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+#
+# Copyright (c) 2001 - 2014 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.
+
+__doc__ = """
+Generic Taskmaster module for the SCons build engine.
+
+This module contains the primary interface(s) between a wrapping user
+interface and the SCons build engine. There are two key classes here:
+
+ Taskmaster
+ This is the main engine for walking the dependency graph and
+ calling things to decide what does or doesn't need to be built.
+
+ Task
+ This is the base class for allowing a wrapping interface to
+ decide what does or doesn't actually need to be done. The
+ intention is for a wrapping interface to subclass this as
+ appropriate for different types of behavior it may need.
+
+ The canonical example is the SCons native Python interface,
+ which has Task subclasses that handle its specific behavior,
+ like printing "`foo' is up to date" when a top-level target
+ doesn't need to be built, and handling the -c option by removing
+ targets as its "build" action. There is also a separate subclass
+ for suppressing this output when the -q option is used.
+
+ The Taskmaster instantiates a Task object for each (set of)
+ target(s) that it decides need to be evaluated and/or built.
+"""
+
+__revision__ = "src/engine/SCons/Taskmaster.py 2014/09/27 12:51:43 garyo"
+
+from itertools import chain
+import operator
+import sys
+import traceback
+
+import SCons.Errors
+import SCons.Node
+import SCons.Warnings
+
+StateString = SCons.Node.StateString
+NODE_NO_STATE = SCons.Node.no_state
+NODE_PENDING = SCons.Node.pending
+NODE_EXECUTING = SCons.Node.executing
+NODE_UP_TO_DATE = SCons.Node.up_to_date
+NODE_EXECUTED = SCons.Node.executed
+NODE_FAILED = SCons.Node.failed
+
+print_prepare = 0 # set by option --debug=prepare
+
+# A subsystem for recording stats about how different Nodes are handled by
+# the main Taskmaster loop. There's no external control here (no need for
+# a --debug= option); enable it by changing the value of CollectStats.
+
+CollectStats = None
+
+class Stats(object):
+ """
+ A simple class for holding statistics about the disposition of a
+ Node by the Taskmaster. If we're collecting statistics, each Node
+ processed by the Taskmaster gets one of these attached, in which case
+ the Taskmaster records its decision each time it processes the Node.
+ (Ideally, that's just once per Node.)
+ """
+ def __init__(self):
+ """
+ Instantiates a Taskmaster.Stats object, initializing all
+ appropriate counters to zero.
+ """
+ self.considered = 0
+ self.already_handled = 0
+ self.problem = 0
+ self.child_failed = 0
+ self.not_built = 0
+ self.side_effects = 0
+ self.build = 0
+
+StatsNodes = []
+
+fmt = "%(considered)3d "\
+ "%(already_handled)3d " \
+ "%(problem)3d " \
+ "%(child_failed)3d " \
+ "%(not_built)3d " \
+ "%(side_effects)3d " \
+ "%(build)3d "
+
+def dump_stats():
+ for n in sorted(StatsNodes, key=lambda a: str(a)):
+ print (fmt % n.stats.__dict__) + str(n)
+
+
+
+class Task(object):
+ """
+ Default SCons build engine task.
+
+ This controls the interaction of the actual building of node
+ and the rest of the engine.
+
+ This is expected to handle all of the normally-customizable
+ aspects of controlling a build, so any given application
+ *should* be able to do what it wants by sub-classing this
+ class and overriding methods as appropriate. If an application
+ needs to customze something by sub-classing Taskmaster (or
+ some other build engine class), we should first try to migrate
+ that functionality into this class.
+
+ Note that it's generally a good idea for sub-classes to call
+ these methods explicitly to update state, etc., rather than
+ roll their own interaction with Taskmaster from scratch.
+ """
+ def __init__(self, tm, targets, top, node):
+ self.tm = tm
+ self.targets = targets
+ self.top = top
+ self.node = node
+ self.exc_clear()
+
+ def trace_message(self, method, node, description='node'):
+ fmt = '%-20s %s %s\n'
+ return fmt % (method + ':', description, self.tm.trace_node(node))
+
+ def display(self, message):
+ """
+ Hook to allow the calling interface to display a message.
