--- configure
+++ configure
@@ -20,10 +20,22 @@
 datarootdir='$(prefix)/share'
 infodir='$(datarootdir)/info'
 mandir='$(datarootdir)/man'
-CXX=g++
-CPPFLAGS=
-CXXFLAGS='-Wall -W -O2'
-LDFLAGS=
+
+if [ -z "${CXX}" ]; then
+	CXX=g++
+fi
+
+if [ -z "${CPPFLAGS}" ]; then
+	CPPFLAGS=
+fi
+
+if [ -z "${CXXFLAGS}" ]; then
+	CXXFLAGS='-Wall -W -O2'
+fi
+
+if [ -z "${LDFLAGS}" ]; then
+	LDFLAGS=
+fi
 
 # checking whether we are using GNU C++.
 /bin/sh -c "${CXX} --version" > /dev/null 2>&1 ||
@@ -46,7 +58,7 @@
 
 	# Split out the argument for options that take them
 	case ${option} in
-	*=*) optarg=`echo ${option} | sed -e 's,^[^=]*=,,;s,/$,,'` ;;
+	*=*) optarg=`echo "${option}" | sed -e 's,^[^=]*=,,;s,/$,,'` ;;
 	esac
 
 	# Process the options
@@ -125,7 +137,7 @@
 	if [ ! -r "${srcdir}/${srctrigger}" ] ; then srcdir=.. ; fi
 	if [ ! -r "${srcdir}/${srctrigger}" ] ; then
 		## the sed command below emulates the dirname command
-		srcdir=`echo $0 | sed -e 's,[^/]*$,,;s,/$,,;s,^$,.,'`
+		srcdir=`echo "$0" | sed -e 's,[^/]*$,,;s,/$,,;s,^$,.,'`
 	fi
 fi
 
--- Makefile.in
+++ Makefile.in
@@ -1,12 +1,11 @@
-
+SHELL = /bin/sh
 DISTNAME = $(pkgname)-$(pkgversion)
 INSTALL = install
 INSTALL_PROGRAM = $(INSTALL) -m 755
 INSTALL_DATA = $(INSTALL) -m 644
 INSTALL_DIR = $(INSTALL) -d -m 755
-SHELL = /bin/sh
 CAN_RUN_INSTALLINFO = $(SHELL) -c "install-info --version" > /dev/null 2>&1
 
 objs = arg_parser.o lzip_index.o list.o encoder_base.o encoder.o \
        fast_encoder.o decoder.o main.o