Umm. Cryptic, yes

In file included from hb-face.cc:35:
hb-ot-cmap-table.hh: In member function 'void OT::CmapSubtableFormat4::_compiles_assertion_on_line_388() const':
hb-ot-cmap-table.hh:388: error: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:
hb-open-type.hh:354: note: candidate 1: const Type& OT::UnsizedArrayOf<Type>::operator[](unsigned int) const [with Type = OT::IntType<short unsigned int, 2u>]
hb-ot-cmap-table.hh:388: note: candidate 2: operator[](const T*, int) <built-in>
hb-ot-cmap-table.hh: In member function 'void OT::CmapSubtableFormat4::_instance_assertion_on_line_388() const':
hb-ot-cmap-table.hh:388: error: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:
hb-open-type.hh:354: note: candidate 1: const Type& OT::UnsizedArrayOf<Type>::operator[](unsigned int) const [with Type = OT::IntType<short unsigned int, 2u>]
hb-ot-cmap-table.hh:388: note: candidate 2: operator[](const T*, int) <built-in>
hb-face.cc: In function 'hb_blob_t* _hb_face_builder_data_reference_blob(hb_face_builder_data_t*)':
hb-face.cc:650: error: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:
hb-vector.hh:81: note: candidate 1: Type& hb_vector_t<Type, PreallocedCount>::operator[](unsigned int) [with Type = hb_face_builder_data_t::table_entry_t, unsigned int PreallocedCount = 32u]
hb-face.cc:650: note: candidate 2: operator[](T*, int) <built-in>
hb-face.cc:650: error: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:
hb-vector.hh:81: note: candidate 1: Type& hb_vector_t<Type, PreallocedCount>::operator[](unsigned int) [with Type = hb_face_builder_data_t::table_entry_t, unsigned int PreallocedCount = 32u]
hb-face.cc:650: note: candidate 2: operator[](const T*, int) <built-in>
hb-face.cc:651: error: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:
hb-vector.hh:81: note: candidate 1: Type& hb_vector_t<Type, PreallocedCount>::operator[](unsigned int) [with Type = hb_face_builder_data_t::table_entry_t, unsigned int PreallocedCount = 32u]
hb-face.cc:651: note: candidate 2: operator[](T*, int) <built-in>
hb-face.cc:651: error: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:
hb-vector.hh:81: note: candidate 1: Type& hb_vector_t<Type, PreallocedCount>::operator[](unsigned int) [with Type = hb_face_builder_data_t::table_entry_t, unsigned int PreallocedCount = 32u]
hb-face.cc:651: note: candidate 2: operator[](const T*, int) <built-in>

src/hb-face.cc

@@ -647,8 +647,8 @@ _hb_face_builder_data_reference_blob (hb_face_builder_data_t *data)
   bool is_cff = data->tables.lsearch (HB_TAG ('C','F','F',' ')) || data->tables.lsearch (HB_TAG ('C','F','F','2'));
   hb_tag_t sfnt_tag = is_cff ? OT::OpenTypeFontFile::CFFTag : OT::OpenTypeFontFile::TrueTypeTag;
 
-  Supplier<hb_tag_t>    tags_supplier  (&data->tables[0].tag, table_count, data->tables.item_size);
-  Supplier<hb_blob_t *> blobs_supplier (&data->tables[0].blob, table_count, data->tables.item_size);
+  Supplier<hb_tag_t>    tags_supplier  (&data->tables[0u].tag, table_count, data->tables.item_size);
+  Supplier<hb_blob_t *> blobs_supplier (&data->tables[0u].blob, table_count, data->tables.item_size);
   bool ret = f->serialize_single (&c,
 				  sfnt_tag,
 				  tags_supplier,

src/hb-machinery.hh

@@ -117,8 +117,8 @@ static inline Type& StructAfter(TObject &X)
   enum { min_size = (size) }
 
 #define DEFINE_SIZE_ARRAY(size, array) \
-  DEFINE_COMPILES_ASSERTION ((void) (array)[0].static_size) \
-  DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size) + VAR * sizeof ((array)[0])) \
+  DEFINE_COMPILES_ASSERTION ((void) (array)[0u].static_size) \
+  DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size) + VAR * sizeof ((array)[0u])) \
   enum { null_size = (size) }; \
   enum { min_size = (size) }