]> git.saurik.com Git - wxWidgets.git/blobdiff - acinclude.m4
correct radio button best size calculation under CE (was too small by 1 pixel vertica...
[wxWidgets.git] / acinclude.m4
index 81c6f2b474b2908b1239038315e711c25b5d6170..bd3e379f7f4166e23c26490ebd6d60320f02e590 100644 (file)
@@ -8,6 +8,20 @@ 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 ===========================================================================
@@ -29,15 +43,15 @@ for ac_dir in $1 /usr/include;
 ])
 
 dnl ---------------------------------------------------------------------------
-dnl call WX_PATH_FIND_LIBRARIES(search path, header name), sets ac_find_libraries
+dnl call WX_PATH_FIND_LIBRARIES(search path, lib 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;
+  ac_find_libraries=
+  for ac_dir in $1;
   do
-    for ac_extension in a so sl dylib; do
+    for ac_extension in a so sl dylib dll.a; do
       if test -f "$ac_dir/lib$2.$ac_extension"; then
         ac_find_libraries=$ac_dir
         break 2
@@ -46,6 +60,19 @@ for ac_dir in $1 /usr/lib;
   done
 ])
 
+dnl ---------------------------------------------------------------------------
+dnl return list of standard library paths
+dnl ---------------------------------------------------------------------------
+dnl return all default locations:
+dnl   - /usr/lib: standard
+dnl   - /usr/lib32: n32 ABI on IRIX
+dnl   - /usr/lib64: n64 ABI on IRIX
+dnl   - /usr/lib/64: 64 bit ABI on Solaris and Linux x86-64
+dnl
+dnl NB: if any of directories in the list is not a subdir of /usr, code setting
+dnl     wx_cv_std_libpath needs to be updated
+AC_DEFUN([WX_STD_LIBPATH], [/usr/lib /usr/lib32 /usr/lib/64 /usr/lib64])
+
 dnl ---------------------------------------------------------------------------
 dnl Path to include, already defined
 dnl ---------------------------------------------------------------------------
@@ -66,16 +93,25 @@ AC_DEFUN([WX_INCLUDE_PATH_EXIST],
 ])
 
 dnl ---------------------------------------------------------------------------
-dnl Path to link, already defined
+dnl Usage: WX_LINK_PATH_EXIST(path, libpath)
+dnl
+dnl Set ac_path_to_link to nothing if path is already in libpath of to -Lpath
+dnl if it is not, so that libpath can be set to "$libpath$ac_path_to_link"
+dnl after calling this function
 dnl ---------------------------------------------------------------------------
 AC_DEFUN([WX_LINK_PATH_EXIST],
 [
-  echo "$2" | grep "\-L$1" > /dev/null
-  result=$?
-  if test $result = 0; then
+  dnl never add -L/usr/libXXX explicitely to libpath
+  if test "$1" = "default location"; then
     ac_path_to_link=""
   else
-    ac_path_to_link=" -L$1"
+    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
   fi
 ])
 
@@ -88,18 +124,15 @@ 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-or-cross-compiling)
+dnl call WX_CPP_NEW_HEADERS(actiof-if-true, action-if-false)
 dnl ---------------------------------------------------------------------------
 
 AC_DEFUN([WX_CPP_NEW_HEADERS],
 [
-  if test "$cross_compiling" = "yes"; then
-    ifelse([$2], , :, [$2])
-  else
     AC_LANG_SAVE
     AC_LANG_CPLUSPLUS
 
-    AC_CHECK_HEADERS(iostream)
+    AC_CHECK_HEADERS([iostream],,, [ ])
 
     if test "$ac_cv_header_iostream" = "yes" ; then
       ifelse([$1], , :, [$1])
@@ -108,7 +141,6 @@ AC_DEFUN([WX_CPP_NEW_HEADERS],
     fi
 
