failed first attempt at linking against libgnunetutil

configure.ac

@@ -13,6 +13,10 @@ AC_CONFIG_SRCDIR([brandt.c])
 AC_PROG_CC_C99
 LT_INIT([pic-only])
 
+# fix std
+CC=$(echo "${CC}" | sed 's/-std=gnu99/-std=c99/')
+CPP=$(echo "${CC}" | sed 's/-std=gnu99/-std=c99/')
+
 # Checks for libraries.
 AC_SEARCH_LIBS([gcry_check_version], [gcrypt], [], [AC_MSG_ERROR([unable to find the gcry_check_version() function from libgcrypt])])
 
@@ -23,11 +27,42 @@ AC_CHECK_HEADER(gcrypt.h, [], [AC_MSG_ERROR([unable to find the gcrypt.h header
 AC_TYPE_SIZE_T
 AC_TYPE_UINT16_T
 
-# Checks for library functions.
+SAVE_LIBS=$LIBS
-
+gnunetutil=0
-# fix std
+AC_MSG_CHECKING(for libgnunetutil)
-CC=$(echo "${CC}" | sed 's/-std=gnu99/-std=c99/')
+AC_ARG_WITH(gnunetutil,
-CPP=$(echo "${CC}" | sed 's/-std=gnu99/-std=c99/')
+   [  --with-gnunetutil=PFX   base of libgnunetutil installation],
+   [AC_MSG_RESULT([$with_gnunetutil])
+    case $with_gnunetutil in
+      no)
+        ;;
+      yes)
+        AC_CHECK_HEADERS(gnunet/gnunet_util_lib.h,
+          AC_CHECK_LIB([gnunetutil], [GNUNET_CRYPTO_ecc_dlog],
+            gnunetutil=1))
+        ;;
+      *)
+        LDFLAGS="-L$with_gnunetutil/lib $LDFLAGS"
+        CPPFLAGS="-I$with_gnunetutil/include $CPPFLAGS"
+        AC_CHECK_HEADERS(gnunet/gnunet_util_lib.h,
+          AC_CHECK_LIB([gnunetutil], [GNUNET_CRYPTO_ecc_dlog],
+            EXT_LIB_PATH="-L$with_gnunetutil/lib $EXT_LIB_PATH"
+            gnunetutil=1))
+        ;;
+    esac
+   ],
+   [AC_MSG_RESULT([--with-gnunetutil not specified])
+    AC_CHECK_HEADERS(gnunet/gnunet_util_lib.h,
+     AC_CHECK_LIB([gnunetutil], [GNUNET_CRYPTO_ecc_dlog],
+      gnunetutil=1))])
+if test x$gnunetutil = x1
+then
+ AC_MSG_RESULT([libgnunetutil found])
+else
+ AC_MSG_ERROR([libbrandt requires libgnunetutil])
+fi
+# restore LIBS
+LIBS=$SAVE_LIBS
 
 AC_CONFIG_FILES([
 Makefile