Replace boost::python with pybind11 (#1040)

* Replace boost::python with pybind11

* Replace add_python_module with pybind11_add_module

* Fix clang error on type-dependent expression

dlib/cmake_utils/add_python_module

-# This is a CMake file that sets up the add_python_module() macro.  This macro
-# lets you easily make python modules that use dlib.  
-#
-# The macro takes the module name as its first argument and then a list of
-# source files to compile into the module.  See ../tools/python/CMakeLists.txt
-# for an example.
-#
-# It also sets up a macro called install_${module_name}_to() where
-# ${module_name} is whatever you named your module.  This install_*_to() macro
-# takes a folder name and creates an install target that will copy the compiled
-# python module to that folder when you run "make install".  Note that the path
-# given to install_*_to() is relative to your CMakeLists.txt file.
-#
-
-
-option(PYTHON3 "Build a Python3 compatible library rather than Python2." OFF)
-
-# Avoid cmake warnings about changes in behavior of some Mac OS X path 
-# variable we don't care about.
-if (POLICY CMP0042)
-    cmake_policy(SET CMP0042 NEW)
-endif()
-
-
-# Sometimes a computer will have multiple python verions installed.  So in this
-# block of code we find the one in the user's path and add its home folder into
-# cmake's search path.  That way it will use that version of python first. 
-if (PYTHON3)
-    find_program(PYTHON_EXECUTABLE python3)
-endif()
-if (NOT PYTHON_EXECUTABLE)
-    find_program(PYTHON_EXECUTABLE python)
-endif()
-# Resolve symbolic links, hopefully this will give us a path in the proper
-# python home directory.
-get_filename_component(PYTHON_EXECUTABLE ${PYTHON_EXECUTABLE} REALPATH)
-# Pick out the parent directories
-get_filename_component(PYTHON_PATH ${PYTHON_EXECUTABLE} PATH)
-get_filename_component(PYTHON_PATH ${PYTHON_PATH} PATH)
-list(APPEND CMAKE_PREFIX_PATH "${PYTHON_PATH}")
-
-
-# To avoid dll hell, always link everything statically when compiling in
-# visual studio.  This way, the resulting library won't depend on a bunch
-# of other dll files and can be safely copied to someone elese's computer
-# and expected to run.
-if (MSVC)
-    include(${CMAKE_CURRENT_LIST_DIR}/tell_visual_studio_to_use_static_runtime.cmake)
-    add_definitions(-DBOOST_PYTHON_STATIC_LIB)
-    SET(Boost_USE_STATIC_LIBS ON)
-    SET(Boost_USE_MULTITHREADED ON)
-    SET(Boost_USE_STATIC_RUNTIME ON)
-endif()
-
-set(Boost_NO_BOOST_CMAKE ON)
-
-if (NOT WIN32)
-    set(BOOST_LIBRARYDIR ${BOOST_LIBRARYDIR} $ENV{BOOST_LIBRARYDIR}  
-            /usr/lib/x86_64-linux-gnu/)
-else()
-    link_directories($ENV{BOOST_LIBRARYDIR})
-endif()
-if (PYTHON3)
-    # On some systems the boost python3 module is called python-py34 so check
-    # for that one first.  
-    FIND_PACKAGE(Boost 1.41.0  COMPONENTS python-py34 )
-    if (NOT Boost_FOUND)
-        FIND_PACKAGE(Boost 1.41.0 COMPONENTS python-py35)
-    endif()
-    if (NOT Boost_FOUND)
-        FIND_PACKAGE(Boost 1.41.0 COMPONENTS python3)
-    endif()
-    if (NOT Boost_FOUND)
-        FIND_PACKAGE(Boost 1.41.0 COMPONENTS python)
-    endif()
-    set(Python_ADDITIONAL_VERSIONS 3.5 3.6)
-    FIND_PACKAGE(PythonLibs 3.4)
-else()
-    FIND_PACKAGE(Boost 1.41.0 COMPONENTS python)
-    FIND_PACKAGE(PythonLibs 2.6)
-endif()
-
-if (CMAKE_COMPILER_IS_GNUCXX)
-    # Just setting CMAKE_POSITION_INDEPENDENT_CODE should be enough to set
-    # -fPIC for GCC but sometimes it still doesn't get set, so make sure it
-    # does.
-    add_definitions("-fPIC")
-    set(CMAKE_POSITION_INDEPENDENT_CODE True)
-else()
-    set(CMAKE_POSITION_INDEPENDENT_CODE True)
-endif()
-
-# include dlib so we can link against it
-add_subdirectory(${CMAKE_CURRENT_LIST_DIR}/.. dlib_build)
-if (USING_OLD_VISUAL_STUDIO_COMPILER)
-   message(FATAL_ERROR "You have to use a version of Visual Studio that supports C++11.  As of December 2017, the only versions that have good enough C++11 support to compile the dlib Pyhton API is a fully updated Visual Studio 2015 or a fully updated Visual Studio 2017.  Older versions of either of these compilers have bad C++11 support and will fail to compile the Python extension. ***SO UPDATE YOUR VISUAL STUDIO TO MAKE THIS ERROR GO AWAY***")
-endif()
-
-
-if (NOT Boost_FOUND)
-    message(STATUS " *****************************************************************************************************")
-    if (WIN32)
-        if (NOT DEFINED ENV{BOOST_ROOT} OR NOT DEFINED ENV{BOOST_LIBRARYDIR})
-            message(STATUS "The BOOST_ROOT and/or BOOST_LIBRARYDIR environment variables are not set.  You need to set these ")
-            message(STATUS "variables so we know where boost is installed.  So set these variables to something like this:")
-            message(STATUS "    BOOST_ROOT=C:\\local\\boost_1_57_0 " )
-            message(STATUS "    BOOST_LIBRARYDIR=C:\\local\\boost_1_57_0\\stage\\lib")
-            message(STATUS "The best way to set enviornment variables in Windows is to go to the start menu's search box,")
-            message(STATUS "type environment, and open the Environment Variables dialog.  That lets you add more variables.")
-            message(STATUS "Add these variables to either user or system variables, it doesn't matter.")
-            message(STATUS "You might have to log out and log back in before the environment changes take effect.")
-        else()
-            message(STATUS "We couldn't find the right version of boost python.  If you installed boost and you are still "
-                    "getting this error then you might have installed a version of boost that was compiled with a different "
-                    "version of visual studio than the one you are using.  So you have to make sure that the version of "
-                    "visual studio is the same version that was used to compile the copy of boost you are using.")
-            message(STATUS "")
-            message(STATUS " You will likely need to compile boost yourself rather than using one of the precompiled ")
-            message(STATUS " windows binaries.  Do this by going to the folder tools\\build\\ within boost and running ")
-            message(STATUS " bootstrap.bat.  Then run the command: ")
-            message(STATUS "    b2 install")
-            message(STATUS " And then add the output bin folder to your PATH.  Usually this is the C:\\boost-build-engine\\bin")
-            message(STATUS " folder. Finally, go to the boost root and run a command like this:")
-            message(STATUS "    b2 -a --with-python address-model=64 toolset=msvc runtime-link=static")
-            message(STATUS " Note that you will need to set the address-model based on if you want a 32 or 64bit python library.")
-            message(STATUS " When it completes, set the BOOST_LIBRARYDIR environment variable equal to wherever b2 put the ")
-            message(STATUS " compiled libraries.  You will also need to set BOOST_ROOT to the root folder of the boost install.")
-            message(STATUS " E.g.  Something like this: ")
-            message(STATUS "    set BOOST_ROOT=C:\\local\\boost_1_57_0 " )
-            message(STATUS "    set BOOST_LIBRARYDIR=C:\\local\\boost_1_57_0\\stage\\lib")
-            message(STATUS "")
-            message(STATUS " Next, if you aren't using python setup.py then you will be invoking cmake to compile dlib.  ")
-            message(STATUS " In this case you may have to use cmake's -G option to set the 64 vs. 32bit mode of visual studio. ")
-            message(STATUS " Also, if you want a Python3 library you will need to add -DPYTHON3=1.  You do this with a statement like: ")
-            message(STATUS "    cmake -G \"Visual Studio 14 2015 Win64\" -DPYTHON3=1 ..\\..\\tools\\python")
-            message(STATUS " Rather than:")
-            message(STATUS "    cmake ..\\..\\tools\\python")
-            message(STATUS " Which will build a 32bit Python2 module by default on most systems.")
-            message(STATUS "")
-        endif()
-    else()
-        message(STATUS " To compile Boost.Python yourself download boost from boost.org and then go into the boost root folder")
-        message(STATUS " and run these commands: ")
-        message(STATUS "    ./bootstrap.sh --with-libraries=python") 
-        message(STATUS "    ./b2")
-        message(STATUS "    sudo ./b2 install")
-    endif()
-    message(STATUS " *****************************************************************************************************")
-    message(FATAL_ERROR " Boost python library not found. ")
-endif()
-
-
-
-
-message(STATUS "USING BOOST_LIBS: ${Boost_LIBRARIES}")
-if (WIN32)
-    message(STATUS "USING PYTHON_LIBS: ${PYTHON_LIBRARIES}")
-endif()
-
-# We put the extra _ on the end of the name just so it's possible to
-# have a module name of dlib and not get a conflict with the target named
-# dlib in ../dlib/cmake.  We use the target OUPUT_NAME property to ensure the
-# output name is set to what the user asked for (i.e. no _).
-macro(add_python_module module_name module_sources )
-   ADD_LIBRARY(${module_name}_ SHARED ${module_sources} ${ARGN} )
-   TARGET_LINK_LIBRARIES(${module_name}_ ${Boost_LIBRARIES} dlib::dlib)
-
-    target_include_directories(${module_name}_ SYSTEM PUBLIC "${Boost_INCLUDE_DIRS}")
-    if (PYTHON_INCLUDE_PATH)
-        target_include_directories(${module_name}_ SYSTEM PUBLIC "${PYTHON_INCLUDE_PATH}" )
-    else()
-        target_include_directories(${module_name}_ SYSTEM PUBLIC "${PYTHON_INCLUDE_DIRS}" )
-    endif()
-
-
-   if(WIN32 AND NOT CYGWIN)
-      TARGET_LINK_LIBRARIES(${module_name}_ ${PYTHON_LIBRARIES})
-      SET_TARGET_PROPERTIES( ${module_name}_
-         PROPERTIES
-         PREFIX ""
-         SUFFIX ".pyd"
-         OUTPUT_NAME ${module_name}
-         )
-   elseif(CYGWIN)
-      SET_TARGET_PROPERTIES( ${module_name}_
-         PROPERTIES
-         PREFIX ""
-         SUFFIX ".dll"
-         OUTPUT_NAME ${module_name}
-         )
-    elseif(APPLE)
-      SET_TARGET_PROPERTIES( ${module_name}_
-         PROPERTIES
-         LINK_FLAGS "-undefined dynamic_lookup"
-         PREFIX ""
-         SUFFIX ".so"
-         OUTPUT_NAME ${module_name}
-         )
-   else()
-      SET_TARGET_PROPERTIES( ${module_name}_
-         PROPERTIES
-         LINK_FLAGS "-shared"
-         PREFIX ""
-         SUFFIX ".so"
-         OUTPUT_NAME ${module_name}
-         )
-   endif()
-
-   macro(install_${module_name}_to path)
-       # Determine the path to our CMakeLists.txt file.
-       string(REGEX REPLACE "CMakeLists.txt$" "" base_path ${CMAKE_CURRENT_LIST_FILE})
-       INSTALL(TARGETS ${module_name}_ 
-            RUNTIME DESTINATION  "${base_path}/${path}"
-            LIBRARY DESTINATION  "${base_path}/${path}"
-           )
-   endmacro()
-
-endmacro()
-
-
-

