Set -o nounset in addition to +o errexit -o nounset.

groups/000.host_tools.group:libtool_host:${PKG_LIBTOOL}: build w/ `none'.
subr/build_init.subr:buildp_init_getopts(): set ${DEFAULT_BUILD_CPUS} prior to ex_pkg_load_vars() call.
subr/pkg_{build,install_make}.subr: only pass `LIBTOOL=${PKG_LIBTOOL}' if set and not `none'.
vars/libtool_host.vars: removes obsolete vars file.

29 files changed, 220 insertions, 186 deletions

diff --git a/subr/build_init.subr b/subr/build_init.subr
index 91784f83..6d1635db 100644
--- a/subr/build_init.subr
+++ b/subr/build_init.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 buildp_init_args() {
@@ -11,86 +11,72 @@ buildp_init_args() {
 	&& [ -e "${PREFIX}/build.gitref" ]\
 	&& [ "$(git rev-parse HEAD)" = "$(cat "${PREFIX}/build.gitref")" ]; then
 		_rc=0; _status="Git repository has not changed since last build and --as-needed was specified.";
-	else	case "${ARG_PARALLEL}" in
-		auto)	if ! ARG_PARALLEL="$(rtl_get_cpu_count)"; then
-				_rc=1; _status="Error: failed to get CPU count.";
-			else
-				ARG_PARALLEL=$((${ARG_PARALLEL}/2));
-			fi; ;;
-		"")	ARG_PARALLEL=1; ;;
-		*)	if ! rtl_isnumber "${ARG_PARALLEL}"; then
-				_rc=1; _status="Error: invalid jobs count \`${ARG_PARALLEL}'.";
-			fi; ;;
+	else	case "${ARG_FETCH_FORCE}" in
+		ipv4)	DEFAULT_GIT_ARGS="$(rtl_lconcat "-4" "${DEFAULT_GIT_ARGS}")";
+			DEFAULT_WGET_ARGS="$(rtl_lconcat "-4" "${DEFAULT_GIT_ARGS}")"; ;;
+		ipv6)	DEFAULT_GIT_ARGS="$(rtl_lconcat "-6" "${DEFAULT_GIT_ARGS}")";
+			DEFAULT_WGET_ARGS="$(rtl_lconcat "-6" "${DEFAULT_GIT_ARGS}")"; ;;
+		esac;
+		case "${ARG_RESTART}" in
+		\*\*\*[a-zA-Z]*)
+				ARG_RESTART="${ARG_RESTART#\*\*\*}"; ARG_RESTART_RECURSIVE=3; ;;
+		\*\*[a-zA-Z]*)	ARG_RESTART="${ARG_RESTART#\*\*}"; ARG_RESTART_RECURSIVE=2; ;;
+		\*[a-zA-Z]*)	ARG_RESTART="${ARG_RESTART#\*}"; ARG_RESTART_RECURSIVE=1; ;;
+		ALL)		ARG_RESTART_AT=ALL; ARG_RESTART_RECURSIVE=2; ;;
+		LAST)		ARG_RESTART_AT=ALL; ARG_RESTART_RECURSIVE=0;
+				if [ -n "${DEFAULT_BUILD_LAST_FAILED_PKG_FNAME}" ]\
+				&& [ -e "${DEFAULT_BUILD_LAST_FAILED_PKG_FNAME}" ]; then
+					_last_pkg="$(cat "${DEFAULT_BUILD_LAST_FAILED_PKG_FNAME}")";
+					rtl_fileop rm "${DEFAULT_BUILD_LAST_FAILED_PKG_FNAME}";
+					rtl_state_clear "${BUILD_WORKDIR}" "${_last_pkg}";
+					ARG_RESTART="${_last_pkg}";
+				else
+					_rc=1; _status="Error: cannot rebuild last failed package.";
+				fi; ;;
 		esac;
 		if [ "${_rc:-0}" -eq 0 ]; then
-			DEFAULT_BUILD_CPUS="${ARG_PARALLEL}";
-			case "${ARG_FETCH_FORCE}" in
-			ipv4)	DEFAULT_GIT_ARGS="$(rtl_lconcat "-4" "${DEFAULT_GIT_ARGS}")";
-				DEFAULT_WGET_ARGS="$(rtl_lconcat "-4" "${DEFAULT_GIT_ARGS}")"; ;;
-			ipv6)	DEFAULT_GIT_ARGS="$(rtl_lconcat "-6" "${DEFAULT_GIT_ARGS}")";
-				DEFAULT_WGET_ARGS="$(rtl_lconcat "-6" "${DEFAULT_GIT_ARGS}")"; ;;
-			esac;
 			case "${ARG_RESTART}" in
-			\*\*\*[a-zA-Z]*)
-					ARG_RESTART="${ARG_RESTART#\*\*\*}"; ARG_RESTART_RECURSIVE=3; ;;
-			\*\*[a-zA-Z]*)	ARG_RESTART="${ARG_RESTART#\*\*}"; ARG_RESTART_RECURSIVE=2; ;;
-			\*[a-zA-Z]*)	ARG_RESTART="${ARG_RESTART#\*}"; ARG_RESTART_RECURSIVE=1; ;;
-			ALL)		ARG_RESTART_AT=ALL; ARG_RESTART_RECURSIVE=2; ;;
-			LAST)		ARG_RESTART_AT=ALL; ARG_RESTART_RECURSIVE=0;
-					if [ -n "${DEFAULT_BUILD_LAST_FAILED_PKG_FNAME}" ]\
-					&& [ -e "${DEFAULT_BUILD_LAST_FAILED_PKG_FNAME}" ]; then
-						_last_pkg="$(cat "${DEFAULT_BUILD_LAST_FAILED_PKG_FNAME}")";
-						rtl_fileop rm "${DEFAULT_BUILD_LAST_FAILED_PKG_FNAME}";
-						rtl_state_clear "${BUILD_WORKDIR}" "${_last_pkg}";
-						ARG_RESTART="${_last_pkg}";
-					else
-						_rc=1; _status="Error: cannot rebuild last failed package.";
-					fi; ;;
+			*:*)		ARG_RESTART_AT="${ARG_RESTART#*:}"; ARG_RESTART="$(rtl_llift "${ARG_RESTART%%:*}" "," " ")"; ;;
+			*)		ARG_RESTART="$(rtl_llift "${ARG_RESTART}" "," " ")"; ARG_RESTART_AT=ALL; ;;
 			esac;
-			if [ "${_rc:-0}" -eq 0 ]; then
-				case "${ARG_RESTART}" in
-				*:*)		ARG_RESTART_AT="${ARG_RESTART#*:}"; ARG_RESTART="$(rtl_llift "${ARG_RESTART%%:*}" "," " ")"; ;;
-				*)		ARG_RESTART="$(rtl_llift "${ARG_RESTART}" "," " ")"; ARG_RESTART_AT=ALL; ;;
-				esac;
-				if ! ex_pkg_load_groups; then
-					_rc=1; _status="Error: failed to load build groups.";
-				else	if ! rtl_lmatch "${ARG_DIST}" "rpm" ","; then
-						EX_PKG_BUILD_GROUPS="$(rtl_lfilter "${EX_PKG_BUILD_GROUPS}" "host_deps_rpm")";
+			if ! ex_pkg_load_groups; then
+				_rc=1; _status="Error: failed to load build groups.";
+			else	if ! rtl_lmatch "${ARG_DIST}" "rpm" ","; then
+					EX_PKG_BUILD_GROUPS="$(rtl_lfilter "${EX_PKG_BUILD_GROUPS}" "host_deps_rpm")";
+				fi;
+				if [ -z "${BUILD_GROUPS}" ]; then
+					BUILD_GROUPS="${EX_PKG_BUILD_GROUPS}";
+				else	for _group in ${BUILD_GROUPS}; do
