[wxWidgets.git] / acinclude.m4

dnl ---------------------------------------------------------------------------
dnl
dnl Macros for configure.in for wxWindows by Robert Roebling, Phil Blecker,
dnl Vadim Zeitlin and Ron Lee
dnl
dnl This script is under the wxWindows licence.
dnl
dnl Version: $Id$
dnl ---------------------------------------------------------------------------

dnl ===========================================================================
dnl macros to detect specialty compiler options
dnl ===========================================================================

dnl Figure out if we need to pass -ext o to compiler (MetroWerks)
AC_DEFUN([AC_WX_METROWERKS_EXTO],
[AC_CACHE_CHECK([if the _AC_LANG compiler requires -ext o], wx_cv_[]_AC_LANG_ABBREV[]_exto,
dnl First create an empty conf test
[AC_LANG_CONFTEST([AC_LANG_PROGRAM()])
dnl Now remove .o and .c.o or .cc.o
rm -f conftest.$ac_objext conftest.$ac_ext.o
dnl Now compile the test
AS_IF([AC_TRY_EVAL(ac_compile)],
dnl If the test succeeded look for conftest.c.o or conftest.cc.o
[for ac_file in `(ls conftest.* 2>/dev/null)`; do
    case $ac_file in
        conftest.$ac_ext.o)
            wx_cv_[]_AC_LANG_ABBREV[]_exto="-ext o"
            ;;
        *)
            ;;
    esac
done],
[AC_MSG_FAILURE([cannot figure out if compiler needs -ext o: cannot compile])
]) dnl AS_IF

rm -f conftest.$ac_ext.o conftest.$ac_objext conftest.$ac_ext
]) dnl AC_CACHE_CHECK

if test "x$wx_cv_[]_AC_LANG_ABBREV[]_exto" '!=' "x"; then
    if test "[]_AC_LANG_ABBREV[]" = "c"; then
        CFLAGS="$wx_cv_[]_AC_LANG_ABBREV[]_exto $CFLAGS"
    fi
    if test "[]_AC_LANG_ABBREV[]" = "cxx"; then
        CXXFLAGS="$wx_cv_[]_AC_LANG_ABBREV[]_exto $CXXFLAGS"
    fi
fi
]) dnl AC_DEFUN


dnl Based on autoconf _AC_LANG_COMPILER_GNU
AC_DEFUN([_AC_WX_LANG_COMPILER_XLC],
[AC_CACHE_CHECK([whether we are using the IBM xlC _AC_LANG compiler],
    [wx_cv_[]_AC_LANG_ABBREV[]_compiler_xlc],
    [AC_TRY_COMPILE([],[#ifndef __xlC__
       choke me
#endif
],
        [wx_compiler_xlc=yes],
        [wx_compiler_xlc=no])
    wx_cv_[]_AC_LANG_ABBREV[]_compiler_xlc=$wx_compiler_xlc
    ])
])

dnl Loosely based on autoconf AC_PROG_CC
AC_DEFUN([AC_WX_PROG_XLCC],
[AC_LANG_PUSH(C)
_AC_WX_LANG_COMPILER_XLC
XLCC=`test $wx_compiler_xlc = yes && echo yes`
AC_LANG_POP(C)
])

dnl Loosely based on autoconf AC_PROG_CXX
AC_DEFUN([AC_WX_PROG_XLCXX],
[AC_LANG_PUSH(C++)
_AC_WX_LANG_COMPILER_XLC
XLCXX=`test $wx_compiler_xlc = yes && echo yes`
AC_LANG_POP(C++)
])


dnl ===========================================================================
dnl macros to find the a file in the list of include/lib paths
dnl ===========================================================================

dnl ---------------------------------------------------------------------------
dnl call WX_PATH_FIND_INCLUDES(search path, header name), sets ac_find_includes
dnl to the full name of the file that was found or leaves it empty if not found
dnl ---------------------------------------------------------------------------
AC_DEFUN([WX_PATH_FIND_INCLUDES],
[
ac_find_includes=
for ac_dir in $1 /usr/include;
  do
    if test -f "$ac_dir/$2"; then
      ac_find_includes=$ac_dir
      break
    fi
  done
])

