../deps/v8/src/wasm/wasm-module.h

Bug Summary

File:	out/../deps/v8/src/wasm/wasm-module.h
Warning:	line 443, column 35 Forming reference to null pointer

Annotated Source Code

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clang -cc1 -cc1 -triple x86_64-unknown-linux-gnu -analyze -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name module-decoder.cc -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=all -relaxed-aliasing -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -ffunction-sections -fdata-sections -fcoverage-compilation-dir=/home/maurizio/node-v18.6.0/out -resource-dir /usr/local/lib/clang/16.0.0 -D _GLIBCXX_USE_CXX11_ABI=1 -D NODE_OPENSSL_CONF_NAME=nodejs_conf -D NODE_OPENSSL_HAS_QUIC -D V8_GYP_BUILD -D V8_TYPED_ARRAY_MAX_SIZE_IN_HEAP=64 -D __STDC_FORMAT_MACROS -D OPENSSL_NO_PINSHARED -D OPENSSL_THREADS -D V8_TARGET_ARCH_X64 -D V8_HAVE_TARGET_OS -D V8_TARGET_OS_LINUX -D V8_EMBEDDER_STRING="-node.8" -D ENABLE_DISASSEMBLER -D V8_PROMISE_INTERNAL_FIELD_COUNT=1 -D V8_SHORT_BUILTIN_CALLS -D OBJECT_PRINT -D V8_INTL_SUPPORT -D V8_ATOMIC_OBJECT_FIELD_WRITES -D V8_ENABLE_LAZY_SOURCE_POSITIONS -D V8_USE_SIPHASH -D V8_SHARED_RO_HEAP -D V8_WIN64_UNWINDING_INFO -D V8_ENABLE_REGEXP_INTERPRETER_THREADED_DISPATCH -D V8_SNAPSHOT_COMPRESSION -D V8_ENABLE_WEBASSEMBLY -D V8_ENABLE_JAVASCRIPT_PROMISE_HOOKS -D V8_ALLOCATION_FOLDING -D V8_ALLOCATION_SITE_TRACKING -D V8_SCRIPTORMODULE_LEGACY_LIFETIME -D V8_ADVANCED_BIGINT_ALGORITHMS -D ICU_UTIL_DATA_IMPL=ICU_UTIL_DATA_STATIC -D UCONFIG_NO_SERVICE=1 -D U_ENABLE_DYLOAD=0 -D U_STATIC_IMPLEMENTATION=1 -D U_HAVE_STD_STRING=1 -D UCONFIG_NO_BREAK_ITERATION=0 -I ../deps/v8 -I ../deps/v8/include -I /home/maurizio/node-v18.6.0/out/Release/obj/gen/inspector-generated-output-root -I ../deps/v8/third_party/inspector_protocol -I /home/maurizio/node-v18.6.0/out/Release/obj/gen -I /home/maurizio/node-v18.6.0/out/Release/obj/gen/generate-bytecode-output-root -I ../deps/icu-small/source/i18n -I ../deps/icu-small/source/common -I ../deps/v8/third_party/zlib -I ../deps/v8/third_party/zlib/google -internal-isystem /usr/lib/gcc/x86_64-redhat-linux/8/../../../../include/c++/8 -internal-isystem /usr/lib/gcc/x86_64-redhat-linux/8/../../../../include/c++/8/x86_64-redhat-linux -internal-isystem /usr/lib/gcc/x86_64-redhat-linux/8/../../../../include/c++/8/backward -internal-isystem /usr/local/lib/clang/16.0.0/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-redhat-linux/8/../../../../x86_64-redhat-linux/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -O3 -Wno-unused-parameter -Wno-return-type -std=gnu++17 -fdeprecated-macro -fdebug-compilation-dir=/home/maurizio/node-v18.6.0/out -ferror-limit 19 -fno-rtti -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -analyzer-output=html -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/scan-build-2022-08-22-142216-507842-1 -x c++ ../deps/v8/src/wasm/module-decoder.cc

../deps/v8/src/wasm/module-decoder.cc

→

1// Copyright 2015 the V8 project authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.

5#include "src/wasm/module-decoder.h"

7#include "src/base/functional.h"
8#include "src/base/platform/platform.h"
9#include "src/base/platform/wrappers.h"
10#include "src/flags/flags.h"
11#include "src/init/v8.h"
12#include "src/logging/counters.h"
13#include "src/logging/metrics.h"
14#include "src/objects/objects-inl.h"
15#include "src/utils/ostreams.h"
16#include "src/wasm/canonical-types.h"
17#include "src/wasm/decoder.h"
18#include "src/wasm/function-body-decoder-impl.h"
19#include "src/wasm/init-expr-interface.h"
20#include "src/wasm/struct-types.h"
21#include "src/wasm/wasm-constants.h"
22#include "src/wasm/wasm-engine.h"
23#include "src/wasm/wasm-limits.h"
24#include "src/wasm/wasm-opcodes-inl.h"

26namespace v8 {
27namespace internal {
28namespace wasm {

30#define TRACE(...)                                    \
do {                                                \
  if (FLAG_trace_wasm_decoder) PrintF(__VA_ARGS__); \
} while (false)

35namespace {

37constexpr char kNameString[] = "name";
38constexpr char kSourceMappingURLString[] = "sourceMappingURL";
39constexpr char kCompilationHintsString[] = "compilationHints";
40constexpr char kBranchHintsString[] = "metadata.code.branch_hint";
41constexpr char kDebugInfoString[] = ".debug_info";
42constexpr char kExternalDebugInfoString[] = "external_debug_info";

44const char* ExternalKindName(ImportExportKindCode kind) {
switch (kind) {
  case kExternalFunction:
    return "function";
  case kExternalTable:
    return "table";
  case kExternalMemory:
    return "memory";
  case kExternalGlobal:
    return "global";
  case kExternalTag:
    return "tag";
}
return "unknown";
58}

60}  // namespace

62const char* SectionName(SectionCode code) {
switch (code) {
  case kUnknownSectionCode:
    return "Unknown";
  case kTypeSectionCode:
    return "Type";
  case kImportSectionCode:
    return "Import";
  case kFunctionSectionCode:
    return "Function";
  case kTableSectionCode:
    return "Table";
  case kMemorySectionCode:
    return "Memory";
  case kGlobalSectionCode:
    return "Global";
  case kExportSectionCode:
    return "Export";
  case kStartSectionCode:
    return "Start";
  case kCodeSectionCode:
    return "Code";
  case kElementSectionCode:
    return "Element";
  case kDataSectionCode:
    return "Data";
  case kTagSectionCode:
    return "Tag";
  case kDataCountSectionCode:
    return "DataCount";
  case kNameSectionCode:
    return kNameString;
  case kSourceMappingURLSectionCode:
    return kSourceMappingURLString;
  case kDebugInfoSectionCode:
    return kDebugInfoString;
  case kExternalDebugInfoSectionCode:
    return kExternalDebugInfoString;
  case kCompilationHintsSectionCode:
    return kCompilationHintsString;
  case kBranchHintsSectionCode:
    return kBranchHintsString;
  default:
    return "<unknown>";
}
107}

109namespace {

111bool validate_utf8(Decoder* decoder, WireBytesRef string) {
return unibrow::Utf8::ValidateEncoding(
    decoder->start() + decoder->GetBufferRelativeOffset(string.offset()),
    string.length());
115}

117// Reads a length-prefixed string, checking that it is within bounds. Returns
118// the offset of the string, and the length as an out parameter.
119WireBytesRef consume_string(Decoder* decoder, bool validate_utf8,
                          const char* name) {
uint32_t length = decoder->consume_u32v("string length");
uint32_t offset = decoder->pc_offset();
const byte* string_start = decoder->pc();
// Consume bytes before validation to guarantee that the string is not oob.
if (length > 0) {
  decoder->consume_bytes(length, name);
  if (decoder->ok() && validate_utf8 &&
      !unibrow::Utf8::ValidateEncoding(string_start, length)) {
    decoder->errorf(string_start, "%s: no valid UTF-8 string", name);
  }
}
return {offset, decoder->failed() ? 0 : length};
133}

135namespace {
136SectionCode IdentifyUnknownSectionInternal(Decoder* decoder) {
WireBytesRef string = consume_string(decoder, true, "section name");
if (decoder->failed()) {
  return kUnknownSectionCode;
}
const byte* section_name_start =
    decoder->start() + decoder->GetBufferRelativeOffset(string.offset());

TRACE("  +%d  section name        : \"%.*s\"\n",
      static_cast<int>(section_name_start - decoder->start()),
      string.length() < 20 ? string.length() : 20, section_name_start);

using SpecialSectionPair = std::pair<base::Vector<const char>, SectionCode>;
static constexpr SpecialSectionPair kSpecialSections[]{
    {base::StaticCharVector(kNameString), kNameSectionCode},
    {base::StaticCharVector(kSourceMappingURLString),
     kSourceMappingURLSectionCode},
    {base::StaticCharVector(kCompilationHintsString),
     kCompilationHintsSectionCode},
    {base::StaticCharVector(kBranchHintsString), kBranchHintsSectionCode},
    {base::StaticCharVector(kDebugInfoString), kDebugInfoSectionCode},
    {base::StaticCharVector(kExternalDebugInfoString),
     kExternalDebugInfoSectionCode}};

auto name_vec = base::Vector<const char>::cast(
    base::VectorOf(section_name_start, string.length()));
for (auto& special_section : kSpecialSections) {
  if (name_vec == special_section.first) return special_section.second;
}

return kUnknownSectionCode;
167}
168}  // namespace

170// An iterator over the sections in a wasm binary module.
171// Automatically skips all unknown sections.
172class WasmSectionIterator {
public:
explicit WasmSectionIterator(Decoder* decoder)
    : decoder_(decoder),
      section_code_(kUnknownSectionCode),
      section_start_(decoder->pc()),
      section_end_(decoder->pc()) {
  next();
}

bool more() const { return decoder_->ok() && decoder_->more(); }

SectionCode section_code() const { return section_code_; }

const byte* section_start() const { return section_start_; }

uint32_t section_length() const {
  return static_cast<uint32_t>(section_end_ - section_start_);
}

base::Vector<const uint8_t> payload() const {
  return {payload_start_, payload_length()};
}

const byte* payload_start() const { return payload_start_; }

uint32_t payload_length() const {
  return static_cast<uint32_t>(section_end_ - payload_start_);
}

const byte* section_end() const { return section_end_; }

// Advances to the next section, checking that decoding the current section
// stopped at {section_end_}.
void advance(bool move_to_section_end = false) {
  if (move_to_section_end && decoder_->pc() < section_end_) {
    decoder_->consume_bytes(
        static_cast<uint32_t>(section_end_ - decoder_->pc()));
  }
  if (decoder_->pc() != section_end_) {
    const char* msg = decoder_->pc() < section_end_ ? "shorter" : "longer";
    decoder_->errorf(decoder_->pc(),
                     "section was %s than expected size "
                     "(%u bytes expected, %zu decoded)",
                     msg, section_length(),
                     static_cast<size_t>(decoder_->pc() - section_start_));
  }
  next();
}

private:
Decoder* decoder_;
SectionCode section_code_;
const byte* section_start_;
const byte* payload_start_;
const byte* section_end_;

// Reads the section code/name at the current position and sets up
// the embedder fields.
void next() {
  if (!decoder_->more()) {
    section_code_ = kUnknownSectionCode;
    return;
  }
  section_start_ = decoder_->pc();
  uint8_t section_code = decoder_->consume_u8("section code");
  // Read and check the section size.
  uint32_t section_length = decoder_->consume_u32v("section length");

  payload_start_ = decoder_->pc();
  if (decoder_->checkAvailable(section_length)) {
    // Get the limit of the section within the module.
    section_end_ = payload_start_ + section_length;
  } else {
    // The section would extend beyond the end of the module.
    section_end_ = payload_start_;
  }

  if (section_code == kUnknownSectionCode) {
    // Check for the known "name", "sourceMappingURL", or "compilationHints"
    // section.
    // To identify the unknown section we set the end of the decoder bytes to
    // the end of the custom section, so that we do not read the section name
    // beyond the end of the section.
    const byte* module_end = decoder_->end();
    decoder_->set_end(section_end_);
    section_code = IdentifyUnknownSectionInternal(decoder_);
    if (decoder_->ok()) decoder_->set_end(module_end);
    // As a side effect, the above function will forward the decoder to after
    // the identifier string.
    payload_start_ = decoder_->pc();
  } else if (!IsValidSectionCode(section_code)) {
    decoder_->errorf(decoder_->pc(), "unknown section code #0x%02x",
                     section_code);
    section_code = kUnknownSectionCode;
  }
  section_code_ = decoder_->failed() ? kUnknownSectionCode
                                     : static_cast<SectionCode>(section_code);

  if (section_code_ == kUnknownSectionCode && section_end_ > decoder_->pc()) {
    // skip to the end of the unknown section.
    uint32_t remaining = static_cast<uint32_t>(section_end_ - decoder_->pc());
    decoder_->consume_bytes(remaining, "section payload");
  }
}
277};

279}  // namespace

281// The main logic for decoding the bytes of a module.
282class ModuleDecoderImpl : public Decoder {
public:
explicit ModuleDecoderImpl(const WasmFeatures& enabled, ModuleOrigin origin)
    : Decoder(nullptr, nullptr),
      enabled_features_(enabled),
      origin_(origin) {}

ModuleDecoderImpl(const WasmFeatures& enabled, const byte* module_start,
                  const byte* module_end, ModuleOrigin origin)
    : Decoder(module_start, module_end),
      enabled_features_(enabled),
      module_start_(module_start),
      module_end_(module_end),
      origin_(origin) {
  if (end_ < start_) {
    error(start_, "end is less than start");
    end_ = start_;
  }
}

void onFirstError() override {
  pc_ = end_;  // On error, terminate section decoding loop.
}

void DumpModule(const base::Vector<const byte> module_bytes) {
  std::string path;
  if (FLAG_dump_wasm_module_path) {
    path = FLAG_dump_wasm_module_path;
    if (path.size() &&
        !base::OS::isDirectorySeparator(path[path.size() - 1])) {
      path += base::OS::DirectorySeparator();
    }
  }
  // File are named `HASH.{ok,failed}.wasm`.
  size_t hash = base::hash_range(module_bytes.begin(), module_bytes.end());
  base::EmbeddedVector<char, 32> buf;
  SNPrintF(buf, "%016zx.%s.wasm", hash, ok() ? "ok" : "failed");
  path += buf.begin();
  size_t rv = 0;
  if (FILE* file = base::OS::FOpen(path.c_str(), "wb")) {
    rv = fwrite(module_bytes.begin(), module_bytes.length(), 1, file);
    base::Fclose(file);
  }
  if (rv != 1) {
    OFStream os(stderrstderr);
    os << "Error while dumping wasm file to " << path << std::endl;
  }
}

void StartDecoding(Counters* counters, AccountingAllocator* allocator) {
  CHECK_NULL(module_)do { if ((__builtin_expect(!!(!((module_) == nullptr)), 0))) {
 V8_Fatal("Check failed: %s.", "(module_) == nullptr"); } } while
 (false);
  SetCounters(counters);
  module_.reset(
      new WasmModule(std::make_unique<Zone>(allocator, "signatures")));
  module_->initial_pages = 0;
  module_->maximum_pages = 0;
  module_->mem_export = false;
  module_->origin = origin_;
}

void DecodeModuleHeader(base::Vector<const uint8_t> bytes, uint8_t offset) {
  if (failed()) return;
  Reset(bytes, offset);

  const byte* pos = pc_;
  uint32_t magic_word = consume_u32("wasm magic");
348#define BYTES(x) (x & 0xFF), (x >> 8) & 0xFF, (x >> 16) & 0xFF, (x >> 24) & 0xFF
  if (magic_word != kWasmMagic) {
    errorf(pos,
           "expected magic word %02x %02x %02x %02x, "
           "found %02x %02x %02x %02x",
           BYTES(kWasmMagic), BYTES(magic_word));
  }

  pos = pc_;
  {
    uint32_t magic_version = consume_u32("wasm version");
    if (magic_version != kWasmVersion) {
      errorf(pos,
             "expected version %02x %02x %02x %02x, "
             "found %02x %02x %02x %02x",
             BYTES(kWasmVersion), BYTES(magic_version));
    }
  }
366#undef BYTES
}

bool CheckSectionOrder(SectionCode section_code,
                       SectionCode prev_section_code,
                       SectionCode next_section_code) {
  if (next_ordered_section_ > next_section_code) {
    errorf(pc(), "The %s section must appear before the %s section",
           SectionName(section_code), SectionName(next_section_code));
    return false;
  }
  if (next_ordered_section_ <= prev_section_code) {
    next_ordered_section_ = prev_section_code + 1;
  }
  return true;
}

bool CheckUnorderedSection(SectionCode section_code) {
  if (has_seen_unordered_section(section_code)) {
    errorf(pc(), "Multiple %s sections not allowed",
           SectionName(section_code));
    return false;
  }
  set_seen_unordered_section(section_code);
  return true;
}

void DecodeSection(SectionCode section_code,
                   base::Vector<const uint8_t> bytes, uint32_t offset,
                   bool verify_functions = true) {
  if (failed()) return;
2
←
Taking false branch→
  Reset(bytes, offset);
  TRACE("Section: %s\n", SectionName(section_code));
3
←
Taking false branch→
4
←
Loop condition is false.  Exiting loop→
  TRACE("Decode Section %p - %p\n", bytes.begin(), bytes.end());
5
←
Taking false branch→

