Added an unmodified copy of SCons to third_party.

scons-2.0.1/engine/SCons/Node/FS.py

+"""scons.Node.FS
+
+File system nodes.
+
+These Nodes represent the canonical external objects that people think
+of when they think of building software: files and directories.
+
+This holds a "default_fs" variable that should be initialized with an FS
+that can be used by scripts or modules looking for the canonical default.
+
+"""
+
+#
+# Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 The SCons Foundation
+#
+# Permission is hereby granted, free of charge, to any person obtaining
+# a copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+#
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
+# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
+# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+__revision__ = "src/engine/SCons/Node/FS.py 5134 2010/08/16 23:02:40 bdeegan"
+
+import fnmatch
+import os
+import re
+import shutil
+import stat
+import sys
+import time
+import codecs
+
+import SCons.Action
+from SCons.Debug import logInstanceCreation
+import SCons.Errors
+import SCons.Memoize
+import SCons.Node
+import SCons.Node.Alias
+import SCons.Subst
+import SCons.Util
+import SCons.Warnings
+
+from SCons.Debug import Trace
+
+do_store_info = True
+
+
+class EntryProxyAttributeError(AttributeError):
+    """
+    An AttributeError subclass for recording and displaying the name
+    of the underlying Entry involved in an AttributeError exception.
+    """
+    def __init__(self, entry_proxy, attribute):
+        AttributeError.__init__(self)
+        self.entry_proxy = entry_proxy
+        self.attribute = attribute
+    def __str__(self):
+        entry = self.entry_proxy.get()
+        fmt = "%s instance %s has no attribute %s"
+        return fmt % (entry.__class__.__name__,
+                      repr(entry.name),
+                      repr(self.attribute))
+
+# The max_drift value:  by default, use a cached signature value for
+# any file that's been untouched for more than two days.
+default_max_drift = 2*24*60*60
+
+#
+# We stringify these file system Nodes a lot.  Turning a file system Node
+# into a string is non-trivial, because the final string representation
+# can depend on a lot of factors:  whether it's a derived target or not,
+# whether it's linked to a repository or source directory, and whether
+# there's duplication going on.  The normal technique for optimizing
+# calculations like this is to memoize (cache) the string value, so you
+# only have to do the calculation once.
+#
+# A number of the above factors, however, can be set after we've already
+# been asked to return a string for a Node, because a Repository() or
+# VariantDir() call or the like may not occur until later in SConscript
+# files.  So this variable controls whether we bother trying to save
+# string values for Nodes.  The wrapper interface can set this whenever
+# they're done mucking with Repository and VariantDir and the other stuff,
+# to let this module know it can start returning saved string values
+# for Nodes.
+#
+Save_Strings = None
+
+def save_strings(val):
+    global Save_Strings
+    Save_Strings = val
+
+#
+# Avoid unnecessary function calls by recording a Boolean value that
+# tells us whether or not os.path.splitdrive() actually does anything
+# on this system, and therefore whether we need to bother calling it
+# when looking up path names in various methods below.
+# 
+
+do_splitdrive = None
+
+def initialize_do_splitdrive():
+    global do_splitdrive
+    drive, path = os.path.splitdrive('X:/foo')
+    do_splitdrive = not not drive
+
+initialize_do_splitdrive()
+
+#
+
+needs_normpath_check = None
+
+def initialize_normpath_check():
+    """
+    Initialize the normpath_check regular expression.
+
+    This function is used by the unit tests to re-initialize the pattern
+    when testing for behavior with different values of os.sep.
+    """
+    global needs_normpath_check
+    if os.sep == '/':
+        pattern = r'.*/|\.$|\.\.$'
+    else:
+        pattern = r'.*[/%s]|\.$|\.\.$' % re.escape(os.sep)
+    needs_normpath_check = re.compile(pattern)
+
+initialize_normpath_check()
+
+#
+# SCons.Action objects for interacting with the outside world.
+#
+# The Node.FS methods in this module should use these actions to
+# create and/or remove files and directories; they should *not* use
+# os.{link,symlink,unlink,mkdir}(), etc., directly.
+#
+# Using these SCons.Action objects ensures that descriptions of these
+# external activities are properly displayed, that the displays are
+# suppressed when the -s (silent) option is used, and (most importantly)
+# the actions are disabled when the the -n option is used, in which case
+# there should be *no* changes to the external file system(s)...
+#
+
+if hasattr(os, 'link'):
+    def _hardlink_func(fs, src, dst):
+        # If the source is a symlink, we can't just hard-link to it
+        # because a relative symlink may point somewhere completely
+        # different.  We must disambiguate the symlink and then
+        # hard-link the final destination file.
+        while fs.islink(src):
+            link = fs.readlink(src)
+            if not os.path.isabs(link):
+                src = link
+            else:
+                src = os.path.join(os.path.dirname(src), link)
+        fs.link(src, dst)
+else:
+    _hardlink_func = None
+
+if hasattr(os, 'symlink'):
+    def _softlink_func(fs, src, dst):
+        fs.symlink(src, dst)
+else:
+    _softlink_func = None
+
+def _copy_func(fs, src, dest):
+    shutil.copy2(src, dest)
+    st = fs.stat(src)
+    fs.chmod(dest, stat.S_IMODE(st[stat.ST_MODE]) | stat.S_IWRITE)
+
+
+Valid_Duplicates = ['hard-soft-copy', 'soft-hard-copy',
+                    'hard-copy', 'soft-copy', 'copy']
+
+Link_Funcs = [] # contains the callables of the specified duplication style
+
+def set_duplicate(duplicate):
+    # Fill in the Link_Funcs list according to the argument
+    # (discarding those not available on the platform).
+
+    # Set up the dictionary that maps the argument names to the
+    # underlying implementations.  We do this inside this function,
+    # not in the top-level module code, so that we can remap os.link
+    # and os.symlink for testing purposes.
+    link_dict = {
+        'hard' : _hardlink_func,
+        'soft' : _softlink_func,
+        'copy' : _copy_func
+    }
+
+    if not duplicate in Valid_Duplicates:
+        raise SCons.Errors.InternalError("The argument of set_duplicate "
+                                           "should be in Valid_Duplicates")
+    global Link_Funcs
+    Link_Funcs = []
+    for func in duplicate.split('-'):
+        if link_dict[func]:
+            Link_Funcs.append(link_dict[func])
+
+def LinkFunc(target, source, env):
+    # Relative paths cause problems with symbolic links, so
+    # we use absolute paths, which may be a problem for people
+    # who want to move their soft-linked src-trees around. Those
+    # people should use the 'hard-copy' mode, softlinks cannot be
+    # used for that; at least I have no idea how ...
+    src = source[0].abspath
+    dest = target[0].abspath
+    dir, file = os.path.split(dest)
+    if dir and not target[0].fs.isdir(dir):
+        os.makedirs(dir)
+    if not Link_Funcs:
+        # Set a default order of link functions.
+        set_duplicate('hard-soft-copy')
+    fs = source[0].fs
+    # Now link the files with the previously specified order.
+    for func in Link_Funcs:
+        try:
+            func(fs, src, dest)
+            break
+        except (IOError, OSError):
+            # An OSError indicates something happened like a permissions
+            # problem or an attempt to symlink across file-system
+            # boundaries.  An IOError indicates something like the file
+            # not existing.  In either case, keeping trying additional
+            # functions in the list and only raise an error if the last
+            # one failed.
+            if func == Link_Funcs[-1]:
+                # exception of the last link method (copy) are fatal
+                raise
+    return 0
+
+Link = SCons.Action.Action(LinkFunc, None)
+def LocalString(target, source, env):
+    return 'Local copy of %s from %s' % (target[0], source[0])
+
+LocalCopy = SCons.Action.Action(LinkFunc, LocalString)
+
+def UnlinkFunc(target, source, env):
+    t = target[0]
+    t.fs.unlink(t.abspath)
+    return 0
+
+Unlink = SCons.Action.Action(UnlinkFunc, None)
+
+def MkdirFunc(target, source, env):
+    t = target[0]
+    if not t.exists():
+        t.fs.mkdir(t.abspath)
+    return 0
+
+Mkdir = SCons.Action.Action(MkdirFunc, None, presub=None)
+
+MkdirBuilder = None
+
+def get_MkdirBuilder():
+    global MkdirBuilder
+    if MkdirBuilder is None:
+        import SCons.Builder
+        import SCons.Defaults
+        # "env" will get filled in by Executor.get_build_env()
+        # calling SCons.Defaults.DefaultEnvironment() when necessary.
+        MkdirBuilder = SCons.Builder.Builder(action = Mkdir,
+                                             env = None,
+                                             explain = None,
+                                             is_explicit = None,
+                                             target_scanner = SCons.Defaults.DirEntryScanner,
+                                             name = "MkdirBuilder")
+    return MkdirBuilder
+
+class _Null(object):
+    pass
+
+_null = _Null()
+
+DefaultSCCSBuilder = None
+DefaultRCSBuilder = None
+
+def get_DefaultSCCSBuilder():
+    global DefaultSCCSBuilder
+    if DefaultSCCSBuilder is None:
+        import SCons.Builder
+        # "env" will get filled in by Executor.get_build_env()
+        # calling SCons.Defaults.DefaultEnvironment() when necessary.
+        act = SCons.Action.Action('$SCCSCOM', '$SCCSCOMSTR')
+        DefaultSCCSBuilder = SCons.Builder.Builder(action = act,
+                                                   env = None,
+                                                   name = "DefaultSCCSBuilder")
+    return DefaultSCCSBuilder
+
+def get_DefaultRCSBuilder():
+    global DefaultRCSBuilder
+    if DefaultRCSBuilder is None:
+        import SCons.Builder
+        # "env" will get filled in by Executor.get_build_env()
+        # calling SCons.Defaults.DefaultEnvironment() when necessary.
+        act = SCons.Action.Action('$RCS_COCOM', '$RCS_COCOMSTR')
+        DefaultRCSBuilder = SCons.Builder.Builder(action = act,
+                                                  env = None,
+                                                  name = "DefaultRCSBuilder")
+    return DefaultRCSBuilder
+
+# Cygwin's os.path.normcase pretends it's on a case-sensitive filesystem.
+_is_cygwin = sys.platform == "cygwin"
+if os.path.normcase("TeSt") == os.path.normpath("TeSt") and not _is_cygwin:
+    def _my_normcase(x):
+        return x
+else:
+    def _my_normcase(x):
+        return x.upper()
+
+
+
+class DiskChecker(object):
+    def __init__(self, type, do, ignore):
+        self.type = type
+        self.do = do
+        self.ignore = ignore
+        self.func = do
+    def __call__(self, *args, **kw):
+        return self.func(*args, **kw)
+    def set(self, list):
+        if self.type in list:
+            self.func = self.do
+        else:
+            self.func = self.ignore
+
+def do_diskcheck_match(node, predicate, errorfmt):
+    result = predicate()
+    try:
+        # If calling the predicate() cached a None value from stat(),
+        # remove it so it doesn't interfere with later attempts to
+        # build this Node as we walk the DAG.  (This isn't a great way
+        # to do this, we're reaching into an interface that doesn't
+        # really belong to us, but it's all about performance, so
+        # for now we'll just document the dependency...)