     AC_LANG_RESTORE
-  fi
 ])
 
 dnl ---------------------------------------------------------------------------
@@ -195,6 +227,72 @@ AC_DEFUN([WX_CPP_EXPLICIT],
   fi
 ])
 
+dnl ---------------------------------------------------------------------------
+dnl WX_CHECK_FUNCS(FUNCTIONS...,
+dnl                [ACTION-IF-FOUND],
+dnl                [ACTION-IF-NOT-FOUND],
+dnl                [EXTRA-DEFINES-AND-INCLUDES],
+dnl                [EXTRA-TEST-CODE])
+dnl
+dnl Checks that the functions listed in FUNCTIONS exist in the headers and the
+dnl libs. For each function, if it is found then defines 'HAVE_FUNCTION' and
+dnl executes ACTION-IF-FOUND, otherwise executes ACTION-IF-NOT-FOUND.
+dnl
+dnl The code from EXTRA-DEFINES-AND-INCLUDES is inserted into the test before
+dnl the default headers are included, and EXTRA-TEST-CODE is inserted into
+dnl the main() function after the default test for existence.
+dnl
+dnl Examples:
+dnl   # the simple case
+dnl   WX_CHECK_FUNCS(stat)
+dnl   # use break to finish the loop early
+dnl   WX_CHECK_FUNCS(mkstemp mktemp, break)
+dnl   # extra defines
+dnl   WX_CHECK_FUNCS(strtok_r, [], [], [#define _RREENTRANT])
+dnl   # extra includes
+dnl   WX_CHECK_FUNCS(swprintf, [], [], [#include <wchar.h>])
+dnl   # checking the signature with extra test code
+dnl   WX_CHECK_FUNCS(gettimeofday, [], [], [#include <sys/time.h>]
+dnl     [struct timeval tv; struct timezone tz; gettimeofday(&tv, &tz)])
+dnl ---------------------------------------------------------------------------
+
+AC_DEFUN([WX_CHECK_FUNCS],
+[
+  for wx_func in $1
+  do
+    AC_CACHE_CHECK(
+      [for $wx_func],
+      [wx_cv_func_$wx_func],
+      [
+        AC_LINK_IFELSE(
+          [
+            AC_LANG_PROGRAM(
+              [
+                $4
+                AC_INCLUDES_DEFAULT
+              ],
+              [
+                #ifndef $wx_func
+                  &$wx_func;
+                #endif
+                $5
+              ])
+          ],
+          [eval wx_cv_func_$wx_func=yes],
+          [eval wx_cv_func_$wx_func=no])
+      ])
+
+    if eval test \$wx_cv_func_$wx_func = yes
+    then
+      AC_DEFINE_UNQUOTED([AS_TR_CPP([HAVE_$wx_func])])
+      $2
+    else
+      :
+      $3
+    fi
+  done
+])
+
 dnl ---------------------------------------------------------------------------
 dnl a slightly better AC_C_BIGENDIAN macro which allows cross-compiling
 dnl ---------------------------------------------------------------------------
@@ -234,60 +332,38 @@ fi
 ])
 
 dnl ---------------------------------------------------------------------------
-dnl override AC_ARG_ENABLE/WITH to cache the results in .cache file
+dnl override AC_ARG_ENABLE/WITH to handle options defaults
 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)
+dnl
+dnl the default value (used if the option is not specified at all) is the value
+dnl of wxUSE_ALL_FEATURES (which is "yes" by default but can be changed by
+dnl giving configure --disable-all-features option)
 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'
+                          AS_TR_SH(wx_cv_use_$1)='$3=yes'
                         elif test "$withval" = no; then
-                          ac_cv_use_$1='$3=no'
+                          AS_TR_SH(wx_cv_use_$1)='$3=no'
                         elif test "$withval" = sys; then
-                          ac_cv_use_$1='$3=sys'
+                          AS_TR_SH(wx_cv_use_$1)='$3=sys'
                         elif test "$withval" = builtin; then
-                          ac_cv_use_$1='$3=builtin'
+                          AS_TR_SH(wx_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
+                        AS_TR_SH(wx_cv_use_$1)='$3=${'DEFAULT_$3":-$wxUSE_ALL_FEATURES}"
                       ])
 