dnl ---------------------------------------------------------------------------
dnl call WX_PATH_FIND_LIBRARIES(search path, header name), sets ac_find_libraries
dnl to the full name of the file that was found or leaves it empty if not found
dnl ---------------------------------------------------------------------------
AC_DEFUN([WX_PATH_FIND_LIBRARIES],
[
ac_find_libraries=
for ac_dir in $1 /usr/lib;
  do
    for ac_extension in a so sl dylib; do
      if test -f "$ac_dir/lib$2.$ac_extension"; then
        ac_find_libraries=$ac_dir
        break 2
      fi
    done
  done
])

dnl ---------------------------------------------------------------------------
dnl Path to include, already defined
dnl ---------------------------------------------------------------------------
AC_DEFUN([WX_INCLUDE_PATH_EXIST],
[
  dnl never add -I/usr/include to the CPPFLAGS
  if test "x$1" = "x/usr/include"; then
    ac_path_to_include=""
  else
    echo "$2" | grep "\-I$1" > /dev/null
    result=$?
    if test $result = 0; then
      ac_path_to_include=""
    else
      ac_path_to_include=" -I$1"
    fi
  fi
])

dnl ---------------------------------------------------------------------------
dnl Path to link, already defined
dnl ---------------------------------------------------------------------------
AC_DEFUN([WX_LINK_PATH_EXIST],
[
  echo "$2" | grep "\-L$1" > /dev/null
  result=$?
  if test $result = 0; then
    ac_path_to_link=""
  else
    ac_path_to_link=" -L$1"
  fi
])

dnl ===========================================================================
dnl C++ features test
dnl ===========================================================================

dnl ---------------------------------------------------------------------------
dnl WX_CPP_NEW_HEADERS checks whether the compiler has "new" <iostream> header
dnl or only the old <iostream.h> one - it may be generally assumed that if
dnl <iostream> exists, the other "new" headers (without .h) exist too.
dnl
dnl call WX_CPP_NEW_HEADERS(actiof-if-true, action-if-false)
dnl ---------------------------------------------------------------------------

AC_DEFUN([WX_CPP_NEW_HEADERS],
[
    AC_LANG_SAVE
    AC_LANG_CPLUSPLUS

    AC_CHECK_HEADERS(iostream)

    if test "$ac_cv_header_iostream" = "yes" ; then
      ifelse([$1], , :, [$1])
    else
      ifelse([$2], , :, [$2])
    fi

    AC_LANG_RESTORE
])

dnl ---------------------------------------------------------------------------
dnl WX_CPP_BOOL checks whether the C++ compiler has a built in bool type
dnl
dnl call WX_CPP_BOOL - will define HAVE_BOOL if the compiler supports bool
dnl ---------------------------------------------------------------------------

AC_DEFUN([WX_CPP_BOOL],
[
  AC_CACHE_CHECK([if C++ compiler supports bool], wx_cv_cpp_bool,
  [
    AC_LANG_SAVE
    AC_LANG_CPLUSPLUS

    AC_TRY_COMPILE(
      [
      ],
      [
        bool b = true;

        return 0;
      ],
      [
        wx_cv_cpp_bool=yes
      ],
      [
        wx_cv_cpp_bool=no
      ]
    )

    AC_LANG_RESTORE
  ])

  if test "$wx_cv_cpp_bool" = "yes"; then
    AC_DEFINE(HAVE_BOOL)
  fi
])

dnl ---------------------------------------------------------------------------
dnl WX_CPP_EXPLICIT checks whether the C++ compiler support the explicit
dnl keyword and defines HAVE_EXPLICIT if this is the case
dnl ---------------------------------------------------------------------------

AC_DEFUN([WX_CPP_EXPLICIT],
[
  AC_CACHE_CHECK([if C++ compiler supports the explicit keyword],
                 wx_cv_explicit,
  [
    AC_LANG_SAVE
    AC_LANG_CPLUSPLUS

    dnl do the test in 2 steps: first check that the compiler knows about the
    dnl explicit keyword at all and then verify that it really honours it
    AC_TRY_COMPILE(
      [
        class Foo { public: explicit Foo(int) {} };
      ],
      [
        return 0;
      ],
      [
        AC_TRY_COMPILE(
            [
                class Foo { public: explicit Foo(int) {} };
                static void TakeFoo(const Foo& foo) { }
            ],
            [
                TakeFoo(17);
                return 0;
            ],
            wx_cv_explicit=no,
            wx_cv_explicit=yes
        )
      ],
      wx_cv_explicit=no
    )