  // Check if the section is out-of-order.
  if (section_code < next_ordered_section_ &&
6
←
Loop condition is false.  Exiting loop→
7
←
Assuming 'section_code' is >= field 'next_ordered_section_'→
      section_code < kFirstUnorderedSection) {
    errorf(pc(), "unexpected section <%s>", SectionName(section_code));
    return;
  }

  switch (section_code) {
8
←
Control jumps to the 'default' case at line 457→
    case kUnknownSectionCode:
      break;
    case kDataCountSectionCode:
      if (!CheckUnorderedSection(section_code)) return;
      // If wasm-gc is enabled, we allow the data cound section anywhere in
      // the module.
      if (!enabled_features_.has_gc() &&
          !CheckSectionOrder(section_code, kElementSectionCode,
                             kCodeSectionCode)) {
        return;
      }
      break;
    case kTagSectionCode:
      if (!CheckUnorderedSection(section_code)) return;
      if (!CheckSectionOrder(section_code, kMemorySectionCode,
                             kGlobalSectionCode)) {
        return;
      }
      break;
    case kNameSectionCode:
      // TODO(titzer): report out of place name section as a warning.
      // Be lenient with placement of name section. All except first
      // occurrence are ignored.
    case kSourceMappingURLSectionCode:
      // sourceMappingURL is a custom section and currently can occur anywhere
      // in the module. In case of multiple sourceMappingURL sections, all
      // except the first occurrence are ignored.
    case kDebugInfoSectionCode:
      // .debug_info is a custom section containing core DWARF information
      // if produced by compiler. Its presence likely means that Wasm was
      // built in a debug mode.
    case kExternalDebugInfoSectionCode:
      // external_debug_info is a custom section containing a reference to an
      // external symbol file.
    case kCompilationHintsSectionCode:
      // TODO(frgossen): report out of place compilation hints section as a
      // warning.
      // Be lenient with placement of compilation hints section. All except
      // first occurrence after function section and before code section are
      // ignored.
      break;
    case kBranchHintsSectionCode:
      // TODO(yuri): report out of place branch hints section as a
      // warning.
      // Be lenient with placement of compilation hints section. All except
      // first occurrence after function section and before code section are
      // ignored.
      break;
    default:
      next_ordered_section_ = section_code + 1;
      break;
  }

  switch (section_code) {
9
←
 Execution continues on line 462→
10
←
Control jumps to 'case kTypeSectionCode:'  at line 465→
    case kUnknownSectionCode:
      break;
    case kTypeSectionCode:
      DecodeTypeSection();
11
←
Calling 'ModuleDecoderImpl::DecodeTypeSection'→
      break;
    case kImportSectionCode:
      DecodeImportSection();
      break;
    case kFunctionSectionCode:
      DecodeFunctionSection();
      break;
    case kTableSectionCode:
      DecodeTableSection();
      break;
    case kMemorySectionCode:
      DecodeMemorySection();
      break;
    case kGlobalSectionCode:
      DecodeGlobalSection();
      break;
    case kExportSectionCode:
      DecodeExportSection();
      break;
    case kStartSectionCode:
      DecodeStartSection();
      break;
    case kCodeSectionCode:
      DecodeCodeSection(verify_functions);
      break;
    case kElementSectionCode:
      DecodeElementSection();
      break;
    case kDataSectionCode:
      DecodeDataSection();
      break;
    case kNameSectionCode:
      DecodeNameSection();
      break;
    case kSourceMappingURLSectionCode:
      DecodeSourceMappingURLSection();
      break;
    case kDebugInfoSectionCode:
      // If there is an explicit source map, prefer it over DWARF info.
      if (module_->debug_symbols.type == WasmDebugSymbols::Type::None) {
        module_->debug_symbols = {WasmDebugSymbols::Type::EmbeddedDWARF, {}};
      }
      consume_bytes(static_cast<uint32_t>(end_ - start_), ".debug_info");
      break;
    case kExternalDebugInfoSectionCode:
      DecodeExternalDebugInfoSection();
      break;
    case kCompilationHintsSectionCode:
      if (enabled_features_.has_compilation_hints()) {
        DecodeCompilationHintsSection();
      } else {
        // Ignore this section when feature was disabled. It is an optional
        // custom section anyways.
        consume_bytes(static_cast<uint32_t>(end_ - start_), nullptr);
      }
      break;
    case kBranchHintsSectionCode:
      if (enabled_features_.has_branch_hinting()) {
        DecodeBranchHintsSection();
      } else {
        // Ignore this section when feature was disabled. It is an optional
        // custom section anyways.
        consume_bytes(static_cast<uint32_t>(end_ - start_), nullptr);
      }
      break;
    case kDataCountSectionCode:
      DecodeDataCountSection();
      break;
    case kTagSectionCode:
      if (enabled_features_.has_eh()) {
        DecodeTagSection();
      } else {
        errorf(pc(),
               "unexpected section <%s> (enable with --experimental-wasm-eh)",
               SectionName(section_code));
      }
      break;
    default:
      errorf(pc(), "unexpected section <%s>", SectionName(section_code));
      return;
  }

  if (pc() != bytes.end()) {
    const char* msg = pc() < bytes.end() ? "shorter" : "longer";
    errorf(pc(),
           "section was %s than expected size "
           "(%zu bytes expected, %zu decoded)",
           msg, bytes.size(), static_cast<size_t>(pc() - bytes.begin()));
  }
}

TypeDefinition consume_base_type_definition() {
  DCHECK(enabled_features_.has_gc())((void) 0);
  uint8_t kind = consume_u8("type kind");
  switch (kind) {
    case kWasmFunctionTypeCode: {
      const FunctionSig* sig = consume_sig(module_->signature_zone.get());
      return {sig, kNoSuperType};
    }
    case kWasmStructTypeCode: {
      const StructType* type = consume_struct(module_->signature_zone.get());
      return {type, kNoSuperType};
    }
    case kWasmArrayTypeCode: {
      const ArrayType* type = consume_array(module_->signature_zone.get());
      return {type, kNoSuperType};
    }
    case kWasmFunctionNominalCode:
    case kWasmArrayNominalCode:
    case kWasmStructNominalCode:
      errorf(pc() - 1,
             "mixing nominal and isorecursive types is not allowed");
      return {};
    default:
      errorf(pc() - 1, "unknown type form: %d", kind);
      return {};
  }
}

bool check_supertype(uint32_t supertype) {
  if (V8_UNLIKELY(supertype >= module_->types.size())(__builtin_expect(!!(supertype >= module_->types.size()
), 0))) {
    errorf(pc(), "type %zu: forward-declared supertype %d",
           module_->types.size(), supertype);
    return false;
  }
  return true;
}

TypeDefinition consume_nominal_type_definition() {
  DCHECK(enabled_features_.has_gc())((void) 0);
  size_t num_types = module_->types.size();
  uint8_t kind = consume_u8("type kind");
  switch (kind) {
    case kWasmFunctionNominalCode: {
      const FunctionSig* sig = consume_sig(module_->signature_zone.get());
      uint32_t super_index = kNoSuperType;
      HeapType super_type = consume_super_type();
      if (super_type.is_index()) {
        super_index = super_type.representation();
      } else if (V8_UNLIKELY(super_type != HeapType::kFunc)(__builtin_expect(!!(super_type != HeapType::kFunc), 0))) {
        errorf(pc() - 1, "type %zu: invalid supertype %d", num_types,
               super_type.code());
        return {};
      }
      return {sig, super_index};
    }
    case kWasmStructNominalCode: {
      const StructType* type = consume_struct(module_->signature_zone.get());
      uint32_t super_index = kNoSuperType;
      HeapType super_type = consume_super_type();
      if (super_type.is_index()) {
        super_index = super_type.representation();
      } else if (V8_UNLIKELY(super_type != HeapType::kData)(__builtin_expect(!!(super_type != HeapType::kData), 0))) {
        errorf(pc() - 1, "type %zu: invalid supertype %d", num_types,
               super_type.code());
        return {};
      }
      return {type, super_index};
    }
    case kWasmArrayNominalCode: {
      const ArrayType* type = consume_array(module_->signature_zone.get());
      uint32_t super_index = kNoSuperType;
      HeapType super_type = consume_super_type();
      if (super_type.is_index()) {
        super_index = super_type.representation();
      } else if (V8_UNLIKELY(super_type != HeapType::kData)(__builtin_expect(!!(super_type != HeapType::kData), 0))) {
        errorf(pc() - 1, "type %zu: invalid supertype %d", num_types,
               super_type.code());
        return {};
      }
      return {type, super_index};
    }
    case kWasmFunctionTypeCode:
    case kWasmArrayTypeCode:
    case kWasmStructTypeCode:
    case kWasmSubtypeCode:
    case kWasmRecursiveTypeGroupCode:
      errorf(pc() - 1,
             "mixing nominal and isorecursive types is not allowed");
      return {};
    default:
      errorf(pc() - 1, "unknown type form: %d", kind);
      return {};
  }
}

TypeDefinition consume_subtype_definition() {
  DCHECK(enabled_features_.has_gc())((void) 0);
  uint8_t kind = read_u8<Decoder::kFullValidation>(pc(), "type kind");
  if (kind == kWasmSubtypeCode) {
    consume_bytes(1, "subtype definition");
    constexpr uint32_t kMaximumSupertypes = 1;
    uint32_t supertype_count =
        consume_count("supertype count", kMaximumSupertypes);
    uint32_t supertype =
        supertype_count == 1 ? consume_u32v("supertype") : kNoSuperType;
    if (!check_supertype(supertype)) return {};
    TypeDefinition type = consume_base_type_definition();
    type.supertype = supertype;
    return type;
  } else {
    return consume_base_type_definition();
  }
}

void DecodeTypeSection() {
  TypeCanonicalizer* type_canon = GetTypeCanonicalizer();
  uint32_t types_count = consume_count("types count", kV8MaxWasmTypes);

  // Non wasm-gc type section decoding.
  if (!enabled_features_.has_gc()) {
12
←
Taking false branch→
    module_->types.reserve(types_count);
    for (uint32_t i = 0; i < types_count; ++i) {
      TRACE("DecodeSignature[%d] module+%d\n", i,
            static_cast<int>(pc_ - start_));
      expect_u8("signature definition", kWasmFunctionTypeCode);
      const FunctionSig* sig = consume_sig(module_->signature_zone.get());
      if (!ok()) break;
      module_->add_signature(sig, kNoSuperType);
      if (FLAG_wasm_type_canonicalization) {
        type_canon->AddRecursiveGroup(module_.get(), 1);
      }
    }
    return;
  }

  if (types_count > 0) {
13
←
Assuming 'types_count' is > 0→
14
←
Taking true branch→
    uint8_t first_type_opcode = this->read_u8<Decoder::kFullValidation>(pc());
    if (first_type_opcode == kWasmFunctionNominalCode ||
15
←
Assuming 'first_type_opcode' is equal to 'kWasmFunctionNominalCode'→
        first_type_opcode == kWasmStructNominalCode ||
        first_type_opcode == kWasmArrayNominalCode) {
      // wasm-gc nominal type section decoding.
      // In a nominal module, all types belong in the same recursive group. We
      // use the type vector's capacity to mark the end of the current
      // recursive group.
      module_->types.reserve(types_count);
      for (uint32_t i = 0; ok() && i16.1
'i' is < 'types_count'
1
'i' is < 'types_count'
 < types_count; ++i) {
16
←
Assuming the condition is true→
17
←
Loop condition is true.  Entering loop body→
        TRACE("DecodeType[%d] module+%d\n", i,
18
←
Taking false branch→
19
←
Loop condition is false.  Exiting loop→
              static_cast<int>(pc_ - start_));
        TypeDefinition type = consume_nominal_type_definition();
        if (ok()) module_->add_type(type);
20
←
Assuming the condition is true→
21
←
Taking true branch→
22
←
Null pointer value stored to 'type..function_sig'→
23
←
Calling 'WasmModule::add_type'→
      }
      if (ok() && FLAG_wasm_type_canonicalization) {
        type_canon->AddRecursiveGroup(module_.get(), types_count);
      }
    } else {
      // wasm-gc isorecursive type section decoding.
      for (uint32_t i = 0; ok() && i < types_count; ++i) {
        TRACE("DecodeType[%d] module+%d\n", i,
              static_cast<int>(pc_ - start_));
        uint8_t kind = read_u8<Decoder::kFullValidation>(pc(), "type kind");
        if (kind == kWasmRecursiveTypeGroupCode) {
          consume_bytes(1, "rec. group definition");
          uint32_t group_size =
              consume_count("recursive group size", kV8MaxWasmTypes);
          if (module_->types.size() + group_size > kV8MaxWasmTypes) {
            errorf(pc(), "Type definition count exeeds maximum %zu",
                   kV8MaxWasmTypes);
            return;
          }
          // Reserve space for the current recursive group, so we are
          // allowed to reference its elements.
          module_->types.reserve(module_->types.size() + group_size);
          for (uint32_t i = 0; i < group_size; i++) {
            TypeDefinition type = consume_subtype_definition();
            if (ok()) module_->add_type(type);
          }
          if (ok() && FLAG_wasm_type_canonicalization) {
            type_canon->AddRecursiveGroup(module_.get(), group_size);
          }
        } else {
          TypeDefinition type = consume_subtype_definition();
          if (ok()) {
            module_->add_type(type);
            if (FLAG_wasm_type_canonicalization) {
              type_canon->AddRecursiveGroup(module_.get(), 1);
            }
          }
        }
      }
    }
  }

