Merge branch 'master' into master

Author: bjornharrtell

.github/workflows/build.yml

@@ -310,14 +310,17 @@ jobs:
 
   build-android:
    name: Build Android (on Linux)
+   if: false #disabled due to continual failure
    runs-on: ubuntu-24.04
    steps:
    - uses: actions/checkout@v3
    - name: set up Java
-     uses: actions/setup-java@v3
+     uses: actions/setup-java@v4
      with:
-       distribution: 'temurin'
-       java-version: '11'
+       distribution: temurin
+       java-version: 17
+   - name: set up Gradle
+     uses: gradle/actions/setup-gradle@v4
    - name: set up flatc
      run: |
        cmake -DFLATBUFFERS_BUILD_TESTS=OFF -DFLATBUFFERS_BUILD_FLATLIB=OFF -DFLATBUFFERS_BUILD_FLATHASH=OFF -DFLATBUFFERS_STRICT_MODE=ON .
@@ -398,11 +401,13 @@ jobs:
       # https://github.com/actions/runner-images/blob/main/images/macos/macos-13-Readme.md#xcode
     - name: Set up Xcode version
       run: sudo xcode-select -s /Applications/Xcode_14.3.app/Contents/Developer
-    - uses: gradle/wrapper-validation-action@v1.0.5
-    - uses: actions/setup-java@v3
+    - name: set up Java
+      uses: actions/setup-java@v4
       with:
-        distribution: 'temurin'
-        java-version: '11'
+        distribution: temurin
+        java-version: 17
+    - name: set up Gradle
+      uses: gradle/actions/setup-gradle@v4
     - name: Build flatc
       run: |
        cmake -DFLATBUFFERS_BUILD_TESTS=OFF -DFLATBUFFERS_BUILD_FLATLIB=OFF -DFLATBUFFERS_BUILD_FLATHASH=OFF .
@@ -414,15 +419,18 @@ jobs:
 
   build-kotlin-linux:
     name: Build Kotlin Linux
+    if: false #disabled due to continual failure
     runs-on: ubuntu-24.04
     steps:
     - name: Checkout
       uses: actions/checkout@v3
-    - uses: actions/setup-java@v3
+    - name: set up Java
+      uses: actions/setup-java@v4
       with:
-        distribution: 'temurin'
-        java-version: '11'
-    - uses: gradle/wrapper-validation-action@v1.0.5
+        distribution: temurin
+        java-version: 17
+    - name: set up Gradle
+      uses: gradle/actions/setup-gradle@v4
     - name: Build flatc
       run: |
        cmake -DFLATBUFFERS_BUILD_TESTS=OFF -DFLATBUFFERS_BUILD_FLATLIB=OFF -DFLATBUFFERS_BUILD_FLATHASH=OFF .
@@ -518,6 +526,8 @@ jobs:
       - uses: SwiftyLab/setup-swift@latest
         with:
           swift-version: '6.1'
+          # To be removed when swiftylab fixes the CI
+          visual-studio-components: Microsoft.VisualStudio.Component.Windows11SDK.22621
       - run: swift build
       - run: swift test
 

CHANGELOG.md

@@ -4,6 +4,10 @@ All major or breaking changes will be documented in this file, as well as any
 new features that should be highlighted. Minor fixes or improvements are not
 necessarily listed.
 
+## Unreleased
+
+* flatc: `--grpc-callback-api` flag generates C++ gRPC Callback API server `CallbackService` skeletons AND client native callback/async stubs (unary + all streaming reactor forms) (opt-in, non-breaking, issue #8596).
+
 ## [25.2.10] (February 10 2025)(https://github.com/google/flatbuffers/releases/tag/v25.2.10)
 
 * Removed the old documentation pages. The new one is live at https://flatbuffers.dev

CMakeLists.txt

@@ -279,6 +279,8 @@ set(FlatBuffers_GRPCTest_SRCS
   tests/test_builder.cpp
   grpc/tests/grpctest.cpp
   grpc/tests/message_builder_test.cpp
+  grpc/tests/grpctest_callback_compile.cpp
+  grpc/tests/grpctest_callback_client_compile.cpp
 )
 
 # TODO(dbaileychess): Figure out how this would now work. I posted a question on

go/grpc.go

@@ -1,7 +1,17 @@
 package flatbuffers
 
-// Codec implements gRPC-go Codec which is used to encode and decode messages.
-var Codec = "flatbuffers"
+import "errors"
+
+var (
+	// Codec implements gRPC-go Codec which is used to encode and decode messages.
+	Codec = "flatbuffers"
+
+	// ErrInsufficientData is returned when the data is too short to read the root UOffsetT.
+	ErrInsufficientData = errors.New("insufficient data")
+
+	// ErrInvalidRootOffset is returned when the root UOffsetT is out of bounds.
+	ErrInvalidRootOffset = errors.New("invalid root offset")
+)
 
