[moving to the cygwin list from bug-gnulib] On 04/05/2010 03:48 PM, Bruno Haible wrote: >> Failures on Cygwin 1.7.2 >> ------------------------ >> >> Starting test_cond .../bin/sh: line 5: 4200 Aborted >> FAIL: test-cond.exe >> >> Starting test_lock .../bin/sh: line 5: 2296 Aborted >> FAIL: test-lock.exe >> >> Starting test_tls .../bin/sh: line 5: 2656 Aborted >> FAIL: test-tls.exe > > These were all due to the fact that gcc 4.3.x on Cygwin 1.7.2 > accepts "#pragma weak foo", but the symbol foo then evaluates > to the NULL address, even if foo is defined in libc.
Dave, are weak symbols something that should work on cygwin with new
enough binutils/gcc? Or is this an indicator of a gcc bug, for silently
accepting #pragma weak foo that it can't support?
>
> This works around it:
>
>
> 2010-04-05 Bruno Haible <br...@clisp.org>
>
> Make the multithread modules work on Cygwin 1.7.2.
> * m4/threadlib.m4 (gl_THREADLIB_BODY): Improve the test whether
> imported symbols can be declared weak, so that it returns "no" on
> Cygwin 1.7.2.
>
> --- m4/threadlib.m4.orig Mon Apr 5 23:43:16 2010
> +++ m4/threadlib.m4 Mon Apr 5 23:39:40 2010
> @@ -1,4 +1,4 @@
> -# threadlib.m4 serial 4 (gettext-0.18)
> +# threadlib.m4 serial 5 (gettext-0.18)
> dnl Copyright (C) 2005-2010 Free Software Foundation, Inc.
> dnl This file is free software; the Free Software Foundation
> dnl gives unlimited permission to copy and/or distribute it,
> @@ -107,11 +107,34 @@
> LTLIBMULTITHREAD=
> if test "$gl_use_threads" != no; then
> dnl Check whether the compiler and linker support weak declarations.
> - AC_MSG_CHECKING([whether imported symbols can be declared weak])
> - gl_have_weak=no
> - AC_TRY_LINK([extern void xyzzy ();
> -#pragma weak xyzzy], [xyzzy();], [gl_have_weak=yes])
> - AC_MSG_RESULT([$gl_have_weak])
> + AC_CACHE_CHECK([whether imported symbols can be declared weak],
> + [gl_cv_have_weak],
> + [gl_cv_have_weak=no
> + dnl First, test whether the compiler accepts it syntactically.
> + AC_TRY_LINK([extern void xyzzy ();
> +#pragma weak xyzzy], [xyzzy();], [gl_cv_have_weak=maybe])
> + if test $gl_cv_have_weak = maybe; then
> + dnl Second, test whether it actually works. On Cygwin 1.7.2, with
> + dnl gcc 4.3, symbols declared weak always evaluate to the address 0.
> + AC_TRY_RUN([
> +#include <stdio.h>
> +#pragma weak fputs
> +int main ()
> +{
> + return (fputs == NULL);
> +}], [gl_cv_have_weak=yes], [gl_cv_have_weak=no],
> + [dnl When cross-compiling, assume that only ELF platforms support
> + dnl weak symbols.
> + AC_EGREP_CPP([Extensible Linking Format],
> + [#ifdef __ELF__
> + Extensible Linking Format
> + #endif
> + ],
> + [gl_cv_have_weak="guessing yes"],
> + [gl_cv_have_weak="guessing no"])
> + ])
> + fi
> + ])
--
Eric Blake ebl...@redhat.com +1-801-349-2682
Libvirt virtualization library http://libvirt.org
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