Removing _LIBCPP_DISABLE_UNUSED_STRUCT_WARNINGS from libc++ enables

`[[gnu::__warn_unused__]]` on standard library types (such as
`std::string` and `std::set`), surfacing `-Wunused-variable` warnings
in `//third_party/flatbuffers`. See [upstream LLVM commit](https://github.com/llvm/llvm-project/commit/ab8b037ef7b398aa864959a69f328fa69b567f74) for reference.

Remove unreferenced variable declarations across the code generators and
binary annotator whose initializers have no observable side effects.

PiperOrigin-RevId: 999136370

Package.swift

@@ -75,6 +75,17 @@ extension Array where Element == Package.Dependency {
       .package(
         url: "https://github.com/grpc/grpc-swift-nio-transport.git",
         from: "2.0.0"),
+      // swift-crypto arrives through grpc-swift-nio-transport -> swift-nio-ssl
+      // and is otherwise resolved afresh on every build, because this package
+      // ships no Package.resolved. 5.x asks for swift-tools-version 6.2, so only
+      // the 6.2 CI job selects it - and then fails to compile it, because 5.x
+      // uses `@nonexhaustive`, which the 6.2.x toolchains do not accept yet.
+      // Stay on the last 4.x release that still builds with every toolchain in
+      // the Swift CI matrix (4.3.0 declares swift-tools-version 6.0; 4.4+ asks
+      // for 6.1 and would drop the 6.0 job).
+      .package(
+        url: "https://github.com/apple/swift-crypto.git",
+        "4.0.0" ..< "4.4.0"),
     ]
     #endif
   }

grpc/src/compiler/ts_generator.cc

@@ -504,7 +504,6 @@ grpc::string GenerateInterface(grpc_generator::File* file,
                                const grpc::string& filename) {
   grpc::string output;
 
-  std::set<grpc::string> generated_functions;
   std::map<grpc::string, grpc::string> vars;
 
   vars["PATH"] = file->package();

include/flatbuffers/base.h

@@ -271,7 +271,7 @@ namespace flatbuffers {
   #if (defined(_MSC_VER) && _MSC_VER >= 1800) || \
       (defined(__ANDROID__) && defined(__ANDROID_API__) && __ANDROID_API__>= 26) || \
       (defined(_XOPEN_VERSION) && (_XOPEN_VERSION >= 700)) && \
-      !defined(__Fuchsia__)
+      !defined(__Fuchsia__) && (!defined(__linux__) || defined(__GLIBC__))
     #define FLATBUFFERS_LOCALE_INDEPENDENT 1
   #else
     #define FLATBUFFERS_LOCALE_INDEPENDENT 0

lobster/flatbuffers.lobster

@@ -24,15 +24,14 @@ class handle:
 struct offset:
     o:int
 
-enum sizeof:
+let sz_8 = 1
-    sz_8 = 1
+let sz_16 = 2
-    sz_16 = 2
+let sz_32 = 4
-    sz_32 = 4
+let sz_64 = 8
-    sz_64 = 8
+let sz_voffset = 2
-    sz_voffset = 2
+let sz_uoffset = 4
-    sz_uoffset = 4
+let sz_soffset = 4
-    sz_soffset = 4
+let sz_metadata_fields = 2
-    sz_metadata_fields = 2
 
 class builder:
     buf = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"

src/binary_annotator.cpp

@@ -722,8 +722,6 @@ void BinaryAnnotator::BuildTable(const uint64_t table_offset,
     BinaryRegionComment offset_field_comment;
     offset_field_comment.type = BinaryRegionCommentType::TableOffsetField;
     offset_field_comment.name = field->name()->c_str();
-    const std::string offset_prefix =
-        "offset to field `" + std::string(field->name()->c_str()) + "`";
 
     // Validate any field that isn't inline (i.e., non-structs).
     if (!IsInlineField(field)) {

src/idl_gen_cpp.cpp

@@ -404,7 +404,7 @@ class CppGenerator : public BaseGenerator {
       code_ += "struct {{STRUCT_NAME}}BinarySchema {";
       code_ += "  static const uint8_t *data() {";
       code_ += "    // Buffer containing the binary schema.";
-      code_ += "    static const uint8_t bfbsData[" +
+      code_ += "    alignas(uint64_t) static const uint8_t bfbsData[" +
                NumToString(parser_.builder_.GetSize()) + "] = {";
       code_ += binary_schema_hex_text;
       code_ += "    };";
@@ -2737,7 +2737,6 @@ class CppGenerator : public BaseGenerator {
     if (!field.IsScalarOptional()) {
       const bool is_scalar = IsScalar(type.base_type);
       std::string accessor;
-      std::string offset_size = "";
       if (is_scalar) {
         accessor = "GetField<";
       } else if (IsStruct(type)) {
@@ -2815,7 +2814,6 @@ class CppGenerator : public BaseGenerator {
 