    AC_LANG_RESTORE
  ])

  if test "$wx_cv_explicit" = "yes"; then
    AC_DEFINE(HAVE_EXPLICIT)
  fi
])

dnl ---------------------------------------------------------------------------
dnl a slightly better AC_C_BIGENDIAN macro which allows cross-compiling
dnl ---------------------------------------------------------------------------

AC_DEFUN([WX_C_BIGENDIAN],
[AC_CACHE_CHECK([whether byte ordering is bigendian], ac_cv_c_bigendian,
[ac_cv_c_bigendian=unknown
# See if sys/param.h defines the BYTE_ORDER macro.
AC_TRY_COMPILE([#include <sys/types.h>
#include <sys/param.h>], [
#if !BYTE_ORDER || !BIG_ENDIAN || !LITTLE_ENDIAN
 bogus endian macros
#endif], [# It does; now see whether it defined to BIG_ENDIAN or not.
AC_TRY_COMPILE([#include <sys/types.h>
#include <sys/param.h>], [
#if BYTE_ORDER != BIG_ENDIAN
 not big endian
#endif], ac_cv_c_bigendian=yes, ac_cv_c_bigendian=no)])
if test $ac_cv_c_bigendian = unknown; then
AC_TRY_RUN([main () {
  /* Are we little or big endian?  From Harbison&Steele.  */
  union
  {
    long l;
    char c[sizeof (long)];
  } u;
  u.l = 1;
  exit (u.c[sizeof (long) - 1] == 1);
}], [ac_cv_c_bigendian=no], [ac_cv_c_bigendian=yes], [ac_cv_c_bigendian=unknown])
fi])
if test $ac_cv_c_bigendian = unknown; then
  AC_MSG_WARN([Assuming little-endian target machine - this may be overriden by adding the line "ac_cv_c_bigendian=${ac_cv_c_bigendian='yes'}" to config.cache file])
fi
if test $ac_cv_c_bigendian = yes; then
  AC_DEFINE(WORDS_BIGENDIAN)
fi
])

dnl ---------------------------------------------------------------------------
dnl override AC_ARG_ENABLE/WITH to cache the results in .cache file
dnl ---------------------------------------------------------------------------

AC_DEFUN([WX_ARG_CACHE_INIT],
        [
          wx_arg_cache_file="configarg.cache"
          echo "loading argument cache $wx_arg_cache_file"
          rm -f ${wx_arg_cache_file}.tmp
          touch ${wx_arg_cache_file}.tmp
          touch ${wx_arg_cache_file}
        ])

AC_DEFUN([WX_ARG_CACHE_FLUSH],
        [
          echo "saving argument cache $wx_arg_cache_file"
          mv ${wx_arg_cache_file}.tmp ${wx_arg_cache_file}
        ])

dnl this macro checks for a three-valued command line --with argument:
dnl   possible arguments are 'yes', 'no', 'sys', or 'builtin'
dnl usage: WX_ARG_SYS_WITH(option, helpmessage, variable-name)
AC_DEFUN([WX_ARG_SYS_WITH],
        [
          AC_MSG_CHECKING([for --with-$1])
          no_cache=0
          AC_ARG_WITH($1, [$2],
                      [
                        if test "$withval" = yes; then
                          ac_cv_use_$1='$3=yes'
                        elif test "$withval" = no; then
                          ac_cv_use_$1='$3=no'
                        elif test "$withval" = sys; then
                          ac_cv_use_$1='$3=sys'
                        elif test "$withval" = builtin; then
                          ac_cv_use_$1='$3=builtin'
                        else
                          AC_MSG_ERROR([Invalid value for --with-$1: should be yes, no, sys, or builtin])
                        fi
                      ],
                      [
                        LINE=`grep "$3" ${wx_arg_cache_file}`
                        if test "x$LINE" != x ; then
                          eval "DEFAULT_$LINE"
                        else
                          no_cache=1
                        fi

