3 The Node package for the SCons software construction utility.
5 This is, in many ways, the heart of SCons.
7 A Node is where we encapsulate all of the dependency information about
8 any thing that SCons can build, or about any thing which SCons can use
9 to build some other thing. The canonical "thing," of course, is a file,
10 but a Node can also represent something remote (like a web page) or
11 something completely abstract (like an Alias).
13 Each specific type of "thing" is specifically represented by a subclass
14 of the Node base class: Node.FS.File for files, Node.Alias for aliases,
15 etc. Dependency information is kept here in the base class, and
16 information specific to files/aliases/etc. is in the subclass. The
17 goal, if we've done this correctly, is that any type of "thing" should
18 be able to depend on any other type of "thing."
25 # Permission is hereby granted, free of charge, to any person obtaining
26 # a copy of this software and associated documentation files (the
27 # "Software"), to deal in the Software without restriction, including
28 # without limitation the rights to use, copy, modify, merge, publish,
29 # distribute, sublicense, and/or sell copies of the Software, and to
30 # permit persons to whom the Software is furnished to do so, subject to
31 # the following conditions:
33 # The above copyright notice and this permission notice shall be included
34 # in all copies or substantial portions of the Software.
36 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
37 # KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
38 # WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
39 # NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
40 # LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
41 # OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
42 # WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
45 __revision__ = "__FILE__ __REVISION__ __DATE__ __DEVELOPER__"
52 from SCons.Debug import logInstanceCreation
58 # These are in "priority" order, so that the maximum value for any
59 # child/dependency of a node represents the state of that node if
60 # it has no builder of its own. The canonical example is a file
61 # system directory, which is only up to date if all of its children
68 stack = 6 # nodes that are in the current Taskmaster execution stack
70 # controls whether implicit depedencies are cached:
73 # controls whether implicit dep changes are ignored:
74 implicit_deps_unchanged = 0
76 # controls whether the cached implicit deps are ignored:
77 implicit_deps_changed = 0
79 # A variable that can be set to an interface-specific function be called
80 # to annotate a Node with information about its creation.
81 def do_nothing(node): pass
86 def __cmp__(self, other):
87 return cmp(self.__dict__, other.__dict__)
90 """The base Node class, for entities that we know how to
91 build, or use to build other Nodes.
98 if __debug__: logInstanceCreation(self, 'Node')
99 # Note that we no longer explicitly initialize a self.builder
100 # attribute to None here. That's because the self.builder
101 # attribute may be created on-the-fly later by a subclass (the
102 # canonical example being a builder to fetch a file from a
103 # source code system like CVS or Subversion).
105 # Each list of children that we maintain is accompanied by a
106 # dictionary used to look up quickly whether a node is already
107 # present in the list. Empirical tests showed that it was
108 # fastest to maintain them as side-by-side Node attributes in
109 # this way, instead of wrapping up each list+dictionary pair in
110 # a class. (Of course, we could always still do that in the
111 # future if we had a good reason to...).
112 self.sources = [] # source files used to build node
113 self.sources_dict = {}
114 self.depends = [] # explicit dependencies (from Depends)
115 self.depends_dict = {}
116 self.ignore = [] # dependencies to ignore
117 self.ignore_dict = {}
118 self.implicit = None # implicit (scanned) dependencies (None means not scanned yet)
119 self.waiting_parents = []
120 self.wkids = None # Kids yet to walk, when it's an array
121 self.target_scanner = None # explicit scanner from this node's Builder
122 self.source_scanner = None
123 self.backup_source_scanner = None
128 self.always_build = None
129 self.found_includes = {}
131 self.overrides = {} # construction variable overrides for building this node
132 self.attributes = self.Attrs() # Generic place to stick information about the Node.
133 self.side_effect = 0 # true iff this node is a side effect
134 self.side_effects = [] # the side effects of building this target
135 self.pre_actions = []
136 self.post_actions = []
137 self.linked = 0 # is this node linked to the build directory?
139 # Let the interface in which the build engine is embedded
140 # annotate this Node with its own info (like a description of
141 # what line in what file created the node, for example).
144 def get_suffix(self):
147 def generate_build_dict(self):
148 """Return an appropriate dictionary of values for building
152 def get_build_env(self):
153 """Fetch the appropriate Environment to build this node."""
