import os
import re
import shlex
import shutil
import subprocess
import sys
import sysconfig
import unittest
from test import support
GDB_PROGRAM = shutil.which('gdb') or 'gdb'
# Location of custom hooks file in a repository checkout.
CHECKOUT_HOOK_PATH = os.path.join(os.path.dirname(sys.executable),
'python-gdb.py')
SAMPLE_SCRIPT = os.path.join(os.path.dirname(__file__), 'gdb_sample.py')
BREAKPOINT_FN = 'builtin_id'
PYTHONHASHSEED = '123'
def clean_environment():
# Remove PYTHON* environment variables such as PYTHONHOME
return {name: value for name, value in os.environ.items()
if not name.startswith('PYTHON')}
# Temporary value until it's initialized by get_gdb_version() below
GDB_VERSION = (0, 0)
def run_gdb(*args, exitcode=0, check=True, **env_vars):
"""Runs gdb in --batch mode with the additional arguments given by *args.
Returns its (stdout, stderr) decoded from utf-8 using the replace handler.
"""
env = clean_environment()
if env_vars:
env.update(env_vars)
cmd = [GDB_PROGRAM,
# Batch mode: Exit after processing all the command files
# specified with -x/--command
'--batch',
# -nx: Do not execute commands from any .gdbinit initialization
# files (gh-66384)
'-nx']
if GDB_VERSION >= (7, 4):
cmd.extend(('--init-eval-command',
f'add-auto-load-safe-path {CHECKOUT_HOOK_PATH}'))
cmd.extend(args)
proc = subprocess.run(
cmd,
# Redirect stdin to prevent gdb from messing with the terminal settings
stdin=subprocess.PIPE,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
encoding="utf8", errors="backslashreplace",
env=env)
stdout = proc.stdout
stderr = proc.stderr
if check and proc.returncode != exitcode:
cmd_text = shlex.join(cmd)
raise Exception(f"{cmd_text} failed with exit code {proc.returncode}, "
f"expected exit code {exitcode}:\n"
f"stdout={stdout!r}\n"
f"stderr={stderr!r}")
return (stdout, stderr)
def get_gdb_version():
try:
stdout, stderr = run_gdb('--version')
except OSError as exc:
# This is what "no gdb" looks like. There may, however, be other
# errors that manifest this way too.
raise unittest.SkipTest(f"Couldn't find gdb program on the path: {exc}")
# Regex to parse:
# 'GNU gdb (GDB; SUSE Linux Enterprise 12) 7.7\n' -> 7.7
# 'GNU gdb (GDB) Fedora 7.9.1-17.fc22\n' -> 7.9
# 'GNU gdb 6.1.1 [FreeBSD]\n' -> 6.1
# 'GNU gdb (GDB) Fedora (7.5.1-37.fc18)\n' -> 7.5
# 'HP gdb 6.7 for HP Itanium (32 or 64 bit) and target HP-UX 11iv2 and 11iv3.\n' -> 6.7
match = re.search(r"^(?:GNU|HP) gdb.*?\b(\d+)\.(\d+)", stdout)
if match is None:
raise Exception("unable to parse gdb version: %r" % stdout)
version_text = stdout
major = int(match.group(1))
minor = int(match.group(2))
version = (major, minor)
return (version_text, version)
GDB_VERSION_TEXT, GDB_VERSION = get_gdb_version()
if GDB_VERSION < (7, 0):
raise unittest.SkipTest(
f"gdb versions before 7.0 didn't support python embedding. "
f"Saw gdb version {GDB_VERSION[0]}.{GDB_VERSION[1]}:\n"
f"{GDB_VERSION_TEXT}")
def check_usable_gdb():
# Verify that "gdb" was built with the embedded Python support enabled and
# verify that "gdb" can load our custom hooks, as OS security settings may
# disallow this without a customized .gdbinit.
stdout, stderr = run_gdb(
'--eval-command=python import sys; print(sys.version_info)',
'--args', sys.executable,
check=False)
if "auto-loading has been declined" in stderr:
raise unittest.SkipTest(
f"gdb security settings prevent use of custom hooks; "
f"stderr: {stderr!r}")
if not stdout:
raise unittest.SkipTest(
f"gdb not built with embedded python support; "
f"stderr: {stderr!r}")
if "major=2" in stdout:
raise unittest.SkipTest("gdb built with Python 2")
check_usable_gdb()
# Control-flow enforcement technology
def cet_protection():
cflags = sysconfig.get_config_var('CFLAGS')
if not cflags:
return False
flags = cflags.split()
# True if "-mcet -fcf-protection" options are found, but false
# if "-fcf-protection=none" or "-fcf-protection=return" is found.
return (('-mcet' in flags)
and any((flag.startswith('-fcf-protection')
and not flag.endswith(("=none", "=return")))
for flag in flags))
CET_PROTECTION = cet_protection()
def setup_module():
if support.verbose:
print(f"gdb version {GDB_VERSION[0]}.{GDB_VERSION[1]}:")
for line in GDB_VERSION_TEXT.splitlines():
print(" " * 4 + line)
print(f" path: {GDB_PROGRAM}")
print()
class DebuggerTests(unittest.TestCase):
"""Test that the debugger can debug Python."""
def get_stack_trace(self, source=None, script=None,
breakpoint=BREAKPOINT_FN,
cmds_after_breakpoint=None,
import_site=False,
ignore_stderr=False):
'''
Run 'python -c SOURCE' under gdb with a breakpoint.
