watchrobot/modules/waf/playground/dynamic_recursive_tasks/wscript

#! /usr/bin/env python
# encoding: utf-8
# Thomas Nagy, 2010 (ita)

VERSION='0.0.1'
APPNAME='crazy_test'

top = '.'
out = 'build'

def options(opt):
	opt.load('compiler_cxx')

def configure(conf):
	conf.load('compiler_cxx')

def build(bld):
	bld.program(source='main.cpp', target='app')

"""
Only main.cpp is added to the program, then by looking at the include files,
a <file.h> file is found. If a corresponding <file.cpp> exists,
then a new c++ task is created to compile that file and to add it to the
program (modify the link task).

The idea is to change the method runnable_status of the task. A more correct but less obvious
approach would be the creation of a specific c++ subclass, and using another
extension mapping function (@extension).
"""

from waflib.Task import ASK_LATER
from waflib.Tools.cxx import cxx
def runnable_status(self):
	ret = super(cxx, self).runnable_status()
	self.more_tasks = []

	# use a cache to avoid creating the same tasks
	# for example, truc.cpp might be compiled twice
	try:
		shared = self.generator.bld.shared_tasks
	except AttributeError:
		shared = self.generator.bld.shared_tasks = {}

	if ret != ASK_LATER:
		for x in self.generator.bld.node_deps[self.uid()]:
			node = x.parent.get_src().find_resource(x.name.replace('.h', '.cpp'))
			if node:
				try:
					tsk = shared[node]
				except:
					tsk = shared[node] = self.generator.cxx_hook(node)

					self.more_tasks.append(tsk)


				# add the node created to the link task outputs
				try:
					link = self.generator.link_task
				except AttributeError:
					pass
				else:
					if not tsk.outputs[0] in link.inputs:
						link.inputs.append(tsk.outputs[0])
						link.set_run_after(tsk)

						# any change in the order of the input nodes may cause a recompilation
						link.inputs.sort(key=lambda x: x.abspath())

		# if you want to modify some flags
		# you *must* have the task recompute the signature
		self.env.append_value('CXXFLAGS', '-O2')
		delattr(self, 'cache_sig')
		return super(cxx, self).runnable_status()

	return ret

cxx.runnable_status = runnable_status