Fix CreateVector/CreateVectorOfStructs for non-std vector types (cpp_vec_type)

When cpp_vec_type is set to a non-std container, Pack methods for scalar,
bool, and plain-struct vectors now use the pointer+size overloads of
CreateVector/CreateVectorOfStructs instead of the std::vector-only overloads.
Extends the combined cpp_vec_type+native_type test to also cover scalar
(ubyte) vectors with a custom container type.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CMakeLists.txt

@@ -240,6 +240,9 @@ set(FlatBuffers_Tests_SRCS
   tests/vector_table_naked_ptr_test.cpp
   tests/native_type_test_impl.h
   tests/native_type_test_impl.cpp
+  tests/cpp_vec_type_test_impl.h
+  tests/cpp_vec_type_native_type_test_impl.h
+  tests/cpp_vec_type_native_type_test_impl.cpp
   tests/alignment_test.h
   tests/alignment_test.cpp
   tests/64bit/offset64_test.h
@@ -554,6 +557,8 @@ if(FLATBUFFERS_BUILD_TESTS)
   compile_schema_for_test(tests/arrays_test.fbs "${FLATC_OPT_SCOPED_ENUMS}")
   compile_schema_for_test(tests/native_inline_table_test.fbs "${FLATC_OPT_COMP}")
   compile_schema_for_test(tests/native_type_test.fbs "${FLATC_OPT_COMP}")
+  compile_schema_for_test(tests/cpp_vec_type_test.fbs "${FLATC_OPT_COMP}")
+  compile_schema_for_test(tests/cpp_vec_type_native_type_test.fbs "${FLATC_OPT_COMP}")
   compile_schema_for_test(tests/key_field/key_field_sample.fbs "${FLATC_OPT_COMP}")
   compile_schema_for_test(tests/64bit/test_64bit.fbs "${FLATC_OPT_COMP};--bfbs-gen-embed")
   compile_schema_for_test(tests/64bit/evolution/v1.fbs "${FLATC_OPT_COMP}")

include/flatbuffers/idl.h

@@ -676,6 +676,7 @@ struct IDLOptions {
   bool gen_absl_hash;
   std::string cpp_object_api_pointer_type;
   std::string cpp_object_api_string_type;
+  std::string cpp_object_api_vector_type;
   bool cpp_object_api_string_flexible_constructor;
   CaseStyle cpp_object_api_field_case_style;
   bool cpp_direct_copy;
@@ -1012,6 +1013,7 @@ class Parser : public ParserState {
     known_attributes_["cpp_ptr_type_get"] = true;
     known_attributes_["cpp_str_type"] = true;
     known_attributes_["cpp_str_flex_ctor"] = true;
+    known_attributes_["cpp_vec_type"] = true;
     known_attributes_["native_inline"] = true;
     known_attributes_["native_custom_alloc"] = true;
     known_attributes_["native_type"] = true;

scripts/generate_code.py

@@ -383,6 +383,11 @@ flatc(
     schema="native_type_test.fbs",
 )
 
+flatc(
+    ["--cpp", "--gen-compare", "--gen-mutable", "--gen-object-api", "--reflect-names"],
+    schema="cpp_vec_type_test.fbs",
+)
+
 flatc(
     [
         "--cpp",

src/flatc.cpp

@@ -142,6 +142,10 @@ const static FlatCOption flatc_options[] = {
      "and T::empty() must be supported. The custom type also needs to be "
      "constructible from std::string (see the --cpp-str-flex-ctor option to "
      "change this behavior)"},
+    {"", "cpp-vec-type", "T",
+     "Set object API vector type (default std::vector). T must support the "
+     "same interface as std::vector: size(), resize(), reserve(), "
+     "emplace_back(), operator[], begin(), end(), and data()."},
     {"", "cpp-str-flex-ctor", "",
      "Don't construct custom string types by passing std::string from "
      "Flatbuffers, but (char* + length)."},
@@ -543,6 +547,9 @@ FlatCOptions FlatCompiler::ParseFromCommandLineArguments(int argc,
       } else if (arg == "--cpp-str-type") {
         if (++argi >= argc) Error("missing type following: " + arg, true);
         opts.cpp_object_api_string_type = argv[argi];
+      } else if (arg == "--cpp-vec-type") {
+        if (++argi >= argc) Error("missing type following: " + arg, true);
+        opts.cpp_object_api_vector_type = argv[argi];
       } else if (arg == "--cpp-str-flex-ctor") {
         opts.cpp_object_api_string_flexible_constructor = true;
       } else if (arg == "--no-cpp-direct-copy") {

src/idl_gen_cpp.cpp

@@ -929,6 +929,15 @@ class CppGenerator : public BaseGenerator {
     return ret;
   }
 