+						if ! rtl_lmatch "${EX_PKG_BUILD_GROUPS}" "${_group}"; then
+							_rc=1; _status="Error: unknown build group \`${_group}'."; break;
+						fi;
+					done;
+				fi;
+				if [ "${_rc:-0}" -eq 0 ]; then
+					if [ -n "${ARG_DIST}" ]; then
+						BUILD_GROUPS="$(rtl_lconcat "$(rtl_lfilter "${BUILD_GROUPS}" "dist")" "dist")";
 					fi;
-					if [ -z "${BUILD_GROUPS}" ]; then
-						BUILD_GROUPS="${EX_PKG_BUILD_GROUPS}";
-					else	for _group in ${BUILD_GROUPS}; do
-							if ! rtl_lmatch "${EX_PKG_BUILD_GROUPS}" "${_group}"; then
-								_rc=1; _status="Error: unknown build group \`${_group}'."; break;
+					if [ -n "${ARG_RESTART}" ]; then
+						for _pkg_name in ${ARG_RESTART}; do
+							if ! ex_pkg_find_package "${BUILD_GROUPS}" "${_pkg_name}" >/dev/null; then
+								_pkg_names_unknown="$(rtl_lconcat "${_pkg_names_unknown}" "${_pkg_name}")";
 							fi;
 						done;
+						case "$(rtl_llength "${_pkg_names_unknown}")" in
+						0)	;;
+						1)	_rc=1; _status="Error: unknown package \`${_pkg_names_unknown}'."; ;;
+						*)	_rc=1; _status="Error: unknown packages: $(rtl_subst "${_pkg_names_unknown}" " " ", ")"; ;;
+						esac;
 					fi;
-					if [ "${_rc:-0}" -eq 0 ]; then
-						if [ -n "${ARG_DIST}" ]; then
-							BUILD_GROUPS="$(rtl_lconcat "$(rtl_lfilter "${BUILD_GROUPS}" "dist")" "dist")";
-						fi;
-						if [ -n "${ARG_RESTART}" ]; then
-							for _pkg_name in ${ARG_RESTART}; do
-								if ! ex_pkg_find_package "${BUILD_GROUPS}" "${_pkg_name}" >/dev/null; then
-									_pkg_names_unknown="$(rtl_lconcat "${_pkg_names_unknown}" "${_pkg_name}")";
-								fi;
-							done;
-							case "$(rtl_llength "${_pkg_names_unknown}")" in
-							0)	;;
-							1)	_rc=1; _status="Error: unknown package \`${_pkg_names_unknown}'."; ;;
-							*)	_rc=1; _status="Error: unknown packages: $(rtl_subst "${_pkg_names_unknown}" " " ", ")"; ;;
-							esac;
-						fi;
-						if [ "${_rc}" -eq 0 ]; then
-							case "${ARG_VERBOSE:-0}" in
-							0)	rtl_fileop_set_log 0; rtl_log_set_lvl 0; ;;
-							1)	rtl_fileop_set_log 0; rtl_log_set_lvl 2; ;;
-							2)	rtl_fileop_set_log 0; rtl_log_set_lvl 2; ;;
-							3)	rtl_fileop_set_log 0; rtl_log_set_lvl 2; ;;
-							4)	rtl_fileop_set_log 1; rtl_log_set_lvl 3; ;;
-							*)	_rc=1; _status="Error: invalid verbosity level (max. -vvvv)"; ;;
-							esac;
-						fi;
+					if [ "${_rc}" -eq 0 ]; then
+						case "${ARG_VERBOSE:-0}" in
+						0)	rtl_fileop_set_log 0; rtl_log_set_lvl 0; ;;
+						1)	rtl_fileop_set_log 0; rtl_log_set_lvl 2; ;;
+						2)	rtl_fileop_set_log 0; rtl_log_set_lvl 2; ;;
+						3)	rtl_fileop_set_log 0; rtl_log_set_lvl 2; ;;
+						4)	rtl_fileop_set_log 1; rtl_log_set_lvl 3; ;;
+						*)	_rc=1; _status="Error: invalid verbosity level (max. -vvvv)"; ;;
+						esac;
 					fi;
 				fi;
 			fi;
@@ -156,7 +142,7 @@ buildp_init_getopts() {
 	: ${ARCH:="nt64"}; : ${BUILD:="debug"};
 	ARG_AS_NEEDED=0; ARG_CLEAN_BUILDS=""; ARG_DEBUG_MINIPIX=0; ARG_DIST=1; ARG_DUMP_IN="";
 	ARG_DUMP_ON_ABORT=0; ARG_FETCH_FORCE=0; ARG_PARALLEL=1; ARG_RELAXED=0; ARG_RESTART="";
-	ARG_VERBOSE=0;
+	ARG_RESTART_AT=""; ARG_RESTART_RECURSIVE=""; ARG_VERBOSE=0;
 	while [ "${#}" -gt 0 ]; do
 		case "${1}" in
 		--as-needed)	ARG_AS_NEEDED=1; _shiftfl=1; ;;
@@ -209,6 +195,22 @@ buildp_init_getopts() {
 			*)		BUILD_GROUPS="$(rtl_lconcat "${BUILD_GROUPS}" "${_arg}")"; ;;
 			esac; shift;
 		done;
+		if [ "${_rc:-0}" -eq 0 ]; then
+			case "${ARG_PARALLEL}" in
+			auto)	if ! ARG_PARALLEL="$(rtl_get_cpu_count)"; then
+					_rc=1; _status="Error: failed to get CPU count.";
+				else
+					ARG_PARALLEL=$((${ARG_PARALLEL}/2));
+				fi; ;;
+			"")	ARG_PARALLEL=1; ;;
+			*)	if ! rtl_isnumber "${ARG_PARALLEL}"; then
+					_rc=1; _status="Error: invalid jobs count \`${ARG_PARALLEL}'.";
+				fi; ;;
+			esac;
+			if [ "${_rc:-0}" -eq 0 ]; then
+				DEFAULT_BUILD_CPUS="${ARG_PARALLEL}";
+			fi;
+		fi;
 	fi;
 	return "${_rc}";
 };
diff --git a/subr/ex_pkg.subr b/subr/ex_pkg.subr
index 3dcfbc7e..e19d987d 100644
--- a/subr/ex_pkg.subr
+++ b/subr/ex_pkg.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 #
@@ -130,14 +130,14 @@ ex_pkg_load_groups() {
 	local  _build_groups="" _fname="" _group="" _groups="";
 	for _fname in $(find ./groups -name *.group | sort); do
 		rtl_fileop source_opt "${_fname}";
-		if [ -n "${GROUP_TARGET}" ]; then
+		if [ -n "${GROUP_TARGET:-}" ]; then
 			_group="${GROUP_TARGET}"; unset GROUP_TARGET;
 		else
 			_group="${_fname##*/}"; _group="${_group%.group}"; _group="${_group#*.}";
 		fi;
 		if ! rtl_lmatch "${_groups}" "${_group}"; then
 			_groups="$(rtl_lconcat "${_groups}" "${_group}")";
-			if [ -n "${GROUP_AUTO}" ]; then
+			if [ -n "${GROUP_AUTO:-}" ]; then