154 executor = self.get_executor()
155 return executor.get_build_env()
157 def set_executor(self, executor):
158 """Set the action executor for this node."""
159 self.executor = executor
161 def get_executor(self, create=1):
162 """Fetch the action executor for this node. Create one if
163 there isn't already one, and requested to do so."""
165 executor = self.executor
166 except AttributeError:
169 import SCons.Executor
170 executor = SCons.Executor.Executor(self.builder.action,
172 [self.builder.overrides],
175 self.executor = executor
178 def retrieve_from_cache(self):
179 """Try to retrieve the node's content from a cache
181 This method is called from multiple threads in a parallel build,
182 so only do thread safe stuff here. Do thread unsafe stuff in
185 Returns true iff the node was successfully retrieved.
189 def build(self, **kw):
190 """Actually build the node.
192 This method is called from multiple threads in a parallel build,
193 so only do thread safe stuff here. Do thread unsafe stuff in
196 if not self.has_builder():
198 def errfunc(stat, node=self):
199 raise SCons.Errors.BuildError(node=node, errstr="Error %d" % stat)
200 executor = self.get_executor()
201 apply(executor, (self, errfunc), kw)
204 """Called just after this node is sucessfully built."""
206 # Clear the implicit dependency caches of any Nodes
207 # waiting for this Node to be built.
208 for parent in self.waiting_parents:
209 parent.implicit = None
213 new_binfo = self.binfo
214 except AttributeError:
215 # Node arrived here without build info; apparently it
216 # doesn't need it, so don't bother calculating or storing
220 # Reset this Node's cached state since it was just built and
221 # various state has changed.
222 save_state = self.get_state()
224 self.set_state(save_state)
226 # Had build info, so it should be stored in the signature
227 # cache. However, if the build info included a content
228 # signature then it should be recalculated before being
232 if hasattr(new_binfo, 'csig'):
233 new_binfo = self.gen_binfo() # sets self.binfo
235 self.binfo = new_binfo
236 self.store_info(new_binfo)
238 def add_to_waiting_parents(self, node):
239 self.waiting_parents.append(node)
241 def call_for_all_waiting_parents(self, func):
243 for parent in self.waiting_parents:
244 parent.call_for_all_waiting_parents(func)
246 def postprocess(self):
247 """Clean up anything we don't need to hang onto after we've
250 executor = self.get_executor(create=None)
251 except AttributeError:
257 """Completely clear a Node of all its cached state (so that it
258 can be re-evaluated by interfaces that do continuous integration
265 delattr(self, '_calculated_sig')
266 except AttributeError:
269 self.found_includes = {}
272 self.waiting_parents = []
275 """Called just after this node has been visited
276 without requiring a build.."""
279 def depends_on(self, nodes):
280 """Does this node depend on any of 'nodes'?"""
282 if node in self.children():
287 def builder_set(self, builder):
288 self.builder = builder
290 def has_builder(self):
291 """Return whether this Node has a builder or not.
293 In Boolean tests, this turns out to be a *lot* more efficient
294 than simply examining the builder attribute directly ("if
295 node.builder: ..."). When the builder attribute is examined
296 directly, it ends up calling __getattr__ for both the __len__
297 and __nonzero__ attributes on instances of our Builder Proxy
298 class(es), generating a bazillion extra calls and slowing
299 things down immensely.
303 except AttributeError:
304 # There was no explicit builder for this Node, so initialize
305 # the self.builder attribute to None now.
310 multiple_side_effect_has_builder = has_builder
312 def is_derived(self):
314 Returns true iff this node is derived (i.e. built).
316 This should return true only for nodes whose path should be in
317 the build directory when duplicate=0 and should contribute their build
318 signatures when they are used as source files to other derived files. For
319 example: source with source builders are not derived in this sense,
320 and hence should not return true.
322 return self.has_builder() or self.side_effect
324 def is_pseudo_derived(self):
326 Returns true iff this node is built, but should use a source path
327 when duplicate=0 and should contribute a content signature (i.e.
328 source signature) when used as a source for other derived files.
332 def alter_targets(self):
333 """Return a list of alternate targets for this Node.
