ceph/cmake/modules/FindStdFilesystem.cmake
Kefu Chai bbd95765cc cmake: fix StdFilesystem detection
before this change, we fails to detect std::filesystem with clang++,
because  the cmake project created by try_compile() only expands
following options passed from its caller:
- COMPILE_DEFINITIONS
- INCLUDE_DIRECTORIES
- LINK_DIRECTORIES
- LINK_LIBRARIES

which do not include CMAKE_CXX_FLAGS, so either we need to (ab)use
COMPILE_DEFINITIONS for passing -std=c++17, or we can change the
CMAKE_CXX_FLAGS in the parent env, as it turns out the created cmake
project does inherit this flag from current project. in this change,
we use the COMPILE_DEFINITIONS approach: simpler this way. and we
can drop it once cmake 3.8 is required.

Signed-off-by: Kefu Chai <kchai@redhat.com>
2018-08-02 14:37:49 +08:00

52 lines
1.6 KiB
CMake

set(_std_filesystem_test_src
${CMAKE_CURRENT_LIST_DIR}/FindStdFilesystem_test.cc)
macro(try_std_filesystem_library _library _result)
if(CMAKE_VERSION VERSION_LESS "3.8")
# abuse the definition flags, because they are quite
# the same as CMAKE_C_FLAGS: they are passed to the
# compiler.
set(_std_filesystem_try_compile_arg
COMPILE_DEFINITIONS "-std=c++17")
else()
set(_std_filesystem_try_compile_arg
CXX_STANDARD 17)
endif()
try_compile(_std_filesystem_compiles
${CMAKE_CURRENT_BINARY_DIR}
SOURCES ${_std_filesystem_test_src}
LINK_LIBRARIES ${_library}
${_std_filesystem_try_compile_arg})
unset(_std_filesystem_try_compile_arg)
if(_std_filesystem_compiles)
set(${_result} ${_library})
endif()
unset(_std_filesystem_compiles)
endmacro()
if(NOT StdFilesystem_LIBRARY)
try_std_filesystem_library("stdc++fs" StdFilesystem_LIBRARY)
endif()
if(NOT StdFilesystem_LIBRARY)
try_std_filesystem_library("c++experimental" StdFilesystem_LIBRARY)
endif()
if(NOT StdFilesystem_LIBRARY)
try_std_filesystem_library("c++fs" StdFilesystem_LIBRARY)
endif()
unset(_std_filesystem_test_src)
include(FindPackageHandleStandardArgs)
find_package_handle_standard_args(StdFilesystem
FOUND_VAR StdFilesystem_FOUND
REQUIRED_VARS StdFilesystem_LIBRARY)
mark_as_advanced(StdFilesystem_LIBRARY)
if(StdFilesystem_FOUND AND NOT (TARGET StdFilesystem::filesystem))
add_library(StdFilesystem::filesystem INTERFACE IMPORTED)
set_target_properties(StdFilesystem::filesystem PROPERTIES
INTERFACE_LINK_LIBRARIES ${StdFilesystem_LIBRARY})
endif()