+#### Test parallel building and related options / routines
+@tmp = ( $ENV{MAKEFLAGS}, $ENV{DEB_BUILD_OPTIONS} );
+
+# Test is_make_jobserver_unavailable and clean_jobserver_makeflags.
+
+$ENV{MAKEFLAGS} = "--jobserver-fds=103,104 -j";
+ok(is_make_jobserver_unavailable(), "unavailable jobserver" );
+clean_jobserver_makeflags();
+ok(! exists $ENV{MAKEFLAGS}, "unset makeflags");
+
+$ENV{MAKEFLAGS} = "-a --jobserver-fds=103,104 -j -b";
+ok(is_make_jobserver_unavailable(), "unavailable jobserver" );
+clean_jobserver_makeflags();
+is($ENV{MAKEFLAGS}, "-a -b", "clean makeflags");
+
+$ENV{MAKEFLAGS} = " --jobserver-fds=1,2 -j ";
+ok(! is_make_jobserver_unavailable(), "available jobserver" );
+clean_jobserver_makeflags();
+ok(! exists $ENV{MAKEFLAGS}, "unset makeflags");
+
+$ENV{MAKEFLAGS} = "-a -j -b";
+ok(! is_make_jobserver_unavailable(), "no specified jobserver");
+clean_jobserver_makeflags();
+is($ENV{MAKEFLAGS}, "-a -j -b", "clean makeflags does not remove -j");
+
+$ENV{MAKEFLAGS} = "-a --jobs -b";
+ok(! is_make_jobserver_unavailable(), "no specified jobserver");
+clean_jobserver_makeflags();
+is($ENV{MAKEFLAGS}, "-a --jobs -b", "clean makeflags does not remove --jobs");
+
+$ENV{MAKEFLAGS} = "-j6";
+ok(! is_make_jobserver_unavailable(), "no specified jobserver");
+clean_jobserver_makeflags();
+is($ENV{MAKEFLAGS}, "-j6", "clean makeflags does not remove -j6");
+
+$ENV{MAKEFLAGS} = "-a -j6 --jobs=7";
+ok(! is_make_jobserver_unavailable(), "no specified jobserver");
+clean_jobserver_makeflags();
+is($ENV{MAKEFLAGS}, "-a -j6 --jobs=7", "clean makeflags does not remove -j or --jobs");
+
+$ENV{MAKEFLAGS} = "-j6 --jobserver-fds=5,6 --jobs=8";
+ok(is_make_jobserver_unavailable(), "unavailable jobserver");
+clean_jobserver_makeflags();
+is($ENV{MAKEFLAGS}, "-j6 --jobs=8", "jobserver options removed");
+
+# Test parallel building with makefile build system.
+$ENV{MAKEFLAGS} = "";
+$ENV{DEB_BUILD_OPTIONS} = "";
+
+sub do_parallel_mk {
+ my $dh_opts=shift || "";
+ my $make_opts=shift || "";
+ return process_stdout(
+ "LANG=C LC_ALL=C LC_MESSAGES=C $TOPDIR/dh_auto_build -Smakefile $dh_opts " .
+ "-- -s -f parallel.mk $make_opts 2>&1 >/dev/null", "");
+}
+
+sub test_isnt_parallel {
+ my ($got, $desc) = @_;
+ my @makemsgs = grep /^make[\d\[\]]*:/, @$got;
+ if (@makemsgs) {
+ like( $makemsgs[0], qr/Error 10/, $desc );
+ }
+ else {
+ ok( scalar(@makemsgs) > 0, $desc );
+ }
+}
+
+sub test_is_parallel {
+ my ($got, $desc) = @_;
+ is_deeply( $got, [] , $desc );
+ is( $?, 0, "(exit status=0) $desc");
+}
+
+test_isnt_parallel( do_parallel_mk(),
+ "No parallel by default" );
+test_isnt_parallel( do_parallel_mk("parallel"),
+ "No parallel by default with --parallel" );
+test_isnt_parallel( do_parallel_mk("--max-parallel=5"),
+ "No parallel by default with --max-parallel=5" );
+
+$ENV{DEB_BUILD_OPTIONS}="parallel=5";
+test_isnt_parallel( do_parallel_mk(),
+ "DEB_BUILD_OPTIONS=parallel=5 without parallel options" );
+test_is_parallel( do_parallel_mk("--parallel"),
+ "DEB_BUILD_OPTIONS=parallel=5 with --parallel" );
+test_is_parallel( do_parallel_mk("--max-parallel=2"),
+ "DEB_BUILD_OPTIONS=parallel=5 with --max-parallel=2" );
+test_isnt_parallel( do_parallel_mk("--max-parallel=1"),
+ "DEB_BUILD_OPTIONS=parallel=5 with --max-parallel=1" );
+
+$ENV{MAKEFLAGS} = "--jobserver-fds=105,106 -j";
+$ENV{DEB_BUILD_OPTIONS}="";
+test_isnt_parallel( do_parallel_mk(),
+ "makefile.pm (no parallel): no make warnings about unavailable jobserver" );
+$ENV{DEB_BUILD_OPTIONS}="parallel=5";
+test_is_parallel( do_parallel_mk("--parallel"),
+ "DEB_BUILD_OPTIONS=parallel=5: no make warnings about unavail parent jobserver" );
+
+$ENV{MAKEFLAGS} = "-j2";
+$ENV{DEB_BUILD_OPTIONS}="";
+test_isnt_parallel( do_parallel_mk(),
+ "MAKEFLAGS=-j2: dh_auto_build ignores MAKEFLAGS" );
+test_isnt_parallel( do_parallel_mk("--max-parallel=1"),
+ "MAKEFLAGS=-j2 with --max-parallel=1: dh_auto_build enforces -j1" );
+
+# Test dh dpkg-buildpackage -jX detection
+sub do_rules_for_parallel {
+ my $cmdline=shift || "";
+ my $stdin=shift || "";
+ return process_stdout("LANG=C LC_ALL=C LC_MESSAGES=C PATH=$TOPDIR:\$PATH " .
+ "make -f - $cmdline 2>&1 >/dev/null", $stdin);
+}
+
+doit("ln", "-sf", "parallel.mk", "Makefile");
+
+# Test if dh+override+$(MAKE) legacy punctuation hack work as before
+$ENV{MAKEFLAGS} = "-j5";
+$ENV{DEB_BUILD_OPTIONS} = "parallel=5";
+
+$tmp = write_debian_rules(<<'EOF');
+#!/usr/bin/make -f
+override_dh_auto_build:
+ $(MAKE)
+%:
+ @dh_clean > /dev/null 2>&1
+ @+dh --buildsystem=makefile --after=dh_auto_configure --until=dh_auto_build $@
+ @dh_clean > /dev/null 2>&1
+EOF
+test_is_parallel( do_rules_for_parallel("build", "include debian/rules"),
+ "legacy punctuation hacks: +dh, override with \$(MAKE)" );
+unlink "debian/rules";
+
+if (defined $tmp) {
+ rename($tmp, "debian/rules");
+}
+else {
+ unlink("debian/rules");
+}
+
+# Clean up after parallel testing
+END {
+ system("rm", "-f", "Makefile");
+}
+$ENV{MAKEFLAGS} = $tmp[0] if defined $tmp[0];
+$ENV{DEB_BUILD_OPTIONS} = $tmp[1] if defined $tmp[1];
+