lib: Annotate more function as NULL terminated

While __attribute((sentinel)) (exposed by glib under
G_GNUC_NULL_TERMINATED macro) is a gcc extension, it's supported
by clang too. It's already being used throughout our code but
some functions that take variadic arguments and expect NULL at
the end were lacking such annotation. Fill them in.

After this, there are still some functions left untouched because
they expect a different sentinel than NULL. Unfortunately, glib
does not provide macro for different sentinels. We may come up
with our own, but let's save that for future work.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

src/qemu/qemu_monitor.h

@@ -947,7 +947,8 @@ int qemuMonitorDelDevice(qemuMonitor *mon,
 int qemuMonitorCreateObjectProps(virJSONValue **propsret,
                                  const char *type,
                                  const char *alias,
-                                 ...);
+                                 ...)
+    G_GNUC_NULL_TERMINATED;
 
 int qemuMonitorAddObject(qemuMonitor *mon,
                          virJSONValue **props,

src/qemu/qemu_monitor_json.c

@@ -468,7 +468,7 @@ qemuMonitorJSONHasError(virJSONValue *reply,
  *
  * Returns 0 on success and -1 on error.
  */
-static int
+static int G_GNUC_NULL_TERMINATED
 qemuMonitorJSONTransactionAdd(virJSONValue *actions,
                               const char *cmdname,
                               ...)

tests/qemumigrationcookiexmltest.c

@@ -39,7 +39,7 @@ static virQEMUDriver driver;
 
 static virBuffer testnamebuf = VIR_BUFFER_INITIALIZER;
 
-static const char *
+static const char * G_GNUC_NULL_TERMINATED
 tn(const char *str, ...)
 {
     va_list ap;

tests/testutils.h

@@ -113,7 +113,8 @@ void virTestFakeRootDirCleanup(char *fakerootdir);
 int virTestMain(int argc,
                 char **argv,
                 int (*func)(void),
-                ...);
+                ...)
+    G_GNUC_NULL_TERMINATED;
 
 /* Setup, then call func() */
 #define VIR_TEST_MAIN(func) \

tests/testutilsqemuschema.h

@@ -40,7 +40,8 @@ testQEMUSchemaValidateCommand(const char *command,
 
 int
 testQEMUSchemaEntryMatchTemplate(virJSONValue *schemaentry,
-                                 ...);
+                                 ...)
+    G_GNUC_NULL_TERMINATED;
 
 
 virJSONValue *

tools/vsh.c

@@ -2418,7 +2418,7 @@ vshCloseLogFile(vshControl *ctl)
 }
 
 #ifndef WIN32
-static void
+static void G_GNUC_NULL_TERMINATED
 vshPrintRaw(vshControl *ctl, ...)
 {
     va_list ap;