Return a named error in the result object of an expression with no result

Before we returned an error that was not exposed in the SB API and no useful
error message.  This change returns eExpressionProducedNoResult and an
appropriate error string.

<rdar://problem/44539514>

Differential Revision: https://reviews.llvm.org/D53309

llvm-svn: 344647

lldb/include/lldb/Expression/UserExpression.h

@@ -288,10 +288,6 @@ public:
            uint32_t line_offset = 0, std::string *fixed_expression = nullptr,
            lldb::ModuleSP *jit_module_sp_ptr = nullptr);
 
-  static const Status::ValueType kNoResult =
-      0x1001; ///< ValueObject::GetError() returns this if there is no result
-              /// from the expression.
-
   const char *GetFixedText() {
     if (m_fixed_text.empty())
       return nullptr;

lldb/include/lldb/lldb-enumerations.h

@@ -254,7 +254,8 @@ enum ExpressionResults {
   eExpressionHitBreakpoint,
   eExpressionTimedOut,
   eExpressionResultUnavailable,
-  eExpressionStoppedForDebug
+  eExpressionStoppedForDebug,
+  eExpressionProducedNoResult
 };
 
 enum SearchDepth {

lldb/packages/Python/lldbsuite/test/expression_command/no-result/Makefile

@@ -0,0 +1,6 @@
+LEVEL = ../../make
+
+C_SOURCES := main.c
+CFLAGS_EXTRAS += -std=c99
+
+include $(LEVEL)/Makefile.rules

lldb/packages/Python/lldbsuite/test/expression_command/no-result/TestNoResult.py

@@ -0,0 +1,45 @@
+"""
+Test that an expression that returns no result returns a sensible error.
+"""
+
+from __future__ import print_function
+
+
+import os
+import time
+import re
+import lldb
+import lldbsuite.test.lldbutil as lldbutil
+from lldbsuite.test.lldbtest import *
+
+
+class TestExprNoResult(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    # If your test case doesn't stress debug info, the
+    # set this to true.  That way it won't be run once for
+    # each debug info format.
+    NO_DEBUG_INFO_TESTCASE = True
+
+    def test_no_result(self):
+        """Run an expression that has no result, check the error."""
+        self.build()
+        self.main_source_file = lldb.SBFileSpec("main.c")
+        self.sample_test()
+
+    def setUp(self):
+        # Call super's setUp().
+        TestBase.setUp(self)
+
+    def sample_test(self):
+        (target, process, thread, bkpt) = lldbutil.run_to_source_breakpoint(self,
+                                   "Set a breakpoint here", self.main_source_file)
+
+        frame = thread.GetFrameAtIndex(0)
+        result = frame.EvaluateExpression("int $x = 10")
+        # No result expressions are considered to fail:
+        self.assertTrue(result.GetError().Fail(), "An expression with no result is a failure.")
+        # But the reason should be eExpressionProducedNoResult
+        self.assertEqual(result.GetError().GetError(), lldb.eExpressionProducedNoResult, 
+                         "But the right kind of failure")

lldb/packages/Python/lldbsuite/test/expression_command/no-result/main.c

@@ -0,0 +1,9 @@
+#include <stdio.h>
+
+int
+main()
+{
+  int test_var = 10;
+  printf ("Set a breakpoint here: %d.\n", test_var);
+  return 0;
+}

lldb/source/Commands/CommandObjectExpression.cpp

@@ -487,7 +487,7 @@ bool CommandObjectExpression::EvaluateExpression(llvm::StringRef expr,
         }
       } else {
         if (result_valobj_sp->GetError().GetError() ==
-            UserExpression::kNoResult) {
+            lldb::eExpressionProducedNoResult) {
           if (format != eFormatVoid &&
               m_interpreter.GetDebugger().GetNotifyVoid()) {
             error_stream->PutCString("(void)\n");

lldb/source/Expression/ExpressionSourceCode.cpp

@@ -256,7 +256,7 @@ bool ExpressionSourceCode::GetText(std::string &text,
     }
 
     ConstString object_name;
-    if (Language::LanguageIsCPlusPlus(frame->GetLanguage())) {
+    if (1 /* Language::LanguageIsCPlusPlus(frame->GetLanguage())*/) {
       if (target->GetInjectLocalVariables(&exe_ctx)) {
         lldb::VariableListSP var_list_sp =
             frame->GetInScopeVariableList(false, true);

lldb/source/Expression/REPL.cpp

@@ -325,7 +325,7 @@ void REPL::IOHandlerInputComplete(IOHandler &io_handler, std::string &code) {
           if (result_valobj_sp->GetError().Success()) {
             handled |= PrintOneVariable(debugger, output_sp, result_valobj_sp);
           } else if (result_valobj_sp->GetError().GetError() ==
-                     UserExpression::kNoResult) {
+                     lldb::eExpressionProducedNoResult) {
             if (format != lldb::eFormatVoid && debugger.GetNotifyVoid()) {
               error_sp->PutCString("(void)\n");
               handled = true;

lldb/source/Expression/UserExpression.cpp

@@ -151,6 +151,9 @@ lldb::ExpressionResults UserExpression::Evaluate(
                                       ? UserExpression::eResultTypeId
                                       : UserExpression::eResultTypeAny;
   lldb::ExpressionResults execution_results = lldb::eExpressionSetupError;
+  
+  static const char *no_result_error = "Expression completed successfully "
+                                       "but had no result";
 
   Target *target = exe_ctx.GetTargetPtr();
   if (!target) {
@@ -304,7 +307,8 @@ lldb::ExpressionResults UserExpression::Evaluate(
         error.SetExpressionError(lldb::eExpressionSetupError,
                                  "expression needed to run but couldn't");
     } else if (execution_policy == eExecutionPolicyTopLevel) {
-      error.SetError(UserExpression::kNoResult, lldb::eErrorTypeGeneric);
+      error.SetExpressionError(lldb::eExpressionProducedNoResult,
+                               no_result_error);
       return lldb::eExpressionCompleted;
     } else {
       if (options.InvokeCancelCallback(lldb::eExpressionEvaluationExecution)) {
@@ -349,7 +353,8 @@ lldb::ExpressionResults UserExpression::Evaluate(
             log->Printf("== [UserExpression::Evaluate] Execution completed "
                         "normally with no result ==");
 
-          error.SetError(UserExpression::kNoResult, lldb::eErrorTypeGeneric);
+          error.SetExpressionError(lldb::eExpressionProducedNoResult,
+                                   no_result_error);
         }
       }
     }

lldb/source/Plugins/LanguageRuntime/RenderScript/RenderScriptRuntime/RenderScriptRuntime.cpp

@@ -1758,7 +1758,7 @@ bool RenderScriptRuntime::EvalRSExpression(const char *expr,
   if (!expr_result->GetError().Success()) {
     Status err = expr_result->GetError();
     // Expression returned is void, so this is actually a success
-    if (err.GetError() == UserExpression::kNoResult) {
+    if (err.GetError() == lldb::eExpressionProducedNoResult) {
       if (log)
         log->Printf("%s - expression returned void.", __FUNCTION__);