diff --git a/src/Makefile.sources b/src/Makefile.sources
index f178fa415..5824055b2 100644
--- a/src/Makefile.sources
+++ b/src/Makefile.sources
@@ -9,6 +9,7 @@ HB_BASE_sources = \
 	hb-buffer-serialize.cc \
 	hb-buffer.cc \
 	hb-common.cc \
+	hb-debug.hh \
 	hb-dsalgs.hh \
 	hb-face-private.hh \
 	hb-face.cc \
diff --git a/src/hb-blob.cc b/src/hb-blob.cc
index e390d7520..59c833363 100644
--- a/src/hb-blob.cc
+++ b/src/hb-blob.cc
@@ -30,6 +30,7 @@
 #endif
 
 #include "hb-private.hh"
+#include "hb-debug.hh"
 
 #include "hb-object-private.hh"
 
@@ -44,12 +45,6 @@
 #include <errno.h>
 
 
-
-#ifndef HB_DEBUG_BLOB
-#define HB_DEBUG_BLOB (HB_DEBUG+0)
-#endif
-
-
 struct hb_blob_t {
   hb_object_header_t header;
   ASSERT_POD ();
diff --git a/src/hb-coretext.cc b/src/hb-coretext.cc
index e27c2bade..90c9cd397 100644
--- a/src/hb-coretext.cc
+++ b/src/hb-coretext.cc
@@ -27,16 +27,14 @@
  */
 
 #define HB_SHAPER coretext
+
+#include "hb-private.hh"
+#include "hb-debug.hh"
 #include "hb-shaper-impl-private.hh"
 
 #include "hb-coretext.h"
 #include <math.h>
 
-
-#ifndef HB_DEBUG_CORETEXT
-#define HB_DEBUG_CORETEXT (HB_DEBUG+0)
-#endif
-
 /* https://developer.apple.com/documentation/coretext/1508745-ctfontcreatewithgraphicsfont */
 #define HB_CORETEXT_DEFAULT_FONT_SIZE 12.f
 
