Data formatter support for libc++ std::atomic<T>

On libc++ std::atomic is a fairly simple data type (layout wise, at least), wrapping actual contents in a member variable named "__a_"

All the formatters are doing is "peel away" this intermediate layer and exposing user data as direct children or values of the std::atomic root variable

Fixes rdar://24329405

llvm-svn: 260752
diff --git a/lldb/source/Plugins/Language/CPlusPlus/CMakeLists.txt b/lldb/source/Plugins/Language/CPlusPlus/CMakeLists.txt
index 0b0f0f4..4efb681 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/CMakeLists.txt
+++ b/lldb/source/Plugins/Language/CPlusPlus/CMakeLists.txt
@@ -2,6 +2,7 @@
   CPlusPlusLanguage.cpp
   CxxStringTypes.cpp
   LibCxx.cpp
+  LibCxxAtomic.cpp
   LibCxxInitializerList.cpp
   LibCxxList.cpp
   LibCxxMap.cpp
diff --git a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
index 09031e2..048ed58 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
@@ -23,6 +23,7 @@
 
 #include "CxxStringTypes.h"
 #include "LibCxx.h"
+#include "LibCxxAtomic.h"
 #include "LibStdcpp.h"
 
 #include <cstring>
@@ -529,7 +530,8 @@
     AddCXXSynthetic(cpp_category_sp, lldb_private::formatters::LibcxxStdMapSyntheticFrontEndCreator, "libc++ std::multimap synthetic children", ConstString("^std::__1::multimap<.+> >(( )?&)?$"), stl_synth_flags, true);
     AddCXXSynthetic(cpp_category_sp, lldb_private::formatters::LibcxxStdUnorderedMapSyntheticFrontEndCreator, "libc++ std::unordered containers synthetic children", ConstString("^(std::__1::)unordered_(multi)?(map|set)<.+> >$"), stl_synth_flags, true);
     AddCXXSynthetic(cpp_category_sp, lldb_private::formatters::LibcxxInitializerListSyntheticFrontEndCreator, "libc++ std::initializer_list synthetic children", ConstString("^std::initializer_list<.+>(( )?&)?$"), stl_synth_flags, true);
-    
+    AddCXXSynthetic(cpp_category_sp, lldb_private::formatters::LibcxxAtomicSyntheticFrontEndCreator, "libc++ std::atomic synthetic children", ConstString("^std::__1::atomic<.+>$"), stl_synth_flags, true);
+
     cpp_category_sp->GetRegexTypeSyntheticsContainer()->Add(RegularExpressionSP(new RegularExpression("^(std::__1::)deque<.+>(( )?&)?$")),
                                                                SyntheticChildrenSP(new ScriptedSyntheticChildren(stl_synth_flags,
                                                                                                                  "lldb.formatters.cpp.libcxx.stddeque_SynthProvider")));
@@ -550,6 +552,7 @@
     AddCXXSummary(cpp_category_sp, lldb_private::formatters::LibcxxContainerSummaryProvider, "libc++ std::multiset summary provider", ConstString("^std::__1::multiset<.+>(( )?&)?$"), stl_summary_flags, true);
     AddCXXSummary(cpp_category_sp, lldb_private::formatters::LibcxxContainerSummaryProvider, "libc++ std::multimap summary provider", ConstString("^std::__1::multimap<.+>(( )?&)?$"), stl_summary_flags, true);
     AddCXXSummary(cpp_category_sp, lldb_private::formatters::LibcxxContainerSummaryProvider, "libc++ std::unordered containers summary provider", ConstString("^(std::__1::)unordered_(multi)?(map|set)<.+> >$"), stl_summary_flags, true);
+    AddCXXSummary(cpp_category_sp, lldb_private::formatters::LibCxxAtomicSummaryProvider, "libc++ std::atomic summary provider", ConstString("^std::__1::atomic<.+>$"), stl_summary_flags, true);
     
     stl_summary_flags.SetSkipPointers(true);
     
@@ -560,8 +563,6 @@
     
     AddCXXSummary(cpp_category_sp, lldb_private::formatters::LibcxxContainerSummaryProvider, "libc++ std::vector<bool> summary provider", ConstString("std::__1::vector<bool, std::__1::allocator<bool> >"), stl_summary_flags);
     AddCXXSynthetic(cpp_category_sp, lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEndCreator, "std::map iterator synthetic children", ConstString("^std::__1::__map_iterator<.+>$"), stl_synth_flags, true);
-    
-    AddFilter(cpp_category_sp, {"__a_"}, "libc++ std::atomic filter", ConstString("^std::__1::atomic<.*>$"), stl_synth_flags, true);
 #endif
 }
 
