Re: test results on Cygwin

[Bruno Haible]

> 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.

This works around it:


2010-04-05  Bruno Haible  <address@hidden>

        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 $gl_cv_have_weak = maybe; then
+         dnl Second, test whether it actually works. On Cygwin 1.7.2, with
+         dnl gcc 4.3, symbols declared weak always evaluate to the address 0.
+         AC_TRY_RUN([
+#include <stdio.h>
+#pragma weak fputs
+int main ()
+{
+  return (fputs == NULL);
+}], [gl_cv_have_weak=yes], [gl_cv_have_weak=no],
+           [dnl When cross-compiling, assume that only ELF platforms support
+            dnl weak symbols.
+            AC_EGREP_CPP([Extensible Linking Format],
+              [#ifdef __ELF__
+               Extensible Linking Format
+               #endif
+              ],
+              [gl_cv_have_weak="guessing yes"],
+              [gl_cv_have_weak="guessing no"])
+           ])
+       fi
+      ])
     if test "$gl_use_threads" = yes || test "$gl_use_threads" = posix; then
       # On OSF/1, the compiler needs the flag -pthread or -D_REENTRANT so that
       # it groks <pthread.h>. It's added above, in gl_THREADLIB_EARLY_BODY.
@@ -165,7 +188,7 @@
           AC_DEFINE([USE_POSIX_THREADS], [1],
             [Define if the POSIX multithreading library can be used.])
           if test -n "$LIBMULTITHREAD" || test -n "$LTLIBMULTITHREAD"; then
-            if test $gl_have_weak = yes; then
+            if case "$gl_cv_have_weak" in *yes) true;; *) false;; esac; then
               AC_DEFINE([USE_POSIX_THREADS_WEAK], [1],
                 [Define if references to the POSIX multithreading library 
should be made weak.])
               LIBTHREAD=
@@ -193,7 +216,7 @@
           LTLIBMULTITHREAD="$LTLIBTHREAD"
           AC_DEFINE([USE_SOLARIS_THREADS], [1],
             [Define if the old Solaris multithreading library can be used.])
-          if test $gl_have_weak = yes; then
+          if case "$gl_cv_have_weak" in *yes) true;; *) false;; esac; then
             AC_DEFINE([USE_SOLARIS_THREADS_WEAK], [1],
               [Define if references to the old Solaris multithreading library 
should be made weak.])
             LIBTHREAD=
@@ -219,7 +242,7 @@
         AC_DEFINE([USE_PTH_THREADS], [1],
           [Define if the GNU Pth multithreading library can be used.])
         if test -n "$LIBMULTITHREAD" || test -n "$LTLIBMULTITHREAD"; then
-          if test $gl_have_weak = yes; then
+          if case "$gl_cv_have_weak" in *yes) true;; *) false;; esac; then
             AC_DEFINE([USE_PTH_THREADS_WEAK], [1],
               [Define if references to the GNU Pth multithreading library 
should be made weak.])
             LIBTHREAD=