bug 670901 pt 1 - add support for an error-message callback to OTS. r=jdaggett

gfx/ots/include/opentype-sanitiser.h

@@ -199,6 +199,13 @@ class OTSStream {
   unsigned chksum_buffer_offset_;
 };
 
+#ifdef MOZ_OTS_REPORT_ERRORS
+// Signature of the function to be provided by the client in order to report errors.
+// The return type is a boolean so that it can be used within an expression,
+// but the actual value is ignored. (Suggested convention is to always return 'false'.)
+typedef bool (*MessageFunc)(void *user_data, const char *format, ...);
+#endif
+
 // -----------------------------------------------------------------------------
 // Process a given OpenType file and write out a sanitised version
 //   output: a pointer to an object implementing the OTSStream interface. The
@@ -209,6 +216,9 @@ class OTSStream {
 //   preserve_graphite_tables: whether to preserve Graphite Layout tables
 // -----------------------------------------------------------------------------
 bool OTS_API Process(OTSStream *output, const uint8_t *input, size_t length,
+#ifdef MOZ_OTS_REPORT_ERRORS
+                     MessageFunc message_func, void *user_data,
+#endif
                      bool preserve_graphite_tables = false);
 
 // Force to disable debug output even when the library is compiled with

gfx/ots/src/gdef.cc

@@ -15,6 +15,8 @@
 // GDEF - The Glyph Definition Table
 // http://www.microsoft.com/typography/otspec/gdef.htm
 
+#define TABLE_NAME "GDEF"
+
 namespace {
 
 // The maximum class value in class definition tables.
@@ -242,7 +244,11 @@ bool ParseMarkGlyphSetsDefTable(ots::OpenTypeFile *file, const uint8_t *data,
 }  // namespace
 
 #define DROP_THIS_TABLE \
-  do { file->gdef->data = 0; file->gdef->length = 0; } while (0)
+  do { \
+    file->gdef->data = 0; \
+    file->gdef->length = 0; \
+    OTS_FAILURE_MSG("OpenType layout data discarded"); \
+  } while (0)
 
 namespace ots {
 

gfx/ots/src/gpos.cc

@@ -15,6 +15,8 @@
 // GPOS - The Glyph Positioning Table
 // http://www.microsoft.com/typography/otspec/gpos.htm
 
+#define TABLE_NAME "GPOS"
+
 namespace {
 
 enum GPOS_TYPE {
@@ -669,7 +671,11 @@ bool ParseExtensionPositioning(const ots::OpenTypeFile *file,
 }  // namespace
 
 #define DROP_THIS_TABLE \
-  do { file->gpos->data = 0; file->gpos->length = 0; } while (0)
+  do { \
+    file->gpos->data = 0; \
+    file->gpos->length = 0; \
+    OTS_FAILURE_MSG("OpenType layout data discarded"); \
+  } while (0)
 
 namespace ots {
 

gfx/ots/src/gsub.cc

@@ -15,6 +15,8 @@
 // GSUB - The Glyph Substitution Table
 // http://www.microsoft.com/typography/otspec/gsub.htm
 
+#define TABLE_NAME "GSUB"
+
 namespace {
 
 // The GSUB header size
@@ -529,7 +531,11 @@ bool ParseReverseChainingContextSingleSubstitution(
 }  // namespace
 
 #define DROP_THIS_TABLE \
-  do { file->gsub->data = 0; file->gsub->length = 0; } while (0)
+  do { \
+    file->gsub->data = 0; \
+    file->gsub->length = 0; \
+    OTS_FAILURE_MSG("OpenType layout data discarded"); \
+  } while (0)
 
 namespace ots {
 

gfx/ots/src/ots.cc

@@ -21,6 +21,20 @@ namespace {
 
 bool g_debug_output = true;
 
+#ifdef MOZ_OTS_REPORT_ERRORS
+
+// Generate a message with or without a table tag, when 'header' is the OpenTypeFile pointer
+#define OTS_FAILURE_MSG_TAG(msg_,tag_) OTS_FAILURE_MSG_TAG_(header, msg_, tag_)
+#define OTS_FAILURE_MSG_HDR(msg_)      OTS_FAILURE_MSG_(header, msg_)
+
+#else
+
+#define OTS_FAILURE_MSG_TAG(msg_,tag_) OTS_FAILURE()
+#define OTS_FAILURE_MSG_HDR(msg_)      OTS_FAILURE()
+
+#endif
+
+
 struct OpenTypeTable {
   uint32_t tag;
   uint32_t chksum;
@@ -182,27 +196,27 @@ bool ProcessTTF(ots::OpenTypeFile *header,
 
