diff --git a/src/hb-fallback-shape.cc b/src/hb-fallback-shape.cc
index 989596ee5..bdc8a80c4 100644
--- a/src/hb-fallback-shape.cc
+++ b/src/hb-fallback-shape.cc
@@ -35,13 +35,13 @@
 struct hb_fallback_shaper_face_data_t {};
 
 hb_fallback_shaper_face_data_t *
-_hb_fallback_shaper_face_data_create (hb_face_t *face)
+_hb_fallback_shaper_face_data_create (hb_face_t *face HB_UNUSED)
 {
   return (hb_fallback_shaper_face_data_t *) HB_SHAPER_DATA_SUCCEEDED;
 }
 
 void
-_hb_fallback_shaper_face_data_destroy (hb_fallback_shaper_face_data_t *data)
+_hb_fallback_shaper_face_data_destroy (hb_fallback_shaper_face_data_t *data HB_UNUSED)
 {
 }
 
@@ -53,13 +53,13 @@ _hb_fallback_shaper_face_data_destroy (hb_fallback_shaper_face_data_t *data)
 struct hb_fallback_shaper_font_data_t {};
 
 hb_fallback_shaper_font_data_t *
-_hb_fallback_shaper_font_data_create (hb_font_t *font)
+_hb_fallback_shaper_font_data_create (hb_font_t *font HB_UNUSED)
 {
   return (hb_fallback_shaper_font_data_t *) HB_SHAPER_DATA_SUCCEEDED;
 }
 
 void
-_hb_fallback_shaper_font_data_destroy (hb_fallback_shaper_font_data_t *data)
+_hb_fallback_shaper_font_data_destroy (hb_fallback_shaper_font_data_t *data HB_UNUSED)
 {
 }
 
@@ -89,7 +89,7 @@ _hb_fallback_shaper_shape_plan_data_destroy (hb_fallback_shaper_shape_plan_data_
  */
 
 hb_bool_t
-_hb_fallback_shape (hb_shape_plan_t    *shape_plan,
+_hb_fallback_shape (hb_shape_plan_t    *shape_plan HB_UNUSED,
 		    hb_font_t          *font,
 		    hb_buffer_t        *buffer,
 		    const hb_feature_t *features HB_UNUSED,
diff --git a/src/hb-glib.cc b/src/hb-glib.cc
index 046275879..676e66016 100644
--- a/src/hb-glib.cc
+++ b/src/hb-glib.cc
@@ -334,7 +334,7 @@ hb_glib_unicode_decompose (hb_unicode_funcs_t *ufuncs HB_UNUSED,
 }
 
 static unsigned int
-hb_glib_unicode_decompose_compatibility (hb_unicode_funcs_t *ufuncs,
+hb_glib_unicode_decompose_compatibility (hb_unicode_funcs_t *ufuncs HB_UNUSED,
 					 hb_codepoint_t      u,
 					 hb_codepoint_t     *decomposed,
 					 void               *user_data HB_UNUSED)
diff --git a/src/hb-icu-le.cc b/src/hb-icu-le.cc
index 61099fedf..c05d330b9 100644
--- a/src/hb-icu-le.cc
+++ b/src/hb-icu-le.cc
@@ -43,13 +43,13 @@
 struct hb_icu_le_shaper_face_data_t {};
 
 hb_icu_le_shaper_face_data_t *
-_hb_icu_le_shaper_face_data_create (hb_face_t *face)
+_hb_icu_le_shaper_face_data_create (hb_face_t *face HB_UNUSED)
 {
   return (hb_icu_le_shaper_face_data_t *) HB_SHAPER_DATA_SUCCEEDED;
 }
 
 void
-_hb_icu_le_shaper_face_data_destroy (hb_icu_le_shaper_face_data_t *data)
+_hb_icu_le_shaper_face_data_destroy (hb_icu_le_shaper_face_data_t *data HB_UNUSED)
 {
 }
 
