def do_link(self, src, tgt):
		"""
		Create a symlink from tgt to src.

		This method is overridden in :py:meth:`waflib.Build.UninstallContext.do_link` to remove the symlink.

		:param src: file name as absolute path
		:type src: string
		:param tgt: file destination, as absolute path
		:type tgt: string
		"""
		d, _ = os.path.split(tgt)
		Utils.check_dir(d)

		link = False
		if not os.path.islink(tgt):
			link = True
		elif os.readlink(tgt) != src:
			link = True

		if link:
			try: os.remove(tgt)
			except OSError: pass
			if not self.progress_bar:
				Logs.info('+ symlink %s (to %s)' % (tgt, src))
			os.symlink(src, tgt)
		else:
			if not self.progress_bar:
				Logs.info('- symlink %s (to %s)' % (tgt, src))

	def env_path(parent_dir_var,name):
		parent=os.getenv(parent_dir_var)
		if parent:
			return os.path.join(parent,name)
		else:
			Logs.warn('Environment variable %s unset, using LIBDIR\n'%parent_dir_var)
			return os.path.join(conf.env['LIBDIR'],name)

	def ant_glob(self,*k,**kw):
		if k:
			lst=Utils.to_list(k[0])
			for pat in lst:
				if'..'in pat.split('/'):
					Logs.error("In ant_glob pattern %r: '..' means 'two dots', not 'parent directory'"%k[0])
		return old_ant_glob(self,*k,**kw)

 def runnable_status(self):
     for t in self.run_after:
         if not t.hasrun:
             return ASK_LATER
     bld = self.generator.bld
     try:
         new_sig = self.signature()
     except Errors.TaskNotReady:
         return ASK_LATER
     key = self.uid()
     try:
         prev_sig = bld.task_sigs[key]
     except KeyError:
         Logs.debug("task: task %r must run as it was never run before or the task code changed" % self)
         return RUN_ME
     for node in self.outputs:
         try:
             if node.sig != new_sig:
                 return RUN_ME
         except AttributeError:
             Logs.debug("task: task %r must run as the output nodes do not exist" % self)
             return RUN_ME
     if new_sig != prev_sig:
         return RUN_ME
     return SKIP_ME

	def clean(self):
		"""
		Remove most files from the build directory, and reset all caches.

		Custom lists of files to clean can be declared as `bld.clean_files`.
		For example, exclude `build/program/myprogram` from getting removed::

			def build(bld):
				bld.clean_files = bld.bldnode.ant_glob('**',
					excl='.lock* config.log c4che/* config.h program/myprogram',
					quiet=True, generator=True)
		"""
		Logs.debug('build: clean called')

		if hasattr(self, 'clean_files'):
			for n in self.clean_files:
				n.delete()
		elif self.bldnode != self.srcnode:
			# would lead to a disaster if top == out
			lst = []
			for env in self.all_envs.values():
				lst.extend(self.root.find_or_declare(f) for f in env[CFG_FILES])
			for n in self.bldnode.ant_glob('**/*', excl='.lock* *conf_check_*/** config.log c4che/*', quiet=True):
				if n in lst:
					continue
				n.delete()
		self.root.children = {}

		for v in SAVED_ATTRS:
			if v == 'root':
				continue
			setattr(self, v, {})

def distclean_dir(dirname):
	"""
	Distclean function called in the particular case when::

		top == out

	:param dirname: absolute path of the folder to clean
	:type dirname: string
	"""
	for (root, dirs, files) in os.walk(dirname):
		for f in files:
			if _can_distclean(f):
				fname = os.path.join(root, f)
				try:
					os.remove(fname)
				except OSError:
					Logs.warn('Could not remove %r' % fname)

	for x in (Context.DBFILE, 'config.log'):
		try:
			os.remove(x)
		except OSError:
			pass

	try:
		shutil.rmtree('c4che')
	except OSError:
		pass

	def exec_command(self, cmd, **kw):
		"""
		execute a command, return the exit status
		if the context has the attribute 'log', capture and log the process stderr/stdout

		this method should be used whenever possible for proper logging

		@param cmd: args for subprocess.Popen
		@param kw: keyword arguments for subprocess.Popen
		"""
		subprocess = Utils.subprocess
		kw['shell'] = isinstance(cmd, str)
		Logs.debug('runner: %r' % cmd)

