build-sys: allow cross-compilation

When cross-compiling systemd, the introspection XML files fail to be
generated because the systemd host binary is not executable. This patch
works around this by putting the introspection XML data into separate
ELF sections and extracting them from the binary when generating the XML
files.

The extracted XML data is passed through the strings utility in order to
strip the trailing NUL character. A small AWK script is used to prepend
the doctype and add the opening and closing node tags respectively.
Finally, the C preprocessor is used to substitute the correct doctype
information from the D-Bus header files.

Makefile.am

@@ -1118,8 +1118,12 @@ CLEANFILES += \
 	${XML_IN_FILES:.xml.in=.html.in}
 endif
 
+DBUS_PREPROCESS = $(CPP) -P $(DBUS_CFLAGS) -imacros dbus/dbus-protocol.h
+
 org.freedesktop.systemd1.%.xml: systemd
-	$(AM_V_GEN)SYSTEMD_SKIP_API_MOUNTS=1 ./systemd --introspect=${@:.xml=} > $@
+	$(AM_V_GEN)$(OBJCOPY) -O binary -j introspect.$* $< $@.tmp && \
+		$(STRINGS) $@.tmp | $(AWK) -f introspect.awk | \
+		$(DBUS_PREPROCESS) -o $@ - && rm $@.tmp
 
 CLEANFILES += \
 	$(dbusinterface_DATA)

configure.ac

@@ -48,6 +48,9 @@ AM_PROG_CC_C_O
 AC_PROG_GCC_TRADITIONAL
 AC_USE_SYSTEM_EXTENSIONS
 
+AC_CHECK_TOOL(OBJCOPY, objcopy)
+AC_CHECK_TOOL(STRINGS, strings)
+
 CC_CHECK_CFLAGS_APPEND([ \
         -pipe \
         -Wall \

introspect.awk

@@ -0,0 +1,13 @@
+BEGIN {
+	print "<!DOCTYPE node PUBLIC DBUS_INTROSPECT_1_0_XML_PUBLIC_IDENTIFIER"
+	print "DBUS_INTROSPECT_1_0_XML_SYSTEM_IDENTIFIER>"
+	print "<node>"
+}
+
+// {
+	print
+}
+
+END {
+	print "</node>"
+}

src/dbus-automount.c

@@ -38,7 +38,7 @@
         BUS_INTROSPECTABLE_INTERFACE                                 \
         "</node>\n"
 
-const char bus_automount_interface[] = BUS_AUTOMOUNT_INTERFACE;
+const char bus_automount_interface[] _introspect_("Automount") = BUS_AUTOMOUNT_INTERFACE;
 
 DBusHandlerResult bus_automount_message_handler(Unit *u, DBusConnection *c, DBusMessage *message) {
         const BusProperty properties[] = {

src/dbus-device.c

@@ -37,7 +37,7 @@
         BUS_INTROSPECTABLE_INTERFACE                                    \
         "</node>\n"
 
-const char bus_device_interface[] = BUS_DEVICE_INTERFACE;
+const char bus_device_interface[] _introspect_("Device") = BUS_DEVICE_INTERFACE;
 
 const char bus_device_invalidating_properties[] =
         "SysFSPath\0"

src/dbus-job.c

@@ -43,7 +43,7 @@
         BUS_INTROSPECTABLE_INTERFACE                                  \
         "</node>\n"
 
-const char bus_job_interface[] = BUS_JOB_INTERFACE;
+const char bus_job_interface[] _introspect_("Job") = BUS_JOB_INTERFACE;
 
 #define INVALIDATING_PROPERTIES                 \
         "State\0"                               \

src/dbus-manager.c

@@ -202,7 +202,7 @@
 #define INTROSPECTION_END                                               \
         "</node>\n"
 
-const char bus_manager_interface[] = BUS_MANAGER_INTERFACE;
+const char bus_manager_interface[] _introspect_("Manager") = BUS_MANAGER_INTERFACE;
 
 static DEFINE_BUS_PROPERTY_APPEND_ENUM(bus_manager_append_running_as, manager_running_as, ManagerRunningAs);
 

src/dbus-mount.c

@@ -50,7 +50,7 @@
         BUS_INTROSPECTABLE_INTERFACE                                    \
         "</node>\n"
 
