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Annotation of embedaddon/libiconv/srcm4/visibility.m4, revision 1.1.1.2

1.1.1.2 ! misho       1: # visibility.m4 serial 4 (gettext-0.18.2)
        !             2: dnl Copyright (C) 2005, 2008, 2010-2011 Free Software Foundation, Inc.
1.1       misho       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 MacOS 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
1.1.1.2 ! misho      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([$gl_cv_cc_vis_werror])
        !            42:     dnl Now check whether visibility declarations are supported.
1.1       misho      43:     AC_MSG_CHECKING([for simple visibility declarations])
                     44:     AC_CACHE_VAL([gl_cv_cc_visibility], [
                     45:       gl_save_CFLAGS="$CFLAGS"
                     46:       CFLAGS="$CFLAGS -fvisibility=hidden"
1.1.1.2 ! misho      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:            [[]])],
1.1       misho      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: ])