+  const std::string NativeVector(const FieldDef* field) {
+    auto attr = field ? field->attributes.Lookup("cpp_vec_type") : nullptr;
+    auto& ret = attr ? attr->constant : opts_.cpp_object_api_vector_type;
+    if (ret.empty()) {
+      return "std::vector";
+    }
+    return ret;
+  }
+
   bool FlexibleStringConstructor(const FieldDef* field) {
     auto attr = field != nullptr &&
                 (field->attributes.Lookup("cpp_str_flex_ctor") != nullptr);
@@ -974,20 +983,26 @@ class CppGenerator : public BaseGenerator {
       case BASE_TYPE_VECTOR64:
       case BASE_TYPE_VECTOR: {
         const auto type_name = GenTypeNative(type.VectorType(), true, field);
-        if (type.struct_def &&
+        const auto vec_type = NativeVector(&field);
+        if (vec_type == "std::vector" && type.struct_def &&
             type.struct_def->attributes.Lookup("native_custom_alloc")) {
           auto native_custom_alloc =
               type.struct_def->attributes.Lookup("native_custom_alloc");
           return "std::vector<" + type_name + "," +
                  native_custom_alloc->constant + "<" + type_name + ">>";
-        } else {
-          return "std::vector<" + type_name + ">";
         }
+        return vec_type + "<" + type_name + ">";
       }
       case BASE_TYPE_STRUCT: {
         auto type_name = WrapInNameSpace(*type.struct_def);
         if (IsStruct(type)) {
-          auto native_type = type.struct_def->attributes.Lookup("native_type");
+          // Field-level native_type takes priority over struct-level
+          // native_type
+          auto field_native_type = field.attributes.Lookup("native_type");
+          auto native_type =
+              field_native_type
+                  ? field_native_type
+                  : type.struct_def->attributes.Lookup("native_type");
           if (native_type) {
             type_name = native_type->constant;
           }
@@ -1951,9 +1966,10 @@ class CppGenerator : public BaseGenerator {
                            field.offset64);
       }
       if (TypeHasKey(vtype)) {
-        code_.SetValue("PARAM_TYPE", "std::vector<" + type + "> *");
+        code_.SetValue("PARAM_TYPE", NativeVector(&field) + "<" + type + "> *");
       } else {
-        code_.SetValue("PARAM_TYPE", "const std::vector<" + type + "> *");
+        code_.SetValue("PARAM_TYPE",
+                       "const " + NativeVector(&field) + "<" + type + "> *");
       }
       code_.SetValue("PARAM_VALUE", "nullptr");
     } else {
@@ -1979,7 +1995,7 @@ class CppGenerator : public BaseGenerator {
       const std::string& full_type =
           (cpp_type
                ? (IsVector(field.value.type)
-                      ? "std::vector<" +
+                      ? NativeVector(&field) + "<" +
                             GenTypeNativePtr(cpp_type->constant, &field,
                                              false) +
                             "> "
@@ -3516,10 +3532,21 @@ class CppGenerator : public BaseGenerator {
       case BASE_TYPE_STRUCT: {
         if (IsStruct(type)) {
           const auto& struct_attrs = type.struct_def->attributes;
-          const auto native_type = struct_attrs.Lookup("native_type");
+          // Field-level native_type takes priority over struct-level
+          // native_type
+          auto field_native_type = afield.attributes.Lookup("native_type");
+          const auto native_type = field_native_type
+                                       ? field_native_type
+                                       : struct_attrs.Lookup("native_type");
           if (native_type) {
             std::string unpack_call = "::flatbuffers::UnPack";
-            const auto pack_name = struct_attrs.Lookup("native_type_pack_name");
+            // Field-level native_type_pack_name takes priority over
+            // struct-level
+            auto field_pack_name =
+                afield.attributes.Lookup("native_type_pack_name");
+            const auto pack_name =
+                field_pack_name ? field_pack_name
+                                : struct_attrs.Lookup("native_type_pack_name");
             if (pack_name) {
               unpack_call += pack_name->constant;
             }
@@ -3774,7 +3801,8 @@ class CppGenerator : public BaseGenerator {
         auto vector_type = field.value.type.VectorType();
         switch (vector_type.base_type) {
           case BASE_TYPE_STRING: {
-            if (NativeString(&field) == "std::string") {
+            if (NativeString(&field) == "std::string" &&
+                NativeVector(&field) == "std::vector") {
               code += "_fbb.CreateVectorOfStrings(" + value + ")";
             } else {
               // Use by-function serialization to emulate
@@ -3795,30 +3823,52 @@ class CppGenerator : public BaseGenerator {
             if (IsStruct(vector_type)) {
               const auto& struct_attrs =
                   field.value.type.struct_def->attributes;
-              const auto native_type = struct_attrs.Lookup("native_type");
+              // Field-level native_type takes priority over struct-level
+              // native_type
+              auto field_native_type = field.attributes.Lookup("native_type");
+              const auto native_type = field_native_type
+                                           ? field_native_type
+                                           : struct_attrs.Lookup("native_type");
               if (native_type) {
                 code += "_fbb.CreateVectorOfNativeStructs<";
                 code += WrapInNameSpace(*vector_type.struct_def) + ", " +
                         native_type->constant + ">";
-                code += "(" + value;
+                // Field-level native_type_pack_name takes priority over
+                // struct-level
+                auto field_pack_name =
+                    field.attributes.Lookup("native_type_pack_name");
                 const auto pack_name =
-                    struct_attrs.Lookup("native_type_pack_name");
+                    field_pack_name
+                        ? field_pack_name
+                        : struct_attrs.Lookup("native_type_pack_name");
+                // Non-std vectors (e.g. eastl::vector) don't match the
+                // std::vector overload, so use the pointer+size overload.
+                const bool is_std_vec = NativeVector(&field) == "std::vector";
+                if (is_std_vec) {
+                  code += "(" + value;
+                } else {
+                  code += "(" + value + ".data(), " + value + ".size()";
+                }
                 if (pack_name) {
                   code += ", ::flatbuffers::Pack" + pack_name->constant;
                 }
                 code += ")";
               } else {
                 // If the field uses 64-bit addressing, create a 64-bit vector.
+                const bool is_std_vec = NativeVector(&field) == "std::vector";
+                const std::string vec_args =
+                    is_std_vec ? ("(" + value + ")")
+                               : ("(" + value + ".data(), " + value + ".size())");
                 if (field.value.type.base_type == BASE_TYPE_VECTOR64) {
-                  code += "_fbb.CreateVectorOfStructs64";
+                  code += "_fbb.CreateVectorOfStructs64" + vec_args;
                 } else {
                   code += "_fbb.CreateVectorOfStructs";
                   if (field.offset64) {
                     // This is normal 32-bit vector, with 64-bit addressing.
                     code += "64<::flatbuffers::Vector>";
                   }
+                  code += vec_args;
                 }
-                code += "(" + value + ")";
               }
             } else {
               code += "_fbb.CreateVector<::flatbuffers::Offset<";
@@ -3837,7 +3887,12 @@ class CppGenerator : public BaseGenerator {
             break;
           }
           case BASE_TYPE_BOOL: {
-            code += "_fbb.CreateVector(" + value + ")";
+            if (NativeVector(&field) == "std::vector") {
+              code += "_fbb.CreateVector(" + value + ")";
+            } else {
+              code += "_fbb.CreateVector(" + value + ".data(), " + value +
+                      ".size())";
+            }
             break;
           }
           case BASE_TYPE_UNION: {
@@ -3886,15 +3941,19 @@ class CppGenerator : public BaseGenerator {
               code += "; }, &_va )";
             } else {
               // If the field uses 64-bit addressing, create a 64-bit vector.
+              const bool is_std_vec = NativeVector(&field) == "std::vector";
+              const std::string vec_args =
+                  is_std_vec ? ("(" + value + ")")
+                             : ("(" + value + ".data(), " + value + ".size())");
               if (field.value.type.base_type == BASE_TYPE_VECTOR64) {
-                code += "_fbb.CreateVector64(" + value + ")";
+                code += "_fbb.CreateVector64" + vec_args;
               } else {
                 code += "_fbb.CreateVector";
                 if (field.offset64) {
                   // This is normal 32-bit vector, with 64-bit addressing.
                   code += "64<::flatbuffers::Vector>";
                 }
-                code += "(" + value + ")";
+                code += vec_args;
               }
             }
             break;
@@ -3918,11 +3977,22 @@ class CppGenerator : public BaseGenerator {
       case BASE_TYPE_STRUCT: {
         if (IsStruct(field.value.type)) {
           const auto& struct_attribs = field.value.type.struct_def->attributes;
-          const auto native_type = struct_attribs.Lookup("native_type");
+          // Field-level native_type takes priority over struct-level
+          // native_type
+          auto field_native_type = field.attributes.Lookup("native_type");
+          const auto native_type = field_native_type
+                                       ? field_native_type
+                                       : struct_attribs.Lookup("native_type");
           if (native_type && field.native_inline) {
             code += "::flatbuffers::Pack";
+            // Field-level native_type_pack_name takes priority over
+            // struct-level
+            auto field_pack_name =
+                field.attributes.Lookup("native_type_pack_name");
             const auto pack_name =
-                struct_attribs.Lookup("native_type_pack_name");
+                field_pack_name
+                    ? field_pack_name
+                    : struct_attribs.Lookup("native_type_pack_name");
             if (pack_name) {
               code += pack_name->constant;
             }
@@ -4086,9 +4156,15 @@ class CppGenerator : public BaseGenerator {
           bool check_ptr = false;
           if (field->value.type.base_type == BASE_TYPE_STRUCT) {
             if (IsStruct(field->value.type)) {
+              // Field-level native_type takes priority over struct-level
+              // native_type
+              auto field_native_type =
+                  field->attributes.Lookup("native_type");
               auto native_type =
-                  field->value.type.struct_def->attributes.Lookup(
-                      "native_type");
+                  field_native_type
+                      ? field_native_type
+                      : field->value.type.struct_def->attributes.Lookup(
+                            "native_type");
               auto native_inline = field->attributes.Lookup("native_inline");
               if (native_type) {
                 pass_by_address = true;

