gnulib m4/threadlib.m4 bug crashing package tests

Brian Inglis
Fri Nov 26 04:48:16 GMT 2021

On 2021-11-25 11:25, Yaakov Selkowitz via Cygwin-apps wrote:
> On Thu, 2021-11-25 at 11:26 -0500, Ken Brown via Cygwin-apps wrote:
>> On 9/29/2021 7:46 PM, Brian Inglis wrote:
>>> 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
>>> [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.

>> I'm writing to reinforce this warning. I just spent 2 days trying 
>> to debug mysterious texinfo crashes that were caused by this bug. I
>> could have saved a lot of time if I had remembered your email and
>> had checked the gnulib version being used by texinfo.
>> For anyone else who bumps into this, gdb and strace are of no use 
>> in debugging this crash. I finally thought to look at the
>> stackdump file, and the second address from the top was in a gnulib
>> file. That was the key clue.

> Add gl_cv_have_weak=no to cygconf?

or gl_cv_have_weak="guessing no" or
patch [gl_cv_have_weak="guessing no"] above

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

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