diff --git a/src/hb-debug.hh b/src/hb-debug.hh
new file mode 100644
index 000000000..c8cbee429
--- /dev/null
+++ b/src/hb-debug.hh
@@ -0,0 +1,383 @@
+/*
+ * Copyright © 2017  Google, Inc.
+ *
+ *  This is part of HarfBuzz, a text shaping library.
+ *
+ * Permission is hereby granted, without written agreement and without
+ * license or royalty fees, to use, copy, modify, and distribute this
+ * software and its documentation for any purpose, provided that the
+ * above copyright notice and the following two paragraphs appear in
+ * all copies of this software.
+ *
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
+ * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
+ * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ *
+ * Google Author(s): Behdad Esfahbod
+ */
+
+#ifndef HB_DEBUG_HH
+#define HB_DEBUG_HH
+
+#include "hb-private.hh"
+
+
+#ifndef HB_DEBUG
+#define HB_DEBUG 0
+#endif
+
+static inline bool
+_hb_debug (unsigned int level,
+	   unsigned int max_level)
+{
+  return level < max_level;
+}
+
+#define DEBUG_LEVEL_ENABLED(WHAT, LEVEL) (_hb_debug ((LEVEL), HB_DEBUG_##WHAT))
+#define DEBUG_ENABLED(WHAT) (DEBUG_LEVEL_ENABLED (WHAT, 0))
+
+static inline void
+_hb_print_func (const char *func)
+{
+  if (func)
+  {
+    unsigned int func_len = strlen (func);
+    /* Skip "static" */
+    if (0 == strncmp (func, "static ", 7))
+      func += 7;
+    /* Skip "typename" */
+    if (0 == strncmp (func, "typename ", 9))
+      func += 9;
+    /* Skip return type */
+    const char *space = strchr (func, ' ');
+    if (space)
+      func = space + 1;
+    /* Skip parameter list */
+    const char *paren = strchr (func, '(');
+    if (paren)
+      func_len = paren - func;
+    fprintf (stderr, "%.*s", func_len, func);
+  }
+}
+
+template <int max_level> static inline void
+_hb_debug_msg_va (const char *what,
+		  const void *obj,
+		  const char *func,
+		  bool indented,
+		  unsigned int level,
+		  int level_dir,
+		  const char *message,
+		  va_list ap) HB_PRINTF_FUNC(7, 0);
+template <int max_level> static inline void
+_hb_debug_msg_va (const char *what,
+		  const void *obj,
+		  const char *func,
+		  bool indented,
+		  unsigned int level,
+		  int level_dir,
+		  const char *message,
+		  va_list ap)
+{
+  if (!_hb_debug (level, max_level))
+    return;
+
+  fprintf (stderr, "%-10s", what ? what : "");
+
+  if (obj)
+    fprintf (stderr, "(%0*lx) ", (unsigned int) (2 * sizeof (void *)), (unsigned long) obj);
+  else
+    fprintf (stderr, " %*s  ", (unsigned int) (2 * sizeof (void *)), "");
+
+  if (indented) {
+#define VBAR	"\342\224\202"	/* U+2502 BOX DRAWINGS LIGHT VERTICAL */
+#define VRBAR	"\342\224\234"	/* U+251C BOX DRAWINGS LIGHT VERTICAL AND RIGHT */
+#define DLBAR	"\342\225\256"	/* U+256E BOX DRAWINGS LIGHT ARC DOWN AND LEFT */
+#define ULBAR	"\342\225\257"	/* U+256F BOX DRAWINGS LIGHT ARC UP AND LEFT */
+#define LBAR	"\342\225\264"	/* U+2574 BOX DRAWINGS LIGHT LEFT */
+    static const char bars[] =
+      VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR
+      VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR
+      VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR
+      VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR
+      VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR;
+    fprintf (stderr, "%2u %s" VRBAR "%s",
+	     level,
+	     bars + sizeof (bars) - 1 - MIN ((unsigned int) sizeof (bars) - 1, (unsigned int) (sizeof (VBAR) - 1) * level),
+	     level_dir ? (level_dir > 0 ? DLBAR : ULBAR) : LBAR);
+  } else
+    fprintf (stderr, "   " VRBAR LBAR);
+
+  _hb_print_func (func);
+
+  if (message)
+  {
+    fprintf (stderr, ": ");
+    vfprintf (stderr, message, ap);
+  }
+
+  fprintf (stderr, "\n");
+}
+template <> inline void
+_hb_debug_msg_va<0> (const char *what HB_UNUSED,
+		     const void *obj HB_UNUSED,
+		     const char *func HB_UNUSED,
+		     bool indented HB_UNUSED,
+		     unsigned int level HB_UNUSED,
+		     int level_dir HB_UNUSED,
+		     const char *message HB_UNUSED,
+		     va_list ap HB_UNUSED) {}
+
+template <int max_level> static inline void
+_hb_debug_msg (const char *what,
+	       const void *obj,
+	       const char *func,
+	       bool indented,
+	       unsigned int level,
+	       int level_dir,
+	       const char *message,
+	       ...) HB_PRINTF_FUNC(7, 8);
+template <int max_level> static inline void
+_hb_debug_msg (const char *what,
+	       const void *obj,
+	       const char *func,
+	       bool indented,
+	       unsigned int level,
+	       int level_dir,
+	       const char *message,
+	       ...)
+{
+  va_list ap;
+  va_start (ap, message);
+  _hb_debug_msg_va<max_level> (what, obj, func, indented, level, level_dir, message, ap);
+  va_end (ap);
+}
+template <> inline void
+_hb_debug_msg<0> (const char *what HB_UNUSED,
+		  const void *obj HB_UNUSED,
+		  const char *func HB_UNUSED,
+		  bool indented HB_UNUSED,
+		  unsigned int level HB_UNUSED,
+		  int level_dir HB_UNUSED,
+		  const char *message HB_UNUSED,
+		  ...) HB_PRINTF_FUNC(7, 8);
+template <> inline void
+_hb_debug_msg<0> (const char *what HB_UNUSED,
+		  const void *obj HB_UNUSED,
+		  const char *func HB_UNUSED,
+		  bool indented HB_UNUSED,
+		  unsigned int level HB_UNUSED,
+		  int level_dir HB_UNUSED,
+		  const char *message HB_UNUSED,
+		  ...) {}
+
+#define DEBUG_MSG_LEVEL(WHAT, OBJ, LEVEL, LEVEL_DIR, ...)	_hb_debug_msg<HB_DEBUG_##WHAT> (#WHAT, (OBJ), nullptr,    true, (LEVEL), (LEVEL_DIR), __VA_ARGS__)
