3 dnl Copyright (C) 2005, 2008, 2010-2024 Free Software Foundation, Inc.
4 dnl This file is free software; the Free Software Foundation
5 dnl gives unlimited permission to copy and/or distribute it,
6 dnl with or without modifications, as long as this notice is preserved.
10 dnl Tests whether the compiler supports the command-line option
11 dnl -fvisibility=hidden and the function and variable attributes
12 dnl __attribute__((__visibility__("hidden"))) and
13 dnl __attribute__((__visibility__("default"))).
14 dnl Does *not* test for __visibility__("protected") - which has tricky
15 dnl semantics (see the 'vismain' test in glibc) and does not exist e.g. on
17 dnl Does *not* test for __visibility__("internal") - which has processor
18 dnl dependent semantics.
19 dnl Does *not* test for #pragma GCC visibility push(hidden) - which is
20 dnl "really only recommended for legacy code".
21 dnl Set the variable CFLAG_VISIBILITY.
22 dnl Defines and sets the variable HAVE_VISIBILITY.
24 AC_DEFUN([gl_VISIBILITY],
26 AC_REQUIRE([AC_PROG_CC])
29 if test -n "$GCC"; then
30 dnl First, check whether -Werror can be added to the command line, or
31 dnl whether it leads to an error because of some other option that the
32 dnl user has put into $CC $CFLAGS $CPPFLAGS.
33 AC_CACHE_CHECK([whether the -Werror option is usable],
34 [gl_cv_cc_vis_werror],
35 [gl_saved_CFLAGS="$CFLAGS"
36 CFLAGS="$CFLAGS -Werror"
38 [AC_LANG_PROGRAM([[]], [[]])],
39 [gl_cv_cc_vis_werror=yes],
40 [gl_cv_cc_vis_werror=no])
41 CFLAGS="$gl_saved_CFLAGS"
43 dnl Now check whether visibility declarations are supported.
44 AC_CACHE_CHECK([for simple visibility declarations],
45 [gl_cv_cc_visibility],
46 [gl_saved_CFLAGS="$CFLAGS"
47 CFLAGS="$CFLAGS -fvisibility=hidden"
48 dnl We use the option -Werror and a function dummyfunc, because on some
49 dnl platforms (Cygwin 1.7) the use of -fvisibility triggers a warning
50 dnl "visibility attribute not supported in this configuration; ignored"
51 dnl at the first function definition in every compilation unit, and we
52 dnl don't want to use the option in this case.
53 if test $gl_cv_cc_vis_werror = yes; then
54 CFLAGS="$CFLAGS -Werror"
58 [[extern __attribute__((__visibility__("hidden"))) int hiddenvar;
59 extern __attribute__((__visibility__("default"))) int exportedvar;
60 extern __attribute__((__visibility__("hidden"))) int hiddenfunc (void);
61 extern __attribute__((__visibility__("default"))) int exportedfunc (void);
62 void dummyfunc (void);
65 int hiddenfunc (void) { return 51; }
66 int exportedfunc (void) { return 1225736919; }
67 void dummyfunc (void) {}
70 [gl_cv_cc_visibility=yes],
71 [gl_cv_cc_visibility=no])
72 CFLAGS="$gl_saved_CFLAGS"
74 if test $gl_cv_cc_visibility = yes; then
75 CFLAG_VISIBILITY="-fvisibility=hidden"
79 AC_SUBST([CFLAG_VISIBILITY])
80 AC_SUBST([HAVE_VISIBILITY])
81 AC_DEFINE_UNQUOTED([HAVE_VISIBILITY], [$HAVE_VISIBILITY],
82 [Define to 1 or 0, depending whether the compiler supports simple visibility declarations.])