+# Checks if make's jobserver is enabled via MAKEFLAGS, but
+# the FD used to communicate with it is actually not available.
+sub is_make_jobserver_unavailable {
+ if (exists $ENV{MAKEFLAGS} &&
+ $ENV{MAKEFLAGS} =~ /(?:^|\s)--jobserver-fds=(\d+)/) {
+ if (!open(my $in, "<&$1")) {
+ return 1; # unavailable
+ }
+ else {
+ close $in;
+ return 0; # available
+ }
+ }
+
+ return; # no jobserver specified
+}
+
+# Cleans out jobserver options from MAKEFLAGS.
+sub clean_jobserver_makeflags {
+ if (exists $ENV{MAKEFLAGS}) {
+ if ($ENV{MAKEFLAGS} =~ /(?:^|\s)--jobserver-fds=(\d+)/) {
+ $ENV{MAKEFLAGS} =~ s/(?:^|\s)--jobserver-fds=\S+//g;
+ $ENV{MAKEFLAGS} =~ s/(?:^|\s)-j\b//g;
+ }
+ delete $ENV{MAKEFLAGS} if $ENV{MAKEFLAGS} =~ /^\s*$/;
+ }
+}
+
+# If cross-compiling, returns appropriate cross version of command.
+sub cross_command {
+ my $command=shift;
+ if (dpkg_architecture_value("DEB_BUILD_GNU_TYPE")
+ ne dpkg_architecture_value("DEB_HOST_GNU_TYPE")) {
+ return dpkg_architecture_value("DEB_HOST_GNU_TYPE")."-$command";
+ }
+ else {
+ return $command;
+ }
+}
+