SConstruct

#SConstruct
# vim: set fenc=utf-8 sw=4 ts=4 :

# needed imports
from collections import (defaultdict, Counter as collections_counter)
import binascii
import errno
import itertools
import subprocess
import sys
import os
import SCons.Util

# Disable injecting tools into default namespace
SCons.Defaults.DefaultEnvironment(tools = [])

try:
	# Test whether the old Python 2 names exist.
	# If the names are found, use the old Python 2 names, which return
	# views on the data.  If the names are not found, an exception is
	# raised.
	get_dictionary_key_view = dict.iterkeys
	get_dictionary_item_view = dict.iteritems
	get_dictionary_value_view = dict.itervalues
except AttributeError:
	# Name not found.  Use the new Python 3 names, which return views
	# (at least until the Python maintainers decide to redefine the
	# interface again).
	get_dictionary_key_view = dict.keys
	get_dictionary_item_view = dict.items
	get_dictionary_value_view = dict.values

def message(program,msg):
	print("%s: %s" % (program.program_message_prefix, msg))

def get_Werror_string(l):
	if l and '-Werror' in l:
		return '-W'
	return '-Werror='

class StaticSubprocess:
	# This class contains utility functions for calling subprocesses
	# that are expected to return the same output for every call.  The
	# output is cached after the first call, so that callers can request
	# the output again later without causing the program to be run again.
	#
	# Suitable programs are not required to depend solely on the
	# parameters, but are assumed to depend only on state that is
	# unlikely to change in the brief time that SConstruct runs.  For
	# example, a tool might be upgraded by the system administrator,
	# changing its version string.  However, we assume nobody upgrades
	# their tools in the middle of an SConstruct run.  Results are not
	# cached to persistent storage, so an upgrade performed after one
	# SConstruct run, but before the next, will not cause any
	# inconsistencies.
	from shlex import split as shlex_split
	class CachedCall:
		def __init__(self,out,err,returncode):
			self.out = out
			self.err = err
			self.returncode = returncode
	# @staticmethod delayed so that default arguments pick up the
	# undecorated form.
	def pcall(args,stderr=None,_call_cache={},_CachedCall=CachedCall):
		# Use repr since callers may construct the same argument
		# list independently.
		## >>> a = ['git', '--version']
		## >>> b = ['git', '--version']
		## >>> a is b
		## False
		## >>> id(a) == id(b)
		## False
		## >>> a == b
		## True
		## >>> repr(a) == repr(b)
		## True
		a = repr(args)
		c = _call_cache.get(a)
		if c is not None:
			return c
		p = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=stderr)
		(o, e) = p.communicate()
		_call_cache[a] = c = _CachedCall(o, e, p.wait())
		return c
	def qcall(args,stderr=None,_pcall=pcall,_shlex_split=shlex_split):
		return _pcall(_shlex_split(args),stderr)
	@staticmethod
	def get_version_head(cmd,_pcall=pcall,_shlex_split=shlex_split):
		# If cmd is bytes, then it is output from a program and should
		# not be reparsed.
		v = _pcall(([cmd] if isinstance(cmd, bytes) else _shlex_split(cmd)) + ['--version'], stderr=subprocess.PIPE)
		try:
			return v.__version_head
		except AttributeError:
			v.__version_head = r = (v.out or v.err).splitlines()[0] if not v.returncode and (v.out or v.err) else None
			return r
	pcall = staticmethod(pcall)
	qcall = staticmethod(qcall)
	shlex_split = staticmethod(shlex_split)

class ToolchainInformation(StaticSubprocess):
	@staticmethod
	def get_tool_path(env,tool,_qcall=StaticSubprocess.qcall):
		# Include $LINKFLAGS since -fuse-ld=gold influences the path
		# printed for the linker.
		tool = env.subst('$CXX $CXXFLAGS $LINKFLAGS -print-prog-name=%s' % tool)
		return tool, _qcall(tool).out.strip()
	@staticmethod
	def show_partial_environ(env, user_settings, f):
		for v in (
			'CXX',
			'CPPDEFINES',
			'CPPPATH',
			'CPPFLAGS',
			'CXXFLAGS',
			'LIBS',
			'LINKFLAGS',
		) + (
			(
				'RC',
				'RCFLAGS',
			) if user_settings.host_platform == 'win32' else ()
		):
			f("%s: %r" % (v, env.get(v, None)))
		penv = env['ENV']
		for v in (
			'CCACHE_PREFIX',
			'DISTCC_HOSTS',
		):
			f("$%s: %r" % (v, penv.get(v, None)))

class Git(StaticSubprocess):
	class ComputedExtraVersion(object):
		__slots__ = ('describe', 'status', 'diffstat_HEAD', 'revparse_HEAD')
		def __init__(self,describe,status,diffstat_HEAD,revparse_HEAD):
			self.describe = describe
			self.status = status
			self.diffstat_HEAD = diffstat_HEAD
			self.revparse_HEAD = revparse_HEAD
		def __repr__(self):
			return 'ComputedExtraVersion(%r,%r,%r,%r)' % (self.describe, self.status, self.diffstat_HEAD, self.revparse_HEAD)
	UnknownExtraVersion = ComputedExtraVersion('', None, None, None)
	# None when unset.  Instance of ComputedExtraVersion once cached.
	__computed_extra_version = None
	__path_git = None
	# `__pcall_missing_git`, `__pcall_found_git`, and `pcall` must have
	# compatible signatures.  In any given run, there will be at most
	# one call to `pcall`, which then patches itself out of the call
	# chain.  A run will call either __pcall_missing_git or
	# __pcall_found_git (depending on whether $GIT is blank), but never
	# both in the same run.
	@classmethod
	def __pcall_missing_git(cls,args,stderr=None,_missing_git=StaticSubprocess.CachedCall(None, None, 1)):
		return _missing_git
	@classmethod
	def __pcall_found_git(cls,args,stderr=None,_pcall=StaticSubprocess.pcall):
		return _pcall(cls.__path_git + args, stderr=stderr)
	@classmethod
	def pcall(cls,args,stderr=None):
		git = cls.__path_git
		if git is None:
			cls.__path_git = git = cls.shlex_split(os.environ.get('GIT', 'git'))
		cls.pcall = f = cls.__pcall_found_git if git else cls.__pcall_missing_git
		return f(args, stderr)
	def spcall(cls,args,stderr=None):
		g = cls.pcall(args, stderr)
		if g.returncode:
			return None
		return g.out
	@classmethod
	def compute_extra_version(cls,_spcall=spcall):
		c = cls.__computed_extra_version
		if c is None:
			v = cls.__compute_extra_version()
			cls.__computed_extra_version = c = cls.ComputedExtraVersion(
				v,
				_spcall(cls, ['status', '--short', '--branch']),
				_spcall(cls, ['diff', '--stat', 'HEAD']),
				_spcall(cls, ['rev-parse', 'HEAD']).rstrip(),
			) if v is not None else cls.UnknownExtraVersion
		return c
	# Run `git describe --tags --abbrev=12`.
	# On failure, return None.
	# On success, return a string containing:
	#	first line of output of describe
	#	'*' if there are unstaged changes else ''
	#	'+' if there are staged changes else ''
	@classmethod
	def __compute_extra_version(cls):
		try:
			g = cls.pcall(['describe', '--tags', '--abbrev=12'], stderr=subprocess.PIPE)
		except OSError as e:
			if e.errno == errno.ENOENT:
				return None
			raise
		if g.returncode:
			return None
		_pcall = cls.pcall
		return (g.out.splitlines()[0] +	\
			(b'*' if _pcall(['diff', '--quiet']).returncode else b'') +	\
			(b'+' if _pcall(['diff', '--quiet', '--cached']).returncode else b'')
		).decode()

class _ConfigureTests:
	class Collector(object):
		class RecordedTest(object):
			__slots__ = ('desc', 'name', 'predicate')
			def __init__(self,name,desc,predicate=None):
				self.name = name
				self.desc = desc
				self.predicate = predicate
			def __repr__(self):
				return '_ConfigureTests.Collector.RecordedTest(%r, %r, %r)' % (self.name, self.desc, self.predicate)

		def __init__(self,record):
			self.record = record
		def __call__(self,f):
			desc = None
			doc = getattr(f, '__doc__', None)
			if doc is not None:
				doc = doc.rstrip().splitlines()
				if doc and doc[-1].startswith("help:"):
					desc = doc[-1][5:]
			self.record(self.RecordedTest(f.__name__, desc))
			return f

class ConfigureTests(_ConfigureTests):
	class Collector(_ConfigureTests.Collector):
		def __init__(self):
			self.tests = tests = []
			_ConfigureTests.Collector.__init__(self, tests.append)

	class GuardedCollector(_ConfigureTests.Collector):
		__RecordedTest = _ConfigureTests.Collector.RecordedTest
		def __init__(self,collector,guard):
			_ConfigureTests.Collector.__init__(self, collector.record)
			self.__guard = guard
		def RecordedTest(self,name,desc):
			return self.__RecordedTest(name, desc, self.__guard)

	class Cxx11RequiredFeature(object):
		__slots__ = ('main', 'name', 'text')
		def __init__(self,name,text,main=''):
			self.name = name
			name = {'N' : 'test_' + ''.join([c if c.isalnum() else '_' for c in name])}
			self.text = text % name
			self.main = ('{' + (main % name) + '}\n') if main else ''
	class CxxRequiredFeatures(object):
		__slots__ = ('features', 'main', 'text')
		def __init__(self,features):
			self.features = features
			self.main = ''.join([f.main for f in features])
			self.text = ''.join([f.text for f in features])
	class PCHAction:
		def __init__(self,context):
			self._context = context
		def __call__(self,text,ext):
			# Ignore caller-supplied text, since _Test always includes a
			# definition of main().  Using the caller-supplied text
			# would provide one main() in the PCH and another in the
			# test which includes the PCH.
			env = self._context.env
			s = env['OBJSUFFIX']
			env['OBJSUFFIX'] = '.h.gch'
			result = self._context.TryCompile('''
/* Define this here.  Use it in the file which includes the PCH.  If the
 * compiler skips including the PCH, and does not fail for that reason
 * alone, then it will fail when the symbol is used in the later test,
 * since the only definition comes from the PCH.
 */
#define dxx_compiler_supports_pch
			''', ext)
			env['OBJSUFFIX'] = s
			return result
	class PreservedEnvironment:
		# One empty list for all the defaults.  The comprehension
		# creates copies, so it is safe for the default value to be
		# shared.
		def __init__(self,env,keyviews,_l=[]):
			self.flags = {k: env.get(k, _l)[:] for k in itertools.chain.from_iterable(keyviews)}
		def restore(self,env):
			env.Replace(**self.flags)
		def __getitem__(self,name):
			return self.flags.__getitem__(name)
	class ForceVerboseLog(PreservedEnvironment):
		def __init__(self,env):
			# Force verbose output to sconf.log
			self.flags = {}
			for k in (
				'CXXCOMSTR',
				'LINKCOMSTR',
			):
				try:
					# env is like a dict, but does not have .pop(), so
					# emulate it with a lookup + delete.
					self.flags[k] = env[k]
					del env[k]
				except KeyError:
					pass
	class pkgconfig:
		def _get_pkg_config_exec_path(context,msgprefix,pkgconfig):
			Display = context.Display
			if not pkgconfig:
				Display("%s: pkg-config disabled by user settings\n" % msgprefix)
				return pkgconfig
			if os.sep in pkgconfig:
				# Split early, so that the user can pass a command with
				# arguments.  Convert to tuple so that the value is not
				# modified later.
				pkgconfig = tuple(StaticSubprocess.shlex_split(pkgconfig))
				Display("%s: using pkg-config at user specified path %s\n" % (msgprefix, pkgconfig))
				return pkgconfig
			join = os.path.join
			# No path specified, search in $PATH
			for p in os.environ.get('PATH', '').split(os.pathsep):
				fp = join(p, pkgconfig)
				try:
					os.close(os.open(fp, os.O_RDONLY))
				except OSError as e:
					# Ignore on permission errors.  If pkg-config is
					# runnable but not readable, the user must
					# specify its path.
					if e.errno == errno.ENOENT or e.errno == errno.EACCES:
						continue
					raise
				Display("%s: using pkg-config at discovered path %s\n" % (msgprefix, fp))
				return (fp,)
			Display("%s: no usable pkg-config %r found in $PATH\n" % (msgprefix, pkgconfig))
		def __get_pkg_config_path(context,message,user_settings,display_name,
				_get_pkg_config_exec_path=_get_pkg_config_exec_path,
				_cache={}):
			pkgconfig = user_settings.PKG_CONFIG
			if pkgconfig is None:
				CHOST = user_settings.CHOST
				pkgconfig = ('%s-pkg-config' % CHOST) if CHOST else 'pkg-config'
				if sys.platform == 'win32':
					pkgconfig += '.exe'
			path = _cache.get(pkgconfig, _cache)
			if path is _cache:
				_cache[pkgconfig] = path = _get_pkg_config_exec_path(context, message, pkgconfig)
			return path
		@staticmethod
		def merge(context,message,user_settings,pkgconfig_name,display_name,
				guess_flags,
				__get_pkg_config_path=__get_pkg_config_path,
				_cache={}):
			Display = context.Display
			Display("%s: checking %s pkg-config %s\n" % (message, display_name, pkgconfig_name))
			pkgconfig = __get_pkg_config_path(context, message, user_settings, display_name)
			if not pkgconfig:
				Display("%s: skipping %s pkg-config; using default flags %r\n" % (message, display_name, guess_flags))
				return guess_flags
			cmd = pkgconfig + ('--cflags', '--libs', pkgconfig_name)
			flags = _cache.get(cmd, None)
			if flags is not None:
				Display("%s: reusing %s settings from %s: %r\n" % (message, display_name, cmd, flags))
				return flags
			mv_cmd = pkgconfig + ('--modversion', pkgconfig_name)
			try:
				Display("%s: reading %s version from %s\n" % (message, pkgconfig_name, mv_cmd))
				v = StaticSubprocess.pcall(mv_cmd)
				if v.out:
					Display("%s: %s version: %r\n" % (message, display_name, v.out.splitlines()[0]))
			except OSError as o:
				Display("%s: failed with error %s; using default flags for '%s': %r\n" % (message, repr(o.message) if o.errno is None else ('%u ("%s")' % (o.errno, o.strerror)), pkgconfig_name, guess_flags))
				flags = guess_flags
			else:
				Display("%s: reading %s settings from %s\n" % (message, display_name, cmd))
				try:
					flags = {
						k:v for k,v in get_dictionary_item_view(context.env.ParseFlags(' ' + StaticSubprocess.pcall(cmd).out.decode()))
							if v and (k[0] in 'CL')
					}
					Display("%s: %s settings: %r\n" % (message, display_name, flags))
				except OSError as o:
					Display("%s: failed with error %s; using default flags for '%s': %r\n" % (message, repr(o.message) if o.errno is None else ('%u ("%s")' % (o.errno, o.strerror)), pkgconfig_name, guess_flags))
					flags = guess_flags
			_cache[cmd] = flags
			return flags

	# Force test to report failure
	sconf_force_failure = 'force-failure'
	# Force test to report success, and modify flags like it
	# succeeded
	sconf_force_success = 'force-success'
	# Force test to report success, do not modify flags
	sconf_assume_success = 'assume-success'
	expect_sconf_success = 'success'
	expect_sconf_failure = 'failure'
	_implicit_test = Collector()
	_custom_test = Collector()
	_guarded_test_windows = GuardedCollector(_custom_test, lambda user_settings: user_settings.host_platform == 'win32')
	implicit_tests = _implicit_test.tests
	custom_tests = _custom_test.tests
	comment_not_supported = '/* not supported */'
	__python_import_struct = None
	_cxx_conformance_cxx14 = 14
	__cxx_conformance = None
	__cxx11_required_features = CxxRequiredFeatures([
		Cxx11RequiredFeature('constexpr', '''
struct %(N)s {};
static constexpr %(N)s get_%(N)s(){return {};}
''', '''
	get_%(N)s();
'''),
		Cxx11RequiredFeature('extern constexpr', '''
	/* <gcc-4.9 rejects this */
extern const int %(N)s;
constexpr int %(N)s = 0;
'''),
		Cxx11RequiredFeature('nullptr', '''
#include <cstddef>
std::nullptr_t %(N)s1 = nullptr;
int *%(N)s2 = nullptr;
''', '''
	%(N)s2 = %(N)s1;
'''),
		Cxx11RequiredFeature('explicit operator bool', '''
struct %(N)s {
	explicit operator bool();
};
'''),
		Cxx11RequiredFeature('template aliases', '''
using %(N)s_typedef = int;
template <typename>
struct %(N)s_struct;
template <typename T>
using %(N)s_alias = %(N)s_struct<T>;
''', '''
	%(N)s_struct<int> *a = nullptr;
	%(N)s_alias<int> *b = a;
	%(N)s_typedef *c = nullptr;
	(void)b;
	(void)c;
'''),
		Cxx11RequiredFeature('trailing function return type', '''
auto %(N)s()->int;
'''),
		Cxx11RequiredFeature('class scope static constexpr assignment', '''
struct %(N)s_instance {
};
struct %(N)s_container {
	static constexpr %(N)s_instance a = {};
};
'''),
		Cxx11RequiredFeature('braced base class initialization', '''
struct %(N)s_base {
	int a;
};
struct %(N)s_derived : %(N)s_base {
	%(N)s_derived(int e) : %(N)s_base{e} {}
};
'''),
		Cxx11RequiredFeature('std::array', '''
#include "compiler-array.h"
''', '''
	array<int,2>b;
	b[0]=1;
'''
),
		Cxx11RequiredFeature('std::begin(), std::end()', '''
#include <array>
''', '''
	char ac[1];
	std::array<char, 1> as;
%s
''' % (''.join(['''
	auto %(i)s = std::%(f)s(%(a)s);
	(void)%(i)s;
''' % {'i' : 'i%s%s' % (f, a), 'f' : f, 'a' : a} for f in ('begin', 'end') for a in ('ac', 'as')]
	)
	)),
		Cxx11RequiredFeature('range-based for', '''
#include "compiler-range_for.h"
''', '''
	int b[2];
	range_for(int&c,b)c=0;
'''
),
		Cxx11RequiredFeature('<type_traits>', '''
#include <type_traits>
''', '''
	typename std::conditional<sizeof(argc) == sizeof(int),int,long>::type a = 0;
	typename std::conditional<sizeof(argc) != sizeof(int),int,long>::type b = 0;
	(void)a;
	(void)b;
'''
),
		Cxx11RequiredFeature('std::unordered_map::emplace', '''
#include <unordered_map>
''', '''
	std::unordered_map<int,int> m;
	m.emplace(0, 0);
'''
),
		Cxx11RequiredFeature('reference qualified methods', '''
struct %(N)s {
	int a()const &{return 1;}
	int a()const &&{return 2;}
};
''', '''
	%(N)s a;
	auto b = a.a() != %(N)s().a();
	(void)b;
'''
),
])
	def __init__(self,msgprefix,user_settings,platform_settings):
		self.msgprefix = msgprefix
		self.user_settings = user_settings
		self.platform_settings = platform_settings
		self.successful_flags = defaultdict(list)
		self._sconf_results = []
		self.__tool_versions = []
		self.__defined_macros = ''
		# Some tests check the functionality of the compiler's
		# optimizer.
		#
		# When LTO is used, the optimizer is deferred to link time.
		# Force all tests to be Link tests when LTO is enabled.
		self.Compile = self.Link if user_settings.lto else self._Compile
		self.custom_tests = [t for t in self.custom_tests if t.predicate is None or t.predicate(user_settings)]
	def _quote_macro_value(v):
		return v.strip().replace('\n', ' \\\n')
	def _check_sconf_forced(self,calling_function):
		return self._check_forced(calling_function), self._check_expected(calling_function)
	@staticmethod
	def _find_calling_sconf_function():
		try:
			1//0
		except ZeroDivisionError:
			frame = sys.exc_info()[2].tb_frame.f_back.f_back
			while frame is not None:
				co_name = frame.f_code.co_name
				if co_name[:6] == 'check_':
					return co_name[6:]
				frame = frame.f_back
		# This assertion is hit if a test is asked to deduce its caller
		# (calling_function=None), but no function in the call stack appears to
		# be a checking function.
		assert False, "SConf caller not specified and no acceptable caller in stack."
	def _check_forced(self,name):
		# This getattr will raise AttributeError if called for a function which
		# is not a registered test.  Tests must be registered as an implicit
		# test (in implicit_tests, usually by applying the @_implicit_test
		# decorator) or a custom test (in custom_tests, usually by applying the
		# @_custom_test decorator).
		#
		# Unregistered tests are never documented and cannot be overridden by
		# the user.
		return getattr(self.user_settings, 'sconf_%s' % name)
	def _check_expected(self,name):
		# The remarks for _check_forced apply here too.
		r = getattr(self.user_settings, 'expect_sconf_%s' % name)
		if r is not None:
			if r == self.expect_sconf_success:
				return 1
			if r == self.expect_sconf_failure:
				return 0
		return r
	def _check_macro(self,context,macro_name,macro_value,test,_comment_not_supported=comment_not_supported,**kwargs):
		r = self.Compile(context, text="""
#define {macro_name} {macro_value}
{test}
""".format(macro_name=macro_name, macro_value=macro_value, test=test), **kwargs)
		if not r:
			macro_value = _comment_not_supported
		self._define_macro(context, macro_name, macro_value)
	def _define_macro(self,context,macro_name,macro_value):
		context.sconf.Define(macro_name, macro_value)
		self.__defined_macros += '#define %s %s\n' % (macro_name, macro_value)
	implicit_tests.append(_implicit_test.RecordedTest('check_ccache_distcc_ld_works', "assume ccache, distcc, C++ compiler, and C++ linker work"))
	implicit_tests.append(_implicit_test.RecordedTest('check_ccache_ld_works', "assume ccache, C++ compiler, and C++ linker work"))
	implicit_tests.append(_implicit_test.RecordedTest('check_distcc_ld_works', "assume distcc, C++ compiler, and C++ linker work"))
	implicit_tests.append(_implicit_test.RecordedTest('check_ld_works', "assume C++ compiler and linker work"))
	implicit_tests.append(_implicit_test.RecordedTest('check_ld_blank_libs_works', "assume C++ compiler and linker work with empty $LIBS"))
	implicit_tests.append(_implicit_test.RecordedTest('check_ld_blank_libs_ldflags_works', "assume C++ compiler and linker work with empty $LIBS and empty $LDFLAGS"))
	implicit_tests.append(_implicit_test.RecordedTest('check_cxx_blank_cxxflags_works', "assume C++ compiler works with empty $CXXFLAGS"))
	# This must be the first custom test.  This test verifies the compiler
	# works and disables any use of ccache/distcc for the duration of the
	# configure run.
	#
	# SCons caches configuration results and tests are usually very small, so
	# ccache will provide limited benefit.
	#
	# Some tests are expected to raise a compiler error.  If distcc is used
	# and DISTCC_FALLBACK prevents local retries, then distcc interprets a
	# compiler error as an indication that the volunteer which served that
	# compile is broken and should be blacklisted.  Suppress use of distcc for
	# all tests to avoid spurious blacklist entries.
	#
	# During the main build, compiling remotely can allow more jobs to run in
	# parallel.  Tests are serialized by SCons, so distcc is helpful during
	# testing only if compiling remotely is faster than compiling locally.
	# This may be true for embedded systems that distcc to desktops, but will
	# not be true for desktops or laptops that distcc to similar sized
	# machines.
	@_custom_test
	def check_cxx_works(self,context):
		"""
help:assume C++ compiler works
"""
		# Use %r to print the tuple in an unambiguous form.
		context.Log('scons: dxx: version: %r\n' % (Git.compute_extra_version(),))
		cenv = context.env
		penv = cenv['ENV']
		self.__cxx_com_prefix = cenv['CXXCOM']
		# Require ccache to run the next stage, but allow it to write the
		# result to cache.  This lets the test validate that ccache fails for
		# an unusable CCACHE_DIR and also validate that the next stage handles
		# the input correctly.  Without this, a cached result may hide that
		# the next stage compiler (or wrapper) worked when a prior run
		# performed the test, but is now broken.
		CCACHE_RECACHE = penv.get('CCACHE_RECACHE', None)
		penv['CCACHE_RECACHE'] = '1'
		most_recent_error = self._check_cxx_works(context)
		if most_recent_error is not None:
			raise SCons.Errors.StopError(most_recent_error)
		if CCACHE_RECACHE is None:
			del penv['CCACHE_RECACHE']
		else:
			penv['CCACHE_RECACHE'] = CCACHE_RECACHE
		# If ccache/distcc are in use, disable them during testing.
		# This assignment is also done in _check_cxx_works, but only on an
		# error path.  Repeat it here so that it is effective on the success
		# path.  It cannot be moved above the call to _check_cxx_works because
		# some tests in _check_cxx_works rely on its original value.
		cenv['CXXCOM'] = cenv._dxx_cxxcom_no_prefix
		self._check_cxx_conformance_level(context)
	def _show_tool_version(self,context,tool,desc,save_tool_version=True):
		# These version results are not used for anything, but are
		# collected here so that users who post only a build log will
		# still supply at least some useful information.
		#
		# This is split into two lines so that the first line is printed
		# before the function call required to format the string for the
		# second line.
		Display = context.Display
		Display('%s: checking version of %s %r ... ' % (self.msgprefix, desc, tool))
		try:
			v = StaticSubprocess.get_version_head(tool)
		except OSError as e:
			if e.errno == errno.ENOENT or e.errno == errno.EACCES:
				Display('error: %s\n' % e.strerror)
				raise SCons.Errors.StopError('Failed to run %r.' % tool)
			raise
		if save_tool_version:
			self.__tool_versions.append((tool, v))
		Display('%r\n' % v)
	def _show_indirect_tool_version(self,context,CXX,tool,desc):
		Display = context.Display
		Display('%s: checking path to %s ... ' % (self.msgprefix, desc))
		tool, name = ToolchainInformation.get_tool_path(context.env, tool)
		self.__tool_versions.append((tool, name))
		if not name:
			# Strange, but not fatal for this to fail.
			Display('! %r\n' % name)
			return
		Display('%r\n' % name)
		self._show_tool_version(context,name,desc)
	def _check_cxx_works(self,context,_crc32=binascii.crc32):
		# Test whether the compiler+linker+optional wrapper(s) work.  If
		# anything fails, a StopError is guaranteed on return.  However, to
		# help the user, this function pushes through all the combinations and
		# reports the StopError for the least complicated issue.  If both the
		# compiler and the linker fail, the compiler will be reported, since
		# the linker might work once the compiler is fixed.
		#
		# If a test fails, then the pending StopError allows this function to
		# safely modify the construction environment and process environment
		# without reverting its changes.
		most_recent_error = None
		Link = self.Link
		cenv = context.env
		user_settings = self.user_settings
		use_distcc = user_settings.distcc
		use_ccache = user_settings.ccache
		if user_settings.show_tool_version:
			CXX = cenv['CXX']
			self._show_tool_version(context, CXX, 'C++ compiler')
			if user_settings.show_assembler_version:
				self._show_indirect_tool_version(context, CXX, 'as', 'assembler')
			if user_settings.show_linker_version:
				self._show_indirect_tool_version(context, CXX, 'ld', 'linker')
			if use_distcc:
				self._show_tool_version(context, use_distcc, 'distcc', False)
			if use_ccache:
				self._show_tool_version(context, use_ccache, 'ccache', False)
		# Use C++ single line comment so that it is guaranteed to extend
		# to the end of the line.  repr ensures that embedded newlines
		# will be escaped and that the final character will not be a
		# backslash.
		self.__commented_tool_versions = s = ''.join('// %r => %r\n' % (v[0], v[1]) for v in self.__tool_versions)
		self.__tool_versions = '''
/* This test is always false.  Use a non-trivial condition to
 * discourage external text scanners from recognizing that the block
 * is never compiled.
 */
#if 1 < -1
%.8x
%s
#endif
''' % (_crc32(s.encode()), s)
		ToolchainInformation.show_partial_environ(cenv, user_settings, lambda s, _Display=context.Display, _msgprefix=self.msgprefix: _Display("%s:\t%s\n" % (_msgprefix, s)))
		if use_ccache:
			if use_distcc:
				if Link(context, text='', msg='whether ccache, distcc, C++ compiler, and linker work', calling_function='ccache_distcc_ld_works'):
					return
				most_recent_error = 'ccache and C++ linker work, but distcc does not work.'
				# Disable distcc so that the next call to self.Link tests only
				# ccache+linker.
				del cenv['ENV']['CCACHE_PREFIX']
			if Link(context, text='', msg='whether ccache, C++ compiler, and linker work', calling_function='ccache_ld_works'):
				return most_recent_error
			most_recent_error = 'C++ linker works, but ccache does not work.'
		elif use_distcc:
			if Link(context, text='', msg='whether distcc, C++ compiler, and linker work', calling_function='distcc_ld_works'):
				return
			most_recent_error = 'C++ linker works, but distcc does not work.'
		else:
			# This assertion fails if the environment's $CXXCOM was modified
			# to use a prefix, but both user_settings.ccache and
			# user_settings.distcc evaluate to false.
			assert cenv._dxx_cxxcom_no_prefix is cenv['CXXCOM'], "Unexpected prefix in $CXXCOM."
		# If ccache/distcc are in use, then testing with one or both of them
		# failed.  Disable them so that the next test can check whether the
		# local linker works.
		#
		# If they are not in use, this assignment is a no-op.
		cenv['CXXCOM'] = cenv._dxx_cxxcom_no_prefix
		if Link(context, text='', msg='whether C++ compiler and linker work', calling_function='ld_works'):
			# If ccache or distcc are in use, this block is only reached
			# when one or both of them failed.  `most_recent_error` will
			# be a description of the failure.  If neither are in use,
			# `most_recent_error` will be None.
			return most_recent_error
		# Force only compile, even if LTO is enabled.
		elif self._Compile(context, text='', msg='whether C++ compiler works', calling_function='cxx_works'):
			specified_LIBS = 'or ' if cenv.get('LIBS') else ''
			if specified_LIBS:
				cenv['LIBS'] = []
				if Link(context, text='', msg='whether C++ compiler and linker work with blank $LIBS', calling_function='ld_blank_libs_works'):
					# Using $LIBS="" allowed the test to succeed.  $LIBS
					# specifies one or more unusable libraries.  Usually
					# this is because it specifies a library which does
					# not exist or is an incompatible architecture.
					return 'C++ compiler works.  C++ linker works with blank $LIBS.  C++ linker does not work with specified $LIBS.'
			if cenv['LINKFLAGS']:
				cenv['LINKFLAGS'] = []
				if Link(context, text='', msg='whether C++ compiler and linker work with blank $LIBS and blank $LDFLAGS', calling_function='ld_blank_libs_ldflags_works'):
					# Using LINKFLAGS="" allowed the test to succeed.
					# To avoid bloat, there is no further test to see
					# whether the link will work with user-specified
					# LIBS after LINKFLAGS is cleared.  The user must
					# fix at least one problem anyway.  If the user is
					# unlucky, fixing LINKFLAGS will result in a
					# different error on the next run.  If the user is
					# lucky, fixing LINKFLAGS will allow the build to
					# run.
					return 'C++ compiler works.  C++ linker works with blank $LIBS and blank $LDFLAGS.  C++ linker does not work with blank $LIBS and specified $LDFLAGS.'
			return 'C++ compiler works.  C++ linker does not work with specified %(LIBS)sblank $LIBS and specified $LINKFLAGS.  C++ linker does not work with blank $LIBS and blank $LINKFLAGS.' % {
				'LIBS' : specified_LIBS,
			}
		else:
			if cenv['CXXFLAGS']:
				cenv['CXXFLAGS'] = []
				if self._Compile(context, text='', msg='whether C++ compiler works with blank $CXXFLAGS', calling_function='cxx_blank_cxxflags_works'):
					return 'C++ compiler works with blank $CXXFLAGS.  C++ compiler does not work with specified $CXXFLAGS.'
			return 'C++ compiler does not work.'
	implicit_tests.append(_implicit_test.RecordedTest('check_cxx11', "assume C++ compiler supports C++11"))
	implicit_tests.append(_implicit_test.RecordedTest('check_cxx14', "assume C++ compiler supports C++14"))
	__cxx_conformance_CXXFLAGS = [None]
	def _check_cxx_conformance_level(self,context,_levels=(
			# List standards in descending order of preference.
			#
			# Currently, no C++17 features are both useful and easy to
			# emulate in supported older compilers, so C++17 is not
			# requested.
			#
			# C++14 is required, so list it last.
			_cxx_conformance_cxx14,
		), _CXXFLAGS=__cxx_conformance_CXXFLAGS,
		_successflags={'CXXFLAGS' : __cxx_conformance_CXXFLAGS}
		):
		# Testing the compiler option parser only needs Compile, even when LTO
		# is enabled.
		Compile = self._Compile
		# Accepted options by version:
		#
		#	gcc-4.9 -std=gnu++1y
		#	gcc-4.9 -std=gnu++14
		#
		#	gcc-5 -std=gnu++1y
		#	gcc-5 -std=gnu++14
		#	gcc-5 -std=gnu++1z
		#	gcc-5 -std=gnu++17
		#
		#	gcc-6 -std=gnu++1y
		#	gcc-6 -std=gnu++14
		#	gcc-6 -std=gnu++1z
		#	gcc-6 -std=gnu++17
		#
		#	gcc-7 -std=gnu++1y
		#	gcc-7 -std=gnu++14
		#	gcc-7 -std=gnu++1z
		#	gcc-7 -std=gnu++17
		#
		#	gcc-8 -std=gnu++1y
		#	gcc-8 -std=gnu++14
		#	gcc-8 -std=gnu++1z
		#	gcc-8 -std=gnu++17
		#	gcc-8 -std=gnu++2a
		for level in _levels:
			opt = '-std=gnu++%u' % level
			_CXXFLAGS[0] = opt
			if Compile(context, text='', msg='whether C++ compiler accepts {opt}'.format(opt=opt), successflags=_successflags, calling_function='cxx%s' % level):
				self.__cxx_conformance = level
				return
		raise SCons.Errors.StopError('C++ compiler does not accept any supported C++ -std option.')
	def _Test(self,context,text,msg,action,main='',ext='.cpp',testflags={},successflags={},skipped=None,successmsg=None,failuremsg=None,expect_failure=False,calling_function=None,__flags_Werror = {'CXXFLAGS' : ['-Werror']}):
		if calling_function is None:
			calling_function = self._find_calling_sconf_function()
		context.Message('%s: checking %s...' % (self.msgprefix, msg))
		if skipped is not None:
			context.Result('(skipped){skipped}'.format(skipped=skipped))
			if self.user_settings.record_sconf_results:
				self._sconf_results.append((calling_function, 'skipped'))
			return
		env_flags = self.PreservedEnvironment(context.env, (get_dictionary_key_view(successflags), get_dictionary_key_view(testflags), get_dictionary_key_view(__flags_Werror), ('CPPDEFINES',)))
		context.env.MergeFlags(successflags)
		forced, expected = self._check_sconf_forced(calling_function)
		caller_modified_env_flags = self.PreservedEnvironment(context.env, (get_dictionary_key_view(testflags), get_dictionary_key_view(__flags_Werror)))
		# Always pass -Werror to configure tests.
		context.env.Append(**__flags_Werror)
		context.env.Append(**testflags)
		# If forced is None, run the test.  Otherwise, skip the test and
		# take an action determined by the value of forced.
		if forced is None:
			r = action('''
{tools}
{macros}
{text}