@@ -88,7 +88,7 @@ _hb_icu_le_shaper_font_data_destroy (hb_icu_le_shaper_font_data_t *data)
 struct hb_icu_le_shaper_shape_plan_data_t {};
 
 hb_icu_le_shaper_shape_plan_data_t *
-_hb_icu_le_shaper_shape_plan_data_create (hb_shape_plan_t    *shape_plan,
+_hb_icu_le_shaper_shape_plan_data_create (hb_shape_plan_t    *shape_plan HB_UNUSED,
 					  const hb_feature_t *user_features,
 					  unsigned int        num_user_features)
 {
diff --git a/src/hb-old.cc b/src/hb-old.cc
index 7c3e3702b..a7ea8ed9b 100644
--- a/src/hb-old.cc
+++ b/src/hb-old.cc
@@ -110,7 +110,7 @@ hb_old_getGlyphAdvances (HB_Font old_font,
 			 const HB_Glyph *glyphs,
 			 hb_uint32 numGlyphs,
 			 HB_Fixed *advances,
-			 int flags /*HB_ShaperFlag*/)
+			 int flags /*HB_ShaperFlag*/ HB_UNUSED)
 {
   hb_font_t *font = (hb_font_t *) old_font->userData;
 
@@ -251,15 +251,15 @@ _hb_old_shaper_font_data_destroy (hb_old_shaper_font_data_t *data)
 struct hb_old_shaper_shape_plan_data_t {};
 
 hb_old_shaper_shape_plan_data_t *
-_hb_old_shaper_shape_plan_data_create (hb_shape_plan_t    *shape_plan,
-				       const hb_feature_t *user_features,
-				       unsigned int        num_user_features)
+_hb_old_shaper_shape_plan_data_create (hb_shape_plan_t    *shape_plan HB_UNUSED,
+				       const hb_feature_t *user_features HB_UNUSED,
+				       unsigned int        num_user_features HB_UNUSED)
 {
   return (hb_old_shaper_shape_plan_data_t *) HB_SHAPER_DATA_SUCCEEDED;
 }
 
 void
-_hb_old_shaper_shape_plan_data_destroy (hb_old_shaper_shape_plan_data_t *data)
+_hb_old_shaper_shape_plan_data_destroy (hb_old_shaper_shape_plan_data_t *data HB_UNUSED)
 {
 }
 
@@ -269,7 +269,7 @@ _hb_old_shaper_shape_plan_data_destroy (hb_old_shaper_shape_plan_data_t *data)
  */
 
 hb_bool_t
-_hb_old_shape (hb_shape_plan_t    *shape_plan,
+_hb_old_shape (hb_shape_plan_t    *shape_plan HB_UNUSED,
 	       hb_font_t          *font,
 	       hb_buffer_t        *buffer,
 	       const hb_feature_t *features,
@@ -369,7 +369,7 @@ retry:
     *p = MIN (*p, buffer->info[i].cluster);
   }
   for (unsigned int i = 1; i < num_glyphs; i++)
-    if (vis_clusters[i] == -1)
+    if (vis_clusters[i] == (uint32_t) -1)
       vis_clusters[i] = vis_clusters[i - 1];
 
 #undef utf16_index
diff --git a/src/hb-open-type-private.hh b/src/hb-open-type-private.hh
index 2372235a5..e57558ea3 100644
--- a/src/hb-open-type-private.hh
+++ b/src/hb-open-type-private.hh
@@ -180,9 +180,7 @@ struct hb_sanitize_context_t
   template <typename T>
   inline return_t process (const T &obj) { return obj.sanitize (this); }
   static return_t default_return_value (void) { return true; }
-  bool stop_sublookup_iteration (const return_t r) const { return false; }
-  return_t recurse (unsigned int lookup_index)
-  { return default_return_value (); }
+  bool stop_sublookup_iteration (const return_t r HB_UNUSED) const { return false; }
 