+#define DEBUG_MSG(WHAT, OBJ, ...) 				_hb_debug_msg<HB_DEBUG_##WHAT> (#WHAT, (OBJ), nullptr,    false, 0, 0, __VA_ARGS__)
+#define DEBUG_MSG_FUNC(WHAT, OBJ, ...)				_hb_debug_msg<HB_DEBUG_##WHAT> (#WHAT, (OBJ), HB_FUNC, false, 0, 0, __VA_ARGS__)
+
+
+/*
+ * Printer
+ */
+
+template <typename T>
+struct hb_printer_t {
+  const char *print (const T&) { return "something"; }
+};
+
+template <>
+struct hb_printer_t<bool> {
+  const char *print (bool v) { return v ? "true" : "false"; }
+};
+
+template <>
+struct hb_printer_t<hb_void_t> {
+  const char *print (hb_void_t) { return ""; }
+};
+
+
+/*
+ * Trace
+ */
+
+template <typename T>
+static inline void _hb_warn_no_return (bool returned)
+{
+  if (unlikely (!returned)) {
+    fprintf (stderr, "OUCH, returned with no call to return_trace().  This is a bug, please report.\n");
+  }
+}
+template <>
+/*static*/ inline void _hb_warn_no_return<hb_void_t> (bool returned HB_UNUSED)
+{}
+
+template <int max_level, typename ret_t>
+struct hb_auto_trace_t {
+  explicit inline hb_auto_trace_t (unsigned int *plevel_,
+				   const char *what_,
+				   const void *obj_,
+				   const char *func,
+				   const char *message,
+				   ...) : plevel (plevel_), what (what_), obj (obj_), returned (false)
+  {
+    if (plevel) ++*plevel;
+
+    va_list ap;
+    va_start (ap, message);
+    _hb_debug_msg_va<max_level> (what, obj, func, true, plevel ? *plevel : 0, +1, message, ap);
+    va_end (ap);
+  }
+  inline ~hb_auto_trace_t (void)
+  {
+    _hb_warn_no_return<ret_t> (returned);
+    if (!returned) {
+      _hb_debug_msg<max_level> (what, obj, nullptr, true, plevel ? *plevel : 1, -1, " ");
+    }
+    if (plevel) --*plevel;
+  }
+
+  inline ret_t ret (ret_t v, unsigned int line = 0)
+  {
+    if (unlikely (returned)) {
+      fprintf (stderr, "OUCH, double calls to return_trace().  This is a bug, please report.\n");
+      return v;
+    }
+
+    _hb_debug_msg<max_level> (what, obj, nullptr, true, plevel ? *plevel : 1, -1,
+			      "return %s (line %d)",
+			      hb_printer_t<ret_t>().print (v), line);
+    if (plevel) --*plevel;
+    plevel = nullptr;
+    returned = true;
+    return v;
+  }
+
+  private:
+  unsigned int *plevel;
+  const char *what;
+  const void *obj;
+  bool returned;
+};
+template <typename ret_t> /* Optimize when tracing is disabled */
+struct hb_auto_trace_t<0, ret_t> {
+  explicit inline hb_auto_trace_t (unsigned int *plevel_ HB_UNUSED,
+				   const char *what HB_UNUSED,
+				   const void *obj HB_UNUSED,
+				   const char *func HB_UNUSED,
+				   const char *message HB_UNUSED,
+				   ...) {}
+
+  inline ret_t ret (ret_t v, unsigned int line HB_UNUSED = 0) { return v; }
+};
+
+#define return_trace(RET) return trace.ret (RET, __LINE__)
+
+
+/*
+ * Instances.
+ */
+
+#ifndef HB_DEBUG_ARABIC
+#define HB_DEBUG_ARABIC (HB_DEBUG+0)
+#endif
+
+#ifndef HB_DEBUG_BLOB
+#define HB_DEBUG_BLOB (HB_DEBUG+0)
+#endif
+
+#ifndef HB_DEBUG_CORETEXT
+#define HB_DEBUG_CORETEXT (HB_DEBUG+0)
+#endif
+
+#ifndef HB_DEBUG_DIRECTWRITE
+#define HB_DEBUG_DIRECTWRITE (HB_DEBUG+0)
+#endif
+
+#ifndef HB_DEBUG_FT
+#define HB_DEBUG_FT (HB_DEBUG+0)
+#endif
+
+#ifndef HB_DEBUG_GET_COVERAGE
+#define HB_DEBUG_GET_COVERAGE (HB_DEBUG+0)
+#endif
+
+#ifndef HB_DEBUG_OBJECT
+#define HB_DEBUG_OBJECT (HB_DEBUG+0)
+#endif
+
+#ifndef HB_DEBUG_SHAPE_PLAN
+#define HB_DEBUG_SHAPE_PLAN (HB_DEBUG+0)
+#endif
+
+#ifndef HB_DEBUG_UNISCRIBE
+#define HB_DEBUG_UNISCRIBE (HB_DEBUG+0)
+#endif
+
+/*
+ * With tracing.
+ */
+
+#ifndef HB_DEBUG_APPLY
+#define HB_DEBUG_APPLY (HB_DEBUG+0)
+#endif
+#define TRACE_APPLY(this) \
+	hb_auto_trace_t<HB_DEBUG_APPLY, bool> trace \
+	(&c->debug_depth, c->get_name (), this, HB_FUNC, \
+	 "idx %d gid %u lookup %d", \
+	 c->buffer->idx, c->buffer->cur().codepoint, (int) c->lookup_index);
+
+#ifndef HB_DEBUG_CLOSURE
+#define HB_DEBUG_CLOSURE (HB_DEBUG+0)
+#endif
+#define TRACE_CLOSURE(this) \
+	hb_auto_trace_t<HB_DEBUG_CLOSURE, hb_void_t> trace \
+	(&c->debug_depth, c->get_name (), this, HB_FUNC, \
+	 "");
+
+#ifndef HB_DEBUG_COLLECT_GLYPHS
+#define HB_DEBUG_COLLECT_GLYPHS (HB_DEBUG+0)
+#endif
+#define TRACE_COLLECT_GLYPHS(this) \
+	hb_auto_trace_t<HB_DEBUG_COLLECT_GLYPHS, hb_void_t> trace \
+	(&c->debug_depth, c->get_name (), this, HB_FUNC, \
+	 "");
+
+#ifndef HB_DEBUG_SANITIZE
+#define HB_DEBUG_SANITIZE (HB_DEBUG+0)
+#endif
+#define TRACE_SANITIZE(this) \
+	hb_auto_trace_t<HB_DEBUG_SANITIZE, bool> trace \
+	(&c->debug_depth, c->get_name (), this, HB_FUNC, \
+	 "");
+
+#ifndef HB_DEBUG_SERIALIZE
+#define HB_DEBUG_SERIALIZE (HB_DEBUG+0)
+#endif
+#define TRACE_SERIALIZE(this) \
+	hb_auto_trace_t<HB_DEBUG_SERIALIZE, bool> trace \
+	(&c->debug_depth, "SERIALIZE", c, HB_FUNC, \
+	 "");
+
+#ifndef HB_DEBUG_WOULD_APPLY
+#define HB_DEBUG_WOULD_APPLY (HB_DEBUG+0)
+#endif
+#define TRACE_WOULD_APPLY(this) \
+	hb_auto_trace_t<HB_DEBUG_WOULD_APPLY, bool> trace \
+	(&c->debug_depth, c->get_name (), this, HB_FUNC, \
+	 "%d glyphs", c->len);
+
+#define TRACE_DISPATCH(this, format) \
+	hb_auto_trace_t<context_t::max_debug_depth, typename context_t::return_t> trace \
+	(&c->debug_depth, c->get_name (), this, HB_FUNC, \
+	 "format %d", (int) format);
+
+
+#endif /* HB_DEBUG_HH */
diff --git a/src/hb-directwrite.cc b/src/hb-directwrite.cc
index a6693ef3a..25749de8c 100644
--- a/src/hb-directwrite.cc
+++ b/src/hb-directwrite.cc
@@ -22,6 +22,8 @@
  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
  */
 