   void GenTableFieldType(const FieldDef& field) {
     const auto& type = field.value.type;
-    const auto offset_str = GenFieldOffsetName(field);
     if (!field.IsScalarOptional()) {
       std::string afterptr = " *" + NullableExtension();
       code_.SetValue("FIELD_TYPE",

src/idl_gen_dart.cpp

@@ -1149,8 +1149,6 @@ static bool GenerateDart(const Parser& parser, const std::string& path,
 
 static std::string DartMakeRule(const Parser& parser, const std::string& path,
                                 const std::string& file_name) {
-  auto filebase =
-      flatbuffers::StripPath(flatbuffers::StripExtension(file_name));
   dart::DartGenerator generator(parser, path, file_name);
   auto make_rule = generator.Filename("") + ": ";
 

src/idl_gen_kotlin.cpp

@@ -966,8 +966,6 @@ class KotlinGenerator : public BaseGenerator {
       auto bbgetter = ByteBufferGetter(field.value.type, "bb");
       auto ucast = CastToUsigned(field);
       auto offset_val = NumToString(field.value.offset);
-      auto offset_prefix =
-          "val o = __offset(" + offset_val + "); return o != 0 ? ";
       auto value_base_type = field.value.type.base_type;
       // Most field accessors need to retrieve and test the field offset
       // first, this is the offset value for that:

src/idl_gen_kotlin_kmp.cpp

@@ -146,7 +146,6 @@ class KotlinKMPGenerator : public BaseGenerator {
 
     std::string code =
         "// " + std::string(FlatBuffersGeneratedWarning()) + "\n\n";
-    auto qualified = ns.GetFullyQualifiedName("");
     std::string namespace_name = namer_.Namespace(ns);
     if (!namespace_name.empty()) {
       code += "package " + namespace_name;
@@ -341,7 +340,6 @@ class KotlinKMPGenerator : public BaseGenerator {
   std::string GenDefaultBufferValue(const FieldDef& field) const {
     auto& value = field.value;
     auto base_type = value.type.base_type;
-    auto field_name = field.name;
     std::string suffix = IsScalar(base_type) ? LiteralSuffix(value.type) : "";
     if (field.IsScalarOptional()) {
       return "null";
@@ -373,7 +371,6 @@ class KotlinKMPGenerator : public BaseGenerator {
   std::string GenDefaultValue(const FieldDef& field) const {
     auto& value = field.value;
     auto base_type = value.type.base_type;
-    auto field_name = field.name;
     std::string suffix = LiteralSuffix(value.type);
     if (field.IsScalarOptional()) {
       return "null";
@@ -1082,8 +1079,6 @@ class KotlinKMPGenerator : public BaseGenerator {
       auto return_type = GetterReturnType(field);
       auto bbgetter = ByteBufferGetter(field.value.type, "bb");
       auto offset_val = NumToString(field.value.offset);
-      auto offset_prefix =
-          "val o = offset(" + offset_val + "); return o != 0 ? ";
       auto value_base_type = field.value.type.base_type;
       // Most field accessors need to retrieve and test the field offset
       // first, this is the offset value for that:

src/idl_gen_python.cpp

@@ -2010,8 +2010,6 @@ class PythonGenerator : public BaseGenerator {
   void InitializeFromPackedBuf(const StructDef& struct_def,
                                std::string* code_ptr) const {
     auto& code = *code_ptr;
-    const auto struct_var = namer_.Variable(struct_def);
-    const auto struct_type = namer_.Type(struct_def);
 
     code += GenIndents(1) + "@classmethod";
     code += GenIndents(1) + "def InitFromPackedBuf(cls, buf, pos=0):";

src/idl_gen_swift.cpp

@@ -787,7 +787,6 @@ class SwiftGenerator : public BaseGenerator {
   }
 
   void GenTableReaderFields(const FieldDef& field) {
-    const auto offset = NumToString(field.value.offset);
     const auto field_field = namer_.Field(field);
     const auto type = GenType(field.value.type);
     code_.SetValue("FIELDVAR", namer_.Variable(field));
@@ -1382,7 +1381,6 @@ class SwiftGenerator : public BaseGenerator {
       const auto& field = **it;
       if (field.deprecated) continue;
 
