Don't produce a dynamic value if there was an error creating it.

We used to make a dynamic value that "pretended to be its parent"
but that's hard for some of the more complex ValueObject types, and
it's better in this case just to return no dynamic value.

Differential Revision: https://reviews.llvm.org/D145629

lldb/source/Core/ValueObject.cpp

@@ -1859,7 +1859,7 @@ ValueObjectSP ValueObject::GetDynamicValue(DynamicValueType use_dynamic) {
   if (!IsDynamic() && m_dynamic_value == nullptr) {
     CalculateDynamicValue(use_dynamic);
   }
-  if (m_dynamic_value)
+  if (m_dynamic_value && m_dynamic_value->GetError().Success())
     return m_dynamic_value->GetSP();
   else
     return ValueObjectSP();

lldb/source/Core/ValueObjectConstResult.cpp

@@ -287,7 +287,7 @@ ValueObjectConstResult::GetDynamicValue(lldb::DynamicValueType use_dynamic) {
       if (process && process->IsPossibleDynamicValue(*this))
         m_dynamic_value = new ValueObjectDynamicValue(*this, use_dynamic);
     }
-    if (m_dynamic_value)
+    if (m_dynamic_value && m_dynamic_value->GetError().Success())
       return m_dynamic_value->GetSP();
   }
   return ValueObjectSP();

lldb/source/Core/ValueObjectDynamicValue.cpp

@@ -187,17 +187,19 @@ bool ValueObjectDynamicValue::UpdateValue() {
     m_type_impl.Clear();
   }
 
-  // If we don't have a dynamic type, then make ourselves just a echo of our
-  // parent. Or we could return false, and make ourselves an echo of our
-  // parent?
+  // If we don't have a dynamic type, set ourselves to be invalid and return
+  // false.  We used to try to produce a dynamic ValueObject that behaved "like"
+  // its parent, but that failed for ValueObjectConstResult, which is too 
+  // complex a beast to try to emulate.  If we return an invalid ValueObject,
+  // clients will end up getting the static value instead, which behaves
+  // correctly.
   if (!found_dynamic_type) {
     if (m_dynamic_type_info)
       SetValueDidChange(true);
     ClearDynamicTypeInformation();
     m_dynamic_type_info.Clear();
-    m_value = m_parent->GetValue();
-    m_error = m_value.GetValueAsData(&exe_ctx, m_data, GetModule().get());
-    return m_error.Success();
+    m_error.SetErrorString("no dynamic type found");
+    return false;
   }
 
   Value old_value(m_value);

lldb/source/Plugins/LanguageRuntime/CPlusPlus/ItaniumABI/ItaniumABILanguageRuntime.cpp

@@ -583,7 +583,11 @@ ValueObjectSP ItaniumABILanguageRuntime::GetExceptionObjectForThread(
   ValueObjectSP exception = ValueObject::CreateValueObjectFromData(
       "exception", exception_isw.GetAsData(m_process->GetByteOrder()), exe_ctx,
       voidstar);
-  exception = exception->GetDynamicValue(eDynamicDontRunTarget);
+  ValueObjectSP dyn_exception 
+      = exception->GetDynamicValue(eDynamicDontRunTarget);
+  // If we succeed in making a dynamic value, return that:
+  if (dyn_exception) 
+     return dyn_exception;
 
   return exception;
 }

lldb/test/API/python_api/value/addr_of_void_star/Makefile

@@ -0,0 +1,3 @@
+C_SOURCES := main.c
+
+include Makefile.rules

lldb/test/API/python_api/value/addr_of_void_star/TestValueAPIAddressOfVoidStar.py

@@ -0,0 +1,38 @@
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+class ValueAPIVoidStarTestCase(TestBase):
+
+    def test(self):
+        self.build()
+
+        target, process, thread, _ = lldbutil.run_to_source_breakpoint(self,
+                                                                       "Break at this line",
+                                                                       lldb.SBFileSpec("main.c"))
+        frame = thread.GetFrameAtIndex(0)
+
+        # Verify that the expression result for a void * behaves the same way as the
+        # variable value.
+
+        var_val = frame.FindVariable("void_ptr")
+        self.assertSuccess(var_val.GetError(), "Var version made correctly")
+
+        expr_val = frame.EvaluateExpression("void_ptr")
+        self.assertSuccess(expr_val.GetError(), "Expr version succeeds")
+
+        # The pointer values should be equal:
+        self.assertEqual(var_val.unsigned, expr_val.unsigned, "Values are equal")
+
+        # Both versions should have valid AddressOf, and they should be the same.
+
+        val_addr_of = var_val.AddressOf()
+        self.assertNotEqual(val_addr_of, lldb.LLDB_INVALID_ADDRESS, "Var addr of right")
+
+        expr_addr_of = expr_val.AddressOf()
+        self.assertNotEqual(expr_addr_of, lldb.LLDB_INVALID_ADDRESS, "Expr addr of right")
+
+        # The AddressOf values should also be equal.
+        self.assertEqual(expr_addr_of.unsigned, val_addr_of.unsigned, "Addr of equal")
+

lldb/test/API/python_api/value/addr_of_void_star/main.c

@@ -0,0 +1,6 @@
+int main (int argc, char const *argv[]) {
+  char *char_ptr = "Some pointer here";
+  void *void_ptr = &char_ptr;
+
+  return 0; // Break at this line
+}