   inline void init (hb_blob_t *b)
   {
diff --git a/src/hb-ot-layout-gsubgpos-private.hh b/src/hb-ot-layout-gsubgpos-private.hh
index d656999cd..87abd3b83 100644
--- a/src/hb-ot-layout-gsubgpos-private.hh
+++ b/src/hb-ot-layout-gsubgpos-private.hh
@@ -62,7 +62,7 @@ struct hb_closure_context_t
   template <typename T>
   inline return_t process (const T &obj) { obj.closure (this); return HB_VOID; }
   static return_t default_return_value (void) { return HB_VOID; }
-  bool stop_sublookup_iteration (const return_t r) const { return false; }
+  bool stop_sublookup_iteration (const return_t r HB_UNUSED) const { return false; }
   return_t recurse (unsigned int lookup_index)
   {
     if (unlikely (nesting_level_left == 0 || !recurse_func))
@@ -150,7 +150,7 @@ struct hb_collect_glyphs_context_t
   template <typename T>
   inline return_t process (const T &obj) { obj.collect_glyphs (this); return HB_VOID; }
   static return_t default_return_value (void) { return HB_VOID; }
-  bool stop_sublookup_iteration (const return_t r) const { return false; }
+  bool stop_sublookup_iteration (const return_t r HB_UNUSED) const { return false; }
   return_t recurse (unsigned int lookup_index)
   {
     if (unlikely (nesting_level_left == 0 || !recurse_func))
@@ -549,7 +549,7 @@ static inline void collect_coverage (hb_set_t *glyphs, const USHORT &value, cons
   const OffsetTo<Coverage> &coverage = (const OffsetTo<Coverage>&)value;
   (data+coverage).add_coverage (glyphs);
 }
-static inline void collect_array (hb_collect_glyphs_context_t *c,
+static inline void collect_array (hb_collect_glyphs_context_t *c HB_UNUSED,
 				  hb_set_t *glyphs,
 				  unsigned int count,
 				  const USHORT values[],
@@ -673,10 +673,10 @@ static inline bool match_input (hb_apply_context_t *c,
 }
 static inline void ligate_input (hb_apply_context_t *c,
 				 unsigned int count, /* Including the first glyph (not matched) */
-				 const USHORT input[], /* Array of input values--start with second glyph */
+				 const USHORT input[] HB_UNUSED, /* Array of input values--start with second glyph */
 				 hb_codepoint_t lig_glyph,
-				 match_func_t match_func,
-				 const void *match_data,
+				 match_func_t match_func HB_UNUSED,
+				 const void *match_data HB_UNUSED,
 				 bool is_mark_ligature,
 				 unsigned int total_component_count)
 {
@@ -939,8 +939,8 @@ static inline void context_collect_glyphs_lookup (hb_collect_glyphs_context_t *c
 static inline bool context_would_apply_lookup (hb_would_apply_context_t *c,
 					       unsigned int inputCount, /* Including the first glyph (not matched) */
 					       const USHORT input[], /* Array of input values--start with second glyph */
-					       unsigned int lookupCount,
-					       const LookupRecord lookupRecord[],
+					       unsigned int lookupCount HB_UNUSED,
+					       const LookupRecord lookupRecord[] HB_UNUSED,
 					       ContextApplyLookupContext &lookup_context)
 {
   return would_match_input (c,
@@ -1454,13 +1454,13 @@ static inline void chain_context_collect_glyphs_lookup (hb_collect_glyphs_contex
 
 static inline bool chain_context_would_apply_lookup (hb_would_apply_context_t *c,
 						     unsigned int backtrackCount,
-						     const USHORT backtrack[],
+						     const USHORT backtrack[] HB_UNUSED,
 						     unsigned int inputCount, /* Including the first glyph (not matched) */
 						     const USHORT input[], /* Array of input values--start with second glyph */
 						     unsigned int lookaheadCount,
-						     const USHORT lookahead[],
-						     unsigned int lookupCount,
-						     const LookupRecord lookupRecord[],
+						     const USHORT lookahead[] HB_UNUSED,
+						     unsigned int lookupCount HB_UNUSED,
+						     const LookupRecord lookupRecord[] HB_UNUSED,
 						     ChainContextApplyLookupContext &lookup_context)
 {
   return (c->zero_context ? !backtrackCount && !lookaheadCount : true)
diff --git a/src/hb-ot-shape-complex-arabic-fallback.hh b/src/hb-ot-shape-complex-arabic-fallback.hh
index bf68561e1..4fcd0a2fd 100644
--- a/src/hb-ot-shape-complex-arabic-fallback.hh
+++ b/src/hb-ot-shape-complex-arabic-fallback.hh
@@ -53,7 +53,7 @@ enum {
 };
 
