Don't let PDBSourceLineWriter::GetSymbolFunctionName return empty function names

src/common/windows/pdb_source_line_writer.cc

 // Copyright (c) 2006, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
@@ skipping 957 matching lines @@
                                    UNDNAME_NO_MEMBER_TYPE |
                                    UNDNAME_NO_RETURN_UDT_MODEL |
                                    UNDNAME_NO_ECSU;
 
   // Use get_undecoratedNameEx to get readable C++ names with arguments.
   if (function->get_undecoratedNameEx(undecorate_options, name) != S_OK) {
     if (function->get_name(name) != S_OK) {
       fprintf(stderr, "failed to get function name\n");
       return false;
     }
+
+    // It's possible for get_name to return an empty string, so
+    // special-case that.
+    if (wcscmp(*name, L"") == 0) {
+      SysFreeString(*name);
+      // dwarf_cu_to_module.cc uses "<name omitted>", so match that.
+      *name = SysAllocString(L"<name omitted>");
+      return true;
+    }
+
     // If a name comes from get_name because no undecorated form existed,
     // it's already formatted properly to be used as output.  Don't do any
     // additional processing.
     //
     // MSVC7's DIA seems to not undecorate names in as many cases as MSVC8's.
     // This will result in calling get_name for some C++ symbols, so
     // all of the parameter and return type information may not be included in
     // the name string.
   } else {
     // C++ uses a bogus "void" argument for functions and methods that don't
@@ skipping 362 matching lines @@
   // an old-style CodeView record if a real 128-bit GUID has its first 32
   // bits set the same as the module's signature (timestamp) and the rest of
   // the GUID is set to 0.  This is highly unlikely.
 
   GUID signature_guid = {signature};  // 0-initializes other members
   *uses_guid = !IsEqualGUID(guid, signature_guid);
   return true;
 }
 
 }  // namespace google_breakpad