From 0cbec5c96e92b26f2ed176c0ecaf8c40fa80f9b1 Mon Sep 17 00:00:00 2001 From: Dean Moldovan Date: Fri, 16 Dec 2016 22:58:37 +0100 Subject: [PATCH] Add new options and docs for pybind11_add_module See the documentation for a description of the options. --- docs/compiling.rst | 126 +++++++++++++----- .../installed_function/CMakeLists.txt | 2 +- .../subdirectory_function/CMakeLists.txt | 2 +- tools/pybind11Tools.cmake | 80 ++++++----- 4 files changed, 144 insertions(+), 66 deletions(-) diff --git a/docs/compiling.rst b/docs/compiling.rst index 35768fe45..ccb198b30 100644 --- a/docs/compiling.rst +++ b/docs/compiling.rst @@ -39,30 +39,88 @@ extension module can be created with just a few lines of code: 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 a function with the signature -``pybind11_add_module( source1 [source2 ...])``. It will take care of all -the details needed to build a Python extension module on any platform. - -The target Python version can be selected by setting the ``PYBIND11_PYTHON_VERSION`` -variable before adding the pybind11 subdirectory. Alternatively, an exact Python -installation can be specified by setting ``PYTHON_EXECUTABLE``. +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 -For CMake-based projects that don't include the pybind11 -repository internally, an external installation can be detected -through `find_package(pybind11 ... CONFIG ...)`. See the `Config file -`_ -docstring for details of relevant CMake variables. +pybind11_add_module +------------------- -Once detected, and after setting any variables to guide Python and -C++ standard detection, the aforementioned ``pybind11_add_module`` -wrapper to ``add_library`` can be employed as described above (after -``include(pybind11Tools)``). This procedure is available when using CMake ->= 2.8.12. A working example can be found at [test_installed_module]_ . +To ease the creation of Python extension modules, pybind11 provides a CMake +function with the following signature: + +.. code-block:: cmake + + pybind11_add_module( [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 ```` 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 +```` 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 ` +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 latest C++ standard +available on the target compiler. To override this, the standard flag can +be given explicitly in ``PYBIND11_CPP_STANDARD``: + +.. code-block:: cmake + + set(PYBIND11_CPP_STANDARD -std=c++11) + add_subdirectory(pybind11) # or find_package(pybind11) + +Note that this and all other configuration variables must be set **before** the +call to ``add_subdiretory`` or ``find_package``. The variables can also be set +when calling CMake from the command line using the ``-D=`` 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 @@ -72,27 +130,32 @@ wrapper to ``add_library`` can be employed as described above (after find_package(pybind11 REQUIRED) pybind11_add_module(example example.cpp) -.. [test_installed_module] https://github.com/pybind/pybind11/blob/master/tests/test_installed_module/CMakeLists.txt +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``. -When using a version of CMake greater than 3.0, pybind11 can -additionally be used as a special *interface library* following the -call to ``find_package``. CMake variables to guide Python and C++ -standard detection should be set *before* ``find_package``. When -``find_package`` returns, the target ``pybind11::pybind11`` 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. A working -example can be found at [test_installed_target]_ . +.. _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::pybind11`` +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) - add_library(example MODULE main.cpp) + find_package(pybind11 REQUIRED) # or add_subdirectory(pybind11) - find_package(pybind11 REQUIRED) + add_library(example MODULE main.cpp) target_link_libraries(example PRIVATE pybind11::pybind11) set_target_properties(example PROPERTIES PREFIX "${PYTHON_MODULE_PREFIX}" SUFFIX "${PYTHON_MODULE_EXTENSION}") @@ -111,6 +174,3 @@ example can be found at [test_installed_target]_ . (``-fvisibility=hidden``) and .OBJ files with many sections on Visual Studio (``/bigobj``). The :ref:`FAQ ` contains an explanation on why these are needed. - -.. [test_installed_target] https://github.com/pybind/pybind11/blob/master/tests/test_installed_target/CMakeLists.txt - diff --git a/tests/test_cmake_build/installed_function/CMakeLists.txt b/tests/test_cmake_build/installed_function/CMakeLists.txt index ff0b32e9c..e0c20a8a3 100644 --- a/tests/test_cmake_build/installed_function/CMakeLists.txt +++ b/tests/test_cmake_build/installed_function/CMakeLists.txt @@ -6,7 +6,7 @@ set(CMAKE_MODULE_PATH "") find_package(pybind11 CONFIG REQUIRED) message(STATUS "Found pybind11 v${pybind11_VERSION}: ${pybind11_INCLUDE_DIRS}") -pybind11_add_module(test_cmake_build