1# visibility.m4 serial 3 (gettext-0.18)
2dnl Copyright (C) 2005, 2008-2010 Free Software Foundation, Inc.
3dnl This file is free software; the Free Software Foundation
4dnl gives unlimited permission to copy and/or distribute it,
5dnl with or without modifications, as long as this notice is preserved.
6
7dnl From Bruno Haible.
8
9dnl Tests whether the compiler supports the command-line option
10dnl -fvisibility=hidden and the function and variable attributes
11dnl __attribute__((__visibility__("hidden"))) and
12dnl __attribute__((__visibility__("default"))).
13dnl Does *not* test for __visibility__("protected") - which has tricky
14dnl semantics (see the 'vismain' test in glibc) and does not exist e.g. on
15dnl MacOS X.
16dnl Does *not* test for __visibility__("internal") - which has processor
17dnl dependent semantics.
18dnl Does *not* test for #pragma GCC visibility push(hidden) - which is
19dnl "really only recommended for legacy code".
20dnl Set the variable CFLAG_VISIBILITY.
21dnl Defines and sets the variable HAVE_VISIBILITY.
22
23AC_DEFUN([gl_VISIBILITY],
24[
25  AC_REQUIRE([AC_PROG_CC])
26  CFLAG_VISIBILITY=
27  HAVE_VISIBILITY=0
28  if test -n "$GCC"; then
29    dnl First, check whether -Werror can be added to the command line, or
30    dnl whether it leads to an error because of some other option that the
31    dnl user has put into $CC $CFLAGS $CPPFLAGS.
32    AC_MSG_CHECKING([whether the -Werror option is usable])
33    AC_CACHE_VAL([gl_cv_cc_vis_werror], [
34      gl_save_CFLAGS="$CFLAGS"
35      CFLAGS="$CFLAGS -Werror"
36      AC_TRY_COMPILE([], [],
37        [gl_cv_cc_vis_werror=yes],
38        [gl_cv_cc_vis_werror=no])
39      CFLAGS="$gl_save_CFLAGS"])
40    AC_MSG_RESULT([$gl_cv_cc_vis_werror])
41    dnl Now check whether visibility declarations are supported.
42    AC_MSG_CHECKING([for simple visibility declarations])
43    AC_CACHE_VAL([gl_cv_cc_visibility], [
44      gl_save_CFLAGS="$CFLAGS"
45      CFLAGS="$CFLAGS -fvisibility=hidden"
46      dnl We use the option -Werror and a function dummyfunc, because on some
47      dnl platforms (Cygwin 1.7) the use of -fvisibility triggers a warning
48      dnl "visibility attribute not supported in this configuration; ignored"
49      dnl at the first function definition in every compilation unit, and we
50      dnl don't want to use the option in this case.
51      if test $gl_cv_cc_vis_werror = yes; then
52        CFLAGS="$CFLAGS -Werror"
53      fi
54      AC_TRY_COMPILE(
55        [extern __attribute__((__visibility__("hidden"))) int hiddenvar;
56         extern __attribute__((__visibility__("default"))) int exportedvar;
57         extern __attribute__((__visibility__("hidden"))) int hiddenfunc (void);
58         extern __attribute__((__visibility__("default"))) int exportedfunc (void);
59         void dummyfunc (void) {}],
60        [],
61        [gl_cv_cc_visibility=yes],
62        [gl_cv_cc_visibility=no])
63      CFLAGS="$gl_save_CFLAGS"])
64    AC_MSG_RESULT([$gl_cv_cc_visibility])
65    if test $gl_cv_cc_visibility = yes; then
66      CFLAG_VISIBILITY="-fvisibility=hidden"
67      HAVE_VISIBILITY=1
68    fi
69  fi
70  AC_SUBST([CFLAG_VISIBILITY])
71  AC_SUBST([HAVE_VISIBILITY])
72  AC_DEFINE_UNQUOTED([HAVE_VISIBILITY], [$HAVE_VISIBILITY],
73    [Define to 1 or 0, depending whether the compiler supports simple visibility declarations.])
74])
75