-      const auto type = GenType(field.value.type);
       code_.SetValue("FIELDVAR", namer_.Variable(field));
       if (IsArray(field.value.type)) {
         code_.SetValue(

src/idl_gen_ts.cpp

@@ -196,7 +196,6 @@ class TsGenerator : public BaseGenerator {
                                 SkipDir::OutputPathAndTrailingPathSeparator);
       symbolic_name = definition.defined_namespace->components.back();
     } else {
-      auto def_mod_name = namer_.File(definition, SkipFile::SuffixAndExtension);
       symbolic_name = file_name_;
       filepath = path_ + symbolic_name + ".ts";
     }
@@ -286,12 +285,10 @@ class TsGenerator : public BaseGenerator {
         auto base_name =
             namer_.Directories(it.second.ns->components, SkipDir::OutputPath) +
             base_file_name;
-        auto ts_file_path = base_name + ".ts";
         auto base_name_rel = std::string("./");
         base_name_rel +=
             namer_.Directories(rel_components, SkipDir::OutputPath);
         base_name_rel += base_file_name;
-        auto ts_file_path_rel = base_name_rel + ".ts";
         auto type_name = def.first;
         auto fully_qualified_type_name =
             it.second.ns->GetFullyQualifiedName(type_name);
@@ -311,7 +308,6 @@ class TsGenerator : public BaseGenerator {
       const auto child_ns_level = it.second.ns->components.size() + 1;
       for (const auto& it2 : ns_defs_) {
         if (it2.second.ns->components.size() != child_ns_level) continue;
-        auto ts_file_path = it2.second.path + ".ts";
         code += "export * as " + it2.second.symbolic_name + " from './";
         int count = it2.second.ns->components.size() > 1 ? 2 : 1;
         std::vector<std::string> rel_path;
@@ -1176,7 +1172,6 @@ class TsGenerator : public BaseGenerator {
     if (union_type.enum_def) {
       const auto& enum_def = *union_type.enum_def;
       const auto enum_type = AddImport(imports, dependent, enum_def).name;
-      const std::string union_accessor = "this." + field_name;
 
       const auto union_has_string = UnionHasStringType(enum_def);
       const auto field_binded_method = "this." + field_name + ".bind(this)";

swift/Sources/FlatBuffers/Root.swift

@@ -16,6 +16,30 @@
 
 import Foundation
 
+@inline(__always)
+private func verifySizePrefix(
+  byteBuffer: inout ByteBuffer,
+  requireExactSize: Bool,
+  options: VerifierOptions) throws
+{
+  let verifier = try Verifier(buffer: &byteBuffer, options: options)
+  let prefixPosition = byteBuffer.reader
+  let prefix: UOffset = try verifier.getValue(at: prefixPosition)
+  let availableSize = byteBuffer.size &- UOffset(MemoryLayout<UOffset>.size)
+
+  if requireExactSize {
+    guard prefix == availableSize else {
+      throw FlatbuffersErrors.prefixedSizeNotEqualToBufferSize
+    }
+  } else if prefix > availableSize {
+    throw FlatbuffersErrors.outOfBounds(
+      position: UInt(prefixPosition)
+        &+ UInt(MemoryLayout<UOffset>.size)
+        &+ UInt(prefix),
+      end: byteBuffer.capacity)
+  }
+}
+
 /// Takes in a prefixed sized buffer, where the prefixed size would be skipped.
 /// And would verify that the buffer passed is a valid `Flatbuffers` Object.
 /// - Parameters:
@@ -31,6 +55,10 @@ public func getPrefixedSizeCheckedRoot<T: FlatBufferTable & Verifiable>(
   fileId: String? = nil,
   options: VerifierOptions = .init()) throws -> T
 {
+  try verifySizePrefix(
+    byteBuffer: &byteBuffer,
+    requireExactSize: false,
+    options: options)
   byteBuffer.skipPrefix()
   return try getCheckedRoot(
     byteBuffer: &byteBuffer,
@@ -53,10 +81,11 @@ public func getCheckedPrefixedSizeRoot<T: FlatBufferTable & Verifiable>(
   fileId: String? = nil,
   options: VerifierOptions = .init()) throws -> T
 {
-  let prefix = byteBuffer.skipPrefix()
+  try verifySizePrefix(
-  if prefix != byteBuffer.size {
+    byteBuffer: &byteBuffer,
-    throw FlatbuffersErrors.prefixedSizeNotEqualToBufferSize
+    requireExactSize: true,
-  }
+    options: options)
+  byteBuffer.skipPrefix()
   return try getCheckedRoot(
     byteBuffer: &byteBuffer,
     fileId: fileId,
@@ -95,14 +124,15 @@ public func getCheckedRoot<T: FlatBufferTable & Verifiable>(
   options: VerifierOptions = .init()) throws -> T
 {
   var verifier = try Verifier(buffer: &byteBuffer, options: options)
+  let rootPosition = byteBuffer.reader
   if let fileId = fileId {
-    try verifier.verify(id: fileId)
+    try verifier.verify(id: fileId, at: rootPosition)
   }
-  try ForwardOffset<T>.verify(&verifier, at: 0, of: T.self)
+  try ForwardOffset<T>.verify(&verifier, at: rootPosition, of: T.self)
   return T.init(
     byteBuffer,
-    o: Int32(byteBuffer.read(def: UOffset.self, position: byteBuffer.reader))
+    o: Int32(byteBuffer.read(def: UOffset.self, position: rootPosition))
-      &+ Int32(byteBuffer.reader))
+      &+ Int32(rootPosition))
 }
 
