| # visibility.m4 serial 4 (gettext-0.18.2) |
| dnl Copyright (C) 2005, 2008, 2010-2011 Free Software Foundation, Inc. |
| dnl This file is free software; the Free Software Foundation |
| dnl gives unlimited permission to copy and/or distribute it, |
| dnl with or without modifications, as long as this notice is preserved. |
| |
| dnl From Bruno Haible. |
| |
| dnl Tests whether the compiler supports the command-line option |
| dnl -fvisibility=hidden and the function and variable attributes |
| dnl __attribute__((__visibility__("hidden"))) and |
| dnl __attribute__((__visibility__("default"))). |
| dnl Does *not* test for __visibility__("protected") - which has tricky |
| dnl semantics (see the 'vismain' test in glibc) and does not exist e.g. on |
| dnl MacOS X. |
| dnl Does *not* test for __visibility__("internal") - which has processor |
| dnl dependent semantics. |
| dnl Does *not* test for #pragma GCC visibility push(hidden) - which is |
| dnl "really only recommended for legacy code". |
| dnl Set the variable CFLAG_VISIBILITY. |
| dnl Defines and sets the variable HAVE_VISIBILITY. |
| |
| AC_DEFUN([gl_VISIBILITY], |
| [ |
| AC_REQUIRE([AC_PROG_CC]) |
| CFLAG_VISIBILITY= |
| HAVE_VISIBILITY=0 |
| if test -n "$GCC"; then |
| dnl First, check whether -Werror can be added to the command line, or |
| dnl whether it leads to an error because of some other option that the |
| dnl user has put into $CC $CFLAGS $CPPFLAGS. |
| AC_MSG_CHECKING([whether the -Werror option is usable]) |
| AC_CACHE_VAL([gl_cv_cc_vis_werror], [ |
| gl_save_CFLAGS="$CFLAGS" |
| CFLAGS="$CFLAGS -Werror" |
| AC_COMPILE_IFELSE( |
| [AC_LANG_PROGRAM([[]], [[]])], |
| [gl_cv_cc_vis_werror=yes], |
| [gl_cv_cc_vis_werror=no]) |
| CFLAGS="$gl_save_CFLAGS"]) |
| AC_MSG_RESULT([$gl_cv_cc_vis_werror]) |
| dnl Now check whether visibility declarations are supported. |
| AC_MSG_CHECKING([for simple visibility declarations]) |
| AC_CACHE_VAL([gl_cv_cc_visibility], [ |
| gl_save_CFLAGS="$CFLAGS" |
| CFLAGS="$CFLAGS -fvisibility=hidden" |
| dnl We use the option -Werror and a function dummyfunc, because on some |
| dnl platforms (Cygwin 1.7) the use of -fvisibility triggers a warning |
| dnl "visibility attribute not supported in this configuration; ignored" |
| dnl at the first function definition in every compilation unit, and we |
| dnl don't want to use the option in this case. |
| if test $gl_cv_cc_vis_werror = yes; then |
| CFLAGS="$CFLAGS -Werror" |
| fi |
| AC_COMPILE_IFELSE( |
| [AC_LANG_PROGRAM( |
| [[extern __attribute__((__visibility__("hidden"))) int hiddenvar; |
| extern __attribute__((__visibility__("default"))) int exportedvar; |
| extern __attribute__((__visibility__("hidden"))) int hiddenfunc (void); |
| extern __attribute__((__visibility__("default"))) int exportedfunc (void); |
| void dummyfunc (void) {} |
| ]], |
| [[]])], |
| [gl_cv_cc_visibility=yes], |
| [gl_cv_cc_visibility=no]) |
| CFLAGS="$gl_save_CFLAGS"]) |
| AC_MSG_RESULT([$gl_cv_cc_visibility]) |
| if test $gl_cv_cc_visibility = yes; then |
| CFLAG_VISIBILITY="-fvisibility=hidden" |
| HAVE_VISIBILITY=1 |
| fi |
| fi |
| AC_SUBST([CFLAG_VISIBILITY]) |
| AC_SUBST([HAVE_VISIBILITY]) |
| AC_DEFINE_UNQUOTED([HAVE_VISIBILITY], [$HAVE_VISIBILITY], |
| [Define to 1 or 0, depending whether the compiler supports simple visibility declarations.]) |
| ]) |