+        if node._memo['stat'] is None:
+            del node._memo['stat']
+    except (AttributeError, KeyError):
+        pass
+    if result:
+        raise TypeError(errorfmt % node.abspath)
+
+def ignore_diskcheck_match(node, predicate, errorfmt):
+    pass
+
+def do_diskcheck_rcs(node, name):
+    try:
+        rcs_dir = node.rcs_dir
+    except AttributeError:
+        if node.entry_exists_on_disk('RCS'):
+            rcs_dir = node.Dir('RCS')
+        else:
+            rcs_dir = None
+        node.rcs_dir = rcs_dir
+    if rcs_dir:
+        return rcs_dir.entry_exists_on_disk(name+',v')
+    return None
+
+def ignore_diskcheck_rcs(node, name):
+    return None
+
+def do_diskcheck_sccs(node, name):
+    try:
+        sccs_dir = node.sccs_dir
+    except AttributeError:
+        if node.entry_exists_on_disk('SCCS'):
+            sccs_dir = node.Dir('SCCS')
+        else:
+            sccs_dir = None
+        node.sccs_dir = sccs_dir
+    if sccs_dir:
+        return sccs_dir.entry_exists_on_disk('s.'+name)
+    return None
+
+def ignore_diskcheck_sccs(node, name):
+    return None
+
+diskcheck_match = DiskChecker('match', do_diskcheck_match, ignore_diskcheck_match)
+diskcheck_rcs = DiskChecker('rcs', do_diskcheck_rcs, ignore_diskcheck_rcs)
+diskcheck_sccs = DiskChecker('sccs', do_diskcheck_sccs, ignore_diskcheck_sccs)
+
+diskcheckers = [
+    diskcheck_match,
+    diskcheck_rcs,
+    diskcheck_sccs,
+]
+
+def set_diskcheck(list):
+    for dc in diskcheckers:
+        dc.set(list)
+
+def diskcheck_types():
+    return [dc.type for dc in diskcheckers]
+
+
+
+class EntryProxy(SCons.Util.Proxy):
+
+    __str__ = SCons.Util.Delegate('__str__')
+
+    def __get_abspath(self):
+        entry = self.get()
+        return SCons.Subst.SpecialAttrWrapper(entry.get_abspath(),
+                                             entry.name + "_abspath")
+
+    def __get_filebase(self):
+        name = self.get().name
+        return SCons.Subst.SpecialAttrWrapper(SCons.Util.splitext(name)[0],
+                                             name + "_filebase")
+
+    def __get_suffix(self):
+        name = self.get().name
+        return SCons.Subst.SpecialAttrWrapper(SCons.Util.splitext(name)[1],
+                                             name + "_suffix")
+
+    def __get_file(self):
+        name = self.get().name
+        return SCons.Subst.SpecialAttrWrapper(name, name + "_file")
+
+    def __get_base_path(self):
+        """Return the file's directory and file name, with the
+        suffix stripped."""
+        entry = self.get()
+        return SCons.Subst.SpecialAttrWrapper(SCons.Util.splitext(entry.get_path())[0],
+                                             entry.name + "_base")
+
+    def __get_posix_path(self):
+        """Return the path with / as the path separator,
+        regardless of platform."""
+        if os.sep == '/':
+            return self
+        else:
+            entry = self.get()
+            r = entry.get_path().replace(os.sep, '/')
+            return SCons.Subst.SpecialAttrWrapper(r, entry.name + "_posix")
+
+    def __get_windows_path(self):
+        """Return the path with \ as the path separator,
+        regardless of platform."""
+        if os.sep == '\\':
+            return self
+        else:
+            entry = self.get()
+            r = entry.get_path().replace(os.sep, '\\')
+            return SCons.Subst.SpecialAttrWrapper(r, entry.name + "_windows")
+
+    def __get_srcnode(self):
+        return EntryProxy(self.get().srcnode())
+
+    def __get_srcdir(self):
+        """Returns the directory containing the source node linked to this
+        node via VariantDir(), or the directory of this node if not linked."""
+        return EntryProxy(self.get().srcnode().dir)
+
+    def __get_rsrcnode(self):
+        return EntryProxy(self.get().srcnode().rfile())
+
+    def __get_rsrcdir(self):
+        """Returns the directory containing the source node linked to this
+        node via VariantDir(), or the directory of this node if not linked."""
+        return EntryProxy(self.get().srcnode().rfile().dir)
+
+    def __get_dir(self):
+        return EntryProxy(self.get().dir)
+
+    dictSpecialAttrs = { "base"     : __get_base_path,
+                         "posix"    : __get_posix_path,
+                         "windows"  : __get_windows_path,
+                         "win32"    : __get_windows_path,
+                         "srcpath"  : __get_srcnode,
+                         "srcdir"   : __get_srcdir,
+                         "dir"      : __get_dir,
+                         "abspath"  : __get_abspath,
+                         "filebase" : __get_filebase,
+                         "suffix"   : __get_suffix,
+                         "file"     : __get_file,
+                         "rsrcpath" : __get_rsrcnode,
+                         "rsrcdir"  : __get_rsrcdir,
+                       }
+
+    def __getattr__(self, name):
+        # This is how we implement the "special" attributes
+        # such as base, posix, srcdir, etc.
+        try:
+            attr_function = self.dictSpecialAttrs[name]
+        except KeyError:
+            try:
+                attr = SCons.Util.Proxy.__getattr__(self, name)
+            except AttributeError, e:
+                # Raise our own AttributeError subclass with an
+                # overridden __str__() method that identifies the
+                # name of the entry that caused the exception.
+                raise EntryProxyAttributeError(self, name)
+            return attr
+        else:
+            return attr_function(self)
+
+class Base(SCons.Node.Node):
+    """A generic class for file system entries.  This class is for
+    when we don't know yet whether the entry being looked up is a file
+    or a directory.  Instances of this class can morph into either
+    Dir or File objects by a later, more precise lookup.
+
+    Note: this class does not define __cmp__ and __hash__ for
+    efficiency reasons.  SCons does a lot of comparing of
+    Node.FS.{Base,Entry,File,Dir} objects, so those operations must be
+    as fast as possible, which means we want to use Python's built-in
+    object identity comparisons.
+    """
+
+    memoizer_counters = []
+
+    def __init__(self, name, directory, fs):
+        """Initialize a generic Node.FS.Base object.
+
+        Call the superclass initialization, take care of setting up
+        our relative and absolute paths, identify our parent
+        directory, and indicate that this node should use
+        signatures."""
+        if __debug__: logInstanceCreation(self, 'Node.FS.Base')
+        SCons.Node.Node.__init__(self)
+
+        # Filenames and paths are probably reused and are intern'ed to
+        # save some memory.
+        self.name = SCons.Util.silent_intern(name)
+        self.suffix = SCons.Util.silent_intern(SCons.Util.splitext(name)[1])
+        self.fs = fs
+
+        assert directory, "A directory must be provided"
+
+        self.abspath = SCons.Util.silent_intern(directory.entry_abspath(name))
+        self.labspath = SCons.Util.silent_intern(directory.entry_labspath(name))
+        if directory.path == '.':
+            self.path = SCons.Util.silent_intern(name)
+        else:
+            self.path = SCons.Util.silent_intern(directory.entry_path(name))
+        if directory.tpath == '.':
+            self.tpath = SCons.Util.silent_intern(name)
+        else:
+            self.tpath = SCons.Util.silent_intern(directory.entry_tpath(name))
+        self.path_elements = directory.path_elements + [self]
+
+        self.dir = directory
+        self.cwd = None # will hold the SConscript directory for target nodes
+        self.duplicate = directory.duplicate
+
+    def str_for_display(self):
+        return '"' + self.__str__() + '"'
+
+    def must_be_same(self, klass):
+        """
+        This node, which already existed, is being looked up as the
+        specified klass.  Raise an exception if it isn't.
+        """
+        if isinstance(self, klass) or klass is Entry:
+            return
+        raise TypeError("Tried to lookup %s '%s' as a %s." %\
+              (self.__class__.__name__, self.path, klass.__name__))
+
+    def get_dir(self):
+        return self.dir
+
+    def get_suffix(self):
+        return self.suffix
+
+    def rfile(self):
+        return self
+
+    def __str__(self):
+        """A Node.FS.Base object's string representation is its path
+        name."""
+        global Save_Strings
+        if Save_Strings:
+            return self._save_str()
+        return self._get_str()
+
+    memoizer_counters.append(SCons.Memoize.CountValue('_save_str'))
+
+    def _save_str(self):
+        try:
+            return self._memo['_save_str']
+        except KeyError:
+            pass
+        result = sys.intern(self._get_str())
+        self._memo['_save_str'] = result
+        return result
+
+    def _get_str(self):
+        global Save_Strings
+        if self.duplicate or self.is_derived():
+            return self.get_path()
+        srcnode = self.srcnode()
+        if srcnode.stat() is None and self.stat() is not None:
+            result = self.get_path()
+        else:
+            result = srcnode.get_path()
+        if not Save_Strings:
+            # We're not at the point where we're saving the string string
+            # representations of FS Nodes (because we haven't finished
+            # reading the SConscript files and need to have str() return
+            # things relative to them).  That also means we can't yet
+            # cache values returned (or not returned) by stat(), since
+            # Python code in the SConscript files might still create
+            # or otherwise affect the on-disk file.  So get rid of the
+            # values that the underlying stat() method saved.
+            try: del self._memo['stat']
+            except KeyError: pass
+            if self is not srcnode:
+                try: del srcnode._memo['stat']
+                except KeyError: pass
+        return result
+
+    rstr = __str__
+
+    memoizer_counters.append(SCons.Memoize.CountValue('stat'))
+
+    def stat(self):
+        try: return self._memo['stat']
+        except KeyError: pass
+        try: result = self.fs.stat(self.abspath)
+        except os.error: result = None
+        self._memo['stat'] = result
+        return result
+
+    def exists(self):
+        return self.stat() is not None
+
+    def rexists(self):
+        return self.rfile().exists()
+
+    def getmtime(self):
+        st = self.stat()
+        if st: return st[stat.ST_MTIME]
+        else: return None
+
+    def getsize(self):
+        st = self.stat()
+        if st: return st[stat.ST_SIZE]
+        else: return None
+
+    def isdir(self):
+        st = self.stat()
+        return st is not None and stat.S_ISDIR(st[stat.ST_MODE])
+
+    def isfile(self):
+        st = self.stat()
+        return st is not None and stat.S_ISREG(st[stat.ST_MODE])
+
+    if hasattr(os, 'symlink'):
+        def islink(self):
+            try: st = self.fs.lstat(self.abspath)
+            except os.error: return 0
+            return stat.S_ISLNK(st[stat.ST_MODE])
+    else:
+        def islink(self):
+            return 0                    # no symlinks
+
+    def is_under(self, dir):
+        if self is dir:
+            return 1
+        else:
+            return self.dir.is_under(dir)
+
+    def set_local(self):
+        self._local = 1
+
+    def srcnode(self):
+        """If this node is in a build path, return the node
+        corresponding to its source file.  Otherwise, return
+        ourself.
+        """
+        srcdir_list = self.dir.srcdir_list()
+        if srcdir_list:
+            srcnode = srcdir_list[0].Entry(self.name)
+            srcnode.must_be_same(self.__class__)
+            return srcnode
+        return self
+
+    def get_path(self, dir=None):
+        """Return path relative to the current working directory of the
+        Node.FS.Base object that owns us."""
+        if not dir:
+            dir = self.fs.getcwd()
+        if self == dir:
+            return '.'
+        path_elems = self.path_elements
+        try: i = path_elems.index(dir)
+        except ValueError: pass
+        else: path_elems = path_elems[i+1:]
+        path_elems = [n.name for n in path_elems]
+        return os.sep.join(path_elems)
+
+    def set_src_builder(self, builder):
+        """Set the source code builder for this node."""
+        self.sbuilder = builder
+        if not self.has_builder():
+            self.builder_set(builder)
+
+    def src_builder(self):
+        """Fetch the source code builder for this node.
+
+        If there isn't one, we cache the source code builder specified
+        for the directory (which in turn will cache the value from its
+        parent directory, and so on up to the file system root).
+        """
+        try:
+            scb = self.sbuilder
+        except AttributeError:
+            scb = self.dir.src_builder()
+            self.sbuilder = scb
+        return scb
+
+    def get_abspath(self):
+        """Get the absolute path of the file."""
+        return self.abspath
+
+    def for_signature(self):
+        # Return just our name.  Even an absolute path would not work,
+        # because that can change thanks to symlinks or remapped network
+        # paths.
+        return self.name
+
+    def get_subst_proxy(self):
+        try:
+            return self._proxy
+        except AttributeError:
+            ret = EntryProxy(self)
+            self._proxy = ret
+            return ret
+
+    def target_from_source(self, prefix, suffix, splitext=SCons.Util.splitext):
+        """
+
+        Generates a target entry that corresponds to this entry (usually
+        a source file) with the specified prefix and suffix.
+
+        Note that this method can be overridden dynamically for generated
+        files that need different behavior.  See Tool/swig.py for
+        an example.
+        """
+        return self.dir.Entry(prefix + splitext(self.name)[0] + suffix)
+
+    def _Rfindalldirs_key(self, pathlist):
+        return pathlist
+
+    memoizer_counters.append(SCons.Memoize.CountDict('Rfindalldirs', _Rfindalldirs_key))
+
+    def Rfindalldirs(self, pathlist):
+        """
+        Return all of the directories for a given path list, including
+        corresponding "backing" directories in any repositories.
+
+        The Node lookups are relative to this Node (typically a
+        directory), so memoizing result saves cycles from looking
+        up the same path for each target in a given directory.
