Function _get_base_temp_dir

Lib/multiprocessing/util.py:155–209

Get a temporary directory where socket files will be created. To prevent additional imports, pass a pre-imported 'tempfile' module.

(tempfile)

        current_process._config['tempdir'] = None

def _get_base_temp_dir(tempfile):
    """Get a temporary directory where socket files will be created.

    To prevent additional imports, pass a pre-imported 'tempfile' module.
    """
    if os.name == 'nt':
        return None
    # Most of the time, the default temporary directory is /tmp. Thus,
    # listener sockets files "$TMPDIR/pymp-XXXXXXXX/sock-XXXXXXXX" do
    # not have a path length exceeding SUN_PATH_MAX.
    #
    # If users specify their own temporary directory, we may be unable
    # to create those files. Therefore, we fall back to the system-wide
    # temporary directory /tmp, assumed to exist on POSIX systems.
    #
    # See https://github.com/python/cpython/issues/132124.
    base_tempdir = tempfile.gettempdir()
    # Files created in a temporary directory are suffixed by a string
    # generated by tempfile._RandomNameSequence, which, by design,
    # is 8 characters long.
    #
    # Thus, the socket file path length (without NULL terminator) will be:
    #
    #   len(base_tempdir + '/pymp-XXXXXXXX' + '/sock-XXXXXXXX')
    sun_path_len = len(base_tempdir) + 14 + 14
    # Strict inequality to account for the NULL terminator.
    # See https://github.com/python/cpython/issues/140734.
    if sun_path_len < _SUN_PATH_MAX:
        return base_tempdir
    # Fallback to the default system-wide temporary directory.
    # This ignores user-defined environment variables.
    #
    # On POSIX systems, /tmp MUST be writable by any application [1].
    # We however emit a warning if this is not the case to prevent
    # obscure errors later in the execution.
    #
    # On some legacy systems, /var/tmp and /usr/tmp can be present
    # and will be used instead.
    #
    # [1]: https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch03s18.html
    dirlist = ['/tmp', '/var/tmp', '/usr/tmp']
    try:
        base_system_tempdir = tempfile._get_default_tempdir(dirlist)
    except FileNotFoundError:
        warn("Process-wide temporary directory %s will not be usable for "
             "creating socket files and no usable system-wide temporary "
             "directory was found in %s", base_tempdir, dirlist)
        # At this point, the system-wide temporary directory is not usable
        # but we may assume that the user-defined one is, even if we will
        # not be able to write socket files out there.
        return base_tempdir
    warn("Ignoring user-defined temporary directory: %s", base_tempdir)
    # at most max(map(len, dirlist)) + 14 + 14 = 36 characters
    assert len(base_system_tempdir) + 14 + 14 < _SUN_PATH_MAX
    return base_system_tempdir

def get_temp_dir():
    # get name of a temp directory which will be automatically cleaned up