 /// Returns a `NON-Checked` flatbuffers object

swift/Sources/FlatBuffers/Verifier.swift

@@ -215,12 +215,16 @@ public struct Verifier {
   }
 
   @inline(__always)
-  func verify(id: String) throws {
+  func verify(id: String, at position: Int) throws {
     let size = MemoryLayout<Int32>.size
-    guard storage.capacity >= (size &* 2) else {
+    guard
+      position >= 0,
+      position <= storage.capacity,
+      storage.capacity - position >= size &* 2
+    else {
       throw FlatbuffersErrors.bufferDoesntContainID
     }
-    let str = _buffer.readString(at: size, count: size)
+    let str = _buffer.readString(at: position &+ size, count: size)
     if id == str {
       return
     }

tests/monster_test_bfbs_generated.h

@@ -12,7 +12,7 @@ namespace Example {
 struct MonsterBinarySchema {
   static const uint8_t *data() {
     // Buffer containing the binary schema.
-    static const uint8_t bfbsData[14520] = {
+    alignas(uint64_t) static const uint8_t bfbsData[14520] = {
       0x20,0x00,0x00,0x00,0x42,0x46,0x42,0x53,0x00,0x00,0x00,0x00,0x14,0x00,0x20,0x00,0x04,0x00,0x08,0x00,
       0x0C,0x00,0x10,0x00,0x14,0x00,0x18,0x00,0x00,0x00,0x1C,0x00,0x14,0x00,0x00,0x00,0x58,0x00,0x00,0x00,
       0x34,0x00,0x00,0x00,0x24,0x00,0x00,0x00,0x18,0x00,0x00,0x00,0x70,0x0D,0x00,0x00,0x08,0x00,0x00,0x00,

tests/swift/Tests/Flatbuffers/FlatbuffersVerifierTests.swift

@@ -373,6 +373,58 @@ final class FlatbuffersVerifierTests {
     }
   }
 
+  @Test
+  func testSizePrefixedVerifierUsesPostPrefixRoot() throws {
+    // The size prefix points to a valid empty decoy table at byte 44. The real
+    // root at byte 4 points to a truncated UInt64 vector that must be rejected.
+    let bytes: [UInt8] = [
+      44, 0, 0, 0,
+      16, 0, 0, 0,
+      6, 0, 8, 0, 4, 0,
+      0, 0, 0, 0, 0, 0,
+      12, 0, 0, 0,
+      8, 0, 0, 0, 0, 0, 0, 0,
+      2, 0, 0, 0, 65, 66,
+      0, 0,
+      4, 0, 4, 0,
+      4, 0, 0, 0,
+    ]
+
+    var strictBuffer = ByteBuffer(bytes: bytes)
+    #expect(throws: FlatbuffersErrors.self) {
+      try getCheckedPrefixedSizeRoot(
+        byteBuffer: &strictBuffer) as Swift_Tests_Vectors
+    }
+
+    var prefixedBuffer = ByteBuffer(bytes: bytes)
+    #expect(throws: FlatbuffersErrors.self) {
+      try getPrefixedSizeCheckedRoot(
+        byteBuffer: &prefixedBuffer) as Swift_Tests_Vectors
+    }
+
+    var builder = FlatBufferBuilder()
+    let movie = Movie.createMovie(&builder)
+    Movie.finish(&builder, end: movie, prefix: true)
+    var validBuffer = builder.sizedBuffer
+    let _: Movie = try getCheckedPrefixedSizeRoot(
+      byteBuffer: &validBuffer,
+      fileId: Movie.id)
+
+    var shortBuffer = ByteBuffer(bytes: [0, 0, 0, 0])
+    #expect(throws: FlatbuffersErrors.bufferDoesntContainID) {
+      try getCheckedRoot(
+        byteBuffer: &shortBuffer,
+        fileId: Movie.id) as Movie
+    }
+
+    var oversizedPrefix = ByteBuffer(bytes: [5, 0, 0, 0, 0, 0, 0, 0])
+    #expect(throws: FlatbuffersErrors.outOfBounds(position: 9, end: 8)) {
+      try getPrefixedSizeCheckedRoot(
+        byteBuffer: &oversizedPrefix) as Movie
+    }
+    #expect(oversizedPrefix.reader == 0)
+  }
+
   @Test
   func testFullVerifier() throws {
     _ =