[lldb-dap] Add: show return value on step out (#106907)

https://github.com/user-attachments/assets/cff48c6f-37ae-4f72-b881-3eff4178fb3c

lldb/test/API/tools/lldb-dap/variables/TestDAP_variables.py

@@ -341,9 +341,9 @@ class TestDAP_variables(lldbdap_testcase.DAPTestCaseBase):
 
         verify_locals["argc"]["equals"]["value"] = "123"
         verify_locals["pt"]["children"]["x"]["equals"]["value"] = "111"
-        verify_locals["x @ main.cpp:17"] = {"equals": {"type": "int", "value": "89"}}
-        verify_locals["x @ main.cpp:19"] = {"equals": {"type": "int", "value": "42"}}
-        verify_locals["x @ main.cpp:21"] = {"equals": {"type": "int", "value": "72"}}
+        verify_locals["x @ main.cpp:19"] = {"equals": {"type": "int", "value": "89"}}
+        verify_locals["x @ main.cpp:21"] = {"equals": {"type": "int", "value": "42"}}
+        verify_locals["x @ main.cpp:23"] = {"equals": {"type": "int", "value": "72"}}
 
         self.verify_variables(verify_locals, self.dap_server.get_local_variables())
 
@@ -353,32 +353,32 @@ class TestDAP_variables(lldbdap_testcase.DAPTestCaseBase):
             self.dap_server.request_setVariable(1, "x @ main.cpp:0", 9)["success"]
         )
 
-        self.assertTrue(
-            self.dap_server.request_setVariable(1, "x @ main.cpp:17", 17)["success"]
-        )
         self.assertTrue(
             self.dap_server.request_setVariable(1, "x @ main.cpp:19", 19)["success"]
         )
         self.assertTrue(
             self.dap_server.request_setVariable(1, "x @ main.cpp:21", 21)["success"]
         )
+        self.assertTrue(
+            self.dap_server.request_setVariable(1, "x @ main.cpp:23", 23)["success"]
+        )
 
         # The following should have no effect
         self.assertFalse(
-            self.dap_server.request_setVariable(1, "x @ main.cpp:21", "invalid")[
+            self.dap_server.request_setVariable(1, "x @ main.cpp:23", "invalid")[
                 "success"
             ]
         )
 
-        verify_locals["x @ main.cpp:17"]["equals"]["value"] = "17"
         verify_locals["x @ main.cpp:19"]["equals"]["value"] = "19"
         verify_locals["x @ main.cpp:21"]["equals"]["value"] = "21"
+        verify_locals["x @ main.cpp:23"]["equals"]["value"] = "23"
 
         self.verify_variables(verify_locals, self.dap_server.get_local_variables())
 
         # The plain x variable shold refer to the innermost x
         self.assertTrue(self.dap_server.request_setVariable(1, "x", 22)["success"])
-        verify_locals["x @ main.cpp:21"]["equals"]["value"] = "22"
+        verify_locals["x @ main.cpp:23"]["equals"]["value"] = "22"
 
         self.verify_variables(verify_locals, self.dap_server.get_local_variables())
 
@@ -394,10 +394,10 @@ class TestDAP_variables(lldbdap_testcase.DAPTestCaseBase):
         locals = self.dap_server.get_local_variables()
         names = [var["name"] for var in locals]
         # The first shadowed x shouldn't have a suffix anymore
-        verify_locals["x"] = {"equals": {"type": "int", "value": "17"}}
-        self.assertNotIn("x @ main.cpp:17", names)
+        verify_locals["x"] = {"equals": {"type": "int", "value": "19"}}
         self.assertNotIn("x @ main.cpp:19", names)
         self.assertNotIn("x @ main.cpp:21", names)
+        self.assertNotIn("x @ main.cpp:23", names)
 
         self.verify_variables(verify_locals, locals)
 
@@ -663,6 +663,54 @@ class TestDAP_variables(lldbdap_testcase.DAPTestCaseBase):
         ]["variables"]
         self.verify_variables(verify_children, children)
 
+    def test_return_variables(self):
+        """
+        Test the stepping out of a function with return value show the variable correctly.
+        """
+        program = self.getBuildArtifact("a.out")
+        self.build_and_launch(program)
+
+        return_name = "(Return Value)"
+        verify_locals = {
+            return_name: {"equals": {"type": "int", "value": "300"}},
+            "argc": {},
+            "argv": {},
+            "pt": {},
+            "x": {},
+            "return_result": {"equals": {"type": "int"}},
+        }
+
+        function_name = "test_return_variable"
+        breakpoint_ids = self.set_function_breakpoints([function_name])
+
+        self.assertEqual(len(breakpoint_ids), 1)
+        self.continue_to_breakpoints(breakpoint_ids)
+
+        threads = self.dap_server.get_threads()
+        for thread in threads:
+            if thread.get("reason") == "breakpoint":
+                thread_id = thread["id"]
+
+                self.stepOut(threadId=thread_id)
+
+                local_variables = self.dap_server.get_local_variables()
+                varref_dict = {}
+
+                # `verify_variable` function only checks if the local variables
+                # are in the `verify_dict` passed  this will cause this test to pass
+                # even if there is no return value.
+                local_variable_names = [
+                    variable["name"] for variable in local_variables
+                ]
+                self.assertIn(
+                    return_name,
+                    local_variable_names,
+                    "return variable is not in local variables",
+                )
+
+                self.verify_variables(verify_locals, local_variables, varref_dict)
+                break
+
     @skipIfWindows
     def test_indexedVariables(self):
         self.do_test_indexedVariables(enableSyntheticChildDebugging=False)