 static OT::SubstLookup *
-arabic_fallback_synthesize_lookup_single (const hb_ot_shape_plan_t *plan,
+arabic_fallback_synthesize_lookup_single (const hb_ot_shape_plan_t *plan HB_UNUSED,
 					  hb_font_t *font,
 					  unsigned int feature_index)
 {
@@ -103,7 +103,7 @@ arabic_fallback_synthesize_lookup_single (const hb_ot_shape_plan_t *plan,
 }
 
 static OT::SubstLookup *
-arabic_fallback_synthesize_lookup_ligature (const hb_ot_shape_plan_t *plan,
+arabic_fallback_synthesize_lookup_ligature (const hb_ot_shape_plan_t *plan HB_UNUSED,
 					    hb_font_t *font)
 {
   OT::GlyphID first_glyphs[ARRAY_LENGTH_CONST (ligature_table)];
diff --git a/src/hb-ot-shape-complex-arabic.cc b/src/hb-ot-shape-complex-arabic.cc
index e9db00545..35356fe97 100644
--- a/src/hb-ot-shape-complex-arabic.cc
+++ b/src/hb-ot-shape-complex-arabic.cc
@@ -305,7 +305,7 @@ arabic_joining (hb_buffer_t *buffer)
 static void
 setup_masks_arabic (const hb_ot_shape_plan_t *plan,
 		    hb_buffer_t              *buffer,
-		    hb_font_t                *font)
+		    hb_font_t                *font HB_UNUSED)
 {
   const arabic_shape_plan_t *arabic_plan = (const arabic_shape_plan_t *) plan->data;
 
diff --git a/src/hb-ot-shape-complex-indic-machine.hh b/src/hb-ot-shape-complex-indic-machine.hh
index 1c0e7f224..f97ec52e6 100644
--- a/src/hb-ot-shape-complex-indic-machine.hh
+++ b/src/hb-ot-shape-complex-indic-machine.hh
@@ -1153,7 +1153,7 @@ static const int indic_syllable_machine_en_main = 143;
 static void
 find_syllables (hb_buffer_t *buffer)
 {
-  unsigned int p, pe, eof, ts, te, act;
+  unsigned int p, pe, eof, ts HB_UNUSED, te, act;
   int cs;
   hb_glyph_info_t *info = buffer->info;
   
diff --git a/src/hb-ot-shape-complex-indic-machine.rl b/src/hb-ot-shape-complex-indic-machine.rl
index a536da55c..5c73ebf7e 100644
--- a/src/hb-ot-shape-complex-indic-machine.rl
+++ b/src/hb-ot-shape-complex-indic-machine.rl
@@ -103,7 +103,7 @@ main := |*
 static void
 find_syllables (hb_buffer_t *buffer)
 {
-  unsigned int p, pe, eof, ts, te, act;
+  unsigned int p, pe, eof, ts HB_UNUSED, te, act;
   int cs;
   hb_glyph_info_t *info = buffer->info;
   %%{
diff --git a/src/hb-ot-shape-complex-indic.cc b/src/hb-ot-shape-complex-indic.cc
index d924d1a5a..466c18439 100644
--- a/src/hb-ot-shape-complex-indic.cc
+++ b/src/hb-ot-shape-complex-indic.cc
@@ -852,7 +852,7 @@ initial_reordering_syllable (const hb_ot_shape_plan_t *plan,
 }
 
 static inline void
-insert_dotted_circles (const hb_ot_shape_plan_t *plan,
+insert_dotted_circles (const hb_ot_shape_plan_t *plan HB_UNUSED,
 		       hb_font_t *font,
 		       hb_buffer_t *buffer)
 {
@@ -1246,7 +1246,7 @@ final_reordering_syllable (const hb_ot_shape_plan_t *plan,
 
