+# Check for libltdl header (#2999)
+ltdl=0
+AC_MSG_CHECKING(for libltdl)
+AC_ARG_WITH(ltdl,
+ [ --with-ltdl=PFX base of libltdl installation],
+ [AC_MSG_RESULT([$with_ltdl])
+ case $with_ltdl in
+ no)
+ ;;
+ yes)
+ AC_CHECK_HEADERS(ltdl.h,
+ AC_CHECK_LIB([ltdl], [lt_dlopenext],
+ ltdl=1))
+ ;;
+ *)
+ LDFLAGS="-L$with_ltdl/lib $LDFLAGS"
+ CPPFLAGS="-I$with_ltdl/include $CPPFLAGS"
+ AC_CHECK_HEADERS(ltdl.h,
+ AC_CHECK_LIB([ltdl], [lt_dlopenext],
+ EXT_LIB_PATH="-L$with_ltdl/lib $EXT_LIB_PATH"
+ ltdl=1))
+ ;;
+ esac
+ ],
+ [AC_MSG_RESULT([--with-ltdl not specified])
+ AC_CHECK_HEADERS(ltdl.h,
+ AC_CHECK_LIB([ltdl], [lt_dlopenext],
+ ltdl=1))])
+if test "$ltdl" != 1
+then
+ AC_MSG_ERROR([GNUnet requires libltdl (from GNU libtool), try installing libltdl-dev])
+fi
+# restore LIBS
+LIBS=$SAVE_LIBS
+