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# Ideas come from
#
# https://gitlab.kitware.com/cmake/cmake/-/issues/17834
#
# Basically, upstream CMake claims the fact that a separate library is
# needed for std::filesystem support is a short-lived fact (of all the
# platforms we use, only RHEL 8 uses a compiler where this is needed),
# hence they don't want a standardized way to detect std::filesystem
include(CheckSourceCompiles)
set( CMAKE_REQUIRED_INCLUDES "${XRootD_INCLUDE_DIR}" )
set( SAMPLE_FILESYSTEM "#include <cstdlib>
#include <filesystem>
int main() {
auto cwd = std::filesystem::current_path();
return cwd.empty();
}")
CHECK_SOURCE_COMPILES( CXX "${SAMPLE_FILESYSTEM}" CXX_FILESYSTEM_NO_LINK_NEEDED )
set( _found FALSE )
if( CXX_FILESYSTEM_NO_LINK_NEEDED )
set( _found TRUE )
else()
# Add the libstdc++ flag
set( CMAKE_REQUIRED_LIBRARIES "-lstdc++fs" )
CHECK_SOURCE_COMPILES( CXX "${SAMPLE_FILESYSTEM}" CXX_FILESYSTEM_STDCPPFS_NEEDED )
set( _found TRUE )
endif()
add_library( std::filesystem INTERFACE IMPORTED )
#set_property( TARGET std::filesystem APPEND PROPERTY INTERFACE_COMPILE_FEATURES cxx_std_17 )
if( CXX_FILESYSTEM_STDCPPFS_NEEDED )
set_property( TARGET std::filesystem APPEND PROPERTY INTERFACE_LINK_LIBRARIES -lstdc++fs )
endif()
set( Filesystem_FOUND ${_found} CACHE BOOL "TRUE if we can run a program using std::filesystem" FORCE )
if( Filesystem_FIND_REQUIRED AND NOT Filesystem_FOUND )
message( FATAL_ERROR "Cannot run simple program using std::filesystem" )
endif()
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