+#include "hb-private.hh"
+#include "hb-debug.hh"
 #define HB_SHAPER directwrite
 #include "hb-shaper-impl-private.hh"
 
@@ -30,10 +32,6 @@
 #include "hb-directwrite.h"
 
 
-#ifndef HB_DEBUG_DIRECTWRITE
-#define HB_DEBUG_DIRECTWRITE (HB_DEBUG+0)
-#endif
-
 HB_SHAPER_DATA_ENSURE_DEFINE(directwrite, face)
 HB_SHAPER_DATA_ENSURE_DEFINE(directwrite, font)
 
diff --git a/src/hb-ft.cc b/src/hb-ft.cc
index 13f32142d..68c774547 100644
--- a/src/hb-ft.cc
+++ b/src/hb-ft.cc
@@ -28,6 +28,7 @@
  */
 
 #include "hb-private.hh"
+#include "hb-debug.hh"
 
 #include "hb-ft.h"
 
@@ -38,12 +39,6 @@
 #include FT_TRUETYPE_TABLES_H
 
 
-
-#ifndef HB_DEBUG_FT
-#define HB_DEBUG_FT (HB_DEBUG+0)
-#endif
-
-
 /* TODO:
  *
  * In general, this file does a fine job of what it's supposed to do.
diff --git a/src/hb-object-private.hh b/src/hb-object-private.hh
index 99fe646bd..0dada492c 100644
--- a/src/hb-object-private.hh
+++ b/src/hb-object-private.hh
@@ -33,18 +33,12 @@
 #define HB_OBJECT_PRIVATE_HH
 
 #include "hb-private.hh"
+#include "hb-debug.hh"
 
 #include "hb-atomic-private.hh"
 #include "hb-mutex-private.hh"
 
 
-/* Debug */
-
-#ifndef HB_DEBUG_OBJECT
-#define HB_DEBUG_OBJECT (HB_DEBUG+0)
-#endif
-
-
 /* reference_count */
 
 #define HB_REFERENCE_COUNT_UNCHANGABLE_VALUE	-0x53043
diff --git a/src/hb-open-type-private.hh b/src/hb-open-type-private.hh
index 90db791ee..b3169c040 100644
--- a/src/hb-open-type-private.hh
+++ b/src/hb-open-type-private.hh
@@ -30,6 +30,7 @@
 #define HB_OPEN_TYPE_PRIVATE_HH
 
 #include "hb-private.hh"
+#include "hb-debug.hh"
 #include "hb-face-private.hh"
 
