waf

TaskGen.py (26525B)

---

 #!/usr/bin/env python
 # encoding: utf-8
 # Thomas Nagy, 2005-2018 (ita)
 
 """
 Task generators
 
 The class :py:class:`waflib.TaskGen.task_gen` encapsulates the creation of task objects (low-level code)
 The instances can have various parameters, but the creation of task nodes (Task.py)
 is deferred. To achieve this, various methods are called from the method "apply"
 """
 
 import copy, re, os, functools
 from waflib import Task, Utils, Logs, Errors, ConfigSet, Node
 
 feats = Utils.defaultdict(set)
 """remember the methods declaring features"""
 
 HEADER_EXTS = ['.h', '.hpp', '.hxx', '.hh']
 
 class task_gen(object):
 	"""
 	Instances of this class create :py:class:`waflib.Task.Task` when
 	calling the method :py:meth:`waflib.TaskGen.task_gen.post` from the main thread.
 	A few notes:
 
 	* The methods to call (*self.meths*) can be specified dynamically (removing, adding, ..)
 	* The 'features' are used to add methods to self.meths and then execute them
 	* The attribute 'path' is a node representing the location of the task generator
 	* The tasks created are added to the attribute *tasks*
 	* The attribute 'idx' is a counter of task generators in the same path
 	"""
 
 	mappings = Utils.ordered_iter_dict()
 	"""Mappings are global file extension mappings that are retrieved in the order of definition"""
 
 	prec = Utils.defaultdict(set)
 	"""Dict that holds the precedence execution rules for task generator methods"""
 
 	def __init__(self, *k, **kw):
 		"""
 		Task generator objects predefine various attributes (source, target) for possible
 		processing by process_rule (make-like rules) or process_source (extensions, misc methods)
 
 		Tasks are stored on the attribute 'tasks'. They are created by calling methods
 		listed in ``self.meths`` or referenced in the attribute ``features``
 		A topological sort is performed to execute the methods in correct order.
 
 		The extra key/value elements passed in ``kw`` are set as attributes
 		"""
 		self.source = []
 		self.target = ''
 
 		self.meths = []
 		"""
 		List of method names to execute (internal)
 		"""
 
 		self.features = []
 		"""
 		List of feature names for bringing new methods in
 		"""
 
 		self.tasks = []
 		"""
 		Tasks created are added to this list
 		"""
 
 		if not 'bld' in kw:
 			# task generators without a build context :-/
 			self.env = ConfigSet.ConfigSet()
 			self.idx = 0
 			self.path = None
 		else:
 			self.bld = kw['bld']
 			self.env = self.bld.env.derive()
 			self.path = kw.get('path', self.bld.path) # by default, emulate chdir when reading scripts
 
 			# Provide a unique index per folder
 			# This is part of a measure to prevent output file name collisions
 			path = self.path.abspath()
 			try:
 				self.idx = self.bld.idx[path] = self.bld.idx.get(path, 0) + 1
 			except AttributeError:
 				self.bld.idx = {}
 				self.idx = self.bld.idx[path] = 1
 
 			# Record the global task generator count
 			try:
 				self.tg_idx_count = self.bld.tg_idx_count = self.bld.tg_idx_count + 1
 			except AttributeError:
 				self.tg_idx_count = self.bld.tg_idx_count = 1
 
 		for key, val in kw.items():
 			setattr(self, key, val)
 
 	def __str__(self):
 		"""Debugging helper"""
 		return "<task_gen %r declared in %s>" % (self.name, self.path.abspath())
 
 	def __repr__(self):
 		"""Debugging helper"""
 		lst = []
 		for x in self.__dict__:
 			if x not in ('env', 'bld', 'compiled_tasks', 'tasks'):
 				lst.append("%s=%s" % (x, repr(getattr(self, x))))
 		return "bld(%s) in %s" % (", ".join(lst), self.path.abspath())
 
 	def get_cwd(self):
 		"""
 		Current working directory for the task generator, defaults to the build directory.
 		This is still used in a few places but it should disappear at some point as the classes
 		define their own working directory.
 