+
+ This hook gets called as part of preparing a task for execution
+ (that is, a Node to be built). As part of figuring out what Node
+ should be built next, the actually target list may be altered,
+ along with a message describing the alteration. The calling
+ interface can subclass Task and provide a concrete implementation
+ of this method to see those messages.
+ """
+ pass
+
+ def prepare(self):
+ """
+ Called just before the task is executed.
+
+ This is mainly intended to give the target Nodes a chance to
+ unlink underlying files and make all necessary directories before
+ the Action is actually called to build the targets.
+ """
+ global print_prepare
+ T = self.tm.trace
+ if T: T.write(self.trace_message(u'Task.prepare()', self.node))
+
+ # Now that it's the appropriate time, give the TaskMaster a
+ # chance to raise any exceptions it encountered while preparing
+ # this task.
+ self.exception_raise()
+
+ if self.tm.message:
+ self.display(self.tm.message)
+ self.tm.message = None
+
+ # Let the targets take care of any necessary preparations.
+ # This includes verifying that all of the necessary sources
+ # and dependencies exist, removing the target file(s), etc.
+ #
+ # As of April 2008, the get_executor().prepare() method makes
+ # sure that all of the aggregate sources necessary to build this
+ # Task's target(s) exist in one up-front check. The individual
+ # target t.prepare() methods check that each target's explicit
+ # or implicit dependencies exists, and also initialize the
+ # .sconsign info.
+ executor = self.targets[0].get_executor()
+ if executor is None:
+ return
+ executor.prepare()
+ for t in executor.get_action_targets():
+ if print_prepare:
+ print "Preparing target %s..."%t
+ for s in t.side_effects:
+ print "...with side-effect %s..."%s
+ t.prepare()
+ for s in t.side_effects:
+ if print_prepare:
+ print "...Preparing side-effect %s..."%s
+ s.prepare()
+
+ def get_target(self):
+ """Fetch the target being built or updated by this task.
+ """
+ return self.node
+
+ def needs_execute(self):
+ # TODO(deprecate): "return True" is the old default behavior;
+ # change it to NotImplementedError (after running through the
+ # Deprecation Cycle) so the desired behavior is explicitly
+ # determined by which concrete subclass is used.
+ #raise NotImplementedError
+ msg = ('Taskmaster.Task is an abstract base class; instead of\n'
+ '\tusing it directly, '
+ 'derive from it and override the abstract methods.')
+ SCons.Warnings.warn(SCons.Warnings.TaskmasterNeedsExecuteWarning, msg)
+ return True
+
+ def execute(self):
+ """
+ Called to execute the task.
+
+ This method is called from multiple threads in a parallel build,
+ so only do thread safe stuff here. Do thread unsafe stuff in
+ prepare(), executed() or failed().
+ """
+ T = self.tm.trace
+ if T: T.write(self.trace_message(u'Task.execute()', self.node))
+
+ try:
+ cached_targets = []
+ for t in self.targets:
+ if not t.retrieve_from_cache():
+ break
+ cached_targets.append(t)
+ if len(cached_targets) < len(self.targets):
+ # Remove targets before building. It's possible that we
+ # partially retrieved targets from the cache, leaving
+ # them in read-only mode. That might cause the command
+ # to fail.
+ #
+ for t in cached_targets:
+ try:
+ t.fs.unlink(t.path)
+ except (IOError, OSError):
+ pass
+ self.targets[0].build()
+ else:
+ for t in cached_targets:
+ t.cached = 1
+ except SystemExit:
+ exc_value = sys.exc_info()[1]
+ raise SCons.Errors.ExplicitExit(self.targets[0], exc_value.code)
+ except SCons.Errors.UserError:
+ raise
+ except SCons.Errors.BuildError:
+ raise
+ except Exception, e:
+ buildError = SCons.Errors.convert_to_BuildError(e)
+ buildError.node = self.targets[0]
+ buildError.exc_info = sys.exc_info()
+ raise buildError
+
+ def executed_without_callbacks(self):
+ """
+ Called when the task has been successfully executed
+ and the Taskmaster instance doesn't want to call
+ the Node's callback methods.
