tools/fuzz/fuzz.cpp

// Copyright (c) 2019 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include <cassert>
#include <cerrno>
#include <cstring>
#include <fstream>
#include <functional>
#include <random>
#include <sstream>
#include <string>

#include "source/fuzz/force_render_red.h"
#include "source/fuzz/fuzzer.h"
#include "source/fuzz/fuzzer_util.h"
#include "source/fuzz/protobufs/spirvfuzz_protobufs.h"
#include "source/fuzz/replayer.h"
#include "source/fuzz/shrinker.h"
#include "source/opt/build_module.h"
#include "source/opt/ir_context.h"
#include "source/opt/log.h"
#include "source/spirv_fuzzer_options.h"
#include "source/util/string_utils.h"
#include "tools/io.h"
#include "tools/util/cli_consumer.h"

namespace {

// Check that the std::system function can actually be used.
bool CheckExecuteCommand() {
  int res = std::system(nullptr);
  return res != 0;
}

// Execute a command using the shell.
// Returns true if and only if the command's exit status was 0.
bool ExecuteCommand(const std::string& command) {
  errno = 0;
  int status = std::system(command.c_str());
  assert(errno == 0 && "failed to execute command");
  // The result returned by 'system' is implementation-defined, but is
  // usually the case that the returned value is 0 when the command's exit
  // code was 0.  We are assuming that here, and that's all we depend on.
  return status == 0;
}

// Status and actions to perform after parsing command-line arguments.
enum class FuzzActions {
  FORCE_RENDER_RED,  // Turn the shader into a form such that it is guaranteed
                     // to render a red image.
  FUZZ,    // Run the fuzzer to apply transformations in a randomized fashion.
  REPLAY,  // Replay an existing sequence of transformations.
  SHRINK,  // Shrink an existing sequence of transformations with respect to an
           // interestingness function.
  STOP     // Do nothing.
};

struct FuzzStatus {
  FuzzActions action;
  int code;
};

void PrintUsage(const char* program) {
  // NOTE: Please maintain flags in lexicographical order.
  printf(
      R"(%s - Fuzzes an equivalent SPIR-V binary based on a given binary.

USAGE: %s [options] <input.spv> -o <output.spv> \
  --donors=<donors.txt>
USAGE: %s [options] <input.spv> -o <output.spv> \
  --shrink=<input.transformations> -- <interestingness_test> [args...]

The SPIR-V binary is read from <input.spv>.  If <input.facts> is also present,
facts about the SPIR-V binary are read from this file.

The transformed SPIR-V binary is written to <output.spv>.  Human-readable and
binary representations of the transformations that were applied are written to
<output.transformations_json> and <output.transformations>, respectively.

When passing --shrink=<input.transformations> an <interestingness_test>
must also be provided; this is the path to a script that returns 0 if and only
if a given SPIR-V binary is interesting.  The SPIR-V binary will be passed to
the script as an argument after any other provided arguments [args...].  The
"--" characters are optional but denote that all arguments that follow are
positional arguments and thus will be forwarded to the interestingness script,
and not parsed by %s.

NOTE: The fuzzer is a work in progress.

Options (in lexicographical order):

  -h, --help
               Print this help.
  --donors=
               File specifying a series of donor files, one per line.  Must be
               provided if the tool is invoked in fuzzing mode; incompatible
               with replay and shrink modes.  The file should be empty if no
               donors are to be used.
  --force-render-red
               Transforms the input shader into a shader that writes red to the
               output buffer, and then captures the original shader as the body
               of a conditional with a dynamically false guard.  Exploits input
               facts to make the guard non-obviously false.  This option is a
               helper for massaging crash-inducing tests into a runnable
               format; it does not perform any fuzzing.
  --fuzzer-pass-validation
               Run the validator after applying each fuzzer pass during
               fuzzing.  Aborts fuzzing early if an invalid binary is created.
               Useful for debugging spirv-fuzz.
  --replay
               File from which to read a sequence of transformations to replay
               (instead of fuzzing)
  --seed=
               Unsigned 32-bit integer seed to control random number
               generation.
  --shrink=
               File from which to read a sequence of transformations to shrink
               (instead of fuzzing)
  --shrinker-step-limit=
               Unsigned 32-bit integer specifying maximum number of steps the
               shrinker will take before giving up.  Ignored unless --shrink
               is used.
  --shrinker-temp-file-prefix=
               Specifies a temporary file prefix that will be used to output
               temporary shader files during shrinking.  A number and .spv
               extension will be added.  The default is "temp_", which will
               cause files like "temp_0001.spv" to be output to the current
               directory.  Ignored unless --shrink is used.
  --replay-validation
               Run the validator after applying each transformation during
               replay (including the replay that occurs during shrinking).
               Aborts if an invalid binary is created.  Useful for debugging
               spirv-fuzz.
  --version
               Display fuzzer version information.

