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1Build systems 2############# 3 4Building with setuptools 5======================== 6 7For projects on PyPI, building with setuptools is the way to go. Sylvain Corlay 8has kindly provided an example project which shows how to set up everything, 9including automatic generation of documentation using Sphinx. Please refer to 10the [python_example]_ repository. 11 12.. [python_example] https://github.com/pybind/python_example 13 14Building with cppimport 15======================== 16 17 cppimport is a small Python import hook that determines whether there is a C++ 18 source file whose name matches the requested module. If there is, the file is 19 compiled as a Python extension using pybind11 and placed in the same folder as 20 the C++ source file. Python is then able to find the module and load it. 21 22.. [cppimport] https://github.com/tbenthompson/cppimport 23 24.. _cmake: 25 26Building with CMake 27=================== 28 29For C++ codebases that have an existing CMake-based build system, a Python 30extension module can be created with just a few lines of code: 31 32.. code-block:: cmake 33 34 cmake_minimum_required(VERSION 2.8.12) 35 project(example) 36 37 add_subdirectory(pybind11) 38 pybind11_add_module(example example.cpp) 39 40This assumes that the pybind11 repository is located in a subdirectory named 41:file:`pybind11` and that the code is located in a file named :file:`example.cpp`. 42The CMake command ``add_subdirectory`` will import a function with the signature 43``pybind11_add_module(<name> source1 [source2 ...])``. It will take care of all 44the details needed to build a Python extension module on any platform. 45 46The target Python version can be selected by setting the ``PYBIND11_PYTHON_VERSION`` 47variable before adding the pybind11 subdirectory. Alternatively, an exact Python 48installation can be specified by setting ``PYTHON_EXECUTABLE``. 49 50A working sample project, including a way to invoke CMake from :file:`setup.py` for 51PyPI integration, can be found in the [cmake_example]_ repository. 52 53.. [cmake_example] https://github.com/pybind/cmake_example 54 55For CMake-based projects that don't include the pybind11 56repository internally, an external installation can be detected 57through `find_package(pybind11 ... CONFIG ...)`. See the `Config file 58<https://github.com/pybind/pybind11/blob/master/tools/pybind11Config.cmake.in>`_ 59docstring for details of relevant CMake variables. 60 61Once detected, and after setting any variables to guide Python and 62C++ standard detection, the aforementioned ``pybind11_add_module`` 63wrapper to ``add_library`` can be employed as described above (after 64``include(pybind11Tools)``). This procedure is available when using CMake 65>= 2.8.12. A working example can be found at [test_installed_module]_ . 66 67.. code-block:: cmake 68 69 cmake_minimum_required(VERSION 2.8.12) 70 project(example) 71 72 find_package(pybind11 REQUIRED) 73 pybind11_add_module(example example.cpp) 74 75.. [test_installed_module] https://github.com/pybind/pybind11/blob/master/tests/test_installed_module/CMakeLists.txt 76 77When using a version of CMake greater than 3.0, pybind11 can 78additionally be used as a special *interface library* following the 79call to ``find_package``. CMake variables to guide Python and C++ 80standard detection should be set *before* ``find_package``. When 81``find_package`` returns, the target ``pybind11::pybind11`` is 82available with pybind11 headers, Python headers and libraries as 83needed, and C++ compile definitions attached. This target is suitable 84for linking to an independently constructed (through ``add_library``, 85not ``pybind11_add_module``) target in the consuming project. A working 86example can be found at [test_installed_target]_ . 87 88.. code-block:: cmake 89 90 cmake_minimum_required(VERSION 3.0) 91 project(example) 92 93 add_library(example MODULE main.cpp) 94 95 find_package(pybind11 REQUIRED) 96 target_link_libraries(example PRIVATE pybind11::pybind11) 97 set_target_properties(example PROPERTIES PREFIX "${PYTHON_MODULE_PREFIX}" 98 SUFFIX "${PYTHON_MODULE_EXTENSION}") 99 100.. warning:: 101 102 Since pybind11 is a metatemplate library, it is crucial that certain 103 compiler flags are provided to ensure high quality code generation. In 104 contrast to the ``pybind11_add_module()`` command, the CMake interface 105 library only provides the *minimal* set of parameters to ensure that the 106 code using pybind11 compiles, but it does **not** pass these extra compiler 107 flags (i.e. this is up to you). 108 109 These include Link Time Optimization (``-flto`` on GCC/Clang/ICPC, ``/GL`` 110 and ``/LTCG`` on Visual Studio). Default-hidden symbols on GCC/Clang/ICPC 111 (``-fvisibility=hidden``) and .OBJ files with many sections on Visual Studio 112 (``/bigobj``). The :ref:`FAQ <faq:symhidden>` contains an 113 explanation on why these are needed. 114 115.. [test_installed_target] https://github.com/pybind/pybind11/blob/master/tests/test_installed_target/CMakeLists.txt 116 117