You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
217 lines
8.8 KiB
217 lines
8.8 KiB
Build systems
|
|
#############
|
|
|
|
Building with setuptools
|
|
========================
|
|
|
|
For projects on PyPI, building with setuptools is the way to go. Sylvain Corlay
|
|
has kindly provided an example project which shows how to set up everything,
|
|
including automatic generation of documentation using Sphinx. Please refer to
|
|
the [python_example]_ repository.
|
|
|
|
.. [python_example] https://github.com/pybind/python_example
|
|
|
|
Building with cppimport
|
|
========================
|
|
|
|
cppimport is a small Python import hook that determines whether there is a C++
|
|
source file whose name matches the requested module. If there is, the file is
|
|
compiled as a Python extension using pybind11 and placed in the same folder as
|
|
the C++ source file. Python is then able to find the module and load it.
|
|
|
|
.. [cppimport] https://github.com/tbenthompson/cppimport
|
|
|
|
.. _cmake:
|
|
|
|
Building with CMake
|
|
===================
|
|
|
|
For C++ codebases that have an existing CMake-based build system, a Python
|
|
extension module can be created with just a few lines of code:
|
|
|
|
.. code-block:: cmake
|
|
|
|
cmake_minimum_required(VERSION 2.8.12)
|
|
project(example)
|
|
|
|
add_subdirectory(pybind11)
|
|
pybind11_add_module(example example.cpp)
|
|
|
|
This assumes that the pybind11 repository is located in a subdirectory named
|
|
:file:`pybind11` and that the code is located in a file named :file:`example.cpp`.
|
|
The CMake command ``add_subdirectory`` will import the pybind11 project which
|
|
provides the ``pybind11_add_module`` function. It will take care of all the
|
|
details needed to build a Python extension module on any platform.
|
|
|
|
A working sample project, including a way to invoke CMake from :file:`setup.py` for
|
|
PyPI integration, can be found in the [cmake_example]_ repository.
|
|
|
|
.. [cmake_example] https://github.com/pybind/cmake_example
|
|
|
|
pybind11_add_module
|
|
-------------------
|
|
|
|
To ease the creation of Python extension modules, pybind11 provides a CMake
|
|
function with the following signature:
|
|
|
|
.. code-block:: cmake
|
|
|
|
pybind11_add_module(<name> [MODULE | SHARED] [EXCLUDE_FROM_ALL]
|
|
[NO_EXTRAS] [THIN_LTO] source1 [source2 ...])
|
|
|
|
This function behaves very much like CMake's builtin ``add_library`` (in fact,
|
|
it's a wrapper function around that command). It will add a library target
|
|
called ``<name>`` to be built from the listed source files. In addition, it
|
|
will take care of all the Python-specific compiler and linker flags as well
|
|
as the OS- and Python-version-specific file extension. The produced target
|
|
``<name>`` can be further manipulated with regular CMake commands.
|
|
|
|
``MODULE`` or ``SHARED`` may be given to specify the type of library. If no
|
|
type is given, ``MODULE`` is used by default which ensures the creation of a
|
|
Python-exclusive module. Specifying ``SHARED`` will create a more traditional
|
|
dynamic library which can also be linked from elsewhere. ``EXCLUDE_FROM_ALL``
|
|
removes this target from the default build (see CMake docs for details).
|
|
|
|
Since pybind11 is a template library, ``pybind11_add_module`` adds compiler
|
|
flags to ensure high quality code generation without bloat arising from long
|
|
symbol names and duplication of code in different translation units. The
|
|
additional flags enable LTO (Link Time Optimization), set default visibility
|
|
to *hidden* and strip unneeded symbols. See the :ref:`FAQ entry <faq:symhidden>`
|
|
for a more detailed explanation. These optimizations are never applied in
|
|
``Debug`` mode. If ``NO_EXTRAS`` is given, they will always be disabled, even
|
|
in ``Release`` mode. However, this will result in code bloat and is generally
|
|
not recommended.
|
|
|
|
As stated above, LTO is enabled by default. Some newer compilers also support
|
|
different flavors of LTO such as `ThinLTO`_. Setting ``THIN_LTO`` will cause
|
|
the function to prefer this flavor if available. The function falls back to
|
|
regular LTO if ``-flto=thin`` is not available.
|
|
|
|
.. _ThinLTO: http://clang.llvm.org/docs/ThinLTO.html
|
|
|
|
Configuration variables
|
|
-----------------------
|
|
|
|
By default, pybind11 will compile modules with the C++14 standard, if available
|
|
on the target compiler, falling back to C++11 if C++14 support is not
|
|
available. Note, however, that this default is subject to change: future
|
|
pybind11 releases are expected to migrate to newer C++ standards as they become
|
|
available. To override this, the standard flag can be given explicitly in
|
|
``PYBIND11_CPP_STANDARD``:
|
|
|
|
.. code-block:: cmake
|
|
|
|
# Use just one of these:
|
|
# GCC/clang:
|
|
set(PYBIND11_CPP_STANDARD -std=c++11)
|
|
set(PYBIND11_CPP_STANDARD -std=c++14)
|
|
set(PYBIND11_CPP_STANDARD -std=c++1z) # Experimental C++17 support
|
|
# MSVC:
|
|
set(PYBIND11_CPP_STANDARD /std:c++14)
|
|
set(PYBIND11_CPP_STANDARD /std:c++latest) # Enables some MSVC C++17 features
|
|
|
|
add_subdirectory(pybind11) # or find_package(pybind11)
|
|
|
|
Note that this and all other configuration variables must be set **before** the
|
|
call to ``add_subdirectory`` or ``find_package``. The variables can also be set
|
|
when calling CMake from the command line using the ``-D<variable>=<value>`` flag.
