[lldb] Add an API to derive language-specific runtime information

This is motivated by exposing some Swift language-specific flags
through the API, in the example here it is used to communicate the
Objective-C runtime version. This could also be a meaningful extension
point to get information about "embedded: languages, such as
extracting the C++ version in an Objective-C++ frame or something
along those lines.

Author: adrian-prantl

lldb/include/lldb/API/SBFrame.h

@@ -122,6 +122,11 @@ class LLDB_API SBFrame {
   lldb::SBValue EvaluateExpression(const char *expr,
                                    const SBExpressionOptions &options);
 
+  /// Language plugins can use this API to report language-specific
+  /// runtime information about this compile unit, such as additional
+  /// language version details or feature flags.
+  SBStructuredData GetLanguageInfo();
+
   /// Gets the lexical block that defines the stack frame. Another way to think
   /// of this is it will return the block that contains all of the variables
   /// for a stack frame. Inlined functions are represented as SBBlock objects

lldb/include/lldb/API/SBStructuredData.h

@@ -114,6 +114,7 @@ class SBStructuredData {
   friend class SBCommandReturnObject;
   friend class SBLaunchInfo;
   friend class SBDebugger;
+  friend class SBFrame;
   friend class SBTarget;
   friend class SBProcess;
   friend class SBThread;

lldb/include/lldb/Target/LanguageRuntime.h

@@ -241,6 +241,11 @@ class LanguageRuntime : public Runtime, public PluginInterface {
                        lldb_private::RegisterContext *regctx,
                        bool &behaves_like_zeroth_frame);
 
+  /// Language runtime plugins can use this API to report
+  /// language-specific runtime information about this compile unit,
+  /// such as additional language version details or feature flags.
+  virtual StructuredData::ObjectSP GetLanguageInfo(SymbolContext sc);
+
 protected:
   // The static GetRuntimeUnwindPlan method above is only implemented in the
   // base class; subclasses may override this protected member if they can

lldb/include/lldb/Target/StackFrame.h

@@ -22,6 +22,7 @@
 #include "lldb/Utility/Scalar.h"
 #include "lldb/Utility/Status.h"
 #include "lldb/Utility/StreamString.h"
+#include "lldb/Utility/StructuredData.h"
 #include "lldb/Utility/UserID.h"
 #include "lldb/ValueObject/ValueObjectList.h"
 
@@ -408,6 +409,11 @@ class StackFrame : public ExecutionContextScope,
   /// system implementation details this way.
   bool IsHidden();
 
+  /// Language plugins can use this API to report language-specific
+  /// runtime information about this compile unit, such as additional
+  /// language version details or feature flags.
+  StructuredData::ObjectSP GetLanguageInfo();
+
   /// Get the frame's demangled name.
   ///
   ///  /// \return

lldb/source/API/SBFrame.cpp

@@ -47,6 +47,7 @@
 #include "lldb/API/SBExpressionOptions.h"
 #include "lldb/API/SBFormat.h"
 #include "lldb/API/SBStream.h"
+#include "lldb/API/SBStructuredData.h"
 #include "lldb/API/SBSymbolContext.h"
 #include "lldb/API/SBThread.h"
 #include "lldb/API/SBValue.h"
@@ -1154,6 +1155,21 @@ lldb::SBValue SBFrame::EvaluateExpression(const char *expr,
   return expr_result;
 }
 
+SBStructuredData SBFrame::GetLanguageInfo() {
+  LLDB_INSTRUMENT_VA(this);
+
+  SBStructuredData sb_data;
+  std::unique_lock<std::recursive_mutex> lock;
+  ExecutionContext exe_ctx(m_opaque_sp.get(), lock);
+  StackFrame *frame = exe_ctx.GetFramePtr();
+  if (!frame)
+    return sb_data;
+
+  StructuredData::ObjectSP data(frame->GetLanguageInfo());
+  sb_data.m_impl_up->SetObjectSP(data);
+  return sb_data;
+}
+
 bool SBFrame::IsInlined() {
   LLDB_INSTRUMENT_VA(this);
 

lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntimeV2.cpp

@@ -3398,6 +3398,13 @@ std::optional<uint64_t> AppleObjCRuntimeV2::GetSharedCacheImageHeaderVersion() {
   return std::nullopt;
 }
 
+StructuredData::ObjectSP AppleObjCRuntimeV2::GetLanguageInfo(SymbolContext sc) {
+  auto dict_up = std::make_unique<StructuredData::Dictionary>();
+  dict_up->AddItem("Objective-C runtime version",
+                   std::make_unique<StructuredData::UnsignedInteger>(2));
+  return dict_up;
+}
+
 #pragma mark Frame recognizers
 
 class ObjCExceptionRecognizedStackFrame : public RecognizedStackFrame {

lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntimeV2.h

@@ -106,6 +106,8 @@ class AppleObjCRuntimeV2 : public AppleObjCRuntime {
 
   std::optional<uint64_t> GetSharedCacheImageHeaderVersion();
 
+  StructuredData::ObjectSP GetLanguageInfo(SymbolContext sc) override;
+
 protected:
   lldb::BreakpointResolverSP
   CreateExceptionResolver(const lldb::BreakpointSP &bkpt, bool catch_bp,

lldb/source/Target/LanguageRuntime.cpp

@@ -277,6 +277,10 @@ LanguageRuntime::GetRuntimeUnwindPlan(Thread &thread, RegisterContext *regctx,
   return UnwindPlanSP();
 }
 
+StructuredData::ObjectSP LanguageRuntime::GetLanguageInfo(SymbolContext sc) {
+  return {};
+}
+
 void LanguageRuntime::InitializeCommands(CommandObject *parent) {
   if (!parent)
     return;

lldb/source/Target/StackFrame.cpp

@@ -22,6 +22,7 @@
 #include "lldb/Symbol/VariableList.h"
 #include "lldb/Target/ABI.h"
 #include "lldb/Target/ExecutionContext.h"
+#include "lldb/Target/LanguageRuntime.h"
 #include "lldb/Target/Process.h"
 #include "lldb/Target/RegisterContext.h"
 #include "lldb/Target/StackFrameRecognizer.h"
@@ -1230,6 +1231,18 @@ bool StackFrame::IsHidden() {
   return false;
 }
 
+StructuredData::ObjectSP StackFrame::GetLanguageInfo() {
+  auto process_sp = CalculateProcess();
+  SourceLanguage language = GetLanguage();
+  if (!language)
+    return {};
+  if (auto runtime_sp =
+          process_sp->GetLanguageRuntime(language.AsLanguageType()))
+    return runtime_sp->GetLanguageInfo(
+        GetSymbolContext(eSymbolContextFunction));
+  return {};
+}
+
 const char *StackFrame::GetFunctionName() {
   const char *name = nullptr;
   SymbolContext sc = GetSymbolContext(

lldb/test/API/lang/objc/languageinfo/Makefile

@@ -0,0 +1,4 @@
+OBJC_SOURCES := main.m
+LD_EXTRAS := -lobjc
+
+include Makefile.rules