 				if [ "${GROUP_AUTO:-0}" -ne 0 ]; then
 					_build_groups="$(rtl_lconcat "${_build_groups}" "${_group}")";
 				fi;
diff --git a/subr/ex_pkg_dispatch.subr b/subr/ex_pkg_dispatch.subr
index 44ed8d43..669357cd 100644
--- a/subr/ex_pkg_dispatch.subr
+++ b/subr/ex_pkg_dispatch.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 #
@@ -129,7 +129,7 @@ exp_pkg_dispatch_package() {
 			printf \"fail %s %s\n\" \"${_group_name}\" \"${_pkg_name}\" >&3;	\
 			pkill -U "${$}";							\
 		      fi;" EXIT HUP INT TERM USR1 USR2;
-		set +o errexit -o noglob; BUILD_IS_PARENT=0; rtl_log_set_fname ""; rtl_log_set_no_attr 1;
+		set +o errexit -o noglob -o nounset; BUILD_IS_PARENT=0; rtl_log_set_fname ""; rtl_log_set_no_attr 1;
 		if ex_pkg_env "${_build_steps_default}" "${_build_vars_default}"		\
 				"${_group_name}" 0 "${_pkg_name}" "${_restart_at}" "${_workdir}"; then
 			ex_pkg_exec "${_dispatch_fn}" "${_group_name}" "${_pkg_name}" "${_restart_at}";
diff --git a/subr/ex_pkg_env.subr b/subr/ex_pkg_env.subr
index 48b57535..ca701296 100644
--- a/subr/ex_pkg_env.subr
+++ b/subr/ex_pkg_env.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 #
@@ -15,17 +15,23 @@ exp_pkg_env_defaults() {
 	: ${PKG_NAME:="${_pkg_name}"};
 	: ${MIDIPIX_BUILD_PWD:="$(pwd)"};
 	: ${PKG_BASE_DIR:="${_workdir}/${_pkg_name}-${PKG_BUILD_TYPE}-${PKG_TARGET}"};
-	: ${PKG_FNAME:="${PKG_URL##*/}"};
-	: ${PKG_BUILD_STEPS:="$(rtl_lfilter "${_build_steps_default}" "${PKG_BUILD_STEPS_DISABLE}")"};
-	if [ -z "${PKG_SUBDIR}" ]; then
-		if [ -n "${PKG_URLS_GIT}" ]; then
+	if [ -n "${PKG_BUILD_STEPS_DISABLE:-}" ]; then
+		: ${PKG_BUILD_STEPS:="$(rtl_lfilter "${_build_steps_default}" "${PKG_BUILD_STEPS_DISABLE:-}")"};
+	else
+		: ${PKG_BUILD_STEPS:="${_build_steps_default}"};
+	fi;
+	if [ -n "${PKG_URL:-}" ]; then
+		: ${PKG_FNAME:="${PKG_URL##*/}"};
+	fi;
+	if [ -z "${PKG_SUBDIR:-}" ]; then
+		if [ -n "${PKG_URLS_GIT:-}" ]; then
 			PKG_SUBDIR="${PKG_URLS_GIT%%=*}";
-		else case "${PKG_FNAME}" in
+		else case "${PKG_FNAME:-}" in
 		*.t*)	PKG_SUBDIR="${PKG_FNAME%%.t*}"; ;;
 		*)	PKG_SUBDIR="${_pkg_name}"; ;;
 		esac; fi;
 	fi;
-	if [ -z "${PKG_BUILD_DIR}" ]; then
+	if [ -z "${PKG_BUILD_DIR:-}" ]; then
 		case "${PKG_IN_TREE:-0}" in
 		0) PKG_BUILD_DIR="obj"; ;;
 		1) PKG_BUILD_DIR="${PKG_SUBDIR}"; ;;
@@ -57,7 +63,7 @@ exp_pkg_env_set() {
 	rtl_set_vars _vars_set INHERIT_FROM "PKG_${_pkg_name}";
 	_var_prefixes="$(rtl_toupper "DEFAULT DEFAULT_${PKG_BUILD_TYPE} ${_group_name}")";
 	for _vname in $(rtl_lfilter "${_build_vars_default}" BUILD_TYPE); do
-		if [ -n "${PKG_INHERIT_FROM}" ]; then
+		if [ -n "${PKG_INHERIT_FROM:-}" ]; then
 			rtl_set_vars _vars_set "${_vname}"			\
 				"$(rtl_lconcat "${_var_prefixes}"		\
 				"$(rtl_toupper "PKG_${PKG_INHERIT_FROM} PKG_${_pkg_name}")")"
@@ -67,7 +73,7 @@ exp_pkg_env_set() {
 				"$(rtl_toupper "PKG_${_pkg_name}")")";
 		fi;
 	done;
-	IFS0="${IFS}"; IFS=":"; for _vname in ${PKG_ENV_VARS_EXTRA}; do
+	IFS0="${IFS}"; IFS=":"; for _vname in ${PKG_ENV_VARS_EXTRA:-}; do
 		export "${_vname}";
 	done; IFS="${IFS0}";
 	if [ "${_nounset:-0}" -eq 0 ]; then
diff --git a/subr/ex_pkg_exec.subr b/subr/ex_pkg_exec.subr
index 4519ce25..d21289b7 100644
--- a/subr/ex_pkg_exec.subr
+++ b/subr/ex_pkg_exec.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 exp_pkg_exec_filter_vars_fn() {
@@ -27,9 +27,9 @@ exp_pkg_exec_filter_vars_fn() {
 #
 exp_pkg_exec_pre() {
 	local _group_name="${1}" _pkg_name="${2}" _restart_at="${3}";
-	if [ -z "${PKG_URL}" ]\
-	&& [ -z "${PKG_URLS_GIT}" ]\
-	&& [ -z "${PKG_VERSION}" ]\
+	if [ -z "${PKG_URL:-}" ]\
+	&& [ -z "${PKG_URLS_GIT:-}" ]\
+	&& [ -z "${PKG_VERSION:-}" ]\
 	&& ! rtl_test_cmd "pkg_${_pkg_name}_all"; then
 		"${_dispatch_fn}" missing_pkg "${_group_name}" "${_pkg_name}";
 		return 1;
@@ -94,7 +94,7 @@ ex_pkg_exec() {
 			"pkg_${_pkg_name}_all" "${_restart_at}"; _rc="${?}";
 		else	set -- ${PKG_BUILD_STEPS};
 			while [ ${#} -gt 0 ]; do
-				_step="${1}"; _step_next="${2}"; shift;
+				_step="${1}"; _step_next="${2:-}"; shift;
 				if [ "${ARG_DUMP_IN}" = "${_step}" ]; then
 					printf "" > "${BUILD_WORKDIR}/${_pkg_name}.dump";
 					rtl_filter_vars exp_pkg_exec_filter_vars_fn >> "${BUILD_WORKDIR}/${_pkg_name}.dump";
diff --git a/subr/pkg_build.subr b/subr/pkg_build.subr
index 2433ea81..d1808213 100644
--- a/subr/pkg_build.subr
+++ b/subr/pkg_build.subr
@@ -1,27 +1,35 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 pkg_build() {
-	local _no_autoconf="";
-	if [ ! -x "${PKG_CONFIGURE}" ]; then
+	local _libtool="" _no_autoconf="";
+	case "${PKG_LIBTOOL:-}" in
+	"")	_libtool=""; ;;
+	none)	_libtool=""; ;;
+	*)	_libtool="${PKG_LIBTOOL}"; ;;
+	esac;
+	if [ ! -x "${PKG_CONFIGURE:-}" ]; then
 		_no_autoconf=1;
 	fi;