{undef_SDL_main}

{main}
'''.format(
	tools=self.__tool_versions,
	macros=self.__defined_macros,
	text=text,
	undef_SDL_main='' if self.user_settings.sdl2 else '#undef main	/* avoid -Dmain=SDL_main from libSDL */',
	main=('' if main is None else
'''
int main(int argc,char**argv){(void)argc;(void)argv;
%s

;}
''' % main
	)), ext)
			# Some tests check that the compiler rejects an input.
			# SConf considers the result a failure when the compiler
			# rejects the input.  For tests that consider a rejection to
			# be the good result, this conditional flips the sense of
			# the result so that a compiler rejection is reported as
			# success.
			if expect_failure:
				r = not r
			context.Result((successmsg if r else failuremsg) or r)
			if expected is not None and r != expected:
				raise SCons.Errors.StopError('Expected and actual results differ.  Test should %s, but it did not.' % ('succeed' if expected else 'fail'))
		else:
			choices = (self.sconf_force_failure, self.sconf_force_success, self.sconf_assume_success)
			if forced not in choices:
				try:
					forced = choices[int(forced)]
				except ValueError:
					raise SCons.Errors.UserError("Unknown force value for sconf_%s: %s" % (co_name[6:], forced))
				except IndexError:
					raise SCons.Errors.UserError("Out of range force value for sconf_%s: %s" % (co_name[6:], forced))
			if forced == self.sconf_force_failure:
				# Pretend the test returned a failure result
				r = False
			elif forced == self.sconf_force_success or forced == self.sconf_assume_success:
				# Pretend the test succeeded.  Forced success modifies
				# the environment as if the test had run and succeeded.
				# Assumed success modifies the environment as if the
				# test had run and failed.
				#
				# The latter is used when the user arranges for the
				# environment to be correct.  For example, if the
				# compiler understands C++14, but uses a non-standard
				# name for the option, the user would set assume-success
				# and add the appropriate option to CXXFLAGS.
				r = True
			else:
				raise SCons.Errors.UserError("Unknown force value for sconf_%s: %s" % (co_name[6:], forced))
			# Flip the sense of the forced value, so that users can
			# treat "force-failure" as force-bad-result regardless of
			# whether the bad result is that the compiler rejected good
			# input or that the compiler accepted bad input.
			if expect_failure:
				r = not r
			context.Result('(forced){inverted}{forced}'.format(forced=forced, inverted='(inverted)' if expect_failure else ''))
		# On success, revert to base flags + successflags
		# On failure, revert to base flags
		if r and forced != self.sconf_assume_success:
			caller_modified_env_flags.restore(context.env)
			context.env.Replace(CPPDEFINES=env_flags['CPPDEFINES'])
			f = self.successful_flags
			# Move most CPPDEFINES to the generated header, so that
			# command lines are shorter.
			for k, v in get_dictionary_item_view(successflags):
				if k == 'CPPDEFINES':
					continue
				f[k].extend(v)
			d = successflags.get('CPPDEFINES', None)
			if d:
				append_CPPDEFINE = f['CPPDEFINES'].append
				Define = context.sconf.Define
				for v in d:
					# v is 'NAME' for -DNAME
					# v is ('NAME', 'VALUE') for -DNAME=VALUE
					d = (v, None) if isinstance(v, str) else v
					if d[0] in ('_REENTRANT',):
						# Blacklist defines that must not be moved to the
						# configuration header.
						append_CPPDEFINE(v)
						continue
					Define(d[0], d[1])
		else:
			env_flags.restore(context.env)
		self._sconf_results.append((calling_function, r))
		return r
	def _Compile(self,context,_Test=_Test,**kwargs):
		return _Test(self, context,action=context.TryCompile, **kwargs)
	def Link(self,context,_Test=_Test,**kwargs):
		return _Test(self, context,action=context.TryLink, **kwargs)
	# Compile and link a program that uses a system library.  On
	# success, return None.  On failure, return a tuple indicating which
	# stage failed and providing a text error message to show to the
	# user.  Some callers handle failure by retrying with other options.
	# Others abort the SConf run.
	def _soft_check_system_library(self,context,header,main,lib,pretext='',text='',successflags={},testflags={}):
		include = pretext + '\n'.join(['#include <%s>' % h for h in header])
		header = header[-1]
		# Test library.  On success, good.  On failure, test header to
		# give the user more help.
		if self.Link(context, text=include + text, main=main, msg='for usable library %s' % lib, successflags=successflags, testflags=testflags):
			return
		# If linking failed, an error report is inevitable.  Probe
		# progressively simpler configurations to help the user trace
		# the problem.
		successflags = successflags.copy()
		successflags.update(testflags)
		Compile = self.Compile
		if Compile(context, text=include + text, main=main, msg='for usable header %s' % header, testflags=successflags):
			# If this Compile succeeds, then the test program can be
			# compiled, but it cannot be linked.  The required library
			# may be missing or broken.
			return (0, "Header %s is usable, but library %s is not usable." % (header, lib))
		if Compile(context, text=include, main=main and '', msg='whether compiler can parse header %s' % header, testflags=successflags):
			# If this Compile succeeds, then the test program cannot be
			# compiled, but the header can be used with an empty test
			# program.  Either the test program is broken or it relies
			# on the header working differently than the used header
			# actually works.
			return (1, "Header %s is parseable, but cannot compile the test program." % header)
		CXXFLAGS = successflags.setdefault('CXXFLAGS', [])
		CXXFLAGS.append('-E')
		if Compile(context, text=include, main=main and '', msg='whether preprocessor can parse header %s' % header, testflags=successflags):
			# If this Compile succeeds, then the used header can be
			# preprocessed, but cannot be compiled as C++ even with an
			# empty test program.  The header likely has a C++ syntax
			# error or assumes prerequisite headers will be included by
			# the calling program.
			return (2, "Header %s exists, but cannot compile an empty program." % header)
		CXXFLAGS.extend(('-M', '-MG'))
		# If the header exists and is accepted by the preprocessor, an
		# earlier test would have returned and this Compile would not be
		# reached.  Therefore, this Compile runs only if the header:
		# - Is directly missing
		# - Is indirectly missing (present, but includes a missing
		#   header)
		# - Is present, but rejected by the preprocessor (such as from
		#   an active `#error`)
		if Compile(context, text=include, main=main and '', msg='whether preprocessor can locate header %s (and supporting headers)' % header, expect_failure=True, testflags=successflags):
			# If this Compile succeeds, then the header does not exist,
			# or exists and includes (possibly through layers of
			# indirection) a header which does not exist.  Passing `-MG`
			# makes non-existent headers legal, but still rejects
			# headers with `#error` and similar constructs.
			#
			# `expect_failure=True` inverts it to a failure in the
			# logged output and in the Python value returned from
			# `Compile(...)`.
			# - Compile success means that the header was not found,
			#   which is not an error when `-MG` is passed, but was an
			#   error in earlier tests.
			# - Compile failure means that the header was found, but
			#   unusable, which is an error even when `-MG` is passed.
			#   This can happen if the header contains `#error`
			#   directives that are not preprocessed out.
			# Therefore, use `expect_failure=True` so that "success"
			# (header not found) prints "no" ("cannot locate header")
			# and "failure" (header found, but unusable) prints "yes"
			# ("can locate header").  This keeps the confusing double
			# negatives confined to the code and this comment.  User
			# visible log messages are clear.
			#
			# Compile failure (unusable) is converted to a True return
			# by `expect_failure=True`, so the guarded path should
			# return "unusable" and the fallthrough path should return
			# "missing".
			return (3, "Header %s is unusable." % header)
		return (4, "Header %s is missing or includes a missing supporting header." % header)
	# Compile and link a program that uses a system library.  On
	# success, return None.  On failure, abort the SConf run.
	def _check_system_library(self,*args,**kwargs):
		e = self._soft_check_system_library(*args, **kwargs)
		if e:
			raise SCons.Errors.StopError(e[1])
	# User settings tests are hidden because they do not respect sconf_*
	# overrides, so the user should not be offered an override.
	@_custom_test
	def _check_user_settings_endian(self,context,__endian_names=('little', 'big')):
		cls = self.__class__
		endian = self.user_settings.host_endian
		if endian is None:
			struct = cls.__python_import_struct
			if struct is None:
				import struct
				cls.__python_import_struct = struct
			a = struct.pack('cccc', b'1', b'2', b'3', b'4')
			unpack = struct.unpack
			i = unpack('i', a)
			if i == unpack('<i', a):
				endian = 0
			elif i == unpack('>i', a):
				endian = 1
			else:
				raise SCons.Errors.UserError("Unknown host endian: unpack('i', %r) == %r; set host_endian='big' or host_endian='little' as appropriate." % (a, i))
		else:
			if endian == __endian_names[0]:
				endian = 0
			else:
				endian = 1
		context.Result('%s: checking endian to use...%s' % (self.msgprefix, __endian_names[endian]))
		self._define_macro(context, 'DXX_WORDS_BIGENDIAN', endian)

	@_custom_test
	def _check_user_settings_words_need_alignment(self,context):
		self._result_check_user_setting(context, self.user_settings.words_need_alignment, 'DXX_WORDS_NEED_ALIGNMENT', 'word alignment fixups')

	@_custom_test
	def _check_user_settings_opengl(self,context):
		user_settings = self.user_settings
		Result = context.Result
		_define_macro = self._define_macro
		_define_macro(context, 'DXX_USE_OGL', int(user_settings.opengl))
		_define_macro(context, 'DXX_USE_OGLES', int(user_settings.opengles))
		if user_settings.opengles:
			s = 'OpenGL ES'
		elif user_settings.opengl:
			s = 'OpenGL'
		else:
			s = 'software renderer'
		Result('%s: building with %s' % (self.msgprefix, s))

	def _result_check_user_setting(self,context,condition,CPPDEFINES,label,int=int,str=str):
		if isinstance(CPPDEFINES, str):
			self._define_macro(context, CPPDEFINES, int(condition))
		elif condition:
			self.successful_flags['CPPDEFINES'].extend(CPPDEFINES)
		context.Result('%s: checking whether to enable %s...%s' % (self.msgprefix, label, 'yes' if condition else 'no'))

	@_custom_test
	def _check_user_settings_debug(self,context,_CPPDEFINES=(('NDEBUG',), ('RELEASE',))):
		self._result_check_user_setting(context, not self.user_settings.debug, _CPPDEFINES, 'release options')

	@_custom_test
	def _check_user_settings_memdebug(self,context,_CPPDEFINES=(('DEBUG_MEMORY_ALLOCATIONS',),)):
		self._result_check_user_setting(context, self.user_settings.memdebug, _CPPDEFINES, 'memory allocation tracking')

	@_custom_test
	def _check_user_settings_editor(self,context,_CPPDEFINES='DXX_USE_EDITOR'):
		self._result_check_user_setting(context, self.user_settings.editor, _CPPDEFINES, 'level editor')

	@_custom_test
	def _check_user_settings_ipv6(self,context,_CPPDEFINES='DXX_USE_IPv6'):
		self._result_check_user_setting(context, self.user_settings.ipv6, _CPPDEFINES, 'IPv6 support')

	@_custom_test
	def _check_user_settings_udp(self,context,_CPPDEFINES='DXX_USE_UDP'):
		self._result_check_user_setting(context, self.user_settings.use_udp, _CPPDEFINES, 'multiplayer over UDP')

	@_custom_test
	def _check_user_settings_tracker(self,context,_CPPDEFINES='DXX_USE_TRACKER'):
		use_tracker = self.user_settings.use_tracker
		self._result_check_user_setting(context, use_tracker, _CPPDEFINES, 'UDP game tracker')
		# The legacy UDP tracker does not need either curl or jsoncpp.
		# The new HTTP tracker requires both.  Force `use_tracker` to
		# False for now.  Remove this comment and this assignment when
		# the HTTP tracker is made active.
		use_tracker = False
		if use_tracker:
			self.check_curl(context)
			self.check_jsoncpp(context)

	@_implicit_test
	def check_libpng(self,context,
		_header=(
			'cstdint',
			'png.h',
		),
		_guess_flags={'LIBS' : ['png']},
		_text='''
namespace {
struct d_screenshot
{
	png_struct *png_ptr;
	png_info *info_ptr = nullptr;
	static void png_error_cb(png_struct *, const char *) {}
	static void png_warn_cb(png_struct *, const char *) {}
	static void png_write_cb(png_struct *, uint8_t *, png_size_t) {}
	static void png_flush_cb(png_struct *) {}
};
}
''',
		_main='''
	d_screenshot ss;
	ss.png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, &ss, &d_screenshot::png_error_cb, &d_screenshot::png_warn_cb);
	png_set_write_fn(ss.png_ptr, &ss, &d_screenshot::png_write_cb, &d_screenshot::png_flush_cb);
	ss.info_ptr = png_create_info_struct(ss.png_ptr);
#ifdef PNG_tIME_SUPPORTED
	png_time pt;
	pt.year = 2018;
	pt.month = 1;
	pt.day = 1;
	pt.hour = 1;
	pt.minute = 1;
	pt.second = 1;
	png_set_tIME(ss.png_ptr, ss.info_ptr, &pt);
#endif
#if DXX_USE_OGL
	const auto color_type = PNG_COLOR_TYPE_RGB;
#else
	png_set_PLTE(ss.png_ptr, ss.info_ptr, reinterpret_cast<const png_color *>(&ss), 256 * 3);
	const auto color_type = PNG_COLOR_TYPE_PALETTE;
#endif
	png_set_IHDR(ss.png_ptr, ss.info_ptr, 1, 1, 8, color_type, PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
#ifdef PNG_TEXT_SUPPORTED
	png_text text_fields[1] = {};
	png_set_text(ss.png_ptr, ss.info_ptr, text_fields, 1);
#endif
	png_write_info(ss.png_ptr, ss.info_ptr);
	png_byte *row_pointers[1024]{};
	png_write_rows(ss.png_ptr, row_pointers, 1024);
	png_write_end(ss.png_ptr, ss.info_ptr);
	png_destroy_write_struct(&ss.png_ptr, &ss.info_ptr);
'''):
		successflags = self.pkgconfig.merge(context, self.msgprefix, self.user_settings, 'libpng', 'libpng', _guess_flags)
		return self._soft_check_system_library(context, header=_header, main=_main, lib='png', text=_text, successflags=successflags)

	@_custom_test
	def _check_user_settings_adldmidi(self,context):
		user_settings = self.user_settings
		adlmidi = user_settings.adlmidi
		if adlmidi == 'none':
			adlmidi_load_type = 'disabled'
		elif adlmidi == 'runtime':
			adlmidi_load_type = 'load dynamically'
		else:
			return
		context.Result('%s: checking how to handle ADL MIDI...%s' % (self.msgprefix, adlmidi_load_type))
		Define = context.sconf.Define
		Define('DXX_USE_ADLMIDI', int(user_settings._enable_adlmidi()))

	@_custom_test
	def _check_user_settings_screenshot(self,context):
		user_settings = self.user_settings
		screenshot_mode = user_settings.screenshot
		if screenshot_mode == 'png':
			screenshot_format_type = screenshot_mode
		elif screenshot_mode == 'legacy':
			screenshot_format_type = 'tga' if user_settings.opengl else 'pcx'
		elif screenshot_mode == 'none':
			screenshot_format_type = 'screenshot support disabled'
		else:
			return
		context.Result('%s: checking how to format screenshots...%s' % (self.msgprefix, screenshot_format_type))
		Define = context.sconf.Define
		Define('DXX_USE_SCREENSHOT_FORMAT_PNG', int(screenshot_mode == 'png'))
		Define('DXX_USE_SCREENSHOT_FORMAT_LEGACY', int(screenshot_mode == 'legacy'))
		Define('DXX_USE_SCREENSHOT', int(screenshot_mode != 'none'))
		if screenshot_mode == 'png':
			e = self.check_libpng(context)
			if e:
				raise SCons.Errors.StopError(e[1] + '  Set screenshot=legacy to remove screenshot libpng requirement or set screenshot=none to remove screenshot support.')

	# Require _WIN32_WINNT >= 0x0501 to enable getaddrinfo
	# Require _WIN32_WINNT >= 0x0600 to enable some useful AI_* flags
	@_guarded_test_windows
	def _check_user_CPPDEFINES__WIN32_WINNT(self,context,_msg='%s: checking whether to define _WIN32_WINNT...%s',_CPPDEFINES_WIN32_WINNT=('_WIN32_WINNT', 0x600)):
		env = context.env
		for f in env['CPPDEFINES']:
			# Ignore the case that an element is a string with this
			# value, since that would not define the macro to a
			# useful value.  In CPPDEFINES, only a tuple of
			# (name,number) is useful for macro _WIN32_WINNT.
			if f[0] == '_WIN32_WINNT':
				f = f[1]
				context.Result(_msg % (self.msgprefix, 'no, already set in CPPDEFINES as %s' % (('%#x' if isinstance(f, int) else '%r') % f)))
				return
		for f in env['CPPFLAGS']:
			if f.startswith('-D_WIN32_WINNT='):
				context.Result(_msg % (self.msgprefix, 'no, already set in CPPFLAGS as %r' % f))
				return
		context.Result(_msg % (self.msgprefix, 'yes, define _WIN32_WINNT=%#x' % _CPPDEFINES_WIN32_WINNT[1]))
		self.successful_flags['CPPDEFINES'].append(_CPPDEFINES_WIN32_WINNT)
		self.__defined_macros += '#define %s %s\n' % (_CPPDEFINES_WIN32_WINNT[0], _CPPDEFINES_WIN32_WINNT[1])
	@_implicit_test
	def check_curl(self,context,
		_header=('curl/curl.h',),
		_guess_flags={'LIBS' : ['curl']},
		_main='''
	CURL *c = curl_easy_init();
	curl_easy_setopt(c, CURLOPT_WRITEFUNCTION, nullptr);
	curl_easy_cleanup(c);
'''):
		successflags = self.pkgconfig.merge(context, self.msgprefix, self.user_settings, 'libcurl', 'curl', _guess_flags).copy()
		successflags['CPPDEFINES'] = successflags.get('CPPDEFINES', []) + ['DXX_HAVE_LIBCURL']
		self._check_system_library(context, header=_header, main=_main, lib='curl', successflags=successflags)
	@_implicit_test
	def check_jsoncpp(self,context,
		_header=(
			'memory',
			'json/json.h',
		),
		_guess_flags={'LIBS' : ['jsoncpp'], 'CPPPATH': ['/usr/include/jsoncpp']},
		_main='''
	Json::Value v;
	v["a"] = "a";
	v["b"] = 1;
	// This code is silly, but it uses many of the required
	// symbols, so if it builds, jsoncpp is probably installed correctly.
	const std::string &&s = Json::writeString(Json::StreamWriterBuilder(), v);
	std::string errs;
	std::unique_ptr<Json::CharReader>(
		Json::CharReaderBuilder().newCharReader()
	)->parse(s.data(), &s.data()[s.size()], &v, &errs);
'''):
		successflags = self.pkgconfig.merge(context, self.msgprefix, self.user_settings, 'jsoncpp', 'jsoncpp', _guess_flags)
		self._check_system_library(context, header=_header, main=_main, lib='jsoncpp', successflags=successflags)
	@_guarded_test_windows
	def check_dbghelp_header(self,context,_CPPDEFINES='DXX_ENABLE_WINDOWS_MINIDUMP'):
		windows_minidump = self.user_settings.windows_minidump
		self._result_check_user_setting(context, windows_minidump, _CPPDEFINES, 'minidump on exception')
		if not windows_minidump:
			return
		include_dbghelp_header = '''
// <dbghelp.h> assumes that <windows.h> was included earlier and fails
// to parse if this assumption is false
#include <windows.h>
#include <dbghelp.h>
'''
		if self.Compile(context, text=include_dbghelp_header + '''
#include <stdexcept>

using MiniDumpWriteDump_type = decltype(MiniDumpWriteDump);
MiniDumpWriteDump_type *pMiniDumpWriteDump;