                        ac_cv_use_$1='$3='$DEFAULT_$3
                      ])

          eval "$ac_cv_use_$1"
          if test "$no_cache" != 1; then
            echo $ac_cv_use_$1 >> ${wx_arg_cache_file}.tmp
          fi

          if test "$$3" = yes; then
            AC_MSG_RESULT(yes)
          elif test "$$3" = no; then
            AC_MSG_RESULT(no)
          elif test "$$3" = sys; then
            AC_MSG_RESULT([system version])
          elif test "$$3" = builtin; then
            AC_MSG_RESULT([builtin version])
          else
            AC_MSG_ERROR([Invalid value for --with-$1: should be yes, no, sys, or builtin])
          fi
        ])

dnl this macro checks for a command line argument and caches the result
dnl usage: WX_ARG_WITH(option, helpmessage, variable-name)
AC_DEFUN([WX_ARG_WITH],
        [
          AC_MSG_CHECKING([for --with-$1])
          no_cache=0
          AC_ARG_WITH($1, [$2],
                      [
                        if test "$withval" = yes; then
                          ac_cv_use_$1='$3=yes'
                        else
                          ac_cv_use_$1='$3=no'
                        fi
                      ],
                      [
                        LINE=`grep "$3" ${wx_arg_cache_file}`
                        if test "x$LINE" != x ; then
                          eval "DEFAULT_$LINE"
                        else
                          no_cache=1
                        fi

                        ac_cv_use_$1='$3='$DEFAULT_$3
                      ])

          eval "$ac_cv_use_$1"
          if test "$no_cache" != 1; then
            echo $ac_cv_use_$1 >> ${wx_arg_cache_file}.tmp
          fi

          if test "$$3" = yes; then
            AC_MSG_RESULT(yes)
          else
            AC_MSG_RESULT(no)
          fi
        ])

dnl like WX_ARG_WITH but uses AC_ARG_ENABLE instead of AC_ARG_WITH
dnl usage: WX_ARG_ENABLE(option, helpmessage, variable-name, enablestring)
dnl
dnl enablestring is a hack and allows to show "checking for --disable-foo"
dnl message when running configure instead of the default "checking for
dnl --enable-foo" one whih is useful for the options enabled by default
AC_DEFUN([WX_ARG_ENABLE],
        [
	  enablestring=$4
          AC_MSG_CHECKING([for --${enablestring:-enable}-$1])
          no_cache=0
          AC_ARG_ENABLE($1, [$2],
                        [
                          if test "$enableval" = yes; then
                            ac_cv_use_$1='$3=yes'
                          else
                            ac_cv_use_$1='$3=no'
                          fi
                        ],
                        [
                          LINE=`grep "$3" ${wx_arg_cache_file}`
                          if test "x$LINE" != x ; then
                            eval "DEFAULT_$LINE"
                          else
                            no_cache=1
                          fi

                          ac_cv_use_$1='$3='$DEFAULT_$3
                        ])

          eval "$ac_cv_use_$1"
          if test "$no_cache" != 1; then
            echo $ac_cv_use_$1 >> ${wx_arg_cache_file}.tmp
          fi

          if test "$$3" = yes; then
            AC_MSG_RESULT(yes)
          else
            AC_MSG_RESULT(no)
          fi
        ])


dnl ===========================================================================
dnl Linker features test
dnl ===========================================================================

dnl ---------------------------------------------------------------------------
dnl WX_VERSIONED_SYMBOLS checks whether the linker can create versioned
dnl symbols. If it can, sets LDFLAGS_VERSIONING to $CXX flags needed to use
dnl version script file named versionfile
dnl
dnl call WX_VERSIONED_SYMBOLS(versionfile)
dnl ---------------------------------------------------------------------------
AC_DEFUN([WX_VERSIONED_SYMBOLS],
[
  found_versioning=no

  dnl FIXME - doesn't work, Solaris linker doesn't accept wildcards
  dnl         in the script.
  dnl dnl Check for known non-gcc cases:
  dnl case "${host}" in
  dnl   *-*-solaris2* )
  dnl     if test "x$GCC" != "xyes" ; then
  dnl         LDFLAGS_VERSIONING="-M $1"
  dnl         found_versioning=yes
  dnl     fi
  dnl   ;;
  dnl esac
  
  dnl Generic check for GCC or GCC-like behaviour (Intel C++, GCC):
  if test $found_versioning = no ; then
      AC_CACHE_CHECK([if the linker accepts --version-script], wx_cv_version_script,
      [
        echo "VER_1 { *; };" >conftest.sym
        echo "int main() { return 0; }" >conftest.cpp
  
        if AC_TRY_COMMAND([
                $CXX -o conftest.output $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.cpp
                -Wl,--version-script,conftest.sym >/dev/null 2>conftest.stderr]) ; then
          if test -s conftest.stderr ; then
              wx_cv_version_script=no
          else
              wx_cv_version_script=yes
          fi
        else
          wx_cv_version_script=no
        fi
        rm -f conftest.output conftest.stderr conftest.sym conftest.cpp
      ])
      if test $wx_cv_version_script = yes ; then
        LDFLAGS_VERSIONING="-Wl,--version-script,$1"
      fi
  fi
])


dnl ===========================================================================
dnl "3rd party" macros included here because they are not widely available
dnl ===========================================================================

dnl ---------------------------------------------------------------------------
dnl test for availability of iconv()
dnl ---------------------------------------------------------------------------

dnl From Bruno Haible.