337 def get_found_includes(self, env, scanner, target):
338 """Return the scanned include lines (implicit dependencies)
341 The default is no implicit dependencies. We expect this method
342 to be overridden by any subclass that can be scanned for
343 implicit dependencies.
347 def get_implicit_deps(self, env, scanner, target):
348 """Return a list of implicit dependencies for this node.
350 This method exists to handle recursive invocation of the scanner
351 on the implicit dependencies returned by the scanner, if the
352 scanner's recursive flag says that we should.
357 # Give the scanner a chance to select a more specific scanner
359 scanner = scanner.select(self)
362 recurse = scanner.recursive
363 except AttributeError:
372 d = filter(lambda x, seen=seen: not seen.has_key(x),
373 n.get_found_includes(env, scanner, target))
383 # cache used to make implicit_factory fast.
384 implicit_factory_cache = {}
386 def implicit_factory(self, path):
388 Turn a cache implicit dependency path into a node.
389 This is called so many times that doing caching
390 here is a significant performance boost.
393 return self.implicit_factory_cache[path]
395 n = self.builder.source_factory(path)
396 self.implicit_factory_cache[path] = n
399 def get_source_scanner(self, node):
400 """Fetch the source scanner for the specified node
402 NOTE: "self" is the target being built, "node" is
403 the source file for which we want to fetch the scanner.
405 if self.source_scanner:
406 return self.source_scanner
408 scanner = self.builder.source_scanner
411 except AttributeError:
413 return node.backup_source_scanner or None
416 """Scan this node's dependents for implicit dependencies."""
417 # Don't bother scanning non-derived files, because we don't
418 # care what their dependencies are.
419 # Don't scan again, if we already have scanned.
420 if not self.implicit is None:
423 self.implicit_dict = {}
424 self._children_reset()
425 if not self.has_builder():
428 build_env = self.get_build_env()
430 # Here's where we implement --implicit-cache.
431 if implicit_cache and not implicit_deps_changed:
432 implicit = self.get_stored_implicit()
433 if implicit is not None:
434 implicit = map(self.implicit_factory, implicit)
435 self._add_child(self.implicit, self.implicit_dict, implicit)
436 calc = build_env.get_calculator()
437 if implicit_deps_unchanged or self.current(calc, scan=0):
440 # one of this node's sources has changed, so
441 # we need to recalculate the implicit deps,
444 self.implicit_dict = {}
445 self._children_reset()
448 for child in self.children(scan=0):
449 scanner = self.get_source_scanner(child)
451 deps = child.get_implicit_deps(build_env, scanner, self)
452 self._add_child(self.implicit, self.implicit_dict, deps)
454 # scan this node itself for implicit dependencies
455 deps = self.get_implicit_deps(build_env, self.target_scanner, self)
456 self._add_child(self.implicit, self.implicit_dict, deps)
458 # XXX See note above re: --implicit-cache.
460 # self.store_implicit()
462 def scanner_key(self):
465 def env_set(self, env, safe=0):
466 if safe and self.env:
470 def calculator(self):
471 import SCons.Defaults
473 env = self.env or SCons.Defaults.DefaultEnvironment()
474 return env.get_calculator()
476 def calc_signature(self, calc=None):
478 Select and calculate the appropriate build signature for a node.
481 calc - the signature calculation module
482 returns - the signature
485 return self._calculated_sig
486 except AttributeError:
487 if self.is_derived():
488 import SCons.Defaults
490 env = self.env or SCons.Defaults.DefaultEnvironment()
491 if env.use_build_signature():
492 sig = self.calc_bsig(calc)
494 sig = self.calc_csig(calc)
495 elif not self.rexists():
498 sig = self.calc_csig(calc)
499 self._calculated_sig = sig
506 """Delete the bsig from this node."""
508 delattr(self, 'binfo')
509 except AttributeError:
512 def calc_bsig(self, calc=None):
514 return self.binfo.bsig
515 except AttributeError:
516 self.binfo = self.gen_binfo(calc)
517 return self.binfo.bsig
519 def gen_binfo(self, calc=None, scan=1):
521 Generate a node's build signature, the digested signatures
522 of its dependency files and build information.