-          eval "$ac_cv_use_$1"
-          if test "$no_cache" != 1; then
-            echo $ac_cv_use_$1 >> ${wx_arg_cache_file}.tmp
-          fi
+          eval "$AS_TR_SH(wx_cv_use_$1)"
 
           if test "$$3" = yes; then
             AC_MSG_RESULT(yes)
@@ -302,85 +378,136 @@ AC_DEFUN([WX_ARG_SYS_WITH],
           fi
         ])
 
-dnl this macro checks for a command line argument and caches the result
-dnl usage: WX_ARG_WITH(option, helpmessage, variable-name)
+dnl this macro simply checks for a command line argument
+dnl usage: WX_ARG_WITH(option, helpmessage, variable-name, [withstring])
 AC_DEFUN([WX_ARG_WITH],
         [
-          AC_MSG_CHECKING([for --with-$1])
-          no_cache=0
+          withstring=$4
+          defaultval=$wxUSE_ALL_FEATURES
+          if test -z "$defaultval"; then
+              if test x"$withstring" = xwithout; then
+                  defaultval=yes
+              else
+                  defaultval=no
+              fi
+          fi
+          AC_MSG_CHECKING([for --${withstring:-with}-$1])
           AC_ARG_WITH($1, [$2],
                       [
                         if test "$withval" = yes; then
-                          ac_cv_use_$1='$3=yes'
+                          AS_TR_SH(wx_cv_use_$1)='$3=yes'
                         else
-                          ac_cv_use_$1='$3=no'
+                          AS_TR_SH(wx_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
+                        AS_TR_SH(wx_cv_use_$1)='$3=${'DEFAULT_$3":-$defaultval}"
                       ])
 
-          eval "$ac_cv_use_$1"
-          if test "$no_cache" != 1; then
-            echo $ac_cv_use_$1 >> ${wx_arg_cache_file}.tmp
-          fi
+          eval "$AS_TR_SH(wx_cv_use_$1)"
 
-          if test "$$3" = yes; then
-            AC_MSG_RESULT(yes)
+          if test x"$withstring" = xwithout; then
+            if test $$3 = yes; then
+              result=no
+            else
+              result=yes
+            fi
           else
-            AC_MSG_RESULT(no)
+            result=$$3
           fi
+
+          AC_MSG_RESULT($result)
         ])
 
+dnl same as WX_ARG_WITH but makes it clear that the option is enabled by default
+AC_DEFUN([WX_ARG_WITHOUT], [WX_ARG_WITH($1, [$2], $3, without)])
+
 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 usage: WX_ARG_ENABLE(option, helpmessage, var, [enablestring], [default])
 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
+dnl enablestring can be omitted or a literal string "disable" and allows to
+dnl show "checking for --disable-foo" message when running configure instead of
+dnl the default "checking for --enable-foo" one whih is useful for the options
+dnl enabled by default
+dnl
+dnl the "default" argument can be omitted or contain the default value to use
+dnl for the option if it's unspecified
 AC_DEFUN([WX_ARG_ENABLE],
         [
-         enablestring=$4
+          enablestring=$4
+          defaultval=$5
+          if test -z "$defaultval"; then
+              if test x"$enablestring" = xdisable; then
+                  defaultval=yes
+              else
+                  defaultval=no
+              fi
+          fi
+
           AC_MSG_CHECKING([for --${enablestring:-enable}-$1])
-          no_cache=0
           AC_ARG_ENABLE($1, [$2],
                         [
                           if test "$enableval" = yes; then
-                            ac_cv_use_$1='$3=yes'
+                            AS_TR_SH(wx_cv_use_$1)='$3=yes'
                           else
-                            ac_cv_use_$1='$3=no'
+                            AS_TR_SH(wx_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
+                          AS_TR_SH(wx_cv_use_$1)='$3=${'DEFAULT_$3":-$defaultval}"
                         ])
 
