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|
#
# __COPYRIGHT__
#
# 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__ = "__FILE__ __REVISION__ __DATE__ __DEVELOPER__"
import SCons.compat
import operator
import string
import sys
import traceback
import SCons.Node
import SCons.Errors
StateString = SCons.Node.StateString
# 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:
"""
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():
StatsNodes.sort(lambda a, b: cmp(str(a), str(b)))
for n in StatsNodes:
print (fmt % n.stats.__dict__) + str(n)
class Task:
"""
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 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.
"""
# 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
for t in self.targets:
t.prepare()
for s in t.side_effects:
s.prepare()
def get_target(self):
"""Fetch the target being built or updated by this task.
"""
return self.node
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().
"""
try:
everything_was_cached = 1
for t in self.targets:
if not t.retrieve_from_cache():
everything_was_cached = 0
break
if not everything_was_cached:
self.targets[0].build()
except KeyboardInterrupt:
raise
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:
raise SCons.Errors.TaskmasterException(self.targets[0],
sys.exc_info())
def executed(self):
"""
Called when the task has been successfully executed.
This may have been a do-nothing operation (to preserve build
order), so we have to check the node's state before deciding
whether it was "built" or just "visited."
"""
for t in self.targets:
if t.get_state() == SCons.Node.executing:
t.set_state(SCons.Node.executed)
t.built()
else:
t.visited()
def failed(self):
"""
Default action when a task fails: stop the build.
"""
self.fail_stop()
def fail_stop(self):
"""
Explicit stop-the-build failure.
"""
for t in self.targets:
t.set_state(SCons.Node.failed)
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.
"""
for t in self.targets:
# Set failure state on all of the parents that were dependent
# on this failed build.
def set_state(node): node.set_state(SCons.Node.failed)
t.call_for_all_waiting_parents(set_state)
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.
"""
self.out_of_date = self.targets[:]
for t in self.targets:
t.disambiguate().set_state(SCons.Node.executing)
for s in t.side_effects:
s.set_state(SCons.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.
"""
self.out_of_date = []
for t in self.targets:
t.disambiguate()
try:
is_up_to_date = not t.always_build and t.current()
except EnvironmentError, e:
raise SCons.Errors.BuildError(node=t, errstr=e.strerror, filename=e.filename)
if is_up_to_date:
t.set_state(SCons.Node.up_to_date)
else:
self.out_of_date.append(t)
t.set_state(SCons.Node.executing)
for s in t.side_effects:
s.set_state(SCons.Node.executing)
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.
"""
# 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.
parents = {}
for t in self.targets:
for p in t.waiting_parents.keys():
parents[p] = parents.get(p, 0) + 1
for t in self.targets:
for s in t.side_effects:
if s.get_state() == SCons.Node.executing:
s.set_state(SCons.Node.no_state)
for p in s.waiting_parents.keys():
if not parents.has_key(p):
parents[p] = 1
for p in s.waiting_s_e.keys():
if p.ref_count == 0:
self.tm.candidates.append(p)
for p, subtract in parents.items():
p.ref_count = p.ref_count - subtract
if p.ref_count == 0:
self.tm.candidates.append(p)
for t in self.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
def find_cycle(stack):
if stack[0] == stack[-1]:
return stack
for n in stack[-1].waiting_parents.keys():
stack.append(n)
if find_cycle(stack):
return stack
stack.pop()
return None
class Taskmaster:
"""
The Taskmaster for walking the dependency DAG.
"""
def __init__(self, targets=[], tasker=Task, order=None, trace=None):
self.top_targets = targets[:]
self.top_targets.reverse()
self.candidates = []
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
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.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.