 		:rtype: :py:class:`waflib.Node.Node`
 		"""
 		return self.bld.bldnode
 
 	def get_name(self):
 		"""
 		If the attribute ``name`` is not set on the instance,
 		the name is computed from the target name::
 
 			def build(bld):
 				x = bld(name='foo')
 				x.get_name() # foo
 				y = bld(target='bar')
 				y.get_name() # bar
 
 		:rtype: string
 		:return: name of this task generator
 		"""
 		try:
 			return self._name
 		except AttributeError:
 			if isinstance(self.target, list):
 				lst = [str(x) for x in self.target]
 				name = self._name = ','.join(lst)
 			else:
 				name = self._name = str(self.target)
 			return name
 	def set_name(self, name):
 		self._name = name
 
 	name = property(get_name, set_name)
 
 	def to_list(self, val):
 		"""
 		Ensures that a parameter is a list, see :py:func:`waflib.Utils.to_list`
 
 		:type val: string or list of string
 		:param val: input to return as a list
 		:rtype: list
 		"""
 		if isinstance(val, str):
 			return val.split()
 		else:
 			return val
 
 	def post(self):
 		"""
 		Creates tasks for this task generators. The following operations are performed:
 
 		#. The body of this method is called only once and sets the attribute ``posted``
 		#. The attribute ``features`` is used to add more methods in ``self.meths``
 		#. The methods are sorted by the precedence table ``self.prec`` or `:waflib:attr:waflib.TaskGen.task_gen.prec`
 		#. The methods are then executed in order
 		#. The tasks created are added to :py:attr:`waflib.TaskGen.task_gen.tasks`
 		"""
 		if getattr(self, 'posted', None):
 			return False
 		self.posted = True
 
 		keys = set(self.meths)
 		keys.update(feats['*'])
 
 		# add the methods listed in the features
 		self.features = Utils.to_list(self.features)
 		for x in self.features:
 			st = feats[x]
 			if st:
 				keys.update(st)
 			elif not x in Task.classes:
 				Logs.warn('feature %r does not exist - bind at least one method to it?', x)
 
 		# copy the precedence table
 		prec = {}
 		prec_tbl = self.prec
 		for x in prec_tbl:
 			if x in keys:
 				prec[x] = prec_tbl[x]
 
 		# elements disconnected
 		tmp = []
 		for a in keys:
 			for x in prec.values():
 				if a in x:
 					break
 			else:
 				tmp.append(a)
 
 		tmp.sort(reverse=True)
 
 		# topological sort
 		out = []
 		while tmp:
 			e = tmp.pop()
 			if e in keys:
 				out.append(e)
 			try:
 				nlst = prec[e]
 			except KeyError:
 				pass
 			else:
 				del prec[e]
 				for x in nlst:
 					for y in prec:
 						if x in prec[y]:
 							break
 					else:
 						tmp.append(x)
 						tmp.sort(reverse=True)
 
 		if prec:
 			buf = ['Cycle detected in the method execution:']
 			for k, v in prec.items():
 				buf.append('- %s after %s' % (k, [x for x in v if x in prec]))
 			raise Errors.WafError('\n'.join(buf))
 		self.meths = out
 
 		# then we run the methods in order
 		Logs.debug('task_gen: posting %s %d', self, id(self))
 		for x in out:
 			try:
 				v = getattr(self, x)
 			except AttributeError:
 				raise Errors.WafError('%r is not a valid task generator method' % x)
 			Logs.debug('task_gen: -> %s (%d)', x, id(self))
 			v()
 
 		Logs.debug('task_gen: posted %s', self.name)
 		return True
 
 	def get_hook(self, node):
 		"""
 		Returns the ``@extension`` method to call for a Node of a particular extension.
 
 		:param node: Input file to process
 		:type node: :py:class:`waflib.Tools.Node.Node`
 		:return: A method able to process the input node by looking at the extension
 		:rtype: function
 		"""
 		name = node.name
 		for k in self.mappings:
 			try:
 				if name.endswith(k):
 					return self.mappings[k]
 			except TypeError:
 				# regexps objects
 				if k.match(name):
 					return self.mappings[k]
 		keys = list(self.mappings.keys())
 		raise Errors.WafError("File %r has no mapping in %r (load a waf tool?)" % (node, keys))
 
 	def create_task(self, name, src=None, tgt=None, **kw):
 		"""
 		Creates task instances.
 