|
|
|
|
The target Python version can be selected by setting ``PYBIND11_PYTHON_VERSION``
|
|
or an exact Python installation can be specified with ``PYTHON_EXECUTABLE``.
|
|
For example:
|
|
|
|
.. code-block:: bash
|
|
|
|
cmake -DPYBIND11_PYTHON_VERSION=3.6 ..
|
|
# or
|
|
cmake -DPYTHON_EXECUTABLE=path/to/python ..
|
|
|
|
find_package vs. add_subdirectory
|
|
---------------------------------
|
|
|
|
For CMake-based projects that don't include the pybind11 repository internally,
|
|
an external installation can be detected through ``find_package(pybind11)``.
|
|
See the `Config file`_ docstring for details of relevant CMake variables.
|
|
|
|
.. code-block:: cmake
|
|
|
|
cmake_minimum_required(VERSION 2.8.12)
|
|
project(example)
|
|
|
|
find_package(pybind11 REQUIRED)
|
|
pybind11_add_module(example example.cpp)
|
|
|
|
Once detected, the aforementioned ``pybind11_add_module`` can be employed as
|
|
before. The function usage and configuration variables are identical no matter
|
|
if pybind11 is added as a subdirectory or found as an installed package. You
|
|
can refer to the same [cmake_example]_ repository for a full sample project
|
|
-- just swap out ``add_subdirectory`` for ``find_package``.
|
|
|
|
.. _Config file: https://github.com/pybind/pybind11/blob/master/tools/pybind11Config.cmake.in
|
|
|
|
Advanced: interface library target
|
|
----------------------------------
|
|
|
|
When using a version of CMake greater than 3.0, pybind11 can additionally
|
|
be used as a special *interface library* . The target ``pybind11::module``
|
|
is available with pybind11 headers, Python headers and libraries as needed,
|
|
and C++ compile definitions attached. This target is suitable for linking
|
|
to an independently constructed (through ``add_library``, not
|
|
``pybind11_add_module``) target in the consuming project.
|
|
|
|
.. code-block:: cmake
|
|
|
|
cmake_minimum_required(VERSION 3.0)
|
|
project(example)
|
|
|
|
find_package(pybind11 REQUIRED) # or add_subdirectory(pybind11)
|
|
|
|
add_library(example MODULE main.cpp)
|
|
target_link_libraries(example PRIVATE pybind11::module)
|
|
set_target_properties(example PROPERTIES PREFIX "${PYTHON_MODULE_PREFIX}"
|
|
SUFFIX "${PYTHON_MODULE_EXTENSION}")
|
|
|
|
.. warning::
|
|
|
|
Since pybind11 is a metatemplate library, it is crucial that certain
|
|
compiler flags are provided to ensure high quality code generation. In
|
|
contrast to the ``pybind11_add_module()`` command, the CMake interface
|
|
library only provides the *minimal* set of parameters to ensure that the
|
|
code using pybind11 compiles, but it does **not** pass these extra compiler
|
|
flags (i.e. this is up to you).
|
|
|
|
These include Link Time Optimization (``-flto`` on GCC/Clang/ICPC, ``/GL``
|
|
and ``/LTCG`` on Visual Studio). Default-hidden symbols on GCC/Clang/ICPC
|
|
(``-fvisibility=hidden``) and .OBJ files with many sections on Visual Studio
|
|
(``/bigobj``). The :ref:`FAQ <faq:symhidden>` contains an
|
|
explanation on why these are needed.
|
|
|
|
Embedding the Python interpreter
|
|
--------------------------------
|
|
|
|
In addition to extension modules, pybind11 also supports embedding Python into
|
|
a C++ executable or library. In CMake, simply link with the ``pybind11::embed``
|
|
target. It provides everything needed to get the interpreter running. The Python
|
|
headers and libraries are attached to the target. Unlike ``pybind11::module``,
|
|
there is no need to manually set any additional properties here. For more
|
|
information about usage in C++, see :doc:`/advanced/embedding`.
|
|
|
|
.. code-block:: cmake
|
|
|
|
cmake_minimum_required(VERSION 3.0)
|
|
project(example)
|
|
|
|
find_package(pybind11 REQUIRED) # or add_subdirectory(pybind11)
|
|
|
|
add_executable(example main.cpp)
|
|
target_link_libraries(example PRIVATE pybind11::embed)
|
|
|
|
|
|
Generating binding code automatically
|
|
=====================================
|
|
|
|
The ``Binder`` project is a tool for automatic generation of pybind11 binding
|
|
code by introspecting existing C++ codebases using LLVM/Clang. See the
|
|
[binder]_ documentation for details.
|
|
|
|
.. [binder] http://cppbinder.readthedocs.io/en/latest/about.html
|