524 node - the node whose sources will be collected
525 cache - alternate node to use for the signature cache
526 returns - the build signature
528 This no longer handles the recursive descent of the
529 node's children's signatures. We expect that they're
530 already built and updated by someone else, if that's
535 calc = self.calculator()
537 binfo = self.new_binfo()
542 sources = self.filter_ignore(self.sources)
543 depends = self.filter_ignore(self.depends)
544 if self.implicit is None:
547 implicit = self.filter_ignore(self.implicit)
549 def calc_signature(node, calc=calc):
550 return node.calc_signature(calc)
551 sourcesigs = map(calc_signature, sources)
552 dependsigs = map(calc_signature, depends)
553 implicitsigs = map(calc_signature, implicit)
555 sigs = sourcesigs + dependsigs + implicitsigs
557 if self.has_builder():
558 executor = self.get_executor()
559 binfo.bact = executor.strfunction()
560 binfo.bactsig = calc.module.signature(executor)
561 sigs.append(binfo.bactsig)
563 binfo.bsources = map(str, sources)
564 binfo.bdepends = map(str, depends)
565 binfo.bimplicit = map(str, implicit)
567 binfo.bsourcesigs = sourcesigs
568 binfo.bdependsigs = dependsigs
569 binfo.bimplicitsigs = implicitsigs
571 binfo.bsig = calc.module.collect(filter(None, sigs))
578 except AttributeError:
581 def calc_csig(self, calc=None):
584 except AttributeError:
585 binfo = self.binfo = self.new_binfo()
588 except AttributeError:
590 calc = self.calculator()
591 binfo.csig = calc.module.signature(self)
592 self.store_info(binfo)
595 def store_info(self, obj):
596 """Make the build signature permanent (that is, store it in the
597 .sconsign file or equivalent)."""
600 def get_stored_info(self):
603 def get_stored_implicit(self):
604 """Fetch the stored implicit dependencies"""
607 def set_precious(self, precious = 1):
608 """Set the Node's precious value."""
609 self.precious = precious
611 def set_always_build(self, always_build = 1):
612 """Set the Node's always_build value."""
613 self.always_build = always_build
616 """Does this node exists?"""
617 # All node exist by default:
621 """Does this node exist locally or in a repositiory?"""
622 # There are no repositories by default:
626 """Prepare for this Node to be created.
627 The default implemenation checks that all children either exist
631 return not node.is_derived() and \
632 not node.is_pseudo_derived() and \
633 not node.linked and \
635 missing_sources = filter(missing, self.children())
637 desc = "Source `%s' not found, needed by target `%s'." % (missing_sources[0], self)
638 raise SCons.Errors.StopError, desc
641 """Remove this Node: no-op by default."""
644 def add_dependency(self, depend):
645 """Adds dependencies."""
647 self._add_child(self.depends, self.depends_dict, depend)
650 if SCons.Util.is_List(e):
654 raise SCons.Errors.UserError("attempted to add a non-Node dependency to %s:\n\t%s is a %s, not a Node" % (str(self), s, type(e)))
656 def add_ignore(self, depend):
657 """Adds dependencies to ignore."""
659 self._add_child(self.ignore, self.ignore_dict, depend)
662 if SCons.Util.is_List(e):
666 raise SCons.Errors.UserError("attempted to ignore a non-Node dependency of %s:\n\t%s is a %s, not a Node" % (str(self), s, type(e)))
668 def add_source(self, source):
671 self._add_child(self.sources, self.sources_dict, source)
674 if SCons.Util.is_List(e):
678 raise SCons.Errors.UserError("attempted to add a non-Node as source of %s:\n\t%s is a %s, not a Node" % (str(self), s, type(e)))
680 def _add_child(self, collection, dict, child):
681 """Adds 'child' to 'collection', first checking 'dict' to see
682 if it's already present."""
683 if type(child) is not type([]):
686 if not isinstance(c, Node):
690 if not dict.has_key(c):
695 self._children_reset()
697 def add_wkid(self, wkid):
698 """Add a node to the list of kids waiting to be evaluated"""
699 if self.wkids != None:
700 self.wkids.append(wkid)
702 def _children_reset(self):
704 delattr(self, '_children')
705 except AttributeError:
708 def filter_ignore(self, nodelist):
711 for node in nodelist:
712 if node not in ignore:
716 def children(self, scan=1):
717 """Return a list of the node's direct children, minus those
718 that are ignored by this node."""