[[noreturn]]
static void terminate_handler()
{
	MINIDUMP_EXCEPTION_INFORMATION mei;
	MINIDUMP_USER_STREAM musa[1];
	MINIDUMP_USER_STREAM_INFORMATION musi;
	EXCEPTION_POINTERS ep;
	mei.ExceptionPointers = &ep;
	musi.UserStreamCount = 1;
	musi.UserStreamArray = musa;
	(*pMiniDumpWriteDump)(GetCurrentProcess(), GetCurrentProcessId(), GetCurrentProcess(), MiniDumpWithFullMemory, &mei, &musi, nullptr);
	ExitProcess(0);
}
''', main='''
	std::set_terminate(&terminate_handler);
''', msg='for usable header dbghelp.h'):
			return
		errtext = "Header dbghelp.h is parseable but cannot compile the test program."	\
			if self.Compile(context, text=include_dbghelp_header, msg='for parseable header dbghelp.h')	\
			else "Header dbghelp.h is missing or unusable."
		raise SCons.Errors.StopError(errtext + "  Upgrade the Windows API header package or disable minidump support.")
	@_custom_test
	def check_libphysfs(self,context,_header=('physfs.h',)):
		main = '''
	PHYSFS_File *f;
	char b[1] = {0};
	if (!PHYSFS_init(""))
		return 1;
	f = PHYSFS_openWrite("a");
	PHYSFS_sint64 w = PHYSFS_write(f, b, 1, 1);
	(void)w;
	PHYSFS_close(f);
	f = PHYSFS_openRead("a");
	PHYSFS_sint64 r = PHYSFS_read(f, b, 1, 1);
	(void)r;
	PHYSFS_close(f);
'''
		l = ['physfs']
		successflags = {'LIBS' : l}
		e = self._soft_check_system_library(context, header=_header, main=main, lib='physfs', successflags=successflags)
		if not e:
			return
		if e[0] == 0:
			context.Display("%s: physfs header usable; adding zlib and retesting library\n" % self.msgprefix)
			l.append('z')
			e = self._soft_check_system_library(context, header=_header, main=main, lib='physfs', successflags=successflags)
		if e:
			raise SCons.Errors.StopError(e[1])
	@_custom_test
	def _check_SDL(self,context):
		if self.user_settings.sdl2:
			check_libSDL = self.check_libSDL2
			check_SDL_mixer = self.check_SDL2_mixer
		else:
			check_libSDL = self.check_libSDL
			check_SDL_mixer = self.check_SDL_mixer
		check_libSDL(context)
		check_SDL_mixer(context)
	@_implicit_test
	def check_libSDL(self,context,_guess_flags={
			'LIBS' : ['SDL'] if sys.platform != 'darwin' else [],
		}):
		self._check_libSDL(context, '', _guess_flags)
	@_implicit_test
	def check_libSDL2(self,context,_guess_flags={
			'LIBS' : ['SDL2'] if sys.platform != 'darwin' else [],
		}):
		if not self.user_settings.opengl:
			raise SCons.Errors.StopError('Rebirth does not support SDL2 without OpenGL.  Set opengl=1 or sdl2=0.')
		self._check_libSDL(context, '2', _guess_flags)
	def _check_libSDL(self,context,sdl2,guess_flags):
		user_settings = self.user_settings
		successflags = self.pkgconfig.merge(context, self.msgprefix, user_settings, 'sdl%s' % sdl2, 'SDL%s' % sdl2, guess_flags).copy()
		if user_settings.max_joysticks:
			# If joysticks are enabled, but all possible inputs are
			# disabled, then disable joystick support.
			if not (user_settings.max_axes_per_joystick or user_settings.max_buttons_per_joystick or user_settings.max_hats_per_joystick):
				user_settings.max_joysticks = 0
			elif not user_settings.max_buttons_per_joystick:
				user_settings.max_hats_per_joystick = 0
		else:
			# If joysticks are disabled, then disable all possible
			# inputs.
			user_settings.max_axes_per_joystick = user_settings.max_buttons_per_joystick = user_settings.max_hats_per_joystick = 0
		successflags['CPPDEFINES'] = CPPDEFINES = successflags.get('CPPDEFINES', [])[:]
		CPPDEFINES.extend((
			('DXX_MAX_JOYSTICKS', user_settings.max_joysticks),
			('DXX_MAX_AXES_PER_JOYSTICK', user_settings.max_axes_per_joystick),
			('DXX_MAX_BUTTONS_PER_JOYSTICK', user_settings.max_buttons_per_joystick),
			('DXX_MAX_HATS_PER_JOYSTICK', user_settings.max_hats_per_joystick),
			('DXX_USE_SDL_REDBOOK_AUDIO', int(not sdl2)),
		))
		context.Display('%s: checking whether to enable joystick support...%s\n' % (self.msgprefix, 'yes' if user_settings.max_joysticks else 'no'))
		# SDL2 removed CD-rom support.
		init_cdrom = '0' if sdl2 else 'SDL_INIT_CDROM'
		error_text_opengl_mismatch = 'Rebirth configured with OpenGL enabled, but SDL{0} configured with OpenGL disabled.  Disable Rebirth OpenGL or install an SDL{0} with OpenGL enabled.'.format(sdl2)
		test_opengl = ('''
#ifndef SDL_VIDEO_OPENGL
#error "%s"
#endif
''' % error_text_opengl_mismatch) if user_settings.opengl else ''
		main = '''
	SDL_RWops *ops = reinterpret_cast<SDL_RWops *>(argv);
#if DXX_MAX_JOYSTICKS
#ifdef SDL_JOYSTICK_DISABLED
#error "Rebirth configured with joystick support enabled, but SDL{sdl2} configured with joystick support disabled.  Disable Rebirth joystick support or install an SDL{sdl2} with joystick support enabled."
#endif
#define DXX_SDL_INIT_JOYSTICK	SDL_INIT_JOYSTICK |
#else
#define DXX_SDL_INIT_JOYSTICK
#endif
	SDL_Init(DXX_SDL_INIT_JOYSTICK {init_cdrom} | SDL_INIT_VIDEO | SDL_INIT_AUDIO);
{test_opengl}
#if DXX_MAX_JOYSTICKS
	auto n = SDL_NumJoysticks();
	(void)n;
#endif
	SDL_QuitSubSystem(SDL_INIT_VIDEO);
	SDL_FreeRW(ops);
	SDL_Quit();
'''
		e = self._soft_check_system_library(context,header=['SDL.h'],main=main.format(init_cdrom=init_cdrom, sdl2=sdl2, test_opengl=test_opengl),
			lib=('SDL{0} with OpenGL' if test_opengl else 'SDL{0}').format(sdl2), successflags=successflags
		)
		if not e:
			return
		if test_opengl:
			e2 = self._soft_check_system_library(context,header=['SDL.h'],main=main.format(init_cdrom=init_cdrom, sdl2=sdl2, test_opengl=''),
				lib='SDL without OpenGL', successflags=successflags
			)
			if not e2 and e[0] == 1:
				e = (None, error_text_opengl_mismatch)
		raise SCons.Errors.StopError(e[1])
	# SDL_mixer/SDL2_mixer use the same -I line as SDL/SDL2
	@_implicit_test
	def check_SDL_mixer(self,context,_guess_flags={
			'LIBS' : ['SDL_mixer'] if sys.platform != 'darwin' else [],
		}):
		self._check_SDL_mixer(context, '', _guess_flags)
	@_implicit_test
	def check_SDL2_mixer(self,context,_guess_flags={
			'LIBS' : ['SDL2_mixer'] if sys.platform != 'darwin' else [],
		}):
		self._check_SDL_mixer(context, '2', _guess_flags)
	def _check_SDL_mixer(self,context,sdl2,guess_flags):
		mixer = 'SDL%s_mixer' % sdl2
		user_settings = self.user_settings
		context.Display('%s: checking whether to use %s...%s\n' % (self.msgprefix, mixer, 'yes' if user_settings.sdlmixer else 'no'))
		# SDL_mixer support?
		use_sdlmixer = user_settings.sdlmixer
		self._define_macro(context, 'DXX_USE_SDLMIXER', int(use_sdlmixer))
		if not use_sdlmixer:
			return
		successflags = self.pkgconfig.merge(context, self.msgprefix, user_settings, mixer, mixer, guess_flags)
		if user_settings.host_platform == 'darwin':
			successflags = successflags.copy()
			successflags['FRAMEWORKS'] = [mixer]
			relative_headers = 'Library/Frameworks/%s.framework/Headers' % mixer
			successflags['CPPPATH'] = [os.path.join(os.getenv("HOME"), relative_headers), '/%s' % relative_headers]
		self._check_system_library(context,header=['SDL_mixer.h'],main='''
	int i = Mix_Init(MIX_INIT_FLAC | MIX_INIT_OGG);
	(void)i;
	Mix_Pause(0);
	Mix_ResumeMusic();
	Mix_Quit();
''',
			lib=mixer, successflags=successflags)

	@_custom_test
	def check_compiler_missing_field_initializers(self,context,
		_testflags_warn={'CXXFLAGS' : ['-Wmissing-field-initializers']},
		_successflags_nowarn={'CXXFLAGS' : ['-Wno-missing-field-initializers']}
	):
		"""
Test whether the compiler warns for a statement of the form

	variable={};

gcc-4.x warns for this form, but -Wno-missing-field-initializers silences it.
gcc-5 does not warn.

This form is used extensively in the code as a shorthand for resetting
variables to their default-constructed value.
"""
		text = 'struct A{int a;};'
		main = 'A a{};(void)a;'
		Compile = self.Compile
		if Compile(context, text=text, main=main, msg='whether C++ compiler accepts {} initialization', testflags=_testflags_warn) or \
			Compile(context, text=text, main=main, msg='whether C++ compiler understands -Wno-missing-field-initializers', successflags=_successflags_nowarn) or \
			not Compile(context, text=text, main=main, msg='whether C++ compiler always errors for {} initialization', expect_failure=True):
			return
		raise SCons.Errors.StopError("C++ compiler errors on {} initialization, even with -Wno-missing-field-initializers.")

	@_custom_test
	def check_compiler_extended_identifiers(self,context,main=r'''
#define DXX_RENAME_IDENTIFIER2(I,N)	I##$##N
#define DXX_RENAME_IDENTIFIER(I,N)	DXX_RENAME_IDENTIFIER2(I,N)
#define DXX_extended a\u012b\u012f\u013d
#define var	DXX_RENAME_IDENTIFIER(var, DXX_extended)
	int var;
	(void)var;
#undef var
#undef DXX_extended
#undef DXX_RENAME_IDENTIFIER
#undef DXX_RENAME_IDENTIFIER2
''',_successflags={'CXXFLAGS' : ['-fextended-identifiers']}):
		Compile = self.Compile
		if Compile(context, text='', main=main, msg='whether compiler accepts extended identifiers by default') or \
			Compile(context, text='', main=main, msg='whether compiler accepts extended identifiers with -fextended-identifiers', successflags=_successflags):
			return
		user_settings = self.user_settings
		user_settings._dxx_extended_identifiers = user_settings._dxx_disable_extended_identifiers
	@_custom_test
	def check_attribute_error(self,context):
		"""
Test whether the compiler accepts and properly implements gcc's function
attribute [__attribute__((__error__))][1].

A proper implementation will compile correctly if the function is
declared and, after optimizations are applied, the function is not
called.  If this function attribute is not supported, then
DXX_ALWAYS_ERROR_FUNCTION results in link-time errors, rather than
compile-time errors.

This test will report failure if the optimizer does not remove the call
to the marked function.

[1]: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-g_t_0040code_007berror_007d-function-attribute-3097

help:assume compiler supports __attribute__((error))
"""
		self._check_function_dce_attribute(context, 'error')
	def _check_function_dce_attribute(self,context,attribute):
		__attribute__ = '__%s__' % attribute
		f = '''
void a()__attribute__((%s("a called")));
''' % __attribute__
		macro_name = '__attribute_%s(M)' % attribute
		Compile = self.Compile
		Define = context.sconf.Define
		if Compile(context, text=f, main='if("0"[0]==\'1\')a();', msg='whether compiler optimizes function __attribute__((%s))' % __attribute__):
			Define('DXX_HAVE_ATTRIBUTE_%s' % attribute.upper())
			macro_value = '__attribute__((%s(M)))' % __attribute__
		else:
			Compile(context, text=f, msg='whether compiler accepts function __attribute__((%s))' % __attribute__) and \
			Compile(context, text=f, main='a();', msg='whether compiler understands function __attribute__((%s))' % __attribute__, expect_failure=True)
			macro_value = self.comment_not_supported
		Define(macro_name, macro_value)
		self.__defined_macros += '#define %s %s\n' % (macro_name, macro_value)

	@_custom_test
	def check_builtin_bswap(self,context,
		_main='''
	(void)__builtin_bswap64(static_cast<uint64_t>(argc));
	(void)__builtin_bswap32(static_cast<uint32_t>(argc));
#ifdef DXX_HAVE_BUILTIN_BSWAP16
/* Added in gcc-4.8 */
	(void)__builtin_bswap16(static_cast<uint16_t>(argc));
#endif
''',
		_successflags_bswap16={'CPPDEFINES' : ['DXX_HAVE_BUILTIN_BSWAP', 'DXX_HAVE_BUILTIN_BSWAP16']},
		_successflags_bswap={'CPPDEFINES' : ['DXX_HAVE_BUILTIN_BSWAP']},
	):
		"""
Test whether the compiler accepts the gcc byte swapping intrinsic
functions.  These functions may be optimized into architecture-specific
swap instructions when the idiomatic swap is not.

	u16 = (u16 << 8) | (u16 >> 8);

The 32-bit version ([__builtin_bswap32][1]) and 64-bit version
([__builtin_bswap64][2]) are present in all supported versions of
gcc.  The 16-bit version ([__builtin_bswap16][3]) was added in
gcc-4.8.

[1]: https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#index-g_t_005f_005fbuiltin_005fbswap32-4135
[2]: https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#index-g_t_005f_005fbuiltin_005fbswap64-4136
[3]: https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#index-g_t_005f_005fbuiltin_005fbswap16-4134
"""
		include = '''
#include <cstdint>
'''
		Compile = self.Compile
		if Compile(context, text=include, main=_main, msg='whether compiler implements __builtin_bswap{16,32,64} functions', successflags=_successflags_bswap16) or \
			Compile(context, text=include, main=_main, msg='whether compiler implements __builtin_bswap{32,64} functions', successflags=_successflags_bswap):
			return
	implicit_tests.append(_implicit_test.RecordedTest('check_optimize_builtin_constant_p', "assume compiler optimizes __builtin_constant_p"))
	@_custom_test
	def check_builtin_constant_p(self,context):
		"""
Test whether the compiler accepts and properly implements gcc's
intrinsic [__builtin_constant_p][1].  A proper implementation will
compile correctly if the intrinsic is recognized and, after
optimizations are applied, the intrinsic returns true for a constant
input and that return value is used to optimize away dead code.
If this intrinsic is not supported, or if applying optimizations
does not make the intrinsic report true, then the test reports
failure.  A failure here disables some compile-time sanity checks.

This test is known to fail when optimizations are disabled.  The failure
is not a bug in the test or in the compiler.

[1]: https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#index-g_t_005f_005fbuiltin_005fconstant_005fp-4082

help:assume compiler supports compile-time __builtin_constant_p
"""
		f = '''
/*
 * Begin `timekeeping.i` from gcc bug #72785, comment #0.  This block
 * provokes gcc-7 into generating a call to ____ilog2_NaN, which then
 * fails to link when ____ilog2_NaN is intentionally undefined.
 *
 * Older versions of gcc declare the expression to be false in
 * this case, and do not generate the call to ____ilog2_NaN.  This looks
 * fragile since b is provably non-zero (`b` = `a` if `a` is not zero,
 * else = `c` = `1`, so `b` is non-zero regardless of the path used in
 * the ternary operator), but the specific non-zero value is not
 * provable.  However, this matches the testcase posted in gcc's
 * Bugzilla and produces the desired results on each of gcc-5 (enable),
 * gcc-6 (enable), and gcc-7 (disable).
 */
int a, b;
int ____ilog2_NaN();
static void by(void) {
	int c = 1;
	b = a ?: c;
	__builtin_constant_p(b) ? b ? ____ilog2_NaN() : 0 : 0;
}
/*
 * End `timekeeping.i`.
 */
int c(int);
static int x(int y){
	return __builtin_constant_p(y) ? 1 : %s;
}
'''
		main = '''
	/*
	** Tell the compiler not to make any assumptions about the value of
	** `a`.  In LTO mode, the compiler would otherwise prove that it
	** knows there are no writes to `a` and therefore prove that `a`
	** must be zero.  That proof then causes it to compile `by()` as:
	**
	**		b = 0 ? 0 : 1;
	**		__builtin_constant_p(1) ? 1 ? ____ilog2_NaN() : 0 : 0;
	**
	** That then generates a reference to the intentionally undefined
	** ____ilog2_NaN, causing the test to report failure.  Prevent this
	** by telling the compiler that it cannot prove the value of `a`,
	** forcing it not to propagate a zero `a` into `by()`.
	**/
	asm("" : "=rm" (a));
	by();
	return x(1) + x(2);
'''
		Define = context.sconf.Define
		if self.Link(context, text=f % 'c(y)', main=main, msg='whether compiler optimizes __builtin_constant_p', calling_function='optimize_builtin_constant_p'):
			Define('DXX_HAVE_BUILTIN_CONSTANT_P')
			Define('DXX_CONSTANT_TRUE(E)', '(__builtin_constant_p((E)) && (E))')
			dxx_builtin_constant_p = '__builtin_constant_p(A)'
		else:
			# This is present because it may be useful to see in the
			# debug log.  It is not expected to modify the build
			# environment.
			self.Compile(context, text=f % '2', main=main, msg='whether compiler accepts __builtin_constant_p')
			dxx_builtin_constant_p = '((void)(A),0)'
		Define('dxx_builtin_constant_p(A)', dxx_builtin_constant_p)

	@_custom_test
	def check_builtin_expect(self,context):
		"""
Test whether the compiler accepts gcc's intrinsic
[__builtin_expect][1].  This intrinsic is a hint to the optimizer,
which it may ignore.  The test does not try to detect whether the
optimizer respects such hints.

When this test succeeds, conditional tests can hint to the optimizer
which path should be considered hot.

[1]: https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#index-g_t_005f_005fbuiltin_005fexpect-4083
"""
		main = '''
return __builtin_expect(argc == 1, 1) ? 1 : 0;
'''
		if self.Compile(context, text='', main=main, msg='whether compiler accepts __builtin_expect'):
			likely = '__builtin_expect(!!(A), 1)'
			unlikely = '__builtin_expect(!!(A), 0)'
		else:
			likely = unlikely = '(!!(A))'
		Define = context.sconf.Define
		Define('likely(A)', likely)
		Define('unlikely(A)', unlikely)

	@_custom_test
	def check_builtin_file(self,context):
		if self.Compile(context, text='''
static void f(const char * = __builtin_FILE(), unsigned = __builtin_LINE())
{
}
''', main='f();', msg='whether compiler accepts __builtin_FILE, __builtin_LINE'):
			context.sconf.Define('DXX_HAVE_CXX_BUILTIN_FILE_LINE')

	@_custom_test
	def check_builtin_object_size(self,context):
		"""
Test whether the compiler accepts and optimizes gcc's intrinsic
[__builtin_object_size][1].  If this intrinsic is optimized,
compile-time checks can verify that the caller-specified constant
size of a variable does not exceed the compiler-determined size of
the variable.  If the compiler cannot determine the size of the
variable, no compile-time check is done.

[1]: https://gcc.gnu.org/onlinedocs/gcc/Object-Size-Checking.html#index-g_t_005f_005fbuiltin_005fobject_005fsize-3657

help:assume compiler supports __builtin_object_size
"""
		f = '''
/* a() is never defined.  An optimizing compiler will eliminate the
 * attempt to call it, allowing the Link to succeed.  A non-optimizing
 * compiler will emit the call, and the Link will fail.
 */
int a();
static inline int a(char *c){
	return __builtin_object_size(c,0) == 4 ? 1 : %s;
}
'''
		main = '''
	char c[4];
	return a(c);
'''
		if self.Link(context, text=f % 'a()', main=main, msg='whether compiler optimizes __builtin_object_size'):
			context.sconf.Define('DXX_HAVE_BUILTIN_OBJECT_SIZE')
		else:
			self.Compile(context, text=f % '2', main=main, msg='whether compiler accepts __builtin_object_size')

	@_custom_test
	def check_embedded_compound_statement(self,context,
		_compound_statement_native=('', ''),
		_compound_statement_emulated=('[&]', '()')
	):
		"""
Test whether the compiler implements gcc's [statement expression][1]
extension.  If this extension is present, statements can be used where
expressions are expected.  If it is absent, it is emulated by defining,
calling, and then discarding a lambda function.  The compiler produces
better error messages for errors in statement expressions than for
errors in lambdas, so prefer statement expressions when they are
available.

[1]: https://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html
"""
		f = '''
	return ({ 1 + 2; });
'''
		t = _compound_statement_native if self.Compile(context, text='', main=f, msg='whether compiler understands embedded compound statements') else _compound_statement_emulated
		Define = context.sconf.Define
		Define('DXX_BEGIN_COMPOUND_STATEMENT', t[0])
		Define('DXX_END_COMPOUND_STATEMENT', t[1])

	@_custom_test
	def check_compiler_always_error_optimizer(self,context,
	# Good case: <gcc-6 takes this path.  Declare a function with
	# __attribute__((__error__)) and call it.
	_macro_value_simple=_quote_macro_value('''( DXX_BEGIN_COMPOUND_STATEMENT {
	void F() __attribute_error(S);
	F();
} DXX_END_COMPOUND_STATEMENT )
'''),
	# Bad case: >=gcc-6 takes this path.  Declare a local scope class
	# with a static method marked __attribute__((__error__)) and call
	# that method.
	_macro_value_complicated=_quote_macro_value('''( DXX_BEGIN_COMPOUND_STATEMENT {
	struct DXX_ALWAYS_ERROR_FUNCTION {
		__attribute_error(S)
		/* The function must be declared inline because it is a member
		** method, but must be marked noinline to discourage gcc from
		** inlining it.  If it is inlined, then the error message is not
		** generated even if F() is called.
		**
		** To make matters worse, if this function calls an undefined
		** global scope function with __attribute__((__error__)), the
		** compiler retains that call even when F() is never called.  That
		** does not produce a compile error, but does cause a link error
		** when the intentionally undefined global function is not found.
		**/
		__attribute__((__noinline__))
		static void F()
		{
			/* If the function body is empty, noinline is not sufficient
			** to prevent the compiler from skipping the error message.
			** Use a no-op asm() with clobber statements to discourage
			** gcc from inlining F().  This is only called if the build
			** is supposed to fail, so the clobber has no performance
			** consequences.
			**/
			__asm__ __volatile__("" ::: "memory", "cc");
		}
	};
	DXX_ALWAYS_ERROR_FUNCTION::F();
} DXX_END_COMPOUND_STATEMENT )
''')
	):
		'''
Rebirth defines a macro DXX_ALWAYS_ERROR_FUNCTION that, when expanded,
results in a call to an undefined function.  If the optimizer cannot
prove the call to be unreachable, the build fails.  This is used to
diagnose certain types of always-incorrect code, such as accessing
elements beyond the end of an array.

Functions declared in local scope make the name available until the end
of the containing block.  The name is treated as if it was declared in
the same scope as the function itself, so a name declared inside a
function in an anonymous namespace is also considered to be in the
anonymous namespace.

Starting in gcc-6, declaring a function while in local scope in an
anonymous namespace triggers a compiler diagnostic about "used but never
defined" even if the optimizer proves the call to be unreachable.
Proving the call to be unreachable would cause the function not to be
used.  Failing to prove it to be unreachable would lead to the
__attribute__((__error__)) marker triggering an error message from the
compiler.  Before gcc-6, the compiler permitted such declarations
provided that the optimizer proved the function was never called.  The
compiler never permitted such declarations when the optimizer failed to
prove the function was never called.

This SConf test checks whether the compiler warns when that construct is
used.  If the compiler does not warn, a simple definition of
DXX_ALWAYS_ERROR_FUNCTION is used.  If the compiler warns, a complicated
and fragile definition of DXX_ALWAYS_ERROR_FUNCTION is used.
As stated in `import this`:

	Simple is better than complex.
	Complex is better than complicated.

Therefore, we prefer the simple form whenever the compiler allows it,
even though the complicated form works for both old and new compilers.
'''
		context.sconf.Define('DXX_ALWAYS_ERROR_FUNCTION(F,S)',
			_macro_value_simple if self.Compile(context, text='''
namespace {
void f()
{
	(void)("i"[0] == 's' &&
		(
			(
				{
					void e() __attribute_error("");
					e();
				}
			), 0
		)
	);
}
}
''', main='f();', msg='whether compiler allows dead calls to undefined functions in the anonymous namespace')	\
			else _macro_value_complicated
		, '''
Declare a function named F and immediately call it.  If gcc's
__attribute__((__error__)) is supported, __attribute_error will expand
to use __attribute__((__error__)) with the explanatory string S, causing
it to be a compilation error if this expression is not optimized out.

Use this macro to implement static assertions that depend on values that
are known to the optimizer, but are not considered "compile time
constant expressions" for the purpose of the static_assert intrinsic.

C++11 deleted functions cannot be used here because the compiler raises
an error for the call before the optimizer has an opportunity to delete
the call via a dead code elimination pass.
''')

	@_custom_test
	def check_attribute_always_inline(self,context):
		"""
help:assume compiler supports __attribute__((always_inline))
"""
		macro_name = '__attribute_always_inline()'
		macro_value = '__attribute__((__always_inline__))'
		self._check_macro(context,macro_name=macro_name,macro_value=macro_value,test='%s static inline void a(){}' % macro_name, main='a();', msg='for function __attribute__((always_inline))')

	@_custom_test
	def check_attribute_alloc_size(self,context):
		"""
help:assume compiler supports __attribute__((alloc_size))
"""
		macro_name = '__attribute_alloc_size(A,...)'
		macro_value = '__attribute__((alloc_size(A, ## __VA_ARGS__)))'
		self._check_macro(context,macro_name=macro_name,macro_value=macro_value,test="""
char*a(int)__attribute_alloc_size(1);
char*b(int,int)__attribute_alloc_size(1,2);
""", msg='for function __attribute__((alloc_size))')
	@_custom_test
	def check_attribute_cold(self,context):
		"""
Test whether the compiler accepts gcc's function attribute
[__attribute__((cold))][1].  Use this to annotate functions which are
rarely called, such as error reporting functions.

