c++ - 如何使用 cmake 确保 C++14 编译器与实验文件系统 TS 库链接？

Question

我正在(切换到)使用 <std::experimental::filesystem>在我的 C++14 代码中，我需要能够在 Linux 上使用 GCC 5.x 构建它(以及任何支持 C++14 的编译器，或者至少 - 相关版本的 clang、msvc 和可能的 icc) .

现在，当我链接时，我收到关于丢失所有文件系统相关符号的错误，例如:

foo.cpp:(.text+0x9cd): undefined reference to `std::experimental::filesystem::v1::__cxx11::path::_M_split_cmpts()'

现在，如果我“手动”添加对 libstdc++fs 的依赖项:

target_link_libraries(foo other_lib stdc++fs)

然后一切都正常链接 - 但我如何将其推广到任何支持 C++14 的编译器？

注:我的相关部分CMakeLists.txt看起来像这样:

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall" )
set(CMAKE_CXX_STANDARD 14)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF)

add_library(bar src/bar.cpp)
add_executable(foo src/foo.cpp)
target_link_libraries(foo bar other_lib)

---

<子>*(当我使用 boost::filesystem 时，它反而更容易 - 我只需要使用 FindBoost.cmake 产生的任何东西。)
** 使用 -Wall我猜对其他编译器来说也是一个问题。

Answer 1

不幸的是，这正是它的用途。参见 the relevant part of libstdc++ documentation :

GCC 5.3 includes an implementation of the Filesystem library defined by the technical specification ISO/IEC TS 18822:2015. Because this is an experimental library extension, not part of the C++ standard, it is implemented in a separate library, libstdc++fs.a, and there is no shared library for it. To use the library you should include and link with -lstdc++fs. The library implementation is incomplete on non-POSIX platforms, specifically Windows support is rudimentary.

Due to the experimental nature of the Filesystem library the usual guarantees about ABI stability and backwards compatibility do not apply to it. There is no guarantee that the components in any header will remain compatible between different GCC releases.

(强调我的)

要仅在 GCC 下显式链接 libstdc++fs，您可以使用 relevant CMake variable :

target_link_libraries(foo other_lib)
if (CMAKE_CXX_COMPILER_ID STREQUAL GNU)
    target_link_libraries(foo stdc++fs)
endif()

或者，以一种更奇特的方式，

if (CMAKE_CXX_COMPILER_ID STREQUAL GNU)
    set(CXX_FILESYSTEM_LIBRARIES stdc++fs)
else()
    set(CXX_FILESYSTEM_LIBRARIES)
endif()
target_link_libraries(foo other_lib ${CXX_FILESYSTEM_LIBRARIES})