 
@@ -174,16 +175,6 @@ struct hb_dispatch_context_t
  * Sanitize
  */
 
-#ifndef HB_DEBUG_SANITIZE
-#define HB_DEBUG_SANITIZE (HB_DEBUG+0)
-#endif
-
-
-#define TRACE_SANITIZE(this) \
-	hb_auto_trace_t<HB_DEBUG_SANITIZE, bool> trace \
-	(&c->debug_depth, c->get_name (), this, HB_FUNC, \
-	 "");
-
 /* This limits sanitizing time on really broken fonts. */
 #ifndef HB_SANITIZE_MAX_EDITS
 #define HB_SANITIZE_MAX_EDITS 32
@@ -387,16 +378,6 @@ struct Sanitizer
  * Serialize
  */
 
-#ifndef HB_DEBUG_SERIALIZE
-#define HB_DEBUG_SERIALIZE (HB_DEBUG+0)
-#endif
-
-
-#define TRACE_SERIALIZE(this) \
-	hb_auto_trace_t<HB_DEBUG_SERIALIZE, bool> trace \
-	(&c->debug_depth, "SERIALIZE", c, HB_FUNC, \
-	 "");
-
 
 struct hb_serialize_context_t
 {
diff --git a/src/hb-ot-layout-common-private.hh b/src/hb-ot-layout-common-private.hh
index ed18bd88f..8d881add5 100644
--- a/src/hb-ot-layout-common-private.hh
+++ b/src/hb-ot-layout-common-private.hh
@@ -29,6 +29,8 @@
 #ifndef HB_OT_LAYOUT_COMMON_PRIVATE_HH
 #define HB_OT_LAYOUT_COMMON_PRIVATE_HH
 
+#include "hb-private.hh"
+#include "hb-debug.hh"
 #include "hb-ot-layout-private.hh"
 #include "hb-open-type-private.hh"
 #include "hb-set-private.hh"
@@ -45,12 +47,6 @@
 namespace OT {
 
 
-#define TRACE_DISPATCH(this, format) \
-	hb_auto_trace_t<context_t::max_debug_depth, typename context_t::return_t> trace \
-	(&c->debug_depth, c->get_name (), this, HB_FUNC, \
-	 "format %d", (int) format);
-
-
 #define NOT_COVERED		((unsigned int) -1)
 
 
diff --git a/src/hb-ot-layout-gsubgpos-private.hh b/src/hb-ot-layout-gsubgpos-private.hh
index e695d7882..367b4d77a 100644
--- a/src/hb-ot-layout-gsubgpos-private.hh
+++ b/src/hb-ot-layout-gsubgpos-private.hh
@@ -29,6 +29,8 @@
 #ifndef HB_OT_LAYOUT_GSUBGPOS_PRIVATE_HH
 #define HB_OT_LAYOUT_GSUBGPOS_PRIVATE_HH
 
+#include "hb-private.hh"
+#include "hb-debug.hh"
 #include "hb-buffer-private.hh"
 #include "hb-ot-layout-gdef-table.hh"
 #include "hb-set-private.hh"
@@ -37,15 +39,6 @@
 namespace OT {
 
 
-#ifndef HB_DEBUG_CLOSURE
-#define HB_DEBUG_CLOSURE (HB_DEBUG+0)
-#endif
-
-#define TRACE_CLOSURE(this) \
-	hb_auto_trace_t<HB_DEBUG_CLOSURE, hb_void_t> trace \
-	(&c->debug_depth, c->get_name (), this, HB_FUNC, \
-	 "");
-
 struct hb_closure_context_t :
        hb_dispatch_context_t<hb_closure_context_t, hb_void_t, HB_DEBUG_CLOSURE>
 {
@@ -85,16 +78,6 @@ struct hb_closure_context_t :
 };
 
 
-
-#ifndef HB_DEBUG_WOULD_APPLY
-#define HB_DEBUG_WOULD_APPLY (HB_DEBUG+0)
-#endif
-
-#define TRACE_WOULD_APPLY(this) \
-	hb_auto_trace_t<HB_DEBUG_WOULD_APPLY, bool> trace \
-	(&c->debug_depth, c->get_name (), this, HB_FUNC, \
-	 "%d glyphs", c->len);
-
 struct hb_would_apply_context_t :
        hb_dispatch_context_t<hb_would_apply_context_t, bool, HB_DEBUG_WOULD_APPLY>
 {
@@ -122,16 +105,6 @@ struct hb_would_apply_context_t :
 };
 
 
-
-#ifndef HB_DEBUG_COLLECT_GLYPHS
-#define HB_DEBUG_COLLECT_GLYPHS (HB_DEBUG+0)
-#endif
-
-#define TRACE_COLLECT_GLYPHS(this) \
-	hb_auto_trace_t<HB_DEBUG_COLLECT_GLYPHS, hb_void_t> trace \
-	(&c->debug_depth, c->get_name (), this, HB_FUNC, \
-	 "");
-
 struct hb_collect_glyphs_context_t :
        hb_dispatch_context_t<hb_collect_glyphs_context_t, hb_void_t, HB_DEBUG_COLLECT_GLYPHS>
 {
@@ -219,10 +192,6 @@ struct hb_collect_glyphs_context_t :
 
