.TestBase):
+
+    mydir = lldbtest.TestBase.compute_mydir(__file__)
+
+    @swiftTest
+    @skipIf(oslist=["windows", "linux"])
+    def test(self):
+        """Test async unwinding with short backtraces work properly"""
+        self.build()
+        src = lldb.SBFileSpec("main.swift")
+        target, process, thread, bkpt = lldbutil.run_to_source_breakpoint(
+            self, "BREAK HERE", src
+        )
+
+        self.assertEqual(2, thread.GetNumFrames())
+        self.assertIn("work", thread.GetFrameAtIndex(0).GetFunctionName())
+        self.assertIn(
+            "await resume partial function for implicit closure",
+            thread.GetFrameAtIndex(1).GetFunctionName(),
+        )

lldb/test/API/lang/swift/async/unwind/short_unwind/main.swift

@@ -0,0 +1,15 @@
+func work() async -> Int {
+  try? await Task.sleep(for: .seconds(3))  // BREAK HERE
+  return 10
+}
+func foo_should_step_over() async -> Int {
+  async let an_array = [work(), work(), work()]
+  await an_array
+  return 10
+}
+
+@main struct Main {
+  static func main() async {
+    await foo_should_step_over()
+  }
+}