dlib/external/pybind11/CMakeLists.txt

+# CMakeLists.txt -- 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)
+
+if (POLICY CMP0048)
+  # cmake warns if loaded from a min-3.0-required parent dir, so silence the warning:
+  cmake_policy(SET CMP0048 NEW)
+endif()
+
+# CMake versions < 3.4.0 do not support try_compile/pthread checks without C as active language.
+if(CMAKE_VERSION VERSION_LESS 3.4.0)
+  project(pybind11)
+else()
+  project(pybind11 CXX)
+endif()
+
+# Check if pybind11 is being used directly or via add_subdirectory
+set(PYBIND11_MASTER_PROJECT OFF)
+if (CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
+  set(PYBIND11_MASTER_PROJECT ON)
+endif()
+
+option(PYBIND11_INSTALL "Install pybind11 header files?" ${PYBIND11_MASTER_PROJECT})
+option(PYBIND11_TEST    "Build pybind11 test suite?"     ${PYBIND11_MASTER_PROJECT})
+
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/tools")
+
+include(pybind11Tools)
+
+# Cache variables so pybind11_add_module can be used in parent projects
+set(PYBIND11_INCLUDE_DIR "${CMAKE_CURRENT_LIST_DIR}/include" CACHE INTERNAL "")
+set(PYTHON_INCLUDE_DIRS ${PYTHON_INCLUDE_DIRS} CACHE INTERNAL "")
+set(PYTHON_LIBRARIES ${PYTHON_LIBRARIES} CACHE INTERNAL "")
+set(PYTHON_MODULE_PREFIX ${PYTHON_MODULE_PREFIX} CACHE INTERNAL "")
+set(PYTHON_MODULE_EXTENSION ${PYTHON_MODULE_EXTENSION} CACHE INTERNAL "")
+
+# NB: when adding a header don't forget to also add it to setup.py
+set(PYBIND11_HEADERS
+  include/pybind11/detail/class.h
+  include/pybind11/detail/common.h
+  include/pybind11/detail/descr.h
+  include/pybind11/detail/init.h
+  include/pybind11/detail/internals.h
+  include/pybind11/detail/typeid.h
+  include/pybind11/attr.h
+  include/pybind11/buffer_info.h
+  include/pybind11/cast.h
+  include/pybind11/chrono.h
+  include/pybind11/common.h
+  include/pybind11/complex.h
+  include/pybind11/options.h
+  include/pybind11/eigen.h
+  include/pybind11/embed.h
+  include/pybind11/eval.h
+  include/pybind11/functional.h
+  include/pybind11/numpy.h
+  include/pybind11/operators.h
+  include/pybind11/pybind11.h
+  include/pybind11/pytypes.h
+  include/pybind11/stl.h
+  include/pybind11/stl_bind.h
+)
+string(REPLACE "include/" "${CMAKE_CURRENT_SOURCE_DIR}/include/"
+       PYBIND11_HEADERS "${PYBIND11_HEADERS}")
+
+if (PYBIND11_TEST)
+  add_subdirectory(tests)
+endif()
+
+include(GNUInstallDirs)
+include(CMakePackageConfigHelpers)
+
+# extract project version from source
+file(STRINGS "${PYBIND11_INCLUDE_DIR}/pybind11/detail/common.h" pybind11_version_defines
+     REGEX "#define PYBIND11_VERSION_(MAJOR|MINOR|PATCH) ")
+foreach(ver ${pybind11_version_defines})
+  if (ver MATCHES "#define PYBIND11_VERSION_(MAJOR|MINOR|PATCH) +([^ ]+)$")
+    set(PYBIND11_VERSION_${CMAKE_MATCH_1} "${CMAKE_MATCH_2}" CACHE INTERNAL "")
+  endif()
+endforeach()
+set(${PROJECT_NAME}_VERSION ${PYBIND11_VERSION_MAJOR}.${PYBIND11_VERSION_MINOR}.${PYBIND11_VERSION_PATCH})
+message(STATUS "pybind11 v${${PROJECT_NAME}_VERSION}")
+
+option (USE_PYTHON_INCLUDE_DIR "Install pybind11 headers in Python include directory instead of default installation prefix" OFF)
+if (USE_PYTHON_INCLUDE_DIR)
+    file(RELATIVE_PATH CMAKE_INSTALL_INCLUDEDIR ${CMAKE_INSTALL_PREFIX} ${PYTHON_INCLUDE_DIRS})
+endif()
+
+if(NOT (CMAKE_VERSION VERSION_LESS 3.0))  # CMake >= 3.0
+  # Build an interface library target:
+  add_library(pybind11 INTERFACE)
+  add_library(pybind11::pybind11 ALIAS pybind11)  # to match exported target
+  target_include_directories(pybind11 INTERFACE $<BUILD_INTERFACE:${PYBIND11_INCLUDE_DIR}>
+                                                $<BUILD_INTERFACE:${PYTHON_INCLUDE_DIRS}>
+                                                $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
+  target_compile_options(pybind11 INTERFACE $<BUILD_INTERFACE:${PYBIND11_CPP_STANDARD}>)
+
+  add_library(module INTERFACE)
+  add_library(pybind11::module ALIAS module)
+  if(NOT MSVC)
+    target_compile_options(module INTERFACE -fvisibility=hidden)
+  endif()
+  target_link_libraries(module INTERFACE pybind11::pybind11)
+  if(WIN32 OR CYGWIN)
+    target_link_libraries(module INTERFACE $<BUILD_INTERFACE:${PYTHON_LIBRARIES}>)
+  elseif(APPLE)
+    target_link_libraries(module INTERFACE "-undefined dynamic_lookup")
+  endif()
+
+  add_library(embed INTERFACE)
+  add_library(pybind11::embed ALIAS embed)
+  target_link_libraries(embed INTERFACE pybind11::pybind11 $<BUILD_INTERFACE:${PYTHON_LIBRARIES}>)
+endif()
+
+if (PYBIND11_INSTALL)
+  install(DIRECTORY ${PYBIND11_INCLUDE_DIR}/pybind11 DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+  # GNUInstallDirs "DATADIR" wrong here; CMake search path wants "share".
+  set(PYBIND11_CMAKECONFIG_INSTALL_DIR "share/cmake/${PROJECT_NAME}" CACHE STRING "install path for pybind11Config.cmake")
+
+  configure_package_config_file(tools/${PROJECT_NAME}Config.cmake.in
+                                "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
+                                INSTALL_DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
+  # Remove CMAKE_SIZEOF_VOID_P from ConfigVersion.cmake since the library does
+  # not depend on architecture specific settings or libraries.
+  set(_PYBIND11_CMAKE_SIZEOF_VOID_P ${CMAKE_SIZEOF_VOID_P})
+  unset(CMAKE_SIZEOF_VOID_P)
+  write_basic_package_version_file(${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
+                                   VERSION ${${PROJECT_NAME}_VERSION}
+                                   COMPATIBILITY AnyNewerVersion)
+  set(CMAKE_SIZEOF_VOID_P ${_PYBIND11_CMAKE_SIZEOF_VOID_P})
+  install(FILES ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake
+                ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
+                tools/FindPythonLibsNew.cmake
+                tools/pybind11Tools.cmake
+          DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
+
+  if(NOT (CMAKE_VERSION VERSION_LESS 3.0))
+    if(NOT PYBIND11_EXPORT_NAME)
+      set(PYBIND11_EXPORT_NAME "${PROJECT_NAME}Targets")
+    endif()
+
+    install(TARGETS pybind11 module embed
+            EXPORT "${PYBIND11_EXPORT_NAME}")
+    if(PYBIND11_MASTER_PROJECT)
+      install(EXPORT "${PYBIND11_EXPORT_NAME}"
+              NAMESPACE "${PROJECT_NAME}::"
+              DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
+    endif()
+  endif()
+endif()

