chromium/testing/libfuzzer/fuzztest_wrapper.cpp

// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// A wrapper which knows to execute a given fuzzer within a fuzztest
// executable that contains multiple fuzzers.
// The fuzzer binary is assumed to be in the same directory as this binary.

#include <iostream>

#include "base/command_line.h"
#include "base/files/file_path.h"
#include "base/files/file_util.h"
#include "base/path_service.h"
#include "base/process/launch.h"
#include "base/strings/string_split.h"
#include "base/strings/stringprintf.h"
#include "base/strings/utf_string_conversions.h"
#include "testing/libfuzzer/fuzztest_wrapper_buildflags.h"

extern const char* kFuzzerBinary;
extern const char* kFuzzerArgs;

#if BUILDFLAG(USE_CENTIPEDE)

namespace {
void HandleReplayMode(auto& args) {
  // We're handling a centipede based fuzzer. If the last argument is a
  // filepath, we're trying to replay a testcase, since it doesn't make sense
  // to get a filepath when running with the centipede binary.
  if (args.size() <= 1) {
    return;
  }
  base::FilePath test_case(args.back());
  if (!base::PathExists(test_case)) {
    return;
  }

  auto env = base::Environment::Create();
#if BUILDFLAG(IS_WIN)
  auto env_value = base::WideToUTF8(args.back());
#else
  auto env_value = args.back();
#endif
  env->SetVar("FUZZTEST_REPLAY", env_value);
  env->UnSetVar("CENTIPEDE_RUNNER_FLAGS");
  std::cerr << "FuzzTest wrapper setting env var: FUZZTEST_REPLAY="
            << args.back() << '\n';

  // We must not add the testcase to the command line, as this will not be
  // parsed correctly by centipede.
  args.pop_back();
}
}  // namespace

#endif  // BUILDFLAG(USE_CENTIPEDE)

int main(int argc, const char* const* argv) { … }

#if defined(WIN32)
#define ALWAYS_EXPORT …
#else
#define ALWAYS_EXPORT …
#endif

ALWAYS_EXPORT extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data,
                                                    size_t size) { … }