#!/usr/bin/env python3
"""Script to generate Chromium's Abseil .def files at roll time.
This script generates //third_party/abseil-app/absl/symbols_*.def at Abseil
roll time.
Since Abseil doesn't export symbols, Chromium is forced to consider all
Abseil's symbols as publicly visible. On POSIX it is possible to use
-fvisibility=default but on Windows a .def file with all the symbols
is needed.
Unless you are on a Windows machine, you need to set up your Chromium
checkout for cross-compilation by following the instructions at
https://chromium.googlesource.com/chromium/src.git/+/main/docs/win_cross.md.
If you are on Windows, you may need to tweak this script to run, e.g. by
changing "gn" to "gn.bat", changing "llvm-nm" to the name of your copy of
llvm-nm, etc.
"""
import fnmatch
import logging
import os
import re
import subprocess
import sys
import tempfile
import time
# Matches mangled symbols containing 'absl' or starting with 'Absl'. This is
# a good enough heuristic to select Abseil symbols to list in the .def file.
# See https://learn.microsoft.com/en-us/cpp/build/reference/decorated-names,
# which describes decorations under different calling conventions. We mostly
# just attempt to handle any leading underscore for C names (as in __cdecl).
ABSL_SYM_RE = r'0* [BT] (?P<symbol>[?]+[^?].*absl.*|_?Absl.*)'
if sys.platform == 'win32':
# Typical dumpbin /symbol lines look like this:
# 04B 0000000C SECT14 notype Static | ?$S1@?1??SetCurrent
# ThreadIdentity@base_internal@absl@@YAXPAUThreadIdentity@12@P6AXPAX@Z@Z@4IA
# (unsigned int `void __cdecl absl::base_internal::SetCurrentThreadIdentity...
# We need to start on "| ?" and end on the first " (" (stopping on space would
# also work).
# This regex is identical inside the () characters except for the ? after .*,
# which is needed to prevent greedily grabbing the undecorated version of the
# symbols.
ABSL_SYM_RE = r'.*External \| (?P<symbol>[?]+[^?].*?absl.*?|_?Absl.*?)($| \(.*)'
# Typical exported symbols in dumpbin /directives look like:
# /EXPORT:?kHexChar@numbers_internal@absl@@3QBDB,DATA
ABSL_EXPORTED_RE = r'.*/EXPORT:(.*),.*'
def _DebugOrRelease(is_debug):
return 'dbg' if is_debug else 'rel'
def _GenerateDefFile(cpu, is_debug, extra_gn_args=[], suffix=None):
"""Generates a .def file for the absl component build on the specified CPU."""
if extra_gn_args:
assert suffix != None, 'suffix is needed when extra_gn_args is used'
flavor = _DebugOrRelease(is_debug)
gn_args = [
'ffmpeg_branding = "Chrome"',
'is_component_build = true',
'is_debug = {}'.format(str(is_debug).lower()),
'proprietary_codecs = true',
'symbol_level = 0',
'target_cpu = "{}"'.format(cpu),
'target_os = "win"',
]
gn_args.extend(extra_gn_args)
gn = 'gn'
autoninja = 'autoninja'
symbol_dumper = ['third_party/llvm-build/Release+Asserts/bin/llvm-nm']
if sys.platform == 'win32':
gn = 'gn.bat'
autoninja = 'autoninja.bat'
symbol_dumper = ['dumpbin', '/symbols']
import shutil
if not shutil.which('dumpbin'):
logging.error('dumpbin not found. Run tools\win\setenv.bat.')