dlib/external/pybind11/CONTRIBUTING.md

+Thank you for your interest in this project! Please refer to the following
+sections on how to contribute code and bug reports.
+
+### Reporting bugs
+
+At the moment, this project is run in the spare time of a single person
+([Wenzel Jakob](http://rgl.epfl.ch/people/wjakob)) with very limited resources
+for issue tracker tickets. Thus, before submitting a question or bug report,
+please take a moment of your time and ensure that your issue isn't already
+discussed in the project documentation provided at
+[http://pybind11.readthedocs.org/en/latest](http://pybind11.readthedocs.org/en/latest).
+
+Assuming that you have identified a previously unknown problem or an important
+question, it's essential that you submit a self-contained and minimal piece of
+code that reproduces the problem. In other words: no external dependencies,
+isolate the function(s) that cause breakage, submit matched and complete C++
+and Python snippets that can be easily compiled and run on my end.
+
+## Pull requests
+Contributions are submitted, reviewed, and accepted using Github pull requests.
+Please refer to [this
+article](https://help.github.com/articles/using-pull-requests) for details and
+adhere to the following rules to make the process as smooth as possible:
+
+* Make a new branch for every feature you're working on.
+* Make small and clean pull requests that are easy to review but make sure they
+  do add value by themselves.
+* Add tests for any new functionality and run the test suite (``make pytest``)
+  to ensure that no existing features break.
+* This project has a strong focus on providing general solutions using a
+  minimal amount of code, thus small pull requests are greatly preferred.
+
+### Licensing of contributions
+
+pybind11 is provided under a BSD-style license that can be found in the
+``LICENSE`` file. By using, distributing, or contributing to this project, you
+agree to the terms and conditions of this license.
+
+You are under no obligation whatsoever to provide any bug fixes, patches, or
+upgrades to the features, functionality or performance of the source code
+("Enhancements") to anyone; however, if you choose to make your Enhancements
+available either publicly, or directly to the author of this software, without
+imposing a separate written license agreement for such Enhancements, then you
+hereby grant the following license: a non-exclusive, royalty-free perpetual
+license to install, use, modify, prepare derivative works, incorporate into
+other computer software, distribute, and sublicense such enhancements or
+derivative works thereof, in binary and source code form.

dlib/external/pybind11/LICENSE

+Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>, All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+3. Neither the name of the copyright holder nor the names of its contributors
+   may be used to endorse or promote products derived from this software
+   without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+Please also refer to the file CONTRIBUTING.md, which clarifies licensing of
+external contributions to this project including patches, pull requests, etc.