722 return self._children
723 except AttributeError:
724 c = self.all_children(scan=0)
725 self._children = self.filter_ignore(c)
726 return self._children
728 def all_children(self, scan=1):
729 """Return a list of all the node's direct children."""
730 # The return list may contain duplicate Nodes, especially in
731 # source trees where there are a lot of repeated #includes
732 # of a tangle of .h files. Profiling shows, however, that
733 # eliminating the duplicates with a brute-force approach that
734 # preserves the order (that is, something like:
741 # takes more cycles than just letting the underlying methods
742 # hand back cached values if a Node's information is requested
743 # multiple times. (Other methods of removing duplicates, like
744 # using dictionary keys, lose the order, and the only ordered
745 # dictionary patterns I found all ended up using "not in"
746 # internally anyway...)
749 if self.implicit is None:
750 return self.sources + self.depends
752 return self.sources + self.depends + self.implicit
754 def set_state(self, state):
760 def current(self, calc=None):
761 """Default check for whether the Node is current: unknown Node
762 subtypes are always out of date, so they will always get built."""
765 def children_are_up_to_date(self, calc=None):
766 """Alternate check for whether the Node is current: If all of
767 our children were up-to-date, then this Node was up-to-date, too.
769 The SCons.Node.Alias and SCons.Node.Python.Value subclasses
770 rebind their current() method to this method."""
771 # Allow the children to calculate their signatures.
772 self.binfo = self.gen_binfo(calc)
774 for kid in self.children(None):
776 if s and (not state or s > state):
778 return (state == 0 or state == SCons.Node.up_to_date)
780 def is_literal(self):
781 """Always pass the string representation of a Node to
782 the command interpreter literally."""
785 def add_pre_action(self, act):
786 """Adds an Action performed on this Node only before
788 self.pre_actions.append(act)
790 def add_post_action(self, act):
791 """Adds and Action performed on this Node only after
793 self.post_actions.append(act)
795 def render_include_tree(self):
797 Return a text representation, suitable for displaying to the
798 user, of the include tree for the sources of this node.
800 if self.is_derived() and self.env:
801 env = self.get_build_env()
802 for s in self.sources:
803 scanner = self.get_source_scanner(s)
804 def f(node, env=env, scanner=scanner, target=self):
805 return node.get_found_includes(env, scanner, target)
806 return SCons.Util.render_tree(s, f, 1)
810 def get_abspath(self):
812 Return an absolute path to the Node. This will return simply
813 str(Node) by default, but for Node types that have a concept of
814 relative path, this might return something different.
818 def for_signature(self):
820 Return a string representation of the Node that will always
821 be the same for this particular Node, no matter what. This
822 is by contrast to the __str__() method, which might, for
823 instance, return a relative path for a file Node. The purpose
824 of this method is to generate a value to be used in signature
825 calculation for the command line used to build a target, and
826 we use this method instead of str() to avoid unnecessary
827 rebuilds. This method does not need to return something that
828 would actually work in a command line; it can return any kind of
829 nonsense, so long as it does not change.
833 def get_string(self, for_signature):
834 """This is a convenience function designed primarily to be
835 used in command generators (i.e., CommandGeneratorActions or
836 Environment variables that are callable), which are called
837 with a for_signature argument that is nonzero if the command
838 generator is being called to generate a signature for the
839 command line, which determines if we should rebuild or not.
841 Such command generators should use this method in preference
842 to str(Node) when converting a Node to a string, passing
843 in the for_signature parameter, such that we will call
844 Node.for_signature() or str(Node) properly, depending on whether
845 we are calculating a signature or actually constructing a
848 return self.for_signature()
851 def get_subst_proxy(self):
853 This method is expected to return an object that will function
854 exactly like this Node, except that it implements any additional
855 special features that we would like to be in effect for
856 Environment variable substitution. The principle use is that
857 some Nodes would like to implement a __getattr__() method,
858 but putting that in the Node type itself has a tendency to kill
859 performance. We instead put it in a proxy and return it from
860 this method. It is legal for this method to return self
861 if no new functionality is needed for Environment substitution.