 static void
 final_reordering (const hb_ot_shape_plan_t *plan,
-		  hb_font_t *font,
+		  hb_font_t *font HB_UNUSED,
 		  hb_buffer_t *buffer)
 {
   unsigned int count = buffer->len;
@@ -1273,7 +1273,7 @@ final_reordering (const hb_ot_shape_plan_t *plan,
 
 
 static hb_ot_shape_normalization_mode_t
-normalization_preference_indic (const hb_segment_properties_t *props)
+normalization_preference_indic (const hb_segment_properties_t *props HB_UNUSED)
 {
   return HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT;
 }
diff --git a/src/hb-ot-shape-complex-thai.cc b/src/hb-ot-shape-complex-thai.cc
index 076089181..24d476a0b 100644
--- a/src/hb-ot-shape-complex-thai.cc
+++ b/src/hb-ot-shape-complex-thai.cc
@@ -215,7 +215,7 @@ static const struct thai_below_state_machine_edge_t {
 
 
 static void
-do_thai_pua_shaping (const hb_ot_shape_plan_t *plan,
+do_thai_pua_shaping (const hb_ot_shape_plan_t *plan HB_UNUSED,
 		     hb_buffer_t              *buffer,
 		     hb_font_t                *font)
 {
diff --git a/src/hb-ot-shape-fallback.cc b/src/hb-ot-shape-fallback.cc
index f4463e4ee..6f3426e6b 100644
--- a/src/hb-ot-shape-fallback.cc
+++ b/src/hb-ot-shape-fallback.cc
@@ -161,8 +161,8 @@ recategorize_combining_class (hb_codepoint_t u,
 }
 
 void
-_hb_ot_shape_fallback_position_recategorize_marks (const hb_ot_shape_plan_t *plan,
-						   hb_font_t *font,
+_hb_ot_shape_fallback_position_recategorize_marks (const hb_ot_shape_plan_t *plan HB_UNUSED,
+						   hb_font_t *font HB_UNUSED,
 						   hb_buffer_t  *buffer)
 {
   unsigned int count = buffer->len;
diff --git a/src/hb-private.hh b/src/hb-private.hh
index 7824956e3..2fee6f8a4 100644
--- a/src/hb-private.hh
+++ b/src/hb-private.hh
@@ -82,7 +82,7 @@ static inline Type MAX (const Type &a, const Type &b) { return a > b ? a : b; }
 
 #undef  ARRAY_LENGTH
 template <typename Type, unsigned int n>
-static inline unsigned int ARRAY_LENGTH (const Type (&a)[n]) { return n; }
+static inline unsigned int ARRAY_LENGTH (const Type (&)[n]) { return n; }
 /* A const version, but does not detect erratically being called on pointers. */
 #define ARRAY_LENGTH_CONST(__array) ((signed int) (sizeof (__array) / sizeof (__array[0])))
 
@@ -680,7 +680,7 @@ struct hb_printer_t<bool> {
 
 template <>
 struct hb_printer_t<hb_void_t> {
-  const char *print (hb_void_t v) { return ""; }
+  const char *print (hb_void_t) { return ""; }
 };
 
 
@@ -696,7 +696,7 @@ static inline void _hb_warn_no_return (bool returned)
   }
 }
 template <>
-inline void _hb_warn_no_return<hb_void_t> (bool returned)
+inline void _hb_warn_no_return<hb_void_t> (bool returned HB_UNUSED)
 {}
 
 template <int max_level, typename ret_t>
@@ -755,7 +755,7 @@ struct hb_auto_trace_t<0, ret_t> {
 				   const char *message HB_UNUSED,
 				   ...) {}
 
-  inline ret_t ret (ret_t v, unsigned int line = 0) { return v; }
+  inline ret_t ret (ret_t v, unsigned int line HB_UNUSED = 0) { return v; }
 };
 