Supported validator options are as follows. See `spirv-val --help` for details.
  --before-hlsl-legalization
  --relax-block-layout
  --relax-logical-pointer
  --relax-struct-store
  --scalar-block-layout
  --skip-block-layout
)",
      program, program, program, program);
}

// Message consumer for this tool.  Used to emit diagnostics during
// initialization and setup. Note that |source| and |position| are irrelevant
// here because we are still not processing a SPIR-V input file.
void FuzzDiagnostic(spv_message_level_t level, const char* /*source*/,
                    const spv_position_t& /*position*/, const char* message) {
  if (level == SPV_MSG_ERROR) {
    fprintf(stderr, "error: ");
  }
  fprintf(stderr, "%s\n", message);
}

FuzzStatus ParseFlags(int argc, const char** argv, std::string* in_binary_file,
                      std::string* out_binary_file, std::string* donors_file,
                      std::string* replay_transformations_file,
                      std::vector<std::string>* interestingness_test,
                      std::string* shrink_transformations_file,
                      std::string* shrink_temp_file_prefix,
                      spvtools::FuzzerOptions* fuzzer_options,
                      spvtools::ValidatorOptions* validator_options) {
  uint32_t positional_arg_index = 0;
  bool only_positional_arguments_remain = false;
  bool force_render_red = false;

  for (int argi = 1; argi < argc; ++argi) {
    const char* cur_arg = argv[argi];
    if ('-' == cur_arg[0] && !only_positional_arguments_remain) {
      if (0 == strcmp(cur_arg, "--version")) {
        spvtools::Logf(FuzzDiagnostic, SPV_MSG_INFO, nullptr, {}, "%s\n",
                       spvSoftwareVersionDetailsString());
        return {FuzzActions::STOP, 0};
      } else if (0 == strcmp(cur_arg, "--help") || 0 == strcmp(cur_arg, "-h")) {
        PrintUsage(argv[0]);
        return {FuzzActions::STOP, 0};
      } else if (0 == strcmp(cur_arg, "-o")) {
        if (out_binary_file->empty() && argi + 1 < argc) {
          *out_binary_file = std::string(argv[++argi]);
        } else {
          PrintUsage(argv[0]);
          return {FuzzActions::STOP, 1};
        }
      } else if (0 == strncmp(cur_arg, "--donors=", sizeof("--donors=") - 1)) {
        const auto split_flag = spvtools::utils::SplitFlagArgs(cur_arg);
        *donors_file = std::string(split_flag.second);
      } else if (0 == strncmp(cur_arg, "--force-render-red",
                              sizeof("--force-render-red") - 1)) {
        force_render_red = true;
      } else if (0 == strncmp(cur_arg, "--fuzzer-pass-validation",
                              sizeof("--fuzzer-pass-validation") - 1)) {
        fuzzer_options->enable_fuzzer_pass_validation();
      } else if (0 == strncmp(cur_arg, "--replay=", sizeof("--replay=") - 1)) {
        const auto split_flag = spvtools::utils::SplitFlagArgs(cur_arg);
        *replay_transformations_file = std::string(split_flag.second);
      } else if (0 == strncmp(cur_arg, "--replay-validation",
                              sizeof("--replay-validation") - 1)) {
        fuzzer_options->enable_replay_validation();
      } else if (0 == strncmp(cur_arg, "--shrink=", sizeof("--shrink=") - 1)) {
        const auto split_flag = spvtools::utils::SplitFlagArgs(cur_arg);
        *shrink_transformations_file = std::string(split_flag.second);
      } else if (0 == strncmp(cur_arg, "--seed=", sizeof("--seed=") - 1)) {
        const auto split_flag = spvtools::utils::SplitFlagArgs(cur_arg);
        char* end = nullptr;
        errno = 0;
        const auto seed =
            static_cast<uint32_t>(strtol(split_flag.second.c_str(), &end, 10));
        assert(end != split_flag.second.c_str() && errno == 0);
        fuzzer_options->set_random_seed(seed);
      } else if (0 == strncmp(cur_arg, "--shrinker-step-limit=",
                              sizeof("--shrinker-step-limit=") - 1)) {
        const auto split_flag = spvtools::utils::SplitFlagArgs(cur_arg);
        char* end = nullptr;
        errno = 0;
        const auto step_limit =
            static_cast<uint32_t>(strtol(split_flag.second.c_str(), &end, 10));
        assert(end != split_flag.second.c_str() && errno == 0);
        fuzzer_options->set_shrinker_step_limit(step_limit);
      } else if (0 == strncmp(cur_arg, "--shrinker-temp-file-prefix=",
                              sizeof("--shrinker-temp-file-prefix=") - 1)) {
        const auto split_flag = spvtools::utils::SplitFlagArgs(cur_arg);
        *shrink_temp_file_prefix = std::string(split_flag.second);
      } else if (0 == strcmp(cur_arg, "--before-hlsl-legalization")) {
        validator_options->SetBeforeHlslLegalization(true);
      } else if (0 == strcmp(cur_arg, "--relax-logical-pointer")) {
        validator_options->SetRelaxLogicalPointer(true);
      } else if (0 == strcmp(cur_arg, "--relax-block-layout")) {
        validator_options->SetRelaxBlockLayout(true);
      } else if (0 == strcmp(cur_arg, "--scalar-block-layout")) {
        validator_options->SetScalarBlockLayout(true);
      } else if (0 == strcmp(cur_arg, "--skip-block-layout")) {
        validator_options->SetSkipBlockLayout(true);
      } else if (0 == strcmp(cur_arg, "--relax-struct-store")) {
        validator_options->SetRelaxStructStore(true);
      } else if (0 == strcmp(cur_arg, "--")) {
        only_positional_arguments_remain = true;
      } else {
        std::stringstream ss;
        ss << "Unrecognized argument: " << cur_arg << std::endl;
        spvtools::Error(FuzzDiagnostic, nullptr, {}, ss.str().c_str());
        PrintUsage(argv[0]);
        return {FuzzActions::STOP, 1};
      }
    } else if (positional_arg_index == 0) {
      // Binary input file name
      assert(in_binary_file->empty());
      *in_binary_file = std::string(cur_arg);
      positional_arg_index++;
    } else {
      interestingness_test->push_back(std::string(cur_arg));
    }
  }

