maint: update copyright

[gnulib.git] / m4 / visibility.m4

diff --git a/m4/visibility.m4 b/m4/visibility.m4
index 35a6dc0..552e397 100644 (file)
--- a/m4/visibility.m4
+++ b/m4/visibility.m4
@@ -1,5 +1,5 @@
-# visibility.m4 serial 2 (gettext-0.18)
-dnl Copyright (C) 2005, 2008, 2009, 2010 Free Software Foundation, Inc.
+# visibility.m4 serial 5 (gettext-0.18.2)
+dnl Copyright (C) 2005, 2008, 2010-2014 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -12,7 +12,7 @@ dnl __attribute__((__visibility__("hidden"))) and
 dnl __attribute__((__visibility__("default"))).
 dnl Does *not* test for __visibility__("protected") - which has tricky
 dnl semantics (see the 'vismain' test in glibc) and does not exist e.g. on
-dnl MacOS X.
+dnl Mac OS X.
 dnl Does *not* test for __visibility__("internal") - which has processor
 dnl dependent semantics.
 dnl Does *not* test for #pragma GCC visibility push(hidden) - which is
@@ -26,16 +26,41 @@ AC_DEFUN([gl_VISIBILITY],
   CFLAG_VISIBILITY=
   HAVE_VISIBILITY=0
   if test -n "$GCC"; then
+    dnl First, check whether -Werror can be added to the command line, or
+    dnl whether it leads to an error because of some other option that the
+    dnl user has put into $CC $CFLAGS $CPPFLAGS.
+    AC_MSG_CHECKING([whether the -Werror option is usable])
+    AC_CACHE_VAL([gl_cv_cc_vis_werror], [
+      gl_save_CFLAGS="$CFLAGS"
+      CFLAGS="$CFLAGS -Werror"
+      AC_COMPILE_IFELSE(
+        [AC_LANG_PROGRAM([[]], [[]])],
+        [gl_cv_cc_vis_werror=yes],
+        [gl_cv_cc_vis_werror=no])
+      CFLAGS="$gl_save_CFLAGS"])
+    AC_MSG_RESULT([$gl_cv_cc_vis_werror])
+    dnl Now check whether visibility declarations are supported.
     AC_MSG_CHECKING([for simple visibility declarations])
     AC_CACHE_VAL([gl_cv_cc_visibility], [
       gl_save_CFLAGS="$CFLAGS"
       CFLAGS="$CFLAGS -fvisibility=hidden"
-      AC_TRY_COMPILE(
-        [extern __attribute__((__visibility__("hidden"))) int hiddenvar;
-         extern __attribute__((__visibility__("default"))) int exportedvar;
-         extern __attribute__((__visibility__("hidden"))) int hiddenfunc (void);
-         extern __attribute__((__visibility__("default"))) int exportedfunc (void);],
-        [],
+      dnl We use the option -Werror and a function dummyfunc, because on some
+      dnl platforms (Cygwin 1.7) the use of -fvisibility triggers a warning
+      dnl "visibility attribute not supported in this configuration; ignored"
+      dnl at the first function definition in every compilation unit, and we
+      dnl don't want to use the option in this case.
+      if test $gl_cv_cc_vis_werror = yes; then
+        CFLAGS="$CFLAGS -Werror"
+      fi
+      AC_COMPILE_IFELSE(
+        [AC_LANG_PROGRAM(
+           [[extern __attribute__((__visibility__("hidden"))) int hiddenvar;
+             extern __attribute__((__visibility__("default"))) int exportedvar;
+             extern __attribute__((__visibility__("hidden"))) int hiddenfunc (void);
+             extern __attribute__((__visibility__("default"))) int exportedfunc (void);
+             void dummyfunc (void) {}
+           ]],
+           [[]])],
         [gl_cv_cc_visibility=yes],
         [gl_cv_cc_visibility=no])
       CFLAGS="$gl_save_CFLAGS"])