AC_DEFUN([AM_ICONV],
[
  dnl Some systems have iconv in libc, some have it in libiconv (OSF/1 and
  dnl those with the standalone portable GNU libiconv installed).

  AC_ARG_WITH([libiconv-prefix],
[  --with-libiconv-prefix=DIR  search for libiconv in DIR/include and DIR/lib], [
    for dir in `echo "$withval" | tr : ' '`; do
      if test -d $dir/include; then CPPFLAGS="$CPPFLAGS -I$dir/include"; fi
      if test -d $dir/lib; then LDFLAGS="$LDFLAGS -L$dir/lib"; fi
    done
   ])

  AC_CACHE_CHECK(for iconv, am_cv_func_iconv, [
    am_cv_func_iconv="no, consider installing GNU libiconv"
    am_cv_lib_iconv=no
    AC_TRY_LINK([#include <stdlib.h>
#include <iconv.h>],
      [iconv_t cd = iconv_open("","");
       iconv(cd,NULL,NULL,NULL,NULL);
       iconv_close(cd);],
      am_cv_func_iconv=yes)
    if test "$am_cv_func_iconv" != yes; then
      am_save_LIBS="$LIBS"
      LIBS="$LIBS -liconv"
      AC_TRY_LINK([#include <stdlib.h>
#include <iconv.h>],
        [iconv_t cd = iconv_open("","");
         iconv(cd,NULL,NULL,NULL,NULL);
         iconv_close(cd);],
        am_cv_lib_iconv=yes
        am_cv_func_iconv=yes)
      LIBS="$am_save_LIBS"
    fi
  ])
  if test "$am_cv_func_iconv" = yes; then
    AC_DEFINE(HAVE_ICONV, 1, [Define if you have the iconv() function.])
    AC_CACHE_CHECK([if iconv needs const], wx_cv_func_iconv_const,
      AC_TRY_COMPILE([
#include <stdlib.h>
#include <iconv.h>
extern
#ifdef __cplusplus
"C"
#endif
#if defined(__STDC__) || defined(__cplusplus)
size_t iconv (iconv_t cd, char * *inbuf, size_t *inbytesleft, char * *outbuf, size_t *outbytesleft);
#else
size_t iconv();
#endif
        ],
        [],
        wx_cv_func_iconv_const="no",
        wx_cv_func_iconv_const="yes"
      )
    )

    iconv_const=
    if test "x$wx_cv_func_iconv_const" = "xyes"; then
        iconv_const="const"
    fi

    AC_DEFINE_UNQUOTED(ICONV_CONST, $iconv_const,
      [Define as const if the declaration of iconv() needs const.])
  fi
  LIBICONV=
  if test "$am_cv_lib_iconv" = yes; then
    LIBICONV="-liconv"
  fi
  AC_SUBST(LIBICONV)
])

dnl ---------------------------------------------------------------------------
dnl AC_SYS_LARGEFILE (partly based on the code from autoconf 2.5x)
dnl ---------------------------------------------------------------------------

dnl WX_SYS_LARGEFILE_TEST
dnl
dnl NB: original autoconf test was checking if compiler supported 6 bit off_t
dnl     arithmetic properly but this failed miserably with gcc under Linux
dnl     whereas the system still supports 64 bit files, so now simply check
dnl     that off_t is big enough
define(WX_SYS_LARGEFILE_TEST,
[typedef struct {
    unsigned int field: sizeof(off_t) == 8;
} wxlf;
])


dnl WX_SYS_LARGEFILE_MACRO_VALUE(C-MACRO, VALUE, CACHE-VAR)
define(WX_SYS_LARGEFILE_MACRO_VALUE,
[
    AC_CACHE_CHECK([for $1 value needed for large files], [$3],
        [
          AC_TRY_COMPILE([#define $1 $2
                          #include <sys/types.h>],
                         WX_SYS_LARGEFILE_TEST,
                         [$3=$2],
                         [$3=no])
        ]
    )