  // Check validity of explicitly defined supertypes.
  const WasmModule* module = module_.get();
  for (uint32_t i = 0; ok() && i < types_count; ++i) {
    uint32_t explicit_super = module_->supertype(i);
    if (explicit_super == kNoSuperType) continue;
    DCHECK_LT(explicit_super, types_count)((void) 0);  // {consume_super_type} checks.
    int depth = GetSubtypingDepth(module, i);
    if (depth > static_cast<int>(kV8MaxRttSubtypingDepth)) {
      errorf("type %d: subtyping depth is greater than allowed", i);
      continue;
    }
    // TODO(7748): Replace this with a DCHECK once we reject inheritance
    // cycles for nominal modules.
    if (depth == -1) {
      errorf("type %d: cyclic inheritance", i);
      continue;
    }
    if (!ValidSubtypeDefinition(i, explicit_super, module, module)) {
      errorf("type %d has invalid explicit supertype %d", i, explicit_super);
      continue;
    }
  }
  module_->signature_map.Freeze();
}

void DecodeImportSection() {
  uint32_t import_table_count =
      consume_count("imports count", kV8MaxWasmImports);
  module_->import_table.reserve(import_table_count);
  for (uint32_t i = 0; ok() && i < import_table_count; ++i) {
    TRACE("DecodeImportTable[%d] module+%d\n", i,
          static_cast<int>(pc_ - start_));

    module_->import_table.push_back({
        {0, 0},             // module_name
        {0, 0},             // field_name
        kExternalFunction,  // kind
        0                   // index
    });
    WasmImport* import = &module_->import_table.back();
    const byte* pos = pc_;
    import->module_name = consume_string(this, true, "module name");
    import->field_name = consume_string(this, true, "field name");
    import->kind =
        static_cast<ImportExportKindCode>(consume_u8("import kind"));
    switch (import->kind) {
      case kExternalFunction: {
        // ===== Imported function ===========================================
        import->index = static_cast<uint32_t>(module_->functions.size());
        module_->num_imported_functions++;
        module_->functions.push_back({nullptr,        // sig
                                      import->index,  // func_index
                                      0,              // sig_index
                                      {0, 0},         // code
                                      0,              // feedback slots
                                      true,           // imported
                                      false,          // exported
                                      false});        // declared
        WasmFunction* function = &module_->functions.back();
        function->sig_index =
            consume_sig_index(module_.get(), &function->sig);
        break;
      }
      case kExternalTable: {
        // ===== Imported table ==============================================
        import->index = static_cast<uint32_t>(module_->tables.size());
        module_->num_imported_tables++;
        module_->tables.emplace_back();
        WasmTable* table = &module_->tables.back();
        table->imported = true;
        const byte* type_position = pc();
        ValueType type = consume_reference_type();
        if (!WasmTable::IsValidTableType(type, module_.get())) {
          errorf(type_position, "Invalid table type %s", type.name().c_str());
          break;
        }
        table->type = type;
        uint8_t flags = validate_table_flags("element count");
        consume_resizable_limits(
            "element count", "elements", std::numeric_limits<uint32_t>::max(),
            &table->initial_size, &table->has_maximum_size,
            std::numeric_limits<uint32_t>::max(), &table->maximum_size,
            flags);
        break;
      }
      case kExternalMemory: {
        // ===== Imported memory =============================================
        if (!AddMemory(module_.get())) break;
        uint8_t flags = validate_memory_flags(&module_->has_shared_memory,
                                              &module_->is_memory64);
        consume_resizable_limits(
            "memory", "pages", kSpecMaxMemoryPages, &module_->initial_pages,
            &module_->has_maximum_pages, kSpecMaxMemoryPages,
            &module_->maximum_pages, flags);
        break;
      }
      case kExternalGlobal: {
        // ===== Imported global =============================================
        import->index = static_cast<uint32_t>(module_->globals.size());
        module_->globals.push_back({kWasmVoid, false, {}, {0}, true, false});
        WasmGlobal* global = &module_->globals.back();
        global->type = consume_value_type();
        global->mutability = consume_mutability();
        if (global->mutability) {
          module_->num_imported_mutable_globals++;
        }
        break;
      }
      case kExternalTag: {
        // ===== Imported tag ================================================
        if (!enabled_features_.has_eh()) {
          errorf(pos, "unknown import kind 0x%02x", import->kind);
          break;
        }
        import->index = static_cast<uint32_t>(module_->tags.size());
        const WasmTagSig* tag_sig = nullptr;
        consume_exception_attribute();  // Attribute ignored for now.
        consume_tag_sig_index(module_.get(), &tag_sig);
        module_->tags.emplace_back(tag_sig);
        break;
      }
      default:
        errorf(pos, "unknown import kind 0x%02x", import->kind);
        break;
    }
  }
}

void DecodeFunctionSection() {
  uint32_t functions_count =
      consume_count("functions count", kV8MaxWasmFunctions);
  auto counter =
      SELECT_WASM_COUNTER(GetCounters(), origin_, wasm_functions_per, module)((origin_) == kWasmOrigin ? (GetCounters())->wasm_functions_per_wasm_module
() : (GetCounters())->wasm_functions_per_asm_module());
  counter->AddSample(static_cast<int>(functions_count));
  DCHECK_EQ(module_->functions.size(), module_->num_imported_functions)((void) 0);
  uint32_t total_function_count =
      module_->num_imported_functions + functions_count;
  module_->functions.reserve(total_function_count);
  module_->num_declared_functions = functions_count;
  for (uint32_t i = 0; i < functions_count; ++i) {
    uint32_t func_index = static_cast<uint32_t>(module_->functions.size());
    module_->functions.push_back({nullptr,     // sig
                                  func_index,  // func_index
                                  0,           // sig_index
                                  {0, 0},      // code
                                  0,           // feedback slots
                                  false,       // imported
                                  false,       // exported
                                  false});     // declared
    WasmFunction* function = &module_->functions.back();
    function->sig_index = consume_sig_index(module_.get(), &function->sig);
    if (!ok()) return;
  }
  DCHECK_EQ(module_->functions.size(), total_function_count)((void) 0);
}

void DecodeTableSection() {
  uint32_t table_count = consume_count("table count", kV8MaxWasmTables);

  for (uint32_t i = 0; ok() && i < table_count; i++) {
    module_->tables.emplace_back();
    WasmTable* table = &module_->tables.back();
    const byte* type_position = pc();
    ValueType table_type = consume_reference_type();
    if (!WasmTable::IsValidTableType(table_type, module_.get())) {
      error(type_position,
            "Currently, only externref and function references are allowed "
            "as table types");
      continue;
    }
    table->type = table_type;
    uint8_t flags = validate_table_flags("table elements");
    consume_resizable_limits(
        "table elements", "elements", std::numeric_limits<uint32_t>::max(),
        &table->initial_size, &table->has_maximum_size,
        std::numeric_limits<uint32_t>::max(), &table->maximum_size, flags);
    if (!table_type.is_defaultable()) {
      table->initial_value = consume_init_expr(module_.get(), table_type);
    }
  }
}

void DecodeMemorySection() {
  uint32_t memory_count = consume_count("memory count", kV8MaxWasmMemories);

  for (uint32_t i = 0; ok() && i < memory_count; i++) {
    if (!AddMemory(module_.get())) break;
    uint8_t flags = validate_memory_flags(&module_->has_shared_memory,
                                          &module_->is_memory64);
    consume_resizable_limits("memory", "pages", kSpecMaxMemoryPages,
                             &module_->initial_pages,
                             &module_->has_maximum_pages, kSpecMaxMemoryPages,
                             &module_->maximum_pages, flags);
  }
}

void DecodeGlobalSection() {
  uint32_t globals_count = consume_count("globals count", kV8MaxWasmGlobals);
  uint32_t imported_globals = static_cast<uint32_t>(module_->globals.size());
  // It is important to not resize the globals vector from the beginning,
  // because we use its current size when decoding the initializer.
  module_->globals.reserve(imported_globals + globals_count);
  for (uint32_t i = 0; ok() && i < globals_count; ++i) {
    TRACE("DecodeGlobal[%d] module+%d\n", i, static_cast<int>(pc_ - start_));
    ValueType type = consume_value_type();
    bool mutability = consume_mutability();
    if (failed()) break;
    ConstantExpression init = consume_init_expr(module_.get(), type);
    module_->globals.push_back({type, mutability, init, {0}, false, false});
  }
  if (ok()) CalculateGlobalOffsets(module_.get());
}

void DecodeExportSection() {
  uint32_t export_table_count =
      consume_count("exports count", kV8MaxWasmExports);
  module_->export_table.reserve(export_table_count);
  for (uint32_t i = 0; ok() && i < export_table_count; ++i) {
    TRACE("DecodeExportTable[%d] module+%d\n", i,
          static_cast<int>(pc_ - start_));

    module_->export_table.push_back({
        {0, 0},             // name
        kExternalFunction,  // kind
        0                   // index
    });
    WasmExport* exp = &module_->export_table.back();

    exp->name = consume_string(this, true, "field name");

    const byte* pos = pc();
    exp->kind = static_cast<ImportExportKindCode>(consume_u8("export kind"));
    switch (exp->kind) {
      case kExternalFunction: {
        WasmFunction* func = nullptr;
        exp->index =
            consume_func_index(module_.get(), &func, "export function index");

        if (failed()) break;
        DCHECK_NOT_NULL(func)((void) 0);

        module_->num_exported_functions++;
        func->exported = true;
        // Exported functions are considered "declared".
        func->declared = true;
        break;
      }
      case kExternalTable: {
        WasmTable* table = nullptr;
        exp->index = consume_table_index(module_.get(), &table);
        if (table) table->exported = true;
        break;
      }
      case kExternalMemory: {
        uint32_t index = consume_u32v("memory index");
        // TODO(titzer): This should become more regular
        // once we support multiple memories.
        if (!module_->has_memory || index != 0) {
          error("invalid memory index != 0");
        }
        module_->mem_export = true;
        break;
      }
      case kExternalGlobal: {
        WasmGlobal* global = nullptr;
        exp->index = consume_global_index(module_.get(), &global);
        if (global) {
          global->exported = true;
        }
        break;
      }
      case kExternalTag: {
        if (!enabled_features_.has_eh()) {
          errorf(pos, "invalid export kind 0x%02x", exp->kind);
          break;
        }
        WasmTag* tag = nullptr;
        exp->index = consume_tag_index(module_.get(), &tag);
        break;
      }
      default:
        errorf(pos, "invalid export kind 0x%02x", exp->kind);
        break;
    }
  }
  // Check for duplicate exports (except for asm.js).
  if (ok() && origin_ == kWasmOrigin && module_->export_table.size() > 1) {
    std::vector<WasmExport> sorted_exports(module_->export_table);

    auto cmp_less = [this](const WasmExport& a, const WasmExport& b) {
      // Return true if a < b.
      if (a.name.length() != b.name.length()) {
        return a.name.length() < b.name.length();
      }
      const byte* left = start() + GetBufferRelativeOffset(a.name.offset());
      const byte* right = start() + GetBufferRelativeOffset(b.name.offset());
      return memcmp(left, right, a.name.length()) < 0;
    };
    std::stable_sort(sorted_exports.begin(), sorted_exports.end(), cmp_less);

    auto it = sorted_exports.begin();
    WasmExport* last = &*it++;
    for (auto end = sorted_exports.end(); it != end; last = &*it++) {
      DCHECK(!cmp_less(*it, *last))((void) 0);  // Vector must be sorted.
      if (!cmp_less(*last, *it)) {
        const byte* pc = start() + GetBufferRelativeOffset(it->name.offset());
        TruncatedUserString<> name(pc, it->name.length());
        errorf(pc, "Duplicate export name '%.*s' for %s %d and %s %d",
               name.length(), name.start(), ExternalKindName(last->kind),
               last->index, ExternalKindName(it->kind), it->index);
        break;
      }
    }
  }
}

void DecodeStartSection() {
  WasmFunction* func;
  const byte* pos = pc_;
  module_->start_function_index =
      consume_func_index(module_.get(), &func, "start function index");
  if (func &&
      (func->sig->parameter_count() > 0 || func->sig->return_count() > 0)) {
    error(pos, "invalid start function: non-zero parameter or return count");
  }
}

void DecodeElementSection() {
  uint32_t element_count =
      consume_count("element count", FLAG_wasm_max_table_size);

  for (uint32_t i = 0; i < element_count; ++i) {
    WasmElemSegment segment = consume_element_segment_header();
    if (failed()) return;
    DCHECK_NE(segment.type, kWasmBottom)((void) 0);

    uint32_t num_elem =
        consume_count("number of elements", max_table_init_entries());

    for (uint32_t j = 0; j < num_elem; j++) {
      ConstantExpression entry =
          segment.element_type == WasmElemSegment::kExpressionElements
              ? consume_init_expr(module_.get(), segment.type)
              : ConstantExpression::RefFunc(
                    consume_element_func_index(segment.type));
      if (failed()) return;
      segment.entries.push_back(entry);
    }
    module_->elem_segments.push_back(std::move(segment));
  }
}

void DecodeCodeSection(bool verify_functions) {
  StartCodeSection();
  uint32_t code_section_start = pc_offset();
  uint32_t functions_count = consume_u32v("functions count");
  CheckFunctionsCount(functions_count, code_section_start);
  for (uint32_t i = 0; ok() && i < functions_count; ++i) {
    const byte* pos = pc();
    uint32_t size = consume_u32v("body size");
    if (size > kV8MaxWasmFunctionSize) {
      errorf(pos, "size %u > maximum function size %zu", size,
             kV8MaxWasmFunctionSize);
      return;
    }
    uint32_t offset = pc_offset();
    consume_bytes(size, "function body");
    if (failed()) break;
    DecodeFunctionBody(i, size, offset, verify_functions);
  }
  DCHECK_GE(pc_offset(), code_section_start)((void) 0);
  set_code_section(code_section_start, pc_offset() - code_section_start);
}

void StartCodeSection() {
  if (ok()) {
    // Make sure global offset were calculated before they get accessed during
    // function compilation.
    CalculateGlobalOffsets(module_.get());
  }
}

bool CheckFunctionsCount(uint32_t functions_count, uint32_t error_offset) {
  if (functions_count != module_->num_declared_functions) {
    errorf(error_offset, "function body count %u mismatch (%u expected)",
           functions_count, module_->num_declared_functions);
    return false;
  }
  return true;
}

void DecodeFunctionBody(uint32_t index, uint32_t length, uint32_t offset,
                        bool verify_functions) {
  WasmFunction* function =
      &module_->functions[index + module_->num_imported_functions];
  function->code = {offset, length};
  if (verify_functions) {
    ModuleWireBytes bytes(module_start_, module_end_);
    VerifyFunctionBody(module_->signature_zone->allocator(),
                       index + module_->num_imported_functions, bytes,
                       module_.get(), function);
  }
}

bool CheckDataSegmentsCount(uint32_t data_segments_count) {
  if (has_seen_unordered_section(kDataCountSectionCode) &&
      data_segments_count != module_->num_declared_data_segments) {
    errorf(pc(), "data segments count %u mismatch (%u expected)",
           data_segments_count, module_->num_declared_data_segments);
    return false;
  }
  return true;
}

void DecodeDataSection() {
  uint32_t data_segments_count =
      consume_count("data segments count", kV8MaxWasmDataSegments);
  if (!CheckDataSegmentsCount(data_segments_count)) return;

  module_->data_segments.reserve(data_segments_count);
  for (uint32_t i = 0; ok() && i < data_segments_count; ++i) {
    const byte* pos = pc();
    TRACE("DecodeDataSegment[%d] module+%d\n", i,
          static_cast<int>(pc_ - start_));

    bool is_active;
    uint32_t memory_index;
    ConstantExpression dest_addr;
    consume_data_segment_header(&is_active, &memory_index, &dest_addr);
    if (failed()) break;

    if (is_active) {
      if (!module_->has_memory) {
        error("cannot load data without memory");
        break;
      }
      if (memory_index != 0) {
        errorf(pos, "illegal memory index %u != 0", memory_index);
        break;
      }
    }

    uint32_t source_length = consume_u32v("source size");
    uint32_t source_offset = pc_offset();

    if (is_active) {
      module_->data_segments.emplace_back(std::move(dest_addr));
    } else {
      module_->data_segments.emplace_back();
    }

    WasmDataSegment* segment = &module_->data_segments.back();

    consume_bytes(source_length, "segment data");
    if (failed()) break;

    segment->source = {source_offset, source_length};
  }
}

void DecodeNameSection() {
  // TODO(titzer): find a way to report name errors as warnings.
  // Ignore all but the first occurrence of name section.
  if (!has_seen_unordered_section(kNameSectionCode)) {
    set_seen_unordered_section(kNameSectionCode);
    // Use an inner decoder so that errors don't fail the outer decoder.
    Decoder inner(start_, pc_, end_, buffer_offset_);
    // Decode all name subsections.
    // Be lenient with their order.
    while (inner.ok() && inner.more()) {
      uint8_t name_type = inner.consume_u8("name type");
      if (name_type & 0x80) inner.error("name type if not varuint7");

      uint32_t name_payload_len = inner.consume_u32v("name payload length");
      if (!inner.checkAvailable(name_payload_len)) break;

