There is a gnulib bug in threadlib.m4 from at least serial 29 to serial
31 that incorrectly configures Cygwin support of weak references.

This leads to SIGSEGV stack smashing crashes with no backtrace
@ 0x00000000100000000 or 0x0000000500000000 etc. normally during tests.

Akim Demaille on bug-bison referred the issue to bug-gnulib where
Bruno Haible diagnosed and patched the problem to appear in
m4/threadlib.m4 serial 32:

* m4/threadlib.m4 (gl_WEAK_SYMBOLS): Force a "guessing no" result on Cygwin
https://lists.gnu.org/archive/html/bug-gnulib/2021-09/msg00068.html
[gl_cv_have_weak="guessing no"]

The patch has now been applied to bison, wget, and wget2, and I have
attached my patches for the copies in those packages, in case anyone
else has this issue in their (mainly GNU) packages which may incorporate 
by inclusion recently updated gnulib m4 macros used in autotools builds.

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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