etc/build.usage: adds -P [jobs].

subr/build_args.subr: adds `optarg' arg type & ARG_PARALLEL:optarg:-P:auto.
subr/build_init.subr: default ${ARG_PARALLEL} ([jobs]) to ${DEFAULT_BUILD_CPUS}.
subr/ex_pkg_dispatch.subr: honour ${ARG_PARALLEL}, defaulting to no parallelisation.

4 files changed, 42 insertions, 23 deletions

diff --git a/etc/build.usage b/etc/build.usage
index e28a5b6e..3267d2a1 100644
--- a/etc/build.usage
+++ b/etc/build.usage
@@ -1,15 +1,19 @@
-usage: ./build.sh [-4|6] [-a nt32|nt64] [-b debug|release]
-                  [-c] [-h] [-N] [-r ALL[:step,..]] [-r name[,..][:step,..]]
-                  [-R] [-t[.gz|.bz2|.xz] [-v[v[v]]] [-x] [<target>[ ..]]
+usage: ./build.sh [-4|6]     [-a nt32|nt64]    [-b debug|release]
+                  [-c] [-h] [-N]  [-P [jobs]]  [-r ALL[:step,..]]
+                  [-r name[,..][:step,..]] [-R] [-t[.gz|.bz2|.xz]
+                  [-v[v[v]]] [-x] [<target>[ ..]]
         -4|-6                   Force IPv[46] when downloading files.
         -a nt32|nt64            Selects 32-bit or 64-bit architecture; defaults to nt64.
         -b debug|release        Selects debug or release build; defaults to debug.
         -c                      Clean ${PREFIX} before processing build scripts.
         -h                      Show this screen.
         -N                      Offline mode: no {wget,git-{clone,pull}}(1) calls.
+        -P [jobs]               Enables parallelisation at target-level, whenever applicable.
+                                The maximum count of jobs defaults to the number of logical
+                                processors on the host system.
         -r ALL[:step,..]
         -r name[,..][:step,..]  Restart the all packages/the specified comma-separated package(s)
-				completely or at optionally specified comma-separated step(s).
+                                completely or at optionally specified comma-separated step(s).
                                 Currently defined steps are:
                                 fetch_wget, fetch_git, fetch_extract,
                                 configure_patch_pre, configure_autotools, configure_patch,
diff --git a/subr/build_args.subr b/subr/build_args.subr
index 2175665c..8bf668a4 100644
--- a/subr/build_args.subr
+++ b/subr/build_args.subr
@@ -3,23 +3,24 @@
 #
 
 BUILD_ARGS_SPEC="
-	ARG_IPV4_ONLY:-4
-	ARG_IPV6_ONLY:-6
-	ARCH:arg:-a
-	BUILD:arg:-b
-	ARG_CLEAN:-c
-	ARG_DEBUG_MINIPIX:--debug-minipix
-	ARG_OFFLINE:-N
-	ARG_RELAXED:-R
-	ARG_RESTART:arg:-r
-	ARG_TARBALL:selfarg:-t
-	ARG_TARBALL:selfarg:-t.bz2
-	ARG_TARBALL:selfarg:-t.gz
-	ARG_TARBALL:selfarg:-t.xz
-	ARG_VERBOSE:selfarg:-v
-	ARG_VERBOSE:selfarg:-vv
-	ARG_VERBOSE:selfarg:-vvv
-	ARG_XTRACE:-x";
+	ARG_IPV4_ONLY:-4:
+	ARG_IPV6_ONLY:-6:
+	ARCH:arg:-a:
+	BUILD:arg:-b:
+	ARG_CLEAN:-c:
+	ARG_DEBUG_MINIPIX:--debug-minipix:
+	ARG_OFFLINE:-N:
+	ARG_PARALLEL:optarg:-P:auto
+	ARG_RELAXED:-R:
+	ARG_RESTART:arg:-r:
+	ARG_TARBALL:selfarg:-t:
+	ARG_TARBALL:selfarg:-t.bz2;
+	ARG_TARBALL:selfarg:-t.gz:
+	ARG_TARBALL:selfarg:-t.xz:
+	ARG_VERBOSE:selfarg:-v:
+	ARG_VERBOSE:selfarg:-vv:
+	ARG_VERBOSE:selfarg:-vvv:
+	ARG_XTRACE:-x:";
 
 build_args() {
 	local _spec="${BUILD_ARGS_SPEC}" _spec_arg _found;
@@ -29,9 +30,19 @@ build_args() {
 		fi;
 		for _spec_arg in ${_spec}; do
 			case "${_spec_arg}" in
-			*:${1})	case "${_spec_arg#*:}" in
+			*:${1}:*)
+				case "${_spec_arg#*:}" in
 				arg:*)
 					ex_rtl_set_var_unsafe "${_spec_arg%%:*}" "${2}"; shift; ;;
+				optarg:*)
+					if [ -n "${2}" ]\
+					&& [ "x${2#-}" = "x${2}" ]; then
+						ex_rtl_set_var_unsafe "${_spec_arg%%:*}" "${2}";
+						shift;
+					else
+						ex_rtl_set_var_unsafe "${_spec_arg%%:*}"	\
+							"${_spec_arg##*:}";
+					fi; ;;
 				selfarg:*)
 					ex_rtl_set_var_unsafe "${_spec_arg%%:*}" "${1}"; ;;
 				*)
diff --git a/subr/build_init.subr b/subr/build_init.subr
index 95ac397d..8b3e6181 100644
--- a/subr/build_init.subr
+++ b/subr/build_init.subr
@@ -15,6 +15,9 @@ build_init() {
 	&& [ -e /proc/cpuinfo ]; then
 		DEFAULT_BUILD_CPUS=$(awk '/^processor/{cpus++} END{print cpus}' /proc/cpuinfo);
 	fi;
+	if [ "${ARG_PARALLEL}" = auto ]; then
+		ARG_PARALLEL="${DEFAULT_BUILD_CPUS}";
+	fi;
 	: ${ARCH:=nt64}; : ${BUILD:=debug};
 	if [ "${ARCH}" = nt32 ]; then
 		DEFAULT_TARGET="i686-nt32-midipix";
diff --git a/subr/ex_pkg_dispatch.subr b/subr/ex_pkg_dispatch.subr
index f56146bf..92890ba6 100644
--- a/subr/ex_pkg_dispatch.subr
+++ b/subr/ex_pkg_dispatch.subr
@@ -46,7 +46,8 @@ ex_pkg_dispatch() {
 	&& [ "${_restart}" != ALL ]; then
 		_pkg_names="$(ex_rtl_lfilter "${_pkg_names}" "${_restart}")";
 	fi;
-	if [ "$(ex_rtl_get_var_unsafe ${_tgt_name_uc}_PARALLELISE)" = 1 ]; then
+	if [ "$(ex_rtl_get_var_unsafe ${_tgt_name_uc}_PARALLELISE)" = 1 ]\
+	&& [ "${ARG_PARALLEL:-0}" -gt 1 ]; then
 		_njobs_max="${DEFAULT_BUILD_CPUS}";
 	else
 		_njobs_max=1;