added mouse wheel event test; don't trap left mouse clicks in MyCanvas as this makes...

[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 Objective-C(++) related macros
dnl ===========================================================================
m4_define([AC_WX_LANG_OBJECTIVEC],
[AC_LANG(C)
ac_ext=m
])

m4_define([AC_WX_LANG_OBJECTIVECPLUSPLUS],
[AC_LANG(C++)
ac_ext=mm
])

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 $1 /usr/lib;
  do
    for ac_extension in a so sl dylib dll.a; do
      if test -f "$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

        dnl There's a problem in some old linkers with --version-script that
        dnl can cause linking to fail when you have objects with vtables in
        dnl libs 3 deep.  This is known to happen in netbsd and openbsd with
        dnl ld 2.11.2.
        dnl 
        dnl To test for this we need to make some shared libs and
        dnl unfortunately we can't be sure of the right way to do that. If the
        dnl first two compiles don't succeed then it looks like the test isn't
        dnl working and the result is ignored, but if OTOH the first two
        dnl succeed but the third does not then the bug has been detected and
        dnl the --version-script flag is dropped.
        if test $wx_cv_version_script = yes
        then
          echo "struct B { virtual ~B() { } }; \
                struct D : public B { }; \
                void F() { D d; }" > conftest.cpp

          if AC_TRY_COMMAND([
                $CXX -shared -fPIC -o conftest1.output $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.cpp
                -Wl,--version-script,conftest.sym >/dev/null 2>/dev/null]) &&
             AC_TRY_COMMAND([
                $CXX -shared -fPIC -o conftest2.output $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.cpp
                -Wl,--version-script,conftest.sym conftest1.output >/dev/null 2>/dev/null])
          then
            if AC_TRY_COMMAND([
                  $CXX -shared -fPIC -o conftest3.output $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.cpp
                  -Wl,--version-script,conftest.sym conftest2.output conftest1.output >/dev/null 2>/dev/null])
            then
              wx_cv_version_script=yes
            else
              wx_cv_version_script=no
            fi
          fi
        fi

        rm -f conftest.output conftest.stderr conftest.sym conftest.cpp
        rm -f conftest1.output conftest2.output conftest3.output
      ])
      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
])

dnl http://autoconf-archive.cryp.to/ac_cxx_dynamic_cast.html
AC_DEFUN([AC_CXX_DYNAMIC_CAST],
[AC_CACHE_CHECK(whether the compiler supports dynamic_cast<>,
ac_cv_cxx_dynamic_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 () {} };],[
Derived d; Base& b=d; return dynamic_cast<Derived*>(&b) ? 0 : 1;],
 ac_cv_cxx_dynamic_cast=yes, ac_cv_cxx_dynamic_cast=no)
 AC_LANG_RESTORE
])
if test "$ac_cv_cxx_dynamic_cast" = yes; then
  AC_DEFINE(HAVE_DYNAMIC_CAST,,[define if the compiler supports dynamic_cast<>])
fi
])