 	# N.B.	We only specify CC= here if the current package does not use GNU
 	#	autoconf as it often abuses it by appending -std={gnu99,...} to it
 	#	instead of amending CFLAGS.
-	rtl_run_cmd_unsplit make						\
-		${PKG_MAKEFLAGS_BUILD}						\
-		${PKG_MAKEFLAGS_BUILD_EXTRA}					\
-		"AR=${PKG_AR}" "${_no_autoconf:+CC=${PKG_CC}}"			\
-		"RANLIB=${PKG_RANLIB}"						\
-		"${PKG_CFLAGS_BUILD:+CFLAGS=${PKG_CFLAGS_BUILD}}"		\
-		"${PKG_CFLAGS_BUILD_EXTRA:+CFLAGS+=${PKG_CFLAGS_BUILD_EXTRA}}"	\
-		"${PKG_LDFLAGS_BUILD:+LDFLAGS=${PKG_LDFLAGS_BUILD}}"		\
-		"${PKG_LDFLAGS_BUILD_EXTRA:+LDFLAGS+=${PKG_LDFLAGS_BUILD_EXTRA}}"\
-		"${PKG_PKG_CONFIG:+PKG_CONFIG=${PKG_PKG_CONFIG}}"		\
-		"${PKG_PKG_CONFIG_PATH:+PKG_CONFIG_PATH=${PKG_PKG_CONFIG_PATH}}"\
-		"LIBTOOL=${PKG_LIBTOOL:-slibtool}";
+	rtl_run_cmd_unsplit make							\
+		${PKG_MAKEFLAGS_BUILD:-}						\
+		${PKG_MAKEFLAGS_BUILD_EXTRA:-}						\
+		"AR=${PKG_AR}" "${_no_autoconf:+CC=${PKG_CC}}" "RANLIB=${PKG_RANLIB}"	\
+		"${PKG_CFLAGS_BUILD:+CFLAGS=${PKG_CFLAGS_BUILD}}"			\
+		"${PKG_CFLAGS_BUILD_EXTRA:+CFLAGS+=${PKG_CFLAGS_BUILD_EXTRA}}"		\
+		"${PKG_CPPFLAGS_BUILD:+CPPFLAGS=${PKG_CPPFLAGS_BUILD}}"			\
+		"${PKG_CPPFLAGS_BUILD_EXTRA:+CPPFLAGS+=${PKG_CPPFLAGS_BUILD_EXTRA}}"	\
+		"${PKG_CXXFLAGS_BUILD:+CXXFLAGS=${PKG_CXXFLAGS_BUILD}}"			\
+		"${PKG_CXXFLAGS_BUILD_EXTRA:+CXXFLAGS+=${PKG_CXXFLAGS_BUILD_EXTRA}}"	\
+		"${PKG_LDFLAGS_BUILD:+LDFLAGS=${PKG_LDFLAGS_BUILD}}"			\
+		"${PKG_LDFLAGS_BUILD_EXTRA:+LDFLAGS+=${PKG_LDFLAGS_BUILD_EXTRA}}"	\
+		"${PKG_PKG_CONFIG:+PKG_CONFIG=${PKG_PKG_CONFIG}}"			\
+		"${PKG_PKG_CONFIG_PATH:+PKG_CONFIG_PATH=${PKG_PKG_CONFIG_PATH}}"	\
+		${_libtool:+"LIBTOOL=${_libtool}"};
 };
 
 # vim:filetype=sh
diff --git a/subr/pkg_clean.subr b/subr/pkg_clean.subr
index a7df7920..39b0ead5 100644
--- a/subr/pkg_clean.subr
+++ b/subr/pkg_clean.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 pkg_clean() {
diff --git a/subr/pkg_configure.subr b/subr/pkg_configure.subr
index 974e708f..f2b64f92 100644
--- a/subr/pkg_configure.subr
+++ b/subr/pkg_configure.subr
@@ -1,20 +1,27 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 pkg_configure() {
 	local _rc=0;
-	if [ -x "${PKG_CONFIGURE}" ]; then
-		rtl_export_vars PKG_CONFIG "${PKG_PKG_CONFIG}" PKG_CONFIG_PATH "${PKG_PKG_CONFIG_PATH}" PYTHON "${PKG_PYTHON}";
+	if [ -x "${PKG_CONFIGURE:-}" ]; then
+		rtl_export_vars	\
+			PKG_CONFIG "${PKG_PKG_CONFIG:-}"								\
+			PKG_CONFIG_PATH "${PKG_PKG_CONFIG_PATH:-}"							\
+			PYTHON "${PKG_PYTHON:-}";
 		AR="${PKG_AR}"												\
 		CC="${PKG_CC}"												\
 		RANLIB="${PKG_RANLIB}"											\
-		CFLAGS="${PKG_CFLAGS_CONFIGURE}${PKG_CFLAGS_CONFIGURE_EXTRA:+ ${PKG_CFLAGS_CONFIGURE_EXTRA}}"		\
-		CPPFLAGS="${PKG_CFLAGS_CONFIGURE}${PKG_CFLAGS_CONFIGURE_EXTRA:+ ${PKG_CFLAGS_CONFIGURE_EXTRA}}"		\
-		CXXFLAGS="${PKG_CXXFLAGS_CONFIGURE}${PKG_CXXFLAGS_CONFIGURE_EXTRA:+ ${PKG_CXXFLAGS_CONFIGURE_EXTRA}}"	\
-		LDFLAGS="${PKG_LDFLAGS_CONFIGURE}${PKG_LDFLAGS_CONFIGURE_EXTRA:+ ${PKG_LDFLAGS_CONFIGURE_EXTRA}}"	\
-		"${PKG_CONFIGURE}" ${PKG_CONFIGURE_ARGS} ${PKG_CONFIGURE_ARGS_EXTRA} ${PKG_CONFIGURE_ARGS_EXTRA_DEBUG}; _rc="${?}"
-		rtl_export_vars -u PKG_CONFIG "${PKG_PKG_CONFIG}" PKG_CONFIG_PATH "${PKG_PKG_CONFIG_PATH}" PYTHON "${PKG_PYTHON}";
+		CFLAGS="${PKG_CFLAGS_CONFIGURE:-}${PKG_CFLAGS_CONFIGURE_EXTRA:+ ${PKG_CFLAGS_CONFIGURE_EXTRA}}"		\
+		CPPFLAGS="${PKG_CFLAGS_CONFIGURE:-}${PKG_CFLAGS_CONFIGURE_EXTRA:+ ${PKG_CFLAGS_CONFIGURE_EXTRA}}"	\
+		CXXFLAGS="${PKG_CXXFLAGS_CONFIGURE:-}${PKG_CXXFLAGS_CONFIGURE_EXTRA:+ ${PKG_CXXFLAGS_CONFIGURE_EXTRA}}"	\
+		LDFLAGS="${PKG_LDFLAGS_CONFIGURE:-}${PKG_LDFLAGS_CONFIGURE_EXTRA:+ ${PKG_LDFLAGS_CONFIGURE_EXTRA}}"	\
+		"${PKG_CONFIGURE}" ${PKG_CONFIGURE_ARGS:-} ${PKG_CONFIGURE_ARGS_EXTRA:-} ${PKG_CONFIGURE_ARGS_EXTRA_DEBUG:-};
+		_rc="${?}"
+		rtl_export_vars	-u \
+			PKG_CONFIG "${PKG_PKG_CONFIG:-}"								\
+			PKG_CONFIG_PATH "${PKG_PKG_CONFIG_PATH:-}"							\
+			PYTHON "${PKG_PYTHON:-}";
 		return "${_rc}";
 	fi;
 };
diff --git a/subr/pkg_configure_autotools.subr b/subr/pkg_configure_autotools.subr
index 32daedc1..86a9dd39 100644
--- a/subr/pkg_configure_autotools.subr
+++ b/subr/pkg_configure_autotools.subr