tests/cpp_vec_type_native_type_test.fbs

@@ -0,0 +1,16 @@
+native_include "cpp_vec_type_native_type_test_impl.h";
+
+namespace CppVecNativeTypeTest;
+
+struct Vec3 (native_type: "CppVecNativeTypeTest::Native::Vec3") {
+  x: float;
+  y: float;
+  z: float;
+}
+
+table Container {
+  points: [Vec3] (cpp_vec_type: "CppVecNativeTypeTest::CustomVec");
+  bytes: [ubyte] (cpp_vec_type: "CppVecNativeTypeTest::CustomVec");
+}
+
+root_type Container;

tests/cpp_vec_type_native_type_test_impl.cpp

@@ -0,0 +1,15 @@
+#include "cpp_vec_type_native_type_test_impl.h"
+
+#include "cpp_vec_type_native_type_test_generated.h"
+
+namespace flatbuffers {
+CppVecNativeTypeTest::Vec3 Pack(
+    const CppVecNativeTypeTest::Native::Vec3& obj) {
+  return CppVecNativeTypeTest::Vec3(obj.x, obj.y, obj.z);
+}
+
+const CppVecNativeTypeTest::Native::Vec3 UnPack(
+    const CppVecNativeTypeTest::Vec3& obj) {
+  return CppVecNativeTypeTest::Native::Vec3(obj.x(), obj.y(), obj.z());
+}
+}  // namespace flatbuffers

tests/cpp_vec_type_native_type_test_impl.h

@@ -0,0 +1,34 @@
+#ifndef CPP_VEC_TYPE_NATIVE_TYPE_TEST_IMPL_H
+#define CPP_VEC_TYPE_NATIVE_TYPE_TEST_IMPL_H
+
+#include <vector>
+
+namespace CppVecNativeTypeTest {
+
+namespace Native {
+struct Vec3 {
+  float x, y, z;
+  Vec3() : x(0), y(0), z(0) {}
+  Vec3(float x_, float y_, float z_) : x(x_), y(y_), z(z_) {}
+  bool operator==(const Vec3& o) const {
+    return x == o.x && y == o.y && z == o.z;
+  }
+};
+}  // namespace Native
+
+template <typename T>
+struct CustomVec : public std::vector<T> {
+  using std::vector<T>::vector;
+};
+
+struct Vec3;  // flatbuffers-generated struct
+
+}  // namespace CppVecNativeTypeTest
+
+namespace flatbuffers {
+CppVecNativeTypeTest::Vec3 Pack(const CppVecNativeTypeTest::Native::Vec3& obj);
+const CppVecNativeTypeTest::Native::Vec3 UnPack(
+    const CppVecNativeTypeTest::Vec3& obj);
+}  // namespace flatbuffers
+
+#endif  // CPP_VEC_TYPE_NATIVE_TYPE_TEST_IMPL_H