+ """
+ T = self.tm.trace
+ if T: T.write(self.trace_message('Task.executed_without_callbacks()',
+ self.node))
+
+ for t in self.targets:
+ if t.get_state() == NODE_EXECUTING:
+ for side_effect in t.side_effects:
+ side_effect.set_state(NODE_NO_STATE)
+ t.set_state(NODE_EXECUTED)
+
+ def executed_with_callbacks(self):
+ """
+ Called when the task has been successfully executed and
+ the Taskmaster instance wants to call the Node's callback
+ methods.
+
+ This may have been a do-nothing operation (to preserve build
+ order), so we must check the node's state before deciding whether
+ it was "built", in which case we call the appropriate Node method.
+ In any event, we always call "visited()", which will handle any
+ post-visit actions that must take place regardless of whether
+ or not the target was an actual built target or a source Node.
+ """
+ global print_prepare
+ T = self.tm.trace
+ if T: T.write(self.trace_message('Task.executed_with_callbacks()',
+ self.node))
+
+ for t in self.targets:
+ if t.get_state() == NODE_EXECUTING:
+ for side_effect in t.side_effects:
+ side_effect.set_state(NODE_NO_STATE)
+ t.set_state(NODE_EXECUTED)
+ if not t.cached:
+ t.push_to_cache()
+ t.built()
+ t.visited()
+ if (not print_prepare and
+ (not hasattr(self, 'options') or not self.options.debug_includes)):
+ t.release_target_info()
+ else:
+ t.visited()
+
+ executed = executed_with_callbacks
+
+ def failed(self):
+ """
+ Default action when a task fails: stop the build.
+
+ Note: Although this function is normally invoked on nodes in
+ the executing state, it might also be invoked on up-to-date
+ nodes when using Configure().
+ """
+ self.fail_stop()
+
+ def fail_stop(self):
+ """
+ Explicit stop-the-build failure.
+
+ This sets failure status on the target nodes and all of
+ their dependent parent nodes.
+
+ Note: Although this function is normally invoked on nodes in
+ the executing state, it might also be invoked on up-to-date
+ nodes when using Configure().
+ """
+ T = self.tm.trace
+ if T: T.write(self.trace_message('Task.failed_stop()', self.node))
+
+ # Invoke will_not_build() to clean-up the pending children
+ # list.
+ self.tm.will_not_build(self.targets, lambda n: n.set_state(NODE_FAILED))
+
+ # Tell the taskmaster to not start any new tasks
+ self.tm.stop()
+
+ # We're stopping because of a build failure, but give the
+ # calling Task class a chance to postprocess() the top-level
+ # target under which the build failure occurred.
+ self.targets = [self.tm.current_top]
+ self.top = 1
+
+ def fail_continue(self):
+ """
+ Explicit continue-the-build failure.
+
+ This sets failure status on the target nodes and all of
+ their dependent parent nodes.
+
+ Note: Although this function is normally invoked on nodes in
+ the executing state, it might also be invoked on up-to-date
+ nodes when using Configure().
+ """
+ T = self.tm.trace
+ if T: T.write(self.trace_message('Task.failed_continue()', self.node))
+
+ self.tm.will_not_build(self.targets, lambda n: n.set_state(NODE_FAILED))
+
+ def make_ready_all(self):
+ """
+ Marks all targets in a task ready for execution.
+
+ This is used when the interface needs every target Node to be
+ visited--the canonical example being the "scons -c" option.
+ """
+ T = self.tm.trace
+ if T: T.write(self.trace_message('Task.make_ready_all()', self.node))
+
+ self.out_of_date = self.targets[:]
+ for t in self.targets:
+ t.disambiguate().set_state(NODE_EXECUTING)
+ for s in t.side_effects:
+ # add disambiguate here to mirror the call on targets above
+ s.disambiguate().set_state(NODE_EXECUTING)
+
+ def make_ready_current(self):
+ """
+ Marks all targets in a task ready for execution if any target
+ is not current.
+
+ This is the default behavior for building only what's necessary.
