Index: kernel/test/synch/rcu1.c
===================================================================
--- kernel/test/synch/rcu1.c	(revision 4ec9ea4158674bc15f751d826091779955c286a4)
+++ kernel/test/synch/rcu1.c	(revision 2708f6aa00d00b5d4b4fa38d184dbe4b24ff32f1)
@@ -43,5 +43,5 @@
 
 static int one_idx = 0;
-static thread_t *thread[MAX_THREADS] = {0};
+static thread_t *thread[MAX_THREADS] = { NULL };
 
 typedef struct {
@@ -100,5 +100,5 @@
 	
 	for (size_t i = 0; i < thread_cnt; ++i) {
-		run_thread(i, func, 0);
+		run_thread(i, func, NULL);
 	}
 }
@@ -123,5 +123,5 @@
 			
 			thread_detach(thread[i]);
-			thread[i] = 0;
+			thread[i] = NULL;
 		}
 	}
@@ -145,5 +145,5 @@
 		thread_join(thread[one_idx]);
 		thread_detach(thread[one_idx]);
-		thread[one_idx] = 0;
+		thread[one_idx] = NULL;
 	}
 }
@@ -337,5 +337,5 @@
 	
 	TPRINTF("\nRun a single reader that posts one callback.\n");
-	run_one(one_cb_reader, 0);
+	run_one(one_cb_reader, NULL);
 	join_one();
 	
@@ -1015,5 +1015,5 @@
 		{ 0, do_expedite, "do_expedite" },
 		{ 1, do_stress, "do_stress" },
-		{ 0, 0, 0 }
+		{ 0, NULL, NULL }
 	};
 	
@@ -1023,5 +1023,5 @@
 	uint64_t delta_gps = 0;
 	
-	for (int i = 0; test_func[i].func != 0; ++i) {
+	for (int i = 0; test_func[i].func; ++i) {
 		if (!test_func[i].include) {
 			TPRINTF("\nSubtest %s() skipped.\n", test_func[i].desc);
@@ -1047,5 +1047,5 @@
 
 	if (success)
-		return 0;
+		return NULL;
 	else
 		return "One of the tests failed.";
Index: kernel/test/synch/workqueue2.c
===================================================================
--- kernel/test/synch/workqueue2.c	(revision 4ec9ea4158674bc15f751d826091779955c286a4)
+++ kernel/test/synch/workqueue2.c	(revision 2708f6aa00d00b5d4b4fa38d184dbe4b24ff32f1)
@@ -116,5 +116,5 @@
 	test_custom_workq_impl(true, "test-workq-stop");
 	/* Errors are expected. */
-	return 0;
+	return NULL;
 }
 
@@ -122,5 +122,5 @@
 const char *test_workqueue_all(void)
 {
-	const char *err = 0;
+	const char *err = NULL;
 	const char *res;
 	
Index: kernel/test/synch/workqueue3.c
===================================================================
--- kernel/test/synch/workqueue3.c	(revision 4ec9ea4158674bc15f751d826091779955c286a4)
+++ kernel/test/synch/workqueue3.c	(revision 2708f6aa00d00b5d4b4fa38d184dbe4b24ff32f1)
@@ -56,5 +56,5 @@
 static const char *do_test(bool exit_early)
 {
-	const char *err = 0;
+	const char *err = NULL;
 	TPRINTF("Stress testing system queue.\n");
 	TPRINTF("First run:\n");