[lldb-dap] Add: Show return values

Explicitly check for the return value variable

Author: da-viper

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

@@ -670,8 +670,9 @@ def test_return_variables(self):
         program = self.getBuildArtifact("a.out")
         self.build_and_launch(program)
 
+        return_name = "(Return Value)"
         verify_locals = {
-            "(Return Value)": {"equals": {"type": "int", "value": "300"}},
+            return_name: {"equals": {"type": "int", "value": "300"}},
             "argc": {},
             "argv": {},
             "pt": {},
@@ -694,6 +695,19 @@ def test_return_variables(self):
 
                 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
 

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);