tests/cpp_vec_type_test.fbs

@@ -0,0 +1,17 @@
+native_include "cpp_vec_type_test_impl.h";
+
+namespace CppVecTest;
+
+table Item {
+  id: int;
+  value: float;
+}
+
+table Data {
+  values: [int] (cpp_vec_type: "CppVecTest::CustomVec");
+  items: [Item] (cpp_vec_type: "CppVecTest::CustomVec");
+  strs: [string] (cpp_vec_type: "CppVecTest::CustomVec");
+  regular: [int];
+}
+
+root_type Data;

tests/cpp_vec_type_test_impl.h

@@ -0,0 +1,15 @@
+#ifndef CPP_VEC_TYPE_TEST_IMPL_H
+#define CPP_VEC_TYPE_TEST_IMPL_H
+
+#include <vector>
+
+namespace CppVecTest {
+
+template<typename T>
+struct CustomVec : public std::vector<T> {
+  using std::vector<T>::vector;
+};
+
+}  // namespace CppVecTest
+
+#endif  // CPP_VEC_TYPE_TEST_IMPL_H

tests/native_type_test.fbs

@@ -14,6 +14,12 @@ struct Vector3DAlt (native_type:"Native::Vector3D", native_type_pack_name:"Vecto
   c:float;
 }
 
+struct Vector3DSimple {
+  x:float;
+  y:float;
+  z:float;
+}
+
 table Matrix (native_type:"Native::Matrix") {
   rows:int32;
   columns:int32;
@@ -27,6 +33,8 @@ table ApplicationData {
   position_inline:Vector3D (native_inline);
   matrix:Matrix;
   matrices:[Matrix];
+  simple_position:Vector3DSimple (native_type: "Native::Vector3D", native_inline, native_type_pack_name: "Vector3DSimple");
+  simple_vectors:[Vector3DSimple] (native_type: "Native::Vector3D", native_type_pack_name: "Vector3DSimple");
 }
 
 root_type ApplicationData;

tests/native_type_test_generated.h

@@ -21,6 +21,8 @@ struct Vector3D;
 
 struct Vector3DAlt;
 
+struct Vector3DSimple;
+
 struct Matrix;
 struct MatrixBuilder;
 
@@ -28,6 +30,8 @@ struct ApplicationData;
 struct ApplicationDataBuilder;
 struct ApplicationDataT;
 
+bool operator==(const Vector3DSimple &lhs, const Vector3DSimple &rhs);
+bool operator!=(const Vector3DSimple &lhs, const Vector3DSimple &rhs);
 bool operator==(const ApplicationDataT &lhs, const ApplicationDataT &rhs);
 bool operator!=(const ApplicationDataT &lhs, const ApplicationDataT &rhs);
 
@@ -35,6 +39,8 @@ inline const ::flatbuffers::TypeTable *Vector3DTypeTable();
 
 inline const ::flatbuffers::TypeTable *Vector3DAltTypeTable();
 
+inline const ::flatbuffers::TypeTable *Vector3DSimpleTypeTable();
+
 inline const ::flatbuffers::TypeTable *MatrixTypeTable();
 
 inline const ::flatbuffers::TypeTable *ApplicationDataTypeTable();
@@ -121,6 +127,59 @@ FLATBUFFERS_MANUALLY_ALIGNED_STRUCT(4) Vector3DAlt FLATBUFFERS_FINAL_CLASS {
 };
 FLATBUFFERS_STRUCT_END(Vector3DAlt, 12);
 
