Update threading.cmake

cpp/cmake/threading.cmake

@@ -1,21 +1,52 @@
+# 🚀 MODERN CMAKE: Create an interface library to encapsulate threading logic.
+# This prevents polluting the global scope with definitions and libraries.
+add_library(threading_config INTERFACE)
+
+# ------------------------------------------------------------------------------
+# 1. OPENMP CONFIGURATION
+# ------------------------------------------------------------------------------
 if(MULTITHREADING)
     find_package(OpenMP REQUIRED)
-    message(STATUS "Multithreading is enabled.")
-    link_libraries(OpenMP::OpenMP_CXX)
+    message(STATUS "Multithreading is enabled (OpenMP).")
+
+    # 🛡️ ENCAPSULATION: Only link OpenMP to targets that link 'threading_config'.
+    target_link_libraries(threading_config INTERFACE OpenMP::OpenMP_CXX)
 else()
     message(STATUS "Multithreading is disabled.")
-    add_definitions(-DNO_MULTITHREADING -DBOOST_SP_NO_ATOMIC_ACCESS)
+
+    # ⚡ DEFINITIONS: Pass flags only to consumers of this config.
+    # -DNO_MULTITHREADING: Custom flag likely used in your code.
+    # -DBOOST_SP_NO_ATOMIC_ACCESS: Disables atomic ref-counting in Boost (perf boost for single-thread).
+    target_compile_definitions(threading_config INTERFACE 
+        NO_MULTITHREADING 
+        BOOST_SP_NO_ATOMIC_ACCESS
+    )
 endif()
 
+# ------------------------------------------------------------------------------
+# 2. INTEL TBB CONFIGURATION
+# ------------------------------------------------------------------------------
 if(DISABLE_TBB)
-    message(STATUS "Intel Thread Building Blocks is disabled.")
-    add_definitions(-DNO_TBB)
+    message(STATUS "Intel Thread Building Blocks is disabled (Explicitly).")
+    target_compile_definitions(threading_config INTERFACE NO_TBB)
 else()
+    # QUIET is good, but we need to ensure we actually link it if found.
     find_package(TBB QUIET OPTIONAL_COMPONENTS tbb)
-    if(${TBB_FOUND})
+
+    if(TBB_FOUND)
         message(STATUS "Intel Thread Building Blocks is enabled.")
+
+        # 🛡️ LINKING FIX: Actually link TBB! 
+        # Modern TBB CMake config exports 'TBB::tbb'.
+        if(TARGET TBB::tbb)
+            target_link_libraries(threading_config INTERFACE TBB::tbb)
+        else()
+            # Fallback for older FindTBB modules that rely on variables
+            target_include_directories(threading_config INTERFACE ${TBB_INCLUDE_DIRS})
+            target_link_libraries(threading_config INTERFACE ${TBB_LIBRARIES})
+        endif()
     else()
-        message(STATUS "Could not locate TBB.")
-        add_definitions(-DNO_TBB)
+        message(STATUS "Could not locate TBB (Disabled).")
+        target_compile_definitions(threading_config INTERFACE NO_TBB)
     endif()
 endif()