 // FlatbuffersCodec defines the interface gRPC uses to encode and decode messages.  Note
 // that implementations of this interface must be thread safe; a Codec's
@@ -15,7 +25,21 @@ func (FlatbuffersCodec) Marshal(v interface{}) ([]byte, error) {
 
 // Unmarshal parses the wire format into v.
 func (FlatbuffersCodec) Unmarshal(data []byte, v interface{}) error {
-	v.(flatbuffersInit).Init(data, GetUOffsetT(data))
+	// Need at least 4 bytes to read the root table offset (UOffsetT).
+	// Vtable soffset_t and metadata are read later during field access.
+	if len(data) < SizeUOffsetT {
+		return ErrInsufficientData
+	}
+
+	off := GetUOffsetT(data)
+
+	// The root UOffsetT must be within the data buffer
+	// Compare in the unsigned domain to avoid signedness pitfalls
+	if off > UOffsetT(len(data)-SizeUOffsetT) {
+		return ErrInvalidRootOffset
+	}
+
+	v.(flatbuffersInit).Init(data, off)
 	return nil
 }
 

grpc/README.md

@@ -1,5 +1,4 @@
 GRPC implementation and test
-============================
 
 NOTE: files in `src/` are shared with the GRPC project, and maintained there
 (any changes should be submitted to GRPC instead). These files are copied
@@ -39,4 +38,64 @@ For Bazel users:
 
 ```shell
 $bazel test tests/...
-```
+```
+
+## C++ Callback API Generation
+
+FlatBuffers gRPC C++ code generation now optionally supports the modern gRPC Callback API.
+
+To enable generation of a `CallbackService` skeleton alongside the existing `Service` and async mixins, invoke `flatc` with both `--grpc` and `--grpc-callback-api`:
+
+```shell
+flatc --cpp --grpc --grpc-callback-api your_service.fbs
+```
+
+This adds (guarded by `#if defined(GRPC_CALLBACK_API_NONEXPERIMENTAL)`) a class:
+
+```cpp
+class YourService::CallbackService : public ::grpc::Service { /* reactor virtuals */ };
+```
+
+Each RPC shape maps to the appropriate reactor return type:
+
+- Unary -> `::grpc::ServerUnaryReactor*` Method(...)
+- Client streaming -> `::grpc::ServerReadReactor<Request>*`
+- Server streaming -> `::grpc::ServerWriteReactor<Response>*`
+- Bidi streaming -> `::grpc::ServerBidiReactor<Request, Response>*`
+
+Default generated implementations return `nullptr`; override in your derived class and return a reactor instance you manage (see gRPC docs for lifecycle patterns).
+
+If your gRPC library predates the stable callback API macro, the code inside the guard will be skipped (no breaking changes). Ensure you build against a recent gRPC (1.38+; verify current minimum in grpc repo) to use this feature.
+
+### Client Callback Stubs
+
+When `--grpc-callback-api` is supplied, the generated C++ client stub gains native callback / reactor based async methods in addition to the existing synchronous / generic async flavors, guarded by the same macro. For each RPC named `Foo`:
+
+Unary:
+
+```
+void async_Foo(::grpc::ClientContext*, const Request&, Response*, std::function<void(::grpc::Status)>);
+void async_Foo(::grpc::ClientContext*, const Request&, Response*, ::grpc::ClientUnaryReactor*);
+```
+
+Client streaming:
+
+```
+::grpc::ClientWriteReactor<Request>* async_Foo(::grpc::ClientContext*, Response*, ::grpc::ClientWriteReactor<Request>*);
+```
+
+Server streaming:
+
+```
+::grpc::ClientReadReactor<Response>* async_Foo(::grpc::ClientContext*, const Request&, ::grpc::ClientReadReactor<Response>*);
+```
+
+Bidirectional streaming:
+
+```
+::grpc::ClientBidiReactor<Request, Response>* async_Foo(::grpc::ClientContext*, ::grpc::ClientBidiReactor<Request, Response>*);
+```
+
+These map directly onto the native gRPC callback API factories (e.g. `CallbackUnaryCall`, `ClientCallbackWriterFactory::Create`, etc.) and do not spawn threads. Override the appropriate reactor callbacks per gRPC's documentation to drive I/O.
+
+If your build uses an older gRPC lacking the non-experimental macro, these symbols will not be emitted, preserving backwards compatibility.