ptsname_r on Cygwin

[Bruno Haible]

Hi Ken,

On Cygwin 2.9 (64-bit) I see a test failure in test-ptsname_r.c, here:

  {
    char buffer[256];
    int result;

    result = ptsname_r (-1, buffer, sizeof buffer);
    ASSERT (result != 0);  // <======================== HERE
    ASSERT (result == EBADF || result == ENOTTY);
  }

While https://www.kernel.org/doc/man-pages/online/pages/man3/ptsname_r.3.html
says that ptsname_r, upon failure, should return an error code, on Cygwin,
it returns 0 and stores the empty string in 'buffer'.

This causes 2 test failures of Gnulib tests:


FAIL: test-ptsname
==================

../../gltests/test-ptsname.c:76: assertion 'result == NULL' failed
FAIL test-ptsname.exe (exit status: 134)

FAIL: test-ptsname_r
====================

../../gltests/test-ptsname_r.c:126: assertion 'result != 0' failed
FAIL test-ptsname_r.exe (exit status: 134)


Bruno