lldb/test/API/tools/lldb-dap/variables/children/TestDAP_variables_children.py

@@ -40,3 +40,59 @@ class TestDAP_variables_children(lldbdap_testcase.DAPTestCaseBase):
                 "`script formatter.num_children_calls", context="repl"
             )["body"]["result"],
         )
+
+    @skipIf(archs=["arm64"])
+    def test_return_variable_with_children(self):
+        """
+        Test the stepping out of a function with return value show the children correctly
+        """
+        program = self.getBuildArtifact("a.out")
+        self.build_and_launch(program)
+
+        function_name = "test_return_variable_with_children"
+        breakpoint_ids = self.set_function_breakpoints([function_name])
+
+        self.assertEqual(len(breakpoint_ids), 1)
+        self.continue_to_breakpoints(breakpoint_ids)
+
+        threads = self.dap_server.get_threads()
+        for thread in threads:
+            if thread.get("reason") == "breakpoint":
+                thread_id = thread.get("id")
+                self.assertIsNot(thread_id, None)
+
+                self.stepOut(threadId=thread_id)
+
+                local_variables = self.dap_server.get_local_variables()
+
+                # verify has return variable as local
+                result_variable = list(
+                    filter(
+                        lambda val: val.get("name") == "(Return Value)", local_variables
+                    )
+                )
+                self.assertEqual(len(result_variable), 1)
+                result_variable = result_variable[0]
+
+                result_var_ref = result_variable.get("variablesReference")
+                self.assertIsNot(result_var_ref, None, "There is no result value")
+
+                result_value = self.dap_server.request_variables(result_var_ref)
+                result_children = result_value["body"]["variables"]
+                self.assertNotEqual(
+                    result_children, None, "The result does not have children"
+                )
+
+                verify_children = {"buffer": '"hello world!"', "x": "10", "y": "20"}
+                for child in result_children:
+                    actual_name = child["name"]
+                    actual_value = child["value"]
+                    verify_value = verify_children.get(actual_name)
+                    self.assertNotEqual(verify_value, None)
+                    self.assertEqual(
+                        actual_value,
+                        verify_value,
+                        "Expected child value does not match",
+                    )
+
+                break

lldb/test/API/tools/lldb-dap/variables/children/main.cpp

@@ -1,8 +1,20 @@
 struct Indexed {};
 struct NotIndexed {};
 
+#define BUFFER_SIZE 16
+struct NonPrimitive {
+  char buffer[BUFFER_SIZE];
+  int x;
+  long y;
+};
+
+NonPrimitive test_return_variable_with_children() {
+  return NonPrimitive{"hello world!", 10, 20};
+}
+
 int main() {
   Indexed indexed;
   NotIndexed not_indexed;
+  NonPrimitive non_primitive_result = test_return_variable_with_children();
   return 0; // break here
 }

lldb/test/API/tools/lldb-dap/variables/main.cpp

@@ -9,6 +9,8 @@ struct PointType {
 int g_global = 123;
 static int s_global = 234;
 int test_indexedVariables();
+int test_return_variable();
+
 int main(int argc, char const *argv[]) {
   static float s_local = 2.25;
   PointType pt = {11, 22, {0}};
@@ -22,6 +24,9 @@ int main(int argc, char const *argv[]) {
       s_global = x; // breakpoint 2
     }
   }
+  {
+    int return_result = test_return_variable();
+  }
   return test_indexedVariables(); // breakpoint 3
 }
 
@@ -34,3 +39,7 @@ int test_indexedVariables() {
   large_vector.assign(200, 0);
   return 0; // breakpoint 4
 }
+
+int test_return_variable() {
+  return 300; // breakpoint 5
+}

lldb/tools/lldb-dap/Handler/VariablesRequestHandler.cpp

@@ -164,6 +164,29 @@ void VariablesRequestHandler::operator()(
       variable_name_counts[GetNonNullVariableName(variable)]++;
     }
 
+    // Show return value if there is any ( in the local top frame )
+    if (variablesReference == VARREF_LOCALS) {
+      auto process = dap.target.GetProcess();
+      auto selected_thread = process.GetSelectedThread();
+      lldb::SBValue stop_return_value = selected_thread.GetStopReturnValue();
+
+      if (stop_return_value.IsValid() &&
+          (selected_thread.GetSelectedFrame().GetFrameID() == 0)) {
+        auto renamed_return_value = stop_return_value.Clone("(Return Value)");
+        int64_t return_var_ref = 0;
+
+        if (stop_return_value.MightHaveChildren() ||
+            stop_return_value.IsSynthetic()) {
+          return_var_ref = dap.variables.InsertVariable(stop_return_value,
+                                                        /*is_permanent=*/false);
+        }
+        variables.emplace_back(
+            CreateVariable(renamed_return_value, return_var_ref, hex,
+                           dap.enable_auto_variable_summaries,
+                           dap.enable_synthetic_child_debugging, false));
+      }
+    }
+
     // Now we construct the result with unique display variable names
     for (auto i = start_idx; i < end_idx; ++i) {
       lldb::SBValue variable = top_scope->GetValueAtIndex(i);

llvm/docs/ReleaseNotes.md

@@ -168,6 +168,7 @@ Changes to LLDB
 ### Changes to lldb-dap
 
 * Breakpoints can now be set for specific columns within a line.
+* Function return value is now displayed on step-out.
 
 Changes to BOLT
 ---------------------------------