Re: bison segv under Cygwin 64 at fatal-signal.c:318

[Bruno Haible]

Brian Inglis wrote:
> > 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.
> 
> Done and attached

Thanks! Indeed, gl_cv_have_weak=no appears to make the essential difference.
Therefore, I'm applying this fix.


2021-09-17  Bruno Haible  <bruno@clisp.org>

        threadlib: Avoid crashes in thread-related functions on Cygwin 3.2.0.
        Reported by Brian Inglis via Akim Demaille in
        <https://lists.gnu.org/archive/html/bug-gnulib/2021-09/msg00063.html>.
        * m4/threadlib.m4 (gl_WEAK_SYMBOLS): Force a "guessing no" result on
        Cygwin.

diff -w --git a/m4/threadlib.m4 b/m4/threadlib.m4
index 37b797c18..6b43bbdfa 100644
--- a/m4/threadlib.m4
+++ b/m4/threadlib.m4
@@ -1,4 +1,4 @@
-# threadlib.m4 serial 31
+# threadlib.m4 serial 32
 dnl Copyright (C) 2005-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -84,7 +84,15 @@ AC_DEFUN([gl_WEAK_SYMBOLS],
   AC_REQUIRE([AC_CANONICAL_HOST])
   AC_CACHE_CHECK([whether imported symbols can be declared weak],
     [gl_cv_have_weak],
-    [gl_cv_have_weak=no
+    [case "$host_os" in
+       cygwin*)
+         dnl On Cygwin 3.2.0 with gcc 10.2, the test below would succeed, but
+         dnl programs that use pthread_in_use() with weak symbol references
+         dnl crash miserably at runtime.
+         gl_cv_have_weak="guessing no"
+         ;;
+       *)
+         gl_cv_have_weak=no
          dnl First, test whether the compiler accepts it syntactically.
          AC_LINK_IFELSE(
            [AC_LANG_PROGRAM(
@@ -116,6 +124,8 @@ int main ()
                 [gl_cv_have_weak="guessing no"])
              ])
          fi
+         ;;
+     esac
      dnl But when linking statically, weak symbols don't work.
      case " $LDFLAGS " in
        *" -static "*) gl_cv_have_weak=no ;;