@@ -1,12 +1,12 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 pkg_configure_autotools() {
 	local _config_cache="" _fname="" _subdir_tgt="";
 	if rtl_exists_any "${PKG_BASE_DIR}/${PKG_SUBDIR}"							\
 			"config.guess" "configure.ac" "configure.in" "configure";
-	then	rtl_export_vars PKG_CONFIG "${PKG_PKG_CONFIG}" PKG_CONFIG_PATH "${PKG_PKG_CONFIG_PATH}";
+	then	rtl_export_vars PKG_CONFIG "${PKG_PKG_CONFIG:-}" PKG_CONFIG_PATH "${PKG_PKG_CONFIG_PATH:-}";
 		if [ "${PKG_FORCE_AUTORECONF:-0}" -eq 1 ]\
 		&& ! (cd "${PKG_BASE_DIR}/${PKG_SUBDIR}" && autoreconf -fiv); then
 			return 1;
@@ -50,10 +50,11 @@ pkg_configure_autotools() {
 			if ! rtl_fileop touch "${PKG_BUILD_DIR}/config.cache"; then
 				return 1;
 			else	for _config_cache in \
-						"${PKG_CONFIG_CACHE}"						\
-						"${PKG_CONFIG_CACHE_LOCAL}"					\
-						"${PKG_CONFIG_CACHE_EXTRA}";
-				do	if ! printf "%s" "${_config_cache}"					|\
+						"${PKG_CONFIG_CACHE:-}"						\
+						"${PKG_CONFIG_CACHE_LOCAL:-}"					\
+						"${PKG_CONFIG_CACHE_EXTRA:-}";
+				do	if [ -n "${_config_cache}" ]\
+					&& ! printf "%s\n" "${_config_cache}"					|\
 							tr " " "\n" >> "${PKG_BUILD_DIR}/config.cache"; then
 						return 1;
 					fi;
@@ -63,7 +64,7 @@ pkg_configure_autotools() {
 				fi;
 			fi;
 		fi;
-		rtl_export_vars -u PKG_CONFIG "${PKG_PKG_CONFIG}" PKG_CONFIG_PATH "${PKG_PKG_CONFIG_PATH}";
+		rtl_export_vars -u PKG_CONFIG "${PKG_PKG_CONFIG:-}" PKG_CONFIG_PATH "${PKG_PKG_CONFIG_PATH:-}";
 	fi;
 };
 
diff --git a/subr/pkg_configure_patch.subr b/subr/pkg_configure_patch.subr
index 88f3f3d1..6b4bcdd3 100644
--- a/subr/pkg_configure_patch.subr
+++ b/subr/pkg_configure_patch.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 pkg_configure_patch() {
@@ -10,7 +10,7 @@ pkg_configure_patch() {
 			"${_patch_dir}/${_pkg_name}/"*.patch				\
 			"${_patch_dir}/${_pkg_name_full}.local.patch"			\
 			"${_patch_dir}/${_pkg_name_full}.local@${BUILD_HNAME}.patch"	\
-			${PKG_PATCHES_EXTRA}; do
+			${PKG_PATCHES_EXTRA:-}; do
 		if [ -r "${_patch_fname}" ]\
 		&& ! rtl_lmatch "${_patches_done}" "${_patch_fname}"; then
 			if ! patch -b -d "${PKG_BASE_DIR}/${PKG_SUBDIR}" -p1 < "${_patch_fname}"; then
diff --git a/subr/pkg_configure_patch_pre.subr b/subr/pkg_configure_patch_pre.subr
index 434b1cf7..c78b65b2 100644
--- a/subr/pkg_configure_patch_pre.subr
+++ b/subr/pkg_configure_patch_pre.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 pkgp_configure_patch_pre() {
@@ -15,8 +15,11 @@ pkgp_configure_patch_pre() {
 };
 
 pkgp_configure_patch_pre_chainport() {
-	local	_chainport_patch_fname="${BUILD_WORKDIR}/chainport/patches/${PKG_NAME%%_*}/${PKG_NAME%%_*}-${PKG_VERSION}.midipix.patch"\
-		_chainport_patch_dname="${PKG_BASE_DIR}/${PKG_SUBDIR}/patches/${PKG_NAME%%_*}" _oldpwd="";
+	local _chainport_patch_dname="" _chainport_patch_fname="" _oldpwd="";
+	_chainport_patch_dname="${PKG_BASE_DIR}/${PKG_SUBDIR}/patches/${PKG_NAME%%_*}";
+	if [ -n "${PKG_VERSION:-}" ]; then
+		_chainport_patch_fname="${BUILD_WORKDIR}/chainport/patches/${PKG_NAME%%_*}/${PKG_NAME%%_*}-${PKG_VERSION}.midipix.patch";
+	fi;
 	if [ -e "${_chainport_patch_fname}" ]; then
 		if ! rtl_fileop mkdir "${_chainport_patch_dname}"\
 		|| ! rtl_fileop cp "${_chainport_patch_fname}" "${_chainport_patch_dname}"; then
diff --git a/subr/pkg_fetch_download.subr b/subr/pkg_fetch_download.subr
index 126675ad..57cad8be 100644
--- a/subr/pkg_fetch_download.subr
+++ b/subr/pkg_fetch_download.subr
@@ -1,14 +1,14 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 pkg_fetch_download() {
-	if [ -n "${PKG_URL}" ]; then
+	if [ -n "${PKG_URL:-}" ]; then
 		if ! rtl_fetch_url_wget "${PKG_URL}" "${PKG_SHA256SUM}" "${PKG_FNAME}"; then
 			return 1;
 		fi;
 	fi;
-	if [ -n "${PKG_URLS_GIT}" ]; then
+	if [ -n "${PKG_URLS_GIT:-}" ]; then
 		if ! rtl_fetch_urls_git "${PKG_BASE_DIR}" ${PKG_URLS_GIT}; then
 			return 1;
 		fi;
diff --git a/subr/pkg_fetch_extract.subr b/subr/pkg_fetch_extract.subr
index 8a9d8319..e91e7a6a 100644
--- a/subr/pkg_fetch_extract.subr
+++ b/subr/pkg_fetch_extract.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 pkgp_fetch_extract_type() {
@@ -12,7 +12,7 @@ pkgp_fetch_extract_type() {
 };
 
 pkg_fetch_extract() {
-	if [ -n "${PKG_URL}" ]; then
+	if [ -n "${PKG_URL:-}" ]; then
