tools/pybind11Tools.cmake

# tools/pybind11Tools.cmake -- Build system for the pybind11 modules
#
# Copyright (c) 2015 Wenzel Jakob <wenzel@inf.ethz.ch>
#
# All rights reserved. Use of this source code is governed by a
# BSD-style license that can be found in the LICENSE file.

cmake_minimum_required(VERSION 2.8.12)

# Add a CMake parameter for choosing a desired Python version
set(PYBIND11_PYTHON_VERSION "" CACHE STRING "Python version to use for compiling modules")

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)
    check_cxx_compiler_flag("-std=c++14" HAS_CPP14_FLAG)
    check_cxx_compiler_flag("-std=c++11" HAS_CPP11_FLAG)

    if (HAS_CPP14_FLAG)
      set(PYBIND11_CPP_STANDARD -std=c++14)
    elseif (HAS_CPP11_FLAG)
      set(PYBIND11_CPP_STANDARD -std=c++11)
    else()
      message(FATAL_ERROR "Unsupported compiler -- pybind11 requires C++11 support!")
    endif()

    set(PYBIND11_CPP_STANDARD ${PYBIND11_CPP_STANDARD} CACHE STRING
        "C++ standard flag, e.g. -std=c++11 or -std=c++14. Defaults to latest available." FORCE)
  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(<name> [MODULE | SHARED] [EXCLUDE_FROM_ALL]
#                     [NO_EXTRAS] [THIN_LTO] source1 [source2 ...])
#
function(pybind11_add_module target_name)
  set(options MODULE SHARED EXCLUDE_FROM_ALL NO_EXTRAS THIN_LTO)
  cmake_parse_arguments(ARG "${options}" "" "" ${ARGN})

  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()

  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
    PRIVATE ${pybind11_INCLUDE_DIR}  # from pybind11Config
    PRIVATE ${PYTHON_INCLUDE_DIRS})

  # The prefix and extension are provided by FindPythonLibsNew.cmake
  set_target_properties(${target_name} PROPERTIES PREFIX "${PYTHON_MODULE_PREFIX}")
  set_target_properties(${target_name} PROPERTIES SUFFIX "${PYTHON_MODULE_EXTENSION}")

  if(WIN32 OR CYGWIN)
    # Link against the Python shared library on Windows
    target_link_libraries(${target_name} PRIVATE ${PYTHON_LIBRARIES})
  elseif(APPLE)
    # It's quite common to have multiple copies of the same Python version
    # installed on one's system. E.g.: one copy from the OS and another copy
    # that's statically linked into an application like Blender or Maya.
    # If we link our plugin library against the OS Python here and import it
    # into Blender or Maya later on, this will cause segfaults when multiple
    # conflicting Python instances are active at the same time (even when they
    # are of the same version).

    # Windows is not affected by this issue since it handles DLL imports
    # differently. The solution for Linux and Mac OS is simple: we just don't
    # link against the Python library. The resulting shared library will have
    # missing symbols, but that's perfectly fine -- they will be resolved at
    # import time.

    target_link_libraries(${target_name} PRIVATE "-undefined dynamic_lookup")

    if(ARG_SHARED)
      # Suppress CMake >= 3.0 warning for shared libraries
      set_target_properties(${target_name} PROPERTIES MACOSX_RPATH ON)
    endif()
  endif()

  select_cxx_standard()
  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 ${U_CMAKE_BUILD_TYPE} MATCHES DEBUG)
      # Link Time Optimization
      if(NOT CYGWIN)
        _pybind11_find_lto_flag(lto_flag ARG_THIN_LTO)
        target_compile_options(${target_name} PRIVATE ${lto_flag})
      endif()

      # Default symbol visibility
      target_compile_options(${target_name} PRIVATE "-fvisibility=hidden")

      # Strip unnecessary sections of the binary on Linux/Mac OS
      if(CMAKE_STRIP)
        if(APPLE)
          add_custom_command(TARGET ${target_name} POST_BUILD
                             COMMAND ${CMAKE_STRIP} -x $<TARGET_FILE:${target_name}>)
        else()
          add_custom_command(TARGET ${target_name} POST_BUILD
                             COMMAND ${CMAKE_STRIP} $<TARGET_FILE:${target_name}>)
        endif()
      endif()
    endif()
  elseif(MSVC)
    # /MP enables multithreaded builds (relevant when there are many files), /bigobj is
    # needed for bigger binding projects due to the limit to 64k addressable sections
    target_compile_options(${target_name} PRIVATE /MP /bigobj)

    # Enforce link time code generation on MSVC, except in debug mode
    target_compile_options(${target_name} PRIVATE $<$<NOT:$<CONFIG:Debug>>:/GL>)

    # Fancy generator expressions don't work with linker flags, for reasons unknown
    set_property(TARGET ${target_name} APPEND_STRING PROPERTY LINK_FLAGS_RELEASE /LTCG)
    set_property(TARGET ${target_name} APPEND_STRING PROPERTY LINK_FLAGS_MINSIZEREL /LTCG)
    set_property(TARGET ${target_name} APPEND_STRING PROPERTY LINK_FLAGS_RELWITHDEBINFO /LTCG)
  endif()
endfunction()