+FLATBUFFERS_MANUALLY_ALIGNED_STRUCT(4) Vector3DSimple FLATBUFFERS_FINAL_CLASS {
+ private:
+  float x_;
+  float y_;
+  float z_;
+
+ public:
+  static const ::flatbuffers::TypeTable *MiniReflectTypeTable() {
+    return Vector3DSimpleTypeTable();
+  }
+  Vector3DSimple()
+      : x_(0),
+        y_(0),
+        z_(0) {
+  }
+  Vector3DSimple(float _x, float _y, float _z)
+      : x_(::flatbuffers::EndianScalar(_x)),
+        y_(::flatbuffers::EndianScalar(_y)),
+        z_(::flatbuffers::EndianScalar(_z)) {
+  }
+  float x() const {
+    return ::flatbuffers::EndianScalar(x_);
+  }
+  void mutate_x(float _x) {
+    ::flatbuffers::WriteScalar(&x_, _x);
+  }
+  float y() const {
+    return ::flatbuffers::EndianScalar(y_);
+  }
+  void mutate_y(float _y) {
+    ::flatbuffers::WriteScalar(&y_, _y);
+  }
+  float z() const {
+    return ::flatbuffers::EndianScalar(z_);
+  }
+  void mutate_z(float _z) {
+    ::flatbuffers::WriteScalar(&z_, _z);
+  }
+};
+FLATBUFFERS_STRUCT_END(Vector3DSimple, 12);
+
+inline bool operator==(const Vector3DSimple &lhs, const Vector3DSimple &rhs) {
+  return
+      (lhs.x() == rhs.x()) &&
+      (lhs.y() == rhs.y()) &&
+      (lhs.z() == rhs.z());
+}
+
+inline bool operator!=(const Vector3DSimple &lhs, const Vector3DSimple &rhs) {
+    return !(lhs == rhs);
+}
+
+
 struct Matrix FLATBUFFERS_FINAL_CLASS : private ::flatbuffers::Table {
   typedef Native::Matrix NativeTableType;
   typedef MatrixBuilder Builder;
@@ -223,6 +282,8 @@ struct ApplicationDataT : public ::flatbuffers::NativeTable {
   Native::Vector3D position_inline{};
   std::unique_ptr<Native::Matrix> matrix{};
   std::vector<std::unique_ptr<Native::Matrix>> matrices{};
+  Native::Vector3D simple_position{};
+  std::vector<Native::Vector3D> simple_vectors{};
   ApplicationDataT() = default;
   ApplicationDataT(const ApplicationDataT &o);
   ApplicationDataT(ApplicationDataT&&) FLATBUFFERS_NOEXCEPT = default;
@@ -241,7 +302,9 @@ struct ApplicationData FLATBUFFERS_FINAL_CLASS : private ::flatbuffers::Table {
     VT_POSITION = 8,
     VT_POSITION_INLINE = 10,
     VT_MATRIX = 12,
-    VT_MATRICES = 14
+    VT_MATRICES = 14,
+    VT_SIMPLE_POSITION = 16,
+    VT_SIMPLE_VECTORS = 18
   };
   const ::flatbuffers::Vector<const Geometry::Vector3D *> *vectors() const {
     return GetPointer<const ::flatbuffers::Vector<const Geometry::Vector3D *> *>(VT_VECTORS);
@@ -279,6 +342,18 @@ struct ApplicationData FLATBUFFERS_FINAL_CLASS : private ::flatbuffers::Table {
   ::flatbuffers::Vector<::flatbuffers::Offset<Geometry::Matrix>> *mutable_matrices() {
     return GetPointer<::flatbuffers::Vector<::flatbuffers::Offset<Geometry::Matrix>> *>(VT_MATRICES);
   }
+  const Geometry::Vector3DSimple *simple_position() const {
+    return GetStruct<const Geometry::Vector3DSimple *>(VT_SIMPLE_POSITION);
+  }
+  Geometry::Vector3DSimple *mutable_simple_position() {
+    return GetStruct<Geometry::Vector3DSimple *>(VT_SIMPLE_POSITION);
+  }
+  const ::flatbuffers::Vector<const Geometry::Vector3DSimple *> *simple_vectors() const {
+    return GetPointer<const ::flatbuffers::Vector<const Geometry::Vector3DSimple *> *>(VT_SIMPLE_VECTORS);
+  }
+  ::flatbuffers::Vector<const Geometry::Vector3DSimple *> *mutable_simple_vectors() {
+    return GetPointer<::flatbuffers::Vector<const Geometry::Vector3DSimple *> *>(VT_SIMPLE_VECTORS);
+  }
   template <bool B = false>
   bool Verify(::flatbuffers::VerifierTemplate<B> &verifier) const {
     return VerifyTableStart(verifier) &&
@@ -293,6 +368,9 @@ struct ApplicationData FLATBUFFERS_FINAL_CLASS : private ::flatbuffers::Table {
            VerifyOffset(verifier, VT_MATRICES) &&
            verifier.VerifyVector(matrices()) &&
            verifier.VerifyVectorOfTables(matrices()) &&
+           VerifyField<Geometry::Vector3DSimple>(verifier, VT_SIMPLE_POSITION, 4) &&
+           VerifyOffset(verifier, VT_SIMPLE_VECTORS) &&
+           verifier.VerifyVector(simple_vectors()) &&
            verifier.EndTable();
   }
   ApplicationDataT *UnPack(const ::flatbuffers::resolver_function_t *_resolver = nullptr) const;
@@ -322,6 +400,12 @@ struct ApplicationDataBuilder {
   void add_matrices(::flatbuffers::Offset<::flatbuffers::Vector<::flatbuffers::Offset<Geometry::Matrix>>> matrices) {
     fbb_.AddOffset(ApplicationData::VT_MATRICES, matrices);
   }
+  void add_simple_position(const Geometry::Vector3DSimple *simple_position) {
+    fbb_.AddStruct(ApplicationData::VT_SIMPLE_POSITION, simple_position);
+  }
+  void add_simple_vectors(::flatbuffers::Offset<::flatbuffers::Vector<const Geometry::Vector3DSimple *>> simple_vectors) {
+    fbb_.AddOffset(ApplicationData::VT_SIMPLE_VECTORS, simple_vectors);
+  }
   explicit ApplicationDataBuilder(::flatbuffers::FlatBufferBuilder &_fbb)
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
@@ -340,8 +424,12 @@ inline ::flatbuffers::Offset<ApplicationData> CreateApplicationData(
     const Geometry::Vector3D *position = nullptr,
     const Geometry::Vector3D *position_inline = nullptr,
     ::flatbuffers::Offset<Geometry::Matrix> matrix = 0,
-    ::flatbuffers::Offset<::flatbuffers::Vector<::flatbuffers::Offset<Geometry::Matrix>>> matrices = 0) {
+    ::flatbuffers::Offset<::flatbuffers::Vector<::flatbuffers::Offset<Geometry::Matrix>>> matrices = 0,
+    const Geometry::Vector3DSimple *simple_position = nullptr,
+    ::flatbuffers::Offset<::flatbuffers::Vector<const Geometry::Vector3DSimple *>> simple_vectors = 0) {
   ApplicationDataBuilder builder_(_fbb);
+  builder_.add_simple_vectors(simple_vectors);
+  builder_.add_simple_position(simple_position);
   builder_.add_matrices(matrices);
   builder_.add_matrix(matrix);
   builder_.add_position_inline(position_inline);
@@ -358,10 +446,13 @@ inline ::flatbuffers::Offset<ApplicationData> CreateApplicationDataDirect(
     const Geometry::Vector3D *position = nullptr,
     const Geometry::Vector3D *position_inline = nullptr,
     ::flatbuffers::Offset<Geometry::Matrix> matrix = 0,
-    const std::vector<::flatbuffers::Offset<Geometry::Matrix>> *matrices = nullptr) {
+    const std::vector<::flatbuffers::Offset<Geometry::Matrix>> *matrices = nullptr,
+    const Geometry::Vector3DSimple *simple_position = nullptr,
+    const std::vector<Geometry::Vector3DSimple> *simple_vectors = nullptr) {
   auto vectors__ = vectors ? _fbb.CreateVectorOfStructs<Geometry::Vector3D>(*vectors) : 0;
   auto vectors_alt__ = vectors_alt ? _fbb.CreateVectorOfStructs<Geometry::Vector3DAlt>(*vectors_alt) : 0;
   auto matrices__ = matrices ? _fbb.CreateVector<::flatbuffers::Offset<Geometry::Matrix>>(*matrices) : 0;
+  auto simple_vectors__ = simple_vectors ? _fbb.CreateVectorOfStructs<Geometry::Vector3DSimple>(*simple_vectors) : 0;
   return Geometry::CreateApplicationData(
       _fbb,
       vectors__,
@@ -369,7 +460,9 @@ inline ::flatbuffers::Offset<ApplicationData> CreateApplicationDataDirect(
       position,
       position_inline,
       matrix,
-      matrices__);
+      matrices__,
+      simple_position,
+      simple_vectors__);
 }
 
