Add standalone lib build with Python install

CMakeLists.txt

@@ -16,11 +16,23 @@ project(kenlm)
 option(FORCE_STATIC "Build static executables" OFF)
 option(COMPILE_TESTS "Compile tests" OFF)
 option(ENABLE_PYTHON "Build Python bindings" OFF)
+option(BUILD_PYTHON_STANDALONE "Build standalone C++ lib with Python install" OFF)
 # Eigen3 less than 3.1.0 has a race condition: http://eigen.tuxfamily.org/bz/show_bug.cgi?id=466
 find_package(Eigen3 3.1.0 CONFIG)
 include(CMakeDependentOption)
 cmake_dependent_option(ENABLE_INTERPOLATE "Build interpolation program (depends on Eigen3)" ON "EIGEN3_FOUND AND NOT WIN32" OFF)
 
+set(KENLM_MAX_ORDER 6 CACHE STRING "Maximum supported ngram order")
+
+if (BUILD_PYTHON_STANDALONE)
+  # Build a shared lib artifact in the same way the cpython setup.py builds
+  # and return. That lib can be dlopened by other Python packages that need
+  # cpp artifacts and can't use the bits compiled by setuptools Extension
+  include(${CMAKE_CURRENT_LIST_DIR}/python/BuildStandalone.cmake)
+  return()
+endif()
+
+
 if (FORCE_STATIC)
   #presumably overkill, is there a better way?
   #http://cmake.3232098.n2.nabble.com/Howto-compile-static-executable-td5580269.html

lm/CMakeLists.txt

@@ -36,7 +36,6 @@ target_link_libraries(kenlm PUBLIC kenlm_util Threads::Threads)
 # Since headers are relative to `include/kenlm` at install time, not just `include`
 target_include_directories(kenlm PUBLIC $<INSTALL_INTERFACE:include/kenlm>)
 
-set(KENLM_MAX_ORDER 6 CACHE STRING "Maximum supported ngram order")
 target_compile_definitions(kenlm PUBLIC -DKENLM_MAX_ORDER=${KENLM_MAX_ORDER})
 
 # This directory has children that need to be processed

pyproject.toml

@@ -0,0 +1,2 @@
+[build-system]
+requires = ["setuptools", "wheel", "cmake"]

python/BuildStandalone.cmake

@@ -0,0 +1,41 @@
+cmake_minimum_required(VERSION 3.1)
+
+file(GLOB
+  KENLM_PYTHON_STANDALONE_SRCS
+  "util/*.cc"
+  "lm/*.cc"
+  "util/double-conversion/*.cc"
+  "python/*.cc"
+  )
+
+list(FILTER KENLM_PYTHON_STANDALONE_SRCS EXCLUDE REGEX ".*main.cc")
+list(FILTER KENLM_PYTHON_STANDALONE_SRCS EXCLUDE REGEX ".*test.cc")
+
+add_library(
+  kenlm
+  SHARED
+  ${KENLM_PYTHON_STANDALONE_SRCS}
+  )
+
+target_include_directories(kenlm PRIVATE ${PROJECT_SOURCE_DIR})
+target_compile_definitions(kenlm PRIVATE KENLM_MAX_ORDER=${KENLM_MAX_ORDER})
+
+find_package(ZLIB)
+find_package(BZip2)
+find_package(LibLZMA)
+
+if (ZLIB_FOUND)
+  target_link_libraries(kenlm PRIVATE ${ZLIB_LIBRARIES})
+  target_include_directories(kenlm PRIVATE ${ZLIB_INCLUDE_DIRS})
+  target_compile_definitions(kenlm PRIVATE HAVE_ZLIB)
+endif()
+if(BZIP2_FOUND)
+  target_link_libraries(kenlm PRIVATE ${BZIP2_LIBRARIES})
+  target_include_directories(kenlm PRIVATE ${BZIP2_INCLUDE_DIR})
+  target_compile_definitions(kenlm PRIVATE HAVE_BZLIB)
+endif()
+if(LIBLZMA_FOUND)
+  target_link_libraries(kenlm PRIVATE ${LIBLZMA_LIBRARIES})
+  target_include_directories(kenlm PRIVATE ${LIBLZMA_INCLUDE_DIRS})
+  target_compile_definitions(kenlm PRIVATE HAVE_LZMA)
+endif()

setup.py

@@ -1,9 +1,12 @@
 from setuptools import setup, Extension
+from setuptools.command.build_ext import build_ext as _build_ext
 import glob
 import platform
+import subprocess
 import os
 import sys
 import re
+from pathlib import Path
 
