Merge from trunk.
[m6w6/libmemcached] / m4 / visibility.m4
1 # visibility.m4 serial 2 (gettext-0.18)
2 dnl Copyright (C) 2005, 2008 Free Software Foundation, Inc.
3 dnl This file is free software; the Free Software Foundation
4 dnl gives unlimited permission to copy and/or distribute it,
5 dnl with or without modifications, as long as this notice is preserved.
6
7 dnl From Bruno Haible.
8
9 dnl Tests whether the compiler supports the command-line option
10 dnl -fvisibility=hidden and the function and variable attributes
11 dnl __attribute__((__visibility__("hidden"))) and
12 dnl __attribute__((__visibility__("default"))).
13 dnl Does *not* test for __visibility__("protected") - which has tricky
14 dnl semantics (see the 'vismain' test in glibc) and does not exist e.g. on
15 dnl MacOS X.
16 dnl Does *not* test for __visibility__("internal") - which has processor
17 dnl dependent semantics.
18 dnl Does *not* test for #pragma GCC visibility push(hidden) - which is
19 dnl "really only recommended for legacy code".
20 dnl Set the variable CFLAG_VISIBILITY.
21 dnl Defines and sets the variable HAVE_VISIBILITY.
22
23 AC_DEFUN([gl_VISIBILITY],
24 [
25 AC_REQUIRE([AC_PROG_CC])
26 CFLAG_VISIBILITY=
27 HAVE_VISIBILITY=0
28 if test -n "$GCC"; then
29 AC_MSG_CHECKING([for simple visibility declarations])
30 AC_CACHE_VAL([gl_cv_cc_visibility], [
31 gl_save_CFLAGS="$CFLAGS"
32 CFLAGS="$CFLAGS -fvisibility=hidden"
33 AC_TRY_COMPILE(
34 [extern __attribute__((__visibility__("hidden"))) int hiddenvar;
35 extern __attribute__((__visibility__("default"))) int exportedvar;
36 extern __attribute__((__visibility__("hidden"))) int hiddenfunc (void);
37 extern __attribute__((__visibility__("default"))) int exportedfunc (void);],
38 [],
39 [gl_cv_cc_visibility=yes],
40 [gl_cv_cc_visibility=no])
41 CFLAGS="$gl_save_CFLAGS"])
42 AC_MSG_RESULT([$gl_cv_cc_visibility])
43 if test $gl_cv_cc_visibility = yes; then
44 CFLAG_VISIBILITY="-fvisibility=hidden"
45 HAVE_VISIBILITY=1
46 fi
47 fi
48 AC_SUBST([CFLAG_VISIBILITY])
49 AC_SUBST([HAVE_VISIBILITY])
50 AC_DEFINE_UNQUOTED([HAVE_VISIBILITY], [$HAVE_VISIBILITY],
51 [Define to 1 or 0, depending whether the compiler supports simple visibility declarations.])
52 ])