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxxAtomic.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibCxxAtomic.cpp
new file mode 100644
index 0000000..7a35be3
--- /dev/null
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibCxxAtomic.cpp
@@ -0,0 +1,122 @@
+//===-- LibCxxAtomic.cpp ------------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "LibCxxAtomic.h"
+#include "lldb-forward.h"
+
+using namespace lldb;
+using namespace lldb_private;
+using namespace lldb_private::formatters;
+
+bool
+lldb_private::formatters::LibCxxAtomicSummaryProvider (ValueObject& valobj, Stream& stream, const TypeSummaryOptions& options)
+{
+    static ConstString g___a_("__a_");
+    
+    if (ValueObjectSP child = valobj.GetChildMemberWithName(g___a_, true))
+    {
+        std::string summary;
+        if (child->GetSummaryAsCString(summary, options) && summary.size() > 0)
+        {
+            stream.Printf("%s", summary.c_str());
+            return true;
+        }
+    }
+    
+    return false;
+}
+
+namespace lldb_private {
+    namespace formatters {
+        class LibcxxStdAtomicSyntheticFrontEnd : public SyntheticChildrenFrontEnd
+        {
+        public:
+            LibcxxStdAtomicSyntheticFrontEnd (lldb::ValueObjectSP valobj_sp);
+            
+            ~LibcxxStdAtomicSyntheticFrontEnd() override = default;
+            
+            size_t
+            CalculateNumChildren() override;
+            
+            lldb::ValueObjectSP
+            GetChildAtIndex(size_t idx) override;
+            
+            bool
+            Update() override;
+            
+            bool
+            MightHaveChildren() override;
+            
+            size_t
+            GetIndexOfChildWithName(const ConstString &name) override;
+            
+            lldb::ValueObjectSP
+            GetSyntheticValue () override;
+        private:
+            ValueObject *m_real_child;
+        };
+    } // namespace formatters
+} // namespace lldb_private
+
+lldb_private::formatters::LibcxxStdAtomicSyntheticFrontEnd::LibcxxStdAtomicSyntheticFrontEnd (lldb::ValueObjectSP valobj_sp) :
+    SyntheticChildrenFrontEnd(*valobj_sp),
+    m_real_child(nullptr)
+{
+}
+
+bool
+lldb_private::formatters::LibcxxStdAtomicSyntheticFrontEnd::Update()
+{
+    static ConstString g___a_("__a_");
+
+    m_real_child = m_backend.GetChildMemberWithName(g___a_, true).get();
+    
+    return false;
+}
+
+bool
+lldb_private::formatters::LibcxxStdAtomicSyntheticFrontEnd::MightHaveChildren()
+{
+    return true;
+}
+
+size_t
+lldb_private::formatters::LibcxxStdAtomicSyntheticFrontEnd::CalculateNumChildren()
+{
+    return m_real_child ? m_real_child->GetNumChildren() : 0;
+}
+
+lldb::ValueObjectSP
+lldb_private::formatters::LibcxxStdAtomicSyntheticFrontEnd::GetChildAtIndex(size_t idx)
+{
+    return m_real_child ? m_real_child->GetChildAtIndex(idx, true) : nullptr;
+}
+
+size_t
+lldb_private::formatters::LibcxxStdAtomicSyntheticFrontEnd::GetIndexOfChildWithName(const ConstString &name)
+{
+    return m_real_child ? m_real_child->GetIndexOfChildWithName(name) : UINT32_MAX;
+}
+
+lldb::ValueObjectSP
+lldb_private::formatters::LibcxxStdAtomicSyntheticFrontEnd::GetSyntheticValue ()
+{
+    if (m_real_child && m_real_child->CanProvideValue())
+        return m_real_child->GetSP();
+    return nullptr;
+}
+
+SyntheticChildrenFrontEnd*
+lldb_private::formatters::LibcxxAtomicSyntheticFrontEndCreator (CXXSyntheticChildren*, lldb::ValueObjectSP valobj_sp)
+{
+    if (valobj_sp)
+        return new LibcxxStdAtomicSyntheticFrontEnd(valobj_sp);
+    return nullptr;
+}
+
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxxAtomic.h b/lldb/source/Plugins/Language/CPlusPlus/LibCxxAtomic.h
new file mode 100644
index 0000000..5cf729b
--- /dev/null
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibCxxAtomic.h
@@ -0,0 +1,29 @@
+//===-- LibCxxAtomic.h -------------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef liblldb_LibCxxAtomic_h_
+#define liblldb_LibCxxAtomic_h_
+
+#include "lldb/Core/Stream.h"
+#include "lldb/Core/ValueObject.h"
+#include "lldb/DataFormatters/TypeSummary.h"
+#include "lldb/DataFormatters/TypeSynthetic.h"
+
+namespace lldb_private {
+    namespace formatters
+    {
+        bool
+        LibCxxAtomicSummaryProvider (ValueObject& valobj, Stream& stream, const TypeSummaryOptions& options);
+        
+        SyntheticChildrenFrontEnd* LibcxxAtomicSyntheticFrontEndCreator (CXXSyntheticChildren*, lldb::ValueObjectSP);
+        
+    } // namespace formatters
+} // namespace lldb_private
+
+#endif // liblldb_LibCxxAtomic_h_