+ """
+ global print_prepare
+ T = self.tm.trace
+ if T: T.write(self.trace_message(u'Task.make_ready_current()',
+ self.node))
+
+ self.out_of_date = []
+ needs_executing = False
+ for t in self.targets:
+ try:
+ t.disambiguate().make_ready()
+ is_up_to_date = not t.has_builder() or \
+ (not t.always_build and t.is_up_to_date())
+ except EnvironmentError, e:
+ raise SCons.Errors.BuildError(node=t, errstr=e.strerror, filename=e.filename)
+
+ if not is_up_to_date:
+ self.out_of_date.append(t)
+ needs_executing = True
+
+ if needs_executing:
+ for t in self.targets:
+ t.set_state(NODE_EXECUTING)
+ for s in t.side_effects:
+ # add disambiguate here to mirror the call on targets in first loop above
+ s.disambiguate().set_state(NODE_EXECUTING)
+ else:
+ for t in self.targets:
+ # We must invoke visited() to ensure that the node
+ # information has been computed before allowing the
+ # parent nodes to execute. (That could occur in a
+ # parallel build...)
+ t.visited()
+ t.set_state(NODE_UP_TO_DATE)
+ if (not print_prepare and
+ (not hasattr(self, 'options') or not self.options.debug_includes)):
+ t.release_target_info()
+
+ make_ready = make_ready_current
+
+ def postprocess(self):
+ """
+ Post-processes a task after it's been executed.
+
+ This examines all the targets just built (or not, we don't care
+ if the build was successful, or even if there was no build
+ because everything was up-to-date) to see if they have any
+ waiting parent Nodes, or Nodes waiting on a common side effect,
+ that can be put back on the candidates list.
+ """
+ T = self.tm.trace
+ if T: T.write(self.trace_message(u'Task.postprocess()', self.node))
+
+ # We may have built multiple targets, some of which may have
+ # common parents waiting for this build. Count up how many
+ # targets each parent was waiting for so we can subtract the
+ # values later, and so we *don't* put waiting side-effect Nodes
+ # back on the candidates list if the Node is also a waiting
+ # parent.
+
+ targets = set(self.targets)
+
+ pending_children = self.tm.pending_children
+ parents = {}
+ for t in targets:
+ # A node can only be in the pending_children set if it has
+ # some waiting_parents.
+ if t.waiting_parents:
+ if T: T.write(self.trace_message(u'Task.postprocess()',
+ t,
+ 'removing'))
+ pending_children.discard(t)
+ for p in t.waiting_parents:
+ parents[p] = parents.get(p, 0) + 1
+
+ for t in targets:
+ if t.side_effects is not None:
+ for s in t.side_effects:
+ if s.get_state() == NODE_EXECUTING:
+ s.set_state(NODE_NO_STATE)
+ for p in s.waiting_parents:
+ parents[p] = parents.get(p, 0) + 1
+ for p in s.waiting_s_e:
+ if p.ref_count == 0:
+ self.tm.candidates.append(p)
+
+ for p, subtract in parents.items():
+ p.ref_count = p.ref_count - subtract
+ if T: T.write(self.trace_message(u'Task.postprocess()',
+ p,
+ 'adjusted parent ref count'))
+ if p.ref_count == 0:
+ self.tm.candidates.append(p)
+
+ for t in targets:
+ t.postprocess()
+
+ # Exception handling subsystem.
+ #
+ # Exceptions that occur while walking the DAG or examining Nodes
+ # must be raised, but must be raised at an appropriate time and in
+ # a controlled manner so we can, if necessary, recover gracefully,
+ # possibly write out signature information for Nodes we've updated,
+ # etc. This is done by having the Taskmaster tell us about the
+ # exception, and letting
+
+ def exc_info(self):
+ """
+ Returns info about a recorded exception.
+ """
+ return self.exception
+
+ def exc_clear(self):
+ """
+ Clears any recorded exception.
+
+ This also changes the "exception_raise" attribute to point
+ to the appropriate do-nothing method.
+ """
+ self.exception = (None, None, None)
+ self.exception_raise = self._no_exception_to_raise
+
+ def exception_set(self, exception=None):
+ """
+ Records an exception to be raised at the appropriate time.
+
+ This also changes the "exception_raise" attribute to point
+ to the method that will, in fact
+ """
+ if not exception:
+ exception = sys.exc_info()
+ self.exception = exception
+ self.exception_raise = self._exception_raise
+
+ def _no_exception_to_raise(self):
+ pass
+
+ def _exception_raise(self):
+ """
+ Raises a pending exception that was recorded while getting a
+ Task ready for execution.
