From 2d81495508b67fc3d3b56f118c956c9f8589b6fe Mon Sep 17 00:00:00 2001 From: Carles Fernandez Date: Mon, 10 Jun 2019 21:45:59 +0200 Subject: [PATCH] Add CMake module to detect std::filesystem availability --- cmake/Modules/FindFILESYSTEM.cmake | 256 +++++++++++++++++++++++++++++ 1 file changed, 256 insertions(+) create mode 100644 cmake/Modules/FindFILESYSTEM.cmake diff --git a/cmake/Modules/FindFILESYSTEM.cmake b/cmake/Modules/FindFILESYSTEM.cmake new file mode 100644 index 000000000..ae52236e7 --- /dev/null +++ b/cmake/Modules/FindFILESYSTEM.cmake @@ -0,0 +1,256 @@ +# Copyright (C) 2019 (see AUTHORS file for a list of contributors) +# +# This file is part of GNSS-SDR. +# +# GNSS-SDR is free software: you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. +# +# GNSS-SDR is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with GNSS-SDR. If not, see . + +# Original Source: https://github.com/vector-of-bool/CMakeCM +# Modified by C. Fernandez-Prades. + +#[=======================================================================[.rst: + +FindFILESYSTEM +############## + +This module supports the C++17 standard library's filesystem utilities. Use the +:imp-target:`std::filesystem` imported target to + +Options +******* + +The ``COMPONENTS`` argument to this module supports the following values: + +.. find-component:: Experimental + :name: fs.Experimental + + Allows the module to find the "experimental" Filesystem TS version of the + Filesystem library. This is the library that should be used with the + ``std::experimental::filesystem`` namespace. + +.. find-component:: Final + :name: fs.Final + + Finds the final C++17 standard version of the filesystem library. + +If no components are provided, behaves as if the +:find-component:`fs.Final` component was specified. + +If both :find-component:`fs.Experimental` and :find-component:`fs.Final` are +provided, first looks for ``Final``, and falls back to ``Experimental`` in case +of failure. If ``Final`` is found, :imp-target:`std::filesystem` and all +:ref:`variables ` will refer to the ``Final`` version. + + +Imported Targets +**************** + +.. imp-target:: std::filesystem + + The ``std::filesystem`` imported target is defined when any requested + version of the C++ filesystem library has been found, whether it is + *Experimental* or *Final*. + + If no version of the filesystem library is available, this target will not + be defined. + + .. note:: + This target has ``cxx_std_17`` as an ``INTERFACE`` + :ref:`compile language standard feature `. Linking + to this target will automatically enable C++17 if no later standard + version is already required on the linking target. + + +.. _fs.variables: + +Variables +********* + +.. variable:: CXX_FILESYSTEM_IS_EXPERIMENTAL + + Set to ``TRUE`` when the :find-component:`fs.Experimental` version of C++ + filesystem library was found, otherwise ``FALSE``. + +.. variable:: CXX_FILESYSTEM_HAVE_FS + + Set to ``TRUE`` when a filesystem header was found. + +.. variable:: CXX_FILESYSTEM_HEADER + + Set to either ``filesystem`` or ``experimental/filesystem`` depending on + whether :find-component:`fs.Final` or :find-component:`fs.Experimental` was + found. + +.. variable:: CXX_FILESYSTEM_NAMESPACE + + Set to either ``std::filesystem`` or ``std::experimental::filesystem`` + depending on whether :find-component:`fs.Final` or + :find-component:`fs.Experimental` was found. + + +Examples +******** + +Using `find_package(FILESYSTEM)` with no component arguments: + +.. code-block:: cmake + + find_package(FILESYSTEM REQUIRED) + + add_executable(my-program main.cpp) + target_link_libraries(my-program PRIVATE std::filesystem) + + +#]=======================================================================] + + +if(TARGET std::filesystem) + # This module has already been processed. Don't do it again. + return() +endif() + +include(CMakePushCheckState) +include(CheckIncludeFileCXX) +include(CheckCXXSourceCompiles) + +cmake_push_check_state() + +set(CMAKE_REQUIRED_QUIET ${FILESYSTEM_FIND_QUIETLY}) + +# All of our tests require C++17 or later +set(OLD_CMAKE_CXX_STANDARD ${CMAKE_CXX_STANDARD}) +set(CMAKE_CXX_STANDARD 17) +if((CMAKE_CXX_COMPILER_ID STREQUAL "GNU") AND (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER "9.0.0")) + set(CMAKE_REQUIRED_FLAGS "-std=c++17") +endif() +if((CMAKE_CXX_COMPILER_ID STREQUAL "Clang") AND NOT (CMAKE_CXX_COMPILER_VERSION VERSION_LESS "8.99")) + set(CMAKE_REQUIRED_FLAGS "-std=c++17") +endif() + +# Normalize and check the component list we were given +set(want_components ${FILESYSTEM_FIND_COMPONENTS}) +if(FILESYSTEM_FIND_COMPONENTS STREQUAL "") + set(want_components Final) +endif() + +# Warn on any unrecognized components +set(extra_components ${want_components}) +list(REMOVE_ITEM extra_components Final Experimental) +foreach(component IN LISTS extra_components) + message(WARNING "Extraneous find_package component for FILESYSTEM: ${component}") +endforeach() + +# Detect which of Experimental and Final we should look for +set(find_experimental TRUE) +set(find_final TRUE) +if(NOT "Final" IN_LIST want_components) + set(find_final FALSE) +endif() +if(NOT "Experimental" IN_LIST want_components) + set(find_experimental FALSE) +endif() + +if(find_final) + check_include_file_cxx("filesystem" _CXX_FILESYSTEM_HAVE_HEADER) + mark_as_advanced(_CXX_FILESYSTEM_HAVE_HEADER) + if(_CXX_FILESYSTEM_HAVE_HEADER) + # We found the non-experimental header. Don't bother looking for the + # experimental one. + set(find_experimental FALSE) + endif() +else() + set(_CXX_FILESYSTEM_HAVE_HEADER FALSE) +endif() + +if(find_experimental) + check_include_file_cxx("experimental/filesystem" _CXX_FILESYSTEM_HAVE_EXPERIMENTAL_HEADER) + mark_as_advanced(_CXX_FILESYSTEM_HAVE_EXPERIMENTAL_HEADER) +else() + set(_CXX_FILESYSTEM_HAVE_EXPERIMENTAL_HEADER FALSE) +endif() + +if(_CXX_FILESYSTEM_HAVE_HEADER) + set(_have_fs TRUE) + set(_fs_header filesystem) + set(_fs_namespace std::filesystem) +elseif(_CXX_FILESYSTEM_HAVE_EXPERIMENTAL_HEADER) + set(_have_fs TRUE) + set(_fs_header experimental/filesystem) + set(_fs_namespace std::experimental::filesystem) +else() + set(_have_fs FALSE) +endif() + +set(CXX_FILESYSTEM_HAVE_FS ${_have_fs} CACHE BOOL "TRUE if we have the C++ filesystem headers") +set(CXX_FILESYSTEM_HEADER ${_fs_header} CACHE STRING "The header that should be included to obtain the filesystem APIs") +set(CXX_FILESYSTEM_NAMESPACE ${_fs_namespace} CACHE STRING "The C++ namespace that contains the filesystem APIs") + +set(_found FALSE) + +if(CXX_FILESYSTEM_HAVE_FS) + # We have some filesystem library available. Do link checks + string(CONFIGURE [[ + #include <@CXX_FILESYSTEM_HEADER@> + + int main() { + auto cwd = @CXX_FILESYSTEM_NAMESPACE@::current_path(); + return static_cast(cwd.string().size()); + } + ]] code @ONLY) + + # Try to compile a simple filesystem program without any linker flags + check_cxx_source_compiles("${code}" CXX_FILESYSTEM_NO_LINK_NEEDED) + + set(can_link ${CXX_FILESYSTEM_NO_LINK_NEEDED}) + + if(NOT CXX_FILESYSTEM_NO_LINK_NEEDED) + set(prev_libraries ${CMAKE_REQUIRED_LIBRARIES}) + set(CMAKE_REQUIRED_FLAGS "-std=c++17") + # Add the libstdc++ flag + set(CMAKE_REQUIRED_LIBRARIES ${prev_libraries} -lstdc++fs) + check_cxx_source_compiles("${code}" CXX_FILESYSTEM_STDCPPFS_NEEDED) + set(can_link ${CXX_FILESYSTEM_STDCPPFS_NEEDED}) + if(NOT CXX_FILESYSTEM_STDCPPFS_NEEDED) + # Try the libc++ flag + set(CMAKE_REQUIRED_LIBRARIES ${prev_libraries} -lc++fs) + check_cxx_source_compiles("${code}" CXX_FILESYSTEM_CPPFS_NEEDED) + set(can_link ${CXX_FILESYSTEM_CPPFS_NEEDED}) + endif() + endif() + + if(can_link) + add_library(std::filesystem INTERFACE IMPORTED) + target_compile_features(std::filesystem INTERFACE cxx_std_17) + set(_found TRUE) + + if(CXX_FILESYSTEM_NO_LINK_NEEDED) + # Nothing to add... + elseif(CXX_FILESYSTEM_STDCPPFS_NEEDED) + target_link_libraries(std::filesystem INTERFACE -lstdc++fs) + elseif(CXX_FILESYSTEM_CPPFS_NEEDED) + target_link_libraries(std::filesystem INTERFACE -lc++fs) + endif() + endif() +endif() + +if(NOT ${_found}) + set(CMAKE_CXX_STANDARD ${OLD_CMAKE_CXX_STANDARD}) +endif() + +cmake_pop_check_state() + +set(FILESYSTEM_FOUND ${_found} CACHE BOOL "TRUE if we can compile and link a program using std::filesystem" FORCE) + +if(FILESYSTEM_FIND_REQUIRED AND NOT FILESYSTEM_FOUND) + message(FATAL_ERROR "Cannot compile a simple program using std::filesystem") +endif()