 
 
-#ifndef HB_DEBUG_GET_COVERAGE
-#define HB_DEBUG_GET_COVERAGE (HB_DEBUG+0)
-#endif
-
 /* XXX Can we remove this? */
 
 template <typename set_t>
@@ -249,17 +218,6 @@ struct hb_add_coverage_context_t :
 };
 
 
-
-#ifndef HB_DEBUG_APPLY
-#define HB_DEBUG_APPLY (HB_DEBUG+0)
-#endif
-
-#define TRACE_APPLY(this) \
-	hb_auto_trace_t<HB_DEBUG_APPLY, bool> trace \
-	(&c->debug_depth, c->get_name (), this, HB_FUNC, \
-	 "idx %d gid %u lookup %d", \
-	 c->buffer->idx, c->buffer->cur().codepoint, (int) c->lookup_index);
-
 struct hb_apply_context_t :
        hb_dispatch_context_t<hb_apply_context_t, bool, HB_DEBUG_APPLY>
 {
diff --git a/src/hb-ot-shape-complex-arabic.cc b/src/hb-ot-shape-complex-arabic.cc
index a303fc138..283f325b4 100644
--- a/src/hb-ot-shape-complex-arabic.cc
+++ b/src/hb-ot-shape-complex-arabic.cc
@@ -24,15 +24,12 @@
  * Google Author(s): Behdad Esfahbod
  */
 
+#include "hb-private.hh"
+#include "hb-debug.hh"
 #include "hb-ot-shape-complex-arabic-private.hh"
 #include "hb-ot-shape-private.hh"
 
 
-#ifndef HB_DEBUG_ARABIC
-#define HB_DEBUG_ARABIC (HB_DEBUG+0)
-#endif
-
-
 /* buffer var allocations */
 #define arabic_shaping_action() complex_var_u8_0() /* arabic shaping action */
 
diff --git a/src/hb-private.hh b/src/hb-private.hh
index 4bda9be72..b6d13bd30 100644
--- a/src/hb-private.hh
+++ b/src/hb-private.hh
@@ -44,20 +44,14 @@
 #include <stddef.h>
 #include <string.h>
 #include <assert.h>
-
-/* We only use these two for debug output.  However, the debug code is
- * always seen by the compiler (and optimized out in non-debug builds.
- * If including these becomes a problem, we can start thinking about
- * someway around that. */
-#include <stdio.h>
 #include <errno.h>
+#include <stdio.h>
 #include <stdarg.h>
 
 
 #define HB_PASTE1(a,b) a##b
 #define HB_PASTE(a,b) HB_PASTE1(a,b)
 
-
 /* Compile-time custom allocator support. */
 
 #if defined(hb_malloc_impl) \
@@ -647,9 +641,6 @@ static inline unsigned char TOLOWER (unsigned char c)
 { return (c >= 'A' && c <= 'Z') ? c - 'A' + 'a' : c; }
 
 
-/* Debug */
-
-
 /* HB_NDEBUG disables some sanity checks that are very safe to disable and
  * should be disabled in production systems.  If NDEBUG is defined, enable
  * HB_NDEBUG; but if it's desirable that normal assert()s (which are very
@@ -659,255 +650,6 @@ static inline unsigned char TOLOWER (unsigned char c)
 #define HB_NDEBUG
 #endif
 
