cmake - build without Python libraries on Unix

Andrej730 · Andrej730 · commit c8a4f1bbd27c · 2025-10-28T17:17:19.000+05:00
diff --git a/nix/build-all.py b/nix/build-all.py
@@ -54,7 +54,7 @@
     - ``USE_OCCT`` - whether to use official Open CASCADE instead of Community Edition
     (`true` by default, any other value is considered `false`)
     - ``WASM_PYTHON_PATH`` - path to WASM Python installation,
-    used to deduce `PYMAJOR`, `PYMINOR`, `PYMICRO`, `TARGETINSTALLDIR`, `PYTHONINCLUDE`,
+    used to deduce `PYVERSION` (e.g. '3.13.2'), `PYTHONINCLUDE`,
     `SIDE_MODULE_CFLAGS`, `SIDE_MODULE_LDFLAGS`.
     Allows to build wasm without pyodide build environment, which can be useful for debugging build issues.
     Example value: 'pyodide/cpython/installs/python-3.13.2'
@@ -216,27 +216,19 @@ def cecho(message, color=NO_COLOR):
         wasm_python_path = os.environ["WASM_PYTHON_PATH"]
         # Deduce version from path, assuming format .../python-X.Y.Z
         version_match = re.search(r"python-(\d+)\.(\d+)\.(\d+)", wasm_python_path)
-        if version_match:
-            os.environ["PYMAJOR"] = version_match.group(1)
-            os.environ["PYMINOR"] = version_match.group(2)
-            os.environ["PYMICRO"] = version_match.group(3)
-        os.environ["TARGETINSTALLDIR"] = wasm_python_path
-        os.environ["PYTHONINCLUDE"] = (
-            f"{wasm_python_path}/include/python{os.environ['PYMAJOR']}.{os.environ['PYMINOR']}"
-        )
+        assert version_match, f"Could not deduce python version from '{wasm_python_path}'"
+        python_version = version_match.group(1)
+        os.environ["PYVERSION"] = python_version
+        os.environ["PYTHONINCLUDE"] = f"{wasm_python_path}/include/python{python_version.rpartition('.')[0]}"
         os.environ["SIDE_MODULE_CFLAGS"] = ""
         # Required, otherwise library will compile as .a, not .so.
         os.environ["SIDE_MODULE_LDFLAGS"] = "-s SIDE_MODULE=1"
         # We're outside pyodide build environment, so need to provide toolchain file ourselves.
         assert "WASM_TOOLCHAIN_FILE" in os.environ, "WASM_TOOLCHAIN_FILE must be set when WASM_PYTHON_PATH is provided"
         WASM_DEBUG = True
     required_vars = (
-        "PYMAJOR",
-        "PYMINOR",
-        "PYMICRO",
-        # Folder where WASM-Python was installed.
-        # e.g '/pyodide/cpython/installs/python-3.13.2'.
-        "TARGETINSTALLDIR",
+        # E.g. '3.13.2'.
+        "PYVERSION",
         # 'include' folder in WASM-Python installation.
         # e.g. '/pyodide/cpython/installs/python-3.13.2/include/python3.13'
         "PYTHONINCLUDE",
@@ -1448,15 +1440,14 @@ def get_cmake_args_prefix_path(additional_paths: "Sequence[str]" = ()) -> "list[
 
     def compile_python_wrapper(
         python_version: str,
-        python_library: Union[str, None] = None,
         python_include: Union[str, None] = None,
         python_executable: Union[str, None] = None,
         python_path: Union[Path, None] = None,
     ) -> Union[str, None]:
         """
         :return: Path to module dir if ``python_executable`` was provided, otherwise ``None``.
         """
-        assert bool(python_path) ^ bool(python_library and python_include)
+        assert bool(python_path) ^ bool(python_include)
 
         logger.info(f"\rConfiguring python {python_version} wrapper...")
 