[1]: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-g_t_0040code_007bcold_007d-function-attribute-3090

help:assume compiler supports __attribute__((cold))
"""
		macro_name = '__attribute_cold'
		macro_value = '__attribute__((cold))'
		self._check_macro(context,macro_name=macro_name,macro_value=macro_value,test="""
__attribute_cold char*a(int);
""", msg='for function __attribute__((cold))')
	@_custom_test
	def check_attribute_format_arg(self,context):
		"""
help:assume compiler supports __attribute__((format_arg))
"""
		macro_name = '__attribute_format_arg(A)'
		macro_value = '__attribute__((format_arg(A)))'
		self._check_macro(context,macro_name=macro_name,macro_value=macro_value,test="""
char*a(char*)__attribute_format_arg(1);
""", msg='for function __attribute__((format_arg))')
	@_custom_test
	def check_attribute_format_printf(self,context):
		"""
help:assume compiler supports __attribute__((format(printf)))
"""
		macro_name = '__attribute_format_printf(A,B)'
		macro_value = '__attribute__((format(printf,A,B)))'
		self._check_macro(context,macro_name=macro_name,macro_value=macro_value,test="""
int a(char*,...)__attribute_format_printf(1,2);
int b(char*)__attribute_format_printf(1,0);
""", msg='for function __attribute__((format(printf)))')
	@_custom_test
	def check_attribute_malloc(self,context):
		"""
help:assume compiler supports __attribute__((malloc))
"""
		macro_name = '__attribute_malloc()'
		macro_value = '__attribute__((malloc))'
		self._check_macro(context,macro_name=macro_name,macro_value=macro_value,test="""
int *a()__attribute_malloc();
""", msg='for function __attribute__((malloc))')
	@_custom_test
	def check_attribute_nonnull(self,context):
		"""
help:assume compiler supports __attribute__((nonnull))
"""
		macro_name = '__attribute_nonnull(...)'
		macro_value = '__attribute__((nonnull __VA_ARGS__))'
		self._check_macro(context,macro_name=macro_name,macro_value=macro_value,test="""
int a(int*)__attribute_nonnull();
int b(int*)__attribute_nonnull((1));
""", msg='for function __attribute__((nonnull))')
	@_custom_test
	def check_attribute_noreturn(self,context):
		"""
help:assume compiler supports __attribute__((noreturn))
"""
		macro_name = '__attribute_noreturn'
		macro_value = '__attribute__((noreturn))'
		self._check_macro(context,macro_name=macro_name,macro_value=macro_value,test='%s void a();void a(){for(;;);}' % macro_name, main='a();', msg='for function __attribute__((noreturn))')
	@_custom_test
	def check_attribute_used(self,context):
		"""
help:assume compiler supports __attribute__((used))
"""
		macro_name = '__attribute_used'
		macro_value = '__attribute__((used))'
		self._check_macro(context,macro_name=macro_name,macro_value=macro_value,test="""
static void a()__attribute_used;
static void a(){}
""", msg='for function __attribute__((used))')
	@_custom_test
	def check_attribute_unused(self,context):
		"""
help:assume compiler supports __attribute__((unused))
"""
		macro_name = '__attribute_unused'
		macro_value = '__attribute__((unused))'
		self._check_macro(context,macro_name=macro_name,macro_value=macro_value,test="""
__attribute_unused
static void a(){}
""", msg='for function __attribute__((unused))', successflags={'CXXFLAGS' : [get_Werror_string(context.env['CXXFLAGS']) + 'unused']})
	@_custom_test
	def check_attribute_warn_unused_result(self,context):
		"""
help:assume compiler supports __attribute__((warn_unused_result))
"""
		macro_name = '__attribute_warn_unused_result'
		macro_value = '__attribute__((warn_unused_result))'
		self._check_macro(context,macro_name=macro_name,macro_value=macro_value,test="""
int a()__attribute_warn_unused_result;
int a(){return 0;}
""", msg='for function __attribute__((warn_unused_result))')
	@_custom_test
	def check_attribute_warning(self,context,_check_function_dce_attribute=_check_function_dce_attribute):
		_check_function_dce_attribute(self, context, 'warning')
	def Cxx14Compile(self,context,*args,**kwargs):
		"""
Test whether the compiler supports a C++14 feature.  If the compiler
failed the test for C++14 support, then the test is not run, but a
message about skipping the test is printed and the test is assumed to
fail.
"""
		self.__skip_missing_cxx_std(self._cxx_conformance_cxx14, 'no C++14 support', kwargs)
		return self.Compile(context,*args,**kwargs)
	def __skip_missing_cxx_std(self,level,text,kwargs):
		if self.__cxx_conformance < level:
			kwargs.setdefault('skipped', text)

	@_custom_test
	def check_cxx11_static_assert(self,context,_f='''
static_assert(%(expr)s, "global");
struct A
{
	static const bool value = %(expr)s;
	static_assert(%(expr)s, "class literal");
	static_assert(A::value, "class static");
	A()
	{
		static_assert(%(expr)s, "constructor literal");
		static_assert(value, "constructor static");
	}
};
template <typename>
struct B
{
	static const bool value = %(expr)s;
	static_assert(%(expr)s, "template class literal");
	static_assert(value, "template class static");
	B(A a)
	{
		static_assert(%(expr)s, "constructor literal");
		static_assert(value, "constructor self static");
		static_assert(A::value, "constructor static");
		static_assert(a.value, "constructor member");
	}
	template <typename R>
		B(B<R> &&)
		{
			static_assert(%(expr)s, "template constructor literal");
			static_assert(value, "template constructor self static");
			static_assert(B<R>::value, "template constructor static");
		}
};
template <typename T>
static void f(B<T> b)
{
	static_assert(%(expr)s, "template function literal");
	static_assert(B<T>::value, "template function static");
	static_assert(b.value, "template function member");
}
void f(A a);
void f(A a)
{
	static_assert(%(expr)s, "function literal");
	static_assert(A::value, "function static");
	static_assert(a.value, "function member");
	f(B<long>(B<int>(a)));
}
'''
			,_msg='for C++11 intrinsic static_assert when %s',_tdict={'expr' : 'true&&true'},_fdict={'expr' : 'false||false'}):
		"""
help:assume compiler supports C++ intrinsic static_assert
"""
		_Compile = self.Compile
		if not (_Compile(context, text=_f % _tdict, main='f(A());', msg=_msg % 'true') and \
				_Compile(context, text=_f % _fdict, main='f(A());', msg=_msg % 'false', expect_failure=True)):
			raise SCons.Errors.StopError('C++ compiler does not support tested versions of C++11 static_assert.')
	@_custom_test
	def check_namespace_disambiguate(self,context,_successflags={'CPPDEFINES' : ['DXX_HAVE_CXX_DISAMBIGUATE_USING_NAMESPACE']}):
		self.Compile(context, text='''
namespace A
{
	int a;
}
using namespace A;
namespace B
{
	class A;
}
using namespace B;
''', main='return A::a;', msg='whether compiler handles classes from "using namespace"', successflags=_successflags)
	@_custom_test
	def check_cxx11_required_features(self,context,_features=__cxx11_required_features):
		# First test all the features at once.  If all work, then done.
		# If any fail, then the configure run will stop.
		_Compile = self.Compile
		if _Compile(context, text=_features.text, main=_features.main, msg='for required C++11 features'):
			return
		# Some failed.  Run each test separately and report to the user
		# which ones failed.
		failures = [f.name for f in _features.features if not _Compile(context, text=f.text, main=f.main, msg='for C++11 %s' % f.name)]
		raise SCons.Errors.StopError(("C++ compiler does not support %s." %
			', '.join(failures)
		) if failures else 'C++ compiler supports each feature individually, but not all of them together.  Please report this as a bug in the Rebirth configure script.')
	def _show_pch_count_message(self,context,which,user_setting):
		count = user_setting if user_setting else 0
		context.Display('%s: checking when to pre-compile %s headers...%s\n' % (self.msgprefix, which, ('if used at least %u time%s' % (count, 's' if count > 1 else '')) if count > 0 else 'never'))
		return count > 0
	implicit_tests.append(_implicit_test.RecordedTest('check_pch_compile', "assume C++ compiler can create pre-compiled headers"))
	implicit_tests.append(_implicit_test.RecordedTest('check_pch_use', "assume C++ compiler can use pre-compiled headers"))
	@_custom_test
	def _check_pch(self,context,
		_Test=_Test,
		_testflags_compile_pch={'CXXFLAGS' : ['-x', 'c++-header']},
		_testflags_use_pch={'CXXFLAGS' : ['-Winvalid-pch', '-include', None]}
	):
		self.pch_flags = None
		# Always evaluate both
		co = self._show_pch_count_message(context, 'own', self.user_settings.pch)
		cs = self._show_pch_count_message(context, 'system', self.user_settings.syspch)
		context.did_show_result = True
		if not co and not cs:
			return
		context.Display('%s: checking when to compute pre-compiled header input *pch.cpp...%s\n' % (self.msgprefix, 'if missing' if self.user_settings.pch_cpp_assume_unchanged else 'always'))
		result = _Test(self, context, action=self.PCHAction(context), text='', msg='whether compiler can create pre-compiled headers', testflags=_testflags_compile_pch, calling_function='pch_compile')
		if not result:
			raise SCons.Errors.StopError("C++ compiler cannot create pre-compiled headers.")
		_testflags_use_pch = _testflags_use_pch.copy()
		_testflags_use_pch['CXXFLAGS'][-1] = str(context.lastTarget)[:-4]
		result = self.Compile(context, text='''
/* This symbol is defined in the PCH.  If the PCH is included, this
 * symbol will preprocess away to nothing.  If the PCH is not included,
 * then the compiler is not using PCHs as expected.
 */
dxx_compiler_supports_pch
''', msg='whether compiler uses pre-compiled headers', testflags=_testflags_use_pch, calling_function='pch_use')
		if not result:
			raise SCons.Errors.StopError("C++ compiler cannot use pre-compiled headers.")
		self.pch_flags = _testflags_compile_pch
	@_custom_test
	def _check_cxx11_explicit_delete(self,context):
		# clang 3.4 warns when a named parameter to a deleted function
		# is not used, even though there is no body in which it could be
		# used, so every named parameter to a deleted function is always
		# unused.
		f = 'int a(int %s)=delete;'
		if self.check_cxx11_explicit_delete_named(context, f):
			# No bug: named parameters with explicitly deleted functions
			# work correctly.
			return
		if self.check_cxx11_explicit_delete_named_unused(context, f):
			# Clang bug hit.  Called function adds -Wno-unused-parameter
			# to work around the bug, but affected users will not get
			# warnings about parameters that are unused in regular
			# functions.
			return
		raise SCons.Errors.StopError(
			"C++ compiler rejects explicitly deleted functions with named parameters, even with -Wno-unused-parameter." \
				if self.check_cxx11_explicit_delete_anonymous(context, f) else \
			"C++ compiler does not support explicitly deleted functions."
		)
	@_implicit_test
	def check_cxx11_explicit_delete_named(self,context,f):
		"""
help:assume compiler supports explicitly deleted functions with named parameters
"""
		return self.Compile(context, text=f % 'b', msg='for explicitly deleted functions with named parameters')
	@_implicit_test
	def check_cxx11_explicit_delete_named_unused(self,context,f,_successflags={'CXXFLAGS' : ['-Wno-unused-parameter']}):
		"""
help:assume compiler supports explicitly deleted functions with named parameters with -Wno-unused-parameter
"""
		return self.Compile(context, text=f % 'b', msg='for explicitly deleted functions with named parameters and -Wno-unused-parameter', successflags=_successflags)
	@_implicit_test
	def check_cxx11_explicit_delete_anonymous(self,context,f):
		"""
help:assume compiler supports explicitly deleted functions with anonymous parameters
"""
		return self.Compile(context, text=f % '', msg='for explicitly deleted functions with anonymous parameters')
	@_implicit_test
	def check_cxx11_addressof(self,context,_successflags={'CPPDEFINES' : ['DXX_HAVE_CXX11_ADDRESSOF']},**kwargs):
		return self.Compile(context, msg='for C++11 function addressof()', successflags=_successflags, **kwargs)
	@_implicit_test
	def check_boost_addressof(self,context,**kwargs):
		return self.Compile(context, msg='for Boost.Utility function addressof()', successflags={'CPPDEFINES' : ['DXX_HAVE_BOOST_ADDRESSOF']}, **kwargs)
	@_custom_test
	def _check_free_addressof_function(self,context):
		f = '''
#include "compiler-addressof.h"
struct A {
	void operator&();
};
'''
		main = '''
	A b;
	return addressof(b) != 0;
'''
		if not self.check_cxx11_addressof(context, text=f, main=main) and not self.check_boost_addressof(context, text=f, main=main):
			raise SCons.Errors.StopError("C++ compiler does not support free function addressof().")
	@_custom_test
	def check_cxx14_exchange(self,context,_successflags={'CPPDEFINES' : ['DXX_HAVE_CXX14_EXCHANGE']}):
		f = '''
#include "compiler-exchange.h"
'''
		self.Cxx14Compile(context, text=f, main='return exchange(argc, 5)', msg='for C++14 exchange', successflags=_successflags)
	implicit_tests.append(_implicit_test.RecordedTest('check_cxx14_tree_integer_sequence', "assume C++14 integer_sequence handles sequences longer than max template depth"))
	@_custom_test
	def check_cxx14_integer_sequence(self,context,
			_successflags_simple={'CPPDEFINES' : ['DXX_HAVE_CXX14_INTEGER_SEQUENCE']},
			_successflags_tree={'CPPDEFINES' : ['DXX_HAVE_CXX14_TREE_INTEGER_SEQUENCE']}
			):
		f = '''
#include <utility>
using std::integer_sequence;
using std::index_sequence;
'''
		Cxx14Compile = self.Cxx14Compile
		if Cxx14Compile(context, text=f, main='''
/* This test could wrongly classify an implementation as depth-efficient
** if the compiler permits very deep template instantiations.  In
** practice, compilers limit the template depth enough that this should
** not be an issue.
**/
std::make_index_sequence<10000> a;
(void)a;
''', msg='for depth-efficient C++14 integer_sequence', successflags=_successflags_tree):
			return
		Cxx14Compile(context, text=f, msg='for C++14 integer_sequence', successflags=_successflags_simple)
	@_custom_test
	def check_cxx14_make_unique(self,context,_successflags={'CPPDEFINES' : ['DXX_HAVE_CXX14_MAKE_UNIQUE']}):
		f = '''
#include "compiler-make_unique.h"
'''
		main = '''
	make_unique<int>(0);
	make_unique<int[]>(1);
'''
		self.Cxx14Compile(context, text=f, main=main, msg='for C++14 make_unique', successflags=_successflags)
	@_implicit_test
	def check_cxx11_inherit_constructor(self,context,text,_macro_value=_quote_macro_value('''
/* Use a typedef for the base type to avoid parsing issues when type
 * B is a qualified name.  Without this typedef, B = std::BASE would
 * expand as `using std::BASE::std::BASE`, which causes a parsing error.
 * The correct way to inherit from std::BASE is `using std::BASE::BASE;`.
 * With using dxx_constructor_base_type = std::BASE;`,
 * `using dxx_constructor_base_type::dxx_constructor_base_type` produces
 * the correct result.
 */
	using dxx_constructor_base_type = B,##__VA_ARGS__;
	using dxx_constructor_base_type::dxx_constructor_base_type;'''),
		**kwargs):
		"""
help:assume compiler supports inheriting constructors
"""
		blacklist_clang_libcxx = '''
/* Test for bug where clang + libc++ + constructor inheritance causes a
 * compilation failure when returning nullptr.
 *
 * Works: gcc
 * Works: clang + gcc libstdc++
 * Works: old clang + old libc++ (cutoff date unknown).
 * Works: new clang + new libc++ + unique_ptr<T>
 * Fails: new clang + new libc++ + unique_ptr<T[]> (v3.6.0 confirmed broken).

memory:2676:32: error: no type named 'type' in 'std::__1::enable_if<false, std::__1::unique_ptr<int [], std::__1::default_delete<int []> >::__nat>'; 'enable_if' cannot be used to disable this declaration
            typename enable_if<__same_or_less_cv_qualified<_Pp, pointer>::value, __nat>::type = __nat()) _NOEXCEPT
                               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.sconf_temp/conftest_43.cpp:26:11: note: in instantiation of member function 'std::__1::unique_ptr<int [], std::__1::default_delete<int []> >::unique_ptr' requested here
        using B::B;
                 ^
.sconf_temp/conftest_43.cpp:30:2: note: while substituting deduced template arguments into function template 'I' [with _Pp = I]
        return nullptr;
        ^
 */
#include <memory>
class I : std::unique_ptr<int[]>
{
public:
	typedef std::unique_ptr<int[]> B;
	using B::B;
};
I a();
I a()
{
	return nullptr;
}
'''
		return _macro_value \
			if self.Compile(context, text=text.format(leading_text=blacklist_clang_libcxx, macro_value=_macro_value), msg='for C++11 inherited constructors with good unique_ptr<T[]> support', **kwargs) \
			else None
	@_implicit_test
	def check_cxx11_variadic_forward_constructor(self,context,text,_macro_value=_quote_macro_value('''
    template <typename... Args>
        constexpr D(Args&&... args) :
            B,##__VA_ARGS__(std::forward<Args>(args)...) {}
'''),**kwargs):
		"""
help:assume compiler supports variadic template-based constructor forwarding
"""
		return _macro_value \
			if self.Compile(context, text=text.format(leading_text='#include <algorithm>\n', macro_value=_macro_value), msg='for C++11 variadic templates on constructors', **kwargs) \
			else None
	@_custom_test
	def _check_forward_constructor(self,context,_text='''
{leading_text}
#define DXX_INHERIT_CONSTRUCTORS(D,B,...) {macro_value}
struct A {{
	A(int){{}}
}};
struct B:A {{
DXX_INHERIT_CONSTRUCTORS(B,A);
}};
''',
		_macro_define='DXX_INHERIT_CONSTRUCTORS(D,B,...)',
		_methods=(check_cxx11_inherit_constructor, check_cxx11_variadic_forward_constructor)
):
		for f in _methods:
			macro_value = f(self, context, text=_text, main='B(0)')
			if macro_value:
				context.sconf.Define(_macro_define, macro_value, '''
Declare that derived type D inherits applicable constructors from base
type B.  Use a variadic macro with the base type second so that types
such as std::pair<int,int> pass through correctly without the need to
parenthesize them.
''')
				return
		raise SCons.Errors.StopError("C++ compiler does not support constructor forwarding.")
	@_custom_test
	def check_deep_tuple(self,context):
		text = '''
#include <tuple>
static inline std::tuple<{type}> make() {{
	return std::make_tuple({value});
}}
static void a(){{
	std::tuple<{type}> t = make();
	(void)t;
}}
'''
		count = 20
		Compile = self.Compile
		if Compile(context, text=text.format(type=','.join(('int',)*count), value=','.join(('0',)*count)), main='a()', msg='whether compiler handles 20-element tuples'):
			return
		count = 2
		raise SCons.Errors.StopError(
			"Compiler cannot handle tuples of 20 elements.  Raise the template instantiation depth." \
			if Compile(context, text=text.format(type=','.join(('int',)*count), value=','.join(('0',)*count)), main='a()', msg='whether compiler handles 2-element tuples') \
			else "Compiler cannot handle tuples of 2 elements."
		)
	@_implicit_test
	def check_poison_valgrind(self,context):
		'''
help:add Valgrind annotations; wipe certain freed memory when running under Valgrind
'''
		context.Message('%s: checking %s...' % (self.msgprefix, 'whether to use Valgrind poisoning'))
		r = 'valgrind' in self.user_settings.poison
		context.Result(r)
		self._define_macro(context, 'DXX_HAVE_POISON_VALGRIND', int(r))
		if not r:
			return
		text = '''
#define DXX_HAVE_POISON	1
#include "compiler-poison.h"
'''
		main = '''
	DXX_MAKE_MEM_UNDEFINED(&argc, sizeof(argc));
'''
		if self.Compile(context, text=text, main=main, msg='whether Valgrind memcheck header works'):
			return True
		raise SCons.Errors.StopError("Valgrind poison requested, but <valgrind/memcheck.h> does not work.")
	@_implicit_test
	def check_poison_overwrite(self,context):
		'''
help:always wipe certain freed memory
'''
		context.Message('%s: checking %s...' % (self.msgprefix, 'whether to use overwrite poisoning'))
		r = 'overwrite' in self.user_settings.poison
		context.Result(r)
		self._define_macro(context, 'DXX_HAVE_POISON_OVERWRITE', int(r))
		return r
	@_custom_test
	def _check_poison_method(self,context,
		_methods=(check_poison_overwrite, check_poison_valgrind),
		poison=0
	):
		# Always run both checks.  The user may want a program that
		# always uses overwrite poisoning and, when running under
		# Valgrind, marks the memory as undefined.
		for f in _methods:
			if f(self, context):
				poison = 1
		self._define_macro(context, 'DXX_HAVE_POISON', poison)
	implicit_tests.append(_implicit_test.RecordedTest('check_size_type_size', "assume size_t is formatted as `size_t`"))
	implicit_tests.append(_implicit_test.RecordedTest('check_size_type_long', "assume size_t is formatted as `unsigned long`"))
	implicit_tests.append(_implicit_test.RecordedTest('check_size_type_int', "assume size_t is formatted as `unsigned int`"))
	implicit_tests.append(_implicit_test.RecordedTest('check_size_type_I64', "assume size_t is formatted as `unsigned I64`"))
	@_custom_test
	def _check_size_type_format_modifier(self,context,_text='''
#include <cstddef>
#define DXX_PRI_size_type %s
__attribute_format_printf(1, 2)
void f(const char *, ...);
void f(const char *, ...)
{
}
''',_main='''
	std::size_t s = 0;
	f("%" DXX_PRI_size_type, s);
'''):
		'''
The test must declare a custom function to call with this format string.
gcc has hardcoded knowledge about how printf works, but that knowledge
on Mingw64 differs from the processing of
__attribute__((format(printf,...))).  Mingw64 requires I64u for
__attribute__((format)) functions, but llu for printf.  Mingw32 is
consistent in its use of u.  Linux gcc is consistent in its use of
lu.

-- cut --
#include <cstdio>
#include <cstddef>
__attribute__((format(printf,1,2))) void f(const char *,...);
void a() {
	std::size_t b = 0;
	printf("%I64u", b);
	f("%I64u", b);
	printf("%llu", b);
	f("%llu", b);
	printf("%lu", b);
	f("%lu", b);
	printf("%u", b);
	f("%u", b);
}
-- cut --

$ x86_64-w64-mingw32-g++-5.4.0 -x c++ -S -Wformat -o /dev/null -
<stdin>: In function 'void a()':
<stdin>:6:19: warning: format '%u' expects argument of type 'unsigned int', but argument 2 has type 'std::size_t {aka long long unsigned int}' [-Wformat=]
<stdin>:9:13: warning: unknown conversion type character 'l' in format [-Wformat=]
<stdin>:9:13: warning: too many arguments for format [-Wformat-extra-args]
<stdin>:10:17: warning: format '%lu' expects argument of type 'long unsigned int', but argument 2 has type 'std::size_t {aka long long unsigned int}' [-Wformat=]
<stdin>:11:12: warning: format '%lu' expects argument of type 'long unsigned int', but argument 2 has type 'std::size_t {aka long long unsigned int}' [-Wformat=]
<stdin>:12:16: warning: format '%u' expects argument of type 'unsigned int', but argument 2 has type 'std::size_t {aka long long unsigned int}' [-Wformat=]
<stdin>:13:11: warning: format '%u' expects argument of type 'unsigned int', but argument 2 has type 'std::size_t {aka long long unsigned int}' [-Wformat=]

$ i686-w64-mingw32-g++-5.4.0 -x c++ -S -Wformat -o /dev/null -
<stdin>: In function 'void a()':
<stdin>:7:14: warning: format '%I64u' expects argument of type 'long long unsigned int', but argument 2 has type 'std::size_t {aka unsigned int}' [-Wformat=]
<stdin>:8:18: warning: format '%llu' expects argument of type 'long long unsigned int', but argument 2 has type 'std::size_t {aka unsigned int}' [-Wformat=]
<stdin>:9:13: warning: unknown conversion type character 'l' in format [-Wformat=]
<stdin>:9:13: warning: too many arguments for format [-Wformat-extra-args]
<stdin>:10:17: warning: format '%lu' expects argument of type 'long unsigned int', but argument 2 has type 'std::size_t {aka unsigned int}' [-Wformat=]
<stdin>:11:12: warning: format '%lu' expects argument of type 'long unsigned int', but argument 2 has type 'std::size_t {aka unsigned int}' [-Wformat=]

$ mingw32-g++-5.4.0 -x c++ -S -Wformat -o /dev/null -
<stdin>: In function 'void a()':
<stdin>:6:19: warning: format '%I64u' expects argument of type 'long long unsigned int', but argument 2 has type 'std::size_t {aka unsigned int}' [-Wformat=]
<stdin>:7:14: warning: format '%I64u' expects argument of type 'long long unsigned int', but argument 2 has type 'std::size_t {aka unsigned int}' [-Wformat=]
<stdin>:8:18: warning: unknown conversion type character 'l' in format [-Wformat=]
<stdin>:8:18: warning: too many arguments for format [-Wformat-extra-args]
<stdin>:9:13: warning: unknown conversion type character 'l' in format [-Wformat=]
<stdin>:9:13: warning: too many arguments for format [-Wformat-extra-args]
<stdin>:10:17: warning: format '%lu' expects argument of type 'long unsigned int', but argument 2 has type 'std::size_t {aka unsigned int}' [-Wformat=]
<stdin>:11:12: warning: format '%lu' expects argument of type 'long unsigned int', but argument 2 has type 'std::size_t {aka unsigned int}' [-Wformat=]

$ x86_64-pc-linux-gnu-g++-5.4.0 -x c++ -S -Wformat -o /dev/null -
<stdin>: In function 'void a()':
<stdin>:6:19: warning: format '%u' expects argument of type 'unsigned int', but argument 2 has type 'std::size_t {aka long unsigned int}' [-Wformat=]
<stdin>:7:14: warning: format '%u' expects argument of type 'unsigned int', but argument 2 has type 'std::size_t {aka long unsigned int}' [-Wformat=]
<stdin>:8:18: warning: format '%llu' expects argument of type 'long long unsigned int', but argument 2 has type 'std::size_t {aka long unsigned int}' [-Wformat=]
<stdin>:9:13: warning: format '%llu' expects argument of type 'long long unsigned int', but argument 2 has type 'std::size_t {aka long unsigned int}' [-Wformat=]
<stdin>:12:16: warning: format '%u' expects argument of type 'unsigned int', but argument 2 has type 'std::size_t {aka long unsigned int}' [-Wformat=]
<stdin>:13:11: warning: format '%u' expects argument of type 'unsigned int', but argument 2 has type 'std::size_t {aka long unsigned int}' [-Wformat=]

'''
		# Test types in order of decreasing probability.
		for how in (
			# Linux
			('z', 'size_type_size'),
			('l', 'size_type_long'),
			# Win64
			('I64', 'size_type_I64'),
			# Win32
			('', 'size_type_int'),
		):
			DXX_PRI_size_type = how[0]
			f = '"%su"' % DXX_PRI_size_type
			if self.Compile(context, text=_text % f, main=_main, msg='whether to format std::size_t with "%%%su"' % DXX_PRI_size_type, calling_function=how[1]):
				context.sconf.Define('DXX_PRI_size_type', f)
				return
		raise SCons.Errors.StopError("C++ compiler rejects all candidate format strings for std::size_t.")
	implicit_tests.append(_implicit_test.RecordedTest('check_compiler_accepts_useless_cast', "assume compiler accepts -Wuseless-cast"))
	@_custom_test
	def check_compiler_useless_cast(self,context):
		Compile = self.Compile
		flags = {'CXXFLAGS' : [get_Werror_string(context.env['CXXFLAGS']) + 'useless-cast']}
		if Compile(context, text='''
/*
 * SDL on Raspbian provokes a warning from -Wuseless-cast
 *
 * Reported-by: derhass <https://github.com/dxx-rebirth/dxx-rebirth/issues/257>
 */
#include <SDL_endian.h>

/*
 * Recent gcc[1] create a useless cast when synthesizing constructor
 * inheritance, then warn the user about the compiler-generated cast.
 * Since the user did not write the cast in the source, the user
 * cannot remove the cast to eliminate the warning.
 *
 * The only way to avoid the problem is to avoid using constructor
 * inheritance in cases where the compiler would synthesize a useless
 * cast.
 *
 * Reported-by: zicodxx <https://github.com/dxx-rebirth/dxx-rebirth/issues/316>
 * gcc Bugzilla: <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70844>
 *
 * [1] gcc-6.x, gcc-7.x (all currently released versions)
 */
class base
{
public:
	base(int &) {}
};

class derived : public base
{
public:
	using base::base;
};

''', main='''
	derived d(argc);
	return SDL_Swap32(argc);
''', msg='whether compiler argument -Wuseless-cast works with SDL and with constructor inheritance', successflags=flags):
			return
		# <=clang-3.7 does not understand -Wuseless-cast
		# This test does not influence the compile environment, but is
		# run to distinguish in the output whether the failure is
		# because the compiler does not accept -Wuseless-cast or because
		# SDL's headers provoke a warning from -Wuseless-cast.
		Compile(context, text='', main='', msg='whether compiler accepts -Wuseless-cast', testflags=flags, calling_function='compiler_accepts_useless_cast')
	@_custom_test
	def check_compiler_ptrdiff_cast_int(self,context):
		context.sconf.Define('DXX_ptrdiff_cast_int', 'static_cast<int>'
			if self.Compile(context, text='''
#include <cstdio>
''', main='''
	char a[8];
	snprintf(a, sizeof(a), "%.*s", static_cast<int>(&argv[0][1] - &argv[0][0]), "0");
''', msg='whether to cast operator-(T*,T*) to int')
			else '',
		'''
For mingw32-gcc-5.4.0 and x86_64-pc-linux-gnu-gcc-5.4.0, gcc defines
`long operator-(T *, T *)`.

For mingw32, gcc reports a useless cast converting `long` to `int`.
For x86_64-pc-linux-gnu, gcc does not report a useless cast converting
`long` to `int`.