-#ifndef HB_DEBUG
-#define HB_DEBUG 0
-#endif
-
-static inline bool
-_hb_debug (unsigned int level,
-	   unsigned int max_level)
-{
-  return level < max_level;
-}
-
-#define DEBUG_LEVEL_ENABLED(WHAT, LEVEL) (_hb_debug ((LEVEL), HB_DEBUG_##WHAT))
-#define DEBUG_ENABLED(WHAT) (DEBUG_LEVEL_ENABLED (WHAT, 0))
-
-static inline void
-_hb_print_func (const char *func)
-{
-  if (func)
-  {
-    unsigned int func_len = strlen (func);
-    /* Skip "static" */
-    if (0 == strncmp (func, "static ", 7))
-      func += 7;
-    /* Skip "typename" */
-    if (0 == strncmp (func, "typename ", 9))
-      func += 9;
-    /* Skip return type */
-    const char *space = strchr (func, ' ');
-    if (space)
-      func = space + 1;
-    /* Skip parameter list */
-    const char *paren = strchr (func, '(');
-    if (paren)
-      func_len = paren - func;
-    fprintf (stderr, "%.*s", func_len, func);
-  }
-}
-
-template <int max_level> static inline void
-_hb_debug_msg_va (const char *what,
-		  const void *obj,
-		  const char *func,
-		  bool indented,
-		  unsigned int level,
-		  int level_dir,
-		  const char *message,
-		  va_list ap) HB_PRINTF_FUNC(7, 0);
-template <int max_level> static inline void
-_hb_debug_msg_va (const char *what,
-		  const void *obj,
-		  const char *func,
-		  bool indented,
-		  unsigned int level,
-		  int level_dir,
-		  const char *message,
-		  va_list ap)
-{
-  if (!_hb_debug (level, max_level))
-    return;
-
-  fprintf (stderr, "%-10s", what ? what : "");
-
-  if (obj)
-    fprintf (stderr, "(%0*lx) ", (unsigned int) (2 * sizeof (void *)), (unsigned long) obj);
-  else
-    fprintf (stderr, " %*s  ", (unsigned int) (2 * sizeof (void *)), "");
-
-  if (indented) {
-#define VBAR	"\342\224\202"	/* U+2502 BOX DRAWINGS LIGHT VERTICAL */
-#define VRBAR	"\342\224\234"	/* U+251C BOX DRAWINGS LIGHT VERTICAL AND RIGHT */
-#define DLBAR	"\342\225\256"	/* U+256E BOX DRAWINGS LIGHT ARC DOWN AND LEFT */
-#define ULBAR	"\342\225\257"	/* U+256F BOX DRAWINGS LIGHT ARC UP AND LEFT */
-#define LBAR	"\342\225\264"	/* U+2574 BOX DRAWINGS LIGHT LEFT */
-    static const char bars[] =
-      VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR
-      VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR
-      VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR
-      VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR
-      VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR VBAR;
-    fprintf (stderr, "%2u %s" VRBAR "%s",
-	     level,
-	     bars + sizeof (bars) - 1 - MIN ((unsigned int) sizeof (bars) - 1, (unsigned int) (sizeof (VBAR) - 1) * level),
-	     level_dir ? (level_dir > 0 ? DLBAR : ULBAR) : LBAR);
-  } else
-    fprintf (stderr, "   " VRBAR LBAR);
-
-  _hb_print_func (func);
-
-  if (message)
-  {
-    fprintf (stderr, ": ");
-    vfprintf (stderr, message, ap);
-  }
-
-  fprintf (stderr, "\n");
-}
-template <> inline void
-_hb_debug_msg_va<0> (const char *what HB_UNUSED,
-		     const void *obj HB_UNUSED,
-		     const char *func HB_UNUSED,
-		     bool indented HB_UNUSED,
-		     unsigned int level HB_UNUSED,
-		     int level_dir HB_UNUSED,
-		     const char *message HB_UNUSED,
-		     va_list ap HB_UNUSED) {}
-
-template <int max_level> static inline void
-_hb_debug_msg (const char *what,
-	       const void *obj,
-	       const char *func,
-	       bool indented,
-	       unsigned int level,
-	       int level_dir,
-	       const char *message,
-	       ...) HB_PRINTF_FUNC(7, 8);
-template <int max_level> static inline void
-_hb_debug_msg (const char *what,
-	       const void *obj,
-	       const char *func,
-	       bool indented,
-	       unsigned int level,
-	       int level_dir,
-	       const char *message,
-	       ...)
-{
-  va_list ap;
-  va_start (ap, message);
-  _hb_debug_msg_va<max_level> (what, obj, func, indented, level, level_dir, message, ap);
-  va_end (ap);
-}
-template <> inline void
-_hb_debug_msg<0> (const char *what HB_UNUSED,
-		  const void *obj HB_UNUSED,
-		  const char *func HB_UNUSED,
-		  bool indented HB_UNUSED,
-		  unsigned int level HB_UNUSED,
-		  int level_dir HB_UNUSED,
-		  const char *message HB_UNUSED,
-		  ...) HB_PRINTF_FUNC(7, 8);
-template <> inline void
-_hb_debug_msg<0> (const char *what HB_UNUSED,
-		  const void *obj HB_UNUSED,
-		  const char *func HB_UNUSED,
-		  bool indented HB_UNUSED,
-		  unsigned int level HB_UNUSED,
-		  int level_dir HB_UNUSED,
-		  const char *message HB_UNUSED,
-		  ...) {}
-
-#define DEBUG_MSG_LEVEL(WHAT, OBJ, LEVEL, LEVEL_DIR, ...)	_hb_debug_msg<HB_DEBUG_##WHAT> (#WHAT, (OBJ), nullptr,    true, (LEVEL), (LEVEL_DIR), __VA_ARGS__)
-#define DEBUG_MSG(WHAT, OBJ, ...) 				_hb_debug_msg<HB_DEBUG_##WHAT> (#WHAT, (OBJ), nullptr,    false, 0, 0, __VA_ARGS__)
-#define DEBUG_MSG_FUNC(WHAT, OBJ, ...)				_hb_debug_msg<HB_DEBUG_##WHAT> (#WHAT, (OBJ), HB_FUNC, false, 0, 0, __VA_ARGS__)
-
-
-/*
- * Printer
- */
-
-template <typename T>
-struct hb_printer_t {
-  const char *print (const T&) { return "something"; }
-};
-
-template <>
-struct hb_printer_t<bool> {
-  const char *print (bool v) { return v ? "true" : "false"; }
-};
-
-template <>
-struct hb_printer_t<hb_void_t> {
-  const char *print (hb_void_t) { return ""; }
-};
-
-
-/*
- * Trace
- */
-
-template <typename T>
-static inline void _hb_warn_no_return (bool returned)
-{
-  if (unlikely (!returned)) {
-    fprintf (stderr, "OUCH, returned with no call to return_trace().  This is a bug, please report.\n");
-  }
-}
-template <>
-/*static*/ inline void _hb_warn_no_return<hb_void_t> (bool returned HB_UNUSED)
-{}
-
-template <int max_level, typename ret_t>
-struct hb_auto_trace_t {
-  explicit inline hb_auto_trace_t (unsigned int *plevel_,
-				   const char *what_,
-				   const void *obj_,
-				   const char *func,
-				   const char *message,
-				   ...) : plevel (plevel_), what (what_), obj (obj_), returned (false)
-  {
-    if (plevel) ++*plevel;
-
-    va_list ap;
-    va_start (ap, message);
-    _hb_debug_msg_va<max_level> (what, obj, func, true, plevel ? *plevel : 0, +1, message, ap);
-    va_end (ap);
-  }
-  inline ~hb_auto_trace_t (void)
-  {
-    _hb_warn_no_return<ret_t> (returned);
-    if (!returned) {
-      _hb_debug_msg<max_level> (what, obj, nullptr, true, plevel ? *plevel : 1, -1, " ");
-    }
-    if (plevel) --*plevel;
-  }
-
-  inline ret_t ret (ret_t v, unsigned int line = 0)
-  {
-    if (unlikely (returned)) {
-      fprintf (stderr, "OUCH, double calls to return_trace().  This is a bug, please report.\n");
-      return v;
-    }
-
-    _hb_debug_msg<max_level> (what, obj, nullptr, true, plevel ? *plevel : 1, -1,
-			      "return %s (line %d)",
-			      hb_printer_t<ret_t>().print (v), line);
-    if (plevel) --*plevel;
-    plevel = nullptr;
-    returned = true;
-    return v;
-  }
-
-  private:
-  unsigned int *plevel;
-  const char *what;
-  const void *obj;
-  bool returned;
-};
-template <typename ret_t> /* Optimize when tracing is disabled */
-struct hb_auto_trace_t<0, ret_t> {
-  explicit inline hb_auto_trace_t (unsigned int *plevel_ HB_UNUSED,
-				   const char *what HB_UNUSED,
-				   const void *obj HB_UNUSED,
-				   const char *func HB_UNUSED,
-				   const char *message HB_UNUSED,
-				   ...) {}
-
-  inline ret_t ret (ret_t v, unsigned int line HB_UNUSED = 0) { return v; }
-};
-
-#define return_trace(RET) return trace.ret (RET, __LINE__)
 
