Added --gen-name-strings command line option.

To support the use case described in issue google/flatbuffers#3826, a new command line option --gen-name-strings
has been added, which will cause a static GetFullyQualifiedName function to be added
to the C++ output for tables/structs.

include/flatbuffers/flatbuffers.h

@@ -91,6 +91,14 @@
 #else
   #define FLATBUFFERS_FINAL_CLASS
 #endif
+
+#if (!defined(_MSC_VER) || _MSC_VER >= 1900) && \
+    (!defined(__GNUC__) || (__GNUC__ * 100 + __GNUC_MINOR__ >= 406))
+  #define FLATBUFFERS_CONSTEXPR constexpr
+#else
+  #define FLATBUFFERS_CONSTEXPR
+#endif
+
 /// @endcond
 
 /// @file

include/flatbuffers/idl.h

@@ -321,6 +321,7 @@ struct IDLOptions {
   bool proto_mode;
   bool generate_all;
   bool skip_unexpected_fields_in_json;
+  bool generate_name_strings;
 
   // Possible options for the more general generator below.
   enum Language { kJava, kCSharp, kGo, kMAX };
@@ -339,6 +340,7 @@ struct IDLOptions {
       proto_mode(false),
       generate_all(false),
       skip_unexpected_fields_in_json(false),
+      generate_name_strings(false),
       lang(IDLOptions::kJava) {}
 };
 

src/flatc.cpp

@@ -117,6 +117,7 @@ static void Error(const std::string &err, bool usage, bool show_exe_name) {
       "                     schemas the generated file depends on (C++).\n"
       "  --gen-mutable      Generate accessors that can mutate buffers in-place.\n"
       "  --gen-onefile      Generate single output file for C#\n"
+      "  --gen-name-strings Generate type name functions for C++.\n"
       "  --raw-binary       Allow binaries without file_indentifier to be read.\n"
       "                     This may crash flatc given a mismatched schema.\n"
       "  --proto            Input is a .proto, translate to .fbs.\n"
@@ -171,6 +172,8 @@ int main(int argc, const char *argv[]) {
         opts.scoped_enums = true;
       } else if(arg == "--gen-mutable") {
         opts.mutable_buffer = true;
+      } else if(arg == "--gen-name-strings") {
+        opts.generate_name_strings = true;
       } else if(arg == "--gen-all") {
         opts.generate_all = true;
         opts.include_dependence_headers = false;

src/idl_gen_cpp.cpp

@@ -267,6 +267,14 @@ std::string GenFieldOffsetName(const FieldDef &field) {
   return "VT_" + uname;
 }
 
+static void GenFullyQualifiedNameGetter(const Parser &parser, const std::string& name, std::string &code) {
+  if (parser.opts.generate_name_strings) {
+    code += "  static FLATBUFFERS_CONSTEXPR const char *GetFullyQualifiedName() {\n";
+    code += "    return \"" + parser.namespaces_.back()->GetFullyQualifiedName(name) + "\";\n";
+    code += "  }\n";
+  }
+}
+
 // Generate an accessor struct, builder structs & function for a table.
 static void GenTable(const Parser &parser, StructDef &struct_def,
                      std::string *code_ptr) {
@@ -277,6 +285,8 @@ static void GenTable(const Parser &parser, StructDef &struct_def,
   code += "struct " + struct_def.name;
   code += " FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table";
   code += " {\n";
+  // Generate GetFullyQualifiedName
+  GenFullyQualifiedNameGetter(parser, struct_def.name, code);
   // Generate field id constants.
   if (struct_def.fields.vec.size() > 0) {
     code += "  enum {\n";
@@ -583,8 +593,12 @@ static void GenStruct(const Parser &parser, StructDef &struct_def,
     GenPadding(field, code, padding_id, PaddingDefinition);
   }
 
+  // Generate GetFullyQualifiedName
+  code += "\n public:\n";
+  GenFullyQualifiedNameGetter(parser, struct_def.name, code);
+
   // Generate a constructor that takes all fields as arguments.
-  code += "\n public:\n  " + struct_def.name + "(";
+  code += "  " + struct_def.name + "(";
   for (auto it = struct_def.fields.vec.begin();
        it != struct_def.fields.vec.end();
        ++it) {