+        """
+        try:
+            memo_dict = self._memo['Rfindalldirs']
+        except KeyError:
+            memo_dict = {}
+            self._memo['Rfindalldirs'] = memo_dict
+        else:
+            try:
+                return memo_dict[pathlist]
+            except KeyError:
+                pass
+
+        create_dir_relative_to_self = self.Dir
+        result = []
+        for path in pathlist:
+            if isinstance(path, SCons.Node.Node):
+                result.append(path)
+            else:
+                dir = create_dir_relative_to_self(path)
+                result.extend(dir.get_all_rdirs())
+
+        memo_dict[pathlist] = result
+
+        return result
+
+    def RDirs(self, pathlist):
+        """Search for a list of directories in the Repository list."""
+        cwd = self.cwd or self.fs._cwd
+        return cwd.Rfindalldirs(pathlist)
+
+    memoizer_counters.append(SCons.Memoize.CountValue('rentry'))
+
+    def rentry(self):
+        try:
+            return self._memo['rentry']
+        except KeyError:
+            pass
+        result = self
+        if not self.exists():
+            norm_name = _my_normcase(self.name)
+            for dir in self.dir.get_all_rdirs():
+                try:
+                    node = dir.entries[norm_name]
+                except KeyError:
+                    if dir.entry_exists_on_disk(self.name):
+                        result = dir.Entry(self.name)
+                        break
+        self._memo['rentry'] = result
+        return result
+
+    def _glob1(self, pattern, ondisk=True, source=False, strings=False):
+        return []
+
+class Entry(Base):
+    """This is the class for generic Node.FS entries--that is, things
+    that could be a File or a Dir, but we're just not sure yet.
+    Consequently, the methods in this class really exist just to
+    transform their associated object into the right class when the
+    time comes, and then call the same-named method in the transformed
+    class."""
+
+    def diskcheck_match(self):
+        pass
+
+    def disambiguate(self, must_exist=None):
+        """
+        """
+        if self.isdir():
+            self.__class__ = Dir
+            self._morph()
+        elif self.isfile():
+            self.__class__ = File
+            self._morph()
+            self.clear()
+        else:
+            # There was nothing on-disk at this location, so look in
+            # the src directory.
+            #
+            # We can't just use self.srcnode() straight away because
+            # that would create an actual Node for this file in the src
+            # directory, and there might not be one.  Instead, use the
+            # dir_on_disk() method to see if there's something on-disk
+            # with that name, in which case we can go ahead and call
+            # self.srcnode() to create the right type of entry.
+            srcdir = self.dir.srcnode()
+            if srcdir != self.dir and \
+               srcdir.entry_exists_on_disk(self.name) and \
+               self.srcnode().isdir():
+                self.__class__ = Dir
+                self._morph()
+            elif must_exist:
+                msg = "No such file or directory: '%s'" % self.abspath
+                raise SCons.Errors.UserError(msg)
+            else:
+                self.__class__ = File
+                self._morph()
+                self.clear()
+        return self
+
+    def rfile(self):
+        """We're a generic Entry, but the caller is actually looking for
+        a File at this point, so morph into one."""
+        self.__class__ = File
+        self._morph()
+        self.clear()
+        return File.rfile(self)
+
+    def scanner_key(self):
+        return self.get_suffix()
+
+    def get_contents(self):
+        """Fetch the contents of the entry.  Returns the exact binary
+        contents of the file."""
+        try:
+            self = self.disambiguate(must_exist=1)
+        except SCons.Errors.UserError:
+            # There was nothing on disk with which to disambiguate
+            # this entry.  Leave it as an Entry, but return a null
+            # string so calls to get_contents() in emitters and the
+            # like (e.g. in qt.py) don't have to disambiguate by hand
+            # or catch the exception.
+            return ''
+        else:
+            return self.get_contents()
+
+    def get_text_contents(self):
+        """Fetch the decoded text contents of a Unicode encoded Entry.
+
+        Since this should return the text contents from the file
+        system, we check to see into what sort of subclass we should
+        morph this Entry."""
+        try:
+            self = self.disambiguate(must_exist=1)
+        except SCons.Errors.UserError:
+            # There was nothing on disk with which to disambiguate
+            # this entry.  Leave it as an Entry, but return a null
+            # string so calls to get_text_contents() in emitters and
+            # the like (e.g. in qt.py) don't have to disambiguate by
+            # hand or catch the exception.
+            return ''
+        else:
+            return self.get_text_contents()
+
+    def must_be_same(self, klass):
+        """Called to make sure a Node is a Dir.  Since we're an
+        Entry, we can morph into one."""
+        if self.__class__ is not klass:
+            self.__class__ = klass
+            self._morph()
+            self.clear()
+
+    # The following methods can get called before the Taskmaster has
+    # had a chance to call disambiguate() directly to see if this Entry
+    # should really be a Dir or a File.  We therefore use these to call
+    # disambiguate() transparently (from our caller's point of view).
+    #
+    # Right now, this minimal set of methods has been derived by just
+    # looking at some of the methods that will obviously be called early
+    # in any of the various Taskmasters' calling sequences, and then
+    # empirically figuring out which additional methods are necessary
+    # to make various tests pass.
+
+    def exists(self):
+        """Return if the Entry exists.  Check the file system to see
+        what we should turn into first.  Assume a file if there's no
+        directory."""
+        return self.disambiguate().exists()
+
+    def rel_path(self, other):
+        d = self.disambiguate()
+        if d.__class__ is Entry:
+            raise Exception("rel_path() could not disambiguate File/Dir")
+        return d.rel_path(other)
+
+    def new_ninfo(self):
+        return self.disambiguate().new_ninfo()
+
+    def changed_since_last_build(self, target, prev_ni):
+        return self.disambiguate().changed_since_last_build(target, prev_ni)
+
+    def _glob1(self, pattern, ondisk=True, source=False, strings=False):
+        return self.disambiguate()._glob1(pattern, ondisk, source, strings)
+
+    def get_subst_proxy(self):
+        return self.disambiguate().get_subst_proxy()
+
+# This is for later so we can differentiate between Entry the class and Entry
+# the method of the FS class.
+_classEntry = Entry
+
+
+class LocalFS(object):
+
+    if SCons.Memoize.use_memoizer:
+        __metaclass__ = SCons.Memoize.Memoized_Metaclass
+
+    # This class implements an abstraction layer for operations involving
+    # a local file system.  Essentially, this wraps any function in
+    # the os, os.path or shutil modules that we use to actually go do
+    # anything with or to the local file system.
+    #
+    # Note that there's a very good chance we'll refactor this part of
+    # the architecture in some way as we really implement the interface(s)
+    # for remote file system Nodes.  For example, the right architecture
+    # might be to have this be a subclass instead of a base class.
+    # Nevertheless, we're using this as a first step in that direction.
+    #
+    # We're not using chdir() yet because the calling subclass method
+    # needs to use os.chdir() directly to avoid recursion.  Will we
+    # really need this one?
+    #def chdir(self, path):
+    #    return os.chdir(path)
+    def chmod(self, path, mode):
+        return os.chmod(path, mode)
+    def copy(self, src, dst):
+        return shutil.copy(src, dst)
+    def copy2(self, src, dst):
+        return shutil.copy2(src, dst)
+    def exists(self, path):
+        return os.path.exists(path)
+    def getmtime(self, path):
+        return os.path.getmtime(path)
+    def getsize(self, path):
+        return os.path.getsize(path)
+    def isdir(self, path):
+        return os.path.isdir(path)
+    def isfile(self, path):
+        return os.path.isfile(path)
+    def link(self, src, dst):
+        return os.link(src, dst)
+    def lstat(self, path):
+        return os.lstat(path)
+    def listdir(self, path):
+        return os.listdir(path)
+    def makedirs(self, path):
+        return os.makedirs(path)
+    def mkdir(self, path):
+        return os.mkdir(path)
+    def rename(self, old, new):
+        return os.rename(old, new)
+    def stat(self, path):
+        return os.stat(path)
+    def symlink(self, src, dst):
+        return os.symlink(src, dst)
+    def open(self, path):
+        return open(path)
+    def unlink(self, path):
+        return os.unlink(path)
+
+    if hasattr(os, 'symlink'):
+        def islink(self, path):
+            return os.path.islink(path)
+    else:
+        def islink(self, path):
+            return 0                    # no symlinks
+
+    if hasattr(os, 'readlink'):
+        def readlink(self, file):
+            return os.readlink(file)
+    else:
+        def readlink(self, file):
+            return ''
+
+
+#class RemoteFS:
+#    # Skeleton for the obvious methods we might need from the
+#    # abstraction layer for a remote filesystem.
+#    def upload(self, local_src, remote_dst):
+#        pass
+#    def download(self, remote_src, local_dst):
+#        pass
+
+
+class FS(LocalFS):
+
+    memoizer_counters = []
+
+    def __init__(self, path = None):
+        """Initialize the Node.FS subsystem.
+
+        The supplied path is the top of the source tree, where we
+        expect to find the top-level build file.  If no path is
+        supplied, the current directory is the default.
+
+        The path argument must be a valid absolute path.
+        """
+        if __debug__: logInstanceCreation(self, 'Node.FS')
+
+        self._memo = {}
+
+        self.Root = {}
+        self.SConstruct_dir = None
+        self.max_drift = default_max_drift
+
+        self.Top = None
+        if path is None:
+            self.pathTop = os.getcwd()
+        else:
+            self.pathTop = path
+        self.defaultDrive = _my_normcase(os.path.splitdrive(self.pathTop)[0])
+
+        self.Top = self.Dir(self.pathTop)
+        self.Top.path = '.'
+        self.Top.tpath = '.'
+        self._cwd = self.Top
+
+        DirNodeInfo.fs = self
+        FileNodeInfo.fs = self
+    
+    def set_SConstruct_dir(self, dir):
+        self.SConstruct_dir = dir
+
+    def get_max_drift(self):
+        return self.max_drift
+
+    def set_max_drift(self, max_drift):
+        self.max_drift = max_drift
+
+    def getcwd(self):
+        return self._cwd
+
+    def chdir(self, dir, change_os_dir=0):
+        """Change the current working directory for lookups.
+        If change_os_dir is true, we will also change the "real" cwd
+        to match.
+        """
+        curr=self._cwd
+        try:
+            if dir is not None:
+                self._cwd = dir
+                if change_os_dir:
+                    os.chdir(dir.abspath)
+        except OSError:
+            self._cwd = curr
+            raise
+
+    def get_root(self, drive):
+        """
+        Returns the root directory for the specified drive, creating
+        it if necessary.
+        """
+        drive = _my_normcase(drive)
+        try:
+            return self.Root[drive]
+        except KeyError:
+            root = RootDir(drive, self)
+            self.Root[drive] = root
+            if not drive:
+                self.Root[self.defaultDrive] = root
+            elif drive == self.defaultDrive:
+                self.Root[''] = root
+            return root
+
+    def _lookup(self, p, directory, fsclass, create=1):
+        """
+        The generic entry point for Node lookup with user-supplied data.
+
+        This translates arbitrary input into a canonical Node.FS object
+        of the specified fsclass.  The general approach for strings is
+        to turn it into a fully normalized absolute path and then call
+        the root directory's lookup_abs() method for the heavy lifting.
+
+        If the path name begins with '#', it is unconditionally
+        interpreted relative to the top-level directory of this FS.  '#'
+        is treated as a synonym for the top-level SConstruct directory,
+        much like '~' is treated as a synonym for the user's home
+        directory in a UNIX shell.  So both '#foo' and '#/foo' refer
+        to the 'foo' subdirectory underneath the top-level SConstruct
+        directory.
+
+        If the path name is relative, then the path is looked up relative
+        to the specified directory, or the current directory (self._cwd,
+        typically the SConscript directory) if the specified directory
+        is None.
+        """
+        if isinstance(p, Base):
+            # It's already a Node.FS object.  Make sure it's the right
+            # class and return.
+            p.must_be_same(fsclass)
+            return p
+        # str(p) in case it's something like a proxy object
+        p = str(p)
+
+        initial_hash = (p[0:1] == '#')
+        if initial_hash:
+            # There was an initial '#', so we strip it and override
+            # whatever directory they may have specified with the
+            # top-level SConstruct directory.
+            p = p[1:]
+            directory = self.Top
+
+        if directory and not isinstance(directory, Dir):
+            directory = self.Dir(directory)
+
+        if do_splitdrive:
+            drive, p = os.path.splitdrive(p)
+        else:
+            drive = ''
+        if drive and not p:
+            # This causes a naked drive letter to be treated as a synonym
+            # for the root directory on that drive.