 		:param name: task class name
 		:type name: string
 		:param src: input nodes
 		:type src: list of :py:class:`waflib.Tools.Node.Node`
 		:param tgt: output nodes
 		:type tgt: list of :py:class:`waflib.Tools.Node.Node`
 		:return: A task object
 		:rtype: :py:class:`waflib.Task.Task`
 		"""
 		task = Task.classes[name](env=self.env.derive(), generator=self)
 		if src:
 			task.set_inputs(src)
 		if tgt:
 			task.set_outputs(tgt)
 		task.__dict__.update(kw)
 		self.tasks.append(task)
 		return task
 
 	def clone(self, env):
 		"""
 		Makes a copy of a task generator. Once the copy is made, it is necessary to ensure that the
 		it does not create the same output files as the original, or the same files may
 		be compiled several times.
 
 		:param env: A configuration set
 		:type env: :py:class:`waflib.ConfigSet.ConfigSet`
 		:return: A copy
 		:rtype: :py:class:`waflib.TaskGen.task_gen`
 		"""
 		newobj = self.bld()
 		for x in self.__dict__:
 			if x in ('env', 'bld'):
 				continue
 			elif x in ('path', 'features'):
 				setattr(newobj, x, getattr(self, x))
 			else:
 				setattr(newobj, x, copy.copy(getattr(self, x)))
 
 		newobj.posted = False
 		if isinstance(env, str):
 			newobj.env = self.bld.all_envs[env].derive()
 		else:
 			newobj.env = env.derive()
 
 		return newobj
 
 def declare_chain(name='', rule=None, reentrant=None, color='BLUE',
 	ext_in=[], ext_out=[], before=[], after=[], decider=None, scan=None, install_path=None, shell=False):
 	"""
 	Creates a new mapping and a task class for processing files by extension.
 	See Tools/flex.py for an example.
 
 	:param name: name for the task class
 	:type name: string
 	:param rule: function to execute or string to be compiled in a function
 	:type rule: string or function
 	:param reentrant: re-inject the output file in the process (done automatically, set to 0 to disable)
 	:type reentrant: int
 	:param color: color for the task output
 	:type color: string
 	:param ext_in: execute the task only after the files of such extensions are created
 	:type ext_in: list of string
 	:param ext_out: execute the task only before files of such extensions are processed
 	:type ext_out: list of string
 	:param before: execute instances of this task before classes of the given names
 	:type before: list of string
 	:param after: execute instances of this task after classes of the given names
 	:type after: list of string
 	:param decider: if present, function that returns a list of output file extensions (overrides ext_out for output files, but not for the build order)
 	:type decider: function
 	:param scan: scanner function for the task
 	:type scan: function
 	:param install_path: installation path for the output nodes
 	:type install_path: string
 	"""
 	ext_in = Utils.to_list(ext_in)
 	ext_out = Utils.to_list(ext_out)
 	if not name:
 		name = rule
 	cls = Task.task_factory(name, rule, color=color, ext_in=ext_in, ext_out=ext_out, before=before, after=after, scan=scan, shell=shell)
 
 	def x_file(self, node):
 		if ext_in:
 			_ext_in = ext_in[0]
 
 		tsk = self.create_task(name, node)
 		cnt = 0
 
 		ext = decider(self, node) if decider else cls.ext_out
 		for x in ext:
 			k = node.change_ext(x, ext_in=_ext_in)
 			tsk.outputs.append(k)
 
 			if reentrant != None:
 				if cnt < int(reentrant):
 					self.source.append(k)
 			else:
 				# reinject downstream files into the build
 				for y in self.mappings: # ~ nfile * nextensions :-/
 					if k.name.endswith(y):
 						self.source.append(k)
 						break
 			cnt += 1
 
 		if install_path:
 			self.install_task = self.add_install_files(install_to=install_path, install_from=tsk.outputs)
 		return tsk
 
 	for x in cls.ext_in:
 		task_gen.mappings[x] = x_file
 	return x_file
 
 def taskgen_method(func):
 	"""
 	Decorator that registers method as a task generator method.
 	The function must accept a task generator as first parameter::
 
 		from waflib.TaskGen import taskgen_method
 		@taskgen_method
 		def mymethod(self):
 			pass
 
 	:param func: task generator method to add
 	:type func: function
 	:rtype: function
 	"""
 	setattr(task_gen, func.__name__, func)
 	return func
 
 def feature(*k):
 	"""
 	Decorator that registers a task generator method that will be executed when the
 	object attribute ``feature`` contains the corresponding key(s)::
 
 		from waflib.TaskGen import feature
 		@feature('myfeature')
 		def myfunction(self):
 			print('that is my feature!')
 		def build(bld):
 			bld(features='myfeature')
 
