Fix an issue where LLDB would crash if one tried to 'frame variable' an unordered_map more than once in a stop due to the synthetic provider not properly caching the ValueObjects it was returning for the child elements

Fixes rdar://26470909

llvm-svn: 270752

lldb/packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/unordered/TestDataFormatterUnordered.py

@@ -72,5 +72,6 @@ class LibcxxUnorderedDataFormatterTestCase(TestBase):
                          '(\[\d\] = "world"(\\n|.)+){2}'])
 
     def look_for_content_and_continue(self, var_name, patterns):
+        self.expect( ("frame variable %s" % var_name), patterns=patterns)
         self.expect( ("frame variable %s" % var_name), patterns=patterns)
         self.runCmd("continue")

lldb/source/Plugins/Language/CPlusPlus/LibCxxUnorderedMap.cpp

@@ -125,10 +125,13 @@ lldb_private::formatters::LibcxxStdUnorderedMapSyntheticFrontEnd::GetChildAtInde
         return lldb::ValueObjectSP();
     const bool thread_and_frame_only_if_stopped = true;
     ExecutionContext exe_ctx = val_hash.first->GetExecutionContextRef().Lock(thread_and_frame_only_if_stopped);
-    return val_hash.first->CreateValueObjectFromData(stream.GetData(),
-                                                     data,
-                                                     exe_ctx,
-                                                     val_hash.first->GetCompilerType());
+    ValueObjectSP child_sp(val_hash.first->CreateValueObjectFromData(stream.GetData(),
+                                                                     data,
+                                                                     exe_ctx,
+                                                                     val_hash.first->GetCompilerType()));
+    if (child_sp)
+        m_children.emplace(idx, child_sp);
+    return child_sp;
 }
 
 bool