dlib/external/pybind11/README.md

+![pybind11 logo](https://github.com/pybind/pybind11/raw/master/docs/pybind11-logo.png)
+
+# pybind11 — Seamless operability between C++11 and Python
+
+[![Documentation Status](https://readthedocs.org/projects/pybind11/badge/?version=master)](http://pybind11.readthedocs.org/en/master/?badge=master)
+[![Documentation Status](https://readthedocs.org/projects/pybind11/badge/?version=stable)](http://pybind11.readthedocs.org/en/stable/?badge=stable)
+[![Gitter chat](https://img.shields.io/gitter/room/gitterHQ/gitter.svg)](https://gitter.im/pybind/Lobby)
+[![Build Status](https://travis-ci.org/pybind/pybind11.svg?branch=master)](https://travis-ci.org/pybind/pybind11)
+[![Build status](https://ci.appveyor.com/api/projects/status/riaj54pn4h08xy40?svg=true)](https://ci.appveyor.com/project/wjakob/pybind11)
+
+**pybind11** is a lightweight header-only library that exposes C++ types in Python
+and vice versa, mainly to create Python bindings of existing C++ code. Its
+goals and syntax are similar to the excellent
+[Boost.Python](http://www.boost.org/doc/libs/1_58_0/libs/python/doc/) library
+by David Abrahams: to minimize boilerplate code in traditional extension
+modules by inferring type information using compile-time introspection.
+
+The main issue with Boost.Python—and the reason for creating such a similar
+project—is Boost. Boost is an enormously large and complex suite of utility
+libraries that works with almost every C++ compiler in existence. This
+compatibility has its cost: arcane template tricks and workarounds are
+necessary to support the oldest and buggiest of compiler specimens. Now that
+C++11-compatible compilers are widely available, this heavy machinery has
+become an excessively large and unnecessary dependency.
+
+Think of this library as a tiny self-contained version of Boost.Python with
+everything stripped away that isn't relevant for binding generation. Without
+comments, the core header files only require ~4K lines of code and depend on
+Python (2.7 or 3.x, or PyPy2.7 >= 5.7) and the C++ standard library. This
+compact implementation was possible thanks to some of the new C++11 language
+features (specifically: tuples, lambda functions and variadic templates). Since
+its creation, this library has grown beyond Boost.Python in many ways, leading
+to dramatically simpler binding code in many common situations.
+
+Tutorial and reference documentation is provided at
+[http://pybind11.readthedocs.org/en/master](http://pybind11.readthedocs.org/en/master).
+A PDF version of the manual is available
+[here](https://media.readthedocs.org/pdf/pybind11/master/pybind11.pdf).
+
+## Core features
+pybind11 can map the following core C++ features to Python
+
+- Functions accepting and returning custom data structures per value, reference, or pointer
+- Instance methods and static methods
+- Overloaded functions
+- Instance attributes and static attributes
+- Arbitrary exception types
+- Enumerations
+- Callbacks
+- Iterators and ranges
+- Custom operators
+- Single and multiple inheritance
+- STL data structures
+- Iterators and ranges
+- Smart pointers with reference counting like ``std::shared_ptr``
+- Internal references with correct reference counting
+- C++ classes with virtual (and pure virtual) methods can be extended in Python
+
+## Goodies
+In addition to the core functionality, pybind11 provides some extra goodies:
+
+- Python 2.7, 3.x, and PyPy (PyPy2.7 >= 5.7) are supported with an
+  implementation-agnostic interface.
+
+- It is possible to bind C++11 lambda functions with captured variables. The
+  lambda capture data is stored inside the resulting Python function object.
+
+- pybind11 uses C++11 move constructors and move assignment operators whenever
+  possible to efficiently transfer custom data types.
+
+- It's easy to expose the internal storage of custom data types through
+  Pythons' buffer protocols. This is handy e.g. for fast conversion between
+  C++ matrix classes like Eigen and NumPy without expensive copy operations.
+
+- pybind11 can automatically vectorize functions so that they are transparently
+  applied to all entries of one or more NumPy array arguments.
+
+- Python's slice-based access and assignment operations can be supported with
+  just a few lines of code.
+
+- Everything is contained in just a few header files; there is no need to link
+  against any additional libraries.
+
+- Binaries are generally smaller by a factor of at least 2 compared to
+  equivalent bindings generated by Boost.Python. A recent pybind11 conversion
+  of PyRosetta, an enormous Boost.Python binding project,
+  [reported](http://graylab.jhu.edu/RosettaCon2016/PyRosetta-4.pdf) a binary
+  size reduction of **5.4x** and compile time reduction by **5.8x**.
+
+- Function signatures are precomputed at compile time (using ``constexpr``),
+  leading to smaller binaries.
+
+- With little extra effort, C++ types can be pickled and unpickled similar to
+  regular Python objects.
+
+## Supported compilers
+
+1. Clang/LLVM 3.3 or newer (for Apple Xcode's clang, this is 5.0.0 or newer)
+2. GCC 4.8 or newer
+3. Microsoft Visual Studio 2015 Update 3 or newer
+4. Intel C++ compiler 16 or newer (15 with a [workaround](https://github.com/pybind/pybind11/issues/276))
+5. Cygwin/GCC (tested on 2.5.1)
+
+## About
+
+This project was created by [Wenzel Jakob](http://rgl.epfl.ch/people/wjakob).
+Significant features and/or improvements to the code were contributed by
+Jonas Adler,
+Sylvain Corlay,
+Trent Houliston,
+Axel Huebl,
+@hulucc,
+Sergey Lyskov
+Johan Mabille,
+Tomasz Miąsko,
+Dean Moldovan,
+Ben Pritchard,
+Jason Rhinelander,
+Boris Schäling,
+Pim Schellart,
+Ivan Smirnov, and
+Patrick Stewart.
+
+### License
+
+pybind11 is provided under a BSD-style license that can be found in the
+``LICENSE`` file. By using, distributing, or contributing to this project,
+you agree to the terms and conditions of this license.