+            p = os.sep
+        absolute = os.path.isabs(p)
+
+        needs_normpath = needs_normpath_check.match(p)
+
+        if initial_hash or not absolute:
+            # This is a relative lookup, either to the top-level
+            # SConstruct directory (because of the initial '#') or to
+            # the current directory (the path name is not absolute).
+            # Add the string to the appropriate directory lookup path,
+            # after which the whole thing gets normalized.
+            if not directory:
+                directory = self._cwd
+            if p:
+                p = directory.labspath + '/' + p
+            else:
+                p = directory.labspath
+
+        if needs_normpath:
+            p = os.path.normpath(p)
+
+        if drive or absolute:
+            root = self.get_root(drive)
+        else:
+            if not directory:
+                directory = self._cwd
+            root = directory.root
+
+        if os.sep != '/':
+            p = p.replace(os.sep, '/')
+        return root._lookup_abs(p, fsclass, create)
+
+    def Entry(self, name, directory = None, create = 1):
+        """Look up or create a generic Entry node with the specified name.
+        If the name is a relative path (begins with ./, ../, or a file
+        name), then it is looked up relative to the supplied directory
+        node, or to the top level directory of the FS (supplied at
+        construction time) if no directory is supplied.
+        """
+        return self._lookup(name, directory, Entry, create)
+
+    def File(self, name, directory = None, create = 1):
+        """Look up or create a File node with the specified name.  If
+        the name is a relative path (begins with ./, ../, or a file name),
+        then it is looked up relative to the supplied directory node,
+        or to the top level directory of the FS (supplied at construction
+        time) if no directory is supplied.
+
+        This method will raise TypeError if a directory is found at the
+        specified path.
+        """
+        return self._lookup(name, directory, File, create)
+
+    def Dir(self, name, directory = None, create = True):
+        """Look up or create a Dir node with the specified name.  If
+        the name is a relative path (begins with ./, ../, or a file name),
+        then it is looked up relative to the supplied directory node,
+        or to the top level directory of the FS (supplied at construction
+        time) if no directory is supplied.
+
+        This method will raise TypeError if a normal file is found at the
+        specified path.
+        """
+        return self._lookup(name, directory, Dir, create)
+
+    def VariantDir(self, variant_dir, src_dir, duplicate=1):
+        """Link the supplied variant directory to the source directory
+        for purposes of building files."""
+
+        if not isinstance(src_dir, SCons.Node.Node):
+            src_dir = self.Dir(src_dir)
+        if not isinstance(variant_dir, SCons.Node.Node):
+            variant_dir = self.Dir(variant_dir)
+        if src_dir.is_under(variant_dir):
+            raise SCons.Errors.UserError("Source directory cannot be under variant directory.")
+        if variant_dir.srcdir:
+            if variant_dir.srcdir == src_dir:
+                return # We already did this.
+            raise SCons.Errors.UserError("'%s' already has a source directory: '%s'."%(variant_dir, variant_dir.srcdir))
+        variant_dir.link(src_dir, duplicate)
+
+    def Repository(self, *dirs):
+        """Specify Repository directories to search."""
+        for d in dirs:
+            if not isinstance(d, SCons.Node.Node):
+                d = self.Dir(d)
+            self.Top.addRepository(d)
+
+    def variant_dir_target_climb(self, orig, dir, tail):
+        """Create targets in corresponding variant directories
+
+        Climb the directory tree, and look up path names
+        relative to any linked variant directories we find.
+
+        Even though this loops and walks up the tree, we don't memoize
+        the return value because this is really only used to process
+        the command-line targets.
+        """
+        targets = []
+        message = None
+        fmt = "building associated VariantDir targets: %s"
+        start_dir = dir
+        while dir:
+            for bd in dir.variant_dirs:
+                if start_dir.is_under(bd):
+                    # If already in the build-dir location, don't reflect
+                    return [orig], fmt % str(orig)
+                p = os.path.join(bd.path, *tail)
+                targets.append(self.Entry(p))
+            tail = [dir.name] + tail
+            dir = dir.up()
+        if targets:
+            message = fmt % ' '.join(map(str, targets))
+        return targets, message
+
+    def Glob(self, pathname, ondisk=True, source=True, strings=False, cwd=None):
+        """
+        Globs
+
+        This is mainly a shim layer 
+        """
+        if cwd is None:
+            cwd = self.getcwd()
+        return cwd.glob(pathname, ondisk, source, strings)
+
+class DirNodeInfo(SCons.Node.NodeInfoBase):
+    # This should get reset by the FS initialization.
+    current_version_id = 1
+
+    fs = None
+
+    def str_to_node(self, s):
+        top = self.fs.Top
+        root = top.root
+        if do_splitdrive:
+            drive, s = os.path.splitdrive(s)
+            if drive:
+                root = self.fs.get_root(drive)
+        if not os.path.isabs(s):
+            s = top.labspath + '/' + s
+        return root._lookup_abs(s, Entry)
+
+class DirBuildInfo(SCons.Node.BuildInfoBase):
+    current_version_id = 1
+
+glob_magic_check = re.compile('[*?[]')
+
+def has_glob_magic(s):
+    return glob_magic_check.search(s) is not None
+
+class Dir(Base):
+    """A class for directories in a file system.
+    """
+
+    memoizer_counters = []
+
+    NodeInfo = DirNodeInfo
+    BuildInfo = DirBuildInfo
+
+    def __init__(self, name, directory, fs):
+        if __debug__: logInstanceCreation(self, 'Node.FS.Dir')
+        Base.__init__(self, name, directory, fs)
+        self._morph()
+
+    def _morph(self):
+        """Turn a file system Node (either a freshly initialized directory
+        object or a separate Entry object) into a proper directory object.
+
+        Set up this directory's entries and hook it into the file
+        system tree.  Specify that directories (this Node) don't use
+        signatures for calculating whether they're current.
+        """
+
+        self.repositories = []
+        self.srcdir = None
+
+        self.entries = {}
+        self.entries['.'] = self
+        self.entries['..'] = self.dir
+        self.cwd = self
+        self.searched = 0
+        self._sconsign = None
+        self.variant_dirs = []
+        self.root = self.dir.root
+
+        # Don't just reset the executor, replace its action list,
+        # because it might have some pre-or post-actions that need to
+        # be preserved.
+        self.builder = get_MkdirBuilder()
+        self.get_executor().set_action_list(self.builder.action)
+
+    def diskcheck_match(self):
+        diskcheck_match(self, self.isfile,
+                        "File %s found where directory expected.")
+
+    def __clearRepositoryCache(self, duplicate=None):
+        """Called when we change the repository(ies) for a directory.
+        This clears any cached information that is invalidated by changing
+        the repository."""
+
+        for node in self.entries.values():
+            if node != self.dir:
+                if node != self and isinstance(node, Dir):
+                    node.__clearRepositoryCache(duplicate)
+                else:
+                    node.clear()
+                    try:
+                        del node._srcreps
+                    except AttributeError:
+                        pass
+                    if duplicate is not None:
+                        node.duplicate=duplicate
+
+    def __resetDuplicate(self, node):
+        if node != self:
+            node.duplicate = node.get_dir().duplicate
+
+    def Entry(self, name):
+        """
+        Looks up or creates an entry node named 'name' relative to
+        this directory.
+        """
+        return self.fs.Entry(name, self)
+
+    def Dir(self, name, create=True):
+        """
+        Looks up or creates a directory node named 'name' relative to
+        this directory.
+        """
+        return self.fs.Dir(name, self, create)
+
+    def File(self, name):
+        """
+        Looks up or creates a file node named 'name' relative to
+        this directory.
+        """
+        return self.fs.File(name, self)
+
+    def _lookup_rel(self, name, klass, create=1):
+        """
+        Looks up a *normalized* relative path name, relative to this
+        directory.
+
+        This method is intended for use by internal lookups with
+        already-normalized path data.  For general-purpose lookups,
+        use the Entry(), Dir() and File() methods above.
+
+        This method does *no* input checking and will die or give
+        incorrect results if it's passed a non-normalized path name (e.g.,
+        a path containing '..'), an absolute path name, a top-relative
+        ('#foo') path name, or any kind of object.
+        """
+        name = self.entry_labspath(name)
+        return self.root._lookup_abs(name, klass, create)
+
+    def link(self, srcdir, duplicate):
+        """Set this directory as the variant directory for the
+        supplied source directory."""
+        self.srcdir = srcdir
+        self.duplicate = duplicate
+        self.__clearRepositoryCache(duplicate)
+        srcdir.variant_dirs.append(self)
+
+    def getRepositories(self):
+        """Returns a list of repositories for this directory.
+        """
+        if self.srcdir and not self.duplicate:
+            return self.srcdir.get_all_rdirs() + self.repositories
+        return self.repositories
+
+    memoizer_counters.append(SCons.Memoize.CountValue('get_all_rdirs'))
+
+    def get_all_rdirs(self):
+        try:
+            return list(self._memo['get_all_rdirs'])
+        except KeyError:
+            pass
+
+        result = [self]
+        fname = '.'
+        dir = self
+        while dir:
+            for rep in dir.getRepositories():
+                result.append(rep.Dir(fname))
+            if fname == '.':
+                fname = dir.name
+            else:
+                fname = dir.name + os.sep + fname
+            dir = dir.up()
+
+        self._memo['get_all_rdirs'] = list(result)
+
+        return result
+
+    def addRepository(self, dir):
+        if dir != self and not dir in self.repositories:
+            self.repositories.append(dir)
+            dir.tpath = '.'
+            self.__clearRepositoryCache()
+
+    def up(self):
+        return self.entries['..']
+
+    def _rel_path_key(self, other):
+        return str(other)
+
+    memoizer_counters.append(SCons.Memoize.CountDict('rel_path', _rel_path_key))
+
+    def rel_path(self, other):
+        """Return a path to "other" relative to this directory.
+        """
+
+        # This complicated and expensive method, which constructs relative
+        # paths between arbitrary Node.FS objects, is no longer used
+        # by SCons itself.  It was introduced to store dependency paths
+        # in .sconsign files relative to the target, but that ended up
+        # being significantly inefficient.
+        #
+        # We're continuing to support the method because some SConstruct
+        # files out there started using it when it was available, and
+        # we're all about backwards compatibility..
+
+        try:
+            memo_dict = self._memo['rel_path']
+        except KeyError:
+            memo_dict = {}
+            self._memo['rel_path'] = memo_dict
+        else:
+            try:
+                return memo_dict[other]
+            except KeyError:
+                pass
+
+        if self is other:
+            result = '.'
+
+        elif not other in self.path_elements:
+            try:
+                other_dir = other.get_dir()
+            except AttributeError:
+                result = str(other)
+            else:
+                if other_dir is None:
+                    result = other.name
+                else:
+                    dir_rel_path = self.rel_path(other_dir)
+                    if dir_rel_path == '.':
+                        result = other.name
+                    else:
+                        result = dir_rel_path + os.sep + other.name
+        else:
+            i = self.path_elements.index(other) + 1
+
+            path_elems = ['..'] * (len(self.path_elements) - i) \
+                         + [n.name for n in other.path_elements[i:]]
+             
+            result = os.sep.join(path_elems)
+
+        memo_dict[other] = result
+
+        return result
+
+    def get_env_scanner(self, env, kw={}):
+        import SCons.Defaults
+        return SCons.Defaults.DirEntryScanner
+
+    def get_target_scanner(self):
+        import SCons.Defaults
+        return SCons.Defaults.DirEntryScanner
+
+    def get_found_includes(self, env, scanner, path):
+        """Return this directory's implicit dependencies.
+
+        We don't bother caching the results because the scan typically
+        shouldn't be requested more than once (as opposed to scanning
+        .h file contents, which can be requested as many times as the
+        files is #included by other files).
+        """
+        if not scanner:
+            return []
+        # Clear cached info for this Dir.  If we already visited this
+        # directory on our walk down the tree (because we didn't know at
+        # that point it was being used as the source for another Node)
+        # then we may have calculated build signature before realizing
+        # we had to scan the disk.  Now that we have to, though, we need
+        # to invalidate the old calculated signature so that any node
+        # dependent on our directory structure gets one that includes
+        # info about everything on disk.
+        self.clear()
+        return scanner(self, env, path)
+
+    #
+    # Taskmaster interface subsystem
+    #
+
+    def prepare(self):
+        pass
+
+    def build(self, **kw):
+        """A null "builder" for directories."""
