re-implement Tail; rewrote name table with it

src/hb-open-type.hh

@@ -338,6 +338,30 @@ struct OffsetTo : Offset<OffsetType, has_null>
   }
 
   /* TODO: Somehow merge this with previous function into a serialize_dispatch(). */
+  /* Workaround clang bug: https://bugs.llvm.org/show_bug.cgi?id=23029
+   * Can't compile: whence = hb_serialize_context_t::Head followed by Ts&&...
+   */
+  template <typename ...Ts>
+  bool serialize_copy (hb_serialize_context_t *c,
+		       const OffsetTo& src,
+		       const void *src_base,
+		       const void *dst_base,
+		       hb_serialize_context_t::whence_t whence,
+		       Ts&&... ds)
+  {
+    *this = 0;
+    if (src.is_null ())
+      return false;
+
+    c->push ();
+
+    bool ret = c->copy (src_base+src, hb_forward<Ts> (ds)...);
+
+    c->add_link (*this, c->pop_pack (), dst_base, whence);
+
+    return ret;
+  }
+
   template <typename ...Ts>
   bool serialize_copy (hb_serialize_context_t *c,
 		       const OffsetTo& src,

src/hb-ot-name-table.hh

@@ -98,13 +98,12 @@ struct NameRecord
   }
 
   NameRecord* copy (hb_serialize_context_t *c,
-		    const void *src_base,
-		    const void *dst_base) const
+		    const void *src_base) const
   {
     TRACE_SERIALIZE (this);
     auto *out = c->embed (this);
     if (unlikely (!out)) return_trace (nullptr);
-    out->offset.serialize_copy (c, offset, src_base, dst_base, length);
+    out->offset.serialize_copy (c, offset, src_base, nullptr, hb_serialize_context_t::Tail, length);
     return_trace (out);
   }
 
@@ -216,13 +215,6 @@ struct name
     this->format = 0;
     this->count = it.len ();
 
-    auto snap = c->snapshot ();
-    this->nameRecordZ.serialize (c, this->count);
-    if (unlikely (!c->check_assign (this->stringOffset, c->length ()))) return_trace (false);
-    c->revert (snap);
-
-    const void *dst_string_pool = &(this + this->stringOffset);
-
     NameRecord *name_records = (NameRecord *) calloc (it.len (), NameRecord::static_size);
     hb_array_t<NameRecord> records (name_records, it.len ());
 
@@ -234,12 +226,12 @@ struct name
 
     records.qsort ();
 
-    c->copy_all (records, src_string_pool, dst_string_pool);
+    c->copy_all (records, src_string_pool);
     free (records.arrayZ);
 
     if (unlikely (c->ran_out_of_room)) return_trace (false);
 
-    assert (this->stringOffset == c->length ());
+    this->stringOffset = c->length ();
 
     return_trace (true);
   }

src/hb-serialize.hh

@@ -50,6 +50,12 @@ struct hb_serialize_context_t
     char *head, *tail;
   };
 
+  enum whence_t {
+     Head,	/* Relative to the current object head (default). */
+     Tail,	/* Relative to the current object tail after packed. */
+     Absolute	/* Absolute: from the start of the serialize buffer. */
+   };
+
   struct object_t : range_t
   {
     void fini () { links.fini (); }
@@ -71,7 +77,7 @@ struct hb_serialize_context_t
     {
       bool is_wide: 1;
       bool is_signed: 1;
-      bool is_absolute: 1;
+      whence_t whence: 2;
       unsigned position: 29;
       unsigned bias;
       objidx_t objidx;
@@ -270,16 +276,10 @@ struct hb_serialize_context_t
       assert (packed.tail ()->head == tail);
   }
 
-  enum base_mode_t {
-     Head,	/* Relative to the current object head (default). */
-     Tail,	/* Relative to the current object tail. */
-     Absolute	/* Absolute: from the start of the serialize buffer. */
-   };
-
   template <typename T>
   void add_link (T &ofs, objidx_t objidx,
 		 const void *base = nullptr,
-		 base_mode_t mode = Head)
+		 whence_t whence = Head)
   {
     static_assert (sizeof (T) == 2 || sizeof (T) == 4, "");
 
@@ -289,34 +289,19 @@ struct hb_serialize_context_t
     assert (current);
     assert (current->head <= (const char *) &ofs);
 
-    const char  *dflt_base;
     auto& link = *current->links.push ();
 
-    switch (mode)
-    {
-    case Head:
-      dflt_base = current->head;
-      link.is_absolute = false;
-      break;
-    case Tail:
-      dflt_base = current->tail;
-      link.is_absolute = false;
-      break;
-    case Absolute:
-      dflt_base = start;
-      link.is_absolute = true;
-      break;
-    default: return;
-    }
-    if (!base)
-      base = dflt_base;
-    else
-      assert (dflt_base <= (const char *) base);
-
     link.is_wide = sizeof (T) == 4;
     link.is_signed = hb_is_signed (hb_unwrap_type (T));
+    link.whence = whence;
     link.position = (const char *) &ofs - current->head;
-    link.bias = (const char *) base - dflt_base;
+    if (whence == Head)
+    {
+      assert (current->head <= (const char *)base);
+      link.bias = (const char *) base - current->head;
+    }
+    else
+      link.bias = 0;
     link.objidx = objidx;
   }
 
@@ -333,12 +318,11 @@ struct hb_serialize_context_t
 	const object_t* child = packed[link.objidx];
 	if (unlikely (!child)) { err_other_error(); return; }
 	unsigned offset;
-	if (link.is_absolute)
-	  offset = (head - start) + (child->head - tail);
-	else
-	{
-	  assert (link.bias <= (size_t) (parent->tail - parent->head));
-	  offset = (child->head - parent->head) - link.bias;
+	switch (link.whence) {
+	case Head:     offset = child->head - parent->head; break;
+	case Tail:     offset = child->head - parent->tail; break;
+	case Absolute: offset = (head - start) + (child->head - tail); break;
+	default: assert (0);
 	}
 
 	if (link.is_signed)