'std::filesystem' 在包含 <experimental/filesystem> 后没有被声明

2021-12-26 00:00:00 cmake c++ c++17

我查了很多关于c++17下文件系统链接的问题，还是不能成功链接.我的 main.cpp 文件如下.

I have checked a lot of issues about the link of filesystem under c++17 and I still cannot make the link successfully. My main.cpp file is as the following.

#include <experimental/filesystem>


int main(int argc, char** argv)
{
    std::string imageDirectory = "./image";;
    std::vector<std::string> imagePath;

    for (const auto& entry: std::filesystem::directory_iterator(imageDirectory))
    {
        imagePath.push_back(entry.path());
        std::cout << entry.path() << std::endl;
    }

    return 0;
}

我的 CMakeLists.txt 如下.

cmake_minimum_required(VERSION 3.8 FATAL_ERROR)

project(visual_hull LANGUAGES CXX)
set(CMAKE_CXX_STANDARD 17)
add_library(dataIO
        STATIC
            dataIO.hpp
            dataIO.cpp)

find_package(OpenCV REQUIRED core highgui imgproc)

target_link_libraries(dataIO ${OpenCV_LIBS})

add_executable(visual_hull main.cpp)

target_link_libraries(visual_hull PUBLIC dataIO
                                         stdc++fs)

错误如下.

/home/SENSETIME/zhangshunkang/Downloads/programming/c++/visual_hull/main.cpp: In function ‘int main(int, char**)’:
/home/SENSETIME/zhangshunkang/Downloads/programming/c++/visual_hull/main.cpp:15:31: error: ‘std::filesystem’ has not been declared
  for (const auto& entry: std::filesystem::directory_iterator(imageDirectory))
                               ^
CMakeFiles/visual_hull.dir/build.make:62: recipe for target 'CMakeFiles/visual_hull.dir/main.cpp.o' failed
make[2]: *** [CMakeFiles/visual_hull.dir/main.cpp.o] Error 1
CMakeFiles/Makefile2:72: recipe for target 'CMakeFiles/visual_hull.dir/all' failed
make[1]: *** [CMakeFiles/visual_hull.dir/all] Error 2
Makefile:83: recipe for target 'all' failed
make: *** [all] Error 2

推荐答案

您使用 std::filesystem::directory_iterator.std::filesystem::directory_iterator 和整个命名空间 std::filesystem 在头文件 中声明.

You use std::filesystem::directory_iterator. std::filesystem::directory_iterator and the entire namespace std::filesystem are declared in the header <filesystem>.

您尚未包含标题 .相反，您包含了 .这个头文件没有声明 std::filesystem::directory_iterator.相反，它声明了 std::experimental::filesystem::directory_iterator.

You haven't included the header <filesystem>. Instead, you've included <experimental/filesystem>. This header does not declare std::filesystem::directory_iterator. Instead, it declares std::experimental::filesystem::directory_iterator.

您可以始终使用标准文件系统库或技术规范中的实验文件系统库，但不得将它们混合在一起.如果您的目标是 C++17，那么您应该使用 .

You can consistently use either the standard filesystem library, or the experimental filesystem library from the technical specification, but you must not mix them together. If you're targeting C++17, then you should use <filesystem>.

我会得到文件系统的错误:没有这样的文件或目录

I will get the error that filesystem: No such file or directory

理想的解决方案是将编译器升级到对 C++17 提供非实验性支持的版本.否则使用实验性 TS 或 Boost.

The ideal solution is to upgrade your compiler to a version that has non-experimental support for C++17. Otherwise use the experimental TS or Boost.

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