+        global MkdirBuilder
+        if self.builder is not MkdirBuilder:
+            SCons.Node.Node.build(self, **kw)
+
+    #
+    #
+    #
+
+    def _create(self):
+        """Create this directory, silently and without worrying about
+        whether the builder is the default or not."""
+        listDirs = []
+        parent = self
+        while parent:
+            if parent.exists():
+                break
+            listDirs.append(parent)
+            p = parent.up()
+            if p is None:
+                # Don't use while: - else: for this condition because
+                # if so, then parent is None and has no .path attribute.
+                raise SCons.Errors.StopError(parent.path)
+            parent = p
+        listDirs.reverse()
+        for dirnode in listDirs:
+            try:
+                # Don't call dirnode.build(), call the base Node method
+                # directly because we definitely *must* create this
+                # directory.  The dirnode.build() method will suppress
+                # the build if it's the default builder.
+                SCons.Node.Node.build(dirnode)
+                dirnode.get_executor().nullify()
+                # The build() action may or may not have actually
+                # created the directory, depending on whether the -n
+                # option was used or not.  Delete the _exists and
+                # _rexists attributes so they can be reevaluated.
+                dirnode.clear()
+            except OSError:
+                pass
+
+    def multiple_side_effect_has_builder(self):
+        global MkdirBuilder
+        return self.builder is not MkdirBuilder and self.has_builder()
+
+    def alter_targets(self):
+        """Return any corresponding targets in a variant directory.
+        """
+        return self.fs.variant_dir_target_climb(self, self, [])
+
+    def scanner_key(self):
+        """A directory does not get scanned."""
+        return None
+
+    def get_text_contents(self):
+        """We already emit things in text, so just return the binary
+        version."""
+        return self.get_contents()
+
+    def get_contents(self):
+        """Return content signatures and names of all our children
+        separated by new-lines. Ensure that the nodes are sorted."""
+        contents = []
+        for node in sorted(self.children(), key=lambda t: t.name):
+            contents.append('%s %s\n' % (node.get_csig(), node.name))
+        return ''.join(contents)
+
+    def get_csig(self):
+        """Compute the content signature for Directory nodes. In
+        general, this is not needed and the content signature is not
+        stored in the DirNodeInfo. However, if get_contents on a Dir
+        node is called which has a child directory, the child
+        directory should return the hash of its contents."""
+        contents = self.get_contents()
+        return SCons.Util.MD5signature(contents)
+
+    def do_duplicate(self, src):
+        pass
+
+    changed_since_last_build = SCons.Node.Node.state_has_changed
+
+    def is_up_to_date(self):
+        """If any child is not up-to-date, then this directory isn't,
+        either."""
+        if self.builder is not MkdirBuilder and not self.exists():
+            return 0
+        up_to_date = SCons.Node.up_to_date
+        for kid in self.children():
+            if kid.get_state() > up_to_date:
+                return 0
+        return 1
+
+    def rdir(self):
+        if not self.exists():
+            norm_name = _my_normcase(self.name)
+            for dir in self.dir.get_all_rdirs():
+                try: node = dir.entries[norm_name]
+                except KeyError: node = dir.dir_on_disk(self.name)
+                if node and node.exists() and \
+                    (isinstance(dir, Dir) or isinstance(dir, Entry)):
+                        return node
+        return self
+
+    def sconsign(self):
+        """Return the .sconsign file info for this directory,
+        creating it first if necessary."""
+        if not self._sconsign:
+            import SCons.SConsign
+            self._sconsign = SCons.SConsign.ForDirectory(self)
+        return self._sconsign
+
+    def srcnode(self):
+        """Dir has a special need for srcnode()...if we
+        have a srcdir attribute set, then that *is* our srcnode."""
+        if self.srcdir:
+            return self.srcdir
+        return Base.srcnode(self)
+
+    def get_timestamp(self):
+        """Return the latest timestamp from among our children"""
+        stamp = 0
+        for kid in self.children():
+            if kid.get_timestamp() > stamp:
+                stamp = kid.get_timestamp()
+        return stamp
+
+    def entry_abspath(self, name):
+        return self.abspath + os.sep + name
+
+    def entry_labspath(self, name):
+        return self.labspath + '/' + name
+
+    def entry_path(self, name):
+        return self.path + os.sep + name
+
+    def entry_tpath(self, name):
+        return self.tpath + os.sep + name
+
+    def entry_exists_on_disk(self, name):
+        try:
+            d = self.on_disk_entries
+        except AttributeError:
+            d = {}
+            try:
+                entries = os.listdir(self.abspath)
+            except OSError:
+                pass
+            else:
+                for entry in map(_my_normcase, entries):
+                    d[entry] = True
+            self.on_disk_entries = d
+        if sys.platform == 'win32':
+            name = _my_normcase(name)
+            result = d.get(name)
+            if result is None:
+                # Belt-and-suspenders for Windows:  check directly for
+                # 8.3 file names that don't show up in os.listdir().
+                result = os.path.exists(self.abspath + os.sep + name)
+                d[name] = result
+            return result
+        else:
+            return name in d
+
+    memoizer_counters.append(SCons.Memoize.CountValue('srcdir_list'))
+
+    def srcdir_list(self):
+        try:
+            return self._memo['srcdir_list']
+        except KeyError:
+            pass
+
+        result = []
+
+        dirname = '.'
+        dir = self
+        while dir:
+            if dir.srcdir:
+                result.append(dir.srcdir.Dir(dirname))
+            dirname = dir.name + os.sep + dirname
+            dir = dir.up()
+
+        self._memo['srcdir_list'] = result
+
+        return result
+
+    def srcdir_duplicate(self, name):
+        for dir in self.srcdir_list():
+            if self.is_under(dir):
+                # We shouldn't source from something in the build path;
+                # variant_dir is probably under src_dir, in which case
+                # we are reflecting.
+                break
+            if dir.entry_exists_on_disk(name):
+                srcnode = dir.Entry(name).disambiguate()
+                if self.duplicate:
+                    node = self.Entry(name).disambiguate()
+                    node.do_duplicate(srcnode)
+                    return node
+                else:
+                    return srcnode
+        return None
+
+    def _srcdir_find_file_key(self, filename):
+        return filename
+
+    memoizer_counters.append(SCons.Memoize.CountDict('srcdir_find_file', _srcdir_find_file_key))
+
+    def srcdir_find_file(self, filename):
+        try:
+            memo_dict = self._memo['srcdir_find_file']
+        except KeyError:
+            memo_dict = {}
+            self._memo['srcdir_find_file'] = memo_dict
+        else:
+            try:
+                return memo_dict[filename]
+            except KeyError:
+                pass
+
+        def func(node):
+            if (isinstance(node, File) or isinstance(node, Entry)) and \
+               (node.is_derived() or node.exists()):
+                    return node
+            return None
+
+        norm_name = _my_normcase(filename)
+
+        for rdir in self.get_all_rdirs():
+            try: node = rdir.entries[norm_name]
+            except KeyError: node = rdir.file_on_disk(filename)
+            else: node = func(node)
+            if node:
+                result = (node, self)
+                memo_dict[filename] = result
+                return result
+
+        for srcdir in self.srcdir_list():
+            for rdir in srcdir.get_all_rdirs():
+                try: node = rdir.entries[norm_name]
+                except KeyError: node = rdir.file_on_disk(filename)
+                else: node = func(node)
+                if node:
+                    result = (File(filename, self, self.fs), srcdir)
+                    memo_dict[filename] = result
+                    return result
+
+        result = (None, None)
+        memo_dict[filename] = result
+        return result
+
+    def dir_on_disk(self, name):
+        if self.entry_exists_on_disk(name):
+            try: return self.Dir(name)
+            except TypeError: pass
+        node = self.srcdir_duplicate(name)
+        if isinstance(node, File):
+            return None
+        return node
+
+    def file_on_disk(self, name):
+        if self.entry_exists_on_disk(name) or \
+           diskcheck_rcs(self, name) or \
+           diskcheck_sccs(self, name):
+            try: return self.File(name)
+            except TypeError: pass
+        node = self.srcdir_duplicate(name)
+        if isinstance(node, Dir):
+            return None
+        return node
+
+    def walk(self, func, arg):
+        """
+        Walk this directory tree by calling the specified function
+        for each directory in the tree.
+
+        This behaves like the os.path.walk() function, but for in-memory
+        Node.FS.Dir objects.  The function takes the same arguments as
+        the functions passed to os.path.walk():
+
+                func(arg, dirname, fnames)
+
+        Except that "dirname" will actually be the directory *Node*,
+        not the string.  The '.' and '..' entries are excluded from
+        fnames.  The fnames list may be modified in-place to filter the
+        subdirectories visited or otherwise impose a specific order.
+        The "arg" argument is always passed to func() and may be used
+        in any way (or ignored, passing None is common).
+        """
+        entries = self.entries
+        names = list(entries.keys())
+        names.remove('.')
+        names.remove('..')
+        func(arg, self, names)
+        for dirname in [n for n in names if isinstance(entries[n], Dir)]:
+            entries[dirname].walk(func, arg)
+
+    def glob(self, pathname, ondisk=True, source=False, strings=False):
+        """
+        Returns a list of Nodes (or strings) matching a specified
+        pathname pattern.
+
+        Pathname patterns follow UNIX shell semantics:  * matches
+        any-length strings of any characters, ? matches any character,
+        and [] can enclose lists or ranges of characters.  Matches do
+        not span directory separators.
+
+        The matches take into account Repositories, returning local
+        Nodes if a corresponding entry exists in a Repository (either
+        an in-memory Node or something on disk).
+
+        By defafult, the glob() function matches entries that exist
+        on-disk, in addition to in-memory Nodes.  Setting the "ondisk"
+        argument to False (or some other non-true value) causes the glob()
+        function to only match in-memory Nodes.  The default behavior is
+        to return both the on-disk and in-memory Nodes.
+
+        The "source" argument, when true, specifies that corresponding
+        source Nodes must be returned if you're globbing in a build
+        directory (initialized with VariantDir()).  The default behavior
+        is to return Nodes local to the VariantDir().
+
+        The "strings" argument, when true, returns the matches as strings,
+        not Nodes.  The strings are path names relative to this directory.
+
+        The underlying algorithm is adapted from the glob.glob() function
+        in the Python library (but heavily modified), and uses fnmatch()
+        under the covers.
+        """
+        dirname, basename = os.path.split(pathname)
+        if not dirname:
+            return sorted(self._glob1(basename, ondisk, source, strings),
+                          key=lambda t: str(t))
+        if has_glob_magic(dirname):
+            list = self.glob(dirname, ondisk, source, strings=False)
+        else:
+            list = [self.Dir(dirname, create=True)]
+        result = []
+        for dir in list:
+            r = dir._glob1(basename, ondisk, source, strings)
+            if strings:
+                r = [os.path.join(str(dir), x) for x in r]
+            result.extend(r)
+        return sorted(result, key=lambda a: str(a))
+
+    def _glob1(self, pattern, ondisk=True, source=False, strings=False):
+        """
+        Globs for and returns a list of entry names matching a single
+        pattern in this directory.
+
+        This searches any repositories and source directories for
+        corresponding entries and returns a Node (or string) relative
+        to the current directory if an entry is found anywhere.
+
+        TODO: handle pattern with no wildcard
+        """
+        search_dir_list = self.get_all_rdirs()
+        for srcdir in self.srcdir_list():
+            search_dir_list.extend(srcdir.get_all_rdirs())
+
+        selfEntry = self.Entry
+        names = []
+        for dir in search_dir_list:
+            # We use the .name attribute from the Node because the keys of
+            # the dir.entries dictionary are normalized (that is, all upper
+            # case) on case-insensitive systems like Windows.
+            node_names = [ v.name for k, v in dir.entries.items()
+                           if k not in ('.', '..') ]
+            names.extend(node_names)
+            if not strings:
+                # Make sure the working directory (self) actually has
+                # entries for all Nodes in repositories or variant dirs.
+                for name in node_names: selfEntry(name)
+            if ondisk:
+                try:
+                    disk_names = os.listdir(dir.abspath)
+                except os.error:
+                    continue
+                names.extend(disk_names)
+                if not strings:
+                    # We're going to return corresponding Nodes in
+                    # the local directory, so we need to make sure
+                    # those Nodes exist.  We only want to create
+                    # Nodes for the entries that will match the
+                    # specified pattern, though, which means we
+                    # need to filter the list here, even though
+                    # the overall list will also be filtered later,
+                    # after we exit this loop.
+                    if pattern[0] != '.':
+                        #disk_names = [ d for d in disk_names if d[0] != '.' ]
+                        disk_names = [x for x in disk_names if x[0] != '.']