    if test "$$3" != no; then
        wx_largefile=yes
        AC_DEFINE_UNQUOTED([$1], [$$3])
    fi
])


dnl AC_SYS_LARGEFILE
dnl ----------------
dnl By default, many hosts won't let programs access large files;
dnl one must use special compiler options to get large-file access to work.
dnl For more details about this brain damage please see:
dnl http://www.sas.com/standards/large.file/x_open.20Mar96.html
AC_DEFUN([AC_SYS_LARGEFILE],
[AC_ARG_ENABLE(largefile,
               [  --disable-largefile     omit support for large files])
if test "$enable_largefile" != no; then
    dnl _FILE_OFFSET_BITS==64 is needed for Linux, Solaris, ...
    dnl _LARGE_FILES -- for AIX
    wx_largefile=no
    WX_SYS_LARGEFILE_MACRO_VALUE(_FILE_OFFSET_BITS, 64, ac_cv_sys_file_offset_bits)
    if test "x$wx_largefile" != "xyes"; then
        WX_SYS_LARGEFILE_MACRO_VALUE(_LARGE_FILES, 1, ac_cv_sys_large_files)
    fi

    AC_MSG_CHECKING(if large file support is available)
    if test "x$wx_largefile" = "xyes"; then
        AC_DEFINE(HAVE_LARGEFILE_SUPPORT)
    fi
    AC_MSG_RESULT($wx_largefile)
fi
])


dnl Available from the GNU Autoconf Macro Archive at:
dnl http://www.gnu.org/software/ac-archive/htmldoc/ac_cxx_const_cast.html
dnl
AC_DEFUN([AC_CXX_CONST_CAST],
[AC_CACHE_CHECK(whether the compiler supports const_cast<>,
ac_cv_cxx_const_cast,
[AC_LANG_SAVE
 AC_LANG_CPLUSPLUS
 AC_TRY_COMPILE(,[int x = 0;const int& y = x;int& z = const_cast<int&>(y);return z;],
 ac_cv_cxx_const_cast=yes, ac_cv_cxx_const_cast=no)
 AC_LANG_RESTORE
])
if test "$ac_cv_cxx_const_cast" = yes; then
  AC_DEFINE(HAVE_CONST_CAST,,[define if the compiler supports const_cast<>])
fi
])

dnl http://www.gnu.org/software/ac-archive/htmldoc/ac_cxx_reinterpret_cast.html
AC_DEFUN([AC_CXX_REINTERPRET_CAST],
[AC_CACHE_CHECK(whether the compiler supports reinterpret_cast<>,
ac_cv_cxx_reinterpret_cast,
[AC_LANG_SAVE
 AC_LANG_CPLUSPLUS
 AC_TRY_COMPILE([#include <typeinfo>
class Base { public : Base () {} virtual void f () = 0;};
class Derived : public Base { public : Derived () {} virtual void f () {} };
class Unrelated { public : Unrelated () {} };
int g (Unrelated&) { return 0; }],[
Derived d;Base& b=d;Unrelated& e=reinterpret_cast<Unrelated&>(b);return g(e);],
 ac_cv_cxx_reinterpret_cast=yes, ac_cv_cxx_reinterpret_cast=no)
 AC_LANG_RESTORE
])
if test "$ac_cv_cxx_reinterpret_cast" = yes; then
  AC_DEFINE(HAVE_REINTERPRET_CAST,,
            [define if the compiler supports reinterpret_cast<>])
fi
])

dnl and http://www.gnu.org/software/ac-archive/htmldoc/ac_cxx_static_cast.html
AC_DEFUN([AC_CXX_STATIC_CAST],
[AC_CACHE_CHECK(whether the compiler supports static_cast<>,
ac_cv_cxx_static_cast,
[AC_LANG_SAVE
 AC_LANG_CPLUSPLUS
 AC_TRY_COMPILE([#include <typeinfo>
class Base { public : Base () {} virtual void f () = 0; };
class Derived : public Base { public : Derived () {} virtual void f () {} };
int g (Derived&) { return 0; }],[
Derived d; Base& b = d; Derived& s = static_cast<Derived&> (b); return g (s);],
 ac_cv_cxx_static_cast=yes, ac_cv_cxx_static_cast=no)
 AC_LANG_RESTORE
])
if test "$ac_cv_cxx_static_cast" = yes; then
  AC_DEFINE(HAVE_STATIC_CAST,, [define if the compiler supports static_cast<>])
fi
])