   // we disallow all files > 1GB in size for sanity.
   if (length > 1024 * 1024 * 1024) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("file exceeds 1GB");
   }
 
   if (!file.ReadTag(&header->version)) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("error reading version tag");
   }
   if (!IsValidVersionTag(header->version)) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_HDR("invalid version tag");
   }
 
   if (!file.ReadU16(&header->num_tables) ||
       !file.ReadU16(&header->search_range) ||
       !file.ReadU16(&header->entry_selector) ||
       !file.ReadU16(&header->range_shift)) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("error reading table directory search header");
   }
 
   // search_range is (Maximum power of 2 <= numTables) x 16. Thus, to avoid
   // overflow num_tables is, at most, 2^16 / 16 = 2^12
   if (header->num_tables >= 4096 || header->num_tables < 1) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("excessive (or zero) number of tables");
   }
 
   unsigned max_pow2 = 0;
@@ -220,7 +234,7 @@ bool ProcessTTF(ots::OpenTypeFile *header,
 
   // entry_selector is Log2(maximum power of 2 <= numTables)
   if (header->entry_selector != max_pow2) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("incorrect entrySelector for table directory");
   }
 
   // range_shift is NumTables x 16-searchRange. We know that 16*num_tables
@@ -242,7 +256,7 @@ bool ProcessTTF(ots::OpenTypeFile *header,
         !file.ReadU32(&table.chksum) ||
         !file.ReadU32(&table.offset) ||
         !file.ReadU32(&table.length)) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_HDR("error reading table directory");
     }
 
     table.uncompressed_length = table.length;
@@ -258,23 +272,23 @@ bool ProcessWOFF(ots::OpenTypeFile *header,
 
   // we disallow all files > 1GB in size for sanity.
   if (length > 1024 * 1024 * 1024) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("file exceeds 1GB");
   }
 
   uint32_t woff_tag;
   if (!file.ReadTag(&woff_tag)) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("error reading WOFF marker");
   }
 
   if (woff_tag != Tag("wOFF")) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("invalid WOFF marker");
   }
 
   if (!file.ReadTag(&header->version)) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("error reading version tag");
   }
   if (!IsValidVersionTag(header->version)) {
-      return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("invalid version tag");
   }
 
   header->search_range = 0;
@@ -283,27 +297,27 @@ bool ProcessWOFF(ots::OpenTypeFile *header,
 
   uint32_t reported_length;
   if (!file.ReadU32(&reported_length) || length != reported_length) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("incorrect file size in WOFF header");
   }
 
   if (!file.ReadU16(&header->num_tables) || !header->num_tables) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("error reading number of tables");
   }
 
   uint16_t reserved_value;
   if (!file.ReadU16(&reserved_value) || reserved_value) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("error in reserved field of WOFF header");
   }
 
   uint32_t reported_total_sfnt_size;
   if (!file.ReadU32(&reported_total_sfnt_size)) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("error reading total sfnt size");
   }
 
   // We don't care about these fields of the header:
   //   uint16_t major_version, minor_version
   if (!file.Skip(2 * 2)) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("error skipping WOFF header fields");
   }
 
   // Checks metadata block size.
@@ -313,11 +327,11 @@ bool ProcessWOFF(ots::OpenTypeFile *header,
   if (!file.ReadU32(&meta_offset) ||
       !file.ReadU32(&meta_length) ||
       !file.ReadU32(&meta_length_orig)) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("error reading WOFF header fields");
   }
   if (meta_offset) {
     if (meta_offset >= length || length - meta_offset < meta_length) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_HDR("invalid metadata block location/size");
     }
   }
 
@@ -326,11 +340,11 @@ bool ProcessWOFF(ots::OpenTypeFile *header,
   uint32_t priv_length;
   if (!file.ReadU32(&priv_offset) ||
       !file.ReadU32(&priv_length)) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("error reading WOFF header fields");
   }
   if (priv_offset) {
     if (priv_offset >= length || length - priv_offset < priv_length) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_HDR("invalid private block location/size");
     }
   }
 
