Cython、CMake和setup.py、python在一个子目录下编译两次

我正在尝试按照以下结构与 Cython 绑定一起构建 C++ 库https://bloerg.net/2012/11/10/cmake-and-distutils.html https://bloerg.net/2012/11/10/cmake-and-distutils.html.

问题是，期间make install，扩展将被编译两次。当只有一个 main 时，不会发生这种双重编译CMakeLists.txt在主文件夹中（调整路径）。详细信息如下：

我的项目结构是

.
├── CMakeLists.txt
├── python
│   ├── CMakeLists.txt
│   ├── a_py.pxd
│   ├── a_py.pyx
│   └── setup.py.in
└── src
    ├── A.cpp
    └── A.h

顶层CMakeLists.txt仅包含add_subdirectory(python).

python/CMakeLists.txt is

IF(NOT ${PYTHON})
    find_program(PYTHON "python")
ENDIF()

set(SETUP_PY_IN "${CMAKE_CURRENT_SOURCE_DIR}/setup.py.in")
set(SETUP_PY    "${CMAKE_CURRENT_BINARY_DIR}/setup.py")

set(PY_OUTPUT      "${CMAKE_CURRENT_BINARY_DIR}/build/pytimestamp")

configure_file(
    ${SETUP_PY_IN}
    ${SETUP_PY}
)

add_custom_command(OUTPUT "${PY_OUTPUT}"
                   COMMAND ${PYTHON} ${SETUP_PY} build_ext
                   COMMAND ${CMAKE_COMMAND} -E touch ${PY_OUTPUT}
               )

add_custom_target(a_py ALL DEPENDS ${PY_OUTPUT})

install(CODE "execute_process(COMMAND ${PYTHON} ${SETUP_PY} install)")

setup.py is:

from distutils.core import setup
from distutils.extension import Extension
from Cython.Distutils import build_ext
ext_modules = [
    Extension(
    name="a",
    sources=["${CMAKE_CURRENT_SOURCE_DIR}/a_py.pyx", "${CMAKE_CURRENT_SOURCE_DIR}/../src/A.cpp"],
    include_dirs = ['${CMAKE_CURRENT_SOURCE_DIR}/../src'],
    language="c++",
    ),
]
setup(
    name = 'a',
    version='${PROJECT_VERSION}',
    cmdclass = {'build_ext': build_ext},
    ext_modules = ext_modules,
    package_dir={ 'a': '${CMAKE_CURRENT_SOURCE_DIR}' },
)

在这两种情况下（CMakeFile.txt在根或在python子文件夹），首先是build_ext步骤运行：

Scanning dependencies of target a_py
[100%] Generating build/pytimestamp
running build_ext

并编译生成的a_py.cpp and A.cpp并链接库。 在安装步骤中，再次运行编译只有当CMakeFile.txt在里面python子文件夹.

这是安装过程中发生的情况：

running build_ext
skipping '/Users/xxx/tmp/ctest/t08/python/a_py.cpp' Cython extension (up-to-date)
building 'a' extension
creating build

请注意，a_py.pyx不会再次进行 cythonized，但会重新创建构建目录（构建和安装步骤之间相同）并且编译文件（使用完全相同的编译器和链接器调用）。

完整的示例可以在这里找到：https://github.com/zeeMonkeez/cmakeCythonTest https://github.com/zeeMonkeez/cmakeCythonTest

我有同样的问题。显然，就我而言，在安装阶段setup.py在构建阶段找不到放置已编译扩展的目录时遇到困难，因此即使使用--skip-build switch.

我通过在构建和安装阶段指定相同的目录路径来解决--build-lib and --build-dir分别切换：

    add_custom_command(OUTPUT ${PY_OUTPUT}
            COMMAND ${PYTHON} ${SETUP_PY} build_ext --build-lib ${CMAKE_CURRENT_BINARY_DIR}/mysoext
            COMMAND ${CMAKE_COMMAND} -E touch ${PY_OUTPUT}
            DEPENDS ${DEPS}
            )
...
        set(MYINSTCMD "\
            EXECUTE_PROCESS(COMMAND ${PYTHON} ${SETUP_PY} install_lib \
            --skip-build \
            --install-dir /my/install/dir \
            --build-dir ${CMAKE_CURRENT_BINARY_DIR}/mysoext)")
        install(CODE "${MYINSTCMD}")