Why does GCC not seem to have the filesystem standard library?

Question

i'm facing a problem with filesystem library, it should be included in c++17 compiler, after 2 days i tried to install gcc-7.0.2 in raspberry pi but it didn't work, it couldn't recognize the command gcc-7 or g++-7 or even -std=c++17 so i had to install g++-6 and gcc-6 using apt-get install anyway, after installing the 6 version the compiler include c++17. i'm using codeblocks as IDE, i had to add a new compiler and add the option -std=c++17 to enable it,but in the main code when i include the filesystem library it says no such file or directory.

my question is, how i can add the c++17 compiler and its library (like filesystem) correctly ??

Answer 1

GCC v7 still does not implement <filesystem> but it does have the Filesystem Technical Specification which is in <experimental/filesystem>

#include <experimental/filesystem>

// for brevity
namespace fs = std::experimental::filesystem;

int main()
{
    fs::path p = "/path/to/my/file"; // etc...
}

This is also available in GCC v6.

To link with the library you need to add -lstdc++fs to the command line.

Note: There may be some minor differences between the current Technical Specification and the final draft of <filesystem> that is decided upon by the Standards Committee.

Note 2: GCC v8 now implements <filesystem> with the -std=c++17 flag.

Answer 2

First you should take at look at C++17 Support in GCC

GCC 8

Runtime Library (libstdc++)

• Improved experimental support for C++17, including the following features:
  • Deduction guides to support class template argument deduction.
  • std::filesystem implementation.
  • std::char_traits<char> and std::char_traits<wchar_t> are usable in constant expressions.
  • std::to_chars and std::from_chars (for integers only, not for floating point types).

src: https://gcc.gnu.org/gcc-8/changes.html

GCC 9

Runtime Library (libstdc++)

• Improved support for C++17, including:
  • The C++17 implementation is no longer experimental.
  • Parallel algorithms and <execution> (requires Thread Building Blocks 2018 or newer).
  • <memory_resource>.
  • Using the types and functions in <filesystem> does not require linking with -lstdc++fs now.

src: https://gcc.gnu.org/gcc-9/changes.html