Load CppInterOp explicitly and resolve it relative to libcppjit

CMakeLists.txt

@@ -95,10 +95,11 @@ execute_process(
     OUTPUT_STRIP_TRAILING_WHITESPACE
 )
 if(_python_platlib)
-    set(CPPINTEROP_INSTALL_DIR "${_python_platlib}/cppjit_backend")
+    set(CPPINTEROP_INSTALL_PREFIX "${_python_platlib}")
 else()
-    set(CPPINTEROP_INSTALL_DIR "${CMAKE_INSTALL_PREFIX}/cppjit_backend")
+    set(CPPINTEROP_INSTALL_PREFIX "${CMAKE_INSTALL_PREFIX}")
 endif()
+set(CPPINTEROP_INSTALL_DIR "${CPPINTEROP_INSTALL_PREFIX}/cppjit_backend")
 
 # Include cmake for CppInterOp config and build using ExternalProject.
 include(${CMAKE_CURRENT_SOURCE_DIR}/cmake/AddCppInterOp.cmake)
@@ -114,11 +115,12 @@ set(INTEROP_SOURCES
 add_library(cppjit SHARED ${CPYRT_SOURCES} ${INTEROP_SOURCES})
 add_dependencies(cppjit CppInterOp)
 
-# The exact library file the wrapper dlopens and the include dir the
-# interpreter boot requires.
+# The wrapper anchors these relative spellings at its own load location,
+# falling back to the install prefix (see cppinterop_paths()).
 target_compile_definitions(cppjit PRIVATE
-    CPPINTEROP_LIBRARY="${CPPINTEROP_INSTALL_DIR}/lib/libclangCppInterOp${CMAKE_SHARED_LIBRARY_SUFFIX}"
-    CPPINTEROP_INCLUDE_DIR="${CPPINTEROP_INSTALL_DIR}/include"
+    CPPINTEROP_INSTALL_PREFIX="${CPPINTEROP_INSTALL_PREFIX}"
+    CPPINTEROP_LIBRARY="cppjit_backend/lib/libclangCppInterOp${CMAKE_SHARED_LIBRARY_SUFFIX}"
+    CPPINTEROP_INCLUDE_DIR="cppjit_backend/include"
 )
 
 target_include_directories(cppjit PRIVATE

python/cppjit/_cpython_cppjit.py

@@ -1,7 +1,7 @@
 """CPython-specific touch-ups"""
 
 import ctypes
-import sys
+import importlib.util
 
 from . import _stdcpp_fix  # noqa: F401
 
@@ -17,42 +17,17 @@
     "_end_capture_stderr",
 ]
 
-# the merged libcppjit extension is the backend: importing it loads the
-# C++ runtime (no separate loader.load_cpp_backend() step, which would
-# initialize the interpreter twice)
-import libcppjit as _backend
-
-# explicitly expose APIs from libcppjit
-_w = ctypes.CDLL(_backend.__file__, ctypes.RTLD_GLOBAL)
-
-
-# some beautification for inspect (only on p2)
-if sys.hexversion < 0x3000000:
-    # TODO: this reliese on CPPOverload cooking up a func_code object, which atm
-    # is simply not implemented for p3 :/
-
-    # convince inspect that cppjit method proxies are possible drop-ins for python
-    # methods and classes for pydoc
-    import inspect
-
-    inspect._old_isfunction = inspect.isfunction
-
-    def isfunction(object):
-        if isinstance(object, _backend.CPPOverload) and not object.im_class:
-            return True
-        return inspect._old_isfunction(object)
-
-    inspect.isfunction = isfunction
-
-    inspect._old_ismethod = inspect.ismethod
-
-    def ismethod(object):
-        if isinstance(object, _backend.CPPOverload):
-            return True
-        return inspect._old_ismethod(object)
-
-    inspect.ismethod = ismethod
-    del isfunction, ismethod
+# preload the merged extension with ctypes and run LoadCppInterOp() first,
+# so the interpreter is ready before the extension module initializes
+_spec = importlib.util.find_spec("libcppjit")
+if _spec is None or not _spec.origin:
+    raise ImportError("cannot locate the libcppjit extension module")
+_w = ctypes.CDLL(_spec.origin, ctypes.RTLD_GLOBAL)
+if not _w.LoadCppInterOp():
+    raise RuntimeError("failed to load CppInterOp (LoadCppInterOp returned 0)")
+del _spec
+
+import libcppjit as _backend  # noqa: E402
 
 
 ### template support ---------------------------------------------------------