+ """
+ exc = self.exc_info()[:]
+ try:
+ exc_type, exc_value, exc_traceback = exc
+ except ValueError:
+ exc_type, exc_value = exc
+ exc_traceback = None
+ raise exc_type, exc_value, exc_traceback
+
+class AlwaysTask(Task):
+ def needs_execute(self):
+ """
+ Always returns True (indicating this Task should always
+ be executed).
+
+ Subclasses that need this behavior (as opposed to the default
+ of only executing Nodes that are out of date w.r.t. their
+ dependencies) can use this as follows:
+
+ class MyTaskSubclass(SCons.Taskmaster.Task):
+ needs_execute = SCons.Taskmaster.Task.execute_always
+ """
+ return True
+
+class OutOfDateTask(Task):
+ def needs_execute(self):
+ """
+ Returns True (indicating this Task should be executed) if this
+ Task's target state indicates it needs executing, which has
+ already been determined by an earlier up-to-date check.
+ """
+ return self.targets[0].get_state() == SCons.Node.executing
+
+
+def find_cycle(stack, visited):
+ if stack[-1] in visited:
+ return None
+ visited.add(stack[-1])
+ for n in stack[-1].waiting_parents:
+ stack.append(n)
+ if stack[0] == stack[-1]:
+ return stack
+ if find_cycle(stack, visited):
+ return stack
+ stack.pop()
+ return None
+
+
+class Taskmaster(object):
+ """
+ The Taskmaster for walking the dependency DAG.
+ """
+
+ def __init__(self, targets=[], tasker=None, order=None, trace=None):
+ self.original_top = targets
+ self.top_targets_left = targets[:]
+ self.top_targets_left.reverse()
+ self.candidates = []
+ if tasker is None:
+ tasker = OutOfDateTask
+ self.tasker = tasker
+ if not order:
+ order = lambda l: l
+ self.order = order
+ self.message = None
+ self.trace = trace
+ self.next_candidate = self.find_next_candidate
+ self.pending_children = set()
+
+ def find_next_candidate(self):
+ """
+ Returns the next candidate Node for (potential) evaluation.
+
+ The candidate list (really a stack) initially consists of all of
+ the top-level (command line) targets provided when the Taskmaster
+ was initialized. While we walk the DAG, visiting Nodes, all the
+ children that haven't finished processing get pushed on to the
+ candidate list. Each child can then be popped and examined in
+ turn for whether *their* children are all up-to-date, in which
+ case a Task will be created for their actual evaluation and
+ potential building.
+
+ Here is where we also allow candidate Nodes to alter the list of
+ Nodes that should be examined. This is used, for example, when
+ invoking SCons in a source directory. A source directory Node can
+ return its corresponding build directory Node, essentially saying,
+ "Hey, you really need to build this thing over here instead."
+ """
+ try:
+ return self.candidates.pop()
+ except IndexError:
+ pass
+ try:
+ node = self.top_targets_left.pop()
+ except IndexError:
+ return None
+ self.current_top = node
+ alt, message = node.alter_targets()
+ if alt:
+ self.message = message
+ self.candidates.append(node)
+ self.candidates.extend(self.order(alt))
+ node = self.candidates.pop()
+ return node
+
+ def no_next_candidate(self):
+ """
+ Stops Taskmaster processing by not returning a next candidate.
+
+ Note that we have to clean-up the Taskmaster candidate list
+ because the cycle detection depends on the fact all nodes have
+ been processed somehow.
+ """
+ while self.candidates:
+ candidates = self.candidates
+ self.candidates = []
+ self.will_not_build(candidates)
+ return None
+
+ def _validate_pending_children(self):
+ """
+ Validate the content of the pending_children set. Assert if an
+ internal error is found.
+
+ This function is used strictly for debugging the taskmaster by
+ checking that no invariants are violated. It is not used in
+ normal operation.
+
+ The pending_children set is used to detect cycles in the
+ dependency graph. We call a "pending child" a child that is
+ found in the "pending" state when checking the dependencies of
+ its parent node.
