[C++] Static assert on Flatbuffers Version (#7203)

* Static assert on Flatbuffers Version

* add comment

include/flatbuffers/reflection_generated.h

@@ -6,6 +6,13 @@
 
 #include "flatbuffers/flatbuffers.h"
 
+// Ensure the included flatbuffers.h is the same version as when this file was
+// generated, otherwise it may not be compatible.
+static_assert(FLATBUFFERS_VERSION_MAJOR == 2 &&
+              FLATBUFFERS_VERSION_MINOR == 0 &&
+              FLATBUFFERS_VERSION_REVISION == 6,
+             "Non-compatible flatbuffers version included");
+
 namespace reflection {
 
 struct Type;

samples/monster_generated.h

@@ -6,6 +6,13 @@
 
 #include "flatbuffers/flatbuffers.h"
 
+// Ensure the included flatbuffers.h is the same version as when this file was
+// generated, otherwise it may not be compatible.
+static_assert(FLATBUFFERS_VERSION_MAJOR == 2 &&
+              FLATBUFFERS_VERSION_MINOR == 0 &&
+              FLATBUFFERS_VERSION_REVISION == 6,
+             "Non-compatible flatbuffers version included");
+
 namespace MyGame {
 namespace Sample {
 

src/idl_gen_cpp.cpp

@@ -16,8 +16,10 @@
 
 // independent from idl_parser, since this code is not needed for most clients
 
+#include <string>
 #include <unordered_set>
 
+#include "flatbuffers/base.h"
 #include "flatbuffers/code_generators.h"
 #include "flatbuffers/flatbuffers.h"
 #include "flatbuffers/flatc.h"
@@ -199,6 +201,25 @@ class CppGenerator : public BaseGenerator {
     for (auto kw = keywords; *kw; kw++) keywords_.insert(*kw);
   }
 
+  // Adds code to check that the included flatbuffers.h is of the same version
+  // as the generated code. This check currently looks for exact version match,
+  // as we would guarantee that they are compatible, but in theory a newer
+  // version of flatbuffers.h should work with a old code gen if we do proper
+  // backwards support.
+  void GenFlatbuffersVersionCheck() {
+    code_ +=
+        "// Ensure the included flatbuffers.h is the same version as when this "
+        "file was";
+    code_ += "// generated, otherwise it may not be compatible.";
+    code_ += "static_assert(FLATBUFFERS_VERSION_MAJOR == " +
+             std::to_string(FLATBUFFERS_VERSION_MAJOR) + " &&";
+    code_ += "              FLATBUFFERS_VERSION_MINOR == " +
+             std::to_string(FLATBUFFERS_VERSION_MINOR) + " &&";
+    code_ += "              FLATBUFFERS_VERSION_REVISION == " +
+             std::to_string(FLATBUFFERS_VERSION_REVISION) + ",";
+    code_ += "             \"Non-compatible flatbuffers version included\");";
+  }
+
   void GenIncludeDependencies() {
     int num_includes = 0;
     if (opts_.generate_object_based_api) {
@@ -285,6 +306,8 @@ class CppGenerator : public BaseGenerator {
 
       code_ += "#include \"flatbuffers/flatbuffers.h\"";
       code_ += "";
+      GenFlatbuffersVersionCheck();
+      code_ += "";
 
       SetNameSpace(struct_def.defined_namespace);
       auto name = Name(struct_def);
@@ -349,6 +372,8 @@ class CppGenerator : public BaseGenerator {
       code_ += "#include \"flatbuffers/flexbuffers.h\"";
     }
     code_ += "";
+    GenFlatbuffersVersionCheck();
+    code_ += "";
 
     if (opts_.include_dependence_headers) { GenIncludeDependencies(); }
     GenExtraIncludes();

tests/arrays_test_generated.h

@@ -6,6 +6,13 @@
 
 #include "flatbuffers/flatbuffers.h"
 
