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],
[  --with-libiconv=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_LINK_IFELSE([AC_LANG_PROGRAM([[#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="$LIBS -liconv"
      AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include <stdlib.h>
#include <iconv.h>]], [[iconv_t cd = iconv_open("","");
         iconv(cd,NULL,NULL,NULL,NULL);
         iconv_close(cd);]])],[am_cv_lib_iconv=yes
        am_cv_func_iconv=yes],[])
      LIBS="$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_MSG_CHECKING([for iconv declaration])
    AC_CACHE_VAL(am_cv_proto_iconv, [
      AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
#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
]], [[]])],[am_cv_proto_iconv_arg1=""],[am_cv_proto_iconv_arg1="const"])
      am_cv_proto_iconv="extern size_t iconv (iconv_t cd, $am_cv_proto_iconv_arg1 char * *inbuf, size_t *inbytesleft, char * *outbuf, size_t *outbytesleft);"])
    am_cv_proto_iconv=`echo "[$]am_cv_proto_iconv" | tr -s ' ' | sed -e 's/( /(/'`
    AC_MSG_RESULT([$]{ac_t:-
         }[$]am_cv_proto_iconv)
    AC_DEFINE_UNQUOTED(ICONV_CONST, $am_cv_proto_iconv_arg1,
      [Define as const if the declaration of iconv() needs const.])
  else
    AC_MSG_FAILURE([iconv() not found. Please install libiconv and use --with-libiconv=/path/to/dir.],[1])
  fi
  if test "$am_cv_lib_iconv" = yes; then
    LIBS="$LIBS -liconv"
  fi
])