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5df4cba6 | 1 | # visibility.m4 serial 6 |
9c9d63b1 | 2 | dnl Copyright (C) 2005, 2008, 2010-2021 Free Software Foundation, Inc. |
5df4cba6 SM |
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 Mac OS 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 | 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 $CPPFLAGS. | |
32 | AC_CACHE_CHECK([whether the -Werror option is usable], | |
33 | [gl_cv_cc_vis_werror], | |
34 | [gl_save_CFLAGS="$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 | ]) | |
42 | dnl Now check whether visibility declarations are supported. | |
43 | AC_CACHE_CHECK([for simple visibility declarations], | |
44 | [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 | ]) | |
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 | ]) |