"""
return None
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
while 1:
node = self.next_candidate()
if node is None:
return None
node = node.disambiguate()
state = node.get_state()
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('Taskmaster: %s:' % repr(str(node)))
# Skip this node if it has already been evaluated:
if state > SCons.Node.pending:
if S: S.already_handled = S.already_handled + 1
if T: T.write(' already handled (%s)\n' % StateString[state])
continue
# Mark this node as being on the execution stack:
node.set_state(SCons.Node.pending)
try:
children = node.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(' SystemExit\n')
return node
except KeyboardInterrupt:
if T: T.write(' KeyboardInterrupt\n')
raise
except:
# We had a problem just trying to figure out the
# children (like a child couldn't be linked in to a
# BuildDir, 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(' exception\n')
return node
if T and children:
c = map(str, children)
c.sort()
T.write(' children:\n %s\n ' % c)
childinfo = map(lambda N: (N.get_state(),
N.is_derived() or N.is_pseudo_derived(),
N), children)
# 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.
failed_children = filter(lambda I: I[0] == SCons.Node.failed,
childinfo)
if failed_children:
node.set_state(SCons.Node.failed)
if S: S.child_failed = S.child_failed + 1
if T:
c = map(str, failed_children)
c.sort()
T.write(' children failed:\n %s\n' % c)
continue
# Detect dependency cycles:
pending_nodes = filter(lambda I: I[0] == SCons.Node.pending, childinfo)
if pending_nodes:
for p in pending_nodes:
cycle = find_cycle([p[2], node])
if cycle:
desc = "Dependency cycle: " + string.join(map(str, cycle), " -> ")
if T: T.write(' dependency cycle\n')
raise SCons.Errors.UserError, desc
# Select all of the dependencies that are derived targets
# (that is, children who have builders or are side effects).
derived_children = filter(lambda I: I[1], childinfo)
not_started = filter(lambda I: not I[0], derived_children)
if not_started:
not_started = map(lambda I: I[2], not_started)
# We're waiting on one more derived targets that have
# not yet started building. Add this node to the
# waiting_parents lists of those derived files so that
# when they've finished building, our implicit dependency
# list will get cleared and we'll re-scan the newly-built
# file(s) for updated implicit dependencies.
added = map(lambda n, P=node: n.add_to_waiting_parents(P), not_started)
node.ref_count = node.ref_count + reduce(operator.add, added, 0)
# Now we add these derived targets to the candidates
# list so they can be examined and built. We have to
# add ourselves back to the list first, though, so we get
# a chance to re-scan and build after the dependencies.
#
# We reverse the order in which the children are added
# to the candidates stack so the order in which they're
# popped matches the order in which they show up in our
# children's list. This is more logical / efficient for
# builders with multiple targets, since the "primary"
# target will be examined first.
self.candidates.append(node)
not_started.reverse()
self.candidates.extend(self.order(not_started))
if S: S.not_started = S.not_started + 1
if T:
c = map(str, not_started)
c.sort()
T.write(' waiting on unstarted children:\n %s\n' % c)
continue
not_built = filter(lambda I: I[0] <= SCons.Node.executing, derived_children)
if not_built:
not_built = map(lambda I: I[2], not_built)
# We're waiting on one or more derived targets that have
# started building but not yet finished. Add this node
# to the waiting parents lists of those derived files
# so that when they've finished building, our implicit
# dependency list will get cleared and we'll re-scan the
# newly-built file(s) for updated implicit dependencies.
added = map(lambda n, P=node: n.add_to_waiting_parents(P), not_built)
node.ref_count = node.ref_count + reduce(operator.add, added, 0)
if S: S.not_built = S.not_built + 1
if T:
c = map(str, not_built)
c.sort()
T.write(' waiting on unfinished children:\n %s\n' % c)
continue
# Skip this node if it has side-effects that are currently being
# built themselves or waiting for something else being built.
side_effects = filter(lambda N:
N.get_state() == SCons.Node.executing,
node.side_effects)
if side_effects:
map(lambda n, P=node: n.add_to_waiting_s_e(P), side_effects)
if S: S.side_effects = S.side_effects + 1
if T:
c = map(str, side_effects)
c.sort()
T.write(' waiting on side effects:\n %s\n' % c)
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(' evaluating %s\n' % 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
tlist = node.get_executor().targets
task = self.tasker(self, tlist, node is self.current_top, node)
try:
task.make_ready()
except KeyboardInterrupt:
raise
except:
# We had a problem just trying to get this task ready (like
# a child couldn't be linked in to a BuildDir 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 stop(self):
"""
Stops the current build completely.
"""
self.next_candidate = self.no_next_candidate
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