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# Distributed under the OSI-approved BSD 3-Clause License. See accompanying
# file Copyright.txt or https://cmake.org/licensing for details.
#
# Copied from:
# https://github.com/lethal-guitar/RigelEngine/blob/master/cmake/Modules/FindFilesystem.cmake
#
# Which is copied from:
# https://github.com/vector-of-bool/CMakeCM/blob/master/modules/FindFilesystem.cmake
#[=======================================================================[.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 <fs.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 <req-lang-standards>`. 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()
cmake_policy(PUSH)
if(POLICY CMP0067)
# pass CMAKE_CXX_STANDARD to check_cxx_source_compiles()
# has to appear before including CheckCXXSourceCompiles module
cmake_policy(SET CMP0067 NEW)
endif()
include(CMakePushCheckState)
include(CheckIncludeFileCXX)
include(CheckCXXSourceCompiles)
cmake_push_check_state()
set(CMAKE_REQUIRED_QUIET ${Filesystem_FIND_QUIETLY})
# All of our tests required C++17 or later
# But AC already sets this in ConfigureBaseTargets.cmake
# set(CMAKE_CXX_STANDARD 17)
# 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 ${_fs_namespace} CACHE STRING "The C++ namespace that contains the filesystem APIs")
set(_found FALSE)
if(CXX_FILESYSTEM_HAVE_FS)
# We have some filesystem library available. Do link checks
string(CONFIGURE [[
#include <@CXX_FILESYSTEM_HEADER@>
int main() {
auto cwd = @CXX_FILESYSTEM_NAMESPACE@::current_path();
return static_cast<int>(cwd.string().size());
}
]] code @ONLY)
# Try to compile a simple filesystem program without any linker flags
check_cxx_source_compiles("${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})
# 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)
# on certain linux distros we have a version of libstdc++ which has the final code for c++17 fs in the
# libstdc++.so.*. BUT when compiling with g++ < 9, we MUST still link with libstdc++fs.a
# libc++ should not suffer from this issue, so, in theory we should be fine with only checking for
# GCC's libstdc++
if((CMAKE_CXX_COMPILER_ID MATCHES "GNU") AND (CMAKE_CXX_COMPILER_VERSION VERSION_LESS "9.0.0"))
target_link_libraries(std::filesystem INTERFACE -lstdc++fs)
endif()
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()
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 simple program using std::filesystem")
endif()
cmake_policy(POP)
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