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
   }

src/idl_gen_cpp.cpp

@@ -2814,7 +2814,6 @@ class CppGenerator : public BaseGenerator {
 
   void GenTableFieldType(const FieldDef& field) {
     const auto& type = field.value.type;
-    [[maybe_unused]] const auto offset_str = GenFieldOffsetName(field);
     if (!field.IsScalarOptional()) {
       std::string afterptr = " *" + NullableExtension();
       code_.SetValue("FIELD_TYPE",

src/idl_gen_java.cpp

@@ -2176,7 +2176,7 @@ class JavaGenerator : public BaseGenerator {
       if (field.deprecated) continue;
       if (field.value.type.base_type == BASE_TYPE_UTYPE) continue;
       if (field.value.type.element == BASE_TYPE_UTYPE) continue;
-      [[maybe_unused]] const auto get_field = namer_.Method("get", field);
+      const auto get_field = namer_.Method("get", field);
 
       code += "    this." + namer_.Field(field) + " = ";
       const auto type_name =

src/idl_gen_kotlin_kmp.cpp

@@ -146,7 +146,6 @@ class KotlinKMPGenerator : public BaseGenerator {
 
     std::string code =
         "// " + std::string(FlatBuffersGeneratedWarning()) + "\n\n";
-    [[maybe_unused]] auto qualified = ns.GetFullyQualifiedName("");
     std::string namespace_name = namer_.Namespace(ns);
     if (!namespace_name.empty()) {
       code += "package " + namespace_name;

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;
-    [[maybe_unused]] const auto struct_var = namer_.Variable(struct_def);
-    [[maybe_unused]] 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

@@ -1141,6 +1141,7 @@ class SwiftGenerator : public BaseGenerator {
          it != struct_def.fields.vec.end(); ++it) {
       const auto& field = **it;
       if (field.deprecated) continue;
+      const auto offset = NumToString(field.value.offset);
 
       code_.SetValue("FIELDVAR", namer_.Variable(field));
       code_.SetValue("VALUETYPE", GenerateVerifierType(field));
@@ -1380,7 +1381,6 @@ class SwiftGenerator : public BaseGenerator {
       const auto& field = **it;
       if (field.deprecated) continue;
 
-      [[maybe_unused]] 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

@@ -196,8 +196,6 @@ class TsGenerator : public BaseGenerator {
                                 SkipDir::OutputPathAndTrailingPathSeparator);
       symbolic_name = definition.defined_namespace->components.back();
     } else {
-      [[maybe_unused]] auto def_mod_name =
-          namer_.File(definition, SkipFile::SuffixAndExtension);
       symbolic_name = file_name_;
       filepath = path_ + symbolic_name + ".ts";
     }
@@ -287,7 +285,6 @@ class TsGenerator : public BaseGenerator {
         auto base_name =
             namer_.Directories(it.second.ns->components, SkipDir::OutputPath) +
             base_file_name;
-        [[maybe_unused]] auto ts_file_path = base_name + ".ts";
         auto base_name_rel = std::string("./");
         base_name_rel +=
             namer_.Directories(rel_components, SkipDir::OutputPath);

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,