 	:param k: feature names
 	:type k: list of string
 	"""
 	def deco(func):
 		setattr(task_gen, func.__name__, func)
 		for name in k:
 			feats[name].update([func.__name__])
 		return func
 	return deco
 
 def before_method(*k):
 	"""
 	Decorator that registera task generator method which will be executed
 	before the functions of given name(s)::
 
 		from waflib.TaskGen import feature, before
 		@feature('myfeature')
 		@before_method('fun2')
 		def fun1(self):
 			print('feature 1!')
 		@feature('myfeature')
 		def fun2(self):
 			print('feature 2!')
 		def build(bld):
 			bld(features='myfeature')
 
 	:param k: method names
 	:type k: list of string
 	"""
 	def deco(func):
 		setattr(task_gen, func.__name__, func)
 		for fun_name in k:
 			task_gen.prec[func.__name__].add(fun_name)
 		return func
 	return deco
 before = before_method
 
 def after_method(*k):
 	"""
 	Decorator that registers a task generator method which will be executed
 	after the functions of given name(s)::
 
 		from waflib.TaskGen import feature, after
 		@feature('myfeature')
 		@after_method('fun2')
 		def fun1(self):
 			print('feature 1!')
 		@feature('myfeature')
 		def fun2(self):
 			print('feature 2!')
 		def build(bld):
 			bld(features='myfeature')
 
 	:param k: method names
 	:type k: list of string
 	"""
 	def deco(func):
 		setattr(task_gen, func.__name__, func)
 		for fun_name in k:
 			task_gen.prec[fun_name].add(func.__name__)
 		return func
 	return deco
 after = after_method
 
 def extension(*k):
 	"""
 	Decorator that registers a task generator method which will be invoked during
 	the processing of source files for the extension given::
 
 		from waflib import Task
 		class mytask(Task):
 			run_str = 'cp ${SRC} ${TGT}'
 		@extension('.moo')
 		def create_maa_file(self, node):
 			self.create_task('mytask', node, node.change_ext('.maa'))
 		def build(bld):
 			bld(source='foo.moo')
 	"""
 	def deco(func):
 		setattr(task_gen, func.__name__, func)
 		for x in k:
 			task_gen.mappings[x] = func
 		return func
 	return deco
 
 @taskgen_method
 def to_nodes(self, lst, path=None):
 	"""
 	Flatten the input list of string/nodes/lists into a list of nodes.
 
 	It is used by :py:func:`waflib.TaskGen.process_source` and :py:func:`waflib.TaskGen.process_rule`.
 	It is designed for source files, for folders, see :py:func:`waflib.Tools.ccroot.to_incnodes`:
 
 	:param lst: input list
 	:type lst: list of string and nodes
 	:param path: path from which to search the nodes (by default, :py:attr:`waflib.TaskGen.task_gen.path`)
 	:type path: :py:class:`waflib.Tools.Node.Node`
 	:rtype: list of :py:class:`waflib.Tools.Node.Node`
 	"""
 	tmp = []
 	path = path or self.path
 	find = path.find_resource
 
 	if isinstance(lst, Node.Node):
 		lst = [lst]
 
 	for x in Utils.to_list(lst):
 		if isinstance(x, str):
 			node = find(x)
 		elif hasattr(x, 'name'):
 			node = x
 		else:
 			tmp.extend(self.to_nodes(x))
 			continue
 		if not node:
 			raise Errors.WafError('source not found: %r in %r' % (x, self))
 		tmp.append(node)
 	return tmp
 
 @feature('*')
 def process_source(self):
 	"""
 	Processes each element in the attribute ``source`` by extension.
 
 	#. The *source* list is converted through :py:meth:`waflib.TaskGen.to_nodes` to a list of :py:class:`waflib.Node.Node` first.
 	#. File extensions are mapped to methods having the signature: ``def meth(self, node)`` by :py:meth:`waflib.TaskGen.extension`
 	#. The method is retrieved through :py:meth:`waflib.TaskGen.task_gen.get_hook`
 	#. When called, the methods may modify self.source to append more source to process
 	#. The mappings can map an extension or a filename (see the code below)
 	"""
 	self.source = self.to_nodes(getattr(self, 'source', []))
 	for node in self.source:
 		self.get_hook(node)(self, node)
 
