scripts/monitor_fuzz.py - external/github.com/WebAssembly/binaryen - Git at Google

 #!/usr/bin/env python3

 # Copyright 2026 WebAssembly Community Group participants
 #
 # 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.

 """Run and monitor the Binaryen fuzzer (fuzz_opt.py).

 Monitors progress, manages log file truncation, stops at iteration limits,
 and reports bugs found.
 """

 import argparse
 import collections
 import os
 import re
 import signal
 import subprocess
 import sys
 import threading
 import time


 class FuzzMonitor:
     """Monitors fuzzer output stream, manages log files, and tracks state."""

     def __init__(self, log_path, max_lines, keep_lines, truncate_interval):
         self.log_path = log_path
         self.max_lines = max_lines
         self.keep_lines = keep_lines
         self.truncate_interval = truncate_interval

         self.lock = threading.Lock()
         self.latest_iteration = 0
         self.latest_seed = 'unknown'
         self.bug_found = False
         self.recent_lines = collections.deque(maxlen=20)

         self.deque = collections.deque(maxlen=keep_lines)
         self.lines_written = 0

         if os.path.isfile(log_path):
             try:
                 with open(log_path, encoding='utf-8', errors='replace') as f:
                     for line in f:
                         self.deque.append(line)
                         self.recent_lines.append(line)
                         self.lines_written += 1
                         self._parse_line(line)
             except Exception:
                 pass

     def _parse_line(self, line):
         iter_match = re.search(r'ITERATION:\s*(\d+)', line)
         if iter_match:
             self.latest_iteration = int(iter_match.group(1))

         seed_match = re.search(r'seed:\s*(\d+)', line)
         if seed_match:
             self.latest_seed = seed_match.group(1)

         if re.search(r'You found a bug', line, re.IGNORECASE):
             self.bug_found = True

     def run(self, stdout_stream):
         last_truncate = time.time()
         try:
             with open(self.log_path, 'a', encoding='utf-8') as f:
                 for line in stdout_stream:
                     with self.lock:
                         self._parse_line(line)
                         self.deque.append(line)
                         self.recent_lines.append(line)
                         self.lines_written += 1

                     f.write(line)
                     f.flush()

                     now = time.time()
                     if (
                         self.lines_written >= self.max_lines
                         and (now - last_truncate) >= self.truncate_interval
                     ):
                         f.close()
                         with open(self.log_path, 'w', encoding='utf-8') as wf:
                             with self.lock:
                                 wf.writelines(self.deque)
                                 self.lines_written = len(self.deque)
                         f = open(self.log_path, 'a', encoding='utf-8')
                         last_truncate = now
         except Exception as e:
             print(f'Error writing to log file: {e}', file=sys.stderr)

     def get_progress(self):
         with self.lock:
             return self.latest_iteration

     def get_status(self):
         with self.lock:
             return (
                 self.bug_found,
                 self.latest_iteration,
                 self.latest_seed,
                 list(self.recent_lines),
             )


 def parse_args():
     default_log_dir = os.path.join(
         os.path.dirname(os.path.abspath(__file__)), 'out', 'test')
     parser = argparse.ArgumentParser(description=__doc__)
     parser.add_argument(
         '--log-dir',
         default=os.environ.get('LOG_DIR', default_log_dir),
         help='Directory to save fuzz.log (default: $LOG_DIR or ./out/test)',
     )
     parser.add_argument(
         '--max-iters',
         type=int,
         default=int(os.environ.get('MAX_ITERS', '0')),
         help='Stop after N iterations (0 for infinite, default: $MAX_ITERS or 0)',
     )
     parser.add_argument(
         '--truncate-interval',
         type=float,
         default=30.0,
         help='Seconds between log truncation checks (default: 30)',
     )
     parser.add_argument(
         '--max-lines',
         type=int,
         default=10000,
         help='Maximum lines in log before truncation (default: 10000)',
     )
     parser.add_argument(
         '--keep-lines',
         type=int,
         default=5000,
         help='Lines to keep when truncating (default: 5000)',
     )
     parser.add_argument(
         'cmd',
         nargs=argparse.REMAINDER,
         help='Fuzzer command to run (default: ./scripts/fuzz_opt.py)',
     )
     return parser.parse_args()


