# visibility.m4 serial 3 (gettext-0.18)

dnl Copyright (C) 2005, 2008-2010 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_TRY_COMPILE([], [],

        [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_TRY_COMPILE(

        [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.])

])