 @feature('*')
 @before_method('process_source')
 def process_rule(self):
 	"""
 	Processes the attribute ``rule``. When present, :py:meth:`waflib.TaskGen.process_source` is disabled::
 
 		def build(bld):
 			bld(rule='cp ${SRC} ${TGT}', source='wscript', target='bar.txt')
 
 	Main attributes processed:
 
 	* rule: command to execute, it can be a tuple of strings for multiple commands
 	* chmod: permissions for the resulting files (integer value such as Utils.O755)
 	* shell: set to False to execute the command directly (default is True to use a shell)
 	* scan: scanner function
 	* vars: list of variables to trigger rebuilds, such as CFLAGS
 	* cls_str: string to display when executing the task
 	* cls_keyword: label to display when executing the task
 	* cache_rule: by default, try to re-use similar classes, set to False to disable
 	* source: list of Node or string objects representing the source files required by this task
 	* target: list of Node or string objects representing the files that this task creates
 	* cwd: current working directory (Node or string)
 	* stdout: standard output, set to None to prevent waf from capturing the text
 	* stderr: standard error, set to None to prevent waf from capturing the text
 	* timeout: timeout for command execution (Python 3)
 	* always: whether to always run the command (False by default)
 	* deep_inputs: whether the task must depend on the input file tasks too (False by default)
 	"""
 	if not getattr(self, 'rule', None):
 		return
 
 	# create the task class
 	name = str(getattr(self, 'name', None) or self.target or getattr(self.rule, '__name__', self.rule))
 
 	# or we can put the class in a cache for performance reasons
 	try:
 		cache = self.bld.cache_rule_attr
 	except AttributeError:
 		cache = self.bld.cache_rule_attr = {}
 
 	chmod = getattr(self, 'chmod', None)
 	shell = getattr(self, 'shell', True)
 	color = getattr(self, 'color', 'BLUE')
 	scan = getattr(self, 'scan', None)
 	_vars = getattr(self, 'vars', [])
 	cls_str = getattr(self, 'cls_str', None)
 	cls_keyword = getattr(self, 'cls_keyword', None)
 	use_cache = getattr(self, 'cache_rule', 'True')
 	deep_inputs = getattr(self, 'deep_inputs', False)
 
 	scan_val = has_deps = hasattr(self, 'deps')
 	if scan:
 		scan_val = id(scan)
 
 	key = Utils.h_list((name, self.rule, chmod, shell, color, cls_str, cls_keyword, scan_val, _vars, deep_inputs))
 
 	cls = None
 	if use_cache:
 		try:
 			cls = cache[key]
 		except KeyError:
 			pass
 	if not cls:
 		rule = self.rule
 		if chmod is not None:
 			def chmod_fun(tsk):
 				for x in tsk.outputs:
 					os.chmod(x.abspath(), tsk.generator.chmod)
 			if isinstance(rule, tuple):
 				rule = list(rule)
 				rule.append(chmod_fun)
 				rule = tuple(rule)
 			else:
 				rule = (rule, chmod_fun)
 
 		cls = Task.task_factory(name, rule, _vars, shell=shell, color=color)
 
 		if cls_str:
 			setattr(cls, '__str__', self.cls_str)
 
 		if cls_keyword:
 			setattr(cls, 'keyword', self.cls_keyword)
 
 		if deep_inputs:
 			Task.deep_inputs(cls)
 
 		if scan:
 			cls.scan = self.scan
 		elif has_deps:
 			def scan(self):
 				deps = getattr(self.generator, 'deps', None)
 				nodes = self.generator.to_nodes(deps)
 				return [nodes, []]
 			cls.scan = scan
 
 		if use_cache:
 			cache[key] = cls
 
 	# now create one instance
 	tsk = self.create_task(name)
 
 	for x in ('after', 'before', 'ext_in', 'ext_out'):
 		setattr(tsk, x, getattr(self, x, []))
 
