Why am I Getting a Linker Error When Using `experimental::filesystem` in C 1z?

experimental::filesystem Linker Error in C 1z

In attempting to utilize the latest C 1z features amidst the ongoing development of GCC 6.0, a peculiar linker error arises when compiling a sample code involving the experimental::filesystem header.

The issue manifests itself when running the following code:

#include <iostream>
#include <experimental/filesystem>
namespace fs = std::experimental::filesystem;
int main()
{
    fs::path p1 = "/home/pete/checkit";
    std::cout << "p1 = " << p1 << std::endl;
}

Compiling this code results in the following error:

undefined reference to `std::experimental::filesystem::v1::__cxx11::path::_M_split_cmpts()'

Resolution:

Contrary to the initial assumption, the Filesystem TS is not affiliated with C 1z but rather constitutes a distinct specification. The GCC implementation of the Filesystem TS is accessible in C 11 mode. To resolve the linking error, the following flag should be added to the linking command:

-lstdc++fs

This instruction guarantees that the program links against the appropriate library containing the necessary implementation for the experimental::filesystem header.

Update:

Subsequent versions of GCC (8.x and above) introduce support for the C 17 Filesystem library. It is accessible via the header and the std::filesystem namespace. Until this implementation achieves stability, linking against -lstdc fs remains necessary to utilize these features.

As of GCC 9, the C 17 std::filesystem components can be used without -lstdc fs, while std::experimental::filesystem symbols are made available through -lstdc exp in GCC 13.3.

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