 ::flatbuffers::Offset<ApplicationData> CreateApplicationData(::flatbuffers::FlatBufferBuilder &_fbb, const ApplicationDataT *_o, const ::flatbuffers::rehasher_function_t *_rehasher = nullptr);
@@ -392,7 +485,9 @@ inline bool operator==(const ApplicationDataT &lhs, const ApplicationDataT &rhs)
       ((lhs.position == rhs.position) || (lhs.position && rhs.position && *lhs.position == *rhs.position)) &&
       (lhs.position_inline == rhs.position_inline) &&
       ((lhs.matrix == rhs.matrix) || (lhs.matrix && rhs.matrix && *lhs.matrix == *rhs.matrix)) &&
-      (lhs.matrices.size() == rhs.matrices.size() && std::equal(lhs.matrices.cbegin(), lhs.matrices.cend(), rhs.matrices.cbegin(), [](std::unique_ptr<Native::Matrix> const &a, std::unique_ptr<Native::Matrix> const &b) { return (a == b) || (a && b && *a == *b); }));
+      (lhs.matrices.size() == rhs.matrices.size() && std::equal(lhs.matrices.cbegin(), lhs.matrices.cend(), rhs.matrices.cbegin(), [](std::unique_ptr<Native::Matrix> const &a, std::unique_ptr<Native::Matrix> const &b) { return (a == b) || (a && b && *a == *b); })) &&
+      (lhs.simple_position == rhs.simple_position) &&
+      (lhs.simple_vectors == rhs.simple_vectors);
 }
 
 inline bool operator!=(const ApplicationDataT &lhs, const ApplicationDataT &rhs) {
@@ -405,7 +500,9 @@ inline ApplicationDataT::ApplicationDataT(const ApplicationDataT &o)
         vectors_alt(o.vectors_alt),
         position((o.position) ? new Native::Vector3D(*o.position) : nullptr),
         position_inline(o.position_inline),
-        matrix((o.matrix) ? new Native::Matrix(*o.matrix) : nullptr) {
+        matrix((o.matrix) ? new Native::Matrix(*o.matrix) : nullptr),
+        simple_position(o.simple_position),
+        simple_vectors(o.simple_vectors) {
   matrices.reserve(o.matrices.size());
   for (const auto &matrices_ : o.matrices) { matrices.emplace_back((matrices_) ? new Native::Matrix(*matrices_) : nullptr); }
 }
@@ -417,6 +514,8 @@ inline ApplicationDataT &ApplicationDataT::operator=(ApplicationDataT o) FLATBUF
   std::swap(position_inline, o.position_inline);
   std::swap(matrix, o.matrix);
   std::swap(matrices, o.matrices);
+  std::swap(simple_position, o.simple_position);
+  std::swap(simple_vectors, o.simple_vectors);
   return *this;
 }
 
@@ -435,6 +534,8 @@ inline void ApplicationData::UnPackTo(ApplicationDataT *_o, const ::flatbuffers:
   { auto _e = position_inline(); if (_e) _o->position_inline = ::flatbuffers::UnPack(*_e); }
   { auto _e = matrix(); if (_e) { if(_o->matrix) { _e->UnPackTo(_o->matrix.get(), _resolver); } else { _o->matrix = std::unique_ptr<Native::Matrix>(_e->UnPack(_resolver)); } } else if (_o->matrix) { _o->matrix.reset(); } }
   { auto _e = matrices(); if (_e) { _o->matrices.resize(_e->size()); for (::flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { if(_o->matrices[_i]) { _e->Get(_i)->UnPackTo(_o->matrices[_i].get(), _resolver); } else { _o->matrices[_i] = std::unique_ptr<Native::Matrix>(_e->Get(_i)->UnPack(_resolver)); } } } else { _o->matrices.resize(0); } }
+  { auto _e = simple_position(); if (_e) _o->simple_position = ::flatbuffers::UnPackVector3DSimple(*_e); }
+  { auto _e = simple_vectors(); if (_e) { _o->simple_vectors.resize(_e->size()); for (::flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->simple_vectors[_i] = ::flatbuffers::UnPackVector3DSimple(*_e->Get(_i)); } } else { _o->simple_vectors.resize(0); } }
 }
 
 inline ::flatbuffers::Offset<ApplicationData> CreateApplicationData(::flatbuffers::FlatBufferBuilder &_fbb, const ApplicationDataT *_o, const ::flatbuffers::rehasher_function_t *_rehasher) {
@@ -451,6 +552,8 @@ inline ::flatbuffers::Offset<ApplicationData> ApplicationData::Pack(::flatbuffer
   auto _position_inline = ::flatbuffers::Pack(_o->position_inline);
   auto _matrix = _o->matrix ? CreateMatrix(_fbb, _o->matrix.get(), _rehasher) : 0;
   auto _matrices = _o->matrices.size() ? _fbb.CreateVector<::flatbuffers::Offset<Geometry::Matrix>> (_o->matrices.size(), [](size_t i, _VectorArgs *__va) { return CreateMatrix(*__va->__fbb, __va->__o->matrices[i].get(), __va->__rehasher); }, &_va ) : 0;
+  auto _simple_position = ::flatbuffers::PackVector3DSimple(_o->simple_position);
+  auto _simple_vectors = _o->simple_vectors.size() ? _fbb.CreateVectorOfNativeStructs<Geometry::Vector3DSimple, Native::Vector3D>(_o->simple_vectors, ::flatbuffers::PackVector3DSimple) : 0;
   return Geometry::CreateApplicationData(
       _fbb,
       _vectors,
@@ -458,7 +561,9 @@ inline ::flatbuffers::Offset<ApplicationData> ApplicationData::Pack(::flatbuffer
       _o->position ? &_position : nullptr,
       &_position_inline,
       _matrix,
-      _matrices);
+      _matrices,
+      &_simple_position,
+      _simple_vectors);
 }
 
