std::filesystem link error on ubuntu 18.10

Question

I learning usage of C++ filesystem library (std::filesystem). The following code cause linker error.

How I can fix it?

Code for fs.cpp:

#include <iostream>
#include <filesystem>
#include <algorithm>
#include <iterator>

int main() {
    using namespace std::filesystem;

    directory_iterator iter{"."};
    for (auto& ent: iter) {
        std::cout << ent.path() << std::endl;
    }
}

Error output:

/usr/bin/ld: /tmp/cc7vhf9X.o: in function `main':
fs.cpp:(.text+0x10b): undefined reference to `std::filesystem::__cxx11::directory_iterator::operator*() const'
/usr/bin/ld: fs.cpp:(.text+0x151): undefined reference to `std::filesystem::__cxx11::directory_iterator::operator++()'
/usr/bin/ld: /tmp/cc7vhf9X.o: in function `std::filesystem::__cxx11::directory_iterator::directory_iterator(std::filesystem::__cxx11::path const&)':
fs.cpp:(.text._ZNSt10filesystem7__cxx1118directory_iteratorC2ERKNS0_4pathE[_ZNSt10filesystem7__cxx1118directory_iteratorC5ERKNS0_4pathE]+0x26): undefined reference to `std::filesystem::__cxx11::directory_iterator::directory_iterator(std::filesystem::__cxx11::path
const&, std::filesystem::directory_options, std::error_code*)'
/usr/bin/ld: /tmp/cc7vhf9X.o: in function `std::filesystem::__cxx11::path::path<char [2], std::filesystem::__cxx11::path>(char const (&) [2], std::filesystem::__cxx11::path::format)':
fs.cpp:(.text._ZNSt10filesystem7__cxx114pathC2IA2_cS1_EERKT_NS1_6formatE[_ZNSt10filesystem7__cxx114pathC5IA2_cS1_EERKT_NS1_6formatE]+0x6d): undefined reference to `std::filesystem::__cxx11::path::_M_split_cmpts()'
collect2: error: ld returned 1 exit status

Environment:

Ubuntu 18.10
g++ 8.2.0
compile options: g++ -std=c++17 -o fs fs.cpp

As this duplicate has libstdc++ and libc++ answers. – Matthieu Brucher Dec 19 '18 at 14:02 — Matthieu Brucher, Dec 19 '18 at 14:02
GCC 8 still needs `-lstdc++fs` – metalfox Dec 19 '18 at 14:02 — metalfox, Dec 19 '18 at 14:02
They will probably require it until C++20. – Matthieu Brucher Dec 19 '18 at 14:06 — Matthieu Brucher, Dec 19 '18 at 14:06

score 25 · Answer 1 · answered Dec 19 '18 at 14:09

25

It need to add -lstdc++fs to option.

g++ -lstdc++fs -std=c++17 -o fs fs.cpp -lstdc++fs

answered Dec 19 '18 at 14:09

KiYugadgeter

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std::filesystem link error on ubuntu 18.10

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