Brian Inglis wrote:
> Please note that latest bison built and passed all checks on latest 
> Cygwin 32.
> The issue is only with Cygwin 64.
> I consistently reproduced the SEGV @ 0x0000000100000000 with trashed 
> stack, in a gdb script.

Comparing the test failures that you got with those that I got, these
are those that are only in your env:
===============================================================================

FAIL: test-areadlinkat
======================

$HOME/src/cygwin/bison/dummy-0-0.x86_64/src/dummy-0/gltests/test-areadlink.h:39: assertion 'errno == ENOENT || errno == EINVAL' failed
Aborted (core dumped)
FAIL test-areadlinkat.exe (exit status: 134)

FAIL: test-areadlinkat-with-size
================================

$HOME/src/cygwin/bison/dummy-0-0.x86_64/src/dummy-0/gltests/test-areadlink.h:39: assertion 'errno == ENOENT || errno == EINVAL' failed
Aborted (core dumped)
FAIL test-areadlinkat-with-size.exe (exit status: 134)

FAIL: test-asyncsafe-spin2
==========================

Starting test_asyncsafe_spin ...Segmentation fault (core dumped)
FAIL test-asyncsafe-spin2.exe (exit status: 139)

FAIL: test-c-dtoastr.sh
=======================

$HOME/src/cygwin/bison/dummy-0-0.x86_64/src/dummy-0/build-aux/test-driver: 107: $HOME/src/cygwin/bison/dummy-0-0.x86_64/src/dummy-0/gltests/test-c-dtoastr.sh: Permission denied
FAIL test-c-dtoastr.sh (exit status: 126)

FAIL: test-c-ldtoastr.sh
========================

$HOME/src/cygwin/bison/dummy-0-0.x86_64/src/dummy-0/build-aux/test-driver: 107: $HOME/src/cygwin/bison/dummy-0-0.x86_64/src/dummy-0/gltests/test-c-ldtoastr.sh: Permission denied
FAIL test-c-ldtoastr.sh (exit status: 126)

FAIL: test-c32isgraph.sh
========================

$HOME/src/cygwin/bison/dummy-0-0.x86_64/src/dummy-0/gltests/test-c32isgraph.c:125: assertion 'is != 0' failed
Aborted (core dumped)
FAIL test-c32isgraph.sh (exit status: 1)

FAIL: test-cond
===============

Starting test_cond ...Segmentation fault (core dumped)
FAIL test-cond.exe (exit status: 139)

FAIL: test-execute.sh
=====================

Segmentation fault (core dumped)
test-execute.sh: test case 0 failed
Segmentation fault (core dumped)
test-execute.sh: test case 1 failed
Segmentation fault (core dumped)
test-execute.sh: test case 2 failed
Segmentation fault (core dumped)
test-execute.sh: test case 3 failed
Segmentation fault (core dumped)
test-execute.sh: test case 4 failed
Segmentation fault (core dumped)
test-execute.sh: test case 5 failed
Segmentation fault (core dumped)
test-execute.sh: test case 6 failed
Segmentation fault (core dumped)
test-execute.sh: test case 7 failed
Segmentation fault (core dumped)
test-execute.sh: test case 8 failed
Segmentation fault (core dumped)
test-execute.sh: test case 9 failed
Segmentation fault (core dumped)
test-execute.sh: test case 10 failed
Segmentation fault (core dumped)
test-execute.sh: test case 11 failed
Segmentation fault (core dumped)
test-execute.sh: test case 12 failed
Segmentation fault (core dumped)
test-execute.sh: test case 13 failed
Segmentation fault (core dumped)
test-execute.sh: test case 14 failed
Segmentation fault (core dumped)
test-execute.sh: test case 15 failed
Segmentation fault (core dumped)
test-execute.sh: test case 16 failed
Segmentation fault (core dumped)
test-execute.sh: test case 17 failed
Segmentation fault (core dumped)
test-execute.sh: test case 18 failed
Segmentation fault (core dumped)
test-execute.sh: test case 19 failed
Segmentation fault (core dumped)
test-execute.sh: test case 20 failed
Segmentation fault (core dumped)
test-execute.sh: test case 21 failed
FAIL test-execute.sh (exit status: 1)

FAIL: test-execute-script
=========================

Segmentation fault (core dumped)
FAIL test-execute-script.exe (exit status: 139)

FAIL: test-file-has-acl.sh
==========================

setfacl: Invalid argument
file_has_acl("tmpfile0") returned yes, expected no
FAIL test-file-has-acl.sh (exit status: 1)

FAIL: test-file-has-acl-1.sh
============================

setfacl: Invalid argument
file_has_acl("tmpfile0") returned yes, expected no
FAIL test-file-has-acl-1.sh (exit status: 1)

FAIL: test-file-has-acl-2.sh
============================

setfacl: Invalid argument
file_has_acl("tmpfile0") returned yes, expected no
FAIL test-file-has-acl-2.sh (exit status: 1)

SKIP: test-fprintf-posix2.sh
============================

Skipping test: getrlimit and setrlimit don't work
SKIP test-fprintf-posix2.sh (exit status: 77)

FAIL: test-fstrcmp
==================

Segmentation fault (core dumped)
FAIL test-fstrcmp.exe (exit status: 139)

FAIL: test-getumask
===================

Segmentation fault (core dumped)
FAIL test-getumask.exe (exit status: 139)

FAIL: test-ilogbl
=================

$HOME/src/cygwin/bison/dummy-0-0.x86_64/src/dummy-0/gltests/test-ilogb.h:68: assertion 'ILOGB (NAN) == FP_ILOGBNAN' failed
Aborted (core dumped)
FAIL test-ilogbl.exe (exit status: 134)