  if (in_binary_file->empty()) {
    spvtools::Error(FuzzDiagnostic, nullptr, {}, "No input file specified");
    return {FuzzActions::STOP, 1};
  }

  if (out_binary_file->empty()) {
    spvtools::Error(FuzzDiagnostic, nullptr, {}, "-o required");
    return {FuzzActions::STOP, 1};
  }

  auto const_fuzzer_options =
      static_cast<spv_const_fuzzer_options>(*fuzzer_options);
  if (force_render_red) {
    if (!replay_transformations_file->empty() ||
        !shrink_transformations_file->empty() ||
        const_fuzzer_options->replay_validation_enabled) {
      spvtools::Error(FuzzDiagnostic, nullptr, {},
                      "The --force-render-red argument cannot be used with any "
                      "other arguments except -o.");
      return {FuzzActions::STOP, 1};
    }
    return {FuzzActions::FORCE_RENDER_RED, 0};
  }

  if (replay_transformations_file->empty() &&
      shrink_transformations_file->empty() &&
      static_cast<spv_const_fuzzer_options>(*fuzzer_options)
          ->replay_validation_enabled) {
    spvtools::Error(FuzzDiagnostic, nullptr, {},
                    "The --replay-validation argument can only be used with "
                    "one of the --replay or --shrink arguments.");
    return {FuzzActions::STOP, 1};
  }

  if (shrink_transformations_file->empty() && !interestingness_test->empty()) {
    spvtools::Error(FuzzDiagnostic, nullptr, {},
                    "Too many positional arguments specified; extra positional "
                    "arguments are used as the interestingness function, which "
                    "are only valid with the --shrink option.");
    return {FuzzActions::STOP, 1};
  }

  if (!shrink_transformations_file->empty() && interestingness_test->empty()) {
    spvtools::Error(
        FuzzDiagnostic, nullptr, {},
        "The --shrink option requires an interestingness function.");
    return {FuzzActions::STOP, 1};
  }