+                    disk_names = fnmatch.filter(disk_names, pattern)
+                    dirEntry = dir.Entry
+                    for name in disk_names:
+                        # Add './' before disk filename so that '#' at
+                        # beginning of filename isn't interpreted.
+                        name = './' + name
+                        node = dirEntry(name).disambiguate()
+                        n = selfEntry(name)
+                        if n.__class__ != node.__class__:
+                            n.__class__ = node.__class__
+                            n._morph()
+
+        names = set(names)
+        if pattern[0] != '.':
+            #names = [ n for n in names if n[0] != '.' ]
+            names = [x for x in names if x[0] != '.']
+        names = fnmatch.filter(names, pattern)
+
+        if strings:
+            return names
+
+        #return [ self.entries[_my_normcase(n)] for n in names ]
+        return [self.entries[_my_normcase(n)] for n in names]
+
+class RootDir(Dir):
+    """A class for the root directory of a file system.
+
+    This is the same as a Dir class, except that the path separator
+    ('/' or '\\') is actually part of the name, so we don't need to
+    add a separator when creating the path names of entries within
+    this directory.
+    """
+    def __init__(self, name, fs):
+        if __debug__: logInstanceCreation(self, 'Node.FS.RootDir')
+        # We're going to be our own parent directory (".." entry and .dir
+        # attribute) so we have to set up some values so Base.__init__()
+        # won't gag won't it calls some of our methods.
+        self.abspath = ''
+        self.labspath = ''
+        self.path = ''
+        self.tpath = ''
+        self.path_elements = []
+        self.duplicate = 0
+        self.root = self
+        Base.__init__(self, name, self, fs)
+
+        # Now set our paths to what we really want them to be: the
+        # initial drive letter (the name) plus the directory separator,
+        # except for the "lookup abspath," which does not have the
+        # drive letter.
+        self.abspath = name + os.sep
+        self.labspath = ''
+        self.path = name + os.sep
+        self.tpath = name + os.sep
+        self._morph()
+
+        self._lookupDict = {}
+
+        # The // and os.sep + os.sep entries are necessary because
+        # os.path.normpath() seems to preserve double slashes at the
+        # beginning of a path (presumably for UNC path names), but
+        # collapses triple slashes to a single slash.
+        self._lookupDict[''] = self
+        self._lookupDict['/'] = self
+        self._lookupDict['//'] = self
+        self._lookupDict[os.sep] = self
+        self._lookupDict[os.sep + os.sep] = self
+
+    def must_be_same(self, klass):
+        if klass is Dir:
+            return
+        Base.must_be_same(self, klass)
+
+    def _lookup_abs(self, p, klass, create=1):
+        """
+        Fast (?) lookup of a *normalized* absolute path.
+
+        This method is intended for use by internal lookups with
+        already-normalized path data.  For general-purpose lookups,
+        use the FS.Entry(), FS.Dir() or FS.File() methods.
+
+        The caller is responsible for making sure we're passed a
+        normalized absolute path; we merely let Python's dictionary look
+        up and return the One True Node.FS object for the path.
+
+        If no Node for the specified "p" doesn't already exist, and
+        "create" is specified, the Node may be created after recursive
+        invocation to find or create the parent directory or directories.
+        """
+        k = _my_normcase(p)
+        try:
+            result = self._lookupDict[k]
+        except KeyError:
+            if not create:
+                msg = "No such file or directory: '%s' in '%s' (and create is False)" % (p, str(self))
+                raise SCons.Errors.UserError(msg)
+            # There is no Node for this path name, and we're allowed
+            # to create it.
+            dir_name, file_name = os.path.split(p)
+            dir_node = self._lookup_abs(dir_name, Dir)
+            result = klass(file_name, dir_node, self.fs)
+
+            # Double-check on disk (as configured) that the Node we
+            # created matches whatever is out there in the real world.
+            result.diskcheck_match()
+
+            self._lookupDict[k] = result
+            dir_node.entries[_my_normcase(file_name)] = result
+            dir_node.implicit = None
+        else:
+            # There is already a Node for this path name.  Allow it to
+            # complain if we were looking for an inappropriate type.
+            result.must_be_same(klass)
+        return result
+
+    def __str__(self):
+        return self.abspath
+
+    def entry_abspath(self, name):
+        return self.abspath + name
+
+    def entry_labspath(self, name):
+        return '/' + name
+
+    def entry_path(self, name):
+        return self.path + name
+
+    def entry_tpath(self, name):
+        return self.tpath + name
+
+    def is_under(self, dir):
+        if self is dir:
+            return 1
+        else:
+            return 0
+
+    def up(self):
+        return None
+
+    def get_dir(self):
+        return None
+
+    def src_builder(self):
+        return _null
+
+class FileNodeInfo(SCons.Node.NodeInfoBase):
+    current_version_id = 1
+
+    field_list = ['csig', 'timestamp', 'size']
+
+    # This should get reset by the FS initialization.
+    fs = None
+
+    def str_to_node(self, s):
+        top = self.fs.Top
+        root = top.root
+        if do_splitdrive:
+            drive, s = os.path.splitdrive(s)
+            if drive:
+                root = self.fs.get_root(drive)
+        if not os.path.isabs(s):
+            s = top.labspath + '/' + s
+        return root._lookup_abs(s, Entry)
+
+class FileBuildInfo(SCons.Node.BuildInfoBase):
+    current_version_id = 1
+
+    def convert_to_sconsign(self):
+        """
+        Converts this FileBuildInfo object for writing to a .sconsign file
+
+        This replaces each Node in our various dependency lists with its
+        usual string representation: relative to the top-level SConstruct
+        directory, or an absolute path if it's outside.
+        """
+        if os.sep == '/':
+            node_to_str = str
+        else:
+            def node_to_str(n):
+                try:
+                    s = n.path
+                except AttributeError:
+                    s = str(n)
+                else:
+                    s = s.replace(os.sep, '/')
+                return s
+        for attr in ['bsources', 'bdepends', 'bimplicit']:
+            try:
+                val = getattr(self, attr)
+            except AttributeError:
+                pass
+            else:
+                setattr(self, attr, list(map(node_to_str, val)))
+    def convert_from_sconsign(self, dir, name):
+        """
+        Converts a newly-read FileBuildInfo object for in-SCons use
+
+        For normal up-to-date checking, we don't have any conversion to
+        perform--but we're leaving this method here to make that clear.
+        """
+        pass
+    def prepare_dependencies(self):
+        """
+        Prepares a FileBuildInfo object for explaining what changed
+
+        The bsources, bdepends and bimplicit lists have all been
+        stored on disk as paths relative to the top-level SConstruct
+        directory.  Convert the strings to actual Nodes (for use by the
+        --debug=explain code and --implicit-cache).
+        """
+        attrs = [
+            ('bsources', 'bsourcesigs'),
+            ('bdepends', 'bdependsigs'),
+            ('bimplicit', 'bimplicitsigs'),
+        ]
+        for (nattr, sattr) in attrs:
+            try:
+                strings = getattr(self, nattr)
+                nodeinfos = getattr(self, sattr)
+            except AttributeError:
+                continue
+            nodes = []
+            for s, ni in zip(strings, nodeinfos):
+                if not isinstance(s, SCons.Node.Node):
+                    s = ni.str_to_node(s)
+                nodes.append(s)
+            setattr(self, nattr, nodes)
+    def format(self, names=0):
+        result = []
+        bkids = self.bsources + self.bdepends + self.bimplicit
+        bkidsigs = self.bsourcesigs + self.bdependsigs + self.bimplicitsigs
+        for bkid, bkidsig in zip(bkids, bkidsigs):
+            result.append(str(bkid) + ': ' +
+                          ' '.join(bkidsig.format(names=names)))
+        result.append('%s [%s]' % (self.bactsig, self.bact))
+        return '\n'.join(result)
+
+class File(Base):
+    """A class for files in a file system.
+    """
+
+    memoizer_counters = []
+
+    NodeInfo = FileNodeInfo
+    BuildInfo = FileBuildInfo
+
+    md5_chunksize = 64
+
+    def diskcheck_match(self):
+        diskcheck_match(self, self.isdir,
+                        "Directory %s found where file expected.")
+
+    def __init__(self, name, directory, fs):
+        if __debug__: logInstanceCreation(self, 'Node.FS.File')
+        Base.__init__(self, name, directory, fs)
+        self._morph()
+
+    def Entry(self, name):
+        """Create an entry node named 'name' relative to
+        the directory of this file."""
+        return self.dir.Entry(name)
+
+    def Dir(self, name, create=True):
+        """Create a directory node named 'name' relative to
+        the directory of this file."""
+        return self.dir.Dir(name, create=create)
+
+    def Dirs(self, pathlist):
+        """Create a list of directories relative to the SConscript
+        directory of this file."""
+        return [self.Dir(p) for p in pathlist]
+
+    def File(self, name):
+        """Create a file node named 'name' relative to
+        the directory of this file."""
+        return self.dir.File(name)
+
+    #def generate_build_dict(self):
+    #    """Return an appropriate dictionary of values for building
+    #    this File."""
+    #    return {'Dir' : self.Dir,
+    #            'File' : self.File,
+    #            'RDirs' : self.RDirs}
+
+    def _morph(self):
+        """Turn a file system node into a File object."""
+        self.scanner_paths = {}
+        if not hasattr(self, '_local'):
+            self._local = 0
+
+        # If there was already a Builder set on this entry, then
+        # we need to make sure we call the target-decider function,
+        # not the source-decider.  Reaching in and doing this by hand
+        # is a little bogus.  We'd prefer to handle this by adding
+        # an Entry.builder_set() method that disambiguates like the
+        # other methods, but that starts running into problems with the
+        # fragile way we initialize Dir Nodes with their Mkdir builders,
+        # yet still allow them to be overridden by the user.  Since it's
+        # not clear right now how to fix that, stick with what works
+        # until it becomes clear...
+        if self.has_builder():
+            self.changed_since_last_build = self.decide_target
+
+    def scanner_key(self):
+        return self.get_suffix()
+
+    def get_contents(self):
+        if not self.rexists():
+            return ''
+        fname = self.rfile().abspath
+        try:
+            contents = open(fname, "rb").read()
+        except EnvironmentError, e:
+            if not e.filename:
+                e.filename = fname
+            raise
+        return contents
+
+    # This attempts to figure out what the encoding of the text is
+    # based upon the BOM bytes, and then decodes the contents so that
+    # it's a valid python string.
+    def get_text_contents(self):
+        contents = self.get_contents()
+        # The behavior of various decode() methods and functions
+        # w.r.t. the initial BOM bytes is different for different
+        # encodings and/or Python versions.  ('utf-8' does not strip
+        # them, but has a 'utf-8-sig' which does; 'utf-16' seems to
+        # strip them; etc.)  Just sidestep all the complication by
+        # explicitly stripping the BOM before we decode().
+        if contents.startswith(codecs.BOM_UTF8):
+            return contents[len(codecs.BOM_UTF8):].decode('utf-8')
+        if contents.startswith(codecs.BOM_UTF16_LE):
+            return contents[len(codecs.BOM_UTF16_LE):].decode('utf-16-le')
+        if contents.startswith(codecs.BOM_UTF16_BE):
+            return contents[len(codecs.BOM_UTF16_BE):].decode('utf-16-be')
+        return contents
+
+    def get_content_hash(self):
+        """
+        Compute and return the MD5 hash for this file.
+        """
+        if not self.rexists():
+            return SCons.Util.MD5signature('')
+        fname = self.rfile().abspath
+        try:
+            cs = SCons.Util.MD5filesignature(fname,
+                chunksize=SCons.Node.FS.File.md5_chunksize*1024)
+        except EnvironmentError, e:
+            if not e.filename:
+                e.filename = fname
+            raise
+        return cs
+        
+
+    memoizer_counters.append(SCons.Memoize.CountValue('get_size'))
+
+    def get_size(self):
+        try:
+            return self._memo['get_size']
+        except KeyError:
+            pass
+
+        if self.rexists():
+            size = self.rfile().getsize()
+        else:
+            size = 0
+
+        self._memo['get_size'] = size
+
+        return size
+
+    memoizer_counters.append(SCons.Memoize.CountValue('get_timestamp'))
+
+    def get_timestamp(self):
+        try:
+            return self._memo['get_timestamp']
+        except KeyError:
+            pass
+
+        if self.rexists():
+            timestamp = self.rfile().getmtime()
+        else:
+            timestamp = 0
+
+        self._memo['get_timestamp'] = timestamp
+
+        return timestamp
+
+    def store_info(self):
+        # Merge our build information into the already-stored entry.