866 if not self.exists():
867 return "building `%s' because it doesn't exist\n" % self
869 old = self.get_stored_info()
873 def dictify(result, kids, sigs):
874 for k, s in zip(kids, sigs):
878 old_bkids = old.bsources + old.bdepends + old.bimplicit
879 except AttributeError:
880 return "Cannot explain why `%s' is being rebuilt: No previous build information found\n" % self
883 dictify(osig, old.bsources, old.bsourcesigs)
884 dictify(osig, old.bdepends, old.bdependsigs)
885 dictify(osig, old.bimplicit, old.bimplicitsigs)
887 new_bsources = map(str, self.binfo.bsources)
888 new_bdepends = map(str, self.binfo.bdepends)
889 new_bimplicit = map(str, self.binfo.bimplicit)
892 dictify(nsig, new_bsources, self.binfo.bsourcesigs)
893 dictify(nsig, new_bdepends, self.binfo.bdependsigs)
894 dictify(nsig, new_bimplicit, self.binfo.bimplicitsigs)
896 new_bkids = new_bsources + new_bdepends + new_bimplicit
897 lines = map(lambda x: "`%s' is no longer a dependency\n" % x,
898 filter(lambda x, nk=new_bkids: not x in nk, old_bkids))
901 if not k in old_bkids:
902 lines.append("`%s' is a new dependency\n" % k)
903 elif osig[k] != nsig[k]:
904 lines.append("`%s' changed\n" % k)
906 if len(lines) == 0 and old_bkids != new_bkids:
907 lines.append("the dependency order changed:\n" +
908 "%sold: %s\n" % (' '*15, old_bkids) +
909 "%snew: %s\n" % (' '*15, new_bkids))
912 newact, newactsig = self.binfo.bact, self.binfo.bactsig
913 def fmt_with_title(title, strlines):
914 lines = string.split(strlines, '\n')
915 sep = '\n' + ' '*(15 + len(title))
916 return ' '*15 + title + string.join(lines, sep) + '\n'
917 if old.bactsig != newactsig:
918 if old.bact == newact:
919 lines.append("the contents of the build action changed\n" +
920 fmt_with_title('action: ', newact))
922 lines.append("the build action changed:\n" +
923 fmt_with_title('old: ', old.bact) +
924 fmt_with_title('new: ', newact))
927 return "rebuilding `%s' for unknown reasons" % self
929 preamble = "rebuilding `%s' because" % self
931 return "%s %s" % (preamble, lines[0])
933 lines = ["%s:\n" % preamble] + lines
934 return string.join(lines, ' '*11)
936 def get_children(node, parent): return node.children()
937 def ignore_cycle(node, stack): pass
938 def do_nothing(node, parent): pass
941 """An iterator for walking a Node tree.
943 This is depth-first, children are visited before the parent.
944 The Walker object can be initialized with any node, and
945 returns the next node on the descent with each next() call.
946 'kids_func' is an optional function that will be called to
947 get the children of a node instead of calling 'children'.
948 'cycle_func' is an optional function that will be called
949 when a cycle is detected.
951 This class does not get caught in node cycles caused, for example,
952 by C header file include loops.
954 def __init__(self, node, kids_func=get_children,
955 cycle_func=ignore_cycle,
956 eval_func=do_nothing):
957 self.kids_func = kids_func
958 self.cycle_func = cycle_func
959 self.eval_func = eval_func
960 node.wkids = copy.copy(kids_func(node, None))
962 self.history = {} # used to efficiently detect and avoid cycles
963 self.history[node] = None
966 """Return the next node for this walk of the tree.
968 This function is intentionally iterative, not recursive,
969 to sidestep any issues of stack size limitations.
973 if self.stack[-1].wkids:
974 node = self.stack[-1].wkids.pop(0)
975 if not self.stack[-1].wkids:
976 self.stack[-1].wkids = None
977 if self.history.has_key(node):
978 self.cycle_func(node, self.stack)
980 node.wkids = copy.copy(self.kids_func(node, self.stack[-1]))
981 self.stack.append(node)
982 self.history[node] = None
984 node = self.stack.pop()
985 del self.history[node]
988 parent = self.stack[-1]
991 self.eval_func(node, parent)
996 return not self.stack
999 arg2nodes_lookups = []