 		_oldpwd="${PWD}";
 		if ! rtl_fileop cd "${PKG_BASE_DIR}"\
 		|| ! rtl_fileop rm "${PKG_BASE_DIR}/${PKG_SUBDIR}"; then
diff --git a/subr/pkg_install.subr b/subr/pkg_install.subr
index 4cefa2d1..8a033572 100644
--- a/subr/pkg_install.subr
+++ b/subr/pkg_install.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 pkg_install() {
@@ -44,7 +44,7 @@ pkg_install() {
 				return 1;
 			else
 				_pkglist_name="${PKG_BASE_DIR##*/}"; _pkglist_name="${_pkglist_name%%-*}";
-				if ! printf "%s" "${_pkglist_name}" >> "${PREFIX}/pkglist.${PKG_BUILD_TYPE}"; then
+				if ! printf "%s\n" "${_pkglist_name}" >> "${PREFIX}/pkglist.${PKG_BUILD_TYPE}"; then
 					return 1;
 				fi;
 			fi;
diff --git a/subr/pkg_install_files.subr b/subr/pkg_install_files.subr
index 2c6703fb..76460da3 100644
--- a/subr/pkg_install_files.subr
+++ b/subr/pkg_install_files.subr
@@ -1,9 +1,9 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 pkgp_install_files() {
-	if [ -n "${PKG_INSTALL_FILES}" ]; then
+	if [ -n "${PKG_INSTALL_FILES:-}" ]; then
 		if ! rtl_install -v "${PKG_DESTDIR}" ${PKG_INSTALL_FILES}; then
 			return 1;
 		fi;
diff --git a/subr/pkg_install_libs.subr b/subr/pkg_install_libs.subr
index 76c7bfdb..a13105ab 100644
--- a/subr/pkg_install_libs.subr
+++ b/subr/pkg_install_libs.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 pkgp_install_libs_purge_la() {
diff --git a/subr/pkg_install_make.subr b/subr/pkg_install_make.subr
index 4babac8f..a5e58f60 100644
--- a/subr/pkg_install_make.subr
+++ b/subr/pkg_install_make.subr
@@ -1,16 +1,22 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 pkg_install_make() {
-	rtl_run_cmd_unsplit make							\
-		${PKG_MAKEFLAGS_INSTALL}						\
-		${PKG_MAKEFLAGS_INSTALL_EXTRA}						\
-		AR=${PKG_AR} CC=${PKG_CC} RANLIB=${PKG_RANLIB}				\
-		"${PKG_RANLIB_INSTALL:+RANLIB=${PKG_RANLIB_INSTALL}}"			\
-		"LIBTOOL=${PKG_LIBTOOL:-slibtool}"					\
-		"${PKG_MAKE_INSTALL_VNAME:-DESTDIR}=${PKG_DESTDIR}/"			\
-		${PKG_INSTALL_TARGET:=install};
+	local _libtool="";
+	case "${PKG_LIBTOOL:-}" in
+	"")	_libtool=""; ;;
+	none)	_libtool=""; ;;
+	*)	_libtool="${PKG_LIBTOOL}"; ;;
+	esac;
+	rtl_run_cmd_unsplit make					\
+		${PKG_MAKEFLAGS_INSTALL:-}				\
+		${PKG_MAKEFLAGS_INSTALL_EXTRA:-}			\
+		AR="${PKG_AR}" CC="${PKG_CC}" RANLIB="${PKG_RANLIB}"	\
+		"${PKG_RANLIB_INSTALL:+RANLIB=${PKG_RANLIB_INSTALL}}"	\
+		${_libtool:+"LIBTOOL=${_libtool}"}			\
+		"${PKG_MAKE_INSTALL_VNAME:-DESTDIR}=${PKG_DESTDIR}/"	\
+		${PKG_INSTALL_TARGET:-install};
 };
 
 # vim:filetype=sh
diff --git a/subr/pkg_install_rpm.subr b/subr/pkg_install_rpm.subr
index 6cc373ff..c0ba3e5e 100644
--- a/subr/pkg_install_rpm.subr
+++ b/subr/pkg_install_rpm.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 pkg_install_rpm() {
@@ -7,9 +7,9 @@ pkg_install_rpm() {
 	if rtl_lmatch "${ARG_DIST}" "rpm" ","\
 	&& [ "${PKG_RPM_DISABLE:-0}" -eq 0 ]\
 	&& [ -x "$(which rpmbuild 2>/dev/null)" ]; then
-		if [ -n "${PKG_URL}" ]; then
+		if [ -n "${PKG_URL:-}" ]; then
 			_pkg_url="${PKG_URL}"; _pkg_version_full="${PKG_VERSION}"; _pkg_version_rpm="${PKG_VERSION%%-*}";
-		elif [ -n "${PKG_URLS_GIT}" ]; then
+		elif [ -n "${PKG_URLS_GIT:-}" ]; then
 			_pkg_version_rpm="$(cd "${PKG_BASE_DIR}/${PKG_SUBDIR}" && git rev-parse HEAD)";
 			_pkg_version_full="${_pkg_version_rpm} ($(cd "${PKG_BASE_DIR}/${PKG_SUBDIR}" && git rev-parse --abbrev-ref HEAD))";
 			_pkg_url="${PKG_URLS_GIT%% *}"; _pkg_url="${_pkg_url##*=}"; _pkg_url="${_pkg_url%%@*}";
diff --git a/subr/pkg_install_subdirs.subr b/subr/pkg_install_subdirs.subr
index 8e6e0429..c9e4cd39 100644
--- a/subr/pkg_install_subdirs.subr
+++ b/subr/pkg_install_subdirs.subr
@@ -1,12 +1,12 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 pkg_install_subdirs() {
 	local _spec="";
 	for _spec in \
-			"${PKG_INSTALL_FILES_DESTDIR}"		\
-			"${PKG_INSTALL_FILES_DESTDIR_EXTRA}"; do
+			"${PKG_INSTALL_FILES_DESTDIR:-}"	\
+			"${PKG_INSTALL_FILES_DESTDIR_EXTRA:-}"; do
 		if ! rtl_install "${PKG_DESTDIR}" ${_spec}; then
 			return 1;
 		fi;
diff --git a/subr/pkgtool_init.subr b/subr/pkgtool_init.subr
index f92572fb..309dc612 100644
--- a/subr/pkgtool_init.subr
+++ b/subr/pkgtool_init.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 pkgtoolp_init_args() {
