[Bug libstdc++/84159] filesystem::path::operator/= with has root directory path

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84159

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Tue May 15 12:07:09 2018
New Revision: 260255

URL: https://gcc.gnu.org/viewcvs?rev=260255&root=gcc&view=rev
Log:
PR libstdc++/84159 fix appending strings to paths

The path::operator/=(const Source&) and path::append overloads were
still following the semantics of the Filesystem TS not C++17. Only
the path::operator/=(const path&) overload was correct.

This change adds more tests for path::operator/=(const path&) and adds
new tests to verify that the other append operations have equivalent
behaviour.

        PR libstdc++/84159
        * include/bits/fs_path.h (path::operator/=, path::append): Construct
        temporary path before calling _M_append.
        (path::_M_append): Change parameter to path and implement C++17
        semantics.
        * testsuite/27_io/filesystem/path/append/path.cc: Add helper function
        and more examples from the standard.
        * testsuite/27_io/filesystem/path/append/source.cc: New.
        * testsuite/27_io/filesystem/path/decompose/filename.cc: Add comment.
        * testsuite/27_io/filesystem/path/nonmember/append.cc: New.

Added:
    trunk/libstdc++-v3/testsuite/27_io/filesystem/path/append/source.cc
    trunk/libstdc++-v3/testsuite/27_io/filesystem/path/nonmember/append.cc
      - copied, changed from r260254,
trunk/libstdc++-v3/testsuite/27_io/filesystem/path/append/path.cc
Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/include/bits/fs_path.h
    trunk/libstdc++-v3/testsuite/27_io/filesystem/path/append/path.cc
    trunk/libstdc++-v3/testsuite/27_io/filesystem/path/decompose/filename.cc