[LLDB] Simplify libstdc++ string summaries (#146562)

Nerixyz · web-flow · commit 4c7a706589ca · 2025-07-02T11:21:31.000+01:00
From #143177. This combines the summaries for the pre- and post C++ 11 `std::string` as well as `std::wstring`. In all cases, the data pointer is reachable through `_M_dataplus._M_p`. It has the correct type (i.e. `char*`/`wchar_t*`) and it's null terminated, so LLDB knows how to format it as expected when using `GetSummaryAsCString`.
diff --git a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
@@ -1344,38 +1344,31 @@ static void LoadLibStdcppFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
       .SetShowMembersOneLiner(false)
       .SetHideItemNames(false);
 
-  lldb::TypeSummaryImplSP std_string_summary_sp(
-      new StringSummaryFormat(stl_summary_flags, "${var._M_dataplus._M_p}"));
-
-  lldb::TypeSummaryImplSP cxx11_string_summary_sp(new CXXFunctionSummaryFormat(
+  lldb::TypeSummaryImplSP string_summary_sp(new CXXFunctionSummaryFormat(
       stl_summary_flags, LibStdcppStringSummaryProvider,
-      "libstdc++ c++11 std::string summary provider"));
-  lldb::TypeSummaryImplSP cxx11_wstring_summary_sp(new CXXFunctionSummaryFormat(
-      stl_summary_flags, LibStdcppWStringSummaryProvider,
-      "libstdc++ c++11 std::wstring summary provider"));
+      "libstdc++ std::(w)string summary provider"));
 
   cpp_category_sp->AddTypeSummary("std::string", eFormatterMatchExact,
-                                  std_string_summary_sp);
+                                  string_summary_sp);
   cpp_category_sp->AddTypeSummary("std::basic_string<char>",
-                                  eFormatterMatchExact, std_string_summary_sp);
+                                  eFormatterMatchExact, string_summary_sp);
   cpp_category_sp->AddTypeSummary(
       "std::basic_string<char,std::char_traits<char>,std::allocator<char> >",
-      eFormatterMatchExact, std_string_summary_sp);
+      eFormatterMatchExact, string_summary_sp);
   cpp_category_sp->AddTypeSummary(
       "std::basic_string<char, std::char_traits<char>, std::allocator<char> >",
-      eFormatterMatchExact, std_string_summary_sp);
+      eFormatterMatchExact, string_summary_sp);
 
   cpp_category_sp->AddTypeSummary("std::__cxx11::string", eFormatterMatchExact,
-                                  cxx11_string_summary_sp);
+                                  string_summary_sp);
   cpp_category_sp->AddTypeSummary(
       "std::__cxx11::basic_string<char, std::char_traits<char>, "
       "std::allocator<char> >",
-      eFormatterMatchExact, cxx11_string_summary_sp);
+      eFormatterMatchExact, string_summary_sp);
   cpp_category_sp->AddTypeSummary("std::__cxx11::basic_string<unsigned char, "
                                   "std::char_traits<unsigned char>, "
                                   "std::allocator<unsigned char> >",
-                                  eFormatterMatchExact,
-                                  cxx11_string_summary_sp);
+                                  eFormatterMatchExact, string_summary_sp);
 
   // making sure we force-pick the summary for printing wstring (_M_p is a
   // wchar_t*)
@@ -1395,11 +1388,11 @@ static void LoadLibStdcppFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
       eFormatterMatchExact, std_wstring_summary_sp);
 
   cpp_category_sp->AddTypeSummary("std::__cxx11::wstring", eFormatterMatchExact,
-                                  cxx11_wstring_summary_sp);
+                                  string_summary_sp);
   cpp_category_sp->AddTypeSummary(
       "std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, "
       "std::allocator<wchar_t> >",
-      eFormatterMatchExact, cxx11_wstring_summary_sp);
+      eFormatterMatchExact, string_summary_sp);
 
   SyntheticChildren::Flags stl_synth_flags;
   stl_synth_flags.SetCascades(true).SetSkipPointers(false).SetSkipReferences(
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp
@@ -239,122 +239,12 @@ VectorIteratorSyntheticFrontEnd::GetIndexOfChildWithName(ConstString name) {
 
