Compile error (again) with GNULIB_NAMESPACE and C++ and Mingw

[Christian Biesinger]

Hello!

This was previously fixed but I again see a compile error (with gnulib
at 4fcedca004fd13aecb5c6f235a988a5548bcb9a4)

In file included from /usr/share/mingw-w64/include/io.h:10,
                 from gnulib/import/stdio.h:146,
                 from gnulib/import/wchar.h:80,
                 from
/usr/lib/gcc/x86_64-w64-mingw32/8.3-win32/include/c++/cwchar:44,
                 from
/usr/lib/gcc/x86_64-w64-mingw32/8.3-win32/include/c++/bits/postypes.h:40,
                 from
/usr/lib/gcc/x86_64-w64-mingw32/8.3-win32/include/c++/iosfwd:40,
                 from
/usr/lib/gcc/x86_64-w64-mingw32/8.3-win32/include/c++/ios:38,
                 from
/usr/lib/gcc/x86_64-w64-mingw32/8.3-win32/include/c++/istream:38,
                 from
/usr/lib/gcc/x86_64-w64-mingw32/8.3-win32/include/c++/sstream:38,
                 from test.cc:4:
gnulib/import/wctype.h: In member function
‘gnulib::_gl_iswdigit_wrapper::operator
gnulib::_gl_iswdigit_wrapper::type() const’:
gnulib/import/wctype.h:1007:1: error: invalid conversion from ‘int
(*)(wint_t)’ {aka ‘int (*)(short unsigned int)’} to
‘gnulib::_gl_iswdigit_wrapper::type’ {aka ‘int (*)(unsigned int)’}
[-fpermissive]
 _GL_CXXALIAS_SYS (iswdigit, int, (wint_t wc));
 ^~~~~~~~~~~~~~~~
gnulib/import/wctype.h: In member function
‘gnulib::_gl_iswxdigit_wrapper::operator
gnulib::_gl_iswxdigit_wrapper::type() const’:
gnulib/import/wctype.h:1042:1: error: invalid conversion from ‘int
(*)(wint_t)’ {aka ‘int (*)(short unsigned int)’} to
‘gnulib::_gl_iswxdigit_wrapper::type’ {aka ‘int (*)(unsigned int)’}
[-fpermissive]
 _GL_CXXALIAS_SYS (iswxdigit, int, (wint_t wc));
 ^~~~~~~~~~~~~~~~

This is my testcase:
#define GNULIB_NAMESPACE gnulib

#include <config.h>
#include <sstream>

Compile with x86_64-w64-mingw32-g++ test.cc -I gnulib/import/ -I
../gnulib/import/ -I gnulib

We have these modules enabled:
IMPORTED_GNULIB_MODULES="\
    alloca \
    canonicalize-lgpl \
    dirent \
    dirfd \
    errno \
    fnmatch-gnu \
    frexpl \
    getcwd \
    glob \
    inet_ntop
    inttypes \
    lstat \
    limits-h \
    memchr \
    memmem \
    mkdir \
    mkdtemp \
    mkostemp \
    pathmax \
    rawmemchr \
    readlink \
    rename \
    setenv \
    signal-h \
    strchrnul \
    strerror_r-posix \
    strstr \
    strtok_r \
    sys_stat \
    time_r \
    unistd \
    unsetenv \
    update-copyright \
    wchar \
    wctype-h \
"

Thanks,
Christian