Generated C++ headers now have include guards.

Bug: 15700355
Change-Id: Iceccb5b344e394e399092ffaa81f9cad2f0418ab
Tested: on Windows

include/flatbuffers/idl.h

@@ -302,7 +302,8 @@ extern void GenerateText(const Parser &parser,
 
 // Generate a C++ header from the definitions in the Parser object.
 // See idl_gen_cpp.
-extern std::string GenerateCPP(const Parser &parser);
+extern std::string GenerateCPP(const Parser &parser,
+                               const std::string &include_guard_ident);
 extern bool GenerateCPP(const Parser &parser,
                         const std::string &path,
                         const std::string &file_name);

src/idl_gen_cpp.cpp

@@ -298,7 +298,7 @@ static void GenStruct(StructDef &struct_def, std::string *code_ptr) {
 
 // Iterate through all definitions we haven't generate code for (enums, structs,
 // and tables) and output them to a single file.
-std::string GenerateCPP(const Parser &parser) {
+std::string GenerateCPP(const Parser &parser, const std::string &include_guard_ident) {
   using namespace cpp;
 
   // Generate code for all the enum declarations.
@@ -331,28 +331,54 @@ std::string GenerateCPP(const Parser &parser) {
   // Only output file-level code if there were any declarations.
   if (enum_code.length() || forward_decl_code.length() || decl_code.length()) {
     std::string code;
-    code = "// automatically generated, do not modify\n\n";
+    code = "// automatically generated by the FlatBuffers compiler,"
+           " do not modify\n\n";
+
+    // Generate include guard.
+    std::string include_guard = "FLATBUFFERS_GENERATED_" + include_guard_ident;
+    include_guard += "_";
+    for (auto it = parser.name_space_.begin();
+         it != parser.name_space_.end(); ++it) {
+      include_guard += *it + "_";
+    }
+    include_guard += "H_";
+    std::transform(include_guard.begin(), include_guard.end(),
+                   include_guard.begin(), ::toupper);
+    code += "#ifndef " + include_guard + "\n";
+    code += "#define " + include_guard + "\n\n";
+
     code += "#include \"flatbuffers/flatbuffers.h\"\n\n";
+
+    // Generate nested namespaces.
     for (auto it = parser.name_space_.begin();
          it != parser.name_space_.end(); ++it) {
       code += "namespace " + *it + " {\n";
     }
+
+    // Output the main declaration code from above.
     code += "\n";
     code += enum_code;
     code += forward_decl_code;
     code += "\n";
     code += decl_code;
+
+    // Generate convenient root datatype accessor.
     if (parser.root_struct_def) {
       code += "inline const " + parser.root_struct_def->name + " *Get";
       code += parser.root_struct_def->name;
       code += "(const void *buf) { return flatbuffers::GetRoot<";
       code += parser.root_struct_def->name + ">(buf); }\n\n";
     }
+
+    // Close the namespaces.
     for (auto it = parser.name_space_.begin();
          it != parser.name_space_.end(); ++it) {
-      code += "}; // namespace " + *it + "\n";
+      code += "};  // namespace " + *it + "\n";
     }
 
+    // Close the include guard.
+    code += "\n#endif  // " + include_guard + "\n";
+
     return code;
   }
 
@@ -362,7 +388,7 @@ std::string GenerateCPP(const Parser &parser) {
 bool GenerateCPP(const Parser &parser,
                  const std::string &path,
                  const std::string &file_name) {
-    auto code = GenerateCPP(parser);
+    auto code = GenerateCPP(parser, file_name);
     return !code.length() ||
            SaveFile((path + file_name + "_generated.h").c_str(), code, false);
 }

tests/monster_test_generated.h

-// automatically generated, do not modify
+// automatically generated by the FlatBuffers compiler, do not modify
+
+#ifndef FLATBUFFERS_GENERATED_MONSTER_TEST_MYGAME_EXAMPLE_H_
+#define FLATBUFFERS_GENERATED_MONSTER_TEST_MYGAME_EXAMPLE_H_
 
 #include "flatbuffers/flatbuffers.h"
 
@@ -119,5 +122,7 @@ inline flatbuffers::Offset<Monster> CreateMonster(flatbuffers::FlatBufferBuilder
 
 inline const Monster *GetMonster(const void *buf) { return flatbuffers::GetRoot<Monster>(buf); }
 
-}; // namespace MyGame
-}; // namespace Example
+};  // namespace MyGame
+};  // namespace Example
+
+#endif  // FLATBUFFERS_GENERATED_MONSTER_TEST_MYGAME_EXAMPLE_H_