 def main():
     args = parse_args()

     cmd = list(args.cmd)
     if cmd and cmd[0] == '--':
         cmd.pop(0)
     if not cmd:
         default_fuzzer = os.path.join(
             os.path.dirname(os.path.abspath(__file__)), 'fuzz_opt.py',
         )
         cmd = [sys.executable, default_fuzzer]

     os.makedirs(args.log_dir, exist_ok=True)
     log_file_path = os.path.join(args.log_dir, 'fuzz.log')

     monitor = FuzzMonitor(
         log_path=log_file_path,
         max_lines=args.max_lines,
         keep_lines=args.keep_lines,
         truncate_interval=args.truncate_interval,
     )

     env = os.environ.copy()
     env['PYTHONUNBUFFERED'] = '1'

     proc = subprocess.Popen(
         cmd,
         stdout=subprocess.PIPE,
         stderr=subprocess.STDOUT,
         text=True,
         bufsize=1,
         env=env,
         errors='replace',
         start_new_session=True,
     )

     print(f'Fuzzer started with PID {proc.pid}. Monitoring...', flush=True)

     reader_thread = threading.Thread(
         target=monitor.run,
         args=(proc.stdout,),
         daemon=True,
     )
     reader_thread.start()

     def stop_child():
         if proc.poll() is None:
             try:
                 os.killpg(proc.pid, signal.SIGTERM)
             except ProcessLookupError:
                 pass
             try:
                 proc.wait(timeout=5)
             except subprocess.TimeoutExpired:
                 try:
                     os.killpg(proc.pid, signal.SIGKILL)
                 except ProcessLookupError:
                     pass
                 proc.wait()

     def signal_handler(signum, _frame):
         stop_child()
         reader_thread.join(timeout=2.0)
         sys.exit(128 + signum)

     signal.signal(signal.SIGINT, signal_handler)
     signal.signal(signal.SIGTERM, signal_handler)

     start_time = time.time()
     last_report = 0
     limit_reached = False

     try:
         while reader_thread.is_alive() or proc.poll() is None:
             reader_thread.join(timeout=1.0)
             now = time.time()
             elapsed = int(now - start_time)

             minute = elapsed // 60
             latest_iter = monitor.get_progress()

             if minute > last_report:
                 last_report = minute
                 timestamp = time.strftime('%H:%M:%S')
                 print(
                     f'[{timestamp}] Runtime: {last_report} min, Latest'
                     f' Iteration: {latest_iter}',
                     flush=True,
                 )

             if args.max_iters > 0 and latest_iter >= args.max_iters:
                 print(
                     f'Reached max iterations ({args.max_iters}). Stopping'
                     ' fuzzer...',
                     flush=True,
                 )
                 limit_reached = True
                 stop_child()
                 break
     finally:
         stop_child()
         reader_thread.join(timeout=5.0)

     exit_code = proc.returncode

     if limit_reached:
         print(
             f'SUCCESS: Reached max iterations ({args.max_iters}) without finding'
             ' a bug.',
         )
         return 0

     bug_found, iteration, seed, recent_lines = monitor.get_status()

     if bug_found:
         print('SUCCESS: Bug found!')
         print(f'Iteration: {iteration}')
         print(f'Seed: {seed}')
         print(f'Exit code: {exit_code}')
         return 0

     print('FAILURE: Fuzzer stopped unexpectedly without finding a bug.')
     print(f'Exit code: {exit_code}')
     if recent_lines:
         print('Last 20 lines of log:')
         for line in recent_lines:
             print(line.rstrip('\r\n'))
     return 1


 if __name__ == '__main__':
     sys.exit(main())
	#!/usr/bin/env python3

	# Copyright 2026 WebAssembly Community Group participants
	#
	# 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.

	"""Run and monitor the Binaryen fuzzer (fuzz_opt.py).

	Monitors progress, manages log file truncation, stops at iteration limits,
	and reports bugs found.
	"""

	import argparse
	import collections
	import os
	import re
	import signal
	import subprocess
	import sys
	import threading
	import time


	class FuzzMonitor:
	"""Monitors fuzzer output stream, manages log files, and tracks state."""

	def __init__(self, log_path, max_lines, keep_lines, truncate_interval):
	self.log_path = log_path
	self.max_lines = max_lines
	self.keep_lines = keep_lines
	self.truncate_interval = truncate_interval

	self.lock = threading.Lock()
	self.latest_iteration = 0
	self.latest_seed = 'unknown'
	self.bug_found = False
	self.recent_lines = collections.deque(maxlen=20)

	self.deque = collections.deque(maxlen=keep_lines)
	self.lines_written = 0

	if os.path.isfile(log_path):
	try:
	with open(log_path, encoding='utf-8', errors='replace') as f:
	for line in f:
	self.deque.append(line)
	self.recent_lines.append(line)
	self.lines_written += 1
	self._parse_line(line)
	except Exception:
	pass

	def _parse_line(self, line):
	iter_match = re.search(r'ITERATION:\s*(\d+)', line)
	if iter_match:
	self.latest_iteration = int(iter_match.group(1))

	seed_match = re.search(r'seed:\s*(\d+)', line)
	if seed_match:
	self.latest_seed = seed_match.group(1)

	if re.search(r'You found a bug', line, re.IGNORECASE):
	self.bug_found = True

	def run(self, stdout_stream):
	last_truncate = time.time()
	try:
	with open(self.log_path, 'a', encoding='utf-8') as f:
	for line in stdout_stream:
	with self.lock:
	self._parse_line(line)
	self.deque.append(line)
	self.recent_lines.append(line)
	self.lines_written += 1

	f.write(line)
	f.flush()

	now = time.time()
	if (
	self.lines_written >= self.max_lines
	and (now - last_truncate) >= self.truncate_interval
	):
	f.close()
	with open(self.log_path, 'w', encoding='utf-8') as wf:
	with self.lock:
	wf.writelines(self.deque)
	self.lines_written = len(self.deque)
	f = open(self.log_path, 'a', encoding='utf-8')
	last_truncate = now
	except Exception as e:
	print(f'Error writing to log file: {e}', file=sys.stderr)

	def get_progress(self):
	with self.lock:
	return self.latest_iteration

	def get_status(self):
	with self.lock:
	return (
	self.bug_found,
	self.latest_iteration,
	self.latest_seed,
	list(self.recent_lines),
	)


	def parse_args():
	default_log_dir = os.path.join(
	os.path.dirname(os.path.abspath(__file__)), 'out', 'test')
	parser = argparse.ArgumentParser(description=__doc__)
	parser.add_argument(
	'--log-dir',
	default=os.environ.get('LOG_DIR', default_log_dir),
	help='Directory to save fuzz.log (default: $LOG_DIR or ./out/test)',
	)
	parser.add_argument(
	'--max-iters',
	type=int,
	default=int(os.environ.get('MAX_ITERS', '0')),
	help='Stop after N iterations (0 for infinite, default: $MAX_ITERS or 0)',
	)
	parser.add_argument(
	'--truncate-interval',
	type=float,
	default=30.0,
	help='Seconds between log truncation checks (default: 30)',
	)
	parser.add_argument(
	'--max-lines',
	type=int,
	default=10000,
	help='Maximum lines in log before truncation (default: 10000)',
	)
	parser.add_argument(
	'--keep-lines',
	type=int,
	default=5000,
	help='Lines to keep when truncating (default: 5000)',
	)
	parser.add_argument(
	'cmd',
	nargs=argparse.REMAINDER,
	help='Fuzzer command to run (default: ./scripts/fuzz_opt.py)',
	)
	return parser.parse_args()


	def main():
	args = parse_args()

	cmd = list(args.cmd)
	if cmd and cmd[0] == '--':
	cmd.pop(0)
	if not cmd:
	default_fuzzer = os.path.join(
	os.path.dirname(os.path.abspath(__file__)), 'fuzz_opt.py',
	)
	cmd = [sys.executable, default_fuzzer]

	os.makedirs(args.log_dir, exist_ok=True)
	log_file_path = os.path.join(args.log_dir, 'fuzz.log')

	monitor = FuzzMonitor(
	log_path=log_file_path,
	max_lines=args.max_lines,
	keep_lines=args.keep_lines,
	truncate_interval=args.truncate_interval,
	)

	env = os.environ.copy()
	env['PYTHONUNBUFFERED'] = '1'

	proc = subprocess.Popen(
	cmd,
	stdout=subprocess.PIPE,
	stderr=subprocess.STDOUT,
	text=True,
	bufsize=1,
	env=env,
	errors='replace',
	start_new_session=True,
	)

	print(f'Fuzzer started with PID {proc.pid}. Monitoring...', flush=True)

	reader_thread = threading.Thread(
	target=monitor.run,
	args=(proc.stdout,),
	daemon=True,
	)
	reader_thread.start()

	def stop_child():
	if proc.poll() is None:
	try:
	os.killpg(proc.pid, signal.SIGTERM)
	except ProcessLookupError:
	pass
	try:
	proc.wait(timeout=5)
	except subprocess.TimeoutExpired:
	try:
	os.killpg(proc.pid, signal.SIGKILL)
	except ProcessLookupError:
	pass
	proc.wait()

	def signal_handler(signum, _frame):
	stop_child()
	reader_thread.join(timeout=2.0)
	sys.exit(128 + signum)

	signal.signal(signal.SIGINT, signal_handler)
	signal.signal(signal.SIGTERM, signal_handler)

	start_time = time.time()
	last_report = 0
	limit_reached = False

	try:
	while reader_thread.is_alive() or proc.poll() is None:
	reader_thread.join(timeout=1.0)
	now = time.time()
	elapsed = int(now - start_time)

	minute = elapsed // 60
	latest_iter = monitor.get_progress()

	if minute > last_report:
	last_report = minute
	timestamp = time.strftime('%H:%M:%S')
	print(
	f'[{timestamp}] Runtime: {last_report} min, Latest'
	f' Iteration: {latest_iter}',
	flush=True,
	)

	if args.max_iters > 0 and latest_iter >= args.max_iters:
	print(
	f'Reached max iterations ({args.max_iters}). Stopping'
	' fuzzer...',
	flush=True,
	)
	limit_reached = True
	stop_child()
	break
	finally:
	stop_child()
	reader_thread.join(timeout=5.0)

	exit_code = proc.returncode

	if limit_reached:
	print(
	f'SUCCESS: Reached max iterations ({args.max_iters}) without finding'
	' a bug.',
	)
	return 0

	bug_found, iteration, seed, recent_lines = monitor.get_status()

	if bug_found:
	print('SUCCESS: Bug found!')
	print(f'Iteration: {iteration}')
	print(f'Seed: {seed}')
	print(f'Exit code: {exit_code}')
	return 0

	print('FAILURE: Fuzzer stopped unexpectedly without finding a bug.')
	print(f'Exit code: {exit_code}')
	if recent_lines:
	print('Last 20 lines of log:')
	for line in recent_lines:
	print(line.rstrip('\r\n'))
	return 1


	if __name__ == '__main__':
	sys.exit(main())