 inline const ::flatbuffers::TypeTable *Vector3DTypeTable() {
@@ -497,6 +602,24 @@ inline const ::flatbuffers::TypeTable *Vector3DAltTypeTable() {
   return &tt;
 }
 
+inline const ::flatbuffers::TypeTable *Vector3DSimpleTypeTable() {
+  static const ::flatbuffers::TypeCode type_codes[] = {
+    { ::flatbuffers::ET_FLOAT, 0, -1 },
+    { ::flatbuffers::ET_FLOAT, 0, -1 },
+    { ::flatbuffers::ET_FLOAT, 0, -1 }
+  };
+  static const int64_t values[] = { 0, 4, 8, 12 };
+  static const char * const names[] = {
+    "x",
+    "y",
+    "z"
+  };
+  static const ::flatbuffers::TypeTable tt = {
+    ::flatbuffers::ST_STRUCT, 3, type_codes, nullptr, nullptr, values, names
+  };
+  return &tt;
+}
+
 inline const ::flatbuffers::TypeTable *MatrixTypeTable() {
   static const ::flatbuffers::TypeCode type_codes[] = {
     { ::flatbuffers::ET_INT, 0, -1 },
@@ -521,12 +644,15 @@ inline const ::flatbuffers::TypeTable *ApplicationDataTypeTable() {
     { ::flatbuffers::ET_SEQUENCE, 0, 0 },
     { ::flatbuffers::ET_SEQUENCE, 0, 0 },
     { ::flatbuffers::ET_SEQUENCE, 0, 2 },
-    { ::flatbuffers::ET_SEQUENCE, 1, 2 }
+    { ::flatbuffers::ET_SEQUENCE, 1, 2 },
+    { ::flatbuffers::ET_SEQUENCE, 0, 3 },
+    { ::flatbuffers::ET_SEQUENCE, 1, 3 }
   };
   static const ::flatbuffers::TypeFunction type_refs[] = {
     Geometry::Vector3DTypeTable,
     Geometry::Vector3DAltTypeTable,
-    Geometry::MatrixTypeTable
+    Geometry::MatrixTypeTable,
+    Geometry::Vector3DSimpleTypeTable
   };
   static const char * const names[] = {
     "vectors",
@@ -534,10 +660,12 @@ inline const ::flatbuffers::TypeTable *ApplicationDataTypeTable() {
     "position",
     "position_inline",
     "matrix",
-    "matrices"
+    "matrices",
+    "simple_position",
+    "simple_vectors"
   };
   static const ::flatbuffers::TypeTable tt = {
-    ::flatbuffers::ST_TABLE, 6, type_codes, type_refs, nullptr, nullptr, names
+    ::flatbuffers::ST_TABLE, 8, type_codes, type_refs, nullptr, nullptr, names
   };
   return &tt;
 }

tests/native_type_test_impl.cpp

@@ -18,6 +18,15 @@ Geometry::Vector3DAlt PackVector3DAlt(const Native::Vector3D& obj) {
 const Native::Vector3D UnPackVector3DAlt(const Geometry::Vector3DAlt& obj) {
   return Native::Vector3D(obj.a(), obj.b(), obj.c());
 }
+
+Geometry::Vector3DSimple PackVector3DSimple(const Native::Vector3D& obj) {
+  return Geometry::Vector3DSimple(obj.x, obj.y, obj.z);
+}
+
+const Native::Vector3D UnPackVector3DSimple(
+    const Geometry::Vector3DSimple& obj) {
+  return Native::Vector3D(obj.x(), obj.y(), obj.z());
+}
 }  // namespace flatbuffers
 
 namespace Geometry {

tests/native_type_test_impl.h

@@ -48,6 +48,7 @@ struct Matrix {
 namespace Geometry {
 struct Vector3D;
 struct Vector3DAlt;
+struct Vector3DSimple;
 }  // namespace Geometry
 
 namespace flatbuffers {
@@ -55,6 +56,8 @@ Geometry::Vector3D Pack(const Native::Vector3D& obj);
 const Native::Vector3D UnPack(const Geometry::Vector3D& obj);
 Geometry::Vector3DAlt PackVector3DAlt(const Native::Vector3D& obj);
 const Native::Vector3D UnPackVector3DAlt(const Geometry::Vector3DAlt& obj);
+Geometry::Vector3DSimple PackVector3DSimple(const Native::Vector3D& obj);
+const Native::Vector3D UnPackVector3DSimple(const Geometry::Vector3DSimple& obj);
 }  // namespace flatbuffers
 
 #endif  // VECTOR3D_PACK_H

tests/test.cpp

@@ -63,7 +63,9 @@
 #include "flexbuffers_test.h"
 #include "is_quiet_nan.h"
 #include "monster_test_bfbs_generated.h"  // Generated using --bfbs-comments --bfbs-builtins --cpp --bfbs-gen-embed
+#include "cpp_vec_type_test_generated.h"
 #include "native_type_test_generated.h"
+#include "cpp_vec_type_native_type_test_generated.h"
 #include "test_assert.h"
 #include "util_test.h"
 #include "vector_table_naked_ptr_test.h"
@@ -929,6 +931,12 @@ void NativeTypeTest() {
         Native::Vector3D(20 * i + 0.1f, 20 * i + 0.2f, 20 * i + 0.3f));
   }
 