dlib/external/pybind11/include/pybind11/attr.h

+/*
+    pybind11/attr.h: Infrastructure for processing custom
+    type and function attributes
+
+    Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "cast.h"
+
+NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+
+/// \addtogroup annotations
+/// @{
+
+/// Annotation for methods
+struct is_method { handle class_; is_method(const handle &c) : class_(c) { } };
+
+/// Annotation for operators
+struct is_operator { };
+
+/// Annotation for parent scope
+struct scope { handle value; scope(const handle &s) : value(s) { } };
+
+/// Annotation for documentation
+struct doc { const char *value; doc(const char *value) : value(value) { } };
+
+/// Annotation for function names
+struct name { const char *value; name(const char *value) : value(value) { } };
+
+/// Annotation indicating that a function is an overload associated with a given "sibling"
+struct sibling { handle value; sibling(const handle &value) : value(value.ptr()) { } };
+
+/// Annotation indicating that a class derives from another given type
+template <typename T> struct base {
+    PYBIND11_DEPRECATED("base<T>() was deprecated in favor of specifying 'T' as a template argument to class_")
+    base() { }
+};
+
+/// Keep patient alive while nurse lives
+template <size_t Nurse, size_t Patient> struct keep_alive { };
+
+/// Annotation indicating that a class is involved in a multiple inheritance relationship
+struct multiple_inheritance { };
+
+/// Annotation which enables dynamic attributes, i.e. adds `__dict__` to a class
+struct dynamic_attr { };
+
+/// Annotation which enables the buffer protocol for a type
+struct buffer_protocol { };
+
+/// Annotation which requests that a special metaclass is created for a type
+struct metaclass {
+    handle value;
+
+    PYBIND11_DEPRECATED("py::metaclass() is no longer required. It's turned on by default now.")
+    metaclass() {}
+
+    /// Override pybind11's default metaclass
+    explicit metaclass(handle value) : value(value) { }
+};
+
+/// Annotation that marks a class as local to the module:
+struct module_local { const bool value; constexpr module_local(bool v = true) : value(v) { } };
+
+/// Annotation to mark enums as an arithmetic type
+struct arithmetic { };
+
+/** \rst
+    A call policy which places one or more guard variables (``Ts...``) around the function call.
+
+    For example, this definition:
+
+    .. code-block:: cpp
+
+        m.def("foo", foo, py::call_guard<T>());
+
+    is equivalent to the following pseudocode:
+
+    .. code-block:: cpp
+
+        m.def("foo", [](args...) {
+            T scope_guard;
+            return foo(args...); // forwarded arguments
+        });
+ \endrst */
+template <typename... Ts> struct call_guard;
+
+template <> struct call_guard<> { using type = detail::void_type; };
+
+template <typename T>
+struct call_guard<T> {
+    static_assert(std::is_default_constructible<T>::value,
+                  "The guard type must be default constructible");
+
+    using type = T;
+};
+
+template <typename T, typename... Ts>
+struct call_guard<T, Ts...> {
+    struct type {
+        T guard{}; // Compose multiple guard types with left-to-right default-constructor order
+        typename call_guard<Ts...>::type next{};
+    };
+};
+
+/// @} annotations
+
+NAMESPACE_BEGIN(detail)
+/* Forward declarations */
+enum op_id : int;
+enum op_type : int;
+struct undefined_t;
+template <op_id id, op_type ot, typename L = undefined_t, typename R = undefined_t> struct op_;
+inline void keep_alive_impl(size_t Nurse, size_t Patient, function_call &call, handle ret);
+
+/// Internal data structure which holds metadata about a keyword argument
+struct argument_record {
+    const char *name;  ///< Argument name
+    const char *descr; ///< Human-readable version of the argument value
+    handle value;      ///< Associated Python object
+    bool convert : 1;  ///< True if the argument is allowed to convert when loading
+    bool none : 1;     ///< True if None is allowed when loading
+
+    argument_record(const char *name, const char *descr, handle value, bool convert, bool none)
+        : name(name), descr(descr), value(value), convert(convert), none(none) { }
+};
+
+/// Internal data structure which holds metadata about a bound function (signature, overloads, etc.)
+struct function_record {
+    function_record()
+        : is_constructor(false), is_new_style_constructor(false), is_stateless(false),
+          is_operator(false), has_args(false), has_kwargs(false), is_method(false) { }
+
+    /// Function name
+    char *name = nullptr; /* why no C++ strings? They generate heavier code.. */
+
+    // User-specified documentation string
+    char *doc = nullptr;
+
+    /// Human-readable version of the function signature
+    char *signature = nullptr;
+
+    /// List of registered keyword arguments
+    std::vector<argument_record> args;
+
+    /// Pointer to lambda function which converts arguments and performs the actual call
+    handle (*impl) (function_call &) = nullptr;
+
+    /// Storage for the wrapped function pointer and captured data, if any
+    void *data[3] = { };
+
+    /// Pointer to custom destructor for 'data' (if needed)
+    void (*free_data) (function_record *ptr) = nullptr;
+
+    /// Return value policy associated with this function
+    return_value_policy policy = return_value_policy::automatic;
+
+    /// True if name == '__init__'
+    bool is_constructor : 1;
+
+    /// True if this is a new-style `__init__` defined in `detail/init.h`
+    bool is_new_style_constructor : 1;
+
+    /// True if this is a stateless function pointer
+    bool is_stateless : 1;
+
+    /// True if this is an operator (__add__), etc.
+    bool is_operator : 1;
+
+    /// True if the function has a '*args' argument
+    bool has_args : 1;
+
+    /// True if the function has a '**kwargs' argument
+    bool has_kwargs : 1;
+
+    /// True if this is a method
+    bool is_method : 1;
+
+    /// Number of arguments (including py::args and/or py::kwargs, if present)
+    std::uint16_t nargs;
+
+    /// Python method object
+    PyMethodDef *def = nullptr;
+
+    /// Python handle to the parent scope (a class or a module)
+    handle scope;
+
+    /// Python handle to the sibling function representing an overload chain
+    handle sibling;
+
+    /// Pointer to next overload
+    function_record *next = nullptr;
+};
+
+/// Special data structure which (temporarily) holds metadata about a bound class
+struct type_record {
+    PYBIND11_NOINLINE type_record()
+        : multiple_inheritance(false), dynamic_attr(false), buffer_protocol(false), module_local(false) { }
+
+    /// Handle to the parent scope
+    handle scope;
+
+    /// Name of the class
+    const char *name = nullptr;
+
+    // Pointer to RTTI type_info data structure
+    const std::type_info *type = nullptr;
+
+    /// How large is the underlying C++ type?
+    size_t type_size = 0;
+
+    /// How large is the type's holder?
+    size_t holder_size = 0;
+
+    /// The global operator new can be overridden with a class-specific variant
+    void *(*operator_new)(size_t) = ::operator new;
+
+    /// Function pointer to class_<..>::init_instance
+    void (*init_instance)(instance *, const void *) = nullptr;
+
+    /// Function pointer to class_<..>::dealloc
+    void (*dealloc)(detail::value_and_holder &) = nullptr;
+
+    /// List of base classes of the newly created type
+    list bases;
+
+    /// Optional docstring
+    const char *doc = nullptr;
+
+    /// Custom metaclass (optional)
+    handle metaclass;
+
+    /// Multiple inheritance marker
+    bool multiple_inheritance : 1;
+
+    /// Does the class manage a __dict__?
+    bool dynamic_attr : 1;
+
+    /// Does the class implement the buffer protocol?
+    bool buffer_protocol : 1;
+
+    /// Is the default (unique_ptr) holder type used?
+    bool default_holder : 1;
+
+    /// Is the class definition local to the module shared object?
+    bool module_local : 1;
+
+    PYBIND11_NOINLINE void add_base(const std::type_info &base, void *(*caster)(void *)) {
+        auto base_info = detail::get_type_info(base, false);
+        if (!base_info) {
+            std::string tname(base.name());
+            detail::clean_type_id(tname);
+            pybind11_fail("generic_type: type \"" + std::string(name) +
+                          "\" referenced unknown base type \"" + tname + "\"");
+        }
+
+        if (default_holder != base_info->default_holder) {
+            std::string tname(base.name());
+            detail::clean_type_id(tname);
+            pybind11_fail("generic_type: type \"" + std::string(name) + "\" " +
+                    (default_holder ? "does not have" : "has") +
+                    " a non-default holder type while its base \"" + tname + "\" " +
+                    (base_info->default_holder ? "does not" : "does"));
+        }
+
+        bases.append((PyObject *) base_info->type);
+
+        if (base_info->type->tp_dictoffset != 0)
+            dynamic_attr = true;
+
+        if (caster)
+            base_info->implicit_casts.emplace_back(type, caster);
+    }
+};
+
+inline function_call::function_call(function_record &f, handle p) :
+        func(f), parent(p) {
+    args.reserve(f.nargs);
+    args_convert.reserve(f.nargs);
+}
+
+/// Tag for a new-style `__init__` defined in `detail/init.h`
+struct is_new_style_constructor { };
+
+/**
+ * Partial template specializations to process custom attributes provided to
+ * cpp_function_ and class_. These are either used to initialize the respective
+ * fields in the type_record and function_record data structures or executed at