      // Decode module name, ignore the rest.
      // Function and local names will be decoded when needed.
      if (name_type == NameSectionKindCode::kModuleCode) {
        WireBytesRef name = consume_string(&inner, false, "module name");
        if (inner.ok() && validate_utf8(&inner, name)) {
          module_->name = name;
        }
      } else {
        inner.consume_bytes(name_payload_len, "name subsection payload");
      }
    }
  }
  // Skip the whole names section in the outer decoder.
  consume_bytes(static_cast<uint32_t>(end_ - start_), nullptr);
}

void DecodeSourceMappingURLSection() {
  Decoder inner(start_, pc_, end_, buffer_offset_);
  WireBytesRef url = wasm::consume_string(&inner, true, "module name");
  if (inner.ok() &&
      module_->debug_symbols.type != WasmDebugSymbols::Type::SourceMap) {
    module_->debug_symbols = {WasmDebugSymbols::Type::SourceMap, url};
  }
  set_seen_unordered_section(kSourceMappingURLSectionCode);
  consume_bytes(static_cast<uint32_t>(end_ - start_), nullptr);
}

void DecodeExternalDebugInfoSection() {
  Decoder inner(start_, pc_, end_, buffer_offset_);
  WireBytesRef url =
      wasm::consume_string(&inner, true, "external symbol file");
  // If there is an explicit source map, prefer it over DWARF info.
  if (inner.ok() &&
      module_->debug_symbols.type != WasmDebugSymbols::Type::SourceMap) {
    module_->debug_symbols = {WasmDebugSymbols::Type::ExternalDWARF, url};
    set_seen_unordered_section(kExternalDebugInfoSectionCode);
  }
  consume_bytes(static_cast<uint32_t>(end_ - start_), nullptr);
}

void DecodeCompilationHintsSection() {
  TRACE("DecodeCompilationHints module+%d\n", static_cast<int>(pc_ - start_));

  // TODO(frgossen): Find a way to report compilation hint errors as warnings.
  // All except first occurrence after function section and before code
  // section are ignored.
  const bool before_function_section =
      next_ordered_section_ <= kFunctionSectionCode;
  const bool after_code_section = next_ordered_section_ > kCodeSectionCode;
  if (before_function_section || after_code_section ||
      has_seen_unordered_section(kCompilationHintsSectionCode)) {
    return;
  }
  set_seen_unordered_section(kCompilationHintsSectionCode);

  // TODO(frgossen) Propagate errors to outer decoder in experimental phase.
  // We should use an inner decoder later and propagate its errors as
  // warnings.
  Decoder& decoder = *this;
  // Decoder decoder(start_, pc_, end_, buffer_offset_);

  // Ensure exactly one compilation hint per function.
  uint32_t hint_count = decoder.consume_u32v("compilation hint count");
  if (hint_count != module_->num_declared_functions) {
    decoder.errorf(decoder.pc(), "Expected %u compilation hints (%u found)",
                   module_->num_declared_functions, hint_count);
  }

  // Decode sequence of compilation hints.
  if (decoder.ok()) {
    module_->compilation_hints.reserve(hint_count);
  }
  for (uint32_t i = 0; decoder.ok() && i < hint_count; i++) {
    TRACE("DecodeCompilationHints[%d] module+%d\n", i,
          static_cast<int>(pc_ - start_));

    // Compilation hints are encoded in one byte each.
    // +-------+----------+---------------+----------+
    // | 2 bit | 2 bit    | 2 bit         | 2 bit    |
    // | ...   | Top tier | Baseline tier | Strategy |
    // +-------+----------+---------------+----------+
    uint8_t hint_byte = decoder.consume_u8("compilation hint");
    if (!decoder.ok()) break;

    // Validate the hint_byte.
    // For the compilation strategy, all 2-bit values are valid. For the tier,
    // only 0x0, 0x1, and 0x2 are allowed.
    static_assert(
        static_cast<int>(WasmCompilationHintTier::kDefault) == 0 &&
            static_cast<int>(WasmCompilationHintTier::kBaseline) == 1 &&
            static_cast<int>(WasmCompilationHintTier::kOptimized) == 2,
        "The check below assumes that 0x03 is the only invalid 2-bit number "
        "for a compilation tier");
    if (((hint_byte >> 2) & 0x03) == 0x03 ||
        ((hint_byte >> 4) & 0x03) == 0x03) {
      decoder.errorf(decoder.pc(),
                     "Invalid compilation hint %#04x (invalid tier 0x03)",
                     hint_byte);
      break;
    }

    // Decode compilation hint.
    WasmCompilationHint hint;
    hint.strategy =
        static_cast<WasmCompilationHintStrategy>(hint_byte & 0x03);
    hint.baseline_tier =
        static_cast<WasmCompilationHintTier>((hint_byte >> 2) & 0x03);
    hint.top_tier =
        static_cast<WasmCompilationHintTier>((hint_byte >> 4) & 0x03);

    // Ensure that the top tier never downgrades a compilation result. If
    // baseline and top tier are the same compilation will be invoked only
    // once.
    if (hint.top_tier < hint.baseline_tier &&
        hint.top_tier != WasmCompilationHintTier::kDefault) {
      decoder.errorf(decoder.pc(),
                     "Invalid compilation hint %#04x (forbidden downgrade)",
                     hint_byte);
    }

    // Happily accept compilation hint.
    if (decoder.ok()) {
      module_->compilation_hints.push_back(std::move(hint));
    }
  }

  // If section was invalid reset compilation hints.
  if (decoder.failed()) {
    module_->compilation_hints.clear();
  }

  // @TODO(frgossen) Skip the whole compilation hints section in the outer
  // decoder if inner decoder was used.
  // consume_bytes(static_cast<uint32_t>(end_ - start_), nullptr);
}

void DecodeBranchHintsSection() {
  TRACE("DecodeBranchHints module+%d\n", static_cast<int>(pc_ - start_));
  if (!has_seen_unordered_section(kBranchHintsSectionCode)) {
    set_seen_unordered_section(kBranchHintsSectionCode);
    // Use an inner decoder so that errors don't fail the outer decoder.
    Decoder inner(start_, pc_, end_, buffer_offset_);
    BranchHintInfo branch_hints;

    uint32_t func_count = inner.consume_u32v("number of functions");
    // Keep track of the previous function index to validate the ordering
    int64_t last_func_idx = -1;
    for (uint32_t i = 0; i < func_count; i++) {
      uint32_t func_idx = inner.consume_u32v("function index");
      if (int64_t(func_idx) <= last_func_idx) {
        inner.errorf("Invalid function index: %d", func_idx);
        break;
      }
      last_func_idx = func_idx;
      uint32_t num_hints = inner.consume_u32v("number of hints");
      BranchHintMap func_branch_hints;
      TRACE("DecodeBranchHints[%d] module+%d\n", func_idx,
            static_cast<int>(inner.pc() - inner.start()));
      // Keep track of the previous branch offset to validate the ordering
      int64_t last_br_off = -1;
      for (uint32_t j = 0; j < num_hints; ++j) {
        uint32_t br_off = inner.consume_u32v("branch instruction offset");
        if (int64_t(br_off) <= last_br_off) {
          inner.errorf("Invalid branch offset: %d", br_off);
          break;
        }
        last_br_off = br_off;
        uint32_t data_size = inner.consume_u32v("data size");
        if (data_size != 1) {
          inner.errorf("Invalid data size: %#x. Expected 1.", data_size);
          break;
        }
        uint32_t br_dir = inner.consume_u8("branch direction");
        TRACE("DecodeBranchHints[%d][%d] module+%d\n", func_idx, br_off,
              static_cast<int>(inner.pc() - inner.start()));
        WasmBranchHint hint;
        switch (br_dir) {
          case 0:
            hint = WasmBranchHint::kUnlikely;
            break;
          case 1:
            hint = WasmBranchHint::kLikely;
            break;
          default:
            hint = WasmBranchHint::kNoHint;
            inner.errorf(inner.pc(), "Invalid branch hint %#x", br_dir);
            break;
        }
        if (!inner.ok()) {
          break;
        }
        func_branch_hints.insert(br_off, hint);
      }
      if (!inner.ok()) {
        break;
      }
      branch_hints.emplace(func_idx, std::move(func_branch_hints));
    }
    // Extra unexpected bytes are an error.
    if (inner.more()) {
      inner.errorf("Unexpected extra bytes: %d\n",
                   static_cast<int>(inner.pc() - inner.start()));
    }
    // If everything went well, accept the hints for the module.
    if (inner.ok()) {
      module_->branch_hints = std::move(branch_hints);
    }
  }
  // Skip the whole branch hints section in the outer decoder.
  consume_bytes(static_cast<uint32_t>(end_ - start_), nullptr);
}

void DecodeDataCountSection() {
  module_->num_declared_data_segments =
      consume_count("data segments count", kV8MaxWasmDataSegments);
}

void DecodeTagSection() {
  uint32_t tag_count = consume_count("tag count", kV8MaxWasmTags);
  for (uint32_t i = 0; ok() && i < tag_count; ++i) {
    TRACE("DecodeTag[%d] module+%d\n", i, static_cast<int>(pc_ - start_));
    const WasmTagSig* tag_sig = nullptr;
    consume_exception_attribute();  // Attribute ignored for now.
    consume_tag_sig_index(module_.get(), &tag_sig);
    module_->tags.emplace_back(tag_sig);
  }
}

bool CheckMismatchedCounts() {
  // The declared vs. defined function count is normally checked when
  // decoding the code section, but we have to check it here too in case the
  // code section is absent.
  if (module_->num_declared_functions != 0) {
    DCHECK_LT(module_->num_imported_functions, module_->functions.size())((void) 0);
    // We know that the code section has been decoded if the first
    // non-imported function has its code set.
    if (!module_->functions[module_->num_imported_functions].code.is_set()) {
      errorf(pc(), "function count is %u, but code section is absent",
             module_->num_declared_functions);
      return false;
    }
  }
  // Perform a similar check for the DataCount and Data sections, where data
  // segments are declared but the Data section is absent.
  if (!CheckDataSegmentsCount(
          static_cast<uint32_t>(module_->data_segments.size()))) {
    return false;
  }
  return true;
}

ModuleResult FinishDecoding(bool verify_functions = true) {
  if (ok() && CheckMismatchedCounts()) {
    // We calculate the global offsets here, because there may not be a
    // global section and code section that would have triggered the
    // calculation before. Even without the globals section the calculation
    // is needed because globals can also be defined in the import section.
    CalculateGlobalOffsets(module_.get());
  }

  ModuleResult result = toResult(std::move(module_));
  if (verify_functions && result.ok() && intermediate_error_.has_error()) {
    // Copy error message and location.
    return ModuleResult{std::move(intermediate_error_)};
  }
  return result;
}

void set_code_section(uint32_t offset, uint32_t size) {
  module_->code = {offset, size};
}

// Decodes an entire module.
ModuleResult DecodeModule(Counters* counters, AccountingAllocator* allocator,
                          bool verify_functions = true) {
  StartDecoding(counters, allocator);
  uint32_t offset = 0;
  base::Vector<const byte> orig_bytes(start(), end() - start());
  DecodeModuleHeader(base::VectorOf(start(), end() - start()), offset);
  if (failed()) {
    return FinishDecoding(verify_functions);
  }
  // Size of the module header.
  offset += 8;
  Decoder decoder(start_ + offset, end_, offset);

  WasmSectionIterator section_iter(&decoder);

  while (ok()) {
    // Shift the offset by the section header length
    offset += section_iter.payload_start() - section_iter.section_start();
    if (section_iter.section_code() != SectionCode::kUnknownSectionCode) {
      DecodeSection(section_iter.section_code(), section_iter.payload(),
                    offset, verify_functions);
    }
    // Shift the offset by the remaining section payload
    offset += section_iter.payload_length();
    if (!section_iter.more()) break;
    section_iter.advance(true);
  }

  if (FLAG_dump_wasm_module) DumpModule(orig_bytes);

  if (decoder.failed()) {
    return decoder.toResult<std::unique_ptr<WasmModule>>(nullptr);
  }

  return FinishDecoding(verify_functions);
}

// Decodes a single anonymous function starting at {start_}.
FunctionResult DecodeSingleFunction(Zone* zone,
                                    const ModuleWireBytes& wire_bytes,
                                    const WasmModule* module,
                                    std::unique_ptr<WasmFunction> function) {
  pc_ = start_;
  expect_u8("type form", kWasmFunctionTypeCode);
  if (!ok()) return FunctionResult{std::move(intermediate_error_)};
  function->sig = consume_sig(zone);
  function->code = {off(pc_), static_cast<uint32_t>(end_ - pc_)};

  if (ok())
    VerifyFunctionBody(zone->allocator(), 0, wire_bytes, module,
                       function.get());

  if (intermediate_error_.has_error()) {
    return FunctionResult{std::move(intermediate_error_)};
  }

  return FunctionResult(std::move(function));
}

// Decodes a single function signature at {start}.
const FunctionSig* DecodeFunctionSignature(Zone* zone, const byte* start) {
  pc_ = start;
  if (!expect_u8("type form", kWasmFunctionTypeCode)) return nullptr;
  const FunctionSig* result = consume_sig(zone);
  return ok() ? result : nullptr;
}

ConstantExpression DecodeInitExprForTesting(ValueType expected) {
  return consume_init_expr(module_.get(), expected);
}

const std::shared_ptr<WasmModule>& shared_module() const { return module_; }

Counters* GetCounters() const {
  DCHECK_NOT_NULL(counters_)((void) 0);
  return counters_;
}

void SetCounters(Counters* counters) {
  DCHECK_NULL(counters_)((void) 0);
  counters_ = counters;
}

private:
const WasmFeatures enabled_features_;
std::shared_ptr<WasmModule> module_;
const byte* module_start_ = nullptr;
const byte* module_end_ = nullptr;
Counters* counters_ = nullptr;
// The type section is the first section in a module.
uint8_t next_ordered_section_ = kFirstSectionInModule;
// We store next_ordered_section_ as uint8_t instead of SectionCode so that
// we can increment it. This static_assert should make sure that SectionCode
// does not get bigger than uint8_t accidentially.
static_assert(sizeof(ModuleDecoderImpl::next_ordered_section_) ==
                  sizeof(SectionCode),
              "type mismatch");
uint32_t seen_unordered_sections_ = 0;
static_assert(kBitsPerByte *
                      sizeof(ModuleDecoderImpl::seen_unordered_sections_) >
                  kLastKnownModuleSection,
              "not enough bits");
WasmError intermediate_error_;
ModuleOrigin origin_;
AccountingAllocator allocator_;
Zone init_expr_zone_{&allocator_, "initializer expression zone"};

bool has_seen_unordered_section(SectionCode section_code) {
  return seen_unordered_sections_ & (1 << section_code);
}

void set_seen_unordered_section(SectionCode section_code) {
  seen_unordered_sections_ |= 1 << section_code;
}

uint32_t off(const byte* ptr) {
  return static_cast<uint32_t>(ptr - start_) + buffer_offset_;
}

bool AddMemory(WasmModule* module) {
  if (module->has_memory) {
    error("At most one memory is supported");
    return false;
  } else {
    module->has_memory = true;
    return true;
  }
}

// Calculate individual global offsets and total size of globals table. This
// function should be called after all globals have been defined, which is
// after the import section and the global section, but before the global
// offsets are accessed, e.g. by the function compilers. The moment when this
// function should be called is not well-defined, as the global section may
// not exist. Therefore this function is called multiple times.
void CalculateGlobalOffsets(WasmModule* module) {
  if (module->globals.empty() || module->untagged_globals_buffer_size != 0 ||
      module->tagged_globals_buffer_size != 0) {
    // This function has already been executed before, so we don't have to
    // execute it again.
    return;
  }
  uint32_t untagged_offset = 0;
  uint32_t tagged_offset = 0;
  uint32_t num_imported_mutable_globals = 0;
  for (WasmGlobal& global : module->globals) {
    if (global.mutability && global.imported) {
      global.index = num_imported_mutable_globals++;
    } else if (global.type.is_reference()) {
      global.offset = tagged_offset;
      // All entries in the tagged_globals_buffer have size 1.
      tagged_offset++;
    } else {
      int size = global.type.value_kind_size();
      untagged_offset = (untagged_offset + size - 1) & ~(size - 1);  // align
      global.offset = untagged_offset;
      untagged_offset += size;
    }
  }
  module->untagged_globals_buffer_size = untagged_offset;
  module->tagged_globals_buffer_size = tagged_offset;
}