@@ -348,12 +362,12 @@ bool ProcessWOFF(ots::OpenTypeFile *header,
         !file.ReadU32(&table.length) ||
         !file.ReadU32(&table.uncompressed_length) ||
         !file.ReadU32(&table.chksum)) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_HDR("error reading table directory");
     }
 
     total_sfnt_size += Round4(table.uncompressed_length);
     if (total_sfnt_size > std::numeric_limits<uint32_t>::max()) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_HDR("sfnt size overflow");
     }
     tables.push_back(table);
     if (i == 0 || tables[first_index].offset > table.offset)
@@ -363,17 +377,17 @@ bool ProcessWOFF(ots::OpenTypeFile *header,
   }
 
   if (reported_total_sfnt_size != total_sfnt_size) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("uncompressed sfnt size mismatch");
   }
 
   // Table data must follow immediately after the header.
   if (tables[first_index].offset != Round4(file.offset())) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("junk before tables in WOFF file");
   }
 
   if (tables[last_index].offset >= length ||
       length - tables[last_index].offset < tables[last_index].length) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("invalid table location/size");
   }
   // Blocks must follow immediately after the previous block.
   // (Except for padding with a maximum of three null bytes)
@@ -381,30 +395,30 @@ bool ProcessWOFF(ots::OpenTypeFile *header,
       static_cast<uint64_t>(tables[last_index].offset) +
       static_cast<uint64_t>(tables[last_index].length));
   if (block_end > std::numeric_limits<uint32_t>::max()) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("invalid table location/size");
   }
   if (meta_offset) {
     if (block_end != meta_offset) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_HDR("invalid metadata block location");
     }
     block_end = Round4(static_cast<uint64_t>(meta_offset) +
                        static_cast<uint64_t>(meta_length));
     if (block_end > std::numeric_limits<uint32_t>::max()) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_HDR("invalid metadata block size");
     }
   }
   if (priv_offset) {
     if (block_end != priv_offset) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_HDR("invalid private block location");
     }
     block_end = Round4(static_cast<uint64_t>(priv_offset) +
                        static_cast<uint64_t>(priv_length));
     if (block_end > std::numeric_limits<uint32_t>::max()) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_HDR("invalid private block size");
     }
   }
   if (block_end != Round4(length)) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("file length mismatch (trailing junk?)");
   }
 
   return ProcessGeneric(header, output, data, length, tables, file);
@@ -425,46 +439,46 @@ bool ProcessGeneric(ots::OpenTypeFile *header, ots::OTSStream *output,
       const uint32_t this_tag = ntohl(tables[i].tag);
       const uint32_t prev_tag = ntohl(tables[i - 1].tag);
       if (this_tag <= prev_tag) {
-        return OTS_FAILURE();
+        return OTS_FAILURE_MSG_HDR("table directory not correctly ordered");
       }
     }
 
     // all tag names must be built from printable ASCII characters
     if (!CheckTag(tables[i].tag)) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_TAG("invalid table tag", &tables[i].tag);
     }
 
     // tables must be 4-byte aligned
     if (tables[i].offset & 3) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_TAG("misaligned table", &tables[i].tag);
     }
 
     // and must be within the file
     if (tables[i].offset < data_offset || tables[i].offset >= length) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_TAG("invalid table offset", &tables[i].tag);
     }
     // disallow all tables with a zero length
     if (tables[i].length < 1) {
       // Note: malayalam.ttf has zero length CVT table...
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_TAG("zero-length table", &tables[i].tag);
     }
     // disallow all tables with a length > 1GB
     if (tables[i].length > 1024 * 1024 * 1024) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_TAG("table length exceeds 1GB", &tables[i].tag);
     }
     // disallow tables where the uncompressed size is < the compressed size.
     if (tables[i].uncompressed_length < tables[i].length) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_TAG("invalid compressed table", &tables[i].tag);
     }
     if (tables[i].uncompressed_length > tables[i].length) {
       // We'll probably be decompressing this table.
 
       // disallow all tables which uncompress to > 30 MB
       if (tables[i].uncompressed_length > 30 * 1024 * 1024) {
-        return OTS_FAILURE();
+        return OTS_FAILURE_MSG_TAG("uncompressed length exceeds 30MB", &tables[i].tag);
       }
       if (uncompressed_sum + tables[i].uncompressed_length < uncompressed_sum) {
-        return OTS_FAILURE();
+        return OTS_FAILURE_MSG_TAG("overflow of uncompressed sum", &tables[i].tag);
       }
 
       uncompressed_sum += tables[i].uncompressed_length;
@@ -476,13 +490,13 @@ bool ProcessGeneric(ots::OpenTypeFile *header, ots::OTSStream *output,
     // called TTX seems not to add 0-padding to the final table. It might be
     // ok to accept these fonts so we round up the length of the font file.
     if (!end_byte || end_byte > length) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_TAG("table overruns end of file", &tables[i].tag);
     }
   }
 