+ * runtime to deal with custom call policies (e.g. keep_alive).
+ */
+template <typename T, typename SFINAE = void> struct process_attribute;
+
+template <typename T> struct process_attribute_default {
+    /// Default implementation: do nothing
+    static void init(const T &, function_record *) { }
+    static void init(const T &, type_record *) { }
+    static void precall(function_call &) { }
+    static void postcall(function_call &, handle) { }
+};
+
+/// Process an attribute specifying the function's name
+template <> struct process_attribute<name> : process_attribute_default<name> {
+    static void init(const name &n, function_record *r) { r->name = const_cast<char *>(n.value); }
+};
+
+/// Process an attribute specifying the function's docstring
+template <> struct process_attribute<doc> : process_attribute_default<doc> {
+    static void init(const doc &n, function_record *r) { r->doc = const_cast<char *>(n.value); }
+};
+
+/// Process an attribute specifying the function's docstring (provided as a C-style string)
+template <> struct process_attribute<const char *> : process_attribute_default<const char *> {
+    static void init(const char *d, function_record *r) { r->doc = const_cast<char *>(d); }
+    static void init(const char *d, type_record *r) { r->doc = const_cast<char *>(d); }
+};
+template <> struct process_attribute<char *> : process_attribute<const char *> { };
+
+/// Process an attribute indicating the function's return value policy
+template <> struct process_attribute<return_value_policy> : process_attribute_default<return_value_policy> {
+    static void init(const return_value_policy &p, function_record *r) { r->policy = p; }
+};
+
+/// Process an attribute which indicates that this is an overloaded function associated with a given sibling
+template <> struct process_attribute<sibling> : process_attribute_default<sibling> {
+    static void init(const sibling &s, function_record *r) { r->sibling = s.value; }
+};
+
+/// Process an attribute which indicates that this function is a method
+template <> struct process_attribute<is_method> : process_attribute_default<is_method> {
+    static void init(const is_method &s, function_record *r) { r->is_method = true; r->scope = s.class_; }
+};
+
+/// Process an attribute which indicates the parent scope of a method
+template <> struct process_attribute<scope> : process_attribute_default<scope> {
+    static void init(const scope &s, function_record *r) { r->scope = s.value; }
+};
+
+/// Process an attribute which indicates that this function is an operator
+template <> struct process_attribute<is_operator> : process_attribute_default<is_operator> {
+    static void init(const is_operator &, function_record *r) { r->is_operator = true; }
+};
+
+template <> struct process_attribute<is_new_style_constructor> : process_attribute_default<is_new_style_constructor> {
+    static void init(const is_new_style_constructor &, function_record *r) { r->is_new_style_constructor = true; }
+};
+
+/// Process a keyword argument attribute (*without* a default value)
+template <> struct process_attribute<arg> : process_attribute_default<arg> {
+    static void init(const arg &a, function_record *r) {
+        if (r->is_method && r->args.empty())
+            r->args.emplace_back("self", nullptr, handle(), true /*convert*/, false /*none not allowed*/);
+        r->args.emplace_back(a.name, nullptr, handle(), !a.flag_noconvert, a.flag_none);
+    }
+};
+
+/// Process a keyword argument attribute (*with* a default value)
+template <> struct process_attribute<arg_v> : process_attribute_default<arg_v> {
+    static void init(const arg_v &a, function_record *r) {
+        if (r->is_method && r->args.empty())
+            r->args.emplace_back("self", nullptr /*descr*/, handle() /*parent*/, true /*convert*/, false /*none not allowed*/);
+
+        if (!a.value) {
+#if !defined(NDEBUG)
+            std::string descr("'");
+            if (a.name) descr += std::string(a.name) + ": ";
+            descr += a.type + "'";
+            if (r->is_method) {
+                if (r->name)
+                    descr += " in method '" + (std::string) str(r->scope) + "." + (std::string) r->name + "'";
+                else
+                    descr += " in method of '" + (std::string) str(r->scope) + "'";
+            } else if (r->name) {
+                descr += " in function '" + (std::string) r->name + "'";
+            }
+            pybind11_fail("arg(): could not convert default argument "
+                          + descr + " into a Python object (type not registered yet?)");
+#else
+            pybind11_fail("arg(): could not convert default argument "
+                          "into a Python object (type not registered yet?). "
+                          "Compile in debug mode for more information.");
+#endif
+        }
+        r->args.emplace_back(a.name, a.descr, a.value.inc_ref(), !a.flag_noconvert, a.flag_none);
+    }
+};
+
+/// Process a parent class attribute.  Single inheritance only (class_ itself already guarantees that)
+template <typename T>
+struct process_attribute<T, enable_if_t<is_pyobject<T>::value>> : process_attribute_default<handle> {
+    static void init(const handle &h, type_record *r) { r->bases.append(h); }
+};
+
+/// Process a parent class attribute (deprecated, does not support multiple inheritance)
+template <typename T>
+struct process_attribute<base<T>> : process_attribute_default<base<T>> {
+    static void init(const base<T> &, type_record *r) { r->add_base(typeid(T), nullptr); }
+};
+
+/// Process a multiple inheritance attribute
+template <>
+struct process_attribute<multiple_inheritance> : process_attribute_default<multiple_inheritance> {
+    static void init(const multiple_inheritance &, type_record *r) { r->multiple_inheritance = true; }
+};
+
+template <>
+struct process_attribute<dynamic_attr> : process_attribute_default<dynamic_attr> {
+    static void init(const dynamic_attr &, type_record *r) { r->dynamic_attr = true; }
+};
+
+template <>
+struct process_attribute<buffer_protocol> : process_attribute_default<buffer_protocol> {
+    static void init(const buffer_protocol &, type_record *r) { r->buffer_protocol = true; }
+};
+
+template <>
+struct process_attribute<metaclass> : process_attribute_default<metaclass> {
+    static void init(const metaclass &m, type_record *r) { r->metaclass = m.value; }
+};
+
+template <>
+struct process_attribute<module_local> : process_attribute_default<module_local> {
+    static void init(const module_local &l, type_record *r) { r->module_local = l.value; }
+};
+
+/// Process an 'arithmetic' attribute for enums (does nothing here)
+template <>
+struct process_attribute<arithmetic> : process_attribute_default<arithmetic> {};
+
+template <typename... Ts>
+struct process_attribute<call_guard<Ts...>> : process_attribute_default<call_guard<Ts...>> { };
+
+/**
+ * Process a keep_alive call policy -- invokes keep_alive_impl during the
+ * pre-call handler if both Nurse, Patient != 0 and use the post-call handler
+ * otherwise
+ */
+template <size_t Nurse, size_t Patient> struct process_attribute<keep_alive<Nurse, Patient>> : public process_attribute_default<keep_alive<Nurse, Patient>> {
+    template <size_t N = Nurse, size_t P = Patient, enable_if_t<N != 0 && P != 0, int> = 0>
+    static void precall(function_call &call) { keep_alive_impl(Nurse, Patient, call, handle()); }
+    template <size_t N = Nurse, size_t P = Patient, enable_if_t<N != 0 && P != 0, int> = 0>
+    static void postcall(function_call &, handle) { }
+    template <size_t N = Nurse, size_t P = Patient, enable_if_t<N == 0 || P == 0, int> = 0>
+    static void precall(function_call &) { }
+    template <size_t N = Nurse, size_t P = Patient, enable_if_t<N == 0 || P == 0, int> = 0>
+    static void postcall(function_call &call, handle ret) { keep_alive_impl(Nurse, Patient, call, ret); }
+};
+
+/// Recursively iterate over variadic template arguments
+template <typename... Args> struct process_attributes {
+    static void init(const Args&... args, function_record *r) {
+        int unused[] = { 0, (process_attribute<typename std::decay<Args>::type>::init(args, r), 0) ... };
+        ignore_unused(unused);
+    }
+    static void init(const Args&... args, type_record *r) {
+        int unused[] = { 0, (process_attribute<typename std::decay<Args>::type>::init(args, r), 0) ... };
+        ignore_unused(unused);
+    }
+    static void precall(function_call &call) {
+        int unused[] = { 0, (process_attribute<typename std::decay<Args>::type>::precall(call), 0) ... };
+        ignore_unused(unused);
+    }
+    static void postcall(function_call &call, handle fn_ret) {
+        int unused[] = { 0, (process_attribute<typename std::decay<Args>::type>::postcall(call, fn_ret), 0) ... };
+        ignore_unused(unused);
+    }
+};
+
+template <typename T>
+using is_call_guard = is_instantiation<call_guard, T>;
+
+/// Extract the ``type`` from the first `call_guard` in `Extras...` (or `void_type` if none found)
+template <typename... Extra>
+using extract_guard_t = typename exactly_one_t<is_call_guard, call_guard<>, Extra...>::type;
+
+/// Check the number of named arguments at compile time
+template <typename... Extra,
+          size_t named = constexpr_sum(std::is_base_of<arg, Extra>::value...),
+          size_t self  = constexpr_sum(std::is_same<is_method, Extra>::value...)>
+constexpr bool expected_num_args(size_t nargs, bool has_args, bool has_kwargs) {
+    return named == 0 || (self + named + has_args + has_kwargs) == nargs;
+}
+
+NAMESPACE_END(detail)
+NAMESPACE_END(PYBIND11_NAMESPACE)