+
+ A pending child can occur when the Taskmaster completes a loop
+ through a cycle. For example, lets imagine a graph made of
+ three node (A, B and C) making a cycle. The evaluation starts
+ at node A. The taskmaster first consider whether node A's
+ child B is up-to-date. Then, recursively, node B needs to
+ check whether node C is up-to-date. This leaves us with a
+ dependency graph looking like:
+
+ Next candidate \
+ \
+ Node A (Pending) --> Node B(Pending) --> Node C (NoState)
+ ^ |
+ | |
+ +-------------------------------------+
+
+ Now, when the Taskmaster examines the Node C's child Node A,
+ it finds that Node A is in the "pending" state. Therefore,
+ Node A is a pending child of node C.
+
+ Pending children indicate that the Taskmaster has potentially
+ loop back through a cycle. We say potentially because it could
+ also occur when a DAG is evaluated in parallel. For example,
+ consider the following graph:
+
+
+ Node A (Pending) --> Node B(Pending) --> Node C (Pending) --> ...
+ | ^
+ | |
+ +----------> Node D (NoState) --------+
+ /
+ Next candidate /
+
+ The Taskmaster first evaluates the nodes A, B, and C and
+ starts building some children of node C. Assuming, that the
+ maximum parallel level has not been reached, the Taskmaster
+ will examine Node D. It will find that Node C is a pending
+ child of Node D.
+
+ In summary, evaluating a graph with a cycle will always
+ involve a pending child at one point. A pending child might
+ indicate either a cycle or a diamond-shaped DAG. Only a
+ fraction of the nodes ends-up being a "pending child" of
+ another node. This keeps the pending_children set small in
+ practice.
+
+ We can differentiate between the two cases if we wait until
+ the end of the build. At this point, all the pending children
+ nodes due to a diamond-shaped DAG will have been properly
+ built (or will have failed to build). But, the pending
+ children involved in a cycle will still be in the pending
+ state.
+
+ The taskmaster removes nodes from the pending_children set as
+ soon as a pending_children node moves out of the pending
+ state. This also helps to keep the pending_children set small.
+ """
+
+ for n in self.pending_children:
+ assert n.state in (NODE_PENDING, NODE_EXECUTING), \
+ (str(n), StateString[n.state])
+ assert len(n.waiting_parents) != 0, (str(n), len(n.waiting_parents))
+ for p in n.waiting_parents:
+ assert p.ref_count > 0, (str(n), str(p), p.ref_count)
+
+
+ def trace_message(self, message):
+ return 'Taskmaster: %s\n' % message
+
+ def trace_node(self, node):
+ return '<%-10s %-3s %s>' % (StateString[node.get_state()],
+ node.ref_count,
+ repr(str(node)))
+
+ def _find_next_ready_node(self):
+ """
+ Finds the next node that is ready to be built.
+
+ This is *the* main guts of the DAG walk. We loop through the
+ list of candidates, looking for something that has no un-built
+ children (i.e., that is a leaf Node or has dependencies that are
+ all leaf Nodes or up-to-date). Candidate Nodes are re-scanned
+ (both the target Node itself and its sources, which are always
+ scanned in the context of a given target) to discover implicit
+ dependencies. A Node that must wait for some children to be
+ built will be put back on the candidates list after the children
+ have finished building. A Node that has been put back on the
+ candidates list in this way may have itself (or its sources)
+ re-scanned, in order to handle generated header files (e.g.) and
+ the implicit dependencies therein.
+
+ Note that this method does not do any signature calculation or
+ up-to-date check itself. All of that is handled by the Task
+ class. This is purely concerned with the dependency graph walk.