 bool lldb_private::formatters::LibStdcppStringSummaryProvider(
     ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
-  const bool scalar_is_load_addr = true;
-  auto [addr_of_string, addr_type] =
-      valobj.IsPointerOrReferenceType()
-          ? valobj.GetPointerValue()
-          : valobj.GetAddressOf(scalar_is_load_addr);
-  if (addr_of_string != LLDB_INVALID_ADDRESS) {
-    switch (addr_type) {
-    case eAddressTypeLoad: {
-      ProcessSP process_sp(valobj.GetProcessSP());
-      if (!process_sp)
-        return false;
-
-      StringPrinter::ReadStringAndDumpToStreamOptions options(valobj);
-      Status error;
-      lldb::addr_t addr_of_data =
-          process_sp->ReadPointerFromMemory(addr_of_string, error);
-      if (error.Fail() || addr_of_data == 0 ||
-          addr_of_data == LLDB_INVALID_ADDRESS)
-        return false;
-      options.SetLocation(addr_of_data);
-      options.SetTargetSP(valobj.GetTargetSP());
-      options.SetStream(&stream);
-      options.SetNeedsZeroTermination(false);
-      options.SetBinaryZeroIsTerminator(true);
-      lldb::addr_t size_of_data = process_sp->ReadPointerFromMemory(
-          addr_of_string + process_sp->GetAddressByteSize(), error);
-      if (error.Fail())
-        return false;
-      options.SetSourceSize(size_of_data);
-      options.SetHasSourceSize(true);
-
-      if (!StringPrinter::ReadStringAndDumpToStream<
-              StringPrinter::StringElementType::UTF8>(options)) {
-        stream.Printf("Summary Unavailable");
-        return true;
-      } else
-        return true;
-    } break;
-    case eAddressTypeHost:
-      break;
-    case eAddressTypeInvalid:
-    case eAddressTypeFile:
-      break;
-    }
-  }
-  return false;
-}
+  ValueObjectSP ptr = valobj.GetChildAtNamePath({"_M_dataplus", "_M_p"});
+  if (!ptr)
+    return false;
 
-bool lldb_private::formatters::LibStdcppWStringSummaryProvider(
-    ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
-  const bool scalar_is_load_addr = true;
-  auto [addr_of_string, addr_type] = valobj.GetAddressOf(scalar_is_load_addr);
-  if (addr_of_string != LLDB_INVALID_ADDRESS) {
-    switch (addr_type) {
-    case eAddressTypeLoad: {
-      ProcessSP process_sp(valobj.GetProcessSP());
-      if (!process_sp)
-        return false;
-
-      CompilerType wchar_compiler_type =
-          valobj.GetCompilerType().GetBasicTypeFromAST(lldb::eBasicTypeWChar);
-
-      if (!wchar_compiler_type)
-        return false;
-
-      // Safe to pass nullptr for exe_scope here.
-      std::optional<uint64_t> size =
-          llvm::expectedToOptional(wchar_compiler_type.GetBitSize(nullptr));
-      if (!size)
-        return false;
-      const uint32_t wchar_size = *size;
-
-      StringPrinter::ReadStringAndDumpToStreamOptions options(valobj);
-      Status error;
-      lldb::addr_t addr_of_data =
-          process_sp->ReadPointerFromMemory(addr_of_string, error);
-      if (error.Fail() || addr_of_data == 0 ||
-          addr_of_data == LLDB_INVALID_ADDRESS)
-        return false;
-      options.SetLocation(addr_of_data);
-      options.SetTargetSP(valobj.GetTargetSP());
-      options.SetStream(&stream);
-      options.SetNeedsZeroTermination(false);
-      options.SetBinaryZeroIsTerminator(false);
-      lldb::addr_t size_of_data = process_sp->ReadPointerFromMemory(
-          addr_of_string + process_sp->GetAddressByteSize(), error);
-      if (error.Fail())
-        return false;
-      options.SetSourceSize(size_of_data);
-      options.SetHasSourceSize(true);
-      options.SetPrefixToken("L");
-
-      switch (wchar_size) {
-      case 8:
-        return StringPrinter::ReadStringAndDumpToStream<
-            StringPrinter::StringElementType::UTF8>(options);
-      case 16:
-        return StringPrinter::ReadStringAndDumpToStream<
-            StringPrinter::StringElementType::UTF16>(options);
-      case 32:
-        return StringPrinter::ReadStringAndDumpToStream<
-            StringPrinter::StringElementType::UTF32>(options);
-      default:
-        stream.Printf("size for wchar_t is not valid");
-        return true;
-      }
-      return true;
-    } break;
-    case eAddressTypeHost:
-      break;
-    case eAddressTypeInvalid:
-    case eAddressTypeFile:
-      break;
-    }
-  }
-  return false;
+  stream << ptr->GetSummaryAsCString();
+  return true;
 }
 
 LibStdcppSharedPtrSyntheticFrontEnd::LibStdcppSharedPtrSyntheticFrontEnd(
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.h b/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.h
@@ -18,11 +18,7 @@ namespace lldb_private {
 namespace formatters {
 bool LibStdcppStringSummaryProvider(
     ValueObject &valobj, Stream &stream,
-    const TypeSummaryOptions &options); // libcstdc++ c++11 std::string
-
-bool LibStdcppWStringSummaryProvider(
-    ValueObject &valobj, Stream &stream,
-    const TypeSummaryOptions &options); // libcstdc++ c++11 std::wstring
+    const TypeSummaryOptions &options); // libstdc++ std::string
 
 bool LibStdcppSmartPointerSummaryProvider(
     ValueObject &valobj, Stream &stream,