-          eval "$ac_cv_use_$1"
-          if test "$no_cache" != 1; then
-            echo $ac_cv_use_$1 >> ${wx_arg_cache_file}.tmp
-          fi
+          eval "$AS_TR_SH(wx_cv_use_$1)"
 
-          if test "$$3" = yes; then
-            AC_MSG_RESULT(yes)
+          if test x"$enablestring" = xdisable; then
+            if test $$3 = yes; then
+              result=no
+            else
+              result=yes
+            fi
           else
-            AC_MSG_RESULT(no)
+            result=$$3
           fi
+
+          AC_MSG_RESULT($result)
         ])
 
+dnl the same as WX_ARG_ENABLE but makes it more clear that the option is
+dnl enabled by default
+AC_DEFUN([WX_ARG_DISABLE], [WX_ARG_ENABLE($1, [$2], $3, disable)])
+
+dnl same as WX_ARG_ENABLE but defaults to wxUSE_ALL_FEATURES instead of "yes"
+AC_DEFUN([WX_ARG_FEATURE], [WX_ARG_ENABLE($1, [$2], $3,, $wxUSE_ALL_FEATURES)])
+
+dnl Like WX_ARG_ENABLE but accepts a parameter.
+dnl
+dnl Usage:
+dnl   WX_ARG_ENABLE_PARAM(option, helpmessage, variable-name, enablestring)
+dnl
+dnl Example:
+dnl   WX_ARG_ENABLE_PARAM(foo, [[  --enable-foo[=bar] use foo]], wxUSE_FOO)
+dnl
+dnl  --enable-foo       wxUSE_FOO=yes
+dnl  --disable-foo      wxUSE_FOO=no
+dnl  --enable-foo=bar   wxUSE_FOO=bar
+dnl  <not given>        wxUSE_FOO=$DEFAULT_wxUSE_FOO
+dnl
+AC_DEFUN([WX_ARG_ENABLE_PARAM],
+        [
+          enablestring=$4
+          AC_MSG_CHECKING([for --${enablestring:-enable}-$1])
+          AC_ARG_ENABLE($1, [$2],
+                        [
+                          wx_cv_use_$1="$3='$enableval'"
+                        ],
+                        [
+                          wx_cv_use_$1='$3='$DEFAULT_$3
+                        ])
+
+          eval "$wx_cv_use_$1"
+
+          AC_MSG_RESULT([$$3])
+        ])
 
 dnl ===========================================================================
 dnl Linker features test
@@ -395,44 +522,80 @@ 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,$1"
-      fi
-  fi
+    case "${host}" in
+        *-*-cygwin* | *-*-mingw* )
+            dnl although ld does support version script option on these
+            dnl platforms, it doesn't make much sense to use it under Win32
+            dnl and, moreover, this breaks linking because of a bug in handling
+            dnl paths in -Wl,--version-script,path option (if we ever do need
+            dnl to use it for cygwin/mingw32, keep in mind that replacing last
+            dnl comma with the equal sign works) so
+            dnl simply disable it
+            wx_cv_version_script=no
+            ;;
+
+        *)
+            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
+            ;;
+    esac
 ])
 
 
@@ -599,6 +762,27 @@ if test "$ac_cv_cxx_const_cast" = yes; then
 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 "$ac_cv_cxx_reinterpret_cast" = yes; then
+  AC_DEFINE(HAVE_REINTERPRET_CAST,,
+            [define if the compiler supports reinterpret_cast<>])
+fi
+])
+
 dnl and http://www.gnu.org/software/ac-archive/htmldoc/ac_cxx_static_cast.html
 AC_DEFUN([AC_CXX_STATIC_CAST],
 [AC_CACHE_CHECK(whether the compiler supports static_cast<>,
@@ -617,3 +801,22 @@ if test "$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
+])
+