@@ -1469,7 +1460,7 @@ def compile_python_wrapper(
             prefix_paths.append(f"{DEPS_DIR}/install/swig")
         if python_path:
             # We couldn't just prefix PATH and have to provide all variables explicitly,
-            # see run-cmake.bat note for details.
+            # see ifcwrap/cmake for the details.
             python_executable = (Path(python_path) / "bin" / "python3").__str__()
             python_include = run(
                 [
@@ -1478,20 +1469,8 @@ def compile_python_wrapper(
                     "import sysconfig; print(sysconfig.get_config_var('INCLUDEPY'))",
                 ]
             )
-            python_library = run(
-                [
-                    python_executable,
-                    "-c",
-                    "import sysconfig, pathlib; "
-                    "lib_dir = pathlib.Path(sysconfig.get_config_var('LIBDIR')); "
-                    "print((lib_dir / sysconfig.get_config_var('LIBRARY')).__str__())",
-                ]
-            )
-            if platform.system() == "Darwin":
-                # Oddly on Mac `LIBRARY` returns .a that doesn't even exists.
-                python_library = Path(python_library).with_suffix(".dylib").__str__()
 
-        assert python_library and python_include
+        assert python_include
         run_cmake(
             "",
             cmake_args
@@ -1500,7 +1479,6 @@ def compile_python_wrapper(
                 *([f"-DPYTHON_EXECUTABLE={python_executable}"] if python_executable else []),
                 # Needed because pyodide is expecting setup.py to be in the root.
                 *([f"-DPYTHON_MODULE_INSTALL_DIR={REPO_PATH}"] * WASM),
-                f"-DPYTHON_LIBRARY={python_library}",
                 f"-DPYTHON_INCLUDE_DIR={python_include}",
                 f"-DCMAKE_INSTALL_PREFIX={DEPS_DIR}/install/ifcopenshell/tmp",
                 "-DUSERSPACE_PYTHON_PREFIX="
@@ -1538,26 +1516,13 @@ def compile_python_wrapper(
             return module_dir
 
     if "wasm" in flags:
-        compile_python_wrapper(
-            f"{os.environ['PYMAJOR']}.{os.environ['PYMINOR']}.{os.environ['PYMICRO']}",
-            f"{os.environ['TARGETINSTALLDIR']}/lib/libpython{os.environ['PYMAJOR']}.{os.environ['PYMINOR']}.a",
-            os.environ["PYTHONINCLUDE"],
-            None,
-        )
+        compile_python_wrapper(os.environ["PYVERSION"], os.environ["PYTHONINCLUDE"])
         # Copy setup.py where pyodide build system expects it.
         shutil.copy(REPO_PATH / "pyodide" / "setup.py", REPO_PATH)
 
     elif USE_CURRENT_PYTHON_VERSION:
         python_info = sysconfig.get_paths()
-
-        py_path_components = [sysconfig.get_config_var("LIBDIR"), sysconfig.get_config_var("INSTSONAME")]
-
-        if sysconfig.get_config_var("multiarchsubdir"):
-            py_path_components.insert(1, sysconfig.get_config_var("multiarchsubdir").replace("/", ""))
-
-        python_lib = os.path.join(*py_path_components)
-
-        compile_python_wrapper(platform.python_version(), python_lib, python_info["include"], sys.executable)
+        compile_python_wrapper(platform.python_version(), python_info["include"], sys.executable)
     else:
         for python_version in PYTHON_VERSIONS:
             python_path = Path(DEPS_DIR) / "install" / f"python-{python_version}"
diff --git a/src/ifcwrap/CMakeLists.txt b/src/ifcwrap/CMakeLists.txt
@@ -46,17 +46,20 @@ IF(NOT "${PYTHON_LIBRARY}" STREQUAL "")
     MESSAGE(STATUS "Looking for Python library file in: ${Python_LIBRARY}")
 ENDIF()
 
-# NOTE PYTHONLIBS_FOUND and PYTHONINTERP_FOUND cannot seem to be trusted so
-# we need further checks to see whether the packages were actually found or not.
-FIND_PACKAGE(Python COMPONENTS Development)
-IF(NOT Python_Development_FOUND)
+# Development.Module = headers on Unix, headers+libraries on Windows.
+# Required variables:
+# - Windows - Python_INCLUDE_DIR, Python_LIBRARY (MSVC doesn't allow undefined symbols at link time)
+# - Unix - Python_INCLUDE_DIR
+# Unfortunately all paths must be always provided explicitly, not by prefixing PATH.
+# Otherwise FindPython will break on newer Python versions (list of supported versions is hardcoded).
+find_package(Python COMPONENTS Development.Module)
+IF(NOT Python_Development.Module_FOUND)
 	MESSAGE(FATAL_ERROR "BUILD_IFCPYTHON enabled, but unable to find Python lib or header. Disable BUILD_IFCPYTHON or fix Python paths to proceed.")
 ENDIF()
 