dlib/external/pybind11/include/pybind11/buffer_info.h

+/*
+    pybind11/buffer_info.h: Python buffer object interface
+
+    Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "detail/common.h"
+
+NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+
+/// Information record describing a Python buffer object
+struct buffer_info {
+    void *ptr = nullptr;          // Pointer to the underlying storage
+    ssize_t itemsize = 0;         // Size of individual items in bytes
+    ssize_t size = 0;             // Total number of entries
+    std::string format;           // For homogeneous buffers, this should be set to format_descriptor<T>::format()
+    ssize_t ndim = 0;             // Number of dimensions
+    std::vector<ssize_t> shape;   // Shape of the tensor (1 entry per dimension)
+    std::vector<ssize_t> strides; // Number of entries between adjacent entries (for each per dimension)
+
+    buffer_info() { }
+
+    buffer_info(void *ptr, ssize_t itemsize, const std::string &format, ssize_t ndim,
+                detail::any_container<ssize_t> shape_in, detail::any_container<ssize_t> strides_in)
+    : ptr(ptr), itemsize(itemsize), size(1), format(format), ndim(ndim),
+      shape(std::move(shape_in)), strides(std::move(strides_in)) {
+        if (ndim != (ssize_t) shape.size() || ndim != (ssize_t) strides.size())
+            pybind11_fail("buffer_info: ndim doesn't match shape and/or strides length");
+        for (size_t i = 0; i < (size_t) ndim; ++i)
+            size *= shape[i];
+    }
+
+    template <typename T>
+    buffer_info(T *ptr, detail::any_container<ssize_t> shape_in, detail::any_container<ssize_t> strides_in)
+    : buffer_info(private_ctr_tag(), ptr, sizeof(T), format_descriptor<T>::format(), static_cast<ssize_t>(shape_in->size()), std::move(shape_in), std::move(strides_in)) { }
+
+    buffer_info(void *ptr, ssize_t itemsize, const std::string &format, ssize_t size)
+    : buffer_info(ptr, itemsize, format, 1, {size}, {itemsize}) { }
+
+    template <typename T>
+    buffer_info(T *ptr, ssize_t size)
+    : buffer_info(ptr, sizeof(T), format_descriptor<T>::format(), size) { }
+
+    explicit buffer_info(Py_buffer *view, bool ownview = true)
+    : buffer_info(view->buf, view->itemsize, view->format, view->ndim,
+            {view->shape, view->shape + view->ndim}, {view->strides, view->strides + view->ndim}) {
+        this->view = view;
+        this->ownview = ownview;
+    }
+
+    buffer_info(const buffer_info &) = delete;
+    buffer_info& operator=(const buffer_info &) = delete;
+
+    buffer_info(buffer_info &&other) {
+        (*this) = std::move(other);
+    }
+
+    buffer_info& operator=(buffer_info &&rhs) {
+        ptr = rhs.ptr;
+        itemsize = rhs.itemsize;
+        size = rhs.size;
+        format = std::move(rhs.format);
+        ndim = rhs.ndim;
+        shape = std::move(rhs.shape);
+        strides = std::move(rhs.strides);
+        std::swap(view, rhs.view);
+        std::swap(ownview, rhs.ownview);
+        return *this;
+    }
+
+    ~buffer_info() {
+        if (view && ownview) { PyBuffer_Release(view); delete view; }
+    }
+
+private:
+    struct private_ctr_tag { };
+
+    buffer_info(private_ctr_tag, void *ptr, ssize_t itemsize, const std::string &format, ssize_t ndim,
+                detail::any_container<ssize_t> &&shape_in, detail::any_container<ssize_t> &&strides_in)
+    : buffer_info(ptr, itemsize, format, ndim, std::move(shape_in), std::move(strides_in)) { }
+
+    Py_buffer *view = nullptr;
+    bool ownview = false;
+};
+
+NAMESPACE_BEGIN(detail)
+
+template <typename T, typename SFINAE = void> struct compare_buffer_info {
+    static bool compare(const buffer_info& b) {
+        return b.format == format_descriptor<T>::format() && b.itemsize == (ssize_t) sizeof(T);
+    }
+};
+
+template <typename T> struct compare_buffer_info<T, detail::enable_if_t<std::is_integral<T>::value>> {
+    static bool compare(const buffer_info& b) {
+        return (size_t) b.itemsize == sizeof(T) && (b.format == format_descriptor<T>::value ||
+            ((sizeof(T) == sizeof(long)) && b.format == (std::is_unsigned<T>::value ? "L" : "l")) ||
+            ((sizeof(T) == sizeof(size_t)) && b.format == (std::is_unsigned<T>::value ? "N" : "n")));
+    }
+};
+
+NAMESPACE_END(detail)
+NAMESPACE_END(PYBIND11_NAMESPACE)

dlib/external/pybind11/include/pybind11/chrono.h

+/*
+    pybind11/chrono.h: Transparent conversion between std::chrono and python's datetime
+
+    Copyright (c) 2016 Trent Houliston <trent@houliston.me> and
+                       Wenzel Jakob <wenzel.jakob@epfl.ch>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "pybind11.h"
+#include <cmath>
+#include <ctime>
+#include <chrono>
+#include <datetime.h>
+
+// Backport the PyDateTime_DELTA functions from Python3.3 if required
+#ifndef PyDateTime_DELTA_GET_DAYS
+#define PyDateTime_DELTA_GET_DAYS(o)         (((PyDateTime_Delta*)o)->days)
+#endif
+#ifndef PyDateTime_DELTA_GET_SECONDS
+#define PyDateTime_DELTA_GET_SECONDS(o)      (((PyDateTime_Delta*)o)->seconds)
+#endif
+#ifndef PyDateTime_DELTA_GET_MICROSECONDS
+#define PyDateTime_DELTA_GET_MICROSECONDS(o) (((PyDateTime_Delta*)o)->microseconds)
+#endif
+
+NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+NAMESPACE_BEGIN(detail)
+
+template <typename type> class duration_caster {
+public:
+    typedef typename type::rep rep;
+    typedef typename type::period period;
+
+    typedef std::chrono::duration<uint_fast32_t, std::ratio<86400>> days;
+
+    bool load(handle src, bool) {
+        using namespace std::chrono;
+
+        // Lazy initialise the PyDateTime import
+        if (!PyDateTimeAPI) { PyDateTime_IMPORT; }
+
+        if (!src) return false;
+        // If invoked with datetime.delta object
+        if (PyDelta_Check(src.ptr())) {
+            value = type(duration_cast<duration<rep, period>>(
+                  days(PyDateTime_DELTA_GET_DAYS(src.ptr()))
+                + seconds(PyDateTime_DELTA_GET_SECONDS(src.ptr()))
+                + microseconds(PyDateTime_DELTA_GET_MICROSECONDS(src.ptr()))));
+            return true;
+        }
+        // If invoked with a float we assume it is seconds and convert
+        else if (PyFloat_Check(src.ptr())) {
+            value = type(duration_cast<duration<rep, period>>(duration<double>(PyFloat_AsDouble(src.ptr()))));
+            return true;
+        }
+        else return false;
+    }
+
+    // If this is a duration just return it back
+    static const std::chrono::duration<rep, period>& get_duration(const std::chrono::duration<rep, period> &src) {
+        return src;
+    }
+
+    // If this is a time_point get the time_since_epoch
+    template <typename Clock> static std::chrono::duration<rep, period> get_duration(const std::chrono::time_point<Clock, std::chrono::duration<rep, period>> &src) {
+        return src.time_since_epoch();
+    }
+
+    static handle cast(const type &src, return_value_policy /* policy */, handle /* parent */) {
+        using namespace std::chrono;
+
+        // Use overloaded function to get our duration from our source
+        // Works out if it is a duration or time_point and get the duration
+        auto d = get_duration(src);
+
+        // Lazy initialise the PyDateTime import
+        if (!PyDateTimeAPI) { PyDateTime_IMPORT; }
+
+        // Declare these special duration types so the conversions happen with the correct primitive types (int)
+        using dd_t = duration<int, std::ratio<86400>>;
+        using ss_t = duration<int, std::ratio<1>>;
+        using us_t = duration<int, std::micro>;
+
+        auto dd = duration_cast<dd_t>(d);
+        auto subd = d - dd;
+        auto ss = duration_cast<ss_t>(subd);
+        auto us = duration_cast<us_t>(subd - ss);
+        return PyDelta_FromDSU(dd.count(), ss.count(), us.count());
+    }
+
+    PYBIND11_TYPE_CASTER(type, _("datetime.timedelta"));
+};
+
+// This is for casting times on the system clock into datetime.datetime instances
+template <typename Duration> class type_caster<std::chrono::time_point<std::chrono::system_clock, Duration>> {
+public:
+    typedef std::chrono::time_point<std::chrono::system_clock, Duration> type;
+    bool load(handle src, bool) {
+        using namespace std::chrono;
+
+        // Lazy initialise the PyDateTime import
+        if (!PyDateTimeAPI) { PyDateTime_IMPORT; }
+
+        if (!src) return false;
+        if (PyDateTime_Check(src.ptr())) {
+            std::tm cal;
+            cal.tm_sec   = PyDateTime_DATE_GET_SECOND(src.ptr());
+            cal.tm_min   = PyDateTime_DATE_GET_MINUTE(src.ptr());
+            cal.tm_hour  = PyDateTime_DATE_GET_HOUR(src.ptr());
+            cal.tm_mday  = PyDateTime_GET_DAY(src.ptr());
+            cal.tm_mon   = PyDateTime_GET_MONTH(src.ptr()) - 1;
+            cal.tm_year  = PyDateTime_GET_YEAR(src.ptr()) - 1900;
+            cal.tm_isdst = -1;
+
+            value = system_clock::from_time_t(std::mktime(&cal)) + microseconds(PyDateTime_DATE_GET_MICROSECOND(src.ptr()));
+            return true;
+        }
+        else return false;
+    }
+
+    static handle cast(const std::chrono::time_point<std::chrono::system_clock, Duration> &src, return_value_policy /* policy */, handle /* parent */) {
+        using namespace std::chrono;
+
+        // Lazy initialise the PyDateTime import
+        if (!PyDateTimeAPI) { PyDateTime_IMPORT; }
+
+        std::time_t tt = system_clock::to_time_t(src);
+        // this function uses static memory so it's best to copy it out asap just in case
+        // otherwise other code that is using localtime may break this (not just python code)
+        std::tm localtime = *std::localtime(&tt);
+
+        // Declare these special duration types so the conversions happen with the correct primitive types (int)
+        using us_t = duration<int, std::micro>;
+
+        return PyDateTime_FromDateAndTime(localtime.tm_year + 1900,
+                                          localtime.tm_mon + 1,
+                                          localtime.tm_mday,
+                                          localtime.tm_hour,
+                                          localtime.tm_min,
+                                          localtime.tm_sec,
+                                          (duration_cast<us_t>(src.time_since_epoch() % seconds(1))).count());
+    }
+    PYBIND11_TYPE_CASTER(type, _("datetime.datetime"));
+};
+
+// Other clocks that are not the system clock are not measured as datetime.datetime objects
+// since they are not measured on calendar time. So instead we just make them timedeltas
+// Or if they have passed us a time as a float we convert that
+template <typename Clock, typename Duration> class type_caster<std::chrono::time_point<Clock, Duration>>
+: public duration_caster<std::chrono::time_point<Clock, Duration>> {
+};
+
+template <typename Rep, typename Period> class type_caster<std::chrono::duration<Rep, Period>>
+: public duration_caster<std::chrono::duration<Rep, Period>> {
+};
+
+NAMESPACE_END(detail)
+NAMESPACE_END(PYBIND11_NAMESPACE)