+        # This accomodates "chained builds" where a file that's a target
+        # in one build (SConstruct file) is a source in a different build.
+        # See test/chained-build.py for the use case.
+        if do_store_info:
+            self.dir.sconsign().store_info(self.name, self)
+
+    convert_copy_attrs = [
+        'bsources',
+        'bimplicit',
+        'bdepends',
+        'bact',
+        'bactsig',
+        'ninfo',
+    ]
+
+
+    convert_sig_attrs = [
+        'bsourcesigs',
+        'bimplicitsigs',
+        'bdependsigs',
+    ]
+
+    def convert_old_entry(self, old_entry):
+        # Convert a .sconsign entry from before the Big Signature
+        # Refactoring, doing what we can to convert its information
+        # to the new .sconsign entry format.
+        #
+        # The old format looked essentially like this:
+        #
+        #   BuildInfo
+        #       .ninfo (NodeInfo)
+        #           .bsig
+        #           .csig
+        #           .timestamp
+        #           .size
+        #       .bsources
+        #       .bsourcesigs ("signature" list)
+        #       .bdepends
+        #       .bdependsigs ("signature" list)
+        #       .bimplicit
+        #       .bimplicitsigs ("signature" list)
+        #       .bact
+        #       .bactsig
+        #
+        # The new format looks like this:
+        #
+        #   .ninfo (NodeInfo)
+        #       .bsig
+        #       .csig
+        #       .timestamp
+        #       .size
+        #   .binfo (BuildInfo)
+        #       .bsources
+        #       .bsourcesigs (NodeInfo list)
+        #           .bsig
+        #           .csig
+        #           .timestamp
+        #           .size
+        #       .bdepends
+        #       .bdependsigs (NodeInfo list)
+        #           .bsig
+        #           .csig
+        #           .timestamp
+        #           .size
+        #       .bimplicit
+        #       .bimplicitsigs (NodeInfo list)
+        #           .bsig
+        #           .csig
+        #           .timestamp
+        #           .size
+        #       .bact
+        #       .bactsig
+        #
+        # The basic idea of the new structure is that a NodeInfo always
+        # holds all available information about the state of a given Node
+        # at a certain point in time.  The various .b*sigs lists can just
+        # be a list of pointers to the .ninfo attributes of the different
+        # dependent nodes, without any copying of information until it's
+        # time to pickle it for writing out to a .sconsign file.
+        #
+        # The complicating issue is that the *old* format only stored one
+        # "signature" per dependency, based on however the *last* build
+        # was configured.  We don't know from just looking at it whether
+        # it was a build signature, a content signature, or a timestamp
+        # "signature".  Since we no longer use build signatures, the
+        # best we can do is look at the length and if it's thirty two,
+        # assume that it was (or might have been) a content signature.
+        # If it was actually a build signature, then it will cause a
+        # rebuild anyway when it doesn't match the new content signature,
+        # but that's probably the best we can do.
+        import SCons.SConsign
+        new_entry = SCons.SConsign.SConsignEntry()
+        new_entry.binfo = self.new_binfo()
+        binfo = new_entry.binfo
+        for attr in self.convert_copy_attrs:
+            try:
+                value = getattr(old_entry, attr)
+            except AttributeError:
+                continue
+            setattr(binfo, attr, value)
+            delattr(old_entry, attr)
+        for attr in self.convert_sig_attrs:
+            try:
+                sig_list = getattr(old_entry, attr)
+            except AttributeError:
+                continue
+            value = []
+            for sig in sig_list:
+                ninfo = self.new_ninfo()
+                if len(sig) == 32:
+                    ninfo.csig = sig
+                else:
+                    ninfo.timestamp = sig
+                value.append(ninfo)
+            setattr(binfo, attr, value)
+            delattr(old_entry, attr)
+        return new_entry
+
+    memoizer_counters.append(SCons.Memoize.CountValue('get_stored_info'))
+
+    def get_stored_info(self):
+        try:
+            return self._memo['get_stored_info']
+        except KeyError:
+            pass
+
+        try:
+            sconsign_entry = self.dir.sconsign().get_entry(self.name)
+        except (KeyError, EnvironmentError):
+            import SCons.SConsign
+            sconsign_entry = SCons.SConsign.SConsignEntry()
+            sconsign_entry.binfo = self.new_binfo()
+            sconsign_entry.ninfo = self.new_ninfo()
+        else:
+            if isinstance(sconsign_entry, FileBuildInfo):
+                # This is a .sconsign file from before the Big Signature
+                # Refactoring; convert it as best we can.
+                sconsign_entry = self.convert_old_entry(sconsign_entry)
+            try:
+                delattr(sconsign_entry.ninfo, 'bsig')
+            except AttributeError:
+                pass
+
+        self._memo['get_stored_info'] = sconsign_entry
+
+        return sconsign_entry
+
+    def get_stored_implicit(self):
+        binfo = self.get_stored_info().binfo
+        binfo.prepare_dependencies()
+        try: return binfo.bimplicit
+        except AttributeError: return None
+
+    def rel_path(self, other):
+        return self.dir.rel_path(other)
+
+    def _get_found_includes_key(self, env, scanner, path):
+        return (id(env), id(scanner), path)
+
+    memoizer_counters.append(SCons.Memoize.CountDict('get_found_includes', _get_found_includes_key))
+
+    def get_found_includes(self, env, scanner, path):
+        """Return the included implicit dependencies in this file.
+        Cache results so we only scan the file once per path
+        regardless of how many times this information is requested.
+        """
+        memo_key = (id(env), id(scanner), path)
+        try:
+            memo_dict = self._memo['get_found_includes']
+        except KeyError:
+            memo_dict = {}
+            self._memo['get_found_includes'] = memo_dict
+        else:
+            try:
+                return memo_dict[memo_key]
+            except KeyError:
+                pass
+
+        if scanner:
+            # result = [n.disambiguate() for n in scanner(self, env, path)]
+            result = scanner(self, env, path)
+            result = [N.disambiguate() for N in result]
+        else:
+            result = []
+
+        memo_dict[memo_key] = result
+
+        return result
+
+    def _createDir(self):
+        # ensure that the directories for this node are
+        # created.
+        self.dir._create()
+
+    def push_to_cache(self):
+        """Try to push the node into a cache
+        """
+        # This should get called before the Nodes' .built() method is
+        # called, which would clear the build signature if the file has
+        # a source scanner.
+        #
+        # We have to clear the local memoized values *before* we push
+        # the node to cache so that the memoization of the self.exists()
+        # return value doesn't interfere.
+        if self.nocache:
+            return
+        self.clear_memoized_values()
+        if self.exists():
+            self.get_build_env().get_CacheDir().push(self)
+
+    def retrieve_from_cache(self):
+        """Try to retrieve the node's content from a cache
+
+        This method is called from multiple threads in a parallel build,
+        so only do thread safe stuff here. Do thread unsafe stuff in
+        built().
+
+        Returns true iff the node was successfully retrieved.
+        """
+        if self.nocache:
+            return None
+        if not self.is_derived():
+            return None
+        return self.get_build_env().get_CacheDir().retrieve(self)
+
+    def visited(self):
+        if self.exists():
+            self.get_build_env().get_CacheDir().push_if_forced(self)
+
+        ninfo = self.get_ninfo()
+
+        csig = self.get_max_drift_csig()
+        if csig:
+            ninfo.csig = csig
+
+        ninfo.timestamp = self.get_timestamp()
+        ninfo.size      = self.get_size()
+
+        if not self.has_builder():
+            # This is a source file, but it might have been a target file
+            # in another build that included more of the DAG.  Copy
+            # any build information that's stored in the .sconsign file
+            # into our binfo object so it doesn't get lost.
+            old = self.get_stored_info()
+            self.get_binfo().__dict__.update(old.binfo.__dict__)
+
+        self.store_info()
+
+    def find_src_builder(self):
+        if self.rexists():
+            return None
+        scb = self.dir.src_builder()
+        if scb is _null:
+            if diskcheck_sccs(self.dir, self.name):
+                scb = get_DefaultSCCSBuilder()
+            elif diskcheck_rcs(self.dir, self.name):
+                scb = get_DefaultRCSBuilder()
+            else:
+                scb = None
+        if scb is not None:
+            try:
+                b = self.builder
+            except AttributeError:
+                b = None
+            if b is None:
+                self.builder_set(scb)
+        return scb
+
+    def has_src_builder(self):
+        """Return whether this Node has a source builder or not.
+
+        If this Node doesn't have an explicit source code builder, this
+        is where we figure out, on the fly, if there's a transparent
+        source code builder for it.
+
+        Note that if we found a source builder, we also set the
+        self.builder attribute, so that all of the methods that actually
+        *build* this file don't have to do anything different.
+        """
+        try:
+            scb = self.sbuilder
+        except AttributeError:
+            scb = self.sbuilder = self.find_src_builder()
+        return scb is not None
+
+    def alter_targets(self):
+        """Return any corresponding targets in a variant directory.
+        """
+        if self.is_derived():
+            return [], None
+        return self.fs.variant_dir_target_climb(self, self.dir, [self.name])
+
+    def _rmv_existing(self):
+        self.clear_memoized_values()
+        e = Unlink(self, [], None)
+        if isinstance(e, SCons.Errors.BuildError):
+            raise e
+
+    #
+    # Taskmaster interface subsystem
+    #
+
+    def make_ready(self):
+        self.has_src_builder()
+        self.get_binfo()
+
+    def prepare(self):
+        """Prepare for this file to be created."""
+        SCons.Node.Node.prepare(self)
+
+        if self.get_state() != SCons.Node.up_to_date:
+            if self.exists():
+                if self.is_derived() and not self.precious:
+                    self._rmv_existing()
+            else:
+                try:
+                    self._createDir()
+                except SCons.Errors.StopError, drive:
+                    desc = "No drive `%s' for target `%s'." % (drive, self)
+                    raise SCons.Errors.StopError(desc)
+
+    #
+    #
+    #
+
+    def remove(self):
+        """Remove this file."""
+        if self.exists() or self.islink():
+            self.fs.unlink(self.path)
+            return 1
+        return None
+
+    def do_duplicate(self, src):
+        self._createDir()
+        Unlink(self, None, None)
+        e = Link(self, src, None)
+        if isinstance(e, SCons.Errors.BuildError):
+            desc = "Cannot duplicate `%s' in `%s': %s." % (src.path, self.dir.path, e.errstr)
+            raise SCons.Errors.StopError(desc)
+        self.linked = 1
+        # The Link() action may or may not have actually
+        # created the file, depending on whether the -n
+        # option was used or not.  Delete the _exists and
+        # _rexists attributes so they can be reevaluated.
+        self.clear()
+
+    memoizer_counters.append(SCons.Memoize.CountValue('exists'))
+
+    def exists(self):
+        try:
+            return self._memo['exists']
+        except KeyError:
+            pass
+        # Duplicate from source path if we are set up to do this.
+        if self.duplicate and not self.is_derived() and not self.linked:
+            src = self.srcnode()
+            if src is not self:
+                # At this point, src is meant to be copied in a variant directory.
+                src = src.rfile()
+                if src.abspath != self.abspath:
+                    if src.exists():
+                        self.do_duplicate(src)
+                        # Can't return 1 here because the duplication might
+                        # not actually occur if the -n option is being used.
+                    else:
+                        # The source file does not exist.  Make sure no old
+                        # copy remains in the variant directory.
+                        if Base.exists(self) or self.islink():
+                            self.fs.unlink(self.path)
+                        # Return None explicitly because the Base.exists() call
+                        # above will have cached its value if the file existed.
+                        self._memo['exists'] = None
+                        return None
+        result = Base.exists(self)
+        self._memo['exists'] = result
+        return result
+
+    #
+    # SIGNATURE SUBSYSTEM
+    #
+
+    def get_max_drift_csig(self):
+        """
+        Returns the content signature currently stored for this node
+        if it's been unmodified longer than the max_drift value, or the
+        max_drift value is 0.  Returns None otherwise.
+        """
+        old = self.get_stored_info()
+        mtime = self.get_timestamp()
+
+        max_drift = self.fs.max_drift
+        if max_drift > 0:
+            if (time.time() - mtime) > max_drift:
+                try:
+                    n = old.ninfo
+                    if n.timestamp and n.csig and n.timestamp == mtime:
+                        return n.csig
+                except AttributeError:
+                    pass
+        elif max_drift == 0:
+            try:
+                return old.ninfo.csig
+            except AttributeError:
+                pass
+
+        return None
+
+    def get_csig(self):
+        """
+        Generate a node's content signature, the digested signature
+        of its content.
