1# visibility.m4 serial 4 (gettext-0.18.2)
2dnl Copyright (C) 2005, 2008, 2010-2011 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="$CFLAGS -Werror"
36      AC_COMPILE_IFELSE(
37        [AC_LANG_PROGRAM([[]], [[]])],
38        [gl_cv_cc_vis_werror=yes],
39        [gl_cv_cc_vis_werror=no])
40      CFLAGS="$gl_save_CFLAGS"])
41    AC_MSG_RESULT([$gl_cv_cc_vis_werror])
42    dnl Now check whether visibility declarations are supported.
43    AC_MSG_CHECKING([for simple visibility declarations])
44    AC_CACHE_VAL([gl_cv_cc_visibility], [
45      gl_save_CFLAGS="$CFLAGS"
46      CFLAGS="$CFLAGS -fvisibility=hidden"
47      dnl We use the option -Werror and a function dummyfunc, because on some
48      dnl platforms (Cygwin 1.7) the use of -fvisibility triggers a warning
49      dnl "visibility attribute not supported in this configuration; ignored"
50      dnl at the first function definition in every compilation unit, and we
51      dnl don't want to use the option in this case.
52      if test $gl_cv_cc_vis_werror = yes; then
53        CFLAGS="$CFLAGS -Werror"
54      fi
55      AC_COMPILE_IFELSE(
56        [AC_LANG_PROGRAM(
57           [[extern __attribute__((__visibility__("hidden"))) int hiddenvar;
58             extern __attribute__((__visibility__("default"))) int exportedvar;
59             extern __attribute__((__visibility__("hidden"))) int hiddenfunc (void);
60             extern __attribute__((__visibility__("default"))) int exportedfunc (void);
61             void dummyfunc (void) {}
62           ]],
63           [[]])],
64        [gl_cv_cc_visibility=yes],
65        [gl_cv_cc_visibility=no])
66      CFLAGS="$gl_save_CFLAGS"])
67    AC_MSG_RESULT([$gl_cv_cc_visibility])
68    if test $gl_cv_cc_visibility = yes; then
69      CFLAG_VISIBILITY="-fvisibility=hidden"
70      HAVE_VISIBILITY=1
71    fi
72  fi
73  AC_SUBST([CFLAG_VISIBILITY])
74  AC_SUBST([HAVE_VISIBILITY])
75  AC_DEFINE_UNQUOTED([HAVE_VISIBILITY], [$HAVE_VISIBILITY],
76    [Define to 1 or 0, depending whether the compiler supports simple visibility declarations.])
77])
78