From 2d038e75f680fb8e889ac1db859689ec2860d33b Mon Sep 17 00:00:00 2001
From: Aaron Jomy <aaronjomyjoseph@gmail.com>
Date: Mon, 4 Nov 2024 13:42:45 +0100
Subject: [PATCH] [TCling] Invoke InterOp interpreter API in metacling

This uses provides InterOp with the TInterpreter instance created by ROOT in TCling.
The InterOp API can now be used without providing interpreter ownership.
---
 core/metacling/src/CMakeLists.txt     | 1 -
 core/metacling/src/TCling.cxx         | 8 ++++++++
 core/metacling/src/TClingCallFunc.cxx | 2 ++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/core/metacling/src/CMakeLists.txt b/core/metacling/src/CMakeLists.txt
index 9c5b2616f577a..1104d8346c509 100644
--- a/core/metacling/src/CMakeLists.txt
+++ b/core/metacling/src/CMakeLists.txt
@@ -76,7 +76,6 @@ if(MSVC)
 endif()
 
 add_dependencies(MetaCling CLING clangCppInterOp)
-# target_include_directories(MetaCling SYSTEM PUBLIC ${source_dir}/include/)
 
 ##### libCling #############################################################
 
diff --git a/core/metacling/src/TCling.cxx b/core/metacling/src/TCling.cxx
index e831914ad0426..b7a90d4f26174 100644
--- a/core/metacling/src/TCling.cxx
+++ b/core/metacling/src/TCling.cxx
@@ -115,6 +115,8 @@ clang/LLVM technology.
 #include "cling/Utils/SourceNormalization.h"
 #include "cling/Interpreter/Exception.h"
 
+#include "clang/Interpreter/CppInterOp.h"
+
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/Module.h"
 
@@ -1609,6 +1611,12 @@ TCling::TCling(const char *name, const char *title, const char* const argv[], vo
       // Initialize the dyld for AutoloadLibraryGenerator.
       DLM.initializeDyld(ShouldPermanentlyIgnore);
    }
+
+   // Tell CppInterOp that the cling::Interpreter instance is managed externally by ROOT
+   // We pass the handle so it sets the ownership flags and sets the interpreter as soon as TCling is initialized 
+   if (!Cpp::GetInterpreter()) {
+      Cpp::UseExternalInterpreter((Cpp::TInterp_t*)fInterpreter.get());
+   }
 }
 
 
diff --git a/core/metacling/src/TClingCallFunc.cxx b/core/metacling/src/TClingCallFunc.cxx
index 7387068e938ee..5772966c1c9f5 100644
--- a/core/metacling/src/TClingCallFunc.cxx
+++ b/core/metacling/src/TClingCallFunc.cxx
@@ -67,6 +67,8 @@ C++ interpreter and the Clang C++ compiler, not CINT.
 
 #include "clang/Sema/SemaInternal.h"
 
+#include "clang/Interpreter/CppInterOp.h"
+
 #include <map>
 #include <string>
 #include <sstream>