Edit File: visibility.m4
# visibility.m4 serial 5 (gettext-0.18.2) dnl Copyright (C) 2005, 2008, 2010-2016 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 Mac OS 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.]) ])