Quote "$d" when testing it in "AC_LBL_LIBPCAP", so that if it's empty -

[tcpdump] / configure

diff --git a/configure b/configure
index 728cccb9116b2f78e9625e73b4eb1c62d37b3292..544767927fe645805cd0d1b3633b90e1b5b05f13 100755 (executable)
--- a/configure
+++ b/configure
@@ -3930,7 +3930,7 @@ echo "configure:3925: checking for extraneous pcap header directories" >&5
                    d="/usr/include/pcap"
                fi
            fi
-           if test -z $d ; then
+           if test -z "$d" ; then
                echo "$ac_t""not found" 1>&6
            else
                V_INCLS="-I$d $V_INCLS"