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

   1 # visibility.m4 serial 2 (gettext-0.18)
   2 dnl Copyright (C) 2005, 2008 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 "$GCC"; then
  29     AC_MSG_CHECKING([for simple visibility declarations])
  30     AC_CACHE_VAL([gl_cv_cc_visibility], [
  31       gl_save_CFLAGS="$CFLAGS"
  32       CFLAGS="$CFLAGS -fvisibility=hidden"
  33       AC_TRY_COMPILE(
  34         [extern __attribute__((__visibility__("hidden"))) int hiddenvar;
  35          extern __attribute__((__visibility__("default"))) int exportedvar;
  36          extern __attribute__((__visibility__("hidden"))) int hiddenfunc (void);
  37          extern __attribute__((__visibility__("default"))) int exportedfunc (void);],
  38         [],
  39         [gl_cv_cc_visibility=yes],
  40         [gl_cv_cc_visibility=no])
  41       CFLAGS="$gl_save_CFLAGS"])
  42     AC_MSG_RESULT([$gl_cv_cc_visibility])
  43     if test $gl_cv_cc_visibility = yes; then
  44       CFLAG_VISIBILITY="-fvisibility=hidden"
  45       HAVE_VISIBILITY=1
  46     fi
  47   fi
  48   AC_SUBST([CFLAG_VISIBILITY])
  49   AC_SUBST([HAVE_VISIBILITY])
  50   AC_DEFINE_UNQUOTED([HAVE_VISIBILITY], [$HAVE_VISIBILITY],
  51     [Define to 1 or 0, depending whether the compiler supports simple visibility declarations.])
  52 ])