SHARED ../main.cpp) +pybind11_add_module(test_cmake_build SHARED NO_EXTRAS ../main.cpp) add_custom_target(check ${CMAKE_COMMAND} -E env PYTHONPATH=$ ${PYTHON_EXECUTABLE} ${PROJECT_SOURCE_DIR}/../test.py ${PROJECT_NAME}) diff --git a/tests/test_cmake_build/subdirectory_function/CMakeLists.txt b/tests/test_cmake_build/subdirectory_function/CMakeLists.txt index 71b77359f..278007aeb 100644 --- a/tests/test_cmake_build/subdirectory_function/CMakeLists.txt +++ b/tests/test_cmake_build/subdirectory_function/CMakeLists.txt @@ -2,7 +2,7 @@ cmake_minimum_required(VERSION 2.8.12) project(test_subdirectory_module CXX) add_subdirectory(${PYBIND11_PROJECT_DIR} pybind11) -pybind11_add_module(test_cmake_build ../main.cpp) +pybind11_add_module(test_cmake_build THIN_LTO ../main.cpp) add_custom_target(check ${CMAKE_COMMAND} -E env PYTHONPATH=$ ${PYTHON_EXECUTABLE} ${PROJECT_SOURCE_DIR}/../test.py ${PROJECT_NAME}) diff --git a/tools/pybind11Tools.cmake b/tools/pybind11Tools.cmake index d629a6fba..fba76adee 100644 --- a/tools/pybind11Tools.cmake +++ b/tools/pybind11Tools.cmake @@ -14,6 +14,7 @@ set(Python_ADDITIONAL_VERSIONS 3.7 3.6 3.5 3.4) find_package(PythonLibsNew ${PYBIND11_PYTHON_VERSION} REQUIRED) include(CheckCXXCompilerFlag) +include(CMakeParseArguments) function(select_cxx_standard) if(NOT MSVC AND NOT PYBIND11_CPP_STANDARD) @@ -33,29 +34,48 @@ function(select_cxx_standard) endif() endfunction() +# Internal: find the appropriate LTO flag for this compiler +macro(_pybind11_find_lto_flag output_var prefer_thin_lto) + if(${prefer_thin_lto}) + # Check for ThinLTO support (Clang) + check_cxx_compiler_flag("-flto=thin" HAS_THIN_LTO_FLAG) + set(${output_var} $<${HAS_THIN_LTO_FLAG}:-flto=thin>) + endif() + + if(NOT ${prefer_thin_lto} OR NOT HAS_THIN_LTO_FLAG) + if(NOT CMAKE_CXX_COMPILER_ID MATCHES "Intel") + # Check for Link Time Optimization support (GCC/Clang) + check_cxx_compiler_flag("-flto" HAS_LTO_FLAG) + set(${output_var} $<${HAS_LTO_FLAG}:-flto>) + else() + # Intel equivalent to LTO is called IPO + check_cxx_compiler_flag("-ipo" HAS_IPO_FLAG) + set(${output_var} $<${HAS_IPO_FLAG}:-ipo>) + endif() + endif() +endmacro() + # Build a Python extension module: -# pybind11_add_module( [MODULE | SHARED] [EXCLUDE_FROM_ALL] source1 [source2 ...]) +# pybind11_add_module( [MODULE | SHARED] [EXCLUDE_FROM_ALL] +# [NO_EXTRAS] [THIN_LTO] source1 [source2 ...]) # function(pybind11_add_module target_name) - set(lib_type "MODULE") - set(do_lto True) - set(exclude_from_all "") - set(sources "") + set(options MODULE SHARED EXCLUDE_FROM_ALL NO_EXTRAS THIN_LTO) + cmake_parse_arguments(ARG "${options}" "" "" ${ARGN}) - set(_args_to_try "${ARGN}") - foreach(_ex_arg IN LISTS _args_to_try) - if(${_ex_arg} STREQUAL "MODULE") - set(lib_type "MODULE") - elseif(${_ex_arg} STREQUAL "SHARED") - set(lib_type "SHARED") - elseif(${_ex_arg} STREQUAL "EXCLUDE_FROM_ALL") - set(exclude_from_all "EXCLUDE_FROM_ALL") - else() - list(APPEND sources "${_ex_arg}") - endif() - endforeach() + if(ARG_MODULE AND ARG_SHARED) + message(FATAL_ERROR "Can't be both MODULE and SHARED") + elseif(ARG_SHARED) + set(lib_type SHARED) + else() + set(lib_type MODULE) + endif() - add_library(${target_name} ${lib_type} ${exclude_from_all} ${sources}) + if(ARG_EXCLUDE_FROM_ALL) + set(exclude_from_all EXCLUDE_FROM_ALL) + endif() + + add_library(${target_name} ${lib_type} ${exclude_from_all} ${ARG_UNPARSED_ARGUMENTS}) target_include_directories(${target_name} PRIVATE ${PYBIND11_INCLUDE_DIR} # from project CMakeLists.txt @@ -86,7 +106,7 @@ function(pybind11_add_module target_name) target_link_libraries(${target_name} PRIVATE "-undefined dynamic_lookup") - if(${lib_type} STREQUAL "SHARED") + if(ARG_SHARED) # Suppress CMake >= 3.0 warning for shared libraries set_target_properties(${target_name} PROPERTIES MACOSX_RPATH ON) endif() @@ -96,23 +116,21 @@ function(pybind11_add_module target_name) if(NOT MSVC) # Make sure C++11/14 are enabled target_compile_options(${target_name} PUBLIC ${PYBIND11_CPP_STANDARD}) + endif() + if(ARG_NO_EXTRAS) + return() + endif() + + if(NOT MSVC) # Enable link time optimization and set the default symbol # visibility to hidden (very important to obtain small binaries) string(TOUPPER "${CMAKE_BUILD_TYPE}" U_CMAKE_BUILD_TYPE) if (NOT ${U_CMAKE_BUILD_TYPE} MATCHES DEBUG) - # Check for Link Time Optimization support (GCC/Clang) - check_cxx_compiler_flag("-flto" HAS_LTO_FLAG) - if(HAS_LTO_FLAG AND NOT CYGWIN) - target_compile_options(${target_name} PRIVATE -flto) - endif() - - # Intel equivalent to LTO is called IPO - if(CMAKE_CXX_COMPILER_ID MATCHES "Intel") - check_cxx_compiler_flag("-ipo" HAS_IPO_FLAG) - if(HAS_IPO_FLAG) - target_compile_options(${target_name} PRIVATE -ipo) - endif() + # Link Time Optimization + if(NOT CYGWIN) + _pybind11_find_lto_flag(lto_flag ARG_THIN_LTO) + target_compile_options(${target_name} PRIVATE ${lto_flag}) endif() # Default symbol visibility