FAIL: test-immutable.sh
=======================

$HOME/src/cygwin/bison/dummy-0-0.x86_64/src/dummy-0/build-aux/test-driver: 107: $HOME/src/cygwin/bison/dummy-0-0.x86_64/src/dummy-0/gltests/test-immutable.sh: Permission denied
FAIL test-immutable.sh (exit status: 126)

FAIL: test-localename
=====================

Segmentation fault (core dumped)
FAIL test-localename.exe (exit status: 139)

FAIL: test-rwlock1
==================

Segmentation fault (core dumped)
FAIL test-rwlock1.exe (exit status: 139)

FAIL: test-once1
================

Segmentation fault (core dumped)
FAIL test-once1.exe (exit status: 139)

FAIL: test-once2
================

Segmentation fault (core dumped)
FAIL test-once2.exe (exit status: 139)

FAIL: test-mtx
==============

Starting test_mtx_plain ... OK
Starting test_mtx_recursive ... OK
Starting test_once ...Segmentation fault (core dumped)
FAIL test-mtx.exe (exit status: 139)

FAIL: test-passfd
=================

recvfd: Permission denied
FAIL test-passfd.exe (exit status: 16)

FAIL: test-pipe-filter-gi1.sh
=============================

Segmentation fault (core dumped)
FAIL test-pipe-filter-gi1.sh (exit status: 1)

FAIL: test-pipe-filter-gi2.sh
=============================

Segmentation fault (core dumped)
FAIL test-pipe-filter-gi2.sh (exit status: 1)

FAIL: test-pipe-filter-ii1.sh
=============================

Segmentation fault (core dumped)
FAIL test-pipe-filter-ii1.sh (exit status: 1)

FAIL: test-pipe-filter-ii2.sh
=============================

Segmentation fault (core dumped)
FAIL test-pipe-filter-ii2.sh (exit status: 1)

FAIL: test-raise
================

$HOME/src/cygwin/bison/dummy-0-0.x86_64/src/dummy-0/gltests/test-raise.c:42: assertion 'raise (-1) != 0' failed
Aborted (core dumped)
FAIL test-raise.exe (exit status: 134)

FAIL: test-readlinkat
=====================

$HOME/src/cygwin/bison/dummy-0-0.x86_64/src/dummy-0/gltests/test-readlink.h:41: assertion 'errno == ENOENT || errno == EINVAL' failed
Aborted (core dumped)
FAIL test-readlinkat.exe (exit status: 134)

FAIL: test-regex-quote
======================

Segmentation fault (core dumped)
FAIL test-regex-quote.exe (exit status: 139)

FAIL: test-regex
================

Segmentation fault (core dumped)
FAIL test-regex.exe (exit status: 139)

FAIL: test-setlocale_null
=========================

Segmentation fault (core dumped)
FAIL test-setlocale_null.exe (exit status: 139)

FAIL: test-setlocale1.sh
========================

Segmentation fault (core dumped)
FAIL test-setlocale1.sh (exit status: 1)

FAIL: test-simple-atomic
========================

Segmentation fault (core dumped)
FAIL test-simple-atomic.exe (exit status: 139)

FAIL: test-spawn-pipe.sh
========================

Segmentation fault (core dumped)
test-spawn-pipe.sh: iteration 0 failed
Segmentation fault (core dumped)
test-spawn-pipe.sh: iteration 1 failed
Segmentation fault (core dumped)
test-spawn-pipe.sh: iteration 2 failed
Segmentation fault (core dumped)
test-spawn-pipe.sh: iteration 3 failed
Segmentation fault (core dumped)
test-spawn-pipe.sh: iteration 4 failed
Segmentation fault (core dumped)
test-spawn-pipe.sh: iteration 5 failed
Segmentation fault (core dumped)
test-spawn-pipe.sh: iteration 6 failed
Segmentation fault (core dumped)
test-spawn-pipe.sh: iteration 7 failed
FAIL test-spawn-pipe.sh (exit status: 1)

FAIL: test-spawn-pipe-script
============================

Segmentation fault (core dumped)
FAIL test-spawn-pipe-script.exe (exit status: 139)

FAIL: test-ssfmalloc
====================

Segmentation fault (core dumped)
FAIL test-ssfmalloc.exe (exit status: 139)

FAIL: test-supersede
====================

Segmentation fault (core dumped)
FAIL test-supersede.exe (exit status: 139)

FAIL: test-term-style-control-hello
===================================

Segmentation fault (core dumped)
FAIL test-term-style-control-hello.exe (exit status: 139)

FAIL: test-thread_self
======================

Segmentation fault (core dumped)
FAIL test-thread_self.exe (exit status: 139)

FAIL: test-thread_create
========================

Segmentation fault (core dumped)
FAIL test-thread_create.exe (exit status: 139)

FAIL: test-tls
==============

Starting test_tls ...Segmentation fault (core dumped)
FAIL test-tls.exe (exit status: 139)

===============================================================================

Among these, the most intriguing one is
  FAIL: test-thread_self
because that test is so small.

Find attached a smaller testdir, created through
  ./gnulib-tool --create-testdir --dir=../testdir-thread --single-configure thread

Does it work (with '../configure -C && make && make check', in a subdirectory)?

Can you also try to build it through

  gl_cv_have_weak=no ../configure -C && make && make check

in a different subdirectory?

Please send the config.log, config.cache, config.status, and
gltests/test-suite.log for each run.

Bruno