diff --git a/tests/child-test.c b/tests/child-test.c
index 2fbc741d8..9ebc202b4 100644
--- a/tests/child-test.c
+++ b/tests/child-test.c
@@ -51,7 +51,7 @@ gint alive;
 char *argv0;
 #endif
 
-GPid
+static GPid
 get_a_child (gint ttl)
 {
   GPid pid;
@@ -89,7 +89,7 @@ get_a_child (gint ttl)
 #endif /* G_OS_WIN32 */
 }
 
-gboolean
+static gboolean
 child_watch_callback (GPid pid, gint status, gpointer data)
 {
 #ifdef VERBOSE
diff --git a/tests/iochannel-test.c b/tests/iochannel-test.c
index 9d6a522a1..492b47e20 100644
--- a/tests/iochannel-test.c
+++ b/tests/iochannel-test.c
@@ -15,7 +15,7 @@ static void
 test_small_writes (void)
 {
   GIOChannel *io;
-  GIOStatus status;
+  GIOStatus status = G_IO_STATUS_ERROR;
   guint cnt; 
   gchar tmp;
   GError *error = NULL;
diff --git a/tests/mainloop-test.c b/tests/mainloop-test.c
index 4bcb05f3f..f4a805e3c 100644
--- a/tests/mainloop-test.c
+++ b/tests/mainloop-test.c
@@ -54,7 +54,7 @@ struct _TestData
 
 static void cleanup_crawlers (GMainContext *context);
 
-gboolean
+static gboolean
 read_all (GIOChannel *channel, char *buf, gsize len)
 {
   gsize bytes_read = 0;
@@ -78,7 +78,7 @@ read_all (GIOChannel *channel, char *buf, gsize len)
   return TRUE;
 }
 
-gboolean
+static gboolean
 write_all (GIOChannel *channel, char *buf, gsize len)
 {
   gsize bytes_written = 0;
@@ -97,7 +97,7 @@ write_all (GIOChannel *channel, char *buf, gsize len)
   return TRUE;
 }
 
-gboolean
+static gboolean
 adder_callback (GIOChannel   *source,
 		GIOCondition  condition,
 		gpointer      data)
@@ -122,7 +122,7 @@ adder_callback (GIOChannel   *source,
   return TRUE;
 }
 
-gboolean
+static gboolean
 timeout_callback (gpointer data)
 {
   AddrData *addr_data = data;
@@ -132,7 +132,7 @@ timeout_callback (gpointer data)
   return TRUE;
 }
 
-gpointer
+static gpointer
 adder_thread (gpointer data)
 {
   GMainContext *context;
@@ -194,7 +194,7 @@ adder_thread (gpointer data)
   return NULL;
 }
 
-void
+static void
 io_pipe (GIOChannel **channels)
 {
   gint fds[2];
@@ -212,7 +212,7 @@ io_pipe (GIOChannel **channels)
   g_io_channel_set_close_on_unref (channels[1], TRUE);
 }
 
-void
+static void
 do_add (GIOChannel *in, gint a, gint b)
 {
   char buf1[32];
@@ -225,7 +225,7 @@ do_add (GIOChannel *in, gint a, gint b)
   write_all (in, buf2, 32);
 }
 
-gboolean
+static gboolean
 adder_response (GIOChannel   *source,
 		GIOCondition  condition,
 		gpointer      data)
@@ -261,7 +261,7 @@ adder_response (GIOChannel   *source,
   return TRUE;
 }
 
-void
+static void
 create_adder_thread (void)
 {
   GError *err = NULL;
diff --git a/tests/module-test.c b/tests/module-test.c
index 9b95b0a2a..dd99b710f 100644
--- a/tests/module-test.c
+++ b/tests/module-test.c
@@ -32,6 +32,8 @@
 
 gchar* global_state;
 
+G_MODULE_EXPORT void g_clash_func (void);
+
 G_MODULE_EXPORT void
 g_clash_func (void)
 {
diff --git a/tests/onceinit.c b/tests/onceinit.c
index fa513d10e..f142fbff8 100644
--- a/tests/onceinit.c
+++ b/tests/onceinit.c
@@ -112,13 +112,15 @@ int
 main (int   argc,
       char *argv[])
 {
-  GThread *threads[N_THREADS];
+  G_GNUC_UNUSED GThread *threads[N_THREADS];
   int i;
+  void *p;
+
   /* test simple initializer */
   initializer1();
   initializer1();
   /* test pointer initializer */
-  void *p = initializer2();
+  p = initializer2();
   g_assert (p == &dummy_value);
   p = initializer2();
   g_assert (p == &dummy_value);
diff --git a/tests/slice-concurrent.c b/tests/slice-concurrent.c
index f4031441d..202cfe78d 100644
--- a/tests/slice-concurrent.c
+++ b/tests/slice-concurrent.c
@@ -37,7 +37,7 @@ struct ThreadData
   int      n_freed;
 } tdata[N_THREADS];
 
-void*
+static void *
 thread_func (void *arg)
 {
   struct ThreadData *td = arg;
@@ -45,18 +45,23 @@ thread_func (void *arg)
 /*   g_print ("Thread %d starting\n", td->thread_id); */
   for (i = 0; i < N_ALLOCS; i++)
     {
+      int bytes;
+      char *mem;
+      int f;
+      int t;
+
       if (rand() % (N_ALLOCS / 20) == 0)
 	g_print ("%c", 'a' - 1 + td->thread_id);
 
       /* allocate block of random size and randomly fill */
-      int   bytes = rand() % MAX_BLOCK_SIZE + 1;
-      char *mem = g_slice_alloc (bytes);
-      int f;
+      bytes = rand() % MAX_BLOCK_SIZE + 1;
+      mem = g_slice_alloc (bytes);
+
       for (f = 0; f < bytes; f++)
 	mem[f] = rand();
 
       /* associate block with random thread */
-      int t = rand() % N_THREADS;
+      t = rand() % N_THREADS;
       g_mutex_lock (&tdata[t].to_free_mutex);
       tdata[t].to_free[tdata[t].n_to_free] = mem;
       tdata[t].bytes_to_free[tdata[t].n_to_free] = bytes;
@@ -87,7 +92,7 @@ thread_func (void *arg)
 }
 
 int
-main()
+main (void)
 {
   int t;
 
diff --git a/tests/thread-test.c b/tests/thread-test.c
index 16844010a..93c01585e 100644
--- a/tests/thread-test.c
+++ b/tests/thread-test.c
@@ -277,7 +277,7 @@ test_g_static_rw_lock_thread (gpointer data)
 }
 
 static void
-test_g_static_rw_lock ()
+test_g_static_rw_lock (void)
 {
   GThread *threads[THREADS];
   guint i;
@@ -368,8 +368,8 @@ test_g_thread_once (void)
 }
 
 /* run all the tests */
-void
-run_all_tests()
+static void
+run_all_tests (void)
 {
   test_g_mutex ();
   test_g_static_rec_mutex ();
diff --git a/tests/threadpool-test.c b/tests/threadpool-test.c
index eb7c16282..07420df18 100644
--- a/tests/threadpool-test.c
+++ b/tests/threadpool-test.c
@@ -332,7 +332,7 @@ test_thread_idle_timeout (gpointer data)
 }
 
 static void
-test_thread_idle_time ()
+test_thread_idle_time (void)
 {
   guint limit = 50;
   guint interval = 10000;