exit(1)
cwd = os.getcwd()
with tempfile.TemporaryDirectory(dir=cwd) as out_dir:
logging.info('[%s - %s] Creating tmp out dir in %s', cpu, flavor, out_dir)
subprocess.check_call([gn, 'gen', out_dir, '--args=' + ' '.join(gn_args)],
cwd=cwd)
logging.info('[%s - %s] gn gen completed', cpu, flavor)
subprocess.check_call(
[autoninja, '-C', out_dir, 'third_party/abseil-cpp:absl_component_deps'],
cwd=os.getcwd())
logging.info('[%s - %s] autoninja completed', cpu, flavor)
obj_files = []
for root, _dirnames, filenames in os.walk(
os.path.join(out_dir, 'obj', 'third_party', 'abseil-cpp')):
matched_files = fnmatch.filter(filenames, '*.obj')
obj_files.extend((os.path.join(root, f) for f in matched_files))
logging.info('[%s - %s] Found %d object files.', cpu, flavor, len(obj_files))
absl_symbols = set()
dll_exports = set()
if sys.platform == 'win32':
for f in obj_files:
# Track all of the functions exported with __declspec(dllexport) and
# don't list them in the .def file - double-exports are not allowed. The
# error is "lld-link: error: duplicate /export option".
exports_out = subprocess.check_output(['dumpbin', '/directives', f], cwd=os.getcwd())
for line in exports_out.splitlines():
line = line.decode('utf-8')
match = re.match(ABSL_EXPORTED_RE, line)
if match:
dll_exports.add(match.groups()[0])
for f in obj_files:
stdout = subprocess.check_output(symbol_dumper + [f], cwd=os.getcwd())
for line in stdout.splitlines():
try:
line = line.decode('utf-8')
except UnicodeDecodeError:
# Due to a dumpbin bug there are sometimes invalid utf-8 characters in
# the output. This only happens on an unimportant line so it can
# safely and silently be skipped.
# https://developercommunity.visualstudio.com/content/problem/1091330/dumpbin-symbols-produces-randomly-wrong-output-on.html
continue
match = re.match(ABSL_SYM_RE, line)
if match:
symbol = match.group('symbol')
assert symbol.count(' ') == 0, ('Regex matched too much, probably got '
'undecorated name as well')
# Avoid getting names exported with dllexport, to avoid
# "lld-link: error: duplicate /export option" on symbols such as:
# ?kHexChar@numbers_internal@absl@@3QBDB
if symbol in dll_exports:
continue
# Avoid to export deleting dtors since they trigger
# "lld-link: error: export of deleting dtor" linker errors, see
# crbug.com/1201277.
if symbol.startswith('??_G'):
continue
# Strip any leading underscore for C names (as in __cdecl). It's only
# there on x86, but the x86 toolchain falls over when you include it!
if cpu == 'x86' and symbol.startswith('_'):
symbol = symbol[1:]
absl_symbols.add(symbol)
logging.info('[%s - %s] Found %d absl symbols.', cpu, flavor, len(absl_symbols))
if extra_gn_args:
def_file = os.path.join('third_party', 'abseil-cpp',
'symbols_{}_{}_{}.def'.format(cpu, flavor, suffix))
else:
def_file = os.path.join('third_party', 'abseil-cpp',
'symbols_{}_{}.def'.format(cpu, flavor))
with open(def_file, 'w', newline='') as f:
f.write('EXPORTS\n')
for s in sorted(absl_symbols):
f.write(' {}\n'.format(s))
# Hack, it looks like there is a race in the directory cleanup.
time.sleep(10)
logging.info('[%s - %s] .def file successfully generated.', cpu, flavor)
if __name__ == '__main__':
logging.getLogger().setLevel(logging.INFO)
if sys.version_info.major == 2:
logging.error('This script requires Python 3.')
exit(1)
if not os.getcwd().endswith('src') or not os.path.exists('chrome/browser'):
logging.error('Run this script from a chromium/src/ directory.')
exit(1)
_GenerateDefFile('x86', True)
_GenerateDefFile('x86', False)
_GenerateDefFile('x64', True)
_GenerateDefFile('x64', False)
_GenerateDefFile('x64', False, ['is_asan = true'], 'asan')
_GenerateDefFile('arm64', True)
_GenerateDefFile('arm64', False)
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