Various parts of the code take the difference of two pointers, then cast
it to `int` to be passed as a parameter to `snprintf` field width
conversion `.*`.  The field width conversion is defined to take `int`,
so the cast is necessary to avoid a warning from `-Wformat` on
x86_64-pc-linux-gnu, but is not necessary on mingw32.  However, the cast
causes a -Wuseless-cast warning on mingw32.  Resolve these conflicting
requirements by defining a macro that expands to `static_cast<int>` on
platforms where the cast is required and expands to nothing on platforms
where the cast is useless.
'''
		)
	@_custom_test
	def check_strcasecmp_present(self,context,_successflags={'CPPDEFINES' : ['DXX_HAVE_STRCASECMP']}):
		main = '''
	return !strcasecmp(argv[0], argv[0] + 1) && !strncasecmp(argv[0] + 1, argv[0], 1);
'''
		self.Compile(context, text='#include <cstring>', main=main, msg='for strcasecmp', successflags=_successflags)
	@_custom_test
	def check_getaddrinfo_present(self,context,_successflags={'CPPDEFINES' : ['DXX_HAVE_GETADDRINFO']}):
		self.Compile(context, text='''
#ifdef WIN32
#include <winsock2.h>
#include <ws2tcpip.h>
#else
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#endif
''', main='''
	addrinfo *res = nullptr;
	addrinfo hints{};
#ifdef AI_NUMERICSERV
	/* Test that it is defined to a term that can be used with bit-or */
	hints.ai_flags |= AI_NUMERICSERV;
#endif
#if DXX_USE_IPv6
	hints.ai_flags |= AI_V4MAPPED | AI_ALL;
#endif
	int i = getaddrinfo("", "", &hints, &res);
	(void)i;
	freeaddrinfo(res);
	return 0;
''', msg='for getaddrinfo', successflags=_successflags)
	@_guarded_test_windows
	def check_inet_ntop_present(self,context,_successflags={'CPPDEFINES' : ['DXX_HAVE_INET_NTOP']}):
		# Linux and OS X have working inet_ntop on all supported
		# platforms.  Only Windows sometimes lacks support for this
		# function.
		if self.Compile(context, text='''
#include <winsock2.h>
#include <ws2tcpip.h>
''', main='''
	struct sockaddr_in sai;
	char dbuf[64];
	return inet_ntop(AF_INET, &sai.sin_addr, dbuf, sizeof(dbuf)) ? 0 : 1;
''', msg='for inet_ntop', successflags=_successflags):
			return
		if self.user_settings.ipv6:
			raise SCons.Errors.StopError("IPv6 enabled and inet_ntop not available: disable IPv6 or upgrade headers to support inet_ntop.")
	@_custom_test
	def check_timespec_present(self,context,_successflags={'CPPDEFINES' : ['DXX_HAVE_STRUCT_TIMESPEC']}):
		self.Compile(context, text='''
#include <time.h>
''', main='''
	struct timespec ts;
	(void)ts;
	return 0;
''', msg='for struct timespec', successflags=_successflags)

	@_implicit_test
	def check_warn_implicit_fallthrough(self,context,text,main,testflags,_successflags={'CXXFLAGS' : ['-Wimplicit-fallthrough=5']}):
		self.Compile(context, text=text, main=main, msg='for -Wimplicit-fallthrough=5', testflags=testflags, successflags=_successflags)

	@_implicit_test
	def check_no_warn_implicit_fallthrough(self,context,_successflags={'CXXFLAGS' : ['-Wno-implicit-fallthrough']}):
		self.Compile(context, text='', main='', msg='for -Wno-implicit-fallthrough', successflags=_successflags)

	@_custom_test
	def check_boost_config(self,context,_successflags={'CPPDEFINES' : [('DXX_BOOST_FALLTHROUGH', 'BOOST_FALLTHROUGH')]}):
		text ='''
#include <boost/config.hpp>
'''
		main = '''
	int a = 1;
	switch (argc) {
		case 1:
			++ a;
			DXX_BOOST_FALLTHROUGH;
		case 2:
			++ a;
			break;
	}
	(void)a;
'''
		sconf = context.sconf
		if not self.Compile(context, text=text, main=main, msg='for Boost.Config', successflags=_successflags):
			sconf.Define('DXX_BOOST_FALLTHROUGH', '((void)0)')
			self.check_no_warn_implicit_fallthrough(context)
			return
		else:
			sconf.config_h_text += '''
#ifndef DXX_SCONF_NO_INCLUDES
/* For BOOST_FALLTHROUGH */
#include <boost/config.hpp>
#endif
'''
		self.check_warn_implicit_fallthrough(context, text, main, testflags=_successflags)

	@_custom_test
	def check_compiler_overzealous_unused_lambda_capture(self,context):
		'''
<clang-5: untested
>clang-8: untested
>=clang-5 && <=clang-8: when -Wunused is passed, clang will warn when a lambda captures by reference a local variable that is itself a reference, regardless of whether the lambda body uses the captured value.  The warning is:

```
similar/main/object.cpp:1060:13: error: lambda capture 'vmobjptr' is not required to be captured for this use [-Werror,-Wunused-lambda-capture]
	auto l = [&vmobjptr, &r, &num_to_free](bool (*predicate)(const vcobjptr_t)) -> bool {
```

<gcc-8 require such variables to be captured and will fail the build if the capture is removed.
>=gcc-8 permit the variable not to be captured, and will not warn regardless of whether it is captured.

Test whether the compiler warns for this case and, if it does, tell it
not to warn.  Once support is removed for gcc versions which require the
capture, this test can be dropped and the warning reinstated.

If clang learns to treat -Wunused-lambda-capture (by way of -Wunused) as
a request to warn only about captures that are _actually_ unused, rather
than also those that are used but not required, this test will stop
disabling the warning on clang.  Since this quirk was discussed when the
warning was added[1], and the warning was added in its current form
anyway, it seems unlikely this will be fixed soon.

[1]: https://marc.info/?l=cfe-commits&m=148494796318826&w=2
|: https://marc.info/?l=cfe-commits&m=148509467111194&w=2
|: https://marc.info/?l=cfe-commits&m=148520882106501&w=2
		'''
		if not self.Compile(context, text='''
int a;
''', main='''
	auto &b = a;
	[&b]() {
		++b;
	}();
''', msg='whether compiler allows lambda capture of local references'):
			self.successful_flags['CXXFLAGS'].append('-Wno-unused-lambda-capture')

	__preferred_compiler_options = (
		'-fvisibility=hidden',
		'-Wduplicated-branches',
		'-Wduplicated-cond',
		'-Wsuggest-attribute=noreturn',
		'-Wlogical-op',
		'-Wold-style-cast',
	)
	__preferred_win32_linker_options = (
		'-Wl,--large-address-aware',
		'-Wl,--dynamicbase',
		'-Wl,--nxcompat',
	)
	# No build directives can modify the process environment, so
	# modifying this at class scope is safe.  Either every build will
	# have $SOURCE_DATE_EPOCH set or every build will have it clear.
	if os.getenv('SOURCE_DATE_EPOCH') is None:
		__preferred_win32_linker_options += ('-Wl,--insert-timestamp',)
	def __mangle_compiler_option_name(opt):
		return 'check_compiler_option%s' % opt.replace('-', '_').replace('=', '_')
	def __mangle_linker_option_name(opt):
		return 'check_linker_option%s' % opt.replace('-', '_').replace(',', '_')
	@_custom_test
	def check_preferred_compiler_options(self,context,
		ccopts=__preferred_compiler_options,
		ldopts=(),
		_text='''
/* clang on OS X incorrectly diagnoses mistakes in Apple system headers
 * even when -Wsystem-headers is not specified.  Include one known buggy
 * header here, so that the compilation will fail and the compiler will be
 * marked as not supporting -Wold-style-cast.
 */
#if defined(__APPLE__) && defined(__MACH__)
#include <HIServices/Processes.h>
#endif

/* gcc's warning -Wduplicated-branches was initially overzealous and
 * warned if the branches were identical after expanding template
 * parameters.  This was documented in gcc bug #82541, which was fixed
 * for gcc-8.x.  As of this writing, the fix has not been backported to
 * gcc-7.x.
 *
 * Work around this unwanted quirk by including code which will provoke
 * a -Wduplicated-branches warning in affected versions, but not in
 * fixed versions, so that the configure stage blacklists the warning on
 * affected versions.
 */

namespace gcc_pr82541 {

template <unsigned U1, unsigned U2>
unsigned u(bool b)
{
	return b ? U1 : U2;
}

unsigned u2(bool b);
unsigned u2(bool b)
{
	return u<1, 1>(b);
}

}
''',
		_mangle_compiler_option_name=__mangle_compiler_option_name,
		_mangle_linker_option_name=__mangle_linker_option_name
	):
		if self.user_settings.host_platform == 'win32':
			ldopts = self.__preferred_win32_linker_options
		Compile = self.Compile
		Link = self.Link
		f, desc = (Link, 'linker') if ldopts else (Compile, 'compiler')
		if f(context, text=_text, main='', msg='whether %s accepts preferred options' % desc, successflags={'CXXFLAGS' : ccopts, 'LINKFLAGS' : ldopts}, calling_function='preferred_%s_options' % desc):
			# Everything is supported.  Skip individual tests.
			return
		# Compiler+linker together failed.  Check if compiler alone will work.
		if f is Compile or not Compile(context, text=_text, main='', msg='whether compiler accepts preferred options', successflags={'CXXFLAGS' : ccopts}):
			# Compiler alone failed.
			# Run down the individual compiler options to find any that work.
			for opt in ccopts:
				Compile(context, text=_text, main='', msg='whether compiler accepts option %s' % opt, successflags={'CXXFLAGS' : (opt,)}, calling_function=_mangle_compiler_option_name(opt)[6:])
		# Run down the individual linker options to find any that work.
		for opt in ldopts:
			Link(context, text=_text, main='', msg='whether linker accepts option %s' % opt, successflags={'LINKFLAGS' : (opt,)}, calling_function=_mangle_linker_option_name(opt)[6:])
	@classmethod
	def register_preferred_compiler_options(cls,
		ccopts = __preferred_compiler_options,
		# Always register target-specific tests on the class.  Individual
		# targets will decide whether to run the tests.
		ldopts = __preferred_win32_linker_options,
		RecordedTest = Collector.RecordedTest,
		record = implicit_tests.append,
		_mangle_compiler_option_name=__mangle_compiler_option_name,
		_mangle_linker_option_name=__mangle_linker_option_name
	):
		del cls.register_preferred_compiler_options
		record(RecordedTest('check_preferred_linker_options', 'assume linker accepts preferred options'))
		mangle = _mangle_compiler_option_name
		for opt in ccopts:
			record(RecordedTest(mangle(opt), 'assume compiler accepts %s' % opt))
		mangle = _mangle_linker_option_name
		for opt in ldopts:
			record(RecordedTest(mangle(opt), 'assume linker accepts %s' % opt))
		assert cls.custom_tests[0].name == cls.check_cxx_works.__name__, cls.custom_tests[0].name
		assert cls.custom_tests[-1].name == cls._restore_cxx_prefix.__name__, cls.custom_tests[-1].name

	@_implicit_test
	def check_boost_test(self,context):
		self._check_system_library(context, header=('boost/test/unit_test.hpp',), pretext='''
#define BOOST_TEST_DYN_LINK
#define BOOST_TEST_MODULE Rebirth
''', main=None, lib='Boost.Test', text='''
BOOST_AUTO_TEST_CASE(f)
{
	BOOST_TEST(true);
}
''', testflags={'LIBS' : ['boost_unit_test_framework']})

	@_custom_test
	def _check_boost_test_required(self,context):
		register_runtime_test_link_targets = self.user_settings.register_runtime_test_link_targets
		context.Display('%s: checking whether to build runtime tests...' % self.msgprefix)
		context.Result(register_runtime_test_link_targets)
		if register_runtime_test_link_targets:
			self.check_boost_test(context)

	# This must be the last custom test.  It does not test the environment,
	# but is responsible for reversing test-environment-specific changes made
	# by check_cxx_works.
	@_custom_test
	def _restore_cxx_prefix(self,context):
		sconf = context.sconf
		sconf.config_h_text = self.__commented_tool_versions + sconf.config_h_text
		context.env['CXXCOM'] = self.__cxx_com_prefix
		context.did_show_result = True

ConfigureTests.register_preferred_compiler_options()

class cached_property(object):
	def __init__(self,f):
		self.method = f
		self.name = f.__name__
	def __get__(self,instance,cls):
		# This should never be accessed directly on the class.
		assert instance is not None
		name = self.name
		d = instance.__dict__
		# After the first access, Python should find the cached value in
		# the instance dictionary instead of calling __get__ again.
		assert name not in d
		d[name] = r = self.method(instance)
		return r

class LazyObjectConstructor(object):
	class LazyObjectState:
		def __init__(self,sources,transform_env=None,StaticObject_hook=None,transform_target=None):
			# `sources` must be non-empty, since it would have no use if
			# it was empty.
			#
			# Every element in `sources` must be a string.  Verify this
			# with an assertion that directly checks that the sequence
			# is not empty and indirectly, by way of attribute lookup,
			# checks that the elements are string-like.
			assert([s.encode for s in sources]), "sources must be a non-empty list of strings"
			self.sources = sources
			self.transform_env = transform_env
			self.StaticObject_hook = StaticObject_hook
			# If transform_target is not used, let references to
			# `self.transform_target` fall through to
			# `cls.transform_target`.
			if transform_target:
				self.transform_target = transform_target

		@staticmethod
		def transform_target(_, name, _splitext=os.path.splitext):
			return _splitext(name)[0]

	def __lazy_objects(self,source,
			cache={}
		):
		env = self.env
		# Use id because name needs to be hashable and have a 1-to-1
		# mapping to source.
		name = (id(env), id(source))
		value = cache.get(name)
		if value is None:
			prepare_target_name = '{}{}'.format
			StaticObject = env.StaticObject
			OBJSUFFIX = env['OBJSUFFIX']
			builddir = self.builddir
			value = []
			append = value.append
			for s in source:
				transform_target = s.transform_target
				transform_env = s.transform_env
				StaticObject_hook = s.StaticObject_hook
				for srcname in s.sources:
					target = builddir.File(prepare_target_name(transform_target(self, srcname), OBJSUFFIX))
					s = StaticObject(target=target, source=srcname,
							**({} if transform_env is None else transform_env(self, env))
							)
					append(s)
					if StaticObject_hook is not None:
						StaticObject_hook(self, env, srcname, target, s)
			# Convert to a tuple so that attempting to modify a cached
			# result raises an error.
			value = tuple(value)
			cache[name] = value
		return value

	def create_lazy_object_states_getter(states,__lazy_objects=__lazy_objects):
		def get_objects(self):
			return __lazy_objects(self, states)
		return get_objects

	@staticmethod
	def create_lazy_object_getter(sources,LazyObjectState=LazyObjectState,create_lazy_object_states_getter=create_lazy_object_states_getter):
		return create_lazy_object_states_getter((LazyObjectState(sources=sources),))

	create_lazy_object_states_getter = staticmethod(create_lazy_object_states_getter)

class FilterHelpText:
	_sconf_align = None
	def __init__(self):
		self.visible_arguments = []
	def FormatVariableHelpText(self, env, opt, help, default, actual, aliases):
		if not opt in self.visible_arguments:
			return ''
		if not self._sconf_align:
			self._sconf_align = len(max((s for s in self.visible_arguments if s[:6] == 'sconf_'), key=len))
		l = []
		if default is not None:
			if isinstance(default, str) and not default.isalnum():
				default = '"%s"' % default
			l.append("default: {default}".format(default=default))
		actual = getattr(self, opt, None)
		if actual is not None:
			if isinstance(actual, str) and not actual.isalnum():
				actual = '"%s"' % actual
			l.append("current: {current}".format(current=actual))
		return (" {opt:%u}  {help}{l}\n" % (self._sconf_align if opt[:6] == 'sconf_' else 15)).format(opt=opt, help=help, l=(" [" + "; ".join(l) + "]" if l else ''))

class PCHManager(object):
	class ScannedFile:
		def __init__(self,candidates):
			self.candidates = candidates

	syspch_cpp_filename = None
	ownpch_cpp_filename = None
	syspch_object_node = None
	ownpch_object_node = None
	required_pch_object_node = None

	# Compile on first use, so that non-PCH builds skip the compile
	_re_preproc_match = None
	_re_include_match = None
	_re_singleline_comments_sub = None
	# Source files are tracked at class scope because all builds share
	# the same source tree.
	_cls_scanned_files = None

	# Import required modules when the first PCHManager is created.
	@classmethod
	def __initialize_cls_static_variables(cls):
		from re import compile as c
		# Match C preprocessor directives that start with i or e,
		# capture any arguments, and allow no arguments.  This accepts:
		# - #if
		# - #ifdef
		# - #ifndef
		# - #else
		# - #endif
		# - #include
		# - #error
		cls._re_preproc_match = c(br'#\s*([ie]\w+)(?:\s+(.*))?').match
		# Capture the argument in a #include statement, including the
		# angle brackets or quotes.
		#
		# Rebirth currently has no computed includes, so ignore computed
		# includes.
		cls._re_include_match = c(br'(<[^>]+>|"[^"]+")').match
		# Strip a single-line C++ style comment ("// Text") and any
		# preceding whitespace.  The C preprocessor will discard these
		# when compiling the header.  Discarding them from the
		# environment Value will prevent rebuilding pch.cpp when the
		# only change is in such a comment.
		cls._re_singleline_comments_sub = c(br'\s*//.*').sub
		# dict with key=filename with path, value=ScannedFile
		cls._cls_scanned_files = {}
		from tempfile import mkstemp
		cls._tempfile_mkstemp = staticmethod(mkstemp)

	def __init__(self,program,configure_pch_flags,common_pch_manager):
		if self._re_preproc_match is None:
			self.__initialize_cls_static_variables()
			assert self._re_preproc_match is not None
		self.user_settings = user_settings = program.user_settings
		assert user_settings.syspch or user_settings.pch
		self.env = env = program.env
		# dict with key=fs.File, value=ScannedFile
		self._instance_scanned_files = {}
		self._common_pch_manager = common_pch_manager
		syspch_cpp_filename = ownpch_cpp_filename = None
		syspch_object_node = None
		CXXFLAGS = env['CXXFLAGS'] + configure_pch_flags['CXXFLAGS']
		File = env.File
		builddir = program.builddir
		pch_subdir_node = builddir.Dir(program.srcdir)
		if user_settings.syspch:
			self.syspch_cpp_node = pch_subdir_node.File('syspch.cpp')
			self.syspch_cpp_filename = syspch_cpp_filename = str(self.syspch_cpp_node)
			self.required_pch_object_node = self.syspch_object_node = syspch_object_node = env.StaticObject(target='%s.gch' % syspch_cpp_filename, source=self.syspch_cpp_node, CXXCOM=env._dxx_cxxcom_no_ccache_prefix, CXXFLAGS=CXXFLAGS)
		if user_settings.pch:
			self.ownpch_cpp_node = pch_subdir_node.File('ownpch.cpp')
			self.ownpch_cpp_filename = ownpch_cpp_filename = str(self.ownpch_cpp_node)
			if syspch_object_node:
				CXXFLAGS += ['-include', syspch_cpp_node, '-Winvalid-pch']
			self.required_pch_object_node = self.ownpch_object_node = ownpch_object_node = env.StaticObject(target='%s.gch' % ownpch_cpp_filename, source=self.ownpch_cpp_node, CXXCOM=env._dxx_cxxcom_no_ccache_prefix, CXXFLAGS=CXXFLAGS)
			env.Depends(ownpch_object_node, builddir.File('dxxsconf.h'))
			if syspch_object_node:
				env.Depends(ownpch_object_node, syspch_object_node)
		self.pch_CXXFLAGS = ['-include', self.ownpch_cpp_node or syspch_cpp_node, '-Winvalid-pch']
		# If assume unchanged and the file exists, set __files_included
		# to a dummy value.  This bypasses scanning source files and
		# guarantees that the text of pch.cpp is not changed.  SCons
		# will still recompile pch.cpp into a new .gch file if pch.cpp
		# includes files that SCons recognizes as changed.
		if user_settings.pch_cpp_assume_unchanged and \
			(not syspch_cpp_filename or os.path.exists(syspch_cpp_filename)) and \
			(not ownpch_cpp_filename or os.path.exists(ownpch_cpp_filename)):
			self.__files_included = True
		else:
			# collections.defaultdict with key from ScannedFile.candidates,
			# value is a collections.Counter with key=tuple of preprocessor
			# guards, value=count of times this header was included under
			# that set of guards.
			self.__files_included = defaultdict(collections_counter)
		self.__env_Program = env.Program
		self.__env_StaticObject = env.StaticObject
		env.Program = self.Program
		env.StaticObject = self.StaticObject

	def record_file(self,env,source_file):
		# Every scanned file goes into self._cls_scanned_files to
		# prevent duplicate scanning from multiple targets.
		f = self._cls_scanned_files.get(source_file, None)
		if f is None:
			self._cls_scanned_files[source_file] = f = self.scan_file(env, source_file)
		self._instance_scanned_files[source_file] = f
		return f

	# Scan a file for preprocessor directives related to conditional
	# compilation and file inclusion.
	#
	# The #include directives found are eventually written to pch.cpp
	# with their original preprocessor guards in place.  Since the
	# preprocessor guards are kept and the C preprocessor will evaluate
	# them when compiling the header, this scanner does not attempt to
	# track which branches are true and which are false.
	#
	# This scanner makes no attempt to normalize guard conditions.  It
	# considers each of these examples to be distinct guards, even
	# though a full preprocessor will produce the same result for each:
	#
	#	#if 1
	#	#if 2
	#	#if 3 < 5
	#
	# or:
	#
	#	#ifdef A
	#	#if defined(A)
	#	#if (defined(A))
	#	#if !!defined(A)
	#
	# or:
	#
	# 	#ifndef A
	# 	#else
	# 	#endif
	#
	# 	#ifdef A
	# 	#endif
	#
	# Include directives are followed only if the calling file will not
	# be part of the output pch.cpp.  When the calling file will be in
	# pch.cpp, then the C preprocessor will include the called file, so
	# there is no need to scan it for other headers to include.
	#
	# This scanner completely ignores pragmas, #define, #undef, and
	# computed includes.
	@classmethod
	def scan_file(cls,env,source_filenode):
		match_preproc_directive = cls._re_preproc_match
		match_include_directive = cls._re_include_match
		preceding_line = None
		lines_since_preprocessor = None
		# defaultdict with key=name of header to include, value=set of
		# preprocessor guards under which an include was seen.  Set is
		# used because duplicate inclusions from a single source file
		# should not adjust the usage counter.
		candidates = defaultdict(set)
		# List of currently active preprocessor guards
		guard = []
		header_search_path = None
		os_path_join = os.path.join
		os_path_exists = os.path.exists
		for line in map(bytes.strip, source_filenode.get_contents().splitlines()):
			if preceding_line is not None:
				# Basic support for line continuation.
				line = b'%s %s' % (preceding_line[:-1], line)
				preceding_line = None
			elif not line.startswith(b'#'):
				# Allow unlimited non-preprocessor lines before the
				# first preprocessor line.  Once one preprocessor line
				# is found, track how many lines since the most recent
				# preprocessor line was seen.  If too many
				# non-preprocessor lines appear in a row, assume the
				# scanner is now down in source text and move to the
				# next file.
				if lines_since_preprocessor is not None:
					lines_since_preprocessor += 1
					if lines_since_preprocessor > 50:
						break
				continue
			lines_since_preprocessor = 0
			# Joined lines are rare.  Ignore complicated quoting.
			if line.endswith(b'\\'):
				preceding_line = line
				continue
			m = match_preproc_directive(line)
			if not m:
				# Not a preprocessor directive or not a directive that
				# this scanner handles.
				continue
			directive = m.group(1)
			if directive == b'include':
				m = match_include_directive(m.group(2))
				if not m:
					# This directive is probably a computed include.
					continue
				name = m.group(1)
				bare_name = name[1:-1]
				if name.startswith(b'"'):
					# Canonicalize paths to non-system headers
					if name == b'"dxxsconf.h"':
						# Ignore generated header here.  PCH generation
						# will insert it in the right order.
						continue
					if not name.endswith(b'.h"'):
						# Exclude non-header files from PCH.
						#
						# Starting in gcc-7, static functions defined in
						# valptridx.tcc generate -Wunused-function
						# warnings if the including file does not
						# instantiate any templates that use the static
						# function.
						continue
					if header_search_path is None:
						header_search_path = [
							d.encode() for d in ([os.path.dirname(str(source_filenode))] + env['CPPPATH'])
							# Filter out SDL paths
							if not d.startswith('/')
						]
					name = None
					for d in header_search_path:
						effective_name = os_path_join(d, bare_name)
						if os_path_exists(effective_name):
							name = effective_name
							break
					else:
						# name is None if:
						# - A system header was included using quotes.
						#
						# - A game-specific header was included in a
						# shared file.  A game-specific preprocessor
						# guard will prevent the preprocessor from
						# including the file, but the PCH scan logic
						# looks inside branches that the C preprocessor
						# will evaluate as false.
						continue
					name = env.File(name.decode())
				candidates[name].add(tuple(guard))
			elif directive == b'endif':
				while guard:
					g = guard.pop()
					if g == b'#else':
						# guard should always be True here, but test to
						# avoid ugly errors if scanning an ill-formed
						# source file.
						if guard:
							guard.pop()
						break
					if not g.startswith(b'#elif '):
						break
			elif directive == b'else':
				# #else is handled separately because it has no
				# arguments
				guard.append(b'#%s' % (directive))
			elif directive in (
				b'elif',
				b'if',
				b'ifdef',
				b'ifndef',
			):
				guard.append(b'#%s %s' % (directive, m.group(2)))
			elif directive not in (b'error',):
				raise SCons.Errors.StopError("Scanning %s found unhandled C preprocessor directive %r" % (str(source_filenode), directive))
		return cls.ScannedFile(candidates)

	def _compute_pch_text(self):
		self._compute_indirect_includes()
		own_header_inclusion_threshold = self.user_settings.pch
		sys_header_inclusion_threshold = self.user_settings.syspch
		configured_threshold = 0x7fffffff if self.user_settings.pch_cpp_exact_counts else None
		# defaultdict with key=name of tuple of active preprocessor
		# guards, value=tuple of (included file, count of times file was
		# seen with this set of guards, count of times file would be
		# included with this set of guards defined).
		syscpp_includes = defaultdict(list)
		owncpp_includes = defaultdict(list) if own_header_inclusion_threshold else None
		for included_file, usage_dict in get_dictionary_item_view(self.__files_included):
			if isinstance(included_file, (bytes, str)):
				# System header
				cpp_includes = syscpp_includes
				name = (included_file.encode() if isinstance(included_file, str) else included_file)
				threshold = own_header_inclusion_threshold if sys_header_inclusion_threshold is None else sys_header_inclusion_threshold
			else:
				# Own header
				cpp_includes = owncpp_includes
				name = b'"%s"' % (str(included_file).encode())
				threshold = own_header_inclusion_threshold
			if not threshold:
				continue
			count_threshold = configured_threshold or threshold
			g = usage_dict.get((), 0)
			# As a special case, if this header is included
			# without any preprocessor guards, ignore all the
			# conditional includes.
			guards = \
				[((), g)] if (g >= threshold) else \
				sorted(get_dictionary_item_view(usage_dict), reverse=True)
			while guards:
				preprocessor_guard_directives, local_count_seen = guards.pop()
				total_count_seen = local_count_seen
				if total_count_seen < count_threshold:
					# If not eligible on its own, add in the count from
					# preprocessor guards that are always true when this
					# set of guards is true.  Since the scanner does not
					# normalize preprocessor directives, this is a
					# conservative count of always-true guards.
					g = preprocessor_guard_directives
					while g and total_count_seen < count_threshold:
						g = g[:-1]
						total_count_seen += usage_dict.get(g, 0)
					if total_count_seen < threshold:
						# If still not eligible, skip.
						continue
				cpp_includes[preprocessor_guard_directives].append((name, local_count_seen, total_count_seen))

		if syscpp_includes:
			self.__generated_syspch_lines = self._compute_pch_generated_lines(syscpp_includes)
		if owncpp_includes:
			self.__generated_ownpch_lines = self._compute_pch_generated_lines(owncpp_includes)

	def _compute_pch_generated_lines(self,cpp_includes):
		generated_pch_lines = []
		# Append guarded #include directives for files which passed the
		# usage threshold above.  This loop could try to combine related
		# preprocessor guards, but:
		# - The C preprocessor handles the noncombined guards correctly.
		# - As a native program optimized for text processing, the C
		# preprocessor almost certainly handles guard checking faster
		# than this script could handle guard merging.
		# - This loop runs whenever pch.cpp might be regenerated, even
		# if the result eventually shows that pch.cpp has not changed.
		# The C preprocessor will only run over the file when it is
		# actually changed and is processed to build a new .gch file.
		for preprocessor_guard_directives, included_file_tuples in sorted(get_dictionary_item_view(cpp_includes)):
			generated_pch_lines.append(b'')
			generated_pch_lines.extend(preprocessor_guard_directives)
			# local_count_seen is the direct usage count for this
			# combination of preprocessor_guard_directives.
			#
			# total_count_seen is the sum of local_count_seen and all
			# guards that are a superset of this
			# preprocessor_guard_directives.  The total stops counting
			# when it reaches threshold, so it may undercount actual
			# usage.
			for (name, local_count_seen, total_count_seen) in sorted(included_file_tuples):
				assert(isinstance(name, bytes)), repr(name)
				generated_pch_lines.append(b'#include %s\t// %u %u' % (name, local_count_seen, total_count_seen))
			# d[2] == l if d is '#else' or d is '#elif'
			# Only generate #endif when d is a '#if*' directive, since
			# '#else/#elif' do not introduce a new scope.
			generated_pch_lines.extend(b'#endif' for d in preprocessor_guard_directives if d[2:3] != b'l')
		return generated_pch_lines

	def _compute_indirect_includes(self):
		own_header_inclusion_threshold = None if self.user_settings.pch_cpp_exact_counts else self.user_settings.pch
		# Count how many times each header is used for each preprocessor
		# guard combination.  After the outer loop finishes,
		# files_included is a dictionary that maps the name of the
		# include file to a collections.counter instance.  The mapped
		# counter maps a preprocessor guard to a count of how many times
		# it was used.
		#
		# Given:
		#
		# a.cpp
		# #include "a.h"
		# #ifdef A
		# #include "b.h"
		# #endif
		#
		# b.cpp
		# #include "b.h"
		#
		# files_included = {
		#	'a.h' : { () : 1 }
		#	'b.h' : {
		#		('#ifdef A',) : 1,	# From a.cpp
		#		() : 1,	# From b.cpp
		#	}
		# }
		files_included = self.__files_included
		for scanned_file in get_dictionary_value_view(self._instance_scanned_files):
			for included_file, guards in get_dictionary_item_view(scanned_file.candidates):
				i = files_included[included_file]
				for g in guards:
					i[g] += 1
		# If own_header_inclusion_threshold == 1, then every header
		# found will be listed in pch.cpp, so any indirect headers will
		# be included by the C preprocessor.
		if own_header_inclusion_threshold == 1:
			return
		# For each include file which is below the threshold, scan it
		# for includes which may end up above the threshold.
		File = self.env.File
		includes_to_check = sorted(files_included.iterkeys(), key=str)
		while includes_to_check:
			included_file = includes_to_check.pop()
			if isinstance(included_file, (bytes, str)):
				# System headers are str.  Internal headers are
				# fs.File.
				continue
			guards = files_included[included_file]
			unconditional_use_count = guards.get((), 0)
			if unconditional_use_count >= own_header_inclusion_threshold and own_header_inclusion_threshold:
				# Header will be unconditionally included in the PCH.
				continue
			f = self.record_file(self.env, File(included_file))
			for nested_included_file, nested_guards in sorted(get_dictionary_item_view(f.candidates), key=str):
				if not isinstance(included_file, (bytes, str)) and not nested_included_file in files_included:
					# If the header is a system header, it will be
					# str.  Skip system headers.
					#
					# Otherwise, if it has not been seen before,
					# append it to includes_to_check for recursive
					# scanning.
					includes_to_check.append(nested_included_file)
				i = files_included[nested_included_file]
				# If the nested header is included
				# unconditionally, skip the generator.
				for g in (nested_guards if unconditional_use_count else (a + b for a in guards for b in nested_guards)):
					i[g] += 1

	@classmethod
	def write_pch_inclusion_file(cls,target,source,env):
		target = str(target[0])
		dn, bn = os.path.split(target)
		fd, path = cls._tempfile_mkstemp(suffix='', prefix='%s.' % bn, dir=dn, text=True)
		# source[0].get_contents() returns the comment-stripped form
		os.write(fd, source[0].__generated_pch_text)
		os.close(fd)
		os.rename(path, target)

	def StaticObject(self,target,source,CXXFLAGS=None,*args,**kwargs):
		env = self.env
		source = env.File(source)
		o = self.__env_StaticObject(target=target, source=source, CXXFLAGS=self.pch_CXXFLAGS + (env['CXXFLAGS'] if CXXFLAGS is None else CXXFLAGS), *args, **kwargs)
		# Force an order dependency on the .gch file.  It is never
		# referenced by the command line or the source files, so SCons
		# may not recognize it as an input.
		env.Requires(o, self.required_pch_object_node)
		if self.__files_included is not True:
			self.record_file(env, source)
		return o

	def Program(self,*args,**kwargs):
		self._register_pch_commands()
		if self._common_pch_manager:
			self._common_pch_manager._register_pch_commands()
		return self.__env_Program(*args, **kwargs)

	def _register_pch_commands(self):
		if self.__files_included:
			# Common code calls this function once for each game which
			# uses it.  Only one call is necessary for proper operation.
			# Ignore all later calls.
			return
		self._compute_pch_text()
		syspch_lines = self.__generated_syspch_lines
		pch_begin_banner_template = b'''
// BEGIN PCH GENERATED FILE
// %r
// Threshold=%u

// SConf generated header
#include "dxxsconf.h"
'''
		pch_end_banner = (b'''
// END PCH GENERATED FILE
''',)
		if self.syspch_object_node:
			self._register_write_pch_inclusion(self.syspch_cpp_node,
				(
					(pch_begin_banner_template % (self.syspch_cpp_filename, self.user_settings.syspch),),
					syspch_lines,
					pch_end_banner,
				)
			)
			# ownpch.cpp will include syspch.cpp.gch from the command
			# line, so clear syspch_lines to avoid repeating system
			# includes in ownpch.cpp
			syspch_lines = ()
		if self.ownpch_object_node:
			self._register_write_pch_inclusion(self.ownpch_cpp_node,
				(
					(pch_begin_banner_template % (self.ownpch_cpp_filename, self.user_settings.pch),),
					(b'// System headers' if syspch_lines else b'',),
					syspch_lines,
					(b'''
// Own headers
''',),
					self.__generated_ownpch_lines,
					pch_end_banner,
				)
			)

	def _register_write_pch_inclusion(self,node,lineseq):
		# The contents of pch.cpp are taken from the iterables in
		# lineseq.  Set the contents as an input Value instead of
		# listing file nodes, so that pch.cpp is not rebuilt if a change
		# to a source file does not change what headers are listed in
		# pch.cpp.
		#
		# Strip C++ single line comments so that changes in comments are
		# ignored when deciding whether pch.cpp needs to be rebuilt.
		env = self.env
		text = b'\n'.join(itertools.chain.from_iterable(lineseq))
		v = env.Value(self._re_singleline_comments_sub(b'', text))
		v.__generated_pch_text = text
		# Use env.Command instead of env.Textfile or env.Substfile since
		# the latter use their input both for freshness and as a data
		# source.  This Command writes the commented form of the Value
		# to the file, but uses a comment-stripped form for SCons
		# freshness checking.
		env.Command(node, v, self.write_pch_inclusion_file)

class DXXCommon(LazyObjectConstructor):
	# version number
	VERSION_MAJOR = 0
	VERSION_MINOR = 61
	VERSION_MICRO = 0
	DXX_VERSION_SEQ = ','.join([str(VERSION_MAJOR), str(VERSION_MINOR), str(VERSION_MICRO)])
	pch_manager = None
	runtime_test_boost_tests = None
	# dict compilation_database_dict_fn_to_entries:
	#	key: str: name of JSON file to which the data will be written
	#	value: tuple: (SCons.Environment, list_of_entries_to_write)
	# The first environment to use the named JSON file will be stored as
	# the environment in the tuple, and later used to provide
	# env.Textfile for all the entries written to the file.  When other
	# environments write to the same JSON file, they will append their
	# entries to the original list, and reuse the initial environment.
	# Since the build system does not customize env.Textfile, any
	# instance of it should be equally good.  This design permits
	# writing all the records for a build into a single file, even
	# though the build will use multiple SCons.Environment instances to
	# compile its source files.
	compilation_database_dict_fn_to_entries = {}

	class RuntimeTest(LazyObjectConstructor):
		nodefaultlibs = True
		def __init__(self,target,source):
			self.target = target
			self.source = LazyObjectConstructor.create_lazy_object_getter(source)

	@cached_property
	def program_message_prefix(self):
		return '%s.%d' % (self.PROGRAM_NAME, self.program_instance)

	@cached_property
	def builddir(self):
		return self.env.Dir(self.user_settings.builddir)

	# Settings which affect how the files are compiled
	class UserBuildSettings:
		class IntVariable(object):
			def __new__(cls,key,help,default):
				return (key, help, default, cls._validator, int)
			@staticmethod
			def _validator(key, value, env):
				try:
					int(value)
					return True
				except ValueError:
					raise SCons.Errors.UserError('Invalid value for integer-only option %s: %s.' % (key, value))
		class UIntVariable(IntVariable):
			@staticmethod
			def _validator(key, value, env):
				try:
					if int(value) < 0:
						raise ValueError
					return True
				except ValueError:
					raise SCons.Errors.UserError('Invalid value for unsigned-integer-only option %s: %s.' % (key, value))
		# Paths for the Videocore libs/includes on the Raspberry Pi
		RPI_DEFAULT_VC_PATH='/opt/vc'
		default_OGLES_LIB = 'GLES_CM'
		default_EGL_LIB = 'EGL'
		_default_prefix = '/usr/local'
		__stdout_is_not_a_tty = None
		__has_git_dir = None
		# +/=
		_dxx_extended_identifiers = (r'\u012b', r'\u012f', r'\u013d')
		_dxx_disable_extended_identifiers = ('_2b', '_2f', '_3d')
		def default_poison(self):
			return 'overwrite' if self.debug else 'none'
		def default_builddir(self):
			builddir_prefix = self.builddir_prefix
			builddir_suffix = self.builddir_suffix
			default_builddir = builddir_prefix or ''
			if builddir_prefix is not None or builddir_suffix is not None:
				fields = [
					self.host_platform,
					os.path.basename(self.CXX) if self.CXX else None,
				]
				compiler_flags = '\n'.join((getattr(self, attr) or '').strip() for attr in ['CPPFLAGS', 'CXXFLAGS'])
				if compiler_flags:
					# Mix in CRC of CXXFLAGS to get reasonable uniqueness
					# when flags are changed.  A full hash is
					# unnecessary here.
					crc = binascii.crc32(compiler_flags.encode())
					if crc < 0:
						crc = crc + 0x100000000
					fields.append('{:08x}'.format(crc))
				if self.pch:
					fields.append('p%u' % self.pch)
				elif self.syspch:
					fields.append('sp%u' % self.syspch)
				fields.append(''.join(a[1] if getattr(self, a[0]) else (a[2] if len(a) > 2 else '')
				for a in (
					('debug', 'dbg'),
					('lto', 'lto'),
					('editor', 'ed'),
					('opengl', 'ogl', 'sdl'),
					('opengles', 'es'),
					('raspberrypi', 'rpi'),
				)))
				default_builddir += '-'.join([f for f in fields if f])
				if builddir_suffix is not None:
					default_builddir += builddir_suffix
			return default_builddir
		def default_memdebug(self):
			return self.debug
		# automatic setup for raspberrypi
		def default_opengles(self):
			if self.raspberrypi in ('yes', 'mesa'):
				return True
			return False
		@classmethod
		def default_verbosebuild(cls):
			# Enable verbosebuild when the output is not directed to a
			# terminal.  When output is not a terminal, it is likely
			# either a pager or a log file, both of which can readily
			# handle the very long lines generated by verbose mode.
			r = cls.__stdout_is_not_a_tty
			if r is None:
				isatty = getattr(sys.stdout, 'isatty', None)
				# If isatty is None, then assume output is a TTY.
				cls.__stdout_is_not_a_tty = r = False if isatty is None else not isatty()
			return r
		def default_words_need_alignment(self):
			if self.raspberrypi in ('yes', 'mesa'):
				return True
			return False
		def selected_OGLES_LIB(self):
			if self.raspberrypi == 'yes':
				return 'brcmGLESv2'
			return self.default_OGLES_LIB
		def selected_EGL_LIB(self):
			if self.raspberrypi == 'yes':
				return 'brcmEGL'
			return self.default_EGL_LIB
		def need_dynamic_library_load(self):
			return self.adlmidi == 'runtime'
		def _enable_adlmidi(self):
			return self.adlmidi != 'none'

		def __default_DATA_DIR(self):
			platform_settings_type = self._program.get_platform_settings_type(self.host_platform)
			sharepath = platform_settings_type.sharepath
			if sharepath is None:
				return None
			return sharepath(prefix=self.prefix, program_target=self._program.target)

		def _generic_variable(key,help,default):
			return (key, help, default)
		def __get_configure_tests(tests,_filter=lambda s: s.name[0] != '_'):
			# Construct combined list on first use, then cache it
			# forever.
			try:
				return tests.__configure_tests
			except AttributeError:
				# Freeze the results into a tuple, to prevent accidental
				# modification later.
				#
				# In Python 2, this is merely a safety feature and could
				# be skipped.
				#
				# In Python 3, filter returns an iterable that is
				# exhausted after one full traversal.  Since this object
				# is intended to be retained and reused, the first
				# traversal must copy the results into a container that
				# can be walked multiple times.  A tuple serves this
				# purpose, in addition to freezing the contents.
				tests.__configure_tests = c = tuple(filter(_filter, tests.implicit_tests + tests.custom_tests))
				return c
		@classmethod
		def __get_has_git_dir(cls):
			r = cls.__has_git_dir
			if r is None:
				# SConstruct is always at the top of the repository.
				# The user might have run `scons` from elsewhere and
				# used `-f` to indicate this file, but a false negative
				# is acceptable here.
				cls.__has_git_dir = r = os.path.exists(os.environ.get('GIT_DIR', '.git'))
			return r
		def _options(self,
				__get_configure_tests=__get_configure_tests,
				generic_variable=_generic_variable,
				BoolVariable=BoolVariable,
				EnumVariable=EnumVariable,
				conftests=ConfigureTests,
				getenv=os.environ.get
			):
			tests = __get_configure_tests(conftests)
			expect_sconf_tuple = ('0', '1', conftests.expect_sconf_success, conftests.expect_sconf_failure)
			sconf_tuple = ('0', '1', '2', conftests.sconf_force_failure, conftests.sconf_force_success, conftests.sconf_assume_success)
			sys_platform = sys.platform
			for platform in ('linux', 'freebsd', 'openbsd'):
				if sys_platform.startswith(platform):
					sys_platform = platform
					break
			return (
			{
				'variable': EnumVariable,
				'arguments': [
					('expect_sconf_%s' % t.name[6:],
						None,
						None,
						{'allowed_values' : expect_sconf_tuple}
					) for t in tests
				],
			},
			{
				'variable': EnumVariable,
				'arguments': [
					('sconf_%s' % t.name[6:],
						None,
						t.desc or ('assume result of %s' % t.name),
						{'allowed_values' : sconf_tuple}
					) for t in tests
				],
			},
			{
				'variable': EnumVariable,
				'arguments': (
					('host_platform',
						sys_platform,
						'cross-compile to specified platform',
						{
							'map': {'msys':'win32'},
							'allowed_values' : ('darwin', 'linux', 'freebsd', 'openbsd', 'win32'),
							}
						),
					('raspberrypi', None, 'build for Raspberry Pi (automatically selects opengles)', {'ignorecase': 2, 'map': {'1':'yes', 'true':'yes', '0':'no', 'false':'no'}, 'allowed_values': ('yes', 'no', 'mesa')}),
				),
			},
			{
				'variable': BoolVariable,
				'arguments': (
					('record_sconf_results', False, 'write sconf results to dxxsconf.h'),
					('git_describe_version', self.__get_has_git_dir(), 'include git --describe in extra_version'),
					('git_status', True, 'include git status'),
					('versid_depend_all', False, 'rebuild vers_id.cpp if any object file changes'),
				),
			},
			{
				'variable': generic_variable,
				'arguments': (
					('rpi_vc_path', self.RPI_DEFAULT_VC_PATH, 'directory for RPi VideoCore libraries'),
					('opengles_lib', self.selected_OGLES_LIB, 'name of the OpenGL ES library to link against'),
					('egl_lib', self.selected_EGL_LIB, 'name of the OpenGL ES Graphics Library to link against'),
					('prefix', self._default_prefix, 'installation prefix directory (Linux only)'),
					('sharepath', self.__default_DATA_DIR, 'directory for shared game data'),
				),
			},
			{
				'variable': self.UIntVariable,
				'arguments': (
					('lto', 0, 'enable gcc link time optimization'),
					('pch', None, 'pre-compile own headers used at least this many times'),
					('syspch', None, 'pre-compile system headers used at least this many times'),
					('max_joysticks', 8, 'maximum number of usable joysticks'),
					('max_axes_per_joystick', 128, 'maximum number of axes per joystick'),
					('max_buttons_per_joystick', 128, 'maximum number of buttons per joystick'),
					('max_hats_per_joystick', 4, 'maximum number of hats per joystick'),
				),
			},
			{
				'variable': BoolVariable,
				'arguments': (
					('pch_cpp_assume_unchanged', False, 'assume text of *pch.cpp is unchanged'),
					('pch_cpp_exact_counts', False, None),
					('check_header_includes', False, 'compile test each header (developer option)'),
					('debug', False, 'build DEBUG binary which includes asserts, debugging output, cheats and more output'),
					('memdebug', self.default_memdebug, 'build with malloc tracking'),
					('opengl', True, 'build with OpenGL support'),
					('opengles', self.default_opengles, 'build with OpenGL ES support'),
					('editor', False, 'include editor into build (!EXPERIMENTAL!)'),
					('sdl2', False, 'use libSDL2+SDL2_mixer (!EXPERIMENTAL!)'),
					('sdlmixer', True, 'build with SDL_Mixer support for sound and music (includes external music support)'),
					('ipv6', False, 'enable UDP/IPv6 for multiplayer'),
					('use_udp', True, 'enable UDP support'),
					('use_tracker', True, 'enable Tracker support (requires UDP)'),
					('verbosebuild', self.default_verbosebuild, 'print out all compiler/linker messages during building'),
					# This is only examined for Windows targets, so
					# there is no need to make the default value depend
					# on the host_platform.
					('windows_minidump', True, 'generate a minidump on unhandled C++ exception'),
					('words_need_alignment', self.default_words_need_alignment, 'align words at load (needed for many non-x86 systems)'),
					('register_compile_target', True, 'report compile targets to SCons core'),
					('register_cpp_output_targets', None, None),
					('register_runtime_test_link_targets', False, None),
					('enable_build_failure_summary', True, 'print failed nodes and their commands'),
					('wrap_PHYSFS_read', False, None),
					('wrap_PHYSFS_write', False, None),
					# This is intentionally undocumented.  If a bug
					# report includes a log with this set to False, the
					# reporter will be asked to provide a log with the
					# value set to True.  Try to prevent the extra round
					# trip by hiding the option.
					('show_tool_version', True, None),
					# Only applicable if show_tool_version=True
					('show_assembler_version', True, None),
					('show_linker_version', True, None),
				),
			},
			{
				'variable': generic_variable,
				'arguments': (
					('CHOST', getenv('CHOST'), 'CHOST of output'),
					('CXX', getenv('CXX'), 'C++ compiler command'),
					('PKG_CONFIG', getenv('PKG_CONFIG'), 'PKG_CONFIG to run (Linux only)'),
					('RC', getenv('RC'), 'Windows resource compiler command'),
					('extra_version', None, 'text to append to version, such as VCS identity'),
					('ccache', None, 'path to ccache'),
					('compilation_database', None, None),
					('distcc', None, 'path to distcc'),
					('distcc_hosts', getenv('DISTCC_HOSTS'), 'hosts to distribute compilation'),
				),
			},
			{
				'variable': generic_variable,
				'stack': ' ',
				'arguments': (
					('CPPFLAGS', getenv('CPPFLAGS'), 'C preprocessor flags'),
					('CXXFLAGS', getenv('CXXFLAGS'), 'C++ compiler flags'),
					('LINKFLAGS', getenv('LDFLAGS'), 'Linker flags'),
					('LIBS', getenv('LIBS'), 'Libraries to link'),
					# These are intentionally undocumented.  They are
					# meant for developers who know the implications of
					# using them.
					('CPPFLAGS_unchecked', None, None),
					('CXXFLAGS_unchecked', None, None),
					('LINKFLAGS_unchecked', None, None),
				),
			},
			{
				'variable': EnumVariable,
				'arguments': (
					('host_endian', None, 'endianness of host platform', {'allowed_values' : ('little', 'big')}),
					('adlmidi', 'none', 'include ADL MIDI support (none: disabled; runtime: dynamically load at runtime)', {'allowed_values' : ('none', 'runtime')}),
					('screenshot', 'png', 'screenshot file format', {'allowed_values' : ('none', 'legacy', 'png')}),
				),
			},
			{
				'variable': ListVariable,
				'arguments': (
					('poison', self.default_poison, 'method for poisoning free memory', {'names' : ('valgrind', 'overwrite')}),
				),
			},
			{
				'variable': generic_variable,
				'arguments': (
					('builddir_prefix', None, 'prefix to generated build directory'),
					('builddir_suffix', None, 'suffix to generated build directory'),
					# This must be last so that default_builddir will
					# have access to other properties.
					('builddir', self.default_builddir, 'build in specified directory'),
				),
			},
		)
		_generic_variable = staticmethod(_generic_variable)

		@staticmethod
		def _names(name,prefix):
			return ['%s%s%s' % (p, '_' if p else '', name) for p in prefix]

		def __init__(self,program=None):
			self._program = program

		def register_variables(self,prefix,variables,filtered_help):
			self.known_variables = []
			append_known_variable = self.known_variables.append
			add_variable = variables.Add
			for grp in self._options():
				variable = grp['variable']
				stack = grp.get('stack', None)
				for opt in grp['arguments']:
					(name,value,help) = opt[0:3]
					kwargs = opt[3] if len(opt) > 3 else {}
					if name not in variables.keys():
						if help is not None:
							filtered_help.visible_arguments.append(name)
						add_variable(variable(key=name, help=help, default=None if callable(value) else value, **kwargs))
					names = self._names(name, prefix)
					for n in names:
						if n not in variables.keys():
							add_variable(variable(key=n, help=help, default=None, **kwargs))
					if not name in names:
						names.append(name)
					append_known_variable((names, name, value, stack))
					if stack:
						for n in names:
							add_variable(self._generic_variable(key='%s_stop' % n, help=None, default=None))
		def read_variables(self,program,variables,d):
			verbose_settings_init = os.getenv('DXX_SCONS_DEBUG_USER_SETTINGS')
			for (namelist,cname,dvalue,stack) in self.known_variables:
				value = None
				found_value = False
				for n in namelist:
					try:
						v = d[n]
						found_value = True
						if stack:
							if callable(v):
								if verbose_settings_init:
									message(program, 'append to stackable %r from %r by call to %r(%r, %r, %r)' % (cname, n, v, dvalue, value, stack))
								value = v(dvalue=dvalue, value=value, stack=stack)
							else:
								if value:
									value = (value, v)
									if verbose_settings_init:
										message(program, 'append to stackable %r from %r by join of %r.join(%r, %r)' % (cname, n, stack, value))
									value = stack.join(value)
								else:
									if verbose_settings_init:
										message(program, 'assign to stackable %r from %r value %r' % (cname, n, v))
									value = v
							stop = '%s_stop' % n
							if d.get(stop, None):
								if verbose_settings_init:
									message(program, 'terminating search early due to presence of %s' % stop)
								break
							continue
						if verbose_settings_init:
							message(program, 'assign to non-stackable %r from %r value %r' % (cname, n, v))
						value = v
						break
					except KeyError as e:
						pass
				if not found_value:
					if callable(dvalue):
						value = dvalue()
						if verbose_settings_init:
							message(program, 'assign to %r by default value %r from call %r' % (cname, value, dvalue))
					else:
						value = dvalue
						if verbose_settings_init:
							message(program, 'assign to %r by default value %r from direct' % (cname, value))
				setattr(self, cname, value)
			if self.builddir != '' and self.builddir[-1:] != '/':
				self.builddir += '/'
		def clone(self):
			clone = DXXCommon.UserBuildSettings(None)
			for grp in clone._options():
				for o in grp['arguments']:
					name = o[0]
					value = getattr(self, name)
					setattr(clone, name, value)
			return clone
	class UserInstallSettings:
		def _options(self):
			return (
			{
				'variable': self._generic_variable,
				'arguments': (
					('DESTDIR', None, 'installation stage directory'),
					('program_name', None, 'name of built program'),
				),
			},
			{
				'variable': BoolVariable,
				'arguments': (
					('register_install_target', True, 'report install target to SCons core'),
				),
			},
		)
	class UserSettings(UserBuildSettings,UserInstallSettings):
		def _options(self):
			return DXXCommon.UserBuildSettings._options(self) + DXXCommon.UserInstallSettings._options(self)
	# Base class for platform-specific settings processing
	class _PlatformSettings:
		tools = ('g++', 'gnulink')
		ogllibs = []
		platform_objects = ()
		sharepath = None

		def __init__(self,program,user_settings):
			self.__program = program
			self.user_settings = user_settings

		@property
		def builddir(self):
			return self.__program.builddir

		@property
		def env(self):
			return self.__program.env

	# Settings to apply to mingw32 builds
	class Win32PlatformSettings(_PlatformSettings):
		ogllibs = ['opengl32']
		tools = ('mingw',)
		def adjust_environment(self,program,env):
			env.Append(
				CPPDEFINES = ['_WIN32', 'WIN32_LEAN_AND_MEAN'],
				LINKFLAGS = ['-mwindows'],
			)
	class DarwinPlatformSettings(_PlatformSettings):
		# Darwin targets include Objective-C (not Objective-C++) code to
		# access Apple-specific functionality.  Add 'gcc' to the target
		# list to support this.
		#
		# Darwin targets need a special linker, because OS X uses
		# frameworks instead of standard libraries.  Using `gnulink`
		# omits framework-related arguments, causing the linker to skip
		# including required libraries.  SCons's `applelink` target
		# understands these quirks and ensures that framework-related
		# arguments are included.
		tools = ('gcc', 'g++', 'applelink')
		def adjust_environment(self,program,env):
			library_frameworks = os.path.join(os.getenv("HOME"), 'Library/Frameworks')
			env.Append(
				CPPDEFINES = ['__unix__'],
				CPPPATH = [os.path.join(library_frameworks, 'SDL.framework/Headers'), '/Library/Frameworks/SDL.framework/Headers'],
				FRAMEWORKS = ['ApplicationServices', 'Cocoa', 'SDL'],
				FRAMEWORKPATH = [library_frameworks, '/System/Library/Frameworks/ApplicationServices.framework/Versions/A/Frameworks'],
				LINKFLAGS = ['-Wl,-rpath,@loader_path/../Frameworks'],	# Allow libraries & frameworks to go in app bundle
			)
			if self.user_settings.opengl or self.user_settings.opengles:
				env.Append(FRAMEWORKS = ['OpenGL'])
	# Settings to apply to Linux builds
	class LinuxPlatformSettings(_PlatformSettings):
		sharepath = '{prefix}/share/games/{program_target}'.format
		@property
		def ogllibs(self):
			user_settings = self.user_settings
			return [user_settings.opengles_lib, user_settings.egl_lib] if user_settings.opengles else ['GL', 'GLU']
		@staticmethod
		def get_platform_objects(_empty=()):
			return _empty
		def adjust_environment(self,program,env):
			env.Append(
				CXXFLAGS = ['-pthread'],
			)

	def __init__(self,user_settings,__program_instance=itertools.count(1)):
		self.program_instance = next(__program_instance)
		self.user_settings = user_settings

	def create_header_targets(self,__shared_header_file_list=[],__shared_cpp_dict={}):
		fs = SCons.Node.FS.get_default_fs()
		env = self.env
		builddir = self.builddir
		check_header_includes = __shared_cpp_dict.get(builddir)
		if check_header_includes is None:
			check_header_includes = builddir.File('check_header_includes.cpp')
			# Generate the list once, on first use.  Any other targets
			# will reuse it.
			#
			# Touch the file into existence.  It is always empty, but
			# must exist and have an extension of '.cpp'.
			check_header_includes = env.Textfile(target=check_header_includes, source=env.Value('''
/* This file is always empty.  It is only present to act as the source
 * file for SCons targets that test individual headers.
 */
'''))
			__shared_cpp_dict[builddir] = check_header_includes
			# This is ugly, but all other known methods are worse.  The
			# object file needs to depend on the header that created it
			# and recursively depend on headers that contributed to the
			# header that created it.  Adding a dependency using
			# env.Depend creates the first-level dependency, but does
			# not recurse into the header.  Overriding
			# get_found_includes will cause SCons to recurse in the
			# desired way.
			#
			# Calling get_found_includes requires parameters that are
			# not easily obtained here.  There does not appear to be a
			# way to patch the node's dependency list to insert the
			# header other than to override get_found_includes.
			#
			# Newer SCons applied a performance optimization based on
			# using Python __slots__.  Using __slots__ makes it a
			# runtime error to overwrite get_found_includes on the
			# instance, so overwrite the class method instead.  However,
			# some instances of the class may not want this hook, so
			# keep a whitelist of nodes for which the hook is active.
			c = check_header_includes[0].__class__
			# If the attribute is missing, this is the first time that
			# an env.Textfile has been created for this purpose.  Create
			# the attribute so that subsequent passes do not add extra
			# copies of the same hook.
			#
			# Since a flag attribute is needed anyway, make it useful by
			# storing the hook whitelist in it.
			if not hasattr(c, '_dxx_node_header_target_set'):
				c._dxx_node_header_target_set = set()
				def __get_found_includes(node, env, scanner, path):
					# Always call the original and always return at
					# least what it returned.  If this node is in the
					# whitelist, then also apply the hook logic.
					# Otherwise, this is a pass-through.
					r = node.__get_found_includes(env, scanner, path)
					return (r + [fs.File(env['DXX_EFFECTIVE_SOURCE'])]) \
						if node in node._dxx_node_header_target_set else r
				c.__get_found_includes = c.get_found_includes
				c.get_found_includes = __get_found_includes
			# Update the whitelist here, outside the hasattr block.
			# This is necessary so that the hook is created once, but
			# every env.Textfile created by this block is whitelisted.
			c._dxx_node_header_target_set.add(check_header_includes[0])
		if not __shared_header_file_list:
			headers = Git.pcall(['ls-files', '-z', '--', '*.h']).out
			if not headers:
				g = Git.pcall(['--version'], stderr=subprocess.STDOUT)
				raise SCons.Errors.StopError(
					"`git ls-files` failed.  `git --version` failed.  Check that Git is installed." \
						if g.returncode else \
					"`git ls-files` failed, but `git --version` works.  Check that scons is run from a Git repository."
				)
			# Filter out OS X related directories.  Files in those
			# directories assume they are only ever built on OS X, so
			# they unconditionally include headers specific to OS X.
			excluded_directories = (
				'common/arch/cocoa/',
				'common/arch/carbon/',
			)
			__shared_header_file_list.extend([h for h in headers.split('\0') if h and not h.startswith(excluded_directories)])
			if not __shared_header_file_list:
				raise SCons.Errors.StopError("`git ls-files` found headers, but none can be checked.")
		subbuilddir = builddir.Dir(self.srcdir, 'chi')
		Depends = env.Depends
		StaticObject = env.StaticObject
		CPPFLAGS_template = env['CPPFLAGS']
		CPPFLAGS_no_sconf = CPPFLAGS_template + ['-g0', '-include', '$DXX_EFFECTIVE_SOURCE']
		CPPFLAGS_with_sconf = ['-include', 'dxxsconf.h'] + CPPFLAGS_no_sconf
		CXXCOMSTR = env.__header_check_output_COMSTR
		CXXFLAGS = env['CXXFLAGS']
		target = os.path.join('%s/${DXX_EFFECTIVE_SOURCE}%s' % (subbuilddir, env['OBJSUFFIX']))
		for name in __shared_header_file_list:
			if not name:
				continue
			if self.srcdir == 'common' and not name.startswith('common/'):
				# Skip game-specific headers when testing common
				continue
			if self.srcdir[0] == 'd' and name[0] == 'd' and not name.startswith(self.srcdir):
				# Skip d1 in d2 and d2 in d1
				continue
			# Compiler feature headers cannot include dxxsconf.h because
			# it confuses the dependency resolver when SConf runs.
			# Calling code must include dxxsconf.h before including the
			# compiler feature header, so add the inclusion here.
			#
			# For best test coverage, only headers that must avoid
			# including dxxsconf.h receive an implicit include.  Any
			# header which needs dxxsconf.h and can include it without
			# side effects must do so.
			StaticObject(target=target,
				CPPFLAGS=CPPFLAGS_with_sconf if name[:24] == 'common/include/compiler-' else CPPFLAGS_no_sconf,
				CXXCOMSTR=CXXCOMSTR,
				CXXFLAGS=CXXFLAGS,
				DXX_EFFECTIVE_SOURCE=name,
				source=check_header_includes)

	def _cpp_output_StaticObject(self,target=None,source=None,DXX_EFFECTIVE_SOURCE='$SOURCE',*args,**kwargs):
		CPPFLAGS = kwargs.get('CPPFLAGS', None)
		CXXFLAGS = kwargs.get('CXXFLAGS', None)
		env = self.env
		OBJSUFFIX = env['OBJSUFFIX']
		StaticObject = env.__cpp_output_StaticObject
		StaticObject(
			target='%s.i' % (target[:-len(OBJSUFFIX)] if target.endswith(OBJSUFFIX) else target),
			source=source, OBJSUFFIX='.i',
			# Bypass ccache
			CXXCOM=env._dxx_cxxcom_no_prefix,
			CPPFLAGS=(env['CPPFLAGS'] if CPPFLAGS is None else CPPFLAGS),
			CXXFLAGS=(env['CXXFLAGS'] if CXXFLAGS is None else CXXFLAGS) + ['-E'],
			CXXCOMSTR=env.__generate_cpp_output_COMSTR,
			DXX_EFFECTIVE_SOURCE=DXX_EFFECTIVE_SOURCE,
		)
		return StaticObject(target=target, source=source, DXX_EFFECTIVE_SOURCE=DXX_EFFECTIVE_SOURCE, *args, **kwargs)

	def _compilation_database_StaticObject(self,target=None,source=None,*args,**kwargs):
		env = self.env
		StaticObject = env.__compilation_database_StaticObject
		objects = StaticObject(target=target, source=source, *args, **kwargs)
		# Exclude ccache/distcc from the persisted command line.  Store
		# `directory` as the directory of the `SConstruct` file.
		# Calls to `str` are necessary here to coerce SCons.Node objects
		# into strings that `json.dumps` can handle.
		relative_file_path = str(source)
		# clang documentation is silent on whether this must be
		# absolute, but `clang-check` refuses to find files when this is
		# relative.
		directory = env.Dir('.').get_abspath()
		self._compilation_database_entries.extend([
			{
				'command' : env.Override(kwargs).subst(env._dxx_cxxcom_no_prefix, target=[o], source=source),
				'directory' : directory,
				'file' : relative_file_path,
				'output' : str(o),
				}
			for o in objects])
		return objects

	def create_special_target_nodes(self,archive):
		env = self.env
		StaticObject = env.StaticObject
		env._rebirth_nopch_StaticObject = StaticObject
		user_settings = self.user_settings
		if user_settings.register_cpp_output_targets:
			env.__cpp_output_StaticObject = StaticObject
			env.StaticObject = StaticObject = self._cpp_output_StaticObject
		if user_settings.compilation_database:
			env.__compilation_database_StaticObject = StaticObject
			env.StaticObject = self._compilation_database_StaticObject
		if user_settings.check_header_includes:
			# Create header targets before creating the PCHManager, so that
			# create_header_targets() does not call the PCHManager
			# StaticObject hook.
			self.create_header_targets()
		if user_settings.register_runtime_test_link_targets:
			self._register_runtime_test_link_targets()
		configure_pch_flags = archive.configure_pch_flags
		if configure_pch_flags:
			self.pch_manager = PCHManager(self, configure_pch_flags, archive.pch_manager)

	@staticmethod
	def _quote_cppdefine(s,f=repr,b2a_hex=binascii.b2a_hex):
		r = ''
		prior = False
		for c in f(s):
			# No xdigit support in str
			if c in ' ()*+,-./:=[]_' or (c.isalnum() and not (prior and (c.isdigit() or c in 'abcdefABCDEF'))):
				r += c
			elif c == '\n':
				r += r'\n'
			else:
				r += r'\\x%s' % b2a_hex(c.encode()).decode()
				prior = True
				continue
			prior = False
		return '\\"%s\\"' % r

	@staticmethod
	def _encode_cppdefine_for_identifier(user_settings,s,b2a_base64=binascii.b2a_base64):
		extended_identifiers = user_settings._dxx_extended_identifiers
		return '"%s"' % (b2a_base64(s.encode())	\
			.rstrip()	\
			.decode()	\
			.replace('+', extended_identifiers[0])	\
			.replace('/', extended_identifiers[1])	\
			.replace('=', extended_identifiers[2])	\
			)

	def prepare_environment(self):
		# Prettier build messages......
		# Move target to end of C++ source command
		target_string = ' -o $TARGET'
		env = self.env
		user_settings = self.user_settings
		# Expand $CXX immediately.
		# $CCFLAGS is never used.  Remove it.
		cxxcom = env['CXXCOM'] \
			.replace('$CXX ', '%s ' % env['CXX']) \
			.replace('$CCFLAGS ', '')
		if target_string + ' ' in cxxcom:
			cxxcom = '%s%s' % (cxxcom.replace(target_string, ''), target_string)
		env._dxx_cxxcom_no_prefix = cxxcom
		distcc_path = user_settings.distcc
		distcc_cxxcom = ('%s %s' % (distcc_path, cxxcom)) if distcc_path else cxxcom
		env._dxx_cxxcom_no_ccache_prefix = distcc_cxxcom
		ccache_path = user_settings.ccache
		# Add ccache/distcc only for compile, not link
		if ccache_path:
			cxxcom = '%s %s' % (ccache_path, cxxcom)
			if distcc_path is not None:
				penv = self.env['ENV']
				if distcc_path:
					penv['CCACHE_PREFIX'] = distcc_path
				elif distcc_path is not None:
					penv.pop('CCACHE_PREFIX', None)
		elif distcc_path:
			cxxcom = distcc_cxxcom
		# Expand $LINK immediately.
		linkcom = env['LINKCOM'].replace('$LINK ', '%s ' % env['LINK'])
		# Move target to end of link command
		if target_string + ' ' in linkcom:
			linkcom = '%s%s' % (linkcom.replace(target_string, ''), target_string)
		# Add $CXXFLAGS to link command
		cxxflags = '$CXXFLAGS '
		if ' ' + cxxflags not in linkcom:
			linkflags = '$LINKFLAGS'
			linkcom = linkcom.replace(linkflags, cxxflags + linkflags)
		env.Replace(
			CXXCOM = cxxcom,
			LINKCOM = linkcom,
		)
		# Custom DISTCC_HOSTS per target
		distcc_hosts = user_settings.distcc_hosts
		if distcc_hosts is not None:
			env['ENV']['DISTCC_HOSTS'] = distcc_hosts
		if user_settings.verbosebuild:
			env.__header_check_output_COMSTR	= None
			env.__generate_cpp_output_COMSTR	= None
		else:
			target = self.target[:3]
			format_tuple = (target, user_settings.builddir or '.')
			env.__header_check_output_COMSTR	= "CHK %s %s $DXX_EFFECTIVE_SOURCE" % format_tuple
			env.__generate_cpp_output_COMSTR	= "CPP %s %s $DXX_EFFECTIVE_SOURCE" % format_tuple
			env.Replace(
				CXXCOMSTR						= "CXX %s %s $SOURCE" % format_tuple,
			# `builddir` is implicit since $TARGET is the full path to
			# the output
				LINKCOMSTR						= "LD  %s $TARGET" % target,
				RCCOMSTR						= "RC  %s %s $SOURCE" % format_tuple,
			)

		Werror = get_Werror_string(user_settings.CXXFLAGS)
		env.Prepend(CXXFLAGS = [
			'-ftabstop=4',
			'-Wall',
			Werror + 'extra',
			Werror + 'format=2',
			Werror + 'missing-braces',
			Werror + 'missing-include-dirs',
			Werror + 'uninitialized',
			Werror + 'undef',
			Werror + 'pointer-arith',
			Werror + 'cast-qual',
			Werror + 'missing-declarations',
			Werror + 'redundant-decls',
			Werror + 'vla',
		])
		env.Append(
			CXXFLAGS = ['-funsigned-char'],
			CPPPATH = ['common/include', 'common/main', '.'],
			CPPFLAGS = SCons.Util.CLVar('-Wno-sign-compare'),
			# PhysFS 2.1 and later deprecate functions PHYSFS_read,
			# PHYSFS_write, which Rebirth uses extensively.  PhysFS 2.0
			# does not implement the new non-deprecated functions.
			# Disable the deprecation error until PhysFS 2.0 support is
			# removed.
			CPPDEFINES = [('PHYSFS_DEPRECATED', '')],
		)
		add_flags = defaultdict(list)
		if user_settings.builddir:
			add_flags['CPPPATH'].append(user_settings.builddir)
		if user_settings.editor:
			add_flags['CPPPATH'].append('common/include/editor')
		CLVar = SCons.Util.CLVar
		for flags in ('CPPFLAGS', 'CXXFLAGS', 'LIBS', 'LINKFLAGS'):
			value = getattr(self.user_settings, flags)
			if value is not None:
				add_flags[flags] = CLVar(value)
		env.Append(**add_flags)
		if self.user_settings.lto:
			env.Append(CXXFLAGS = [
				# clang does not support =N syntax
				('-flto=%s' % self.user_settings.lto) if self.user_settings.lto > 1 else '-flto',
			])

	@cached_property
	def platform_settings(self):
		# windows or *nix?
		platform_name = self.user_settings.host_platform
		try:
			machine = os.uname()[4]
		except AttributeError:
			machine = None
		message(self, "compiling on %r/%r for %r into %s%s" % (sys.platform, machine, platform_name, self.user_settings.builddir or '.',
			(' with prefix list %s' % str(self._argument_prefix_list)) if self._argument_prefix_list else ''))
		return self.get_platform_settings_type(platform_name)(self, self.user_settings)

	@classmethod
	def get_platform_settings_type(cls,platform_name):
		# By happy accident, LinuxPlatformSettings produces the desired
		# result on OpenBSD, so there is no need for specific handling
		# of `platform_name == 'openbsd'`.
		return (
			cls.Win32PlatformSettings if platform_name == 'win32' else (
				cls.DarwinPlatformSettings if platform_name == 'darwin' else
				cls.LinuxPlatformSettings
			)
		)

	@cached_property
	def env(self):
		platform_settings = self.platform_settings
		# Acquire environment object...
		user_settings = self.user_settings
		# Get traditional compiler environment variables
		kw = {}
		chost_aware_tools = ('CXX', 'RC')
		for cc in chost_aware_tools:
			value = getattr(user_settings, cc)
			if value is not None:
				kw[cc] = value
		tools = platform_settings.tools + ('textfile',)
		env = Environment(ENV = os.environ, tools = tools, **kw)
		CHOST = user_settings.CHOST
		if CHOST:
			denv = None
			for cc in chost_aware_tools:
				value = kw.get(cc)
				if value is not None:
					# If the user set a value, that value is always
					# used.
					continue
				if denv is None:
					# Lazy load denv.
					denv = Environment(tools = tools)
				# If the option in the base environment, ignoring both
				# user_settings and the process environment, matches the
				# option in the customized environment, then assume that
				# this is an SCons default, not a user-chosen value.
				value = denv.get(cc)
				if value and env.get(cc) == value:
					env[cc] = '{}-{}'.format(CHOST, value)
		platform_settings.adjust_environment(self, env)
		return env

	def process_user_settings(self):
		env = self.env
		user_settings = self.user_settings
		compilation_database = self.user_settings.compilation_database
		if compilation_database:
			# Only set self._compilation_database_entries if collection
			# of the compilation database is enabled.
			try:
				compilation_database_entries = self.compilation_database_dict_fn_to_entries[compilation_database][1]
			except KeyError:
				compilation_database_entries = []
				self.compilation_database_dict_fn_to_entries[compilation_database] = (env, compilation_database_entries)
			self._compilation_database_entries = compilation_database_entries

		# Insert default CXXFLAGS.  User-specified CXXFLAGS, if any, are
		# appended to this list and will override these defaults.  The
		# defaults are present to ensure that a user who does not set
		# any options gets a good default experience.
		env.Prepend(CXXFLAGS = ['-g', '-O2'])
		# Raspberry Pi?
		if user_settings.raspberrypi == 'yes':
			rpi_vc_path = user_settings.rpi_vc_path
			message(self, "Raspberry Pi: using VideoCore libs in %r" % rpi_vc_path)
			env.Append(
				CPPDEFINES = ['RPI'],
			# use CPPFLAGS -isystem instead of CPPPATH because these those header files
			# are not very clean and would trigger some warnings we usually consider as
			# errors. Using them as system headers will make gcc ignoring any warnings.
				CPPFLAGS = [
				'-isystem=%s/include' % rpi_vc_path,
				'-isystem=%s/include/interface/vcos/pthreads' % rpi_vc_path,
				'-isystem=%s/include/interface/vmcs_host/linux' % rpi_vc_path,
			],
				LIBPATH = '%s/lib' % rpi_vc_path,
				LIBS = ['bcm_host'],
			)

	def _register_runtime_test_link_targets(self):
		runtime_test_boost_tests = self.runtime_test_boost_tests
		if not runtime_test_boost_tests:
			return
		env = self.env
		user_settings = self.user_settings
		builddir = env.Dir(user_settings.builddir).Dir(self.srcdir)
		for test in runtime_test_boost_tests:
			LIBS = [] if test.nodefaultlibs else env['LIBS'][:]
			LIBS.append('boost_unit_test_framework')
			env.Program(target=builddir.File(test.target), source=test.source(self), LIBS=LIBS)

class DXXArchive(DXXCommon):
	PROGRAM_NAME = 'DXX-Archive'
	_argument_prefix_list = None
	srcdir = 'common'
	target = 'dxx-common'
	RuntimeTest = DXXCommon.RuntimeTest
	runtime_test_boost_tests = (
		RuntimeTest('test-valptridx-range', (
			'common/unittest/valptridx-range.cpp',
			))
			,)
	del RuntimeTest

	def get_objects_common(self,
		__get_objects_common=DXXCommon.create_lazy_object_getter((
'common/2d/2dsline.cpp',
'common/2d/bitblt.cpp',
'common/2d/bitmap.cpp',
'common/2d/box.cpp',
'common/2d/canvas.cpp',
'common/2d/circle.cpp',
'common/2d/disc.cpp',
'common/2d/gpixel.cpp',
'common/2d/line.cpp',
'common/2d/pixel.cpp',
'common/2d/rect.cpp',
'common/2d/rle.cpp',
'common/2d/scalec.cpp',
'common/3d/draw.cpp',
'common/3d/globvars.cpp',
'common/3d/instance.cpp',
'common/3d/matrix.cpp',
'common/3d/points.cpp',
'common/3d/rod.cpp',
'common/3d/setup.cpp',
'common/arch/sdl/event.cpp',
'common/arch/sdl/joy.cpp',
'common/arch/sdl/key.cpp',
'common/arch/sdl/mouse.cpp',
'common/arch/sdl/timer.cpp',
'common/arch/sdl/window.cpp',
'common/main/cli.cpp',
'common/main/cmd.cpp',
'common/main/cvar.cpp',
'common/maths/fixc.cpp',
'common/maths/rand.cpp',
'common/maths/tables.cpp',
'common/maths/vecmat.cpp',
'common/mem/mem.cpp',
'common/misc/error.cpp',
'common/misc/hash.cpp',
'common/misc/hmp.cpp',
'common/misc/ignorecase.cpp',
'common/misc/strutil.cpp',
'common/misc/vgrphys.cpp',
'common/misc/vgwphys.cpp',
)), \
		__get_objects_use_adlmidi=DXXCommon.create_lazy_object_getter((
'common/music/adlmidi_dynamic.cpp',
)),
		__get_objects_use_sdl1=DXXCommon.create_lazy_object_getter((
'common/arch/sdl/rbaudio.cpp',
))
		):
		value = list(__get_objects_common(self))
		extend = value.extend
		user_settings = self.user_settings
		if user_settings._enable_adlmidi():
			extend(__get_objects_use_adlmidi(self))
		if not user_settings.sdl2:
			extend(__get_objects_use_sdl1(self))
		extend(self.platform_settings.get_platform_objects())
		return value

	get_objects_editor = DXXCommon.create_lazy_object_getter((
'common/editor/autosave.cpp',
'common/editor/func.cpp',
'common/ui/button.cpp',
'common/ui/checkbox.cpp',
'common/ui/dialog.cpp',
'common/ui/file.cpp',
'common/ui/gadget.cpp',
'common/ui/icon.cpp',
'common/ui/inputbox.cpp',
'common/ui/keypad.cpp',
'common/ui/keypress.cpp',
'common/ui/listbox.cpp',
'common/ui/menu.cpp',
'common/ui/menubar.cpp',
'common/ui/message.cpp',
'common/ui/radio.cpp',
'common/ui/scroll.cpp',
'common/ui/ui.cpp',
'common/ui/uidraw.cpp',
'common/ui/userbox.cpp',
))
	# for non-ogl
	get_objects_arch_sdl = DXXCommon.create_lazy_object_getter((
'common/3d/clipper.cpp',
'common/texmap/ntmap.cpp',
'common/texmap/scanline.cpp',
'common/texmap/tmapflat.cpp',
))
	# for ogl
	get_objects_arch_ogl = DXXCommon.create_lazy_object_getter((
'common/arch/ogl/ogl_extensions.cpp',
'common/arch/ogl/ogl_sync.cpp',
))
	get_objects_arch_sdlmixer = DXXCommon.create_lazy_object_getter((
'common/arch/sdl/digi_mixer_music.cpp',
))
	class Win32PlatformSettings(DXXCommon.Win32PlatformSettings):
		get_platform_objects = LazyObjectConstructor.create_lazy_object_getter((
'common/arch/win32/except.cpp',
'common/arch/win32/messagebox.cpp',
))
	class DarwinPlatformSettings(DXXCommon.DarwinPlatformSettings):
		get_platform_objects = LazyObjectConstructor.create_lazy_object_getter((
			'common/arch/cocoa/messagebox.mm',
			'common/arch/cocoa/SDLMain.m',
		))

	def __init__(self,user_settings):
		user_settings = user_settings.clone()
		DXXCommon.__init__(self, user_settings)
		if not user_settings.register_compile_target:
			return
		self.prepare_environment()
		self.process_user_settings()
		self.configure_environment()
		self.create_special_target_nodes(self)
		ToolchainInformation.show_partial_environ(self.env, user_settings, lambda s, _message=message, _self=self: _message(self, s))

	def configure_environment(self):
		fs = SCons.Node.FS.get_default_fs()
		user_settings = self.user_settings
		builddir = user_settings.builddir or '.'
		try:
			builddir = fs.Dir(builddir)
		except TypeError as e:
			raise SCons.Errors.StopError(e.args[0])
		tests = ConfigureTests(self.program_message_prefix, user_settings, self.platform_settings)
		log_file = builddir.File('sconf.log')
		env = self.env
		conf = env.Configure(custom_tests = {
				k.name:getattr(tests, k.name) for k in tests.custom_tests
			},
			conf_dir=fs.Dir('.sconf_temp', builddir),
			log_file=log_file,
			config_h=fs.File('dxxsconf.h', builddir),
			clean=False,
			help=False
		)
		self.configure_added_environment_flags = tests.successful_flags
		self.configure_pch_flags = None
		if not conf.env:
			return
		cc_env_strings = tests.ForceVerboseLog(conf.env)
		try:
			for k in tests.custom_tests:
				getattr(conf, k.name)()
		except SCons.Errors.StopError as e:
			raise SCons.Errors.StopError('{e0}  See {log_file} for details.'.format(e0=e.args[0], log_file=log_file), *e.args[1:])
		cc_env_strings.restore(conf.env)
		if user_settings.pch:
			conf.Define('DXX_VERSION_SEQ', self.DXX_VERSION_SEQ)
		if user_settings.record_sconf_results:
			conf.config_h_text += '''
/*
%s
 */
''' % '\n'.join(['check_%s=%s' % (n,v) for n,v in tests._sconf_results])
		conf.Finish()
		self.configure_pch_flags = tests.pch_flags
		add_flags = self.configure_added_environment_flags
		CLVar = SCons.Util.CLVar
		for flags in ('CPPFLAGS', 'CXXFLAGS', 'LINKFLAGS'):
			value = getattr(user_settings, '%s_unchecked' % flags)
			if value:
				add_flags[flags] += CLVar(value)
		# Wrapping PHYSFS_read / PHYSFS_write is only useful when
		# Valgrind poisoning is enabled.  If Valgrind poisoning is not
		# enabled, the wrappers are not built (unless the appropriate
		# preprocessor define is added to $CPPFLAGS by the user).  The
		# link will fail if wrapping is enabled, Valgrind poisoning is
		# disabled, and the preprocessor define is not set.
		#
		# Only $LINKFLAGS are set here.  The preprocessor define is only
		# relevant to 2 source files, both of which delegate it to
		# header common/misc/vg-wrap-physfs.h, so omit it from the
		# general options to avoid unnecessary rebuilds of other source
		# files.
		if user_settings.wrap_PHYSFS_read:
			add_flags['LINKFLAGS'].extend((
					'-Wl,--wrap,PHYSFS_read',
					'-Wl,--wrap,PHYSFS_readSBE16',
					'-Wl,--wrap,PHYSFS_readSBE32',
					'-Wl,--wrap,PHYSFS_readSLE16',
					'-Wl,--wrap,PHYSFS_readSLE32',
					))
		if user_settings.wrap_PHYSFS_write:
			add_flags['LINKFLAGS'].extend((
					'-Wl,--wrap,PHYSFS_write',
					'-Wl,--wrap,PHYSFS_writeSBE16',
					'-Wl,--wrap,PHYSFS_writeSBE32',
					'-Wl,--wrap,PHYSFS_writeSLE16',
					'-Wl,--wrap,PHYSFS_writeSLE32',
					'-Wl,--wrap,PHYSFS_writeULE16',
					'-Wl,--wrap,PHYSFS_writeULE32',
					))
		env.MergeFlags(add_flags)

class DXXProgram(DXXCommon):
	LazyObjectState = DXXCommon.LazyObjectState
	def _generate_kconfig_ui_table(program,env,source,target,kconfig_static_object):
			builddir = program.builddir.Dir(program.target)
			kwargs = {}
			# Bypass ccache, if any, since this is a preprocess only
			# call.
			kwargs['CXXFLAGS'] = (env['CXXFLAGS'] or []) + ['-E']
			cpp_kconfig_udlr = env._rebirth_nopch_StaticObject(target=str(target)[:-1] + 'ui-table.i', source=source[:-3] + 'ui-table.cpp', CXXCOM=env._dxx_cxxcom_no_ccache_prefix, **kwargs)
			generated_udlr_header = builddir.File('kconfig.udlr.h')
			generate_kconfig_udlr = env.File('similar/main/generate-kconfig-udlr.py')
			env.Command(generated_udlr_header, [cpp_kconfig_udlr, generate_kconfig_udlr], [[sys.executable, generate_kconfig_udlr, '$SOURCE', '$TARGET']])
			env.Depends(kconfig_static_object, generated_udlr_header)