 # Ensure version is saved here, from wasm libraries,
 # not from Python interpreter that might be unrelated to pyodide Python version.
 set(_python_libs_version "${Python_VERSION_MAJOR}${Python_VERSION_MINOR}")
-INCLUDE_DIRECTORIES(${Python_INCLUDE_DIRS})
 INCLUDE_DIRECTORIES(BEFORE ${CMAKE_CURRENT_SOURCE_DIR})
 
 SET(CMAKE_SWIG_FLAGS ${SWIG_DEFINES})
@@ -90,6 +93,7 @@ SET_PROPERTY(
 set(SWIG_MODULE_ifcopenshell_wrapper_EXTRA_FLAGS "-interface" "_ifcopenshell_wrapper")
 
 swig_add_library(ifcopenshell_wrapper LANGUAGE python SOURCES IfcPython.i)
+swig_link_libraries(ifcopenshell_wrapper PRIVATE Python::Module)
 SET_PROPERTY(TARGET ${SWIG_MODULE_ifcopenshell_wrapper_REAL_NAME} PROPERTY SWIG_DEPENDS ${IFCOPENSHELL_LIBRARIES})
 if (WASM_BUILD)
     # SIDE_MODULE=1 - add to .so all symbols from linked archives (default used by pyodide).
@@ -113,9 +117,9 @@ if (WASM_BUILD)
 endif()
 if("$ENV{LDFLAGS}" MATCHES ".undefined.suppress")
 # On osx there is some state in the python dylib. With `-Wl,undefined,suppress` we can ignore the missing symbols at compile time.
-SWIG_LINK_LIBRARIES(ifcopenshell_wrapper ${IFCOPENSHELL_LIBRARIES} ${OPENCASCADE_LIBRARIES} ${Boost_LIBRARIES} ${LIBSVGFILL})
+swig_link_libraries(ifcopenshell_wrapper PRIVATE ${IFCOPENSHELL_LIBRARIES} ${OPENCASCADE_LIBRARIES} ${Boost_LIBRARIES} ${LIBSVGFILL})
 else()
-SWIG_LINK_LIBRARIES(ifcopenshell_wrapper ${IFCOPENSHELL_LIBRARIES} ${Python_LIBRARIES} ${LIBSVGFILL})
+swig_link_libraries(ifcopenshell_wrapper PRIVATE ${IFCOPENSHELL_LIBRARIES} ${LIBSVGFILL})
 endif()
 if ((NOT WIN32) AND BUILD_SHARED_LIBS)
     SET_INSTALL_RPATHS(${SWIG_MODULE_ifcopenshell_wrapper_REAL_NAME} "${IFCDIRS};${OCC_LIBRARY_DIR}")
diff --git a/win/run-cmake.bat b/win/run-cmake.bat
@@ -92,10 +92,6 @@ set LIBXML2_INCLUDE_DIR=%DEPS_DIR%\OpenCOLLADA\Externals\LibXML\include
 set LIBXML2_LIBRARIES=%INSTALL_DIR%\OpenCOLLADA\lib\opencollada\xml.lib
 set HDF5_INSTALL_DIR=%INSTALL_DIR%\HDF5-%HDF5_VERSION%-win%ARCH_BITS%
 
-:: Unfortunately we have to provide all 3 paths explicitly,
-:: because if just prefix PATH, then FindPython will have an issue with newer versions of Python.
-:: E.g. older FindPython that didn't s added explicit support for Python 3.14 will fail to find.
-:: So setting paths expliicitly is more robust.
 set PYTHON_EXECUTABLE=%PYTHONHOME%\python.exe
 for /f "usebackq delims=" %%v in (`
     call "%PYTHON_EXECUTABLE%" -c "import sys; print(f'{sys.version_info[0]}{sys.version_info[1]}')"