 	if hasattr(self, 'stdout'):
 		tsk.stdout = self.stdout
 
 	if hasattr(self, 'stderr'):
 		tsk.stderr = self.stderr
 
 	if getattr(self, 'timeout', None):
 		tsk.timeout = self.timeout
 
 	if getattr(self, 'always', None):
 		tsk.always_run = True
 
 	if getattr(self, 'target', None):
 		if isinstance(self.target, str):
 			self.target = self.target.split()
 		if not isinstance(self.target, list):
 			self.target = [self.target]
 		for x in self.target:
 			if isinstance(x, str):
 				tsk.outputs.append(self.path.find_or_declare(x))
 			else:
 				x.parent.mkdir() # if a node was given, create the required folders
 				tsk.outputs.append(x)
 		if getattr(self, 'install_path', None):
 			self.install_task = self.add_install_files(install_to=self.install_path,
 				install_from=tsk.outputs, chmod=getattr(self, 'chmod', Utils.O644))
 
 	if getattr(self, 'source', None):
 		tsk.inputs = self.to_nodes(self.source)
 		# bypass the execution of process_source by setting the source to an empty list
 		self.source = []
 
 	if getattr(self, 'cwd', None):
 		tsk.cwd = self.cwd
 
 	if isinstance(tsk.run, functools.partial):
 		# Python documentation says: "partial objects defined in classes
 		# behave like static methods and do not transform into bound
 		# methods during instance attribute look-up."
 		tsk.run = functools.partial(tsk.run, tsk)
 
 @feature('seq')
 def sequence_order(self):
 	"""
 	Adds a strict sequential constraint between the tasks generated by task generators.
 	It works because task generators are posted in order.
 	It will not post objects which belong to other folders.
 
 	Example::
 
 		bld(features='javac seq')
 		bld(features='jar seq')
 
 	To start a new sequence, set the attribute seq_start, for example::
 
 		obj = bld(features='seq')
 		obj.seq_start = True
 
 	Note that the method is executed in last position. This is more an
 	example than a widely-used solution.
 	"""
 	if self.meths and self.meths[-1] != 'sequence_order':
 		self.meths.append('sequence_order')
 		return
 
 	if getattr(self, 'seq_start', None):
 		return
 
 	# all the tasks previously declared must be run before these
 	if getattr(self.bld, 'prev', None):
 		self.bld.prev.post()
 		for x in self.bld.prev.tasks:
 			for y in self.tasks:
 				y.set_run_after(x)
 
 	self.bld.prev = self
 
 
 re_m4 = re.compile(r'@(\w+)@', re.M)
 
 class subst_pc(Task.Task):
 	"""
 	Creates *.pc* files from *.pc.in*. The task is executed whenever an input variable used
 	in the substitution changes.
 	"""
 
 	def force_permissions(self):
 		"Private for the time being, we will probably refactor this into run_str=[run1,chmod]"
 		if getattr(self.generator, 'chmod', None):
 			for x in self.outputs:
 				os.chmod(x.abspath(), self.generator.chmod)
 
 	def run(self):
 		"Substitutes variables in a .in file"
 
 		if getattr(self.generator, 'is_copy', None):
 			for i, x in enumerate(self.outputs):
 				x.write(self.inputs[i].read('rb'), 'wb')
 				stat = os.stat(self.inputs[i].abspath()) # Preserve mtime of the copy
 				os.utime(self.outputs[i].abspath(), (stat.st_atime, stat.st_mtime))
 			self.force_permissions()
 			return None
 
 		if getattr(self.generator, 'fun', None):
 			ret = self.generator.fun(self)
 			if not ret:
 				self.force_permissions()
 			return ret
 
 		code = self.inputs[0].read(encoding=getattr(self.generator, 'encoding', 'latin-1'))
 		if getattr(self.generator, 'subst_fun', None):
 			code = self.generator.subst_fun(self, code)
 			if code is not None:
 				self.outputs[0].write(code, encoding=getattr(self.generator, 'encoding', 'latin-1'))
 			self.force_permissions()
 			return None
 
 		# replace all % by %% to prevent errors by % signs
 		code = code.replace('%', '%%')
 
 		# extract the vars foo into lst and replace @foo@ by %(foo)s
 		lst = []
 		def repl(match):
 			g = match.group
 			if g(1):
 				lst.append(g(1))
 				return "%%(%s)s" % g(1)
 			return ''
 		code = getattr(self.generator, 're_m4', re_m4).sub(repl, code)
 
 		try:
 			d = self.generator.dct
 		except AttributeError:
 			d = {}
 			for x in lst:
 				tmp = getattr(self.generator, x, '') or self.env[x] or self.env[x.upper()]
 				try:
 					tmp = ''.join(tmp)
 				except TypeError:
 					tmp = str(tmp)
 				d[x] = tmp
 
 		code = code % d
 		self.outputs[0].write(code, encoding=getattr(self.generator, 'encoding', 'latin-1'))
 		self.generator.bld.raw_deps[self.uid()] = lst
 
