Package SCons :: Module Taskmaster :: Class Taskmaster
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Class Taskmaster

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The Taskmaster for walking the dependency DAG.



Instance Methods [hide private]
 
__init__(self, targets=[], tasker=<class SCons.Taskmaster.Task at 0x8b7489c>, order=False, trace=False) source code
 
find_next_candidate(self)
Returns the next candidate Node for (potential) evaluation.
source code
 
no_next_candidate(self)
Stops Taskmaster processing by not returning a next candidate.
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_find_next_ready_node(self)
Finds the next node that is ready to be built.
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next_task(self)
Returns the next task to be executed.
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will_not_build(self, nodes, mark_fail=<function <lambda> at 0x8b6b064>)
Perform clean-up about nodes that will never be built.
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stop(self)
Stops the current build completely.
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cleanup(self)
Check for dependency cycles.
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Method Details [hide private]

find_next_candidate(self)

source code 

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."

no_next_candidate(self)

source code 

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.

_find_next_ready_node(self)

source code 

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.

next_task(self)

source code 

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.