+ """
+
+ self.ready_exc = None
+
+ T = self.trace
+ if T: T.write(u'\n' + self.trace_message('Looking for a node to evaluate'))
+
+ while True:
+ node = self.next_candidate()
+ if node is None:
+ if T: T.write(self.trace_message('No candidate anymore.') + u'\n')
+ return None
+
+ node = node.disambiguate()
+ state = node.get_state()
+
+ # For debugging only:
+ #
+ # try:
+ # self._validate_pending_children()
+ # except:
+ # self.ready_exc = sys.exc_info()
+ # return node
+
+ if CollectStats:
+ if not hasattr(node, 'stats'):
+ node.stats = Stats()
+ StatsNodes.append(node)
+ S = node.stats
+ S.considered = S.considered + 1
+ else:
+ S = None
+
+ if T: T.write(self.trace_message(u' Considering node %s and its children:' % self.trace_node(node)))
+
+ if state == NODE_NO_STATE:
+ # Mark this node as being on the execution stack:
+ node.set_state(NODE_PENDING)
+ elif state > NODE_PENDING:
+ # Skip this node if it has already been evaluated:
+ if S: S.already_handled = S.already_handled + 1
+ if T: T.write(self.trace_message(u' already handled (executed)'))
+ continue
+
+ executor = node.get_executor()
+
+ try:
+ children = executor.get_all_children()
+ except SystemExit:
+ exc_value = sys.exc_info()[1]
+ e = SCons.Errors.ExplicitExit(node, exc_value.code)
+ self.ready_exc = (SCons.Errors.ExplicitExit, e)
+ if T: T.write(self.trace_message(' SystemExit'))
+ return node
+ except Exception, e:
+ # We had a problem just trying to figure out the
+ # children (like a child couldn't be linked in to a
+ # VariantDir, or a Scanner threw something). Arrange to
+ # raise the exception when the Task is "executed."
+ self.ready_exc = sys.exc_info()
+ if S: S.problem = S.problem + 1
+ if T: T.write(self.trace_message(' exception %s while scanning children.\n' % e))
+ return node
+
+ children_not_visited = []
+ children_pending = set()
+ children_not_ready = []
+ children_failed = False
+
+ for child in chain(executor.get_all_prerequisites(), children):
+ childstate = child.get_state()
+
+ if T: T.write(self.trace_message(u' ' + self.trace_node(child)))
+
+ if childstate == NODE_NO_STATE:
+ children_not_visited.append(child)
+ elif childstate == NODE_PENDING:
+ children_pending.add(child)
+ elif childstate == NODE_FAILED:
+ children_failed = True
+
+ if childstate <= NODE_EXECUTING:
+ children_not_ready.append(child)
+
+
+ # These nodes have not even been visited yet. Add
+ # them to the list so that on some next pass we can
+ # take a stab at evaluating them (or their children).
+ children_not_visited.reverse()
+ self.candidates.extend(self.order(children_not_visited))
+ #if T and children_not_visited:
+ # T.write(self.trace_message(' adding to candidates: %s' % map(str, children_not_visited)))
+ # T.write(self.trace_message(' candidates now: %s\n' % map(str, self.candidates)))
+
+ # Skip this node if any of its children have failed.
+ #
+ # This catches the case where we're descending a top-level
+ # target and one of our children failed while trying to be
+ # built by a *previous* descent of an earlier top-level
+ # target.
+ #
+ # It can also occur if a node is reused in multiple
+ # targets. One first descends though the one of the
+ # target, the next time occurs through the other target.
+ #
+ # Note that we can only have failed_children if the
+ # --keep-going flag was used, because without it the build
+ # will stop before diving in the other branch.
+ #
+ # Note that even if one of the children fails, we still
+ # added the other children to the list of candidate nodes
+ # to keep on building (--keep-going).
+ if children_failed:
+ for n in executor.get_action_targets():
+ n.set_state(NODE_FAILED)
+
+ if S: S.child_failed = S.child_failed + 1
+ if T: T.write(self.trace_message('****** %s\n' % self.trace_node(node)))
+ continue
+
+ if children_not_ready:
+ for child in children_not_ready:
+ # We're waiting on one or more derived targets
+ # that have not yet finished building.
+ if S: S.not_built = S.not_built + 1
+
+ # Add this node to the waiting parents lists of
+ # anything we're waiting on, with a reference
+ # count so we can be put back on the list for
+ # re-evaluation when they've all finished.
+ node.ref_count = node.ref_count + child.add_to_waiting_parents(node)
+ if T: T.write(self.trace_message(u' adjusted ref count: %s, child %s' %
+ (self.trace_node(node), repr(str(child)))))
+
+ if T:
+ for pc in children_pending:
+ T.write(self.trace_message(' adding %s to the pending children set\n' %
+ self.trace_node(pc)))
+ self.pending_children = self.pending_children | children_pending
+
+ continue
+
+ # Skip this node if it has side-effects that are
+ # currently being built:
+ wait_side_effects = False
+ for se in executor.get_action_side_effects():
+ if se.get_state() == NODE_EXECUTING:
+ se.add_to_waiting_s_e(node)
+ wait_side_effects = True
+
+ if wait_side_effects:
+ if S: S.side_effects = S.side_effects + 1
+ continue
+
+ # The default when we've gotten through all of the checks above:
+ # this node is ready to be built.
