git.m6w6.name Git - m6w6/libmemcached/blob - m4/visibility.m4

   1 # visibility.m4 serial 3 (gettext-0.18)
   2 dnl Copyright (C) 2005, 2008-2010 Free Software Foundation, Inc.
   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
  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="$CFLAGS -Werror"
  36       AC_TRY_COMPILE([], [],
  37         [gl_cv_cc_vis_werror=yes],
  38         [gl_cv_cc_vis_werror=no])
  39       CFLAGS="$gl_save_CFLAGS"])
  40     AC_MSG_RESULT([$gl_cv_cc_vis_werror])
  41     dnl Now check whether visibility declarations are supported.
  42     AC_MSG_CHECKING([for simple visibility declarations])
  43     AC_CACHE_VAL([gl_cv_cc_visibility], [
  44       gl_save_CFLAGS="$CFLAGS"
  45       CFLAGS="$CFLAGS -fvisibility=hidden"
  46       dnl We use the option -Werror and a function dummyfunc, because on some
  47       dnl platforms (Cygwin 1.7) the use of -fvisibility triggers a warning
  48       dnl "visibility attribute not supported in this configuration; ignored"
  49       dnl at the first function definition in every compilation unit, and we
  50       dnl don't want to use the option in this case.
  51       if test $gl_cv_cc_vis_werror = yes; then
  52         CFLAGS="$CFLAGS -Werror"
  53       fi
  54       AC_TRY_COMPILE(
  55         [extern __attribute__((__visibility__("hidden"))) int hiddenvar;
  56          extern __attribute__((__visibility__("default"))) int exportedvar;
  57          extern __attribute__((__visibility__("hidden"))) int hiddenfunc (void);
  58          extern __attribute__((__visibility__("default"))) int exportedfunc (void);
  59          void dummyfunc (void) {}],
  60         [],
  61         [gl_cv_cc_visibility=yes],
  62         [gl_cv_cc_visibility=no])
  63       CFLAGS="$gl_save_CFLAGS"])
  64     AC_MSG_RESULT([$gl_cv_cc_visibility])
  65     if test $gl_cv_cc_visibility = yes; then
  66       CFLAG_VISIBILITY="-fvisibility=hidden"
  67       HAVE_VISIBILITY=1
  68     fi
  69   fi
  70   AC_SUBST([CFLAG_VISIBILITY])
  71   AC_SUBST([HAVE_VISIBILITY])
  72   AC_DEFINE_UNQUOTED([HAVE_VISIBILITY], [$HAVE_VISIBILITY],
  73     [Define to 1 or 0, depending whether the compiler supports simple visibility declarations.])
  74 ])