+// Ensure the included flatbuffers.h is the same version as when this file was
+// generated, otherwise it may not be compatible.
+static_assert(FLATBUFFERS_VERSION_MAJOR == 2 &&
+              FLATBUFFERS_VERSION_MINOR == 0 &&
+              FLATBUFFERS_VERSION_REVISION == 6,
+             "Non-compatible flatbuffers version included");
+
 namespace MyGame {
 namespace Example {
 

tests/cpp17/generated_cpp17/monster_test_generated.h

@@ -7,6 +7,13 @@
 #include "flatbuffers/flatbuffers.h"
 #include "flatbuffers/flexbuffers.h"
 
+// Ensure the included flatbuffers.h is the same version as when this file was
+// generated, otherwise it may not be compatible.
+static_assert(FLATBUFFERS_VERSION_MAJOR == 2 &&
+              FLATBUFFERS_VERSION_MINOR == 0 &&
+              FLATBUFFERS_VERSION_REVISION == 6,
+             "Non-compatible flatbuffers version included");
+
 namespace MyGame {
 
 struct InParentNamespace;

tests/cpp17/generated_cpp17/optional_scalars_generated.h

@@ -6,6 +6,13 @@
 
 #include "flatbuffers/flatbuffers.h"
 
+// Ensure the included flatbuffers.h is the same version as when this file was
+// generated, otherwise it may not be compatible.
+static_assert(FLATBUFFERS_VERSION_MAJOR == 2 &&
+              FLATBUFFERS_VERSION_MINOR == 0 &&
+              FLATBUFFERS_VERSION_REVISION == 6,
+             "Non-compatible flatbuffers version included");
+
 namespace optional_scalars {
 
 struct ScalarStuff;

tests/cpp17/generated_cpp17/union_vector_generated.h

@@ -6,6 +6,13 @@
 
 #include "flatbuffers/flatbuffers.h"
 
+// Ensure the included flatbuffers.h is the same version as when this file was
+// generated, otherwise it may not be compatible.
+static_assert(FLATBUFFERS_VERSION_MAJOR == 2 &&
+              FLATBUFFERS_VERSION_MINOR == 0 &&
+              FLATBUFFERS_VERSION_REVISION == 6,
+             "Non-compatible flatbuffers version included");
+
 struct Attacker;
 struct AttackerBuilder;
 struct AttackerT;

tests/evolution_test/evolution_v1_generated.h

@@ -6,6 +6,13 @@
 
 #include "flatbuffers/flatbuffers.h"
 
+// Ensure the included flatbuffers.h is the same version as when this file was
+// generated, otherwise it may not be compatible.
+static_assert(FLATBUFFERS_VERSION_MAJOR == 2 &&
+              FLATBUFFERS_VERSION_MINOR == 0 &&
+              FLATBUFFERS_VERSION_REVISION == 6,
+             "Non-compatible flatbuffers version included");
+
 namespace Evolution {
 namespace V1 {
 

tests/evolution_test/evolution_v2_generated.h

@@ -6,6 +6,13 @@
 
 #include "flatbuffers/flatbuffers.h"
 
+// Ensure the included flatbuffers.h is the same version as when this file was
+// generated, otherwise it may not be compatible.
+static_assert(FLATBUFFERS_VERSION_MAJOR == 2 &&
+              FLATBUFFERS_VERSION_MINOR == 0 &&
+              FLATBUFFERS_VERSION_REVISION == 6,
+             "Non-compatible flatbuffers version included");
+
 namespace Evolution {
 namespace V2 {
 

tests/monster_extra_generated.h

@@ -6,6 +6,13 @@
 
 #include "flatbuffers/flatbuffers.h"
 
+// Ensure the included flatbuffers.h is the same version as when this file was
+// generated, otherwise it may not be compatible.
+static_assert(FLATBUFFERS_VERSION_MAJOR == 2 &&
+              FLATBUFFERS_VERSION_MINOR == 0 &&
+              FLATBUFFERS_VERSION_REVISION == 6,
+             "Non-compatible flatbuffers version included");
+
 namespace MyGame {
 
 struct MonsterExtra;

tests/monster_test_bfbs_generated.h

@@ -6,6 +6,13 @@
 
 #include "flatbuffers/flatbuffers.h"
 