-const char bus_mount_interface[] = BUS_MOUNT_INTERFACE;
+const char bus_mount_interface[] _introspect_("Mount") = BUS_MOUNT_INTERFACE;
 
 const char bus_mount_invalidating_properties[] =
         "What\0"

src/dbus-path.c

@@ -41,7 +41,7 @@
         BUS_INTROSPECTABLE_INTERFACE                                    \
         "</node>\n"
 
-const char bus_path_interface[] = BUS_PATH_INTERFACE;
+const char bus_path_interface[] _introspect_("Path") = BUS_PATH_INTERFACE;
 
 static int bus_path_append_paths(Manager *m, DBusMessageIter *i, const char *property, void *data) {
         Path *p = data;

src/dbus-service.c

@@ -90,7 +90,7 @@
         BUS_INTROSPECTABLE_INTERFACE                                    \
         "</node>\n"
 
-const char bus_service_interface[] = BUS_SERVICE_INTERFACE;
+const char bus_service_interface[] _introspect_("Service") = BUS_SERVICE_INTERFACE;
 
 const char bus_service_invalidating_properties[] =
         "ExecStartPre\0"

src/dbus-snapshot.c

@@ -38,7 +38,7 @@
         BUS_INTROSPECTABLE_INTERFACE                                    \
         "</node>\n"
 
-const char bus_snapshot_interface[] = BUS_SNAPSHOT_INTERFACE;
+const char bus_snapshot_interface[] _introspect_("Snapshot") = BUS_SNAPSHOT_INTERFACE;
 
 DBusHandlerResult bus_snapshot_message_handler(Unit *u, DBusConnection *c, DBusMessage *message) {
         const BusProperty properties[] = {

src/dbus-socket.c

@@ -64,7 +64,7 @@
         BUS_INTROSPECTABLE_INTERFACE                                    \
         "</node>\n"
 
-const char bus_socket_interface[] = BUS_SOCKET_INTERFACE;
+const char bus_socket_interface[] _introspect_("Socket") = BUS_SOCKET_INTERFACE;
 
 const char bus_socket_invalidating_properties[] =
         "ExecStartPre\0"

src/dbus-swap.c

@@ -47,7 +47,7 @@
         BUS_INTROSPECTABLE_INTERFACE                                    \
         "</node>\n"
 
-const char bus_swap_interface[] = BUS_SWAP_INTERFACE;
+const char bus_swap_interface[] _introspect_("Swap") = BUS_SWAP_INTERFACE;
 
 const char bus_swap_invalidating_properties[] =
         "What\0"

src/dbus-target.c

@@ -38,7 +38,7 @@
         BUS_INTROSPECTABLE_INTERFACE                                    \
         "</node>\n"
 
-const char bus_target_interface[] = BUS_TARGET_INTERFACE;
+const char bus_target_interface[] _introspect_("Target") = BUS_TARGET_INTERFACE;
 
 DBusHandlerResult bus_target_message_handler(Unit *u, DBusConnection *c, DBusMessage *message) {
         const BusProperty properties[] = {

src/dbus-timer.c

@@ -42,7 +42,7 @@
         BUS_INTROSPECTABLE_INTERFACE                                    \
         "</node>\n"
 
-const char bus_timer_interface[] = BUS_TIMER_INTERFACE;
+const char bus_timer_interface[] _introspect_("Timer") = BUS_TIMER_INTERFACE;
 
 const char bus_timer_invalidating_properties[] =
         "Timers\0"

src/dbus-unit.c

@@ -26,7 +26,7 @@
 #include "dbus-unit.h"
 #include "bus-errors.h"
 
-const char bus_unit_interface[] = BUS_UNIT_INTERFACE;
+const char bus_unit_interface[] _introspect_("Unit") = BUS_UNIT_INTERFACE;
 
 #define INVALIDATING_PROPERTIES                 \
         "LoadState\0"                           \

src/macro.h

@@ -45,6 +45,7 @@
 #define _public_ __attribute__ ((visibility("default")))
 #define _hidden_ __attribute__ ((visibility("hidden")))
 #define _weakref_(x) __attribute__((weakref(#x)))
+#define _introspect_(x) __attribute__((section("introspect." x)))
 
 /* Rounds up */
 static inline size_t ALIGN(size_t l) {