 /* Misc */
 
diff --git a/src/hb-shape-plan.cc b/src/hb-shape-plan.cc
index e58f9ff80..6eeba2b3d 100644
--- a/src/hb-shape-plan.cc
+++ b/src/hb-shape-plan.cc
@@ -24,17 +24,14 @@
  * Google Author(s): Behdad Esfahbod
  */
 
+#include "hb-private.hh"
+#include "hb-debug.hh"
 #include "hb-shape-plan-private.hh"
 #include "hb-shaper-private.hh"
 #include "hb-font-private.hh"
 #include "hb-buffer-private.hh"
 
 
-#ifndef HB_DEBUG_SHAPE_PLAN
-#define HB_DEBUG_SHAPE_PLAN (HB_DEBUG+0)
-#endif
-
-
 static void
 hb_shape_plan_plan (hb_shape_plan_t    *shape_plan,
 		    const hb_feature_t *user_features,
diff --git a/src/hb-uniscribe.cc b/src/hb-uniscribe.cc
index b28e7f043..484134570 100644
--- a/src/hb-uniscribe.cc
+++ b/src/hb-uniscribe.cc
@@ -24,6 +24,8 @@
  * Google Author(s): Behdad Esfahbod
  */
 
+#include "hb-private.hh"
+#include "hb-debug.hh"
 #define HB_SHAPER uniscribe
 #include "hb-shaper-impl-private.hh"
 
@@ -38,11 +40,6 @@
 #include "hb-ot-tag.h"
 
 
-#ifndef HB_DEBUG_UNISCRIBE
-#define HB_DEBUG_UNISCRIBE (HB_DEBUG+0)
-#endif
-
-
 static inline uint16_t hb_uint16_swap (const uint16_t v)
 { return (v >> 8) | (v << 8); }
 static inline uint32_t hb_uint32_swap (const uint32_t v)