   // All decompressed tables uncompressed must be <= 30MB.
   if (uncompressed_sum > 30 * 1024 * 1024) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("uncompressed sum exceeds 30MB");
   }
 
   std::map<uint32_t, OpenTypeTable> table_map;
@@ -504,7 +518,7 @@ bool ProcessGeneric(ots::OpenTypeFile *header, ots::OTSStream *output,
   for (unsigned i = 0; i < overlap_checker.size(); ++i) {
     overlap_count += (overlap_checker[i].second ? 1 : -1);
     if (overlap_count > 1) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_HDR("overlapping tables");
     }
   }
 
@@ -518,7 +532,7 @@ bool ProcessGeneric(ots::OpenTypeFile *header, ots::OTSStream *output,
 
     if (it == table_map.end()) {
       if (table_parsers[i].required) {
-        return OTS_FAILURE();
+        return OTS_FAILURE_MSG_TAG("missing required table", table_parsers[i].tag);
       }
       continue;
     }
@@ -534,7 +548,7 @@ bool ProcessGeneric(ots::OpenTypeFile *header, ots::OTSStream *output,
       int r = uncompress((Bytef*) table_data, &dest_len,
                          data + it->second.offset, it->second.length);
       if (r != Z_OK || dest_len != table_length) {
-        return OTS_FAILURE();
+        return OTS_FAILURE_MSG_TAG("uncompress failed", table_parsers[i].tag);
       }
     } else {
       // uncompressed table. We can process directly from memory.
@@ -543,24 +557,26 @@ bool ProcessGeneric(ots::OpenTypeFile *header, ots::OTSStream *output,
     }
 
     if (!table_parsers[i].parse(header, table_data, table_length)) {
-      return OTS_FAILURE();
+      // TODO: parsers should generate specific messages detailing the failure;
+      // once those are all added, we won't need a generic failure message here
+      return OTS_FAILURE_MSG_TAG("failed to parse table", table_parsers[i].tag);
     }
   }
 
   if (header->cff) {
     // font with PostScript glyph
     if (header->version != Tag("OTTO")) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_HDR("wrong font version for PostScript glyph data");
     }
     if (header->glyf || header->loca) {
       // mixing outline formats is not recommended
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_HDR("font contains both PS and TT glyphs");
     }
   } else {
     if (!header->glyf || !header->loca) {
       // No TrueType glyph found.
       // Note: bitmap-only fonts are not supported.
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_HDR("neither PS nor TT glyphs present");
     }
   }
 
@@ -581,19 +597,21 @@ bool ProcessGeneric(ots::OpenTypeFile *header, ots::OTSStream *output,
   }
   const uint16_t output_search_range = (1u << max_pow2) << 4;
 
+  // most of the errors here are highly unlikely - they'd only occur if the
+  // output stream returns a failure, e.g. lack of space to write
   output->ResetChecksum();
   if (!output->WriteTag(header->version) ||
       !output->WriteU16(num_output_tables) ||
       !output->WriteU16(output_search_range) ||
       !output->WriteU16(max_pow2) ||
       !output->WriteU16((num_output_tables << 4) - output_search_range)) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("error writing output");
   }
   const uint32_t offset_table_chksum = output->chksum();
 
   const size_t table_record_offset = output->Tell();
   if (!output->Pad(16 * num_output_tables)) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("error writing output");
   }
 
   std::vector<OutputTable> out_tables;
@@ -618,20 +636,20 @@ bool ProcessGeneric(ots::OpenTypeFile *header, ots::OTSStream *output,
       head_table_offset = out.offset;
     }
     if (!table_parsers[i].serialise(output, header)) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_TAG("failed to serialize table", table_parsers[i].tag);
     }
 
     const size_t end_offset = output->Tell();
     if (end_offset <= out.offset) {
       // paranoid check. |end_offset| is supposed to be greater than the offset,
       // as long as the Tell() interface is implemented correctly.
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_HDR("error writing output");
     }
     out.length = end_offset - out.offset;
 
