diff --git a/test/api/hb-test.h b/test/api/hb-test.h
index 307845f62..39d091b60 100644
--- a/test/api/hb-test.h
+++ b/test/api/hb-test.h
@@ -42,6 +42,7 @@ HB_BEGIN_DECLS
 /* Just in case */
 #undef G_DISABLE_ASSERT
 
+#define HB_UNUSED	G_GNUC_UNUSED
 
 /* Misc */
 
diff --git a/test/api/test-blob.c b/test/api/test-blob.c
index d566f4e9d..7914a26ce 100644
--- a/test/api/test-blob.c
+++ b/test/api/test-blob.c
@@ -195,7 +195,7 @@ fixture_init (fixture_t *fixture, gconstpointer user_data)
 }
 
 static void
-fixture_finish (fixture_t *fixture, gconstpointer user_data)
+fixture_finish (fixture_t *fixture, gconstpointer user_data HB_UNUSED)
 {
   hb_blob_destroy (fixture->blob);
   g_assert_cmpint (fixture->freed, ==, 1);
diff --git a/test/api/test-c.c b/test/api/test-c.c
index 4b43b8379..78d6e974d 100644
--- a/test/api/test-c.c
+++ b/test/api/test-c.c
@@ -58,7 +58,7 @@
 #endif
 
 int
-main (int argc, char **argv)
+main (void)
 {
   return !*hb_shape_list_shapers ();
 }
diff --git a/test/api/test-font.c b/test/api/test-font.c
index 4a2393ec6..4cd8dd8bf 100644
--- a/test/api/test-font.c
+++ b/test/api/test-font.c
@@ -83,7 +83,7 @@ free_up (void *user_data)
 }
 
 static hb_blob_t *
-get_table (hb_face_t *face, hb_tag_t tag, void *user_data)
+get_table (hb_face_t *face HB_UNUSED, hb_tag_t tag, void *user_data HB_UNUSED)
 {
   if (tag == HB_TAG ('a','b','c','d'))
     return hb_blob_create (test_data, sizeof (test_data), HB_MEMORY_MODE_READONLY, NULL, NULL);
@@ -210,10 +210,10 @@ test_fontfuncs_nil (void)
 }
 
 static hb_bool_t
-contour_point_func1 (hb_font_t *font, void *font_data,
-		     hb_codepoint_t glyph, unsigned int point_index,
+contour_point_func1 (hb_font_t *font HB_UNUSED, void *font_data HB_UNUSED,
+		     hb_codepoint_t glyph, unsigned int point_index HB_UNUSED,
 		     hb_position_t *x, hb_position_t *y,
-		     void *user_data)
+		     void *user_data HB_UNUSED)
 {
   if (glyph == 1) {
     *x = 2;
@@ -230,10 +230,10 @@ contour_point_func1 (hb_font_t *font, void *font_data,
 }
 
 static hb_bool_t
-contour_point_func2 (hb_font_t *font, void *font_data,
+contour_point_func2 (hb_font_t *font, void *font_data HB_UNUSED,
 		     hb_codepoint_t glyph, unsigned int point_index,
 		     hb_position_t *x, hb_position_t *y,
-		     void *user_data)
+		     void *user_data HB_UNUSED)
 {
   if (glyph == 1) {
     *x = 6;
@@ -246,9 +246,9 @@ contour_point_func2 (hb_font_t *font, void *font_data,
 }
 
 static hb_position_t
-glyph_h_advance_func1 (hb_font_t *font, void *font_data,
+glyph_h_advance_func1 (hb_font_t *font HB_UNUSED, void *font_data HB_UNUSED,
 		       hb_codepoint_t glyph,
-		       void *user_data)
+		       void *user_data HB_UNUSED)
 {
   if (glyph == 1)
     return 8;
diff --git a/test/api/test-multithread.c b/test/api/test-multithread.c
index b9efca9bf..de288b6a4 100644
--- a/test/api/test-multithread.c
+++ b/test/api/test-multithread.c
@@ -101,7 +101,7 @@ thread_func (void *data)
   return 0;
 }
 
-void
+static void
 test_body (void)
 {
   int i;
diff --git a/test/api/test-ot-color.c b/test/api/test-ot-color.c
index 22584d20e..254f01556 100644
--- a/test/api/test-ot-color.c
+++ b/test/api/test-ot-color.c
@@ -99,6 +99,7 @@ static hb_face_t *cpal_v0 = NULL;
 static hb_face_t *cpal_v1 = NULL;
 