dlib/external/pybind11/include/pybind11/common.h

+#include "detail/common.h"
+#warning "Including 'common.h' is deprecated. It will be removed in v3.0. Use 'pybind11.h'."

dlib/external/pybind11/include/pybind11/complex.h

+/*
+    pybind11/complex.h: Complex number support
+
+    Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "pybind11.h"
+#include <complex>
+
+/// glibc defines I as a macro which breaks things, e.g., boost template names
+#ifdef I
+#  undef I
+#endif
+
+NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+
+template <typename T> struct format_descriptor<std::complex<T>, detail::enable_if_t<std::is_floating_point<T>::value>> {
+    static constexpr const char c = format_descriptor<T>::c;
+    static constexpr const char value[3] = { 'Z', c, '\0' };
+    static std::string format() { return std::string(value); }
+};
+
+#ifndef PYBIND11_CPP17
+
+template <typename T> constexpr const char format_descriptor<
+    std::complex<T>, detail::enable_if_t<std::is_floating_point<T>::value>>::value[3];
+
+#endif
+
+NAMESPACE_BEGIN(detail)
+
+template <typename T> struct is_fmt_numeric<std::complex<T>, detail::enable_if_t<std::is_floating_point<T>::value>> {
+    static constexpr bool value = true;
+    static constexpr int index = is_fmt_numeric<T>::index + 3;
+};
+
+template <typename T> class type_caster<std::complex<T>> {
+public:
+    bool load(handle src, bool convert) {
+        if (!src)
+            return false;
+        if (!convert && !PyComplex_Check(src.ptr()))
+            return false;
+        Py_complex result = PyComplex_AsCComplex(src.ptr());
+        if (result.real == -1.0 && PyErr_Occurred()) {
+            PyErr_Clear();
+            return false;
+        }
+        value = std::complex<T>((T) result.real, (T) result.imag);
+        return true;
+    }
+
+    static handle cast(const std::complex<T> &src, return_value_policy /* policy */, handle /* parent */) {
+        return PyComplex_FromDoubles((double) src.real(), (double) src.imag());
+    }
+
+    PYBIND11_TYPE_CASTER(std::complex<T>, _("complex"));
+};
+NAMESPACE_END(detail)
+NAMESPACE_END(PYBIND11_NAMESPACE)

dlib/external/pybind11/include/pybind11/detail/descr.h

+/*
+    pybind11/detail/descr.h: Helper type for concatenating type signatures at compile time
+
+    Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "common.h"
+
+NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+NAMESPACE_BEGIN(detail)
+
+#if !defined(_MSC_VER)
+#  define PYBIND11_DESCR_CONSTEXPR static constexpr
+#else
+#  define PYBIND11_DESCR_CONSTEXPR const
+#endif
+
+/* Concatenate type signatures at compile time */
+template <size_t N, typename... Ts>
+struct descr {
+    char text[N + 1];
+
+    constexpr descr() : text{'\0'} { }
+    constexpr descr(char const (&s)[N+1]) : descr(s, make_index_sequence<N>()) { }
+
+    template <size_t... Is>
+    constexpr descr(char const (&s)[N+1], index_sequence<Is...>) : text{s[Is]..., '\0'} { }
+
+    template <typename... Chars>
+    constexpr descr(char c, Chars... cs) : text{c, static_cast<char>(cs)..., '\0'} { }
+
+    static constexpr std::array<const std::type_info *, sizeof...(Ts) + 1> types() {
+        return {{&typeid(Ts)..., nullptr}};
+    }
+};
+
+template <size_t N1, size_t N2, typename... Ts1, typename... Ts2, size_t... Is1, size_t... Is2>
+constexpr descr<N1 + N2, Ts1..., Ts2...> plus_impl(const descr<N1, Ts1...> &a, const descr<N2, Ts2...> &b,
+                                                   index_sequence<Is1...>, index_sequence<Is2...>) {
+    return {a.text[Is1]..., b.text[Is2]...};
+}
+
+template <size_t N1, size_t N2, typename... Ts1, typename... Ts2>
+constexpr descr<N1 + N2, Ts1..., Ts2...> operator+(const descr<N1, Ts1...> &a, const descr<N2, Ts2...> &b) {
+    return plus_impl(a, b, make_index_sequence<N1>(), make_index_sequence<N2>());
+}
+
+template <size_t N>
+constexpr descr<N - 1> _(char const(&text)[N]) { return descr<N - 1>(text); }
+constexpr descr<0> _(char const(&)[1]) { return {}; }
+
+template <size_t Rem, size_t... Digits> struct int_to_str : int_to_str<Rem/10, Rem%10, Digits...> { };
+template <size_t...Digits> struct int_to_str<0, Digits...> {
+    static constexpr auto digits = descr<sizeof...(Digits)>(('0' + Digits)...);
+};
+
+// Ternary description (like std::conditional)
+template <bool B, size_t N1, size_t N2>
+constexpr enable_if_t<B, descr<N1 - 1>> _(char const(&text1)[N1], char const(&)[N2]) {
+    return _(text1);
+}
+template <bool B, size_t N1, size_t N2>
+constexpr enable_if_t<!B, descr<N2 - 1>> _(char const(&)[N1], char const(&text2)[N2]) {
+    return _(text2);
+}
+
+template <bool B, typename T1, typename T2>
+constexpr enable_if_t<B, T1> _(const T1 &d, const T2 &) { return d; }
+template <bool B, typename T1, typename T2>
+constexpr enable_if_t<!B, T2> _(const T1 &, const T2 &d) { return d; }
+
+template <size_t Size> auto constexpr _() -> decltype(int_to_str<Size / 10, Size % 10>::digits) {
+    return int_to_str<Size / 10, Size % 10>::digits;
+}
+
+template <typename Type> constexpr descr<1, Type> _() { return {'%'}; }
+
+constexpr descr<0> concat() { return {}; }
+
+template <size_t N, typename... Ts>
+constexpr descr<N, Ts...> concat(const descr<N, Ts...> &descr) { return descr; }
+
+template <size_t N, typename... Ts, typename... Args>
+constexpr auto concat(const descr<N, Ts...> &d, const Args &...args)
+    -> decltype(std::declval<descr<N + 2, Ts...>>() + concat(args...)) {
+    return d + _(", ") + concat(args...);
+}
+
+template <size_t N, typename... Ts>
+constexpr descr<N + 2, Ts...> type_descr(const descr<N, Ts...> &descr) {
+    return _("{") + descr + _("}");
+}
+
+NAMESPACE_END(detail)
+NAMESPACE_END(PYBIND11_NAMESPACE)