Support injecting commands after the breakpoint is reached
Returns the stdout from gdb
cmds_after_breakpoint: if provided, a list of strings: gdb commands
'''
# We use "set breakpoint pending yes" to avoid blocking with a:
# Function "foo" not defined.
# Make breakpoint pending on future shared library load? (y or [n])
# error, which typically happens python is dynamically linked (the
# breakpoints of interest are to be found in the shared library)
# When this happens, we still get:
# Function "textiowrapper_write" not defined.
# emitted to stderr each time, alas.
# Initially I had "--eval-command=continue" here, but removed it to
# avoid repeated print breakpoints when traversing hierarchical data
# structures
# Generate a list of commands in gdb's language:
commands = [
'set breakpoint pending yes',
'break %s' % breakpoint,
# The tests assume that the first frame of printed
# backtrace will not contain program counter,
# that is however not guaranteed by gdb
# therefore we need to use 'set print address off' to
# make sure the counter is not there. For example:
# #0 in PyObject_Print ...
# is assumed, but sometimes this can be e.g.
# #0 0x00003fffb7dd1798 in PyObject_Print ...
'set print address off',
'run',
]
# GDB as of 7.4 onwards can distinguish between the
# value of a variable at entry vs current value:
# http://sourceware.org/gdb/onlinedocs/gdb/Variables.html
# which leads to the selftests failing with errors like this:
# AssertionError: 'v@entry=()' != '()'
# Disable this:
if GDB_VERSION >= (7, 4):
commands += ['set print entry-values no']
if cmds_after_breakpoint:
if CET_PROTECTION:
# bpo-32962: When Python is compiled with -mcet
# -fcf-protection, function arguments are unusable before
# running the first instruction of the function entry point.
# The 'next' command makes the required first step.
commands += ['next']
commands += cmds_after_breakpoint
else:
commands += ['backtrace']
# print commands
# Use "commands" to generate the arguments with which to invoke "gdb":
args = ['--eval-command=%s' % cmd for cmd in commands]
args += ["--args",
sys.executable]
args.extend(subprocess._args_from_interpreter_flags())
if not import_site:
# -S suppresses the default 'import site'
args += ["-S"]
if source:
args += ["-c", source]
elif script:
args += [script]
# Use "args" to invoke gdb, capturing stdout, stderr:
out, err = run_gdb(*args, PYTHONHASHSEED=PYTHONHASHSEED)
if not ignore_stderr:
for line in err.splitlines():
print(line, file=sys.stderr)
# bpo-34007: Sometimes some versions of the shared libraries that
# are part of the traceback are compiled in optimised mode and the
# Program Counter (PC) is not present, not allowing gdb to walk the
# frames back. When this happens, the Python bindings of gdb raise
# an exception, making the test impossible to succeed.
if "PC not saved" in err:
raise unittest.SkipTest("gdb cannot walk the frame object"
" because the Program Counter is"
" not present")
# bpo-40019: Skip the test if gdb failed to read debug information
# because the Python binary is optimized.
for pattern in (
'(frame information optimized out)',
'Unable to read information on python frame',
# gh-91960: On Python built with "clang -Og", gdb gets
# "frame=<optimized out>" for _PyEval_EvalFrameDefault() parameter
'(unable to read python frame information)',
# gh-104736: On Python built with "clang -Og" on ppc64le,
# "py-bt" displays a truncated or not traceback, but "where"
# logs this error message:
'Backtrace stopped: frame did not save the PC',
# gh-104736: When "bt" command displays something like:
# "#1 0x0000000000000000 in ?? ()", the traceback is likely
# truncated or wrong.
' ?? ()',
):
if pattern in out:
raise unittest.SkipTest(f"{pattern!r} found in gdb output")
return out
def assertEndsWith(self, actual, exp_end):
'''Ensure that the given "actual" string ends with "exp_end"'''
self.assertTrue(actual.endswith(exp_end),
msg='%r did not end with %r' % (actual, exp_end))
def assertMultilineMatches(self, actual, pattern):
m = re.match(pattern, actual, re.DOTALL)
if not m:
self.fail(msg='%r did not match %r' % (actual, pattern))
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