 
+#if 0
 #define assert_color_rgba(colors, i, r, g, b, a) G_STMT_START {	\
   const hb_ot_color_t *_colors = (colors); \
   const size_t _i = (i); \
@@ -122,7 +123,6 @@ static hb_face_t *cpal_v1 = NULL;
 } G_STMT_END
 
 
-#if 0
 static void
 test_hb_ot_color_get_palette_count (void)
 {
diff --git a/test/api/test-shape.c b/test/api/test-shape.c
index 6232e7382..2a0024d04 100644
--- a/test/api/test-shape.c
+++ b/test/api/test-shape.c
@@ -41,9 +41,9 @@
 static const char test_data[] = "test\0data";
 
 static hb_position_t
-glyph_h_advance_func (hb_font_t *font, void *font_data,
+glyph_h_advance_func (hb_font_t *font HB_UNUSED, void *font_data HB_UNUSED,
 		      hb_codepoint_t glyph,
-		      void *user_data)
+		      void *user_data HB_UNUSED)
 {
   switch (glyph) {
   case 1: return 10;
@@ -54,10 +54,10 @@ glyph_h_advance_func (hb_font_t *font, void *font_data,
 }
 
 static hb_bool_t
-glyph_func (hb_font_t *font, void *font_data,
-	    hb_codepoint_t unicode, hb_codepoint_t variant_selector,
+glyph_func (hb_font_t *font HB_UNUSED, void *font_data HB_UNUSED,
+	    hb_codepoint_t unicode, hb_codepoint_t variation_selector HB_UNUSED,
 	    hb_codepoint_t *glyph,
-	    void *user_data)
+	    void *user_data HB_UNUSED)
 {
   switch (unicode) {
   case 'T': *glyph = 1; return TRUE;
@@ -68,9 +68,9 @@ glyph_func (hb_font_t *font, void *font_data,
 }
 
 static hb_position_t
-glyph_h_kerning_func (hb_font_t *font, void *font_data,
+glyph_h_kerning_func (hb_font_t *font HB_UNUSED, void *font_data HB_UNUSED,
 		      hb_codepoint_t left, hb_codepoint_t right,
-		      void *user_data)
+		      void *user_data HB_UNUSED)
 {
   if (left == 1 && right == 2)
     return -2;
diff --git a/test/api/test-unicode.c b/test/api/test-unicode.c
index 88f12e779..4238ca992 100644
--- a/test/api/test-unicode.c
+++ b/test/api/test-unicode.c
@@ -645,18 +645,18 @@ typedef struct {
 } data_fixture_t;
 
 static void
-data_fixture_init (data_fixture_t *f, gconstpointer user_data)
+data_fixture_init (data_fixture_t *f, gconstpointer user_data HB_UNUSED)
 {
   f->data[0].value = MAGIC0;
   f->data[1].value = MAGIC1;
 }
 static void
-data_fixture_finish (data_fixture_t *f, gconstpointer user_data)
+data_fixture_finish (data_fixture_t *f HB_UNUSED, gconstpointer user_data HB_UNUSED)
 {
 }
 
 static void
-test_unicode_subclassing_nil (data_fixture_t *f, gconstpointer user_data)
+test_unicode_subclassing_nil (data_fixture_t *f, gconstpointer user_data HB_UNUSED)
 {
   hb_unicode_funcs_t *uf, *aa;
 
@@ -678,7 +678,7 @@ test_unicode_subclassing_nil (data_fixture_t *f, gconstpointer user_data)
 }
 
 static void
-test_unicode_subclassing_default (data_fixture_t *f, gconstpointer user_data)
+test_unicode_subclassing_default (data_fixture_t *f, gconstpointer user_data HB_UNUSED)
 {
   hb_unicode_funcs_t *uf, *aa;
 
@@ -697,7 +697,7 @@ test_unicode_subclassing_default (data_fixture_t *f, gconstpointer user_data)
 }
 
 static void
-test_unicode_subclassing_deep (data_fixture_t *f, gconstpointer user_data)
+test_unicode_subclassing_deep (data_fixture_t *f, gconstpointer user_data HB_UNUSED)
 {
   hb_unicode_funcs_t *uf, *aa;