+// Ensure the included flatbuffers.h is the same version as when this file was
+// generated, otherwise it may not be compatible.
+static_assert(FLATBUFFERS_VERSION_MAJOR == 2 &&
+              FLATBUFFERS_VERSION_MINOR == 0 &&
+              FLATBUFFERS_VERSION_REVISION == 6,
+             "Non-compatible flatbuffers version included");
+
 namespace MyGame {
 namespace Example {
 

tests/monster_test_generated.h

@@ -7,6 +7,13 @@
 #include "flatbuffers/flatbuffers.h"
 #include "flatbuffers/flexbuffers.h"
 
+// Ensure the included flatbuffers.h is the same version as when this file was
+// generated, otherwise it may not be compatible.
+static_assert(FLATBUFFERS_VERSION_MAJOR == 2 &&
+              FLATBUFFERS_VERSION_MINOR == 0 &&
+              FLATBUFFERS_VERSION_REVISION == 6,
+             "Non-compatible flatbuffers version included");
+
 namespace MyGame {
 
 struct InParentNamespace;

tests/namespace_test/namespace_test1_generated.h

@@ -6,6 +6,13 @@
 
 #include "flatbuffers/flatbuffers.h"
 
+// Ensure the included flatbuffers.h is the same version as when this file was
+// generated, otherwise it may not be compatible.
+static_assert(FLATBUFFERS_VERSION_MAJOR == 2 &&
+              FLATBUFFERS_VERSION_MINOR == 0 &&
+              FLATBUFFERS_VERSION_REVISION == 6,
+             "Non-compatible flatbuffers version included");
+
 namespace NamespaceA {
 namespace NamespaceB {
 

tests/namespace_test/namespace_test2_generated.h

@@ -6,6 +6,13 @@
 
 #include "flatbuffers/flatbuffers.h"
 
+// Ensure the included flatbuffers.h is the same version as when this file was
+// generated, otherwise it may not be compatible.
+static_assert(FLATBUFFERS_VERSION_MAJOR == 2 &&
+              FLATBUFFERS_VERSION_MINOR == 0 &&
+              FLATBUFFERS_VERSION_REVISION == 6,
+             "Non-compatible flatbuffers version included");
+
 namespace NamespaceA {
 
 struct TableInFirstNS;

tests/native_type_test_generated.h

@@ -6,6 +6,13 @@
 
 #include "flatbuffers/flatbuffers.h"
 
+// Ensure the included flatbuffers.h is the same version as when this file was
+// generated, otherwise it may not be compatible.
+static_assert(FLATBUFFERS_VERSION_MAJOR == 2 &&
+              FLATBUFFERS_VERSION_MINOR == 0 &&
+              FLATBUFFERS_VERSION_REVISION == 6,
+             "Non-compatible flatbuffers version included");
+
 #include "native_type_test_impl.h"
 
 namespace Geometry {

tests/optional_scalars_generated.h

@@ -6,6 +6,13 @@
 
 #include "flatbuffers/flatbuffers.h"
 
+// Ensure the included flatbuffers.h is the same version as when this file was
+// generated, otherwise it may not be compatible.
+static_assert(FLATBUFFERS_VERSION_MAJOR == 2 &&
+              FLATBUFFERS_VERSION_MINOR == 0 &&
+              FLATBUFFERS_VERSION_REVISION == 6,
+             "Non-compatible flatbuffers version included");
+
 namespace optional_scalars {
 
 struct ScalarStuff;

tests/union_vector/union_vector_generated.h

@@ -6,6 +6,13 @@
 
 #include "flatbuffers/flatbuffers.h"
 
+// Ensure the included flatbuffers.h is the same version as when this file was
+// generated, otherwise it may not be compatible.
+static_assert(FLATBUFFERS_VERSION_MAJOR == 2 &&
+              FLATBUFFERS_VERSION_MINOR == 0 &&
+              FLATBUFFERS_VERSION_REVISION == 6,
+             "Non-compatible flatbuffers version included");
+
 struct Attacker;
 struct AttackerBuilder;
 struct AttackerT;