~bzr-pqm/bzr/bzr.dev

# Copyright (C) 2007, 2009, 2010 Canonical Ltd

#   Authors: Robert Collins <robert.collins@canonical.com>

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

"""Support for running strace against the current process."""

import errno

import os

import signal

import subprocess

import tempfile

from bzrlib import errors

# this is currently test-focused, so importing bzrlib.tests is ok. We might

# want to move feature to its own module though.

from bzrlib.tests import Feature

def strace(function, *args, **kwargs):

    """Invoke strace on function.

    :return: a tuple: function-result, a StraceResult.

    """

    return strace_detailed(function, args, kwargs)

def strace_detailed(function, args, kwargs, follow_children=True):

    # FIXME: strace is buggy

    # (https://bugs.launchpad.net/ubuntu/+source/strace/+bug/103133) and the

    # test suite hangs if the '-f' is given to strace *and* more than one

    # thread is running. Using follow_children=False allows the test suite to

    # disable fork following to work around the bug.

    # capture strace output to a file

    log_file = tempfile.NamedTemporaryFile()

    log_file_fd = log_file.fileno()

    err_file = tempfile.NamedTemporaryFile()

    pid = os.getpid()

    # start strace

    strace_cmd = ['strace', '-r', '-tt', '-p', str(pid), '-o', log_file.name]

    if follow_children:

        strace_args.append('-f')

    # need to catch both stdout and stderr to work around

    # bug 627208

    proc = subprocess.Popen(strace_cmd,

                            stdout=subprocess.PIPE,

                            stderr=err_file.fileno())

    # Wait for strace to attach

    attached_notice = proc.stdout.readline()

    # Run the function to strace

    result = function(*args, **kwargs)

    # stop strace

    os.kill(proc.pid, signal.SIGQUIT)

    proc.communicate()

    # grab the log

    log_file.seek(0)

    log = log_file.read()

    log_file.close()

    # and stderr

    err_file.seek(0)

    err_messages = err_file.read()

    err_file.close()

    # and read any errors

    if err_messages.startswith("attach: ptrace(PTRACE_ATTACH,"):

        raise StraceError(err_messages=err_messages)

    return result, StraceResult(log, err_messages)

class StraceError(errors.BzrError):

    _fmt = "strace failed: %(err_messages)s"

class StraceResult(object):

    """The result of stracing a function."""

    def __init__(self, raw_log, err_messages):

        """Create a StraceResult.

        :param raw_log: The output that strace created.

        """

        self.raw_log = raw_log

        self.err_messages = err_messages

class _StraceFeature(Feature):

    def _probe(self):

        try:

            proc = subprocess.Popen(['strace'],

                stderr=subprocess.PIPE,

                stdout=subprocess.PIPE)

            proc.communicate()

            return True

        except OSError, e:

            if e.errno == errno.ENOENT:

                # strace is not installed

                return False

            else:

                raise

    def feature_name(self):

        return 'strace'

StraceFeature = _StraceFeature()