 #Does gcc compile with this header and library?
 def compile_test(header, library):
@@ -28,10 +31,6 @@ def compile_test(header, library):
     ARGS.append('-DHAVE_CLOCKGETTIME')
 elif platform.system() == 'Darwin':
     LIBS = ['c++']
-    # Build a dylib on macOS
-    import sysconfig
-    vars = sysconfig.get_config_vars()
-    vars['LDSHARED'] = vars['LDSHARED'].replace('-bundle', '-dynamiclib')
 else:
     LIBS = []
 
@@ -51,17 +50,71 @@ def compile_test(header, library):
     ARGS.append('-DHAVE_XZLIB')
     LIBS.append('lzma')
 
+
+class build_ext(_build_ext):
+    def run(self):
+        try:
+            out = subprocess.check_output(["cmake", "--version"])
+        except OSError:
+            raise RuntimeError(
+                "CMake must be installed to build the following extensions: "
+                + ", ".join(e.name for e in self.extensions)
+            )
+
+        ext_dir = str(Path(self.get_ext_fullpath('libkenlm')).absolute().parent)
+        source_dir = str(Path(__file__).absolute().parent)
+
+        cmake_args = [
+            "-DCMAKE_LIBRARY_OUTPUT_DIRECTORY=" + ext_dir,
+            "-DBUILD_SHARED_LIBS=ON",
+            "-DBUILD_PYTHON_STANDALONE=ON",
+        ]
+        cfg = "Debug" if self.debug else "Release"
+        build_args = ["--config", cfg]
+
+        if platform.system() == "Windows":
+            cmake_args += [
+                "-DCMAKE_WINDOWS_EXPORT_ALL_SYMBOLS=ON",
+                "-DCMAKE_RUNTIME_OUTPUT_DIRECTORY_{}={}".format(cfg.upper(), ext_dir),
+                "-DCMAKE_LIBRARY_OUTPUT_DIRECTORY_{}={}".format(cfg.upper(), ext_dir),
+                "-DCMAKE_ARCHIVE_OUTPUT_DIRECTORY_{}={}".format(cfg.upper(), ext_dir),
+            ]
+            if sys.maxsize > 2**32:
+                cmake_args += ["-A", "x64"]
+            build_args += ["--", "/m"]
+        else:
+            cmake_args += ["-DCMAKE_BUILD_TYPE=" + cfg]
+            build_args += ["--", "-j4"]
+
+        env = os.environ.copy()
+        env["CXXFLAGS"] = '{} -fPIC -DVERSION_INFO=\\"{}\\"'.format(
+            env.get("CXXFLAGS", ""), self.distribution.get_version()
+        )
+
+        if not os.path.exists(self.build_temp):
+            os.makedirs(self.build_temp)
+        subprocess.check_call(
+            ["cmake", source_dir] + cmake_args, cwd=self.build_temp, env=env
+        )
+        subprocess.check_call(
+            ["cmake", "--build", "."] + build_args, cwd=self.build_temp
+        )
+
+        return _build_ext.run(self)
+
+
 ext_modules = [
     Extension(name='kenlm',
         sources=FILES + ['python/kenlm.cpp'],
         language='C++', 
         include_dirs=['.'],
         libraries=LIBS, 
-        extra_compile_args=ARGS)
+        extra_compile_args=ARGS),
 ]
 
 setup(
     name='kenlm',
     ext_modules=ext_modules,
+    cmdclass={"build_ext": build_ext},
     include_package_data=True,
 )