gnulib m4/threadlib.m4 bug crashing package tests

Ken Brown
Thu Nov 25 16:26:51 GMT 2021

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.

Thanks, Brian.

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.


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