// Verifies the body (code) of a given function.
void VerifyFunctionBody(AccountingAllocator* allocator, uint32_t func_num,
                        const ModuleWireBytes& wire_bytes,
                        const WasmModule* module, WasmFunction* function) {
  WasmFunctionName func_name(function,
                             wire_bytes.GetNameOrNull(function, module));
  if (FLAG_trace_wasm_decoder) {
    StdoutStream{} << "Verifying wasm function " << func_name << std::endl;
  }
  FunctionBody body = {
      function->sig, function->code.offset(),
      start_ + GetBufferRelativeOffset(function->code.offset()),
      start_ + GetBufferRelativeOffset(function->code.end_offset())};

  WasmFeatures unused_detected_features = WasmFeatures::None();
  DecodeResult result = VerifyWasmCode(allocator, enabled_features_, module,
                                       &unused_detected_features, body);

  // If the decode failed and this is the first error, set error code and
  // location.
  if (result.failed() && intermediate_error_.empty()) {
    // Wrap the error message from the function decoder.
    std::ostringstream error_msg;
    error_msg << "in function " << func_name << ": "
              << result.error().message();
    intermediate_error_ = WasmError{result.error().offset(), error_msg.str()};
  }
}

uint32_t consume_sig_index(WasmModule* module, const FunctionSig** sig) {
  const byte* pos = pc_;
  uint32_t sig_index = consume_u32v("signature index");
  if (!module->has_signature(sig_index)) {
    errorf(pos, "signature index %u out of bounds (%d signatures)", sig_index,
           static_cast<int>(module->types.size()));
    *sig = nullptr;
    return 0;
  }
  *sig = module->signature(sig_index);
  return sig_index;
}

uint32_t consume_tag_sig_index(WasmModule* module, const FunctionSig** sig) {
  const byte* pos = pc_;
  uint32_t sig_index = consume_sig_index(module, sig);
  if (*sig && (*sig)->return_count() != 0) {
    errorf(pos, "tag signature %u has non-void return", sig_index);
    *sig = nullptr;
    return 0;
  }
  return sig_index;
}

uint32_t consume_count(const char* name, size_t maximum) {
  const byte* p = pc_;
  uint32_t count = consume_u32v(name);
  if (count > maximum) {
    errorf(p, "%s of %u exceeds internal limit of %zu", name, count, maximum);
    return static_cast<uint32_t>(maximum);
  }
  return count;
}

uint32_t consume_func_index(WasmModule* module, WasmFunction** func,
                            const char* name) {
  return consume_index(name, &module->functions, func);
}

uint32_t consume_global_index(WasmModule* module, WasmGlobal** global) {
  return consume_index("global index", &module->globals, global);
}

uint32_t consume_table_index(WasmModule* module, WasmTable** table) {
  return consume_index("table index", &module->tables, table);
}

uint32_t consume_tag_index(WasmModule* module, WasmTag** tag) {
  return consume_index("tag index", &module->tags, tag);
}

template <typename T>
uint32_t consume_index(const char* name, std::vector<T>* vector, T** ptr) {
  const byte* pos = pc_;
  uint32_t index = consume_u32v(name);
  if (index >= vector->size()) {
    errorf(pos, "%s %u out of bounds (%d entr%s)", name, index,
           static_cast<int>(vector->size()),
           vector->size() == 1 ? "y" : "ies");
    *ptr = nullptr;
    return 0;
  }
  *ptr = &(*vector)[index];
  return index;
}

uint8_t validate_table_flags(const char* name) {
  uint8_t flags = consume_u8("table limits flags");
  STATIC_ASSERT(kNoMaximum < kWithMaximum)static_assert(kNoMaximum < kWithMaximum, "kNoMaximum < kWithMaximum"
);
  if (V8_UNLIKELY(flags > kWithMaximum)(__builtin_expect(!!(flags > kWithMaximum), 0))) {
    errorf(pc() - 1, "invalid %s limits flags", name);
  }
  return flags;
}

uint8_t validate_memory_flags(bool* has_shared_memory, bool* is_memory64) {
  uint8_t flags = consume_u8("memory limits flags");
  *has_shared_memory = false;
  switch (flags) {
    case kNoMaximum:
    case kWithMaximum:
      break;
    case kSharedNoMaximum:
    case kSharedWithMaximum:
      if (!enabled_features_.has_threads()) {
        errorf(pc() - 1,
               "invalid memory limits flags 0x%x (enable via "
               "--experimental-wasm-threads)",
               flags);
      }
      *has_shared_memory = true;
      // V8 does not support shared memory without a maximum.
      if (flags == kSharedNoMaximum) {
        errorf(pc() - 1,
               "memory limits flags must have maximum defined if shared is "
               "true");
      }
      break;
    case kMemory64NoMaximum:
    case kMemory64WithMaximum:
      if (!enabled_features_.has_memory64()) {
        errorf(pc() - 1,
               "invalid memory limits flags 0x%x (enable via "
               "--experimental-wasm-memory64)",
               flags);
      }
      *is_memory64 = true;
      break;
    default:
      errorf(pc() - 1, "invalid memory limits flags 0x%x", flags);
      break;
  }
  return flags;
}

void consume_resizable_limits(const char* name, const char* units,
                              uint32_t max_initial, uint32_t* initial,
                              bool* has_max, uint32_t max_maximum,
                              uint32_t* maximum, uint8_t flags) {
  const byte* pos = pc();
  // For memory64 we need to read the numbers as LEB-encoded 64-bit unsigned
  // integer. All V8 limits are still within uint32_t range though.
  const bool is_memory64 =
      flags == kMemory64NoMaximum || flags == kMemory64WithMaximum;
  uint64_t initial_64 = is_memory64 ? consume_u64v("initial size")
                                    : consume_u32v("initial size");
  if (initial_64 > max_initial) {
    errorf(pos,
           "initial %s size (%" PRIu64"l" "u"
           " %s) is larger than implementation limit (%u)",
           name, initial_64, units, max_initial);
  }
  *initial = static_cast<uint32_t>(initial_64);
  if (flags & 1) {
    *has_max = true;
    pos = pc();
    uint64_t maximum_64 = is_memory64 ? consume_u64v("maximum size")
                                      : consume_u32v("maximum size");
    if (maximum_64 > max_maximum) {
      errorf(pos,
             "maximum %s size (%" PRIu64"l" "u"
             " %s) is larger than implementation limit (%u)",
             name, maximum_64, units, max_maximum);
    }
    if (maximum_64 < *initial) {
      errorf(pos,
             "maximum %s size (%" PRIu64"l" "u" " %s) is less than initial (%u %s)",
             name, maximum_64, units, *initial, units);
    }
    *maximum = static_cast<uint32_t>(maximum_64);
  } else {
    *has_max = false;
    *maximum = max_initial;
  }
}

// Consumes a byte, and emits an error if it does not equal {expected}.
bool expect_u8(const char* name, uint8_t expected) {
  const byte* pos = pc();
  uint8_t value = consume_u8(name);
  if (value != expected) {
    errorf(pos, "expected %s 0x%02x, got 0x%02x", name, expected, value);
    return false;
  }
  return true;
}

ConstantExpression consume_init_expr(WasmModule* module, ValueType expected) {
  uint32_t length;

  // The error message mimics the one generated by the {WasmFullDecoder}.
1862#define TYPE_CHECK(found)                                             \
if (V8_UNLIKELY(!IsSubtypeOf(found, expected, module_.get()))(__builtin_expect(!!(!IsSubtypeOf(found, expected, module_.get
())), 0))) {    \
  errorf(pc() + 1,                                                  \
         "type error in init. expression[0] (expected %s, got %s)", \
         expected.name().c_str(), found.name().c_str());            \
  return {};                                                        \
}

  // To avoid initializing a {WasmFullDecoder} for the most common
  // expressions, we replicate their decoding and validation here. The
  // manually handled cases correspond to {ConstantExpression}'s kinds.
  // We need to make sure to check that the expression ends in {kExprEnd};
  // otherwise, it is just the first operand of a composite expression, and we
  // fall back to the default case.
  if (!more()) {
    error("Beyond end of code");
    return {};
  }
  switch (static_cast<WasmOpcode>(*pc())) {
    case kExprI32Const: {
      int32_t value =
          read_i32v<kFullValidation>(pc() + 1, &length, "i32.const");
      if (V8_UNLIKELY(failed())(__builtin_expect(!!(failed()), 0))) return {};
      if (V8_LIKELY(lookahead(1 + length, kExprEnd))(__builtin_expect(!!(lookahead(1 + length, kExprEnd)), 1))) {
        TYPE_CHECK(kWasmI32)
        consume_bytes(length + 2);
        return ConstantExpression::I32Const(value);
      }
      break;
    }
    case kExprRefFunc: {
      uint32_t index =
          read_u32v<kFullValidation>(pc() + 1, &length, "ref.func");
      if (V8_UNLIKELY(failed())(__builtin_expect(!!(failed()), 0))) return {};
      if (V8_LIKELY(lookahead(1 + length, kExprEnd))(__builtin_expect(!!(lookahead(1 + length, kExprEnd)), 1))) {
        if (V8_UNLIKELY(index >= module_->functions.size())(__builtin_expect(!!(index >= module_->functions.size()
), 0))) {
          errorf(pc() + 1, "function index %u out of bounds", index);
          return {};
        }
        ValueType type =
            enabled_features_.has_typed_funcref()
                ? ValueType::Ref(module_->functions[index].sig_index,
                                 kNonNullable)
                : kWasmFuncRef;
        TYPE_CHECK(type)
        module_->functions[index].declared = true;
        consume_bytes(length + 2);
        return ConstantExpression::RefFunc(index);
      }
      break;
    }
    case kExprRefNull: {
      HeapType type = value_type_reader::read_heap_type<kFullValidation>(
          this, pc() + 1, &length, module_.get(), enabled_features_);
      if (V8_UNLIKELY(failed())(__builtin_expect(!!(failed()), 0))) return {};
      if (V8_LIKELY(lookahead(1 + length, kExprEnd))(__builtin_expect(!!(lookahead(1 + length, kExprEnd)), 1))) {
        TYPE_CHECK(ValueType::Ref(type, kNullable))
        consume_bytes(length + 2);
        return ConstantExpression::RefNull(type.representation());
      }
      break;
    }
    default:
      break;
  }
1927#undef TYPE_CHECK

  auto sig = FixedSizeSignature<ValueType>::Returns(expected);
  FunctionBody body(&sig, buffer_offset_, pc_, end_);
  WasmFeatures detected;
  WasmFullDecoder<Decoder::kFullValidation, InitExprInterface,
                  kInitExpression>
      decoder(&init_expr_zone_, module, enabled_features_, &detected, body,
              module);

  uint32_t offset = this->pc_offset();

  decoder.DecodeFunctionBody();

  this->pc_ = decoder.end();

  if (decoder.failed()) {
    error(decoder.error().offset(), decoder.error().message().c_str());
    return {};
  }

  if (!decoder.interface().end_found()) {
    error("Initializer expression is missing 'end'");
    return {};
  }

  return ConstantExpression::WireBytes(
      offset, static_cast<uint32_t>(decoder.end() - decoder.start()));
}

// Read a mutability flag
bool consume_mutability() {
  byte val = consume_u8("mutability");
  if (val > 1) error(pc_ - 1, "invalid mutability");
  return val != 0;
}

ValueType consume_value_type() {
  uint32_t type_length;
  ValueType result = value_type_reader::read_value_type<kFullValidation>(
      this, this->pc(), &type_length, module_.get(),
      origin_ == kWasmOrigin ? enabled_features_ : WasmFeatures::None());
  consume_bytes(type_length, "value type");
  return result;
}

HeapType consume_super_type() {
  return value_type_reader::consume_heap_type(this, module_.get(),
                                              enabled_features_);
}

ValueType consume_storage_type() {
  uint8_t opcode = read_u8<kFullValidation>(this->pc());
  switch (opcode) {
    case kI8Code:
      consume_bytes(1, "i8");
      return kWasmI8;
    case kI16Code:
      consume_bytes(1, "i16");
      return kWasmI16;
    default:
      // It is not a packed type, so it has to be a value type.
      return consume_value_type();
  }
}

// Reads a reference type for tables and element segment headers.
ValueType consume_reference_type() {
  const byte* position = pc();
  ValueType result = consume_value_type();
  if (!result.is_reference()) {
    error(position, "expected reference type");
  }
  return result;
}

const FunctionSig* consume_sig(Zone* zone) {
  // Parse parameter types.
  uint32_t param_count =
      consume_count("param count", kV8MaxWasmFunctionParams);
  if (failed()) return nullptr;
  std::vector<ValueType> params;
  for (uint32_t i = 0; ok() && i < param_count; ++i) {
    params.push_back(consume_value_type());
  }
  std::vector<ValueType> returns;

  // Parse return types.
  uint32_t return_count =
      consume_count("return count", kV8MaxWasmFunctionReturns);
  if (failed()) return nullptr;
  for (uint32_t i = 0; ok() && i < return_count; ++i) {
    returns.push_back(consume_value_type());
  }
  if (failed()) return nullptr;

  // FunctionSig stores the return types first.
  ValueType* buffer = zone->NewArray<ValueType>(param_count + return_count);
  uint32_t b = 0;
  for (uint32_t i = 0; i < return_count; ++i) buffer[b++] = returns[i];
  for (uint32_t i = 0; i < param_count; ++i) buffer[b++] = params[i];

  return zone->New<FunctionSig>(return_count, param_count, buffer);
}

const StructType* consume_struct(Zone* zone) {
  uint32_t field_count = consume_count("field count", kV8MaxWasmStructFields);
  if (failed()) return nullptr;
  ValueType* fields = zone->NewArray<ValueType>(field_count);
  bool* mutabilities = zone->NewArray<bool>(field_count);
  for (uint32_t i = 0; ok() && i < field_count; ++i) {
    fields[i] = consume_storage_type();
    mutabilities[i] = consume_mutability();
  }
  if (failed()) return nullptr;
  uint32_t* offsets = zone->NewArray<uint32_t>(field_count);
  return zone->New<StructType>(field_count, offsets, fields, mutabilities);
}

const ArrayType* consume_array(Zone* zone) {
  ValueType element_type = consume_storage_type();
  bool mutability = consume_mutability();
  if (failed()) return nullptr;
  return zone->New<ArrayType>(element_type, mutability);
}

// Consume the attribute field of an exception.
uint32_t consume_exception_attribute() {
  const byte* pos = pc_;
  uint32_t attribute = consume_u32v("exception attribute");
  if (attribute != kExceptionAttribute) {
    errorf(pos, "exception attribute %u not supported", attribute);
    return 0;
  }
  return attribute;
}

WasmElemSegment consume_element_segment_header() {
  const byte* pos = pc();

  // The mask for the bit in the flag which indicates if the segment is
  // active or not (0 is active).
  constexpr uint8_t kNonActiveMask = 1 << 0;
  // The mask for the bit in the flag which indicates:
  // - for active tables, if the segment has an explicit table index field.
  // - for non-active tables, whether the table is declarative (vs. passive).
  constexpr uint8_t kHasTableIndexOrIsDeclarativeMask = 1 << 1;
  // The mask for the bit in the flag which indicates if the functions of this
  // segment are defined as function indices (0) or init. expressions (1).
  constexpr uint8_t kExpressionsAsElementsMask = 1 << 2;
  constexpr uint8_t kFullMask = kNonActiveMask |
                                kHasTableIndexOrIsDeclarativeMask |
                                kExpressionsAsElementsMask;

  uint32_t flag = consume_u32v("flag");
  if ((flag & kFullMask) != flag) {
    errorf(pos, "illegal flag value %u. Must be between 0 and 7", flag);
    return {};
  }

  const WasmElemSegment::Status status =
      (flag & kNonActiveMask) ? (flag & kHasTableIndexOrIsDeclarativeMask)
                                    ? WasmElemSegment::kStatusDeclarative
                                    : WasmElemSegment::kStatusPassive
                              : WasmElemSegment::kStatusActive;
  const bool is_active = status == WasmElemSegment::kStatusActive;

  WasmElemSegment::ElementType element_type =
      flag & kExpressionsAsElementsMask
          ? WasmElemSegment::kExpressionElements
          : WasmElemSegment::kFunctionIndexElements;

  const bool has_table_index =
      is_active && (flag & kHasTableIndexOrIsDeclarativeMask);
  uint32_t table_index = has_table_index ? consume_u32v("table index") : 0;
  if (is_active && table_index >= module_->tables.size()) {
    errorf(pos, "out of bounds%s table index %u",
           has_table_index ? " implicit" : "", table_index);
    return {};
  }
  ValueType table_type =
      is_active ? module_->tables[table_index].type : kWasmBottom;

  ConstantExpression offset;
  if (is_active) {
    offset = consume_init_expr(module_.get(), kWasmI32);
    // Failed to parse offset initializer, return early.
    if (failed()) return {};
  }

  // Denotes an active segment without table index, type, or element kind.
  const bool backwards_compatible_mode =
      is_active && !(flag & kHasTableIndexOrIsDeclarativeMask);
  ValueType type;
  if (element_type == WasmElemSegment::kExpressionElements) {
    type =
        backwards_compatible_mode ? kWasmFuncRef : consume_reference_type();
    if (is_active && !IsSubtypeOf(type, table_type, this->module_.get())) {
      errorf(pos,
             "Element segment of type %s is not a subtype of referenced "
             "table %u (of type %s)",
             type.name().c_str(), table_index, table_type.name().c_str());
      return {};
    }
  } else {
    if (!backwards_compatible_mode) {
      // We have to check that there is an element kind of type Function. All
      // other element kinds are not valid yet.
      uint8_t val = consume_u8("element kind");
      if (static_cast<ImportExportKindCode>(val) != kExternalFunction) {
        errorf(pos, "illegal element kind 0x%x. Must be 0x%x", val,
               kExternalFunction);
        return {};
      }
    }
    if (!is_active) {
      // Declarative and passive segments without explicit type are funcref.
      type = kWasmFuncRef;
    } else {
      type = table_type;
      // Active segments with function indices must reference a function
      // table. TODO(7748): Add support for anyref tables when we have them.
      if (!IsSubtypeOf(table_type, kWasmFuncRef, this->module_.get())) {
        errorf(pos,
               "An active element segment with function indices as elements "
               "must reference a table of %s. Instead, table %u of type %s "
               "is referenced.",
               enabled_features_.has_typed_funcref()
                   ? "a subtype of type funcref"
                   : "type funcref",
               table_index, table_type.name().c_str());
        return {};
      }
    }
  }

  if (is_active) {
    return {type, table_index, std::move(offset), element_type};
  } else {
    return {type, status, element_type};
  }
}

void consume_data_segment_header(bool* is_active, uint32_t* index,
                                 ConstantExpression* offset) {
  const byte* pos = pc();
  uint32_t flag = consume_u32v("flag");

  // Some flag values are only valid for specific proposals.
  if (flag != SegmentFlags::kActiveNoIndex &&
      flag != SegmentFlags::kPassive &&
      flag != SegmentFlags::kActiveWithIndex) {
    errorf(pos, "illegal flag value %u. Must be 0, 1, or 2", flag);
    return;
  }

  // We know now that the flag is valid. Time to read the rest.
  ValueType expected_type = module_->is_memory64 ? kWasmI64 : kWasmI32;
  if (flag == SegmentFlags::kActiveNoIndex) {
    *is_active = true;
    *index = 0;
    *offset = consume_init_expr(module_.get(), expected_type);
    return;
  }
  if (flag == SegmentFlags::kPassive) {
    *is_active = false;
    return;
  }
  if (flag == SegmentFlags::kActiveWithIndex) {
    *is_active = true;
    *index = consume_u32v("memory index");
    *offset = consume_init_expr(module_.get(), expected_type);
  }
}

uint32_t consume_element_func_index(ValueType expected) {
  WasmFunction* func = nullptr;
  const byte* initial_pc = pc();
  uint32_t index =
      consume_func_index(module_.get(), &func, "element function index");
  if (failed()) return index;
  DCHECK_NOT_NULL(func)((void) 0);
  DCHECK_EQ(index, func->func_index)((void) 0);
  ValueType entry_type = ValueType::Ref(func->sig_index, kNonNullable);
  if (V8_UNLIKELY(!IsSubtypeOf(entry_type, expected, module_.get()))(__builtin_expect(!!(!IsSubtypeOf(entry_type, expected, module_
.get())), 0))) {
    errorf(initial_pc,
           "Invalid type in element entry: expected %s, got %s instead.",
           expected.name().c_str(), entry_type.name().c_str());
    return index;
  }
  func->declared = true;
  return index;
}
2220};

2222ModuleResult DecodeWasmModule(
  const WasmFeatures& enabled, const byte* module_start,
  const byte* module_end, bool verify_functions, ModuleOrigin origin,
  Counters* counters, std::shared_ptr<metrics::Recorder> metrics_recorder,
  v8::metrics::Recorder::ContextId context_id, DecodingMethod decoding_method,
  AccountingAllocator* allocator) {
size_t size = module_end - module_start;
CHECK_LE(module_start, module_end)do { bool _cmp = ::v8::base::CmpLEImpl< typename ::v8::base
::pass_value_or_ref<decltype(module_start)>::type, typename
 ::v8::base::pass_value_or_ref<decltype(module_end)>::type
>((module_start), (module_end)); do { if ((__builtin_expect
(!!(!(_cmp)), 0))) { V8_Fatal("Check failed: %s.", "module_start"
 " " "<=" " " "module_end"); } } while (false); } while (false
);
size_t max_size = max_module_size();
if (size > max_size) {
  return ModuleResult{
      WasmError{0, "size > maximum module size (%zu): %zu", max_size, size}};
}
// TODO(bradnelson): Improve histogram handling of size_t.
auto size_counter =
    SELECT_WASM_COUNTER(counters, origin, wasm, module_size_bytes)((origin) == kWasmOrigin ? (counters)->wasm_wasm_module_size_bytes
() : (counters)->wasm_asm_module_size_bytes());
size_counter->AddSample(static_cast<int>(size));
// Signatures are stored in zone memory, which have the same lifetime
// as the {module}.
ModuleDecoderImpl decoder(enabled, module_start, module_end, origin);
v8::metrics::WasmModuleDecoded metrics_event;
base::ElapsedTimer timer;
timer.Start();
base::ThreadTicks thread_ticks = base::ThreadTicks::IsSupported()
                                     ? base::ThreadTicks::Now()
                                     : base::ThreadTicks();
ModuleResult result =
    decoder.DecodeModule(counters, allocator, verify_functions);

// Record event metrics.
metrics_event.wall_clock_duration_in_us = timer.Elapsed().InMicroseconds();
timer.Stop();
if (!thread_ticks.IsNull()) {
  metrics_event.cpu_duration_in_us =
      (base::ThreadTicks::Now() - thread_ticks).InMicroseconds();
}
metrics_event.success = decoder.ok() && result.ok();
metrics_event.async = decoding_method == DecodingMethod::kAsync ||
                      decoding_method == DecodingMethod::kAsyncStream;
metrics_event.streamed = decoding_method == DecodingMethod::kSyncStream ||
                         decoding_method == DecodingMethod::kAsyncStream;
if (result.ok()) {
  metrics_event.function_count = result.value()->num_declared_functions;
} else if (auto&& module = decoder.shared_module()) {
  metrics_event.function_count = module->num_declared_functions;
}
metrics_event.module_size_in_bytes = size;
metrics_recorder->DelayMainThreadEvent(metrics_event, context_id);

return result;
2272}

2274ModuleDecoder::ModuleDecoder(const WasmFeatures& enabled)
  : enabled_features_(enabled) {}

2277ModuleDecoder::~ModuleDecoder() = default;

2279const std::shared_ptr<WasmModule>& ModuleDecoder::shared_module() const {
return impl_->shared_module();
2281}

2283void ModuleDecoder::StartDecoding(
  Counters* counters, std::shared_ptr<metrics::Recorder> metrics_recorder,
  v8::metrics::Recorder::ContextId context_id, AccountingAllocator* allocator,
  ModuleOrigin origin) {
DCHECK_NULL(impl_)((void) 0);
impl_.reset(new ModuleDecoderImpl(enabled_features_, origin));
impl_->StartDecoding(counters, allocator);
2290}

2292void ModuleDecoder::DecodeModuleHeader(base::Vector<const uint8_t> bytes,
                                     uint32_t offset) {
impl_->DecodeModuleHeader(bytes, offset);
2295}

2297void ModuleDecoder::DecodeSection(SectionCode section_code,
                                base::Vector<const uint8_t> bytes,
                                uint32_t offset, bool verify_functions) {
impl_->DecodeSection(section_code, bytes, offset, verify_functions);
1
Calling 'ModuleDecoderImpl::DecodeSection'→
2301}

2303void ModuleDecoder::DecodeFunctionBody(uint32_t index, uint32_t length,
                                     uint32_t offset, bool verify_functions) {
impl_->DecodeFunctionBody(index, length, offset, verify_functions);
2306}

2308void ModuleDecoder::StartCodeSection() { impl_->StartCodeSection(); }

2310bool ModuleDecoder::CheckFunctionsCount(uint32_t functions_count,
                                      uint32_t error_offset) {
return impl_->CheckFunctionsCount(functions_count, error_offset);
2313}

2315ModuleResult ModuleDecoder::FinishDecoding(bool verify_functions) {
return impl_->FinishDecoding(verify_functions);
2317}

2319void ModuleDecoder::set_code_section(uint32_t offset, uint32_t size) {
return impl_->set_code_section(offset, size);
2321}

2323size_t ModuleDecoder::IdentifyUnknownSection(ModuleDecoder* decoder,
                                           base::Vector<const uint8_t> bytes,
                                           uint32_t offset,
                                           SectionCode* result) {
if (!decoder->ok()) return 0;
decoder->impl_->Reset(bytes, offset);
*result = IdentifyUnknownSectionInternal(decoder->impl_.get());
return decoder->impl_->pc() - bytes.begin();
2331}

2333bool ModuleDecoder::ok() { return impl_->ok(); }

2335const FunctionSig* DecodeWasmSignatureForTesting(const WasmFeatures& enabled,
                                               Zone* zone, const byte* start,
                                               const byte* end) {
ModuleDecoderImpl decoder(enabled, start, end, kWasmOrigin);
return decoder.DecodeFunctionSignature(zone, start);
2340}

2342ConstantExpression DecodeWasmInitExprForTesting(const WasmFeatures& enabled,
                                              const byte* start,
                                              const byte* end,
                                              ValueType expected) {
ModuleDecoderImpl decoder(enabled, start, end, kWasmOrigin);
AccountingAllocator allocator;
decoder.StartDecoding(nullptr, &allocator);
return decoder.DecodeInitExprForTesting(expected);
2350}

2352FunctionResult DecodeWasmFunctionForTesting(
  const WasmFeatures& enabled, Zone* zone, const ModuleWireBytes& wire_bytes,
  const WasmModule* module, const byte* function_start,
  const byte* function_end, Counters* counters) {
size_t size = function_end - function_start;
CHECK_LE(function_start, function_end)do { bool _cmp = ::v8::base::CmpLEImpl< typename ::v8::base
::pass_value_or_ref<decltype(function_start)>::type, typename
 ::v8::base::pass_value_or_ref<decltype(function_end)>::
type>((function_start), (function_end)); do { if ((__builtin_expect
(!!(!(_cmp)), 0))) { V8_Fatal("Check failed: %s.", "function_start"
 " " "<=" " " "function_end"); } } while (false); } while (
false);
if (size > kV8MaxWasmFunctionSize) {
  return FunctionResult{WasmError{0,
                                  "size > maximum function size (%zu): %zu",
                                  kV8MaxWasmFunctionSize, size}};
}
ModuleDecoderImpl decoder(enabled, function_start, function_end, kWasmOrigin);
decoder.SetCounters(counters);
return decoder.DecodeSingleFunction(zone, wire_bytes, module,
                                    std::make_unique<WasmFunction>());
2367}

2369AsmJsOffsetsResult DecodeAsmJsOffsets(
  base::Vector<const uint8_t> encoded_offsets) {
std::vector<AsmJsOffsetFunctionEntries> functions;

Decoder decoder(encoded_offsets);
uint32_t functions_count = decoder.consume_u32v("functions count");
// Consistency check.
DCHECK_GE(encoded_offsets.size(), functions_count)((void) 0);
functions.reserve(functions_count);

for (uint32_t i = 0; i < functions_count; ++i) {
  uint32_t size = decoder.consume_u32v("table size");
  if (size == 0) {
    functions.emplace_back();
    continue;
  }
  DCHECK(decoder.checkAvailable(size))((void) 0);
  const byte* table_end = decoder.pc() + size;
  uint32_t locals_size = decoder.consume_u32v("locals size");
  int function_start_position = decoder.consume_u32v("function start pos");
  int function_end_position = function_start_position;
  int last_byte_offset = locals_size;
  int last_asm_position = function_start_position;
  std::vector<AsmJsOffsetEntry> func_asm_offsets;
  func_asm_offsets.reserve(size / 4);  // conservative estimation
  // Add an entry for the stack check, associated with position 0.
  func_asm_offsets.push_back(
      {0, function_start_position, function_start_position});
  while (decoder.pc() < table_end) {
    DCHECK(decoder.ok())((void) 0);
    last_byte_offset += decoder.consume_u32v("byte offset delta");
    int call_position =
        last_asm_position + decoder.consume_i32v("call position delta");
    int to_number_position =
        call_position + decoder.consume_i32v("to_number position delta");
    last_asm_position = to_number_position;
    if (decoder.pc() == table_end) {
      // The last entry is the function end marker.
      DCHECK_EQ(call_position, to_number_position)((void) 0);
      function_end_position = call_position;
    } else {
      func_asm_offsets.push_back(
          {last_byte_offset, call_position, to_number_position});
    }
  }
  DCHECK_EQ(decoder.pc(), table_end)((void) 0);
  functions.emplace_back(AsmJsOffsetFunctionEntries{
      function_start_position, function_end_position,
      std::move(func_asm_offsets)});
}
DCHECK(decoder.ok())((void) 0);
DCHECK(!decoder.more())((void) 0);

return decoder.toResult(AsmJsOffsets{std::move(functions)});
2423}

2425std::vector<CustomSectionOffset> DecodeCustomSections(const byte* start,
                                                    const byte* end) {
Decoder decoder(start, end);
decoder.consume_bytes(4, "wasm magic");
decoder.consume_bytes(4, "wasm version");

std::vector<CustomSectionOffset> result;

while (decoder.more()) {
  byte section_code = decoder.consume_u8("section code");
  uint32_t section_length = decoder.consume_u32v("section length");
  uint32_t section_start = decoder.pc_offset();
  if (section_code != 0) {
    // Skip known sections.
    decoder.consume_bytes(section_length, "section bytes");
    continue;
  }
  uint32_t name_length = decoder.consume_u32v("name length");
  uint32_t name_offset = decoder.pc_offset();
  decoder.consume_bytes(name_length, "section name");
  uint32_t payload_offset = decoder.pc_offset();
  if (section_length < (payload_offset - section_start)) {
    decoder.error("invalid section length");
    break;
  }
  uint32_t payload_length = section_length - (payload_offset - section_start);
  decoder.consume_bytes(payload_length);
  if (decoder.failed()) break;
  result.push_back({{section_start, section_length},
                    {name_offset, name_length},
                    {payload_offset, payload_length}});
}

return result;
2459}

2461namespace {

2463bool FindNameSection(Decoder* decoder) {
static constexpr int kModuleHeaderSize = 8;
decoder->consume_bytes(kModuleHeaderSize, "module header");

WasmSectionIterator section_iter(decoder);

while (decoder->ok() && section_iter.more() &&
       section_iter.section_code() != kNameSectionCode) {
  section_iter.advance(true);
}
if (!section_iter.more()) return false;

// Reset the decoder to not read beyond the name section end.
decoder->Reset(section_iter.payload(), decoder->pc_offset());
return true;
2478}

2480}  // namespace

2482void DecodeFunctionNames(const byte* module_start, const byte* module_end,
                       std::unordered_map<uint32_t, WireBytesRef>* names) {
DCHECK_NOT_NULL(names)((void) 0);
DCHECK(names->empty())((void) 0);

Decoder decoder(module_start, module_end);
if (FindNameSection(&decoder)) {
  while (decoder.ok() && decoder.more()) {
    uint8_t name_type = decoder.consume_u8("name type");
    if (name_type & 0x80) break;  // no varuint7

    uint32_t name_payload_len = decoder.consume_u32v("name payload length");
    if (!decoder.checkAvailable(name_payload_len)) break;

    if (name_type != NameSectionKindCode::kFunctionCode) {
      decoder.consume_bytes(name_payload_len, "name subsection payload");
      continue;
    }
    uint32_t functions_count = decoder.consume_u32v("functions count");

    for (; decoder.ok() && functions_count > 0; --functions_count) {
      uint32_t function_index = decoder.consume_u32v("function index");
      WireBytesRef name = consume_string(&decoder, false, "function name");

      // Be lenient with errors in the name section: Ignore non-UTF8 names.
      // You can even assign to the same function multiple times (last valid
      // one wins).
      if (decoder.ok() && validate_utf8(&decoder, name)) {
        names->insert(std::make_pair(function_index, name));
      }
    }
  }
}
2515}

2517NameMap DecodeNameMap(base::Vector<const uint8_t> module_bytes,
                    uint8_t name_section_kind) {
Decoder decoder(module_bytes);
if (!FindNameSection(&decoder)) return NameMap{{}};

std::vector<NameAssoc> names;
while (decoder.ok() && decoder.more()) {
  uint8_t name_type = decoder.consume_u8("name type");
  if (name_type & 0x80) break;  // no varuint7

  uint32_t name_payload_len = decoder.consume_u32v("name payload length");
  if (!decoder.checkAvailable(name_payload_len)) break;

  if (name_type != name_section_kind) {
    decoder.consume_bytes(name_payload_len, "name subsection payload");
    continue;
  }

  uint32_t count = decoder.consume_u32v("names count");
  for (uint32_t i = 0; i < count; i++) {
    uint32_t index = decoder.consume_u32v("index");
    WireBytesRef name = consume_string(&decoder, false, "name");
    if (!decoder.ok()) break;
    if (index > kMaxInt) continue;
    if (!validate_utf8(&decoder, name)) continue;
    names.emplace_back(static_cast<int>(index), name);
  }
}
std::stable_sort(names.begin(), names.end(), NameAssoc::IndexLess{});
return NameMap{std::move(names)};
2547}

2549IndirectNameMap DecodeIndirectNameMap(base::Vector<const uint8_t> module_bytes,
                                    uint8_t name_section_kind) {
Decoder decoder(module_bytes);
if (!FindNameSection(&decoder)) return IndirectNameMap{{}};

std::vector<IndirectNameMapEntry> entries;
while (decoder.ok() && decoder.more()) {
  uint8_t name_type = decoder.consume_u8("name type");
  if (name_type & 0x80) break;  // no varuint7

  uint32_t name_payload_len = decoder.consume_u32v("name payload length");
  if (!decoder.checkAvailable(name_payload_len)) break;

  if (name_type != name_section_kind) {
    decoder.consume_bytes(name_payload_len, "name subsection payload");
    continue;
  }

  uint32_t outer_count = decoder.consume_u32v("outer count");
  for (uint32_t i = 0; i < outer_count; ++i) {
    uint32_t outer_index = decoder.consume_u32v("outer index");
    if (outer_index > kMaxInt) continue;
    std::vector<NameAssoc> names;
    uint32_t inner_count = decoder.consume_u32v("inner count");
    for (uint32_t k = 0; k < inner_count; ++k) {
      uint32_t inner_index = decoder.consume_u32v("inner index");
      WireBytesRef name = consume_string(&decoder, false, "name");
      if (!decoder.ok()) break;
      if (inner_index > kMaxInt) continue;
      // Ignore non-utf8 names.
      if (!validate_utf8(&decoder, name)) continue;
      names.emplace_back(static_cast<int>(inner_index), name);
    }
    // Use stable sort to get deterministic names (the first one declared)
    // even in the presence of duplicates.
    std::stable_sort(names.begin(), names.end(), NameAssoc::IndexLess{});
    entries.emplace_back(static_cast<int>(outer_index), std::move(names));
  }
}
std::stable_sort(entries.begin(), entries.end(),
                 IndirectNameMapEntry::IndexLess{});
return IndirectNameMap{std::move(entries)};
2591}

2593#undef TRACE

2595}  // namespace wasm
2596}  // namespace internal
2597}  // namespace v8

←

../deps/v8/src/wasm/wasm-module.h

1// Copyright 2015 the V8 project authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.

5#if !V8_ENABLE_WEBASSEMBLY1
6#error This header should only be included if WebAssembly is enabled.
7#endif  // !V8_ENABLE_WEBASSEMBLY

9#ifndef V8_WASM_WASM_MODULE_H_
10#define V8_WASM_WASM_MODULE_H_

12#include <map>
13#include <memory>

15#include "src/base/optional.h"
16#include "src/base/platform/wrappers.h"
17#include "src/base/vector.h"
18#include "src/common/globals.h"
19#include "src/handles/handles.h"
20#include "src/wasm/branch-hint-map.h"
21#include "src/wasm/signature-map.h"
22#include "src/wasm/struct-types.h"
23#include "src/wasm/wasm-constants.h"
24#include "src/wasm/wasm-init-expr.h"
25#include "src/wasm/wasm-limits.h"

27namespace v8 {

29namespace internal {

31class WasmModuleObject;

33namespace wasm {

35using WasmName = base::Vector<const char>;

37struct AsmJsOffsets;
38class ErrorThrower;

40// Reference to a string in the wire bytes.
41class WireBytesRef {
public:
WireBytesRef() : WireBytesRef(0, 0) {}
WireBytesRef(uint32_t offset, uint32_t length)
    : offset_(offset), length_(length) {
  DCHECK_IMPLIES(offset_ == 0, length_ == 0)((void) 0);
  DCHECK_LE(offset_, offset_ + length_)((void) 0);  // no uint32_t overflow.
}

uint32_t offset() const { return offset_; }
uint32_t length() const { return length_; }
uint32_t end_offset() const { return offset_ + length_; }
bool is_empty() const { return length_ == 0; }
bool is_set() const { return offset_ != 0; }

private:
uint32_t offset_;
uint32_t length_;
59};

61// Static representation of a wasm function.
62struct WasmFunction {
const FunctionSig* sig;  // signature of the function.
uint32_t func_index;     // index into the function table.
uint32_t sig_index;      // index into the signature table.
WireBytesRef code;       // code of this function.
// Required number of slots in a feedback vector. Marked {mutable} because
// this is computed late (by Liftoff compilation), when the rest of the
// {WasmFunction} is typically considered {const}.
mutable int feedback_slots;
bool imported;
bool exported;
bool declared;
74};

76// A representation of a constant expression. The most common expression types
77// are hard-coded, while the rest are represented as a {WireBytesRef}.
78class ConstantExpression {
public:
enum Kind {
  kEmpty,
  kI32Const,
  kRefNull,
  kRefFunc,
  kWireBytesRef,
  kLastKind = kWireBytesRef
};

union Value {
  int32_t i32_value;
  uint32_t index_or_offset;
  HeapType::Representation repr;
};

ConstantExpression() : bit_field_(KindField::encode(kEmpty)) {}

static ConstantExpression I32Const(int32_t value) {
  return ConstantExpression(ValueField::encode(value) |
                            KindField::encode(kI32Const));
}
static ConstantExpression RefFunc(uint32_t index) {
  return ConstantExpression(ValueField::encode(index) |
                            KindField::encode(kRefFunc));
}
static ConstantExpression RefNull(HeapType::Representation repr) {
  return ConstantExpression(ValueField::encode(repr) |
                            KindField::encode(kRefNull));
}
static ConstantExpression WireBytes(uint32_t offset, uint32_t length) {
  return ConstantExpression(OffsetField::encode(offset) |
                            LengthField::encode(length) |
                            KindField::encode(kWireBytesRef));
}

Kind kind() const { return KindField::decode(bit_field_); }

bool is_set() const { return kind() != kEmpty; }

uint32_t index() const {
  DCHECK_EQ(kind(), kRefFunc)((void) 0);
  return ValueField::decode(bit_field_);
}

HeapType::Representation repr() const {
  DCHECK_EQ(kind(), kRefNull)((void) 0);
  return static_cast<HeapType::Representation>(
      ValueField::decode(bit_field_));
}

int32_t i32_value() const {
  DCHECK_EQ(kind(), kI32Const)((void) 0);
  return ValueField::decode(bit_field_);
}

WireBytesRef wire_bytes_ref() const {
  DCHECK_EQ(kind(), kWireBytesRef)((void) 0);
  return WireBytesRef(OffsetField::decode(bit_field_),
                      LengthField::decode(bit_field_));
}

private:
static constexpr int kValueBits = 32;
static constexpr int kLengthBits = 30;
static constexpr int kOffsetBits = 30;
static constexpr int kKindBits = 3;

// There are two possible combinations of fields: offset + length + kind if
// kind = kWireBytesRef, or value + kind for anything else.
using ValueField = base::BitField<uint32_t, 0, kValueBits, uint64_t>;
using OffsetField = base::BitField<uint32_t, 0, kOffsetBits, uint64_t>;
using LengthField = OffsetField::Next<uint32_t, kLengthBits>;
using KindField = LengthField::Next<Kind, kKindBits>;

// Make sure we reserve enough bits for a {WireBytesRef}'s length and offset.
STATIC_ASSERT(kV8MaxWasmModuleSize <= LengthField::kMax + 1)static_assert(kV8MaxWasmModuleSize <= LengthField::kMax + 1
, "kV8MaxWasmModuleSize <= LengthField::kMax + 1");
STATIC_ASSERT(kV8MaxWasmModuleSize <= OffsetField::kMax + 1)static_assert(kV8MaxWasmModuleSize <= OffsetField::kMax + 1
, "kV8MaxWasmModuleSize <= OffsetField::kMax + 1");
// Make sure kind fits in kKindBits.
STATIC_ASSERT(kLastKind <= KindField::kMax + 1)static_assert(kLastKind <= KindField::kMax + 1, "kLastKind <= KindField::kMax + 1"
);

explicit ConstantExpression(uint64_t bit_field) : bit_field_(bit_field) {}

uint64_t bit_field_;
163};

165// We want to keep {ConstantExpression} small to reduce memory usage during
166// compilation/instantiation.
167STATIC_ASSERT(sizeof(ConstantExpression) <= 8)static_assert(sizeof(ConstantExpression) <= 8, "sizeof(ConstantExpression) <= 8"
);

169// Static representation of a wasm global variable.
170struct WasmGlobal {
ValueType type;           // type of the global.
bool mutability;          // {true} if mutable.
ConstantExpression init;  // the initialization expression of the global.
union {
  // Index of imported mutable global.
  uint32_t index;
  // Offset into global memory (if not imported & mutable). Expressed in bytes
  // for value-typed globals, and in tagged words for reference-typed globals.
  uint32_t offset;
};
bool imported;  // true if imported.
bool exported;  // true if exported.
183};

185// Note: An exception tag signature only uses the params portion of a function
186// signature.
187using WasmTagSig = FunctionSig;

189// Static representation of a wasm tag type.
190struct WasmTag {
explicit WasmTag(const WasmTagSig* sig) : sig(sig) {}
const FunctionSig* ToFunctionSig() const { return sig; }

const WasmTagSig* sig;  // type signature of the tag.
195};

197// Static representation of a wasm data segment.
198struct WasmDataSegment {
// Construct an active segment.
explicit WasmDataSegment(ConstantExpression dest_addr)
    : dest_addr(dest_addr), active(true) {}

// Construct a passive segment, which has no dest_addr.
WasmDataSegment() : active(false) {}

ConstantExpression dest_addr;  // destination memory address of the data.
WireBytesRef source;           // start offset in the module bytes.
bool active = true;  // true if copied automatically during instantiation.
209};

211// Static representation of wasm element segment (table initializer).
212struct WasmElemSegment {
enum Status {
  kStatusActive,      // copied automatically during instantiation.
  kStatusPassive,     // copied explicitly after instantiation.
  kStatusDeclarative  // purely declarative and never copied.
};
enum ElementType { kFunctionIndexElements, kExpressionElements };

// Construct an active segment.
WasmElemSegment(ValueType type, uint32_t table_index,
                ConstantExpression offset, ElementType element_type)
    : status(kStatusActive),
      type(type),
      table_index(table_index),
      offset(std::move(offset)),
      element_type(element_type) {}

// Construct a passive or declarative segment, which has no table index or
// offset.
WasmElemSegment(ValueType type, Status status, ElementType element_type)
    : status(status), type(type), table_index(0), element_type(element_type) {
  DCHECK_NE(status, kStatusActive)((void) 0);
}

// Default constructor. Constucts an invalid segment.
WasmElemSegment()
    : status(kStatusActive),
      type(kWasmBottom),
      table_index(0),
      element_type(kFunctionIndexElements) {}

WasmElemSegment(const WasmElemSegment&) = delete;
WasmElemSegment(WasmElemSegment&&) V8_NOEXCEPTnoexcept = default;
WasmElemSegment& operator=(const WasmElemSegment&) = delete;
WasmElemSegment& operator=(WasmElemSegment&&) V8_NOEXCEPTnoexcept = default;

Status status;
ValueType type;
uint32_t table_index;
ConstantExpression offset;
ElementType element_type;
std::vector<ConstantExpression> entries;
254};

256// Static representation of a wasm import.
257struct WasmImport {
WireBytesRef module_name;   // module name.
WireBytesRef field_name;    // import name.
ImportExportKindCode kind;  // kind of the import.
uint32_t index;             // index into the respective space.
262};

264// Static representation of a wasm export.
265struct WasmExport {
WireBytesRef name;          // exported name.
ImportExportKindCode kind;  // kind of the export.
uint32_t index;             // index into the respective space.
269};

271enum class WasmCompilationHintStrategy : uint8_t {
kDefault = 0,
kLazy = 1,
kEager = 2,
kLazyBaselineEagerTopTier = 3,
276};

278enum class WasmCompilationHintTier : uint8_t {
kDefault = 0,
kBaseline = 1,
kOptimized = 2,
282};

284// Static representation of a wasm compilation hint
285struct WasmCompilationHint {
WasmCompilationHintStrategy strategy;
WasmCompilationHintTier baseline_tier;
WasmCompilationHintTier top_tier;
289};

291enum ModuleOrigin : uint8_t {
kWasmOrigin,
kAsmJsSloppyOrigin,
kAsmJsStrictOrigin
295};

297#define SELECT_WASM_COUNTER(counters, origin, prefix, suffix)((origin) == kWasmOrigin ? (counters)->prefix_wasm_suffix(
) : (counters)->prefix_asm_suffix())     \
((origin) == kWasmOrigin ? (counters)->prefix##_wasm_##suffix() \
                         : (counters)->prefix##_asm_##suffix())

301struct ModuleWireBytes;

303class V8_EXPORT_PRIVATE LazilyGeneratedNames {
public:
WireBytesRef LookupFunctionName(const ModuleWireBytes& wire_bytes,
                                uint32_t function_index) const;

void AddForTesting(int function_index, WireBytesRef name);

private:
// {function_names_} are populated lazily after decoding, and
// therefore need a mutex to protect concurrent modifications
// from multiple {WasmModuleObject}.
mutable base::Mutex mutex_;
mutable std::unique_ptr<std::unordered_map<uint32_t, WireBytesRef>>
    function_names_;
317};

319class V8_EXPORT_PRIVATE AsmJsOffsetInformation {
public:
explicit AsmJsOffsetInformation(base::Vector<const byte> encoded_offsets);

// Destructor defined in wasm-module.cc, where the definition of
// {AsmJsOffsets} is available.
~AsmJsOffsetInformation();

int GetSourcePosition(int func_index, int byte_offset,
                      bool is_at_number_conversion);

std::pair<int, int> GetFunctionOffsets(int func_index);

private:
void EnsureDecodedOffsets();

// The offset information table is decoded lazily, hence needs to be
// protected against concurrent accesses.
// Exactly one of the two fields below will be set at a time.
mutable base::Mutex mutex_;

// Holds the encoded offset table bytes.
base::OwnedVector<const uint8_t> encoded_offsets_;

// Holds the decoded offset table.
std::unique_ptr<AsmJsOffsets> decoded_offsets_;
345};

347// Used as the supertype for a type at the top of the type hierarchy.
348constexpr uint32_t kNoSuperType = std::numeric_limits<uint32_t>::max();

350struct TypeDefinition {
enum Kind { kFunction, kStruct, kArray };

TypeDefinition(const FunctionSig* sig, uint32_t supertype)
    : function_sig(sig), supertype(supertype), kind(kFunction) {}
TypeDefinition(const StructType* type, uint32_t supertype)
    : struct_type(type), supertype(supertype), kind(kStruct) {}
TypeDefinition(const ArrayType* type, uint32_t supertype)
    : array_type(type), supertype(supertype), kind(kArray) {}
TypeDefinition()
    : function_sig(nullptr), supertype(kNoSuperType), kind(kFunction) {}

union {
  const FunctionSig* function_sig;
  const StructType* struct_type;
  const ArrayType* array_type;
};

bool operator==(const TypeDefinition& other) const {
  if (supertype != other.supertype || kind != other.kind) {
    return false;
  }
  switch (kind) {
    case kFunction:
      return *function_sig == *other.function_sig;
    case kStruct:
      return *struct_type == *other.struct_type;
    case kArray:
      return *array_type == *other.array_type;
  }
}

bool operator!=(const TypeDefinition& other) const {
  return !(*this == other);
}

uint32_t supertype;
Kind kind;
388};

390struct V8_EXPORT_PRIVATE WasmDebugSymbols {
enum class Type { None, SourceMap, EmbeddedDWARF, ExternalDWARF };
Type type = Type::None;
WireBytesRef external_url;
394};

396struct CallSiteFeedback {
int function_index;
int absolute_call_frequency;
399};
400struct FunctionTypeFeedback {
std::vector<CallSiteFeedback> feedback_vector;
std::map<WasmCodePosition, int> positions;
int tierup_priority = 0;
404};
405struct TypeFeedbackStorage {
std::map<uint32_t, FunctionTypeFeedback> feedback_for_function;
// Accesses to {feedback_for_function} are guarded by this mutex.
base::Mutex mutex;
409};

411struct WasmTable;

413// Static representation of a module.
414struct V8_EXPORT_PRIVATE WasmModule {
std::unique_ptr<Zone> signature_zone;
uint32_t initial_pages = 0;      // initial size of the memory in 64k pages
uint32_t maximum_pages = 0;      // maximum size of the memory in 64k pages
bool has_shared_memory = false;  // true if memory is a SharedArrayBuffer
bool has_maximum_pages = false;  // true if there is a maximum memory size
bool is_memory64 = false;        // true if the memory is 64 bit
bool has_memory = false;         // true if the memory was defined or imported
bool mem_export = false;         // true if the memory is exported
int start_function_index = -1;   // start function, >= 0 if any

// Size of the buffer required for all globals that are not imported and
// mutable.
uint32_t untagged_globals_buffer_size = 0;
uint32_t tagged_globals_buffer_size = 0;
uint32_t num_imported_mutable_globals = 0;
uint32_t num_imported_functions = 0;
uint32_t num_imported_tables = 0;
uint32_t num_declared_functions = 0;  // excluding imported
uint32_t num_exported_functions = 0;
uint32_t num_declared_data_segments = 0;  // From the DataCount section.
// Position and size of the code section (payload only, i.e. without section
// ID and length).
WireBytesRef code = {0, 0};
WireBytesRef name = {0, 0};

void add_type(TypeDefinition type) {
  types.push_back(type);
  uint32_t canonical_id = type.kind23.1
Field 'kind' is equal to kFunction
1
Field 'kind' is equal to kFunction
 == TypeDefinition::kFunction
24
←
'?' condition is true→
                              ? signature_map.FindOrInsert(*type.function_sig)
25
←
Forming reference to null pointer
                              : 0;
  canonicalized_type_ids.push_back(canonical_id);
  // Canonical type will be computed later.
  isorecursive_canonical_type_ids.push_back(kNoSuperType);
}

bool has_type(uint32_t index) const { return index < types.size(); }

void add_signature(const FunctionSig* sig, uint32_t supertype) {
  DCHECK_NOT_NULL(sig)((void) 0);
  add_type(TypeDefinition(sig, supertype));
}
bool has_signature(uint32_t index) const {
  return index < types.size() &&
         types[index].kind == TypeDefinition::kFunction;
}
const FunctionSig* signature(uint32_t index) const {
  DCHECK(has_signature(index))((void) 0);
  return types[index].function_sig;
}

void add_struct_type(const StructType* type, uint32_t supertype) {
  DCHECK_NOT_NULL(type)((void) 0);
  add_type(TypeDefinition(type, supertype));
}
bool has_struct(uint32_t index) const {
  return index < types.size() && types[index].kind == TypeDefinition::kStruct;
}
const StructType* struct_type(uint32_t index) const {
  DCHECK(has_struct(index))((void) 0);
  return types[index].struct_type;
}

void add_array_type(const ArrayType* type, uint32_t supertype) {
  DCHECK_NOT_NULL(type)((void) 0);
  add_type(TypeDefinition(type, supertype));
}
bool has_array(uint32_t index) const {
  return index < types.size() && types[index].kind == TypeDefinition::kArray;
}
const ArrayType* array_type(uint32_t index) const {
  DCHECK(has_array(index))((void) 0);
  return types[index].array_type;
}

uint32_t supertype(uint32_t index) const {
  DCHECK(index < types.size())((void) 0);
  return types[index].supertype;
}
bool has_supertype(uint32_t index) const {
  return supertype(index) != kNoSuperType;
}

std::vector<TypeDefinition> types;  // by type index
// TODO(7748): Unify the following two arrays.
// Maps each type index to a canonical index for purposes of call_indirect.
std::vector<uint32_t> canonicalized_type_ids;
// Maps each type index to its global (cross-module) canonical index as per
// isorecursive type canonicalization.
std::vector<uint32_t> isorecursive_canonical_type_ids;
// Canonicalizing map for signature indexes.
SignatureMap signature_map;
std::vector<WasmFunction> functions;
std::vector<WasmGlobal> globals;
std::vector<WasmDataSegment> data_segments;
std::vector<WasmTable> tables;
std::vector<WasmImport> import_table;
std::vector<WasmExport> export_table;
std::vector<WasmTag> tags;
std::vector<WasmElemSegment> elem_segments;
std::vector<WasmCompilationHint> compilation_hints;
BranchHintInfo branch_hints;
mutable TypeFeedbackStorage type_feedback;

ModuleOrigin origin = kWasmOrigin;  // origin of the module
LazilyGeneratedNames lazily_generated_names;
WasmDebugSymbols debug_symbols;

// Asm.js source position information. Only available for modules compiled
// from asm.js.
std::unique_ptr<AsmJsOffsetInformation> asm_js_offset_information;

explicit WasmModule(std::unique_ptr<Zone> signature_zone = nullptr);
WasmModule(const WasmModule&) = delete;
WasmModule& operator=(const WasmModule&) = delete;
529};

531// Static representation of a wasm indirect call table.
532struct WasmTable {
MOVE_ONLY_WITH_DEFAULT_CONSTRUCTORS(WasmTable)WasmTable() = default; WasmTable(WasmTable&&) noexcept
 = default; WasmTable& operator=(WasmTable&&) noexcept
 = default; WasmTable(const WasmTable&) = delete; WasmTable
& operator=(const WasmTable&) = delete;

// 'module' can be nullptr
// TODO(9495): Update this function as more table types are supported, or
// remove it completely when all reference types are allowed.
static bool IsValidTableType(ValueType type, const WasmModule* module) {
  if (!type.is_object_reference()) return false;
  HeapType heap_type = type.heap_type();
  return heap_type == HeapType::kFunc || heap_type == HeapType::kAny ||
         (module != nullptr && heap_type.is_index() &&
          module->has_signature(heap_type.ref_index()));
}

ValueType type = kWasmVoid;     // table type.
uint32_t initial_size = 0;      // initial table size.
uint32_t maximum_size = 0;      // maximum table size.
bool has_maximum_size = false;  // true if there is a maximum size.
bool imported = false;          // true if imported.
bool exported = false;          // true if exported.
ConstantExpression initial_value;
553};

555inline bool is_asmjs_module(const WasmModule* module) {
return module->origin != kWasmOrigin;
557}

559size_t EstimateStoredSize(const WasmModule* module);

561// Returns the number of possible export wrappers for a given module.
562V8_EXPORT_PRIVATE int MaxNumExportWrappers(const WasmModule* module);

564// Returns the wrapper index for a function in {module} with signature {sig}
565// or {sig_index} and origin defined by {is_import}.
566// Prefer to use the {sig_index} consuming version, as it is much faster.
567int GetExportWrapperIndex(const WasmModule* module, const FunctionSig* sig,
                        bool is_import);
569int GetExportWrapperIndex(const WasmModule* module, uint32_t sig_index,
                        bool is_import);

572// Return the byte offset of the function identified by the given index.
573// The offset will be relative to the start of the module bytes.
574// Returns -1 if the function index is invalid.
575int GetWasmFunctionOffset(const WasmModule* module, uint32_t func_index);

577// Returns the function containing the given byte offset.
578// Returns -1 if the byte offset is not contained in any
579// function of this module.
580int GetContainingWasmFunction(const WasmModule* module, uint32_t byte_offset);

582// Returns the function containing the given byte offset.
583// Will return preceding function if the byte offset is not
584// contained within a function.
585int GetNearestWasmFunction(const WasmModule* module, uint32_t byte_offset);

587// Gets the explicitly defined subtyping depth for the given type.
588// Returns 0 if the type has no explicit supertype.
589// The result is capped to {kV8MaxRttSubtypingDepth + 1}.
590// Invalid cyclic hierarchies will return -1.
591V8_EXPORT_PRIVATE int GetSubtypingDepth(const WasmModule* module,
                                      uint32_t type_index);

594// Interface to the storage (wire bytes) of a wasm module.
595// It is illegal for anyone receiving a ModuleWireBytes to store pointers based
596// on module_bytes, as this storage is only guaranteed to be alive as long as
597// this struct is alive.
598struct V8_EXPORT_PRIVATE ModuleWireBytes {
explicit ModuleWireBytes(base::Vector<const byte> module_bytes)
    : module_bytes_(module_bytes) {}
ModuleWireBytes(const byte* start, const byte* end)
    : module_bytes_(start, static_cast<int>(end - start)) {
  DCHECK_GE(kMaxInt, end - start)((void) 0);
}

// Get a string stored in the module bytes representing a name.
WasmName GetNameOrNull(WireBytesRef ref) const;

// Get a string stored in the module bytes representing a function name.
WasmName GetNameOrNull(const WasmFunction* function,
                       const WasmModule* module) const;

// Checks the given reference is contained within the module bytes.
bool BoundsCheck(WireBytesRef ref) const {
  uint32_t size = static_cast<uint32_t>(module_bytes_.length());
  return ref.offset() <= size && ref.length() <= size - ref.offset();
}

base::Vector<const byte> GetFunctionBytes(
    const WasmFunction* function) const {
  return module_bytes_.SubVector(function->code.offset(),
                                 function->code.end_offset());
}

base::Vector<const byte> module_bytes() const { return module_bytes_; }
const byte* start() const { return module_bytes_.begin(); }
const byte* end() const { return module_bytes_.end(); }
size_t length() const { return module_bytes_.length(); }

private:
base::Vector<const byte> module_bytes_;
632};

634// A helper for printing out the names of functions.
635struct WasmFunctionName {
WasmFunctionName(const WasmFunction* function, WasmName name)
    : function_(function), name_(name) {}

const WasmFunction* function_;
const WasmName name_;
641};

643std::ostream& operator<<(std::ostream& os, const WasmFunctionName& name);

645V8_EXPORT_PRIVATE bool IsWasmCodegenAllowed(Isolate* isolate,
                                          Handle<Context> context);

648Handle<JSObject> GetTypeForFunction(Isolate* isolate, const FunctionSig* sig,
                                  bool for_exception = false);
650Handle<JSObject> GetTypeForGlobal(Isolate* isolate, bool is_mutable,
                                ValueType type);
652Handle<JSObject> GetTypeForMemory(Isolate* isolate, uint32_t min_size,
                                base::Optional<uint32_t> max_size,
                                bool shared);
655Handle<JSObject> GetTypeForTable(Isolate* isolate, ValueType type,
                               uint32_t min_size,
                               base::Optional<uint32_t> max_size);
658Handle<JSArray> GetImports(Isolate* isolate, Handle<WasmModuleObject> module);
659Handle<JSArray> GetExports(Isolate* isolate, Handle<WasmModuleObject> module);
660Handle<JSArray> GetCustomSections(Isolate* isolate,
                                Handle<WasmModuleObject> module,
                                Handle<String> name, ErrorThrower* thrower);

664// Get the source position from a given function index and byte offset,
665// for either asm.js or pure Wasm modules.
666int GetSourcePosition(const WasmModule*, uint32_t func_index,
                    uint32_t byte_offset, bool is_at_number_conversion);

669// Translate function index to the index relative to the first declared (i.e.
670// non-imported) function.
671inline int declared_function_index(const WasmModule* module, int func_index) {
DCHECK_LE(module->num_imported_functions, func_index)((void) 0);
int declared_idx = func_index - module->num_imported_functions;
DCHECK_GT(module->num_declared_functions, declared_idx)((void) 0);
return declared_idx;
676}

678// TruncatedUserString makes it easy to output names up to a certain length, and
679// output a truncation followed by '...' if they exceed a limit.
680// Use like this:
681//   TruncatedUserString<> name (pc, len);
682//   printf("... %.*s ...", name.length(), name.start())
683template <int kMaxLen = 50>
684class TruncatedUserString {
static_assert(kMaxLen >= 4, "minimum length is 4 (length of '...' plus one)");

public:
template <typename T>
explicit TruncatedUserString(base::Vector<T> name)
    : TruncatedUserString(name.begin(), name.length()) {}

TruncatedUserString(const byte* start, size_t len)
    : TruncatedUserString(reinterpret_cast<const char*>(start), len) {}

TruncatedUserString(const char* start, size_t len)
    : start_(start), length_(std::min(kMaxLen, static_cast<int>(len))) {
  if (len > static_cast<size_t>(kMaxLen)) {
    memcpy(buffer_, start, kMaxLen - 3);
    memset(buffer_ + kMaxLen - 3, '.', 3);
    start_ = buffer_;
  }
}

const char* start() const { return start_; }

int length() const { return length_; }

private:
const char* start_;
const int length_;
char buffer_[kMaxLen];
712};

714// Print the signature into the given {buffer}, using {delimiter} as separator
715// between parameter types and return types. If {buffer} is non-empty, it will
716// be null-terminated, even if the signature is cut off. Returns the number of
717// characters written, excluding the terminating null-byte.
718size_t PrintSignature(base::Vector<char> buffer, const wasm::FunctionSig*,
                    char delimiter = ':');

721}  // namespace wasm
722}  // namespace internal
723}  // namespace v8

725#endif  // V8_WASM_WASM_MODULE_H_