     // align tables to four bytes
     if (!output->Pad((4 - (end_offset & 3)) % 4)) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_HDR("error writing output");
     }
     out.chksum = output->chksum();
     out_tables.push_back(out);
@@ -642,7 +660,7 @@ bool ProcessGeneric(ots::OpenTypeFile *header, ots::OTSStream *output,
   // Need to sort the output tables for inclusion in the file
   std::sort(out_tables.begin(), out_tables.end(), OutputTable::SortByTag);
   if (!output->Seek(table_record_offset)) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("error writing output");
   }
 
   output->ResetChecksum();
@@ -652,7 +670,7 @@ bool ProcessGeneric(ots::OpenTypeFile *header, ots::OTSStream *output,
         !output->WriteU32(out_tables[i].chksum) ||
         !output->WriteU32(out_tables[i].offset) ||
         !output->WriteU32(out_tables[i].length)) {
-      return OTS_FAILURE();
+      return OTS_FAILURE_MSG_HDR("error writing output");
     }
     tables_chksum += out_tables[i].chksum;
   }
@@ -665,17 +683,17 @@ bool ProcessGeneric(ots::OpenTypeFile *header, ots::OTSStream *output,
 
   // seek into the 'head' table and write in the checksum magic value
   if (!head_table_offset) {
-    return OTS_FAILURE();  // not reached.
+    return OTS_FAILURE_MSG_HDR("internal error!");
   }
   if (!output->Seek(head_table_offset + 8)) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("error writing output");
   }
   if (!output->WriteU32(chksum_magic)) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("error writing output");
   }
 
   if (!output->Seek(end_of_file)) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_HDR("error writing output");
   }
 
   return true;
@@ -689,11 +707,20 @@ void DisableDebugOutput() {
   g_debug_output = false;
 }
 
-bool Process(OTSStream *output, const uint8_t *data, size_t length,
-             bool preserveGraphite) {
+bool OTS_API Process(OTSStream *output, const uint8_t *data, size_t length,
+#ifdef MOZ_OTS_REPORT_ERRORS
+                     MessageFunc message_func, void *user_data,
+#endif
+                     bool preserveGraphite) {
   OpenTypeFile header;
+
+#ifdef MOZ_OTS_REPORT_ERRORS
+  header.message_func = message_func;
+  header.user_data = user_data;
+#endif
+
   if (length < 4) {
-    return OTS_FAILURE();
+    return OTS_FAILURE_MSG_(&header, "file less than 4 bytes");
   }
 
   header.preserve_graphite = preserveGraphite;

gfx/ots/src/ots.h

@@ -38,6 +38,40 @@ void Warning(const char *f, int l, const char *format, ...)
 #endif
 #endif
 
+#ifdef MOZ_OTS_REPORT_ERRORS
+
+// All OTS_FAILURE_* macros ultimately evaluate to 'false', just like the original
+// message-less OTS_FAILURE(), so that the current parser will return 'false' as
+// its result (indicating a failure).
+// If the message-callback feature is enabled, and a message_func pointer has been
+// provided, this will be called before returning the 'false' status.
+
+// Generate a simple message
+#define OTS_FAILURE_MSG_(otf_,msg_) \
+  ((otf_)->message_func && \
+    (*(otf_)->message_func)((otf_)->user_data, "%s", msg_) && \
+    false)
+
+// Generate a message with an associated table tag
+#define OTS_FAILURE_MSG_TAG_(otf_,msg_,tag_) \
+  ((otf_)->message_func && \
+    (*(otf_)->message_func)((otf_)->user_data, "table '%4.4s': %s", tag_, msg_) && \
+    false)
+
+// Convenience macro for use in files that only handle a single table tag,
+// defined as TABLE_NAME at the top of the file; the 'file' variable is
+// expected to be the current OpenTypeFile pointer.
+#define OTS_FAILURE_MSG(msg_) OTS_FAILURE_MSG_TAG_(file, msg_, TABLE_NAME)
+
+#else
+
+// If the message-callback feature is not enabled, error messages are just dropped.
+#define OTS_FAILURE_MSG_(otf_,msg_)          OTS_FAILURE()
+#define OTS_FAILURE_MSG_TAG_(otf_,msg_,tag_) OTS_FAILURE()
+#define OTS_FAILURE_MSG(msg_)                OTS_FAILURE()
+
+#endif
+
 // Define OTS_NO_TRANSCODE_HINTS (i.e., g++ -DOTS_NO_TRANSCODE_HINTS) if you
 // want to omit TrueType hinting instructions and variables in glyf, fpgm, prep,
 // and cvt tables.
@@ -207,6 +241,11 @@ struct OpenTypeFile {
   uint16_t entry_selector;
   uint16_t range_shift;
 
+#ifdef MOZ_OTS_REPORT_ERRORS
+  MessageFunc message_func;
+  void        *user_data;
+#endif
+
   // This is used to tell the relevant parsers whether to preserve the
   // Graphite layout tables (currently _without_ any checking)
   bool preserve_graphite;