[LLDB] libcxx summary formatters for std::string_view

When printing a std::string_view, print the referenced string as the
summary. Support string_view, u32string_view, u16string_view and
wstring_view, as we do for std::string and friends.

This is based on the existing fomratter for std::string, and just
extracts the data and length members, pushing them through the existing
string formatter.

In testing this, a "FIXME" was corrected for printing of non-ASCII empty
values. Previously, the "u", 'U" etc. prefixes were not printed for
basic_string<> types that were not char. This is trivial to resolve by
printing the prefix before the "".

Differential revision: https://reviews.llvm.org/D112222

3 files changed, 177 insertions, 16 deletions

diff --git a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
index df61cc3853eb..0fb65f5a317d 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
@@ -579,6 +579,51 @@ static void LoadLibCxxFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
                             "std::__[[:alnum:]]+::allocator<wchar_t> >$"),
                 stl_summary_flags, true);
 
+  AddCXXSummary(cpp_category_sp,
+                lldb_private::formatters::LibcxxStringViewSummaryProviderASCII,
+                "std::string_view summary provider",
+                ConstString("^std::__[[:alnum:]]+::string_view$"),
+                stl_summary_flags, true);
+  AddCXXSummary(cpp_category_sp,
+                lldb_private::formatters::LibcxxStringViewSummaryProviderASCII,
+                "std::string_view summary provider",
+                ConstString("^std::__[[:alnum:]]+::basic_string_view<char, "
+                            "std::__[[:alnum:]]+::char_traits<char> >$"),
+                stl_summary_flags, true);
+  AddCXXSummary(
+      cpp_category_sp,
+      lldb_private::formatters::LibcxxStringViewSummaryProviderASCII,
+      "std::string_view summary provider",
+      ConstString("^std::__[[:alnum:]]+::basic_string_view<unsigned char, "
+                  "std::__[[:alnum:]]+::char_traits<unsigned char> >$"),
+      stl_summary_flags, true);
+
+  AddCXXSummary(cpp_category_sp,
+                lldb_private::formatters::LibcxxStringViewSummaryProviderUTF16,
+                "std::u16string_view summary provider",
+                ConstString("^std::__[[:alnum:]]+::basic_string_view<char16_t, "
+                            "std::__[[:alnum:]]+::char_traits<char16_t> >$"),
+                stl_summary_flags, true);
+
+  AddCXXSummary(cpp_category_sp,
+                lldb_private::formatters::LibcxxStringViewSummaryProviderUTF32,
+                "std::u32string_view summary provider",
+                ConstString("^std::__[[:alnum:]]+::basic_string_view<char32_t, "
+                            "std::__[[:alnum:]]+::char_traits<char32_t> >$"),
+                stl_summary_flags, true);
+
+  AddCXXSummary(cpp_category_sp,
+                lldb_private::formatters::LibcxxWStringViewSummaryProvider,
+                "std::wstring_view summary provider",
+                ConstString("^std::__[[:alnum:]]+::wstring_view$"),
+                stl_summary_flags, true);
+  AddCXXSummary(cpp_category_sp,
+                lldb_private::formatters::LibcxxWStringViewSummaryProvider,
+                "std::wstring_view summary provider",
+                ConstString("^std::__[[:alnum:]]+::basic_string_view<wchar_t, "
+                            "std::__[[:alnum:]]+::char_traits<wchar_t> >$"),
+                stl_summary_flags, true);
+
   SyntheticChildren::Flags stl_synth_flags;
   stl_synth_flags.SetCascades(true).SetSkipPointers(false).SetSkipReferences(
       false);
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp
index b9aef0ae7d9e..21196393371e 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp
@@ -19,6 +19,7 @@
 #include "lldb/Target/ProcessStructReader.h"
 #include "lldb/Target/SectionLoadList.h"
 #include "lldb/Target/Target.h"
+#include "lldb/Utility/ConstString.h"
 #include "lldb/Utility/DataBufferHeap.h"
 #include "lldb/Utility/Endian.h"
 #include "lldb/Utility/Status.h"
@@ -26,6 +27,7 @@
 
 #include "Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.h"
 #include "Plugins/TypeSystem/Clang/TypeSystemClang.h"
+#include <tuple>
 
 using namespace lldb;
 using namespace lldb_private;
@@ -560,7 +562,7 @@ ExtractLibcxxStringInfo(ValueObject &valobj) {
     return {};
 
   ValueObjectSP layout_decider(
-    D->GetChildAtIndexPath(llvm::ArrayRef<size_t>({0, 0})));
+      D->GetChildAtIndexPath(llvm::ArrayRef<size_t>({0, 0})));
 
   // this child should exist
   if (!layout_decider)
@@ -643,16 +645,10 @@ ExtractLibcxxStringInfo(ValueObject &valobj) {
   return std::make_pair(size, location_sp);
 }
 
-bool lldb_private::formatters::LibcxxWStringSummaryProvider(
-    ValueObject &valobj, Stream &stream,
-    const TypeSummaryOptions &summary_options) {
-  auto string_info = ExtractLibcxxStringInfo(valobj);
-  if (!string_info)
-    return false;
-  uint64_t size;
-  ValueObjectSP location_sp;
-  std::tie(size, location_sp) = *string_info;
-
+static bool
+LibcxxWStringSummaryProvider(ValueObject &valobj, Stream &stream,
+                             const TypeSummaryOptions &summary_options,
+                             ValueObjectSP location_sp, size_t size) {
   if (size == 0) {
     stream.Printf("L\"\"");
     return true;
@@ -660,7 +656,6 @@ bool lldb_private::formatters::LibcxxWStringSummaryProvider(
   if (!location_sp)
     return false;
 
-
   StringPrinter::ReadBufferAndDumpToStreamOptions options(valobj);
   if (summary_options.GetCapping() == TypeSummaryCapping::eTypeSummaryCapped) {
     const auto max_size = valobj.GetTargetSP()->GetMaximumSizeOfStringSummary();
@@ -714,10 +709,9 @@ bool lldb_private::formatters::LibcxxWStringSummaryProvider(
   return false;
 }
 
-template <StringPrinter::StringElementType element_type>
-bool LibcxxStringSummaryProvider(ValueObject &valobj, Stream &stream,
-                                 const TypeSummaryOptions &summary_options,
-                                 std::string prefix_token) {
+bool lldb_private::formatters::LibcxxWStringSummaryProvider(
+    ValueObject &valobj, Stream &stream,
+    const TypeSummaryOptions &summary_options) {
   auto string_info = ExtractLibcxxStringInfo(valobj);
   if (!string_info)
     return false;
@@ -725,6 +719,17 @@ bool LibcxxStringSummaryProvider(ValueObject &valobj, Stream &stream,
   ValueObjectSP location_sp;
   std::tie(size, location_sp) = *string_info;
 
+  return ::LibcxxWStringSummaryProvider(valobj, stream, summary_options,
+                                        location_sp, size);
+}
+
+template <StringPrinter::StringElementType element_type>
+static bool
+LibcxxStringSummaryProvider(ValueObject &valobj, Stream &stream,
+                            const TypeSummaryOptions &summary_options,
+                            std::string prefix_token, ValueObjectSP location_sp,
+                            uint64_t size) {
+
   if (size == 0) {
     stream.Printf("\"\"");
     return true;
@@ -763,6 +768,21 @@ bool LibcxxStringSummaryProvider(ValueObject &valobj, Stream &stream,
 }
 
 template <StringPrinter::StringElementType element_type>
+static bool
+LibcxxStringSummaryProvider(ValueObject &valobj, Stream &stream,
+                            const TypeSummaryOptions &summary_options,
+                            std::string prefix_token) {
+  auto string_info = ExtractLibcxxStringInfo(valobj);
+  if (!string_info)
+    return false;
+  uint64_t size;
+  ValueObjectSP location_sp;
+  std::tie(size, location_sp) = *string_info;
+
+  return LibcxxStringSummaryProvider<element_type>(
+      valobj, stream, summary_options, prefix_token, location_sp, size);
+}
+template <StringPrinter::StringElementType element_type>
 static bool formatStringImpl(ValueObject &valobj, Stream &stream,
                              const TypeSummaryOptions &summary_options,
                              std::string prefix_token) {
@@ -796,3 +816,83 @@ bool lldb_private::formatters::LibcxxStringSummaryProviderUTF32(
   return formatStringImpl<StringPrinter::StringElementType::UTF32>(
       valobj, stream, summary_options, "U");
 }
+
+static std::tuple<bool, ValueObjectSP, size_t>
+LibcxxExtractStringViewData(ValueObject& valobj) {
+  ConstString g_data_name("__data");
+  ConstString g_size_name("__size");
+  auto dataobj = valobj.GetChildMemberWithName(g_data_name, true);
+  auto sizeobj = valobj.GetChildMemberWithName(g_size_name, true);
+
+  if (!dataobj || !sizeobj)
+    return std::make_tuple<bool,ValueObjectSP,size_t>(false, {}, {});
+
+  if (!dataobj->GetError().Success() || !sizeobj->GetError().Success())
+    return std::make_tuple<bool,ValueObjectSP,size_t>(false, {}, {});
+
+  bool success{false};
+  uint64_t size = sizeobj->GetValueAsUnsigned(0, &success);
+  if (!success)
+    return std::make_tuple<bool,ValueObjectSP,size_t>(false, {}, {});
+
+  return std::make_tuple(true,dataobj,size);
+}
+
+template <StringPrinter::StringElementType element_type>
+static bool formatStringViewImpl(ValueObject &valobj, Stream &stream,
+                                 const TypeSummaryOptions &summary_options,
+                                 std::string prefix_token) {
+
+  bool success;
+  ValueObjectSP dataobj;
+  size_t size;
+  std::tie(success, dataobj, size) = LibcxxExtractStringViewData(valobj);
+
+  if (!success) {
+    stream << "Summary Unavailable";
+    return true;
+  }
+
+  return LibcxxStringSummaryProvider<element_type>(
+      valobj, stream, summary_options, prefix_token, dataobj, size);
+}
+
+bool lldb_private::formatters::LibcxxStringViewSummaryProviderASCII(
+    ValueObject &valobj, Stream &stream,
+    const TypeSummaryOptions &summary_options) {
+  return formatStringViewImpl<StringPrinter::StringElementType::ASCII>(
+      valobj, stream, summary_options, "");
+}
+
+bool lldb_private::formatters::LibcxxStringViewSummaryProviderUTF16(
+    ValueObject &valobj, Stream &stream,
+    const TypeSummaryOptions &summary_options) {
+  return formatStringViewImpl<StringPrinter::StringElementType::UTF16>(
+      valobj, stream, summary_options, "u");
+}
+
+bool lldb_private::formatters::LibcxxStringViewSummaryProviderUTF32(
+    ValueObject &valobj, Stream &stream,
+    const TypeSummaryOptions &summary_options) {
+  return formatStringViewImpl<StringPrinter::StringElementType::UTF32>(
+      valobj, stream, summary_options, "U");
+}
+
+bool lldb_private::formatters::LibcxxWStringViewSummaryProvider(
+    ValueObject &valobj, Stream &stream,
+    const TypeSummaryOptions &summary_options) {
+
+  bool success;
+  ValueObjectSP dataobj;
+  size_t size;
+  std::tie( success, dataobj, size ) = LibcxxExtractStringViewData(valobj);
+
+  if (!success) {
+    stream << "Summary Unavailable";
+    return true;
+  }
+
+
+  return ::LibcxxWStringSummaryProvider(valobj, stream, summary_options,
+                                        dataobj, size);
+}
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxx.h b/lldb/source/Plugins/Language/CPlusPlus/LibCxx.h
index 80dc71787ceb..0f166ae24912 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibCxx.h
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibCxx.h
@@ -34,6 +34,22 @@ bool LibcxxWStringSummaryProvider(
     ValueObject &valobj, Stream &stream,
     const TypeSummaryOptions &options); // libc++ std::wstring
 
+bool LibcxxStringViewSummaryProviderASCII(
+    ValueObject &valueObj, Stream &stream,
+    const TypeSummaryOptions &summary_options); // libc++ std::string_view
+
+bool LibcxxStringViewSummaryProviderUTF16(
+    ValueObject &valobj, Stream &stream,
+    const TypeSummaryOptions &summary_options); // libc++ std::u16string_view
+
+bool LibcxxStringViewSummaryProviderUTF32(
+    ValueObject &valobj, Stream &stream,
+    const TypeSummaryOptions &summary_options); // libc++ std::u32string_view
+
+bool LibcxxWStringViewSummaryProvider(
+    ValueObject &valobj, Stream &stream,
+    const TypeSummaryOptions &options); // libc++ std::wstring_view
+
 bool LibcxxOptionalSummaryProvider(
     ValueObject &valobj, Stream &stream,
     const TypeSummaryOptions &options); // libc++ std::optional<>