		try:
			if self.logger:
				# warning: may deadlock with a lot of output (subprocess limitation)

				self.logger.info(cmd)

				kw['stdout'] = kw['stderr'] = subprocess.PIPE
				p = subprocess.Popen(cmd, **kw)
				(out, err) = p.communicate()
				if out:
					self.logger.debug('out: %s' % out.decode('utf-8'))
				if err:
					self.logger.error('err: %s' % err.decode('utf-8'))
				return p.returncode
			else:
				p = subprocess.Popen(cmd, **kw)
				return p.wait()
		except OSError:
			return -1

def download_tool(tool,force=False,ctx=None):
	for x in Utils.to_list(Context.remote_repo):
		for sub in Utils.to_list(Context.remote_locs):
			url='/'.join((x,sub,tool+'.py'))
			try:
				web=urlopen(url)
				try:
					if web.getcode()!=200:
						continue
				except AttributeError:
					pass
			except Exception:
				continue
			else:
				tmp=ctx.root.make_node(os.sep.join((Context.waf_dir,'waflib','extras',tool+'.py')))
				tmp.write(web.read(),'wb')
				Logs.warn('Downloaded %s from %s'%(tool,url))
				download_check(tmp)
				try:
					module=Context.load_tool(tool)
				except Exception:
					Logs.warn('The tool %s from %s is unusable'%(tool,url))
					try:
						tmp.delete()
					except Exception:
						pass
					continue
				return module
	raise Errors.WafError('Could not load the Waf tool')

def get_ccenv(fname):
	'''Returns dictionary of variant C/C++ build environments. In which the keys
	are the name of the actual variant C/C++ build environments and its values the
	settings for that variant build environment.
	
	:param fname: Complete path to the configuration file.
	:type fname: str
	'''
	if not os.path.exists(fname):
		Logs.warn("CCENV: ini file '%s' not found!" % fname)
	ccenv = {}
	c = configparser.ConfigParser()
	c.read(fname)
	for s in c.sections():
		ccenv[s] = {'prefix' : None, 'shlib' : [], 'env' : [], 'c': ['gcc'], 'cxx': ['g++', 'cpp']}
		if c.has_option(s, 'c'):
			ccenv[s]['c'] = c.get(s,'c').split(',')
		if c.has_option(s, 'cxx'):
			ccenv[s]['cxx'] = c.get(s,'cxx').split(',')
		if c.has_option(s, 'prefix'):
			ccenv[s]['prefix'] = c.get(s,'prefix')
		if c.has_option(s, 'shlib'):
			ccenv[s]['shlib'] = [l for l in str(c.get(s,'shlib')).split(',') if len(l)]
		if c.has_option(s, 'env'):
			ccenv[s]['env'] = [l.split('\t') for l in c.get(s,'env').splitlines() if len(l)]
		if c.has_option(s, 'host'):
			ccenv[s]['host'] = c.get(s,'host')
	return ccenv

def distclean_dir(dirname):
	"""
	Distclean function called in the particular case when::

		top == out

	:param dirname: absolute path of the folder to clean
	:type dirname: string
	"""
	for (root, dirs, files) in os.walk(dirname):
		for f in files:
			if _can_distclean(f):
				fname = root + os.sep + f
				try:
					os.unlink(fname)
				except:
					Logs.warn('could not remove %r' % fname)

	for x in [Context.DBFILE, 'config.log']:
		try:
			os.unlink(x)
		except:
			pass

	try:
		shutil.rmtree('c4che')
	except:
		pass

 def restore(self):
     try:
         env = ConfigSet.ConfigSet(os.path.join(self.cache_dir, "build.config.py"))
     except (IOError, OSError):
         pass
     else:
         if env["version"] < Context.HEXVERSION:
             raise Errors.WafError("Version mismatch! reconfigure the project")
         for t in env["tools"]:
             self.setup(**t)
     f = None
     try:
         try:
             f = open(os.path.join(self.variant_dir, Context.DBFILE), "rb")
         except (IOError, EOFError):
             Logs.debug("build: could not load the build cache (missing)")
         else:
             try:
                 waflib.Node.pickle_lock.acquire()
                 waflib.Node.Nod3 = self.node_class
                 try:
                     data = cPickle.load(f)
                 except Exception, e:
                     Logs.debug("build: could not load the build cache %r" % e)
                 else:
                     for x in SAVED_ATTRS:
                         setattr(self, x, data[x])

def build_version_files(header_path, source_path, domain, major, minor, micro, exportname, visheader):
    header_path = os.path.abspath(header_path)
    source_path = os.path.abspath(source_path)
    text  = "int " + domain + "_major_version = " + str(major) + ";\n"
    text += "int " + domain + "_minor_version = " + str(minor) + ";\n"
    text += "int " + domain + "_micro_version = " + str(micro) + ";\n"
    try:
        o = open(source_path, 'w')
        o.write(text)
        o.close()
    except IOError:
        Logs.error('Failed to open %s for writing\n' % source_path)
        sys.exit(-1)

    text  = "#ifndef __" + domain + "_version_h__\n"
    text += "#define __" + domain + "_version_h__\n"
    if visheader != '':
        text += "#include \"" + visheader + "\"\n"
    text += exportname + " extern const char* " + domain + "_revision;\n"
    text += exportname + " extern int " + domain + "_major_version;\n"
    text += exportname + " extern int " + domain + "_minor_version;\n"
    text += exportname + " extern int " + domain + "_micro_version;\n"
    text += "#endif /* __" + domain + "_version_h__ */\n"
    try:
        o = open(header_path, 'w')
        o.write(text)
        o.close()
    except IOError:
        Logs.warn('Failed to open %s for writing\n' % header_path)
        sys.exit(-1)

    return None

	def end_msg(self, *k, **kw):
		"""Print the end of a 'Checking for' message. See :py:meth:`waflib.Context.Context.msg`"""
		if kw.get('quiet', None):
			return
		self.in_msg -= 1
		if self.in_msg:
			return

		result = kw.get('result', None) or k[0]

		defcolor = 'GREEN'
		if result == True:
			msg = 'ok'
		elif result == False:
			msg = 'not found'
			defcolor = 'YELLOW'
		else:
			msg = str(result)

		self.to_log(msg)
		try:
			color = kw['color']
		except KeyError:
			if len(k) > 1 and k[1] in Logs.colors_lst:
				# compatibility waf 1.7
				color = k[1]
			else:
				color = defcolor
		Logs.pprint(color, msg)

		def parse_node(node):
			if node in seen:
				return
			seen.append(node)
			code = node.read()
			global re_tex
			for match in re_tex.finditer(code):
				for path in match.group('file').split(','):
					if path:
						add_name = True
						found = None
						for k in exts_deps_tex:
							Logs.debug('tex: trying %s%s' % (path, k))
							found = node.parent.find_resource(path + k)

							for tsk in self.generator.tasks:
								if not found or found in tsk.outputs:
									break
							else:
								nodes.append(found)
								add_name = False
								for ext in exts_tex:
									if found.name.endswith(ext):
										parse_node(found)
										break
							# no break, people are crazy
						if add_name:
							names.append(path)

def write_compilation_database(ctx):
	"Write the clang compilation database as JSON"
	database_file = ctx.bldnode.make_node('compile_commands.json')
	Logs.info('Build commands will be stored in %s', database_file.path_from(ctx.path))
	try:
		root = json.load(database_file)
	except IOError:
		root = []
	clang_db = dict((x['file'], x) for x in root)
	for task in getattr(ctx, 'clang_compilation_database_tasks', []):
		try:
			cmd = task.last_cmd
		except AttributeError:
			continue
		directory = getattr(task, 'cwd', ctx.variant_dir)
		f_node = task.inputs[0]
		filename = os.path.relpath(f_node.abspath(), directory)
		entry = {
			"directory": directory,
			"arguments": cmd,
			"file": filename,
		}
		clang_db[filename] = entry
	root = list(clang_db.values())
	database_file.write(json.dumps(root, indent=2))

	def load(self,filename):
		tbl=self.table
		code=Utils.readf(filename,m='rU')
		for m in re_imp.finditer(code):
			g=m.group
			tbl[g(2)]=eval(g(3))
		Logs.debug('env: %s'%str(self.table))

	def execute(self):
		if not Configure.autoconfig:
			return execute_method(self)

		env = ConfigSet.ConfigSet()
		do_config = False
		try:
			env.load(os.path.join(Context.top_dir, Options.lockfile))
		except Exception:
			Logs.warn('Configuring the project')
			do_config = True
		else:
			if env.run_dir != Context.run_dir:
				do_config = True
			else:
				h = 0
				for f in env['files']:
					h = Utils.h_list((h, Utils.readf(f, 'rb')))
				do_config = h != env.hash

		if do_config:
			Options.commands.insert(0, self.cmd)
			Options.commands.insert(0, 'configure')
			if Configure.autoconfig == 'clobber':
				Options.options.__dict__ = env.options
			return

		return execute_method(self)

def start(cwd, version, wafdir):
	# simple example, the file main.c is hard-coded
	try:
		os.stat(cwd + os.sep + 'cbit')
	except:
		print('call from a folder containing a file named "cbit"')
		sys.exit(1)

	Logs.init_log()
	Context.waf_dir = wafdir
	Context.top_dir = Context.run_dir = cwd
	Context.out_dir = os.path.join(cwd, 'build')
	Context.g_module = imp.new_module('wscript')
	Context.g_module.root_path = os.path.join(cwd, 'cbit')
	Context.Context.recurse = recurse_rep

	# this is a fake module, which looks like a standard wscript file
	Context.g_module.options = options
	Context.g_module.configure = configure
	Context.g_module.build = build

	Options.OptionsContext().execute()

	do_config = 'configure' in sys.argv
	try:
		os.stat(cwd + os.sep + 'build')
	except:
		do_config = True
	if do_config:
		Context.create_context('configure').execute()

	if 'clean' in sys.argv:
		Context.create_context('clean').execute()
	if 'build' in sys.argv:
		Context.create_context('build').execute()

	def cmd_and_log(self, cmd, **kw):
		"""
		execute a command, return the stdout
		this method should be used whenever possible for proper logging

		to obtain stdout+stderr, pass output=BOTH in the arguments (or output=0)
		to obtain just stderr, pass output=STDERR in the arguments (or output=-1)

		@param cmd: args for subprocess.Popen
		@param kw: keyword arguments for subprocess.Popen
		"""
		subprocess = Utils.subprocess
		kw['shell'] = isinstance(cmd, str)
		Logs.debug('runner: %r' % cmd)

		if 'quiet' in kw:
			quiet = kw['quiet']
			del kw['quiet']
		else:
			quiet = None

		if 'output' in kw:
			to_ret = kw['output']
			del kw['output']
		else:
			to_ret = STDOUT

		kw['stdout'] = kw['stderr'] = subprocess.PIPE
		if not quiet:
			self.to_log(cmd)
		try:
			p = subprocess.Popen(cmd, **kw)
			(out, err) = p.communicate()
		except Exception as e:
			try:
				self.to_log(str(err))
			except:
				pass
			raise Errors.WafError('Execution failure', ex=e)

		if not isinstance(out, str):
			out = out.decode('utf-8')
		if not isinstance(err, str):
			err = err.decode('utf-8')

		if out and quiet != STDOUT and quiet != BOTH:
			self.to_log('out: %s' % out)
		if err and quiet != STDERR and quiet != BOTH:
			self.to_log('err: %s' % err)

		if p.returncode:
			e = Errors.WafError('command %r returned %r' % (cmd, p.returncode))
			e.returncode = p.returncode
			raise e

		if to_ret == BOTH:
			return (out, err)
		elif to_ret == STDERR:
			return err
		return out

def configure(conf):
    areCustomCxxflagsPresent = (len(conf.env.CXXFLAGS) > 0)
    defaultFlags = []

    defaultFlags += ['-pedantic', '-Wall', '-Wno-long-long']

    if conf.options.debug:
        conf.define('_DEBUG', 1)
        defaultFlags += ['-O0',
                         '-Og', # gcc >= 4.8
                         '-g3',
                         '-fcolor-diagnostics', # clang
                         '-fdiagnostics-color', # gcc >= 4.9
                         '-Werror'
                        ]
        if areCustomCxxflagsPresent:
            missingFlags = [x for x in defaultFlags if x not in conf.env.CXXFLAGS]
            if len(missingFlags) > 0:
                Logs.warn("Selected debug mode, but CXXFLAGS is set to a custom value '%s'"
                          % " ".join(conf.env.CXXFLAGS))
                Logs.warn("Default flags '%s' are not activated" % " ".join(missingFlags))
        else:
            conf.add_supported_cxxflags(defaultFlags)
    else:
        defaultFlags += ['-O2', '-g']
        if not areCustomCxxflagsPresent:
            conf.add_supported_cxxflags(defaultFlags)