 #define TRACE_RETURN(RET) trace.ret (RET, __LINE__)
diff --git a/src/hb-ucdn.cc b/src/hb-ucdn.cc
index 35063043f..61e6ad362 100644
--- a/src/hb-ucdn.cc
+++ b/src/hb-ucdn.cc
@@ -129,57 +129,60 @@ static const hb_script_t ucdn_script_translate[] =
 
 static hb_unicode_combining_class_t
 hb_ucdn_combining_class(hb_unicode_funcs_t *ufuncs, hb_codepoint_t unicode,
-        void *user_data)
+			void *user_data HB_UNUSED)
 {
     return (hb_unicode_combining_class_t) ucdn_get_combining_class(unicode);
 }
 
 static unsigned int
 hb_ucdn_eastasian_width(hb_unicode_funcs_t *ufuncs, hb_codepoint_t unicode,
-        void *user_data)
+			void *user_data HB_UNUSED)
 {
     int w = ucdn_get_east_asian_width(unicode);
     return (w == UCDN_EAST_ASIAN_F || w == UCDN_EAST_ASIAN_W) ? 2 : 1;
 }
 
 static hb_unicode_general_category_t
-hb_ucdn_general_category(hb_unicode_funcs_t *ufuncs,
-        hb_codepoint_t unicode, void *user_data)
+hb_ucdn_general_category(hb_unicode_funcs_t *ufuncs, hb_codepoint_t unicode,
+			 void *user_data HB_UNUSED)
 {
     return (hb_unicode_general_category_t)ucdn_get_general_category(unicode);
 }
 
 static hb_codepoint_t
 hb_ucdn_mirroring(hb_unicode_funcs_t *ufuncs, hb_codepoint_t unicode,
-        void *user_data)
+		  void *user_data HB_UNUSED)
 {
     return ucdn_mirror(unicode);
 }
 
 static hb_script_t
 hb_ucdn_script(hb_unicode_funcs_t *ufuncs, hb_codepoint_t unicode,
-        void *user_data)
+	       void *user_data HB_UNUSED)
 {
     return ucdn_script_translate[ucdn_get_script(unicode)];
 }
 
 static hb_bool_t
-hb_ucdn_compose(hb_unicode_funcs_t *ufuncs, hb_codepoint_t a,
-        hb_codepoint_t b, hb_codepoint_t *ab, void *user_data)
+hb_ucdn_compose(hb_unicode_funcs_t *ufuncs,
+		hb_codepoint_t a, hb_codepoint_t b, hb_codepoint_t *ab,
+		void *user_data HB_UNUSED)
 {
     return ucdn_compose(ab, a, b);
 }
 
 static hb_bool_t
-hb_ucdn_decompose(hb_unicode_funcs_t *ufuncs, hb_codepoint_t ab,
-        hb_codepoint_t *a, hb_codepoint_t *b, void *user_data)
+hb_ucdn_decompose(hb_unicode_funcs_t *ufuncs,
+		  hb_codepoint_t ab, hb_codepoint_t *a, hb_codepoint_t *b,
+		  void *user_data HB_UNUSED)
 {
     return ucdn_decompose(ab, a, b);
 }
 
 static unsigned int
-hb_ucdn_decompose_compatibility(hb_unicode_funcs_t *ufuncs, hb_codepoint_t u,
-        hb_codepoint_t *decomposed, void *user_data)
+hb_ucdn_decompose_compatibility(hb_unicode_funcs_t *ufuncs,
+				hb_codepoint_t u, hb_codepoint_t *decomposed,
+				void *user_data HB_UNUSED)
 {
     return ucdn_compat_decompose(u, decomposed);
 }
diff --git a/src/hb-utf-private.hh b/src/hb-utf-private.hh
index ae36ef864..b9a6519d2 100644
--- a/src/hb-utf-private.hh
+++ b/src/hb-utf-private.hh
@@ -176,7 +176,7 @@ hb_utf_strlen (const uint16_t *text)
 
 static inline const uint32_t *
 hb_utf_next (const uint32_t *text,
-	     const uint32_t *end,
+	     const uint32_t *end HB_UNUSED,
 	     hb_codepoint_t *unicode)
 {
   *unicode = *text++;
@@ -185,7 +185,7 @@ hb_utf_next (const uint32_t *text,
 
 static inline const uint32_t *
 hb_utf_prev (const uint32_t *text,
-	     const uint32_t *start,
+	     const uint32_t *start HB_UNUSED,
 	     hb_codepoint_t *unicode)
 {
   *unicode = *--text;