diff --git a/subr/rtl.subr b/subr/rtl.subr
index f029a8e1..ef9d63ea 100644
--- a/subr/rtl.subr
+++ b/subr/rtl.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 rtl_basename() { local _fname="${1##*/}"; printf "%s" "${_fname}"; };
diff --git a/subr/rtl_complex.subr b/subr/rtl_complex.subr
index 0e39178d..2ce5dd16 100644
--- a/subr/rtl_complex.subr
+++ b/subr/rtl_complex.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 rtl_check_path_vars() {
@@ -117,7 +117,7 @@ rtl_get_var_unsafe() {
 	else
 		_vname="${1}";
 	fi;
-	eval echo \${${_vname}};
+	eval echo \${${_vname}} 2>/dev/null;
 };
 
 rtl_get_vars_fast() {
diff --git a/subr/rtl_fetch.subr b/subr/rtl_fetch.subr
index e93d69eb..1fd72e99 100644
--- a/subr/rtl_fetch.subr
+++ b/subr/rtl_fetch.subr
@@ -1,11 +1,12 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 exp_rtl_fetch_url_git() {
 	local _tgtdir="${1}" _subdir="${2}" _url="${3}" _branch="${4}"	\
 		_oldpwd="";
-	(set -o errexit -o noglob; trap "rm -f \"${BUILD_DLCACHEDIR}/${_subdir%%[/]}.fetching\"" EXIT;
+	(set -o errexit -o noglob -o nounset;
+	trap "rm -f \"${BUILD_DLCACHEDIR}/${_subdir%%[/]}.fetching\"" EXIT;
 	while true; do
 		if flock -E 622 -w 3600 4; then
 			break;
@@ -67,7 +68,8 @@ rtl_fetch_url_wget() {
 		_target_fname="$(rtl_basename "${_url}")";
 	fi;
 	_url_dst="${BUILD_DLCACHEDIR}/${_target_fname}";
-	(set -o errexit -o noglob; trap "_rc=\"\${?}\" ;rm -f \"${_url_dst}.fetching\"; exit \"\${_rc}\";" EXIT;
+	(set -o errexit -o noglob -o nounset;
+	trap "_rc=\"\${?}\" ;rm -f \"${_url_dst}.fetching\"; exit \"\${_rc}\";" EXIT;
 	while true; do
 		if flock -E 622 -w 3600 4; then
 			break;
diff --git a/subr/rtl_fileop.subr b/subr/rtl_fileop.subr
index fd45f67f..64538c59 100644
--- a/subr/rtl_fileop.subr
+++ b/subr/rtl_fileop.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 #
@@ -28,28 +28,28 @@ rtl_fileop() {
 	case "${_op}" in
 	cd)	if [ \( -z "${1}" \) -o ! \( -L "${1}" -o -e "${1}" \) ]; then
 			rtl_log_msg fatalexit "Invalid or non-existent directory \`%s'." "${1}";
-		elif rtlp_fileop_check "${PREFIX}" "${1}"; then
+		elif rtlp_fileop_check "${PREFIX:-}" "${1}"; then
 			rtlp_fileop_log "Changing working directory to \`${1}'.";
 			cd -- "${1}"; _rc="${?}";
 		fi; ;;
 	chmod)	if [ "${#}" -lt 2 ]; then
 			rtl_log_msg fatalexit "Missing parameters (in: chmod %s.)" "${*}";
 		elif _mode="${1}" && shift\
-		&&   rtlp_fileop_check "${PREFIX}" "${*}"; then
+		&&   rtlp_fileop_check "${PREFIX:-}" "${*}"; then
 			rtlp_fileop_log "Changing file mode bits of \`${*}' to \`${_mode}'.";
 			chmod -- "${_mode}" "${@}"; _rc="${?}";
 		fi; ;;
 	chown)	if [ "${#}" -lt 2 ]; then
 			rtl_log_msg fatalexit "Missing parameters (in: chown %s.)" "${*}";
 		elif _owner="${1}" && shift\
-		&&   rtlp_fileop_check "${PREFIX}" "${*}"; then
+		&&   rtlp_fileop_check "${PREFIX:-}" "${*}"; then
 			rtlp_fileop_log "Changing file owner of \`${*}' to \`${_owner}'.";
 			chown -- "${_owner}" "${@}"; _rc="${?}";
 		fi; ;;
 	cp_follow)
 		if [ "${#}" -lt 2 ]; then
 			rtl_log_msg fatalexit "Missing parameters (in: cp_follow %s}.)" "${*}";
-		elif rtlp_fileop_check "${PREFIX}" "${*}"; then
+		elif rtlp_fileop_check "${PREFIX:-}" "${*}"; then
 			_src="${*}"; _src="${_src% *}";
 			_dst="${*}"; _dst="${_dst##* }";
 			rtlp_fileop_log "Copying \`${_src}' into \`${_dst}' w/ -pLR.";
@@ -57,7 +57,7 @@ rtl_fileop() {
 		fi; ;;
 	cp)	if [ "${#}" -lt 2 ]; then
 			rtl_log_msg fatalexit "Missing parameters (in: cp %s.)" "${*}";
-		elif rtlp_fileop_check "${PREFIX}" "${*}"; then
+		elif rtlp_fileop_check "${PREFIX:-}" "${*}"; then
 			_src="${*}"; _src="${_src% *}";
 			_dst="${*}"; _dst="${_dst##* }";
 			rtlp_fileop_log "Copying \`${_src}' into \`${_dst}' w/ -pPR.";
@@ -69,7 +69,7 @@ rtl_fileop() {
 		else	_dst="$(while [ ""${#}"" -gt 2 ]; do shift; done; printf "%s" "${2}")";
 			_install_args="$(while [ ""${#}"" -gt 2 ]; do printf "%s" "${1}"; shift; done)";
 			_src="$(while [ ""${#}"" -gt 2 ]; do shift; done; printf "%s" "${1}")";
-			if rtlp_fileop_check "${PREFIX}" "${_dst}" "${_src}"; then
+			if rtlp_fileop_check "${PREFIX:-}" "${_dst}" "${_src}"; then
 				rtlp_fileop_log "Installing \`${_src}' into \`${_dst}' w/ ${_install_args}.";
