[Bug libstdc++/66011] New: call to '__open_missing_mode' declared with attribute error

["asolokha at gmx dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66011

            Bug ID: 66011
           Summary: call to '__open_missing_mode' declared with attribute
                    error
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---

gcc-6.0.0_alpha20150503 fails to build for powerpc-e500v2-linux-gnuspe target
inside libstdc++:

--------8<--------
libtool: compile:  powerpc-e500v2-linux-gnuspe-c++
-I/usr/powerpc-e500v2-linux-gnuspe/tmp/portage/sys-devel/gcc-6.0.0_alpha20150503/work/gcc-6-20150503/libstdc++-v3/../libgcc
-I/usr/powerpc-e500v2-linux-gnuspe/tmp/portage/sys-devel/gcc-6.0.0_alpha20150503/work/build/powerpc-e500v2-linux-gnuspe/libstdc++-v3/include/powerpc-e500v2-linux-gnuspe
-I/usr/powerpc-e500v2-linux-gnuspe/tmp/portage/sys-devel/gcc-6.0.0_alpha20150503/work/build/powerpc-e500v2-linux-gnuspe/libstdc++-v3/include
-I/usr/powerpc-e500v2-linux-gnuspe/tmp/portage/sys-devel/gcc-6.0.0_alpha20150503/work/gcc-6-20150503/libstdc++-v3/libsupc++
-D_GLIBCXX_SHARED -std=gnu++14 -Wall -Wextra -Wwrite-strings -Wcast-qual -Wabi
-fdiagnostics-show-location=once -ffunction-sections -fdata-sections
-frandom-seed=ops.lo -g -O2 -pipe -D_GNU_SOURCE -c
/usr/powerpc-e500v2-linux-gnuspe/tmp/portage/sys-devel/gcc-6.0.0_alpha20150503/work/gcc-6-20150503/libstdc++-v3/src/filesystem/ops.cc
 -fPIC -DPIC -D_GLIBCXX_SHARED -o ops.o
In file included from
/usr/powerpc-e500v2-linux-gnuspe/usr/include/fcntl.h:302:0,
                 from
/usr/powerpc-e500v2-linux-gnuspe/tmp/portage/sys-devel/gcc-6.0.0_alpha20150503/work/gcc-6-20150503/libstdc++-v3/src/filesystem/ops.cc:39:
In function 'int open(const char*, int, ...)',
    inlined from 'bool {anonymous}::do_copy_file(const
std::experimental::filesystem::v1::__cxx11::path&, const
std::experimental::filesystem::v1::__cxx11::path&,
std::experimental::filesystem::v1::copy_options, stat*, stat*,
std::error_code&)' at
/usr/powerpc-e500v2-linux-gnuspe/tmp/portage/sys-devel/gcc-6.0.0_alpha20150503/work/gcc-6-20150503/libstdc++-v3/src/filesystem/ops.cc:285:27:
/usr/powerpc-e500v2-linux-gnuspe/usr/include/bits/fcntl2.h:50:26: error: call
to '__open_missing_mode' declared with attribute error: open with O_CREAT in
second argument needs 3 arguments
    __open_missing_mode ();
                          ^
Makefile:481: recipe for target 'ops.lo' failed
make[5]: *** [ops.lo] Error 1
-------->8--------

As man open says,
> mode specifies the permissions to use in case a new file is created.
> This argument must be supplied when O_CREAT or O_TMPFILE is specified
> in flags; if neither O_CREAT nor O_TMPFILE is specified, then mode
> is ignored.
(and the similar wording can be found in Posix version).

Cross-compiler is 5.1.0. I can provide full build log if necessary.