+  src_data.simple_position = Native::Vector3D(7.0f, 8.0f, 9.0f);
+  for (int i = 0; i < N; ++i) {
+    src_data.simple_vectors.push_back(
+        Native::Vector3D(30 * i + 0.1f, 30 * i + 0.2f, 30 * i + 0.3f));
+  }
+
   src_data.matrix = std::unique_ptr<Native::Matrix>(new Native::Matrix(1, 2));
   src_data.matrix->values = {3, 4};
 
@@ -963,6 +971,17 @@ void NativeTypeTest() {
     TEST_EQ(v2.z, 20 * i + 0.3f);
   }
 
+  TEST_EQ(dstDataT->simple_position.x, 7.0f);
+  TEST_EQ(dstDataT->simple_position.y, 8.0f);
+  TEST_EQ(dstDataT->simple_position.z, 9.0f);
+
+  for (int i = 0; i < N; ++i) {
+    const Native::Vector3D& sv = dstDataT->simple_vectors[i];
+    TEST_EQ(sv.x, 30 * i + 0.1f);
+    TEST_EQ(sv.y, 30 * i + 0.2f);
+    TEST_EQ(sv.z, 30 * i + 0.3f);
+  }
+
   TEST_EQ(dstDataT->matrix->rows, 1);
   TEST_EQ(dstDataT->matrix->columns, 2);
   TEST_EQ(dstDataT->matrix->values[0], 3);
@@ -978,6 +997,92 @@ void NativeTypeTest() {
   }
 }
 
+void CppVecTypeTest() {
+  static_assert(
+      std::is_same<decltype(CppVecTest::DataT{}.values),
+                   CppVecTest::CustomVec<int32_t>>::value,
+      "values should be CustomVec<int32_t>");
+  static_assert(
+      std::is_same<decltype(CppVecTest::DataT{}.regular),
+                   std::vector<int32_t>>::value,
+      "regular should be std::vector<int32_t>");
+
+  CppVecTest::DataT src;
+  src.values.push_back(10);
+  src.values.push_back(20);
+  src.values.push_back(30);
+
+  auto item = flatbuffers::unique_ptr<CppVecTest::ItemT>(new CppVecTest::ItemT());
+  item->id = 42;
+  item->value = 1.5f;
+  src.items.push_back(std::move(item));
+
+  src.strs.push_back("hello");
+  src.strs.push_back("world");
+
+  flatbuffers::FlatBufferBuilder fbb;
+  fbb.Finish(CppVecTest::Data::Pack(fbb, &src));
+
+  auto dst = CppVecTest::UnPackData(fbb.GetBufferPointer());
+
+  TEST_EQ(dst->values.size(), 3U);
+  TEST_EQ(dst->values[0], 10);
+  TEST_EQ(dst->values[1], 20);
+  TEST_EQ(dst->values[2], 30);
+
+  TEST_EQ(dst->items.size(), 1U);
+  TEST_EQ(dst->items[0]->id, 42);
+  TEST_EQ(dst->items[0]->value, 1.5f);
+
+  TEST_EQ(dst->strs.size(), 2U);
+  TEST_EQ(dst->strs[0], std::string("hello"));
+  TEST_EQ(dst->strs[1], std::string("world"));
+
+  TEST_EQ(dst->regular.size(), 0U);
+  TEST_ASSERT(*dst == *dst);
+}
+
+void CppVecTypeNativeTypeTest() {
+  // Verify that combining cpp_vec_type + native_type on a vector of structs
+  // produces the correct container type in the NativeTable.
+  static_assert(
+      std::is_same<
+          decltype(CppVecNativeTypeTest::ContainerT{}.points),
+          CppVecNativeTypeTest::CustomVec<
+              CppVecNativeTypeTest::Native::Vec3>>::value,
+      "points should be CustomVec<Native::Vec3>");
+  static_assert(
+      std::is_same<decltype(CppVecNativeTypeTest::ContainerT{}.bytes),
+                   CppVecNativeTypeTest::CustomVec<uint8_t>>::value,
+      "bytes should be CustomVec<uint8_t>");
+
+  const int N = 3;
+  CppVecNativeTypeTest::ContainerT src;
+  for (int i = 0; i < N; ++i) {
+    src.points.push_back(
+        CppVecNativeTypeTest::Native::Vec3(1.0f * i, 2.0f * i, 3.0f * i));
+    src.bytes.push_back(static_cast<uint8_t>(i * 10));
+  }
+
+  flatbuffers::FlatBufferBuilder fbb;
+  fbb.Finish(CppVecNativeTypeTest::Container::Pack(fbb, &src));
+
+  auto dst =
+      CppVecNativeTypeTest::UnPackContainer(fbb.GetBufferPointer());
+
+  TEST_EQ(dst->points.size(), static_cast<size_t>(N));
+  for (int i = 0; i < N; ++i) {
+    TEST_EQ(dst->points[i].x, 1.0f * i);
+    TEST_EQ(dst->points[i].y, 2.0f * i);
+    TEST_EQ(dst->points[i].z, 3.0f * i);
+  }
+
+  TEST_EQ(dst->bytes.size(), static_cast<size_t>(N));
+  for (int i = 0; i < N; ++i) {
+    TEST_EQ(dst->bytes[i], static_cast<uint8_t>(i * 10));
+  }
+}
+
 // Guard against -Wunused-function on platforms without file tests.
 #ifndef FLATBUFFERS_NO_FILE_TESTS
 // VS10 does not support typed enums, exclude from tests
@@ -1813,6 +1918,8 @@ int FlatBufferTests(const std::string& tests_data_path) {
   InvalidFloatTest();
   FixedLengthArrayTest();
   NativeTypeTest();
+  CppVecTypeTest();
+  CppVecTypeNativeTypeTest();
   OptionalScalarsTest();
   ParseFlexbuffersFromJsonWithNullTest();
   FlatbuffersSpanTest();