 				install "${@}"; _rc="${?}";
 			fi;
@@ -77,7 +77,7 @@ rtl_fileop() {
 	ln_symbolic)
 		if [ \( -z "${1}" \) -o \( -z "${2}" \) ]; then
 			rtl_log_msg fatalexit "Missing parameters (in: ln_symbolic %s.)" "${*}";
-		elif rtlp_fileop_check "${PREFIX}" "${2}"; then
+		elif rtlp_fileop_check "${PREFIX:-}" "${2}"; then
 			if rtl_fileop test "${2}"; then
 				rtl_fileop rm "${2}";
 			fi;
@@ -88,7 +88,7 @@ rtl_fileop() {
 		fi; ;;
 	mv)	if [ \( -z "${1}" \) -o \( -z "${2}" \) ]; then
 			rtl_log_msg fatalexit "Missing parameters (in: mv %s.)" "${*}";
-		elif rtlp_fileop_check "${PREFIX}" "${1}" "${2}"; then
+		elif rtlp_fileop_check "${PREFIX:-}" "${1}" "${2}"; then
 			rtlp_fileop_log "Moving \`${1}' to \`${2}' w/ -fs";
 			mv -f -- "${1}" "${2}"; _rc="${?}";
 		fi; ;;
@@ -98,36 +98,36 @@ rtl_fileop() {
 				rtl_log_msg fatalexit "Missing parameters (in: %s %s.)" "${_op}" "${*}";
 			elif [ "${_op}" = mkdir ]\
 			&& [ ! -d "${1}" ]\
-			&& rtlp_fileop_check "${PREFIX}" "${1}"; then
+			&& rtlp_fileop_check "${PREFIX:-}" "${1}"; then
 				if rtl_fileop test "${1}"; then
 					rtl_fileop rm "${1}";
 				fi;
 				rtlp_fileop_log "Making directory \`${1}'.";
 				mkdir -p -- "${1}"; _rc="${?}";
 			elif [ "${_op}" = mkfifo ]\
-			&& rtlp_fileop_check "${PREFIX}" "${1}"; then
+			&& rtlp_fileop_check "${PREFIX:-}" "${1}"; then
 				if rtl_fileop test "${1}"; then
 					rtl_fileop rm "${1}";
 				fi;
 				rtlp_fileop_log "Creating FIFO \`${1}'.";
-				rtlp_fileop_check "${PREFIX}" "${1}";
+				rtlp_fileop_check "${PREFIX:-}" "${1}";
 				mkfifo -- "${1}"; _rc="${?}";
 			elif [ "${_op}" = rm ]\
 			&& rtl_fileop test "${1}"\
-			&& rtlp_fileop_check "${PREFIX}" "${1}"; then
+			&& rtlp_fileop_check "${PREFIX:-}" "${1}"; then
 				rtlp_fileop_log "Removing directory or file \`${1}'.";
 				rm -rf -- "${1}"; _rc="${?}";
 			elif [ "${_op}" = source_opt ]\
 			&& rtl_fileop test "${1}"\
-			&& rtlp_fileop_check "${PREFIX}" "${1}"; then
+			&& rtlp_fileop_check "${PREFIX:-}" "${1}"; then
 				rtlp_fileop_log "Sourcing file \`${1}'.";
 				. "${1}"; _rc="${?}";
 			elif [ "${_op}" = test ]\
-			&& rtlp_fileop_check "${PREFIX}" "${1}"\
+			&& rtlp_fileop_check "${PREFIX:-}" "${1}"\
 			&& ! [ \( -L "${1}" \) -o \( -e "${1}" \) ]; then
 				return 1;
 			elif [ "${_op}" = touch ]\
-			&& rtlp_fileop_check "${PREFIX}" "${1}"; then
+			&& rtlp_fileop_check "${PREFIX:-}" "${1}"; then
 				rtlp_fileop_log "Touching file \`${1}'.";
 				touch -- "${1}"; _rc="${?}";
 			fi; shift;
diff --git a/subr/rtl_install.subr b/subr/rtl_install.subr
index a1c70a01..b57c68f2 100644
--- a/subr/rtl_install.subr
+++ b/subr/rtl_install.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 rtl_install() {
diff --git a/subr/rtl_list.subr b/subr/rtl_list.subr
index b1105bab..c4c563bf 100644
--- a/subr/rtl_list.subr
+++ b/subr/rtl_list.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 rtl_lconcat() {
@@ -45,7 +45,7 @@ rtl_llift() {
 };
 
 rtl_lmatch() {
-	local _list="${1}" _item="${2}" _sep="${3}";
+	local _list="${1}" _item="${2}" _sep="${3:- }";
 	[ -n "$(rtl_lsearch "${_list}" "${_item}" "${_sep}")" ];
 };
 
diff --git a/subr/rtl_log.subr b/subr/rtl_log.subr
index 860ccf03..b91d1374 100644
--- a/subr/rtl_log.subr
+++ b/subr/rtl_log.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 #
diff --git a/subr/rtl_state.subr b/subr/rtl_state.subr
index 1ee8258b..6d539563 100644
--- a/subr/rtl_state.subr
+++ b/subr/rtl_state.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 rtl_state_clear() {
@@ -25,8 +25,7 @@ rtl_state_set() {
 };
 
 rtl_state_test() {
-	local _workdir="${1}" _pkg_name="${2}" _build_step="${3}"	\
-		_restart_at="${4}" _done_fname="";
+	local _workdir="${1}" _pkg_name="${2}" _build_step="${3}" _restart_at="${4:-}" _done_fname="";
 	_done_fname="${_workdir}/.${_pkg_name}.${_build_step}";
 	if [ -z "${_restart_at}" ]; then
 		rtl_fileop test "${_done_fname}";
diff --git a/subr/rtl_string.subr b/subr/rtl_string.subr
index 2dd9e27a..e642bebe 100644
--- a/subr/rtl_string.subr
+++ b/subr/rtl_string.subr
@@ -1,5 +1,5 @@
 #
-# set +o errexit -o noglob is assumed.
+# set +o errexit -o noglob -o nounset is assumed.
 #
 
 rtl_isnumber() {