Example to how how to obtain build dependencies through strace

playground/stracedeps/foo.sh

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+#! /bin/sh
+
+set -e
+cd /etc
+cat fstab > /dev/null
+

playground/stracedeps/wscript

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+#! /usr/bin/env python
+# encoding: utf-8
+# Thomas Nagy, 2015 (ita)
+
+VERSION='0.0.1'
+APPNAME='strace_test'
+
+from waflib import Logs
+def configure(conf):
+	Logs.warn("run with 'waf --zones=deps'")
+	conf.load('stracedeps')
+
+def build(bld):
+	bld(rule='${SRC[0].abspath()}', source='foo.sh', always=True, shell=1)
+

waflib/extras/stracedeps.py

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+#!/usr/bin/env python
+# encoding: utf-8
+# Thomas Nagy, 2015 (ita)
+
+"""
+Execute tasks through strace to obtain dependencies after the process is run. This
+scheme is similar to that of the Fabricate script.
+
+To use::
+
+  def configure(conf):
+     conf.load('strace')
+
+WARNING:
+* This will not work when advanced scanners are needed (qt4/qt5)
+* The overhead of running 'strace' is significant (56s -> 1m29s)
+* It will not work on Windows :-)
+"""
+
+import os, re, threading
+from waflib import Task, Logs, Utils
+
+#TRACECALLS = 'trace=access,chdir,clone,creat,execve,exit_group,fork,lstat,lstat64,mkdir,open,rename,stat,stat64,symlink,vfork'
+TRACECALLS = 'trace=process,file'
+
+BANNED = ('/tmp', '/proc', '/sys', '/dev')
+
+s_process = r'(?:clone|fork|vfork)\(.*?(?P<npid>\d+)'
+s_file = r'(?P<call>\w+)\("(?P<path>.*?[^\\])"(.*)'
+re_lines = re.compile(r'^(?P<pid>\d+)\s+(?:(?:%s)|(?:%s))\r*$' % (s_file, s_process), re.IGNORECASE | re.MULTILINE)
+strace_lock = threading.Lock()
+
+def configure(conf):
+	conf.find_program('strace')
+
+def task_method(func):
+	# Decorator function to bind/replace methods on the base Task class
+	#
+	# The methods Task.exec_command and Task.sig_implicit_deps already exists and are rarely overridden
+	# we thus expect that we are the only ones doing this
+	try:
+		setattr(Task.Task, 'nostrace_%s' % func.__name__, getattr(Task.Task, func.__name__))
+	except AttributeError:
+		pass
+	setattr(Task.Task, func.__name__, func)
+        return func
+
+@task_method
+def get_strace_file(self):
+	try:
+		return self.strace_file
+	except AttributeError:
+		pass
+
+	if self.outputs:
+		ret = self.outputs[0].abspath() + '.strace'
+	else:
+		ret = '%s%s%d%s' % (self.generator.bld.bldnode.abspath(), os.sep, id(self), '.strace')
+	self.strace_file = ret
+	return ret
+
+@task_method
+def get_strace_args(self):
+	return (self.env.STRACE or ['strace']) + ['-e', TRACECALLS, '-f', '-o', self.get_strace_file()]
+
+@task_method
+def exec_command(self, cmd, **kw):
+	bld = self.generator.bld
+	try:
+		if not kw.get('cwd', None):
+			kw['cwd'] = bld.cwd
+	except AttributeError:
+		bld.cwd = kw['cwd'] = bld.variant_dir
+
+	args = self.get_strace_args()
+	fname = self.get_strace_file()
+	if isinstance(cmd, list):
+		cmd = args + cmd
+	else:
+		cmd = '%s %s' % (' '.join(args), cmd)
+
+	try:
+		ret = bld.exec_command(cmd, **kw)
+	finally:
+		if not ret:
+			self.parse_strace_deps(fname, kw['cwd'])
+	return ret
+
+@task_method
+def sig_implicit_deps(self):
+	# bypass the scanner functions
+	return
+
+@task_method
+def parse_strace_deps(self, path, cwd):
+	# uncomment the following line to disable the dependencies and force a file scan
+	# return
+	try:
+		cnt = Utils.readf(path)
+	finally:
+		try:
+			os.remove(path)
+		except OSError:
+			pass
+
+	nodes = []
+	bld = self.generator.bld
+	try:
+		cache = bld.strace_cache
+	except AttributeError:
+		cache = bld.strace_cache = {}
+
+	# chdir and relative paths
+	pid_to_cwd = {}
+
+	global BANNED
+	done = set([])
+	for m in re.finditer(re_lines, cnt):
+		# scraping the output of strace
+		pid = m.group('pid')
+		if m.group('npid'):
+			npid = m.group('npid')
+			pid_to_cwd[npid] = pid_to_cwd.get(pid, cwd)
+			continue
+
+		p = m.group('path')
+
+		if p == '.' or m.group().find('= -1 ENOENT') > -1:
+			# just to speed it up a bit
+			continue
+
+		if not os.path.isabs(p):
+			p = os.path.join(pid_to_cwd.get(pid, cwd), p)
+
+		call = m.group('call')
+		if call == 'chdir':
+			pid_to_cwd[pid] = p
+			continue
+
+		if p in done:
+			continue
+		done.add(p)
+
+		for x in BANNED:
+			if p.startswith(x):
+				break
+		else:
+			if p.endswith('/') or os.path.isdir(p):
+				continue
+
+			try:
+				node = cache[p]
+			except KeyError:
+				strace_lock.acquire()
+				try:
+					cache[p] = node = bld.root.find_node(p)
+					if not node:
+						continue
+				finally:
+					strace_lock.release()
+			nodes.append(node)
+
+	# record the dependencies then force the task signature recalculation for next time
+	if Logs.verbose:
+		Logs.debug('deps: real scanner for %s returned %s' % (str(self), str(nodes)))
+	bld = self.generator.bld
+	bld.node_deps[self.uid()] = nodes
+	bld.raw_deps[self.uid()] = []
+	try:
+		del self.cache_sig
+	except AttributeError:
+		pass
+	self.signature()
+