+ if S: S.build = S.build + 1
+ if T: T.write(self.trace_message(u'Evaluating %s\n' %
+ self.trace_node(node)))
+
+ # For debugging only:
+ #
+ # try:
+ # self._validate_pending_children()
+ # except:
+ # self.ready_exc = sys.exc_info()
+ # return node
+
+ return node
+
+ return None
+
+ def next_task(self):
+ """
+ Returns the next task to be executed.
+
+ This simply asks for the next Node to be evaluated, and then wraps
+ it in the specific Task subclass with which we were initialized.
+ """
+ node = self._find_next_ready_node()
+
+ if node is None:
+ return None
+
+ executor = node.get_executor()
+ if executor is None:
+ return None
+
+ tlist = executor.get_all_targets()
+
+ task = self.tasker(self, tlist, node in self.original_top, node)
+ try:
+ task.make_ready()
+ except:
+ # We had a problem just trying to get this task ready (like
+ # a child couldn't be linked in to a VariantDir when deciding
+ # whether this node is current). Arrange to raise the
+ # exception when the Task is "executed."
+ self.ready_exc = sys.exc_info()
+
+ if self.ready_exc:
+ task.exception_set(self.ready_exc)
+
+ self.ready_exc = None
+
+ return task
+
+ def will_not_build(self, nodes, node_func=lambda n: None):
+ """
+ Perform clean-up about nodes that will never be built. Invokes
+ a user defined function on all of these nodes (including all
+ of their parents).
+ """
+
+ T = self.trace
+
+ pending_children = self.pending_children
+
+ to_visit = set(nodes)
+ pending_children = pending_children - to_visit
+
+ if T:
+ for n in nodes:
+ T.write(self.trace_message(' removing node %s from the pending children set\n' %
+ self.trace_node(n)))
+ try:
+ while len(to_visit):
+ node = to_visit.pop()
+ node_func(node)
+
+ # Prune recursion by flushing the waiting children
+ # list immediately.
+ parents = node.waiting_parents
+ node.waiting_parents = set()
+
+ to_visit = to_visit | parents
+ pending_children = pending_children - parents
+
+ for p in parents:
+ p.ref_count = p.ref_count - 1
+ if T: T.write(self.trace_message(' removing parent %s from the pending children set\n' %
+ self.trace_node(p)))
+ except KeyError:
+ # The container to_visit has been emptied.
+ pass
+
+ # We have the stick back the pending_children list into the
+ # taskmaster because the python 1.5.2 compatibility does not
+ # allow us to use in-place updates
+ self.pending_children = pending_children
+
+ def stop(self):
+ """
+ Stops the current build completely.
+ """
+ self.next_candidate = self.no_next_candidate
+
+ def cleanup(self):
+ """
+ Check for dependency cycles.
+ """
+ if not self.pending_children:
+ return
+
+ nclist = [(n, find_cycle([n], set())) for n in self.pending_children]
+
+ genuine_cycles = [
+ node for node,cycle in nclist
+ if cycle or node.get_state() != NODE_EXECUTED
+ ]
+ if not genuine_cycles:
+ # All of the "cycles" found were single nodes in EXECUTED state,
+ # which is to say, they really weren't cycles. Just return.
+ return
+
+ desc = 'Found dependency cycle(s):\n'
+ for node, cycle in nclist:
+ if cycle:
+ desc = desc + " " + " -> ".join(map(str, cycle)) + "\n"
+ else:
+ desc = desc + \
+ " Internal Error: no cycle found for node %s (%s) in state %s\n" % \
+ (node, repr(node), StateString[node.get_state()])
+
+ raise SCons.Errors.UserError(desc)
+
+# Local Variables:
+# tab-width:4
+# indent-tabs-mode:nil
+# End:
+# vim: set expandtab tabstop=4 shiftwidth=4: