Index: lib/asan/scripts/asan_symbolize.py
===================================================================
--- lib/asan/scripts/asan_symbolize.py
+++ lib/asan/scripts/asan_symbolize.py
@@ -6,16 +6,37 @@
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
 #===------------------------------------------------------------------------===#
+"""
+Example of use:
+  asan_symbolize.py -c "$HOME/opt/cross/bin/arm-linux-gnueabi-" -s "$HOME/SymbolFiles" < asan.log
+
+Logging
+
+  The script can performing logging during operation. Logging is controlled via
+  environment variables:
+
+  ASAN_SYMBOLIZER_LOG_LEVEL
+    Sets the log level (debug, info, warning, error, or critical).
+    The default level is info.
+
+  ASAN_SYMBOLIZER_LOG_DEST
+    Sets the file path to write logging output to. If not set (default)
+    output in emitted to standard error.
+
+  Example:
+    ASAN_SYMBOLIZER_LOG_LEVEL=debug ASAN_SYMBOLIZER_LOG_DEST=./foo asan_symbolize.py --help
+  
+"""
 import argparse
 import bisect
 import getopt
+import logging
 import os
 import re
 import subprocess
 import sys
 
 symbolizers = {}
-DEBUG = False
 demangle = False
 binutils_prefix = None
 sysroot_path = None
@@ -87,8 +108,7 @@
     if self.system == 'Darwin':
       for hint in self.dsym_hints:
         cmd.append('--dsym-hint=%s' % hint)
-    if DEBUG:
-      print(' '.join(cmd))
+    logging.debug(' '.join(cmd))
     try:
       result = subprocess.Popen(cmd, stdin=subprocess.PIPE,
                                 stdout=subprocess.PIPE,
@@ -105,8 +125,7 @@
     result = []
     try:
       symbolizer_input = '"%s" %s' % (binary, offset)
-      if DEBUG:
-        print(symbolizer_input)
+      logging.debug(symbolizer_input)
       self.pipe.stdin.write("%s\n" % symbolizer_input)
       while True:
         function_name = self.pipe.stdout.readline().rstrip()
@@ -151,8 +170,7 @@
     if demangle:
       cmd += ['--demangle']
     cmd += ['-e', self.binary]
-    if DEBUG:
-      print(' '.join(cmd))
+    logging.debug(' '.join(cmd))
     return subprocess.Popen(cmd,
                             stdin=subprocess.PIPE, stdout=subprocess.PIPE,
                             bufsize=0,
@@ -221,8 +239,7 @@
     self.open_atos()
 
   def open_atos(self):
-    if DEBUG:
-      print('atos -o %s -arch %s' % (self.binary, self.arch))
+    logging.debug('atos -o %s -arch %s', self.binary, self.arch)
     cmdline = ['atos', '-o', self.binary, '-arch', self.arch]
     self.atos = UnbufferedLineConverter(cmdline, close_stderr=True)
 
@@ -240,8 +257,7 @@
     # A well-formed atos response looks like this:
     #   foo(type1, type2) (in object.name) (filename.cc:80)
     match = re.match('^(.*) \(in (.*)\) \((.*:\d*)\)$', atos_line)
-    if DEBUG:
-      print('atos_line: ', atos_line)
+    logging.debug('atos_line: %s', atos_line)
     if match:
       function_name = match.group(1)
       function_name = re.sub('\(.*?\)', '', function_name)
@@ -454,8 +470,7 @@
     match = re.match(stack_trace_line_format, line)
     if not match:
       return [self.current_line]
-    if DEBUG:
-      print(line)
+    logging.debug(line)
     _, frameno_str, addr, binary, offset = match.groups()
     arch = ""
     # Arch can be embedded in the filename, e.g.: "libabc.dylib:x86_64h"
@@ -479,14 +494,38 @@
         symbolized_line = self.symbolize_address(addr, original_binary, offset, arch)
     return self.get_symbolized_lines(symbolized_line)
 
+def setup_logging():
+  valid_logging_levels = [ 'debug', 'info', 'warning', 'error', 'critical' ]
+  logging_level = os.getenv('ASAN_SYMBOLIZER_LOG_LEVEL', valid_logging_levels[1])
+  if logging_level not in valid_logging_levels:
+    print('ASAN_SYMBOLIZER_LOG_LEVEL : Invalid logging level "{}"'.format(logging_level))
+    return False
+  if logging_level == 'debug':
+    log_format = '%(levelname)s: [%(funcName)s() %(filename)s:%(lineno)d] %(message)s'
+  else:
+    log_format = '%(levelname)s: %(message)s'
+  basic_config = {
+    'level': getattr(logging, logging_level.upper()),
+    'format': log_format
+  }
+  logging_dest = os.getenv('ASAN_SYMBOLIZER_LOG_DEST', None)
+  if logging_dest:
+    basic_config['filename'] = logging_dest
+  logging.basicConfig(**basic_config)
+  logging.debug('Logging level set to "{}" and directing output to "{}"'.format(
+    logging_level,
+    'stderr' if logging_dest is None else logging_dest)
+  )
+  return True
+
 
 if __name__ == '__main__':
+  if not setup_logging():
+    sys.exit(1)
   parser = argparse.ArgumentParser(
       formatter_class=argparse.RawDescriptionHelpFormatter,
       description='ASan symbolization script',
-      epilog='Example of use:\n'
-             'asan_symbolize.py -c "$HOME/opt/cross/bin/arm-linux-gnueabi-" '
-             '-s "$HOME/SymbolFiles" < asan.log')
+      epilog=__doc__)
   parser.add_argument('path_to_cut', nargs='*',
                       help='pattern to be cut from the result file path ')
   parser.add_argument('-d','--demangle', action='store_true',