+
+        node - the node
+        cache - alternate node to use for the signature cache
+        returns - the content signature
+        """
+        ninfo = self.get_ninfo()
+        try:
+            return ninfo.csig
+        except AttributeError:
+            pass
+
+        csig = self.get_max_drift_csig()
+        if csig is None:
+
+            try:
+                if self.get_size() < SCons.Node.FS.File.md5_chunksize:
+                    contents = self.get_contents()
+                else:
+                    csig = self.get_content_hash()
+            except IOError:
+                # This can happen if there's actually a directory on-disk,
+                # which can be the case if they've disabled disk checks,
+                # or if an action with a File target actually happens to
+                # create a same-named directory by mistake.
+                csig = ''
+            else:
+                if not csig:
+                    csig = SCons.Util.MD5signature(contents)
+
+        ninfo.csig = csig
+
+        return csig
+
+    #
+    # DECISION SUBSYSTEM
+    #
+
+    def builder_set(self, builder):
+        SCons.Node.Node.builder_set(self, builder)
+        self.changed_since_last_build = self.decide_target
+
+    def changed_content(self, target, prev_ni):
+        cur_csig = self.get_csig()
+        try:
+            return cur_csig != prev_ni.csig
+        except AttributeError:
+            return 1
+
+    def changed_state(self, target, prev_ni):
+        return self.state != SCons.Node.up_to_date
+
+    def changed_timestamp_then_content(self, target, prev_ni):
+        if not self.changed_timestamp_match(target, prev_ni):
+            try:
+                self.get_ninfo().csig = prev_ni.csig
+            except AttributeError:
+                pass
+            return False
+        return self.changed_content(target, prev_ni)
+
+    def changed_timestamp_newer(self, target, prev_ni):
+        try:
+            return self.get_timestamp() > target.get_timestamp()
+        except AttributeError:
+            return 1
+
+    def changed_timestamp_match(self, target, prev_ni):
+        try:
+            return self.get_timestamp() != prev_ni.timestamp
+        except AttributeError:
+            return 1
+
+    def decide_source(self, target, prev_ni):
+        return target.get_build_env().decide_source(self, target, prev_ni)
+
+    def decide_target(self, target, prev_ni):
+        return target.get_build_env().decide_target(self, target, prev_ni)
+
+    # Initialize this Node's decider function to decide_source() because
+    # every file is a source file until it has a Builder attached...
+    changed_since_last_build = decide_source
+
+    def is_up_to_date(self):
+        T = 0
+        if T: Trace('is_up_to_date(%s):' % self)
+        if not self.exists():
+            if T: Trace(' not self.exists():')
+            # The file doesn't exist locally...
+            r = self.rfile()
+            if r != self:
+                # ...but there is one in a Repository...
+                if not self.changed(r):
+                    if T: Trace(' changed(%s):' % r)
+                    # ...and it's even up-to-date...
+                    if self._local:
+                        # ...and they'd like a local copy.
+                        e = LocalCopy(self, r, None)
+                        if isinstance(e, SCons.Errors.BuildError):
+                            raise 
+                        self.store_info()
+                    if T: Trace(' 1\n')
+                    return 1
+            self.changed()
+            if T: Trace(' None\n')
+            return None
+        else:
+            r = self.changed()
+            if T: Trace(' self.exists():  %s\n' % r)
+            return not r
+
+    memoizer_counters.append(SCons.Memoize.CountValue('rfile'))
+
+    def rfile(self):
+        try:
+            return self._memo['rfile']
+        except KeyError:
+            pass
+        result = self
+        if not self.exists():
+            norm_name = _my_normcase(self.name)
+            for dir in self.dir.get_all_rdirs():
+                try: node = dir.entries[norm_name]
+                except KeyError: node = dir.file_on_disk(self.name)
+                if node and node.exists() and \
+                   (isinstance(node, File) or isinstance(node, Entry) \
+                    or not node.is_derived()):
+                        result = node
+                        # Copy over our local attributes to the repository
+                        # Node so we identify shared object files in the
+                        # repository and don't assume they're static.
+                        #
+                        # This isn't perfect; the attribute would ideally
+                        # be attached to the object in the repository in
+                        # case it was built statically in the repository
+                        # and we changed it to shared locally, but that's
+                        # rarely the case and would only occur if you
+                        # intentionally used the same suffix for both
+                        # shared and static objects anyway.  So this
+                        # should work well in practice.
+                        result.attributes = self.attributes
+                        break
+        self._memo['rfile'] = result
+        return result
+
+    def rstr(self):
+        return str(self.rfile())
+
+    def get_cachedir_csig(self):
+        """
+        Fetch a Node's content signature for purposes of computing
+        another Node's cachesig.
+
+        This is a wrapper around the normal get_csig() method that handles
+        the somewhat obscure case of using CacheDir with the -n option.
+        Any files that don't exist would normally be "built" by fetching
+        them from the cache, but the normal get_csig() method will try
+        to open up the local file, which doesn't exist because the -n
+        option meant we didn't actually pull the file from cachedir.
+        But since the file *does* actually exist in the cachedir, we
+        can use its contents for the csig.
+        """
+        try:
+            return self.cachedir_csig
+        except AttributeError:
+            pass
+
+        cachedir, cachefile = self.get_build_env().get_CacheDir().cachepath(self)
+        if not self.exists() and cachefile and os.path.exists(cachefile):
+            self.cachedir_csig = SCons.Util.MD5filesignature(cachefile, \
+                SCons.Node.FS.File.md5_chunksize * 1024)
+        else:
+            self.cachedir_csig = self.get_csig()
+        return self.cachedir_csig
+
+    def get_cachedir_bsig(self):
+        try:
+            return self.cachesig
+        except AttributeError:
+            pass
+
+        # Add the path to the cache signature, because multiple
+        # targets built by the same action will all have the same
+        # build signature, and we have to differentiate them somehow.
+        children = self.children()
+        executor = self.get_executor()
+        # sigs = [n.get_cachedir_csig() for n in children]
+        sigs = [n.get_cachedir_csig() for n in children]
+        sigs.append(SCons.Util.MD5signature(executor.get_contents()))
+        sigs.append(self.path)
+        result = self.cachesig = SCons.Util.MD5collect(sigs)
+        return result
+
+
+default_fs = None
+
+def get_default_fs():
+    global default_fs
+    if not default_fs:
+        default_fs = FS()
+    return default_fs
+
+class FileFinder(object):
+    """
+    """
+    if SCons.Memoize.use_memoizer:
+        __metaclass__ = SCons.Memoize.Memoized_Metaclass
+
+    memoizer_counters = []
+
+    def __init__(self):
+        self._memo = {}
+
+    def filedir_lookup(self, p, fd=None):
+        """
+        A helper method for find_file() that looks up a directory for
+        a file we're trying to find.  This only creates the Dir Node if
+        it exists on-disk, since if the directory doesn't exist we know
+        we won't find any files in it...  :-)
+
+        It would be more compact to just use this as a nested function
+        with a default keyword argument (see the commented-out version
+        below), but that doesn't work unless you have nested scopes,
+        so we define it here just so this work under Python 1.5.2.
+        """
+        if fd is None:
+            fd = self.default_filedir
+        dir, name = os.path.split(fd)
+        drive, d = os.path.splitdrive(dir)
+        if not name and d[:1] in ('/', os.sep):
+            #return p.fs.get_root(drive).dir_on_disk(name)
+            return p.fs.get_root(drive)
+        if dir:
+            p = self.filedir_lookup(p, dir)
+            if not p:
+                return None
+        norm_name = _my_normcase(name)
+        try:
+            node = p.entries[norm_name]
+        except KeyError:
+            return p.dir_on_disk(name)
+        if isinstance(node, Dir):
+            return node
+        if isinstance(node, Entry):
+            node.must_be_same(Dir)
+            return node
+        return None
+
+    def _find_file_key(self, filename, paths, verbose=None):
+        return (filename, paths)
+        
+    memoizer_counters.append(SCons.Memoize.CountDict('find_file', _find_file_key))
+
+    def find_file(self, filename, paths, verbose=None):
+        """
+        find_file(str, [Dir()]) -> [nodes]
+
+        filename - a filename to find
+        paths - a list of directory path *nodes* to search in.  Can be
+                represented as a list, a tuple, or a callable that is
+                called with no arguments and returns the list or tuple.
+
+        returns - the node created from the found file.
+
+        Find a node corresponding to either a derived file or a file
+        that exists already.
+
+        Only the first file found is returned, and none is returned
+        if no file is found.
+        """
+        memo_key = self._find_file_key(filename, paths)
+        try:
+            memo_dict = self._memo['find_file']
+        except KeyError:
+            memo_dict = {}
+            self._memo['find_file'] = memo_dict
+        else:
+            try:
+                return memo_dict[memo_key]
+            except KeyError:
+                pass
+
+        if verbose and not callable(verbose):
+            if not SCons.Util.is_String(verbose):
+                verbose = "find_file"
+            _verbose = u'  %s: ' % verbose
+            verbose = lambda s: sys.stdout.write(_verbose + s)
+
+        filedir, filename = os.path.split(filename)
+        if filedir:
+            # More compact code that we can't use until we drop
+            # support for Python 1.5.2:
+            #
+            #def filedir_lookup(p, fd=filedir):
+            #    """
+            #    A helper function that looks up a directory for a file
+            #    we're trying to find.  This only creates the Dir Node
+            #    if it exists on-disk, since if the directory doesn't
+            #    exist we know we won't find any files in it...  :-)
+            #    """
+            #    dir, name = os.path.split(fd)
+            #    if dir:
+            #        p = filedir_lookup(p, dir)
+            #        if not p:
+            #            return None
+            #    norm_name = _my_normcase(name)
+            #    try:
+            #        node = p.entries[norm_name]
+            #    except KeyError:
+            #        return p.dir_on_disk(name)
+            #    if isinstance(node, Dir):
+            #        return node
+            #    if isinstance(node, Entry):
+            #        node.must_be_same(Dir)
+            #        return node
+            #    if isinstance(node, Dir) or isinstance(node, Entry):
+            #        return node
+            #    return None
+            #paths = [_f for _f in map(filedir_lookup, paths) if _f]
+
+            self.default_filedir = filedir
+            paths = [_f for _f in map(self.filedir_lookup, paths) if _f]
+
+        result = None
+        for dir in paths:
+            if verbose:
+                verbose("looking for '%s' in '%s' ...\n" % (filename, dir))
+            node, d = dir.srcdir_find_file(filename)
+            if node:
+                if verbose:
+                    verbose("... FOUND '%s' in '%s'\n" % (filename, d))
+                result = node
+                break
+
+        memo_dict[memo_key] = result
+
+        return result
+
+find_file = FileFinder().find_file
+
+
+def invalidate_node_memos(targets):
+    """
+    Invalidate the memoized values of all Nodes (files or directories)
+    that are associated with the given entries. Has been added to
+    clear the cache of nodes affected by a direct execution of an
+    action (e.g.  Delete/Copy/Chmod). Existing Node caches become
+    inconsistent if the action is run through Execute().  The argument
+    `targets` can be a single Node object or filename, or a sequence
+    of Nodes/filenames.
+    """
+    from traceback import extract_stack
+
+    # First check if the cache really needs to be flushed. Only
+    # actions run in the SConscript with Execute() seem to be
+    # affected. XXX The way to check if Execute() is in the stacktrace
+    # is a very dirty hack and should be replaced by a more sensible
+    # solution.
+    for f in extract_stack():
+        if f[2] == 'Execute' and f[0][-14:] == 'Environment.py':
+            break
+    else:
+        # Dont have to invalidate, so return
+        return
+
+    if not SCons.Util.is_List(targets):
+        targets = [targets]
+    
+    for entry in targets:
+        # If the target is a Node object, clear the cache. If it is a
+        # filename, look up potentially existing Node object first.
+        try:
+            entry.clear_memoized_values()
+        except AttributeError:
+            # Not a Node object, try to look up Node by filename.  XXX
+            # This creates Node objects even for those filenames which
+            # do not correspond to an existing Node object.
+            node = get_default_fs().Entry(entry)
+            if node:
+                node.clear_memoized_values()                        
+
+# Local Variables:
+# tab-width:4
+# indent-tabs-mode:nil
+# End:
+# vim: set expandtab tabstop=4 shiftwidth=4: