[lldb] Add summary for NSIndirectTaggedPointerString

[kastiglione]

rdar://143164164

[llvmbot]

@llvm/pr-subscribers-lldb

Author: Dave Lee (kastiglione)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/136025.diff

3 Files Affected:

• (modified) lldb/source/Plugins/Language/ObjC/NSString.cpp (+45-6)
• (modified) lldb/source/Plugins/Language/ObjC/NSString.h (+4)
• (modified) lldb/source/Plugins/Language/ObjC/ObjCLanguage.cpp (+4)

diff --git a/lldb/source/Plugins/Language/ObjC/NSString.cpp b/lldb/source/Plugins/Language/ObjC/NSString.cpp
index a99d042572bfe..11b4c6c5df8af 100644
--- a/lldb/source/Plugins/Language/ObjC/NSString.cpp
+++ b/lldb/source/Plugins/Language/ObjC/NSString.cpp
@@ -63,12 +63,17 @@ bool lldb_private::formatters::NSStringSummaryProvider(
   if (class_name.empty())
     return false;
 
-  bool is_tagged_ptr = class_name == "NSTaggedPointerString" &&
-                       descriptor->GetTaggedPointerInfo();
-  // for a tagged pointer, the descriptor has everything we need
-  if (is_tagged_ptr)
-    return NSTaggedString_SummaryProvider(valobj, descriptor, stream,
-                                          summary_options);
+  // for tagged pointers, the descriptor has everything needed.
+  bool is_tagged = descriptor->GetTaggedPointerInfo();
+  if (is_tagged) {
+    if (class_name == "NSTaggedPointerString")
+      return NSTaggedString_SummaryProvider(valobj, descriptor, stream,
+                                            summary_options);
+
+    if (class_name == "NSIndirectTaggedPointerString")
+      return NSIndirectTaggedString_SummaryProvider(valobj, descriptor, stream,
+                                                    summary_options);
+  }
 
   auto &additionals_map(NSString_Additionals::GetAdditionalSummaries());
   auto iter = additionals_map.find(class_name_cs), end = additionals_map.end();
@@ -368,3 +373,37 @@ bool lldb_private::formatters::NSTaggedString_SummaryProvider(
   stream << suffix;
   return true;
 }
+
+bool lldb_private::formatters::NSIndirectTaggedString_SummaryProvider(
+    ValueObject &valobj, ObjCLanguageRuntime::ClassDescriptorSP descriptor,
+    Stream &stream, const TypeSummaryOptions &summary_options) {
+  if (!descriptor)
+    return false;
+
+  uint64_t payload = 0;
+  if (!descriptor->GetTaggedPointerInfo(nullptr, nullptr, &payload))
+    return false;
+
+  // First 47 bits are the address of the contents.
+  addr_t ptr = payload & 0x7fffffffffffULL;
+  // Next 13 bits are the string's length.
+  size_t size = (payload >> 47) & 0x1fff;
+
+  Status status;
+  char buf[8192];
+  if (auto process_sp = valobj.GetProcessSP())
+    if (process_sp->ReadMemory(ptr, buf, size, status)) {
+      llvm::StringRef prefix, suffix;
+      if (auto *language = Language::FindPlugin(summary_options.GetLanguage()))
+        std::tie(prefix, suffix) =
+            language->GetFormatterPrefixSuffix("NSString");
+      stream << prefix << '"';
+      stream.PutCString({buf, size});
+      stream << '"' << suffix;
+      return true;
+    }
+
+  if (status.Fail())
+    stream.Format("<{0}>", status);
+  return false;
+}
diff --git a/lldb/source/Plugins/Language/ObjC/NSString.h b/lldb/source/Plugins/Language/ObjC/NSString.h
index 8c9fcf955f1f8..5d405b30b6817 100644
--- a/lldb/source/Plugins/Language/ObjC/NSString.h
+++ b/lldb/source/Plugins/Language/ObjC/NSString.h
@@ -25,6 +25,10 @@ bool NSTaggedString_SummaryProvider(
     ValueObject &valobj, ObjCLanguageRuntime::ClassDescriptorSP descriptor,
     Stream &stream, const TypeSummaryOptions &summary_options);
 
+bool NSIndirectTaggedString_SummaryProvider(
+    ValueObject &valobj, ObjCLanguageRuntime::ClassDescriptorSP descriptor,
+    Stream &stream, const TypeSummaryOptions &summary_options);
+
 bool NSAttributedStringSummaryProvider(ValueObject &valobj, Stream &stream,
                                        const TypeSummaryOptions &options);
 
diff --git a/lldb/source/Plugins/Language/ObjC/ObjCLanguage.cpp b/lldb/source/Plugins/Language/ObjC/ObjCLanguage.cpp
index c835b439a64dd..3b8e21cbb9269 100644
--- a/lldb/source/Plugins/Language/ObjC/ObjCLanguage.cpp
+++ b/lldb/source/Plugins/Language/ObjC/ObjCLanguage.cpp
@@ -691,6 +691,10 @@ static void LoadObjCFormatters(TypeCategoryImplSP objc_category_sp) {
   AddCXXSummary(
       objc_category_sp, lldb_private::formatters::NSStringSummaryProvider,
       "NSString summary provider", "NSTaggedPointerString", appkit_flags);
+  AddCXXSummary(objc_category_sp,
+                lldb_private::formatters::NSStringSummaryProvider,
+                "NSString summary provider", "NSIndirectTaggedPointerString",
+                appkit_flags);
 
   AddCXXSummary(objc_category_sp,
                 lldb_private::formatters::NSAttributedStringSummaryProvider,

[adrian-prantl]

Given how deeply nested lldb stacks often are, I would probably use a std::vector here and allocate this on the heap.

[adrian-prantl]

and then you can reserve() exactly size

[kastiglione]

good call, done

[adrian-prantl]

LGTM with some nits

[adrian-prantl]

Does PutCString scan through the buffer until it finds a NUL byte or does it copy size bytes (which would be faster).

I doubt this affects the performance measurably. Just being curious.

[kastiglione]

or does it copy size bytes (which would be faster).

It does this, the faster option.