 		# make sure the signature is updated
 		try:
 			delattr(self, 'cache_sig')
 		except AttributeError:
 			pass
 
 		self.force_permissions()
 
 	def sig_vars(self):
 		"""
 		Compute a hash (signature) of the variables used in the substitution
 		"""
 		bld = self.generator.bld
 		env = self.env
 		upd = self.m.update
 
 		if getattr(self.generator, 'fun', None):
 			upd(Utils.h_fun(self.generator.fun).encode())
 		if getattr(self.generator, 'subst_fun', None):
 			upd(Utils.h_fun(self.generator.subst_fun).encode())
 
 		# raw_deps: persistent custom values returned by the scanner
 		vars = self.generator.bld.raw_deps.get(self.uid(), [])
 
 		# hash both env vars and task generator attributes
 		act_sig = bld.hash_env_vars(env, vars)
 		upd(act_sig)
 
 		lst = [getattr(self.generator, x, '') for x in vars]
 		upd(Utils.h_list(lst))
 
 		return self.m.digest()
 
 @extension('.pc.in')
 def add_pcfile(self, node):
 	"""
 	Processes *.pc.in* files to *.pc*. Installs the results to ``${PREFIX}/lib/pkgconfig/`` by default
 
 		def build(bld):
 			bld(source='foo.pc.in', install_path='${LIBDIR}/pkgconfig/')
 	"""
 	tsk = self.create_task('subst_pc', node, node.change_ext('.pc', '.pc.in'))
 	self.install_task = self.add_install_files(
 		install_to=getattr(self, 'install_path', '${LIBDIR}/pkgconfig/'), install_from=tsk.outputs)
 
 class subst(subst_pc):
 	pass
 
 @feature('subst')
 @before_method('process_source', 'process_rule')
 def process_subst(self):
 	"""
 	Defines a transformation that substitutes the contents of *source* files to *target* files::
 
 		def build(bld):
 			bld(
 				features='subst',
 				source='foo.c.in',
 				target='foo.c',
 				install_path='${LIBDIR}/pkgconfig',
 				VAR = 'val'
 			)
 
 	The input files are supposed to contain macros of the form *@VAR@*, where *VAR* is an argument
 	of the task generator object.
 
 	This method overrides the processing by :py:meth:`waflib.TaskGen.process_source`.
 	"""
 
 	src = Utils.to_list(getattr(self, 'source', []))
 	if isinstance(src, Node.Node):
 		src = [src]
 	tgt = Utils.to_list(getattr(self, 'target', []))
 	if isinstance(tgt, Node.Node):
 		tgt = [tgt]
 	if len(src) != len(tgt):
 		raise Errors.WafError('invalid number of source/target for %r' % self)
 
 	for x, y in zip(src, tgt):
 		if not x or not y:
 			raise Errors.WafError('null source or target for %r' % self)
 		a, b = None, None
 
 		if isinstance(x, str) and isinstance(y, str) and x == y:
 			a = self.path.find_node(x)
 			b = self.path.get_bld().make_node(y)
 			if not os.path.isfile(b.abspath()):
 				b.parent.mkdir()
 		else:
 			if isinstance(x, str):
 				a = self.path.find_resource(x)
 			elif isinstance(x, Node.Node):
 				a = x
 			if isinstance(y, str):
 				b = self.path.find_or_declare(y)
 			elif isinstance(y, Node.Node):
 				b = y
 
 		if not a:
 			raise Errors.WafError('could not find %r for %r' % (x, self))
 
 		tsk = self.create_task('subst', a, b)
 		for k in ('after', 'before', 'ext_in', 'ext_out'):
 			val = getattr(self, k, None)
 			if val:
 				setattr(tsk, k, val)
 
 		# paranoid safety measure for the general case foo.in->foo.h with ambiguous dependencies
 		for xt in HEADER_EXTS:
 			if b.name.endswith(xt):
 				tsk.ext_out = tsk.ext_out + ['.h']
 				break
 
 		inst_to = getattr(self, 'install_path', None)
 		if inst_to:
 			self.install_task = self.add_install_files(install_to=inst_to,
 				install_from=b, chmod=getattr(self, 'chmod', Utils.O644))
 
 	self.source = []