  if (!replay_transformations_file->empty() ||
      !shrink_transformations_file->empty()) {
    // Donors should not be provided when replaying or shrinking: they only make
    // sense during fuzzing.
    if (!donors_file->empty()) {
      spvtools::Error(FuzzDiagnostic, nullptr, {},
                      "The --donors argument is not compatible with --replay "
                      "nor --shrink.");
      return {FuzzActions::STOP, 1};
    }
  }

  if (!replay_transformations_file->empty()) {
    // A replay transformations file was given, thus the tool is being invoked
    // in replay mode.
    if (!shrink_transformations_file->empty()) {
      spvtools::Error(
          FuzzDiagnostic, nullptr, {},
          "The --replay and --shrink arguments are mutually exclusive.");
      return {FuzzActions::STOP, 1};
    }
    return {FuzzActions::REPLAY, 0};
  }

  if (!shrink_transformations_file->empty()) {
    // The tool is being invoked in shrink mode.
    assert(!interestingness_test->empty() &&
           "An error should have been raised if --shrink was provided without "
           "an interestingness test.");
    return {FuzzActions::SHRINK, 0};
  }

  // The tool is being invoked in fuzz mode.
  if (donors_file->empty()) {
    spvtools::Error(FuzzDiagnostic, nullptr, {},
                    "Fuzzing requires that the --donors option is used.");
    return {FuzzActions::STOP, 1};
  }
  return {FuzzActions::FUZZ, 0};
}

bool ParseTransformations(
    const std::string& transformations_file,
    spvtools::fuzz::protobufs::TransformationSequence* transformations) {
  std::ifstream transformations_stream;
  transformations_stream.open(transformations_file,
                              std::ios::in | std::ios::binary);
  auto parse_success =
      transformations->ParseFromIstream(&transformations_stream);
  transformations_stream.close();
  if (!parse_success) {
    spvtools::Error(FuzzDiagnostic, nullptr, {},
                    ("Error reading transformations from file '" +
                     transformations_file + "'")
                        .c_str());
    return false;
  }
  return true;
}

bool Replay(const spv_target_env& target_env,
            spv_const_fuzzer_options fuzzer_options,
            spv_validator_options validator_options,
            const std::vector<uint32_t>& binary_in,
            const spvtools::fuzz::protobufs::FactSequence& initial_facts,
            const std::string& replay_transformations_file,
            std::vector<uint32_t>* binary_out,
            spvtools::fuzz::protobufs::TransformationSequence*
                transformations_applied) {
  spvtools::fuzz::protobufs::TransformationSequence transformation_sequence;
  if (!ParseTransformations(replay_transformations_file,
                            &transformation_sequence)) {
    return false;
  }
  spvtools::fuzz::Replayer replayer(
      target_env, fuzzer_options->replay_validation_enabled, validator_options);
  replayer.SetMessageConsumer(spvtools::utils::CLIMessageConsumer);
  auto replay_result_status =
      replayer.Run(binary_in, initial_facts, transformation_sequence,
                   binary_out, transformations_applied);
  return !(replay_result_status !=
           spvtools::fuzz::Replayer::ReplayerResultStatus::kComplete);
}

bool Shrink(const spv_target_env& target_env,
            spv_const_fuzzer_options fuzzer_options,
            spv_validator_options validator_options,
            const std::vector<uint32_t>& binary_in,
            const spvtools::fuzz::protobufs::FactSequence& initial_facts,
            const std::string& shrink_transformations_file,
            const std::string& shrink_temp_file_prefix,
            const std::vector<std::string>& interestingness_command,
            std::vector<uint32_t>* binary_out,
            spvtools::fuzz::protobufs::TransformationSequence*
                transformations_applied) {
  spvtools::fuzz::protobufs::TransformationSequence transformation_sequence;
  if (!ParseTransformations(shrink_transformations_file,
                            &transformation_sequence)) {
    return false;
  }
  spvtools::fuzz::Shrinker shrinker(
      target_env, fuzzer_options->shrinker_step_limit,
      fuzzer_options->replay_validation_enabled, validator_options);
  shrinker.SetMessageConsumer(spvtools::utils::CLIMessageConsumer);

  assert(!interestingness_command.empty() &&
         "An error should have been raised because the interestingness_command "
         "is empty.");
  std::stringstream joined;
  joined << interestingness_command[0];
  for (size_t i = 1, size = interestingness_command.size(); i < size; ++i) {
    joined << " " << interestingness_command[i];
  }
  std::string interestingness_command_joined = joined.str();

  spvtools::fuzz::Shrinker::InterestingnessFunction interestingness_function =
      [interestingness_command_joined, shrink_temp_file_prefix](
          std::vector<uint32_t> binary, uint32_t reductions_applied) -> bool {
    std::stringstream ss;
    ss << shrink_temp_file_prefix << std::setw(4) << std::setfill('0')
       << reductions_applied << ".spv";
    const auto spv_file = ss.str();
    const std::string command = interestingness_command_joined + " " + spv_file;
    auto write_file_succeeded =
        WriteFile(spv_file.c_str(), "wb", &binary[0], binary.size());
    (void)(write_file_succeeded);
    assert(write_file_succeeded);
    return ExecuteCommand(command);
  };

  auto shrink_result_status = shrinker.Run(
      binary_in, initial_facts, transformation_sequence,
      interestingness_function, binary_out, transformations_applied);
  return spvtools::fuzz::Shrinker::ShrinkerResultStatus::kComplete ==
             shrink_result_status ||
         spvtools::fuzz::Shrinker::ShrinkerResultStatus::kStepLimitReached ==
             shrink_result_status;
}

bool Fuzz(const spv_target_env& target_env,
          spv_const_fuzzer_options fuzzer_options,
          spv_validator_options validator_options,
          const std::vector<uint32_t>& binary_in,
          const spvtools::fuzz::protobufs::FactSequence& initial_facts,
          const std::string& donors, std::vector<uint32_t>* binary_out,
          spvtools::fuzz::protobufs::TransformationSequence*
              transformations_applied) {
  auto message_consumer = spvtools::utils::CLIMessageConsumer;

  std::vector<spvtools::fuzz::fuzzerutil::ModuleSupplier> donor_suppliers;

  std::ifstream donors_file(donors);
  if (!donors_file) {
    spvtools::Error(FuzzDiagnostic, nullptr, {}, "Error opening donors file");
    return false;
  }
  std::string donor_filename;
  while (std::getline(donors_file, donor_filename)) {
    donor_suppliers.emplace_back(
        [donor_filename, message_consumer,
         target_env]() -> std::unique_ptr<spvtools::opt::IRContext> {
          std::vector<uint32_t> donor_binary;
          if (!ReadFile<uint32_t>(donor_filename.c_str(), "rb",
                                  &donor_binary)) {
            return nullptr;
          }
          return spvtools::BuildModule(target_env, message_consumer,
                                       donor_binary.data(),
                                       donor_binary.size());
        });
  }

  spvtools::fuzz::Fuzzer fuzzer(
      target_env,
      fuzzer_options->has_random_seed
          ? fuzzer_options->random_seed
          : static_cast<uint32_t>(std::random_device()()),
      fuzzer_options->fuzzer_pass_validation_enabled, validator_options);
  fuzzer.SetMessageConsumer(message_consumer);
  auto fuzz_result_status =
      fuzzer.Run(binary_in, initial_facts, donor_suppliers, binary_out,
                 transformations_applied);
  if (fuzz_result_status !=
      spvtools::fuzz::Fuzzer::FuzzerResultStatus::kComplete) {
    spvtools::Error(FuzzDiagnostic, nullptr, {}, "Error running fuzzer");
    return false;
  }
  return true;
}

}  // namespace

// Dumps |binary| to file |filename|. Useful for interactive debugging.
void DumpShader(const std::vector<uint32_t>& binary, const char* filename) {
  auto write_file_succeeded =
      WriteFile(filename, "wb", &binary[0], binary.size());
  if (!write_file_succeeded) {
    std::cerr << "Failed to dump shader" << std::endl;
  }
}

// Dumps the SPIRV-V module in |context| to file |filename|. Useful for
// interactive debugging.
void DumpShader(spvtools::opt::IRContext* context, const char* filename) {
  std::vector<uint32_t> binary;
  context->module()->ToBinary(&binary, false);
  DumpShader(binary, filename);
}

const auto kDefaultEnvironment = SPV_ENV_UNIVERSAL_1_3;

int main(int argc, const char** argv) {
  std::string in_binary_file;
  std::string out_binary_file;
  std::string donors_file;
  std::string replay_transformations_file;
  std::vector<std::string> interestingness_test;
  std::string shrink_transformations_file;
  std::string shrink_temp_file_prefix = "temp_";

  spvtools::FuzzerOptions fuzzer_options;
  spvtools::ValidatorOptions validator_options;

  FuzzStatus status =
      ParseFlags(argc, argv, &in_binary_file, &out_binary_file, &donors_file,
                 &replay_transformations_file, &interestingness_test,
                 &shrink_transformations_file, &shrink_temp_file_prefix,
                 &fuzzer_options, &validator_options);

  if (status.action == FuzzActions::STOP) {
    return status.code;
  }

  std::vector<uint32_t> binary_in;
  if (!ReadFile<uint32_t>(in_binary_file.c_str(), "rb", &binary_in)) {
    return 1;
  }

  spvtools::fuzz::protobufs::FactSequence initial_facts;

  // If not found, dot_pos will be std::string::npos, which can be used in
  // substr to mean "the end of the string"; there is no need to check the
  // result.
  size_t dot_pos = in_binary_file.rfind('.');
  std::string in_facts_file = in_binary_file.substr(0, dot_pos) + ".facts";
  std::ifstream facts_input(in_facts_file);
  if (facts_input) {
    std::string facts_json_string((std::istreambuf_iterator<char>(facts_input)),
                                  std::istreambuf_iterator<char>());
    facts_input.close();
    if (google::protobuf::util::Status::OK !=
        google::protobuf::util::JsonStringToMessage(facts_json_string,
                                                    &initial_facts)) {
      spvtools::Error(FuzzDiagnostic, nullptr, {}, "Error reading facts data");
      return 1;
    }
  }

  std::vector<uint32_t> binary_out;
  spvtools::fuzz::protobufs::TransformationSequence transformations_applied;

  spv_target_env target_env = kDefaultEnvironment;

  switch (status.action) {
    case FuzzActions::FORCE_RENDER_RED:
      if (!spvtools::fuzz::ForceRenderRed(target_env, validator_options,
                                          binary_in, initial_facts,
                                          &binary_out)) {
        return 1;
      }
      break;
    case FuzzActions::FUZZ:
      if (!Fuzz(target_env, fuzzer_options, validator_options, binary_in,
                initial_facts, donors_file, &binary_out,
                &transformations_applied)) {
        return 1;
      }
      break;
    case FuzzActions::REPLAY:
      if (!Replay(target_env, fuzzer_options, validator_options, binary_in,
                  initial_facts, replay_transformations_file, &binary_out,
                  &transformations_applied)) {
        return 1;
      }
      break;
    case FuzzActions::SHRINK: {
      if (!CheckExecuteCommand()) {
        std::cerr << "could not find shell interpreter for executing a command"
                  << std::endl;
        return 1;
      }
      if (!Shrink(target_env, fuzzer_options, validator_options, binary_in,
                  initial_facts, shrink_transformations_file,
                  shrink_temp_file_prefix, interestingness_test, &binary_out,
                  &transformations_applied)) {
        return 1;
      }
    } break;
    default:
      assert(false && "Unknown fuzzer action.");
      break;
  }

  if (!WriteFile<uint32_t>(out_binary_file.c_str(), "wb", binary_out.data(),
                           binary_out.size())) {
    spvtools::Error(FuzzDiagnostic, nullptr, {}, "Error writing out binary");
    return 1;
  }

  if (status.action != FuzzActions::FORCE_RENDER_RED) {
    // If not found, dot_pos will be std::string::npos, which can be used in
    // substr to mean "the end of the string"; there is no need to check the
    // result.
    dot_pos = out_binary_file.rfind('.');
    std::string output_file_prefix = out_binary_file.substr(0, dot_pos);
    std::ofstream transformations_file;
    transformations_file.open(output_file_prefix + ".transformations",
                              std::ios::out | std::ios::binary);
    bool success =
        transformations_applied.SerializeToOstream(&transformations_file);
    transformations_file.close();
    if (!success) {
      spvtools::Error(FuzzDiagnostic, nullptr, {},
                      "Error writing out transformations binary");
      return 1;
    }

    std::string json_string;
    auto json_options = google::protobuf::util::JsonOptions();
    json_options.add_whitespace = true;
    auto json_generation_status = google::protobuf::util::MessageToJsonString(
        transformations_applied, &json_string, json_options);
    if (json_generation_status != google::protobuf::util::Status::OK) {
      spvtools::Error(FuzzDiagnostic, nullptr, {},
                      "Error writing out transformations in JSON format");
      return 1;
    }

    std::ofstream transformations_json_file(output_file_prefix +
                                            ".transformations_json");
    transformations_json_file << json_string;
    transformations_json_file.close();
  }

  return 0;
}