	static_archive_construction = {}
	def _apply_target_name(self,name):
		return os.path.join(os.path.dirname(name), '.%s.%s' % (self.target, os.path.splitext(os.path.basename(name))[0]))
	def _apply_env_version_seq(self,env,_empty={}):
		return _empty if self.user_settings.pch else {'CPPDEFINES' : env['CPPDEFINES'] + [('DXX_VERSION_SEQ', self.DXX_VERSION_SEQ)]}
	get_objects_similar_arch_ogl = DXXCommon.create_lazy_object_states_getter((LazyObjectState(sources=(
'similar/arch/ogl/gr.cpp',
'similar/arch/ogl/ogl.cpp',
),
		transform_target=_apply_target_name,
	),
	))
	get_objects_similar_arch_sdl = DXXCommon.create_lazy_object_states_getter((LazyObjectState(sources=(
'similar/arch/sdl/gr.cpp',
),
		transform_target=_apply_target_name,
	),
	))
	get_objects_similar_arch_sdlmixer = DXXCommon.create_lazy_object_states_getter((LazyObjectState(sources=(
'similar/arch/sdl/digi_mixer.cpp',
'similar/arch/sdl/jukebox.cpp',
),
		transform_target=_apply_target_name,
	),
	))
	__get_objects_common = DXXCommon.create_lazy_object_states_getter((LazyObjectState(sources=(
'similar/2d/font.cpp',
'similar/2d/palette.cpp',
'similar/2d/pcx.cpp',
'similar/3d/interp.cpp',
'similar/arch/sdl/digi.cpp',
'similar/arch/sdl/digi_audio.cpp',
'similar/arch/sdl/init.cpp',
'similar/main/ai.cpp',
'similar/main/aipath.cpp',
'similar/main/automap.cpp',
'similar/main/bm.cpp',
'similar/main/cntrlcen.cpp',
'similar/main/collide.cpp',
'similar/main/config.cpp',
'similar/main/console.cpp',
'similar/main/controls.cpp',
'similar/main/credits.cpp',
'similar/main/digiobj.cpp',
'similar/main/effects.cpp',
'similar/main/endlevel.cpp',
'similar/main/fireball.cpp',
'similar/main/fuelcen.cpp',
'similar/main/fvi.cpp',
'similar/main/game.cpp',
'similar/main/gamecntl.cpp',
'similar/main/gamefont.cpp',
'similar/main/gamemine.cpp',
'similar/main/gamerend.cpp',
'similar/main/gamesave.cpp',
'similar/main/gameseg.cpp',
'similar/main/gameseq.cpp',
'similar/main/gauges.cpp',
'similar/main/hostage.cpp',
'similar/main/hud.cpp',
'similar/main/iff.cpp',
'similar/main/kmatrix.cpp',
'similar/main/laser.cpp',
'similar/main/lighting.cpp',
'similar/main/menu.cpp',
'similar/main/mglobal.cpp',
'similar/main/mission.cpp',
'similar/main/morph.cpp',
'similar/main/multi.cpp',
'similar/main/multibot.cpp',
'similar/main/newdemo.cpp',
'similar/main/newmenu.cpp',
'similar/main/object.cpp',
'similar/main/paging.cpp',
'similar/main/physics.cpp',
'similar/main/piggy.cpp',
'similar/main/player.cpp',
'similar/main/polyobj.cpp',
'similar/main/powerup.cpp',
'similar/main/render.cpp',
'similar/main/robot.cpp',
'similar/main/scores.cpp',
'similar/main/segment.cpp',
'similar/main/slew.cpp',
'similar/main/songs.cpp',
'similar/main/state.cpp',
'similar/main/switch.cpp',
'similar/main/terrain.cpp',
'similar/main/texmerge.cpp',
'similar/main/text.cpp',
'similar/main/titles.cpp',
'similar/main/vclip.cpp',
'similar/main/wall.cpp',
'similar/main/weapon.cpp',
'similar/misc/args.cpp',
),
		transform_target=_apply_target_name,
	), LazyObjectState(sources=(
'similar/main/inferno.cpp',
),
		transform_env = (lambda self, env: {'CPPDEFINES' : env['CPPDEFINES'] + env.__dxx_CPPDEFINE_SHAREPATH + env.__dxx_CPPDEFINE_git_version}),
		transform_target=_apply_target_name,
	), LazyObjectState(sources=(
'similar/main/kconfig.cpp',
),
		StaticObject_hook=_generate_kconfig_ui_table,
		transform_target=_apply_target_name,
	), LazyObjectState(sources=(
'similar/misc/physfsx.cpp',
),
		transform_env = (lambda self, env: {'CPPDEFINES' : env['CPPDEFINES'] + env.__dxx_CPPDEFINE_SHAREPATH}),
		transform_target=_apply_target_name,
	), LazyObjectState(sources=(
'similar/main/playsave.cpp',
),
		transform_env=_apply_env_version_seq,
		transform_target=_apply_target_name,
	),
	))
	get_objects_editor = DXXCommon.create_lazy_object_states_getter((LazyObjectState(sources=(
'similar/editor/centers.cpp',
'similar/editor/curves.cpp',
'similar/main/dumpmine.cpp',
'similar/editor/eglobal.cpp',
'similar/editor/elight.cpp',
'similar/editor/eobject.cpp',
'similar/editor/eswitch.cpp',
'similar/editor/group.cpp',
'similar/editor/info.cpp',
'similar/editor/kbuild.cpp',
'similar/editor/kcurve.cpp',
'similar/editor/kfuncs.cpp',
'similar/editor/kgame.cpp',
'similar/editor/khelp.cpp',
'similar/editor/kmine.cpp',
'similar/editor/ksegmove.cpp',
'similar/editor/ksegsel.cpp',
'similar/editor/ksegsize.cpp',
'similar/editor/ktmap.cpp',
'similar/editor/kview.cpp',
'similar/editor/med.cpp',
'similar/editor/meddraw.cpp',
'similar/editor/medmisc.cpp',
'similar/editor/medrobot.cpp',
'similar/editor/medsel.cpp',
'similar/editor/medwall.cpp',
'similar/editor/mine.cpp',
'similar/editor/objpage.cpp',
'similar/editor/segment.cpp',
'similar/editor/seguvs.cpp',
'similar/editor/texpage.cpp',
'similar/editor/texture.cpp',
),
		transform_target=_apply_target_name,
	),
	))

	class UserSettings(DXXCommon.UserSettings):
		@property
		def BIN_DIR(self):
			# installation path
			return '%s/bin' % self.prefix
	# Settings to apply to mingw32 builds
	class Win32PlatformSettings(DXXCommon.Win32PlatformSettings):
		def __init__(self,program,user_settings):
			DXXCommon.Win32PlatformSettings.__init__(self,program,user_settings)
		def adjust_environment(self,program,env):
			DXXCommon.Win32PlatformSettings.adjust_environment(self, program, env)
			rcdir = 'similar/arch/win32'
			j = os.path.join
			resfile = env.RES(target=j(program.user_settings.builddir, rcdir, '%s.res%s' % (program.target, env["OBJSUFFIX"])), source=j(rcdir, 'dxx-rebirth.rc'))
			Depends = env.Depends
			File = env.File
			Depends(resfile, File(j(rcdir, 'dxx-rebirth.manifest')))
			Depends(resfile, File(j(rcdir, '%s.ico' % program.target)))
			self.platform_objects = [resfile]
			env.Prepend(
				CXXFLAGS = ['-fno-omit-frame-pointer'],
				RCFLAGS = ['-D%s' % d for d in program.env_CPPDEFINES],
			)
			env.Append(
				LIBS = ['glu32', 'wsock32', 'ws2_32', 'winmm', 'mingw32', 'SDLmain', 'SDL'],
			)
	# Settings to apply to Apple builds
	class DarwinPlatformSettings(DXXCommon.DarwinPlatformSettings):
		def __init__(self,program,user_settings):
			DXXCommon.DarwinPlatformSettings.__init__(self,program,user_settings)
		def adjust_environment(self,program,env):
			DXXCommon.DarwinPlatformSettings.adjust_environment(self, program, env)
			VERSION = '%s.%s' % (program.VERSION_MAJOR, program.VERSION_MINOR)
			if (program.VERSION_MICRO):
				VERSION += '.%s' % program.VERSION_MICRO
			env.Replace(
				VERSION_NUM = VERSION,
				VERSION_NAME = '%s v%s' % (program.PROGRAM_NAME, VERSION),
			)
	# Settings to apply to Linux builds
	class LinuxPlatformSettings(DXXCommon.LinuxPlatformSettings):
		def __init__(self,program,user_settings):
			DXXCommon.LinuxPlatformSettings.__init__(self,program,user_settings)
			if user_settings.sharepath and user_settings.sharepath[-1] != '/':
				user_settings.sharepath += '/'
		def adjust_environment(self,program,env):
			DXXCommon.LinuxPlatformSettings.adjust_environment(self,program,env)
			user_settings = self.user_settings
			if user_settings.need_dynamic_library_load():
				env.Append(LIBS = ['dl'])

	def get_objects_common(self,
		__get_objects_common=__get_objects_common,
		__get_objects_use_udp=DXXCommon.create_lazy_object_states_getter((LazyObjectState(sources=(
'similar/main/net_udp.cpp',
),
		transform_env= _apply_env_version_seq,
		transform_target=_apply_target_name,
	),
	))
		):
		value = list(__get_objects_common(self))
		extend = value.extend
		if self.user_settings.use_udp:
			extend(__get_objects_use_udp(self))
		extend(self.platform_settings.platform_objects)
		return value

	def __init__(self,prefix,variables,filtered_help):
		self.variables = variables
		self._argument_prefix_list = prefix
		user_settings = self.UserSettings(program=self)
		DXXCommon.__init__(self, user_settings)
		git_describe_version = Git.compute_extra_version().describe
		extra_version = 'v%s.%s.%s' % (self.VERSION_MAJOR, self.VERSION_MINOR, self.VERSION_MICRO)
		if git_describe_version and not (extra_version == git_describe_version or extra_version[1:] == git_describe_version):
			extra_version += ' ' + git_describe_version
		print('===== %s %s =====' % (self.PROGRAM_NAME, extra_version))
		user_settings.register_variables(prefix, variables, filtered_help)

	def init(self,substenv):
		user_settings = self.user_settings
		user_settings.read_variables(self, self.variables, substenv)
		archive = DXXProgram.static_archive_construction.get(user_settings.builddir, None)
		if archive is None:
			DXXProgram.static_archive_construction[user_settings.builddir] = archive = DXXArchive(user_settings)
		if user_settings.register_compile_target:
			self.prepare_environment(archive)
			self.process_user_settings()
		self.register_program()
		if user_settings.enable_build_failure_summary:
			self._register_build_failure_hook(archive)
		return self.variables.GenerateHelpText(self.env)

	def prepare_environment(self,archive):
		DXXCommon.prepare_environment(self)
		env = self.env
		env.MergeFlags(archive.configure_added_environment_flags)
		self.create_special_target_nodes(archive)
		sharepath = self.user_settings.sharepath
		# Must use [] here, not (), since it is concatenated with other
		# lists.
		env.__dxx_CPPDEFINE_SHAREPATH = [('DXX_SHAREPATH', self._quote_cppdefine(sharepath, f=str))] if sharepath else []
		message(self, "default sharepath is %r" % (sharepath or None))
		env.Append(
			CPPDEFINES = [
				self.env_CPPDEFINES,
		# For PRIi64
				('__STDC_FORMAT_MACROS',),
				# Every file that sees `GameArg` must know whether a
				# sharepath exists.  Most files do not need to know the
				# value of sharepath.  Pass only its existence, so that
				# changing the sharepath does not needlessly rebuild
				# those files.
				('DXX_USE_SHAREPATH', int(not not sharepath)),
			],
			CPPPATH = [os.path.join(self.srcdir, 'main')],
			LIBS = ['m'],
		)

	def register_program(self):
		user_settings = self.user_settings
		exe_target = user_settings.program_name
		if not exe_target:
			exe_target = os.path.join(self.srcdir, self.target)
			if user_settings.editor:
				exe_target += '-editor'
		env = self.env
		PROGSUFFIX = env['PROGSUFFIX']
		if PROGSUFFIX and not exe_target.endswith(PROGSUFFIX):
			exe_target += PROGSUFFIX
		exe_target = self.builddir.File(exe_target)
		if user_settings.register_compile_target:
			exe_target = self._register_program(exe_target)
			ToolchainInformation.show_partial_environ(env, user_settings, lambda s, _message=message, _self=self: _message(self, s))
		if user_settings.register_install_target:
			self._register_install(self.shortname, exe_target)

	def _register_program(self,exe_target):
		env = self.env
		user_settings = self.user_settings
		static_archive_construction = self.static_archive_construction[user_settings.builddir]
		objects = static_archive_construction.get_objects_common()
		git_describe_version = Git.compute_extra_version() if user_settings.git_describe_version else Git.UnknownExtraVersion
		env.__dxx_CPPDEFINE_git_version = [('DXX_git_commit', git_describe_version.revparse_HEAD), ('DXX_git_describe', self._encode_cppdefine_for_identifier(user_settings,git_describe_version.describe))]
		objects.extend(self.get_objects_common())
		if user_settings.sdlmixer:
			objects.extend(static_archive_construction.get_objects_arch_sdlmixer())
			objects.extend(self.get_objects_similar_arch_sdlmixer())
		if user_settings.opengl or user_settings.opengles:
			env.Append(LIBS = self.platform_settings.ogllibs)
			static_objects_arch = static_archive_construction.get_objects_arch_ogl
			objects_similar_arch = self.get_objects_similar_arch_ogl
		else:
			static_objects_arch = static_archive_construction.get_objects_arch_sdl
			objects_similar_arch = self.get_objects_similar_arch_sdl
		objects.extend(static_objects_arch())
		objects.extend(objects_similar_arch())
		if user_settings.editor:
			objects.extend(self.get_objects_editor())
			objects.extend(static_archive_construction.get_objects_editor())
		versid_build_environ = ['CXX', 'CPPFLAGS', 'CXXFLAGS', 'LINKFLAGS']
		versid_cppdefines = env['CPPDEFINES'][:]
		extra_version = user_settings.extra_version
		if extra_version is None:
			extra_version = 'v%u.%u' % (self.VERSION_MAJOR, self.VERSION_MINOR)
			if self.VERSION_MICRO:
				extra_version += '.%u' % self.VERSION_MICRO
		git_describe_version_describe_output = git_describe_version.describe
		if git_describe_version_describe_output and not (extra_version and (extra_version == git_describe_version_describe_output or (extra_version[0] == 'v' and extra_version[1:] == git_describe_version_describe_output))):
			# Suppress duplicate output
			if extra_version:
				extra_version += ' '
			extra_version += git_describe_version_describe_output
		get_version_head = StaticSubprocess.get_version_head
		ld_path = ToolchainInformation.get_tool_path(env, 'ld')[1]
		_quote_cppdefine = self._quote_cppdefine
		versid_cppdefines.extend([('DESCENT_%s' % k, _quote_cppdefine(env.get(k, ''))) for k in versid_build_environ])
		versid_cppdefines.extend((
			# VERSION_EXTRA is special.  Format it as a string so that
			# it can be pasted into g_descent_version (in vers_id.cpp)
			# and look normal when printed as part of the startup
			# banner.  Since it is pasted into g_descent_version, it is
			# NOT included in versid_build_environ as an independent
			# field.
			('DESCENT_VERSION_EXTRA', _quote_cppdefine(extra_version, f=str)),
			('DESCENT_CXX_version', _quote_cppdefine(get_version_head(env['CXX']))),
			('DESCENT_LINK', _quote_cppdefine(ld_path)),
			('DESCENT_git_status', _quote_cppdefine(git_describe_version.status)),
			('DESCENT_git_diffstat', _quote_cppdefine(git_describe_version.diffstat_HEAD)),
		))
		if ld_path:
			versid_cppdefines.append(
				('DESCENT_LINK_version', _quote_cppdefine(get_version_head(ld_path))),
			)
			versid_build_environ.append('LINK_version')
		versid_build_environ.extend((
			'CXX_version',
			'LINK',
			'git_status',
			'git_diffstat',
		))
		versid_cppdefines.append(('DXX_RBE"(A)"', '"%s"' % ''.join(['A(%s)' % k for k in versid_build_environ])))
		versid_environ = self.env['ENV'].copy()
		# Direct mode conflicts with __TIME__
		versid_environ['CCACHE_NODIRECT'] = 1
		versid_cpp = 'similar/main/vers_id.cpp'
		versid_obj = env.StaticObject(target='%s%s%s' % (user_settings.builddir, self._apply_target_name(versid_cpp), self.env["OBJSUFFIX"]), source=versid_cpp, CPPDEFINES=versid_cppdefines, ENV=versid_environ)
		Depends = env.Depends
		# If $SOURCE_DATE_EPOCH is set, add its value as a shadow
		# dependency to ensure that vers_id.cpp is rebuilt if
		# $SOURCE_DATE_EPOCH on this run differs from $SOURCE_DATE_EPOCH
		# on last run.  If it is unset, use None for this test, so that
		# unset differs from all valid values.  Using a fixed value for
		# unset means that vers_id.cpp will not be rebuilt for this
		# dependency if $SOURCE_DATE_EPOCH was previously unset and is
		# currently unset, regardless of when it was most recently
		# built, but vers_id.cpp will be rebuilt if the user changes
		# $SOURCE_DATE_EPOCH and reruns scons.
		#
		# The process environment is not modified, so the default None
		# is never seen by tools that would reject it.
		Depends(versid_obj, env.Value(os.getenv('SOURCE_DATE_EPOCH')))
		if user_settings.versid_depend_all:
			# Optional fake dependency to force vers_id to rebuild so
			# that it picks up the latest timestamp.
			Depends(versid_obj, objects)
		objects.append(versid_obj)
		# finally building program...
		return env.Program(target=exe_target, source = objects)

	def _show_build_failure_summary():
		from SCons.Script import GetBuildFailures
		build_failures = GetBuildFailures()
		if not build_failures:
			return
		node = []
		command = []
		total = 0
		for f in build_failures:
			if not f:
				continue
			e = f.executor
			if not e:
				continue
			total = total + 1
			e = e.get_build_env()
			try:
				e.__show_build_failure_summary
			except AttributeError:
				continue
			node.append('\t%s\n' % f.node)
			# Sacrifice some precision so that the printed output is
			# valid shell input.
			c = f.command
			command.append('\n %s' % (' '.join(c) if isinstance(c, list) else c))
		if not total:
			return
		print("Failed target count: total=%u; targets with enable_build_failure_summary=1: %u" % (total, len(node)))
		if node:
			print('Failed node list:\n%sFailed command list:%s' % (''.join(node), ''.join(command)))

	def _register_build_failure_hook(self,archive,show_build_failure_summary=[_show_build_failure_summary]):
		# Always mark the environment as report-enabled.
		# Only register the atexit hook once.
		env = self.env
		env.__show_build_failure_summary = None
		archive.env.__show_build_failure_summary = None
		if not show_build_failure_summary:
			return
		from atexit import register
		register(show_build_failure_summary.pop())

	def _register_install(self,dxxstr,exe_node):
		env = self.env
		if self.user_settings.host_platform != 'darwin':
				install_dir = '%s%s' % (self.user_settings.DESTDIR or '', self.user_settings.BIN_DIR)
				env.Install(install_dir, exe_node)
				env.Alias('install', install_dir)
		else:
			syspath = sys.path[:]
			cocoa = 'common/arch/cocoa'
			sys.path += [cocoa]
			import tool_bundle
			sys.path = syspath
			tool_bundle.TOOL_BUNDLE(env)
			env.MakeBundle(os.path.join(self.user_settings.builddir, '%s.app' % self.PROGRAM_NAME), exe_node,
					'free.%s-rebirth' % dxxstr, os.path.join(cocoa, 'Info.plist'),
					typecode='APPL', creator='DCNT',
					icon_file=os.path.join(cocoa, '%s-rebirth.icns' % dxxstr),
					resources=[[os.path.join(self.srcdir, s), s] for s in ['English.lproj/InfoPlist.strings']])

class D1XProgram(DXXProgram):
	LazyObjectState = DXXProgram.LazyObjectState
	PROGRAM_NAME = 'D1X-Rebirth'
	target = \
	srcdir = 'd1x-rebirth'
	shortname = 'd1x'
	env_CPPDEFINES = ('DXX_BUILD_DESCENT_I',)

	# general source files
	def get_objects_common(self,
		__get_dxx_objects_common=DXXProgram.get_objects_common, \
		__get_dsx_objects_common=DXXCommon.create_lazy_object_states_getter((LazyObjectState(sources=(
'd1x-rebirth/main/custom.cpp',
'd1x-rebirth/main/snddecom.cpp',
),
	),
	LazyObjectState(sources=(
			# In Descent 1, bmread.cpp is used for both the regular
			# build and the editor build.
			#
			# In Descent 2, bmread.cpp is only used for the editor
			# build.
			#
			# Handle that inconsistency by defining it in the
			# per-program lookup (D1XProgram, D2XProgram), not in the
			# shared program lookup (DXXProgram).
'similar/main/bmread.cpp',
),
		transform_target=DXXProgram._apply_target_name,
	),
	))
		):
		value = __get_dxx_objects_common(self)
		value.extend(__get_dsx_objects_common(self))
		return value

	# for editor
	def get_objects_editor(self,
		__get_dxx_objects_editor=DXXProgram.get_objects_editor,
		__get_dsx_objects_editor=DXXCommon.create_lazy_object_getter((
'd1x-rebirth/editor/ehostage.cpp',
),
	)):
		value = list(__get_dxx_objects_editor(self))
		value.extend(__get_dsx_objects_editor(self))
		return value

class D2XProgram(DXXProgram):
	LazyObjectState = DXXProgram.LazyObjectState
	PROGRAM_NAME = 'D2X-Rebirth'
	target = \
	srcdir = 'd2x-rebirth'
	shortname = 'd2x'
	env_CPPDEFINES = ('DXX_BUILD_DESCENT_II',)

	# general source files
	def get_objects_common(self,
		__get_dxx_objects_common=DXXProgram.get_objects_common, \
		__get_dsx_objects_common=DXXCommon.create_lazy_object_getter((
'd2x-rebirth/libmve/decoder8.cpp',
'd2x-rebirth/libmve/decoder16.cpp',
'd2x-rebirth/libmve/mve_audio.cpp',
'd2x-rebirth/libmve/mvelib.cpp',
'd2x-rebirth/libmve/mveplay.cpp',
'd2x-rebirth/main/escort.cpp',
'd2x-rebirth/main/gamepal.cpp',
'd2x-rebirth/main/movie.cpp',
'd2x-rebirth/misc/physfsrwops.cpp',
	))):
		value = __get_dxx_objects_common(self)
		value.extend(__get_dsx_objects_common(self))
		return value

	# for editor
	def get_objects_editor(self,
		__get_dxx_objects_editor=DXXProgram.get_objects_editor, \
		__get_dsx_objects_editor=DXXCommon.create_lazy_object_states_getter((LazyObjectState(sources=(
			# See comment by D1XProgram reference to bmread.cpp for why
			# this is here instead of in the usual handling for similar
			# files.
'similar/main/bmread.cpp',
),
		transform_target=DXXProgram._apply_target_name,
		),
		))):
		value = list(__get_dxx_objects_editor(self))
		value.extend(__get_dsx_objects_editor(self))
		return value

def register_program(program,other_program,variables,filtered_help,append,_itertools_product=itertools.product):
	s = program.shortname
	l = [v for (k,v) in ARGLIST if k == s or k == 'dxx'] or [other_program.shortname not in ARGUMENTS]
	# Legacy case: build one configuration.
	if len(l) == 1:
		try:
			if not int(l[0]):
				# If the user specifies an integer that evaluates to
				# False, this configuration is disabled.  This allows
				# the user to build only one game, instead of both.
				return
			# Coerce to an empty string, then reuse the case for stacked
			# profiles.  This is slightly less efficient, but reduces
			# maintenance by not having multiple sites that call
			# program().
			l = ['']
		except ValueError:
			# If not an integer, treat this as a configuration profile.
			pass
	seen = set()
	add_seen = seen.add
	for e in l:
		for prefix in _itertools_product(*[v.split('+') for v in e.split(',')]):
			duplicates = set()
			# This would be simpler if set().add(V) returned the result
			# of `V not in self`, as seen before the add.  Instead, it
			# always returns None.
			#
			# Test for presence, then add if not present.  add() always
			# returns None, which coerces to False in boolean context.
			# This is slightly inefficient since we know the right hand
			# side will always be True after negation, so we ought to be
			# able to skip testing its truth value.  However, the
			# alternative is to use a wrapper function that checks
			# membership, adds the value, and returns the result of the
			# test.  Calling such a function is even less efficient.
			#
			# In most cases, this loop is not run often enough for the
			# efficiency to matter.
			prefix = tuple([
				p for p in prefix	\
					if (p not in duplicates and not duplicates.add(p))
			])
			if prefix in seen:
				continue
			add_seen(prefix)
			append(program(tuple(('%s%s%s' % (s, '_' if p else '', p) for p in prefix)) + prefix, variables, filtered_help))

def main(register_program,_d1xp=D1XProgram,_d2xp=D2XProgram):
	if os.path.isdir('build'):
		SConsignFile('build/.sconsign')
	variables = Variables([v for k, v in ARGLIST if k == 'site'] or ['site-local.py'], ARGUMENTS)
	filtered_help = FilterHelpText()
	dxx = []
	register_program(_d1xp, _d2xp, variables, filtered_help, dxx.append)
	register_program(_d2xp, _d1xp, variables, filtered_help, dxx.append)
	substenv = SCons.Environment.SubstitutionEnvironment()
	variables.FormatVariableHelpText = filtered_help.FormatVariableHelpText
	variables.Update(substenv)
# show some help when running scons -h
	Help("""DXX-Rebirth, SConstruct file help:

	Type 'scons' to build the binary.
	Type 'scons install' to build (if it hasn't been done) and install.
	Type 'scons -c' to clean up.

	Extra options (add them to command line, like 'scons extraoption=value'):
	d1x=[0/1]        Disable/enable D1X-Rebirth
	d1x=prefix-list  Enable D1X-Rebirth with prefix-list modifiers
	d2x=[0/1]        Disable/enable D2X-Rebirth
	d2x=prefix-list  Enable D2X-Rebirth with prefix-list modifiers
	dxx=VALUE        Equivalent to d1x=VALUE d2x=VALUE
""" +	\
		''.join(['%s:\n%s' % (d.program_message_prefix, d.init(substenv)) for d in dxx])
	)
	if not dxx:
		return
	compilation_database_dict_fn_to_entries = DXXCommon.compilation_database_dict_fn_to_entries
	if compilation_database_dict_fn_to_entries:
		import json
		for fn, entry_tuple in get_dictionary_item_view(compilation_database_dict_fn_to_entries):
			env, entries = entry_tuple
			e = env.Entry(fn)
			# clang tools search for this specific filename.  As a
			# convenience to the caller, if the target is a directory,
			# assume this filename in the named directory.  If the
			# caller wishes to generate the file under some other name,
			# that will be respected, though clang tools may refuse to
			# see it.
			if e.isdir() or fn.endswith('/'):
				e = e.File('compile_commands.json')
			# Sort by key so that dictionary ordering changes do not
			# cause unnecessary regeneration of the file.
			env.Textfile(target=e, source=env.Value(json.dumps(entries, indent=4, sort_keys=True)))

	unknown = variables.UnknownVariables()
	# Delete known unregistered variables
	unknown.pop('d1x', None)
	unknown.pop('d2x', None)
	unknown.pop('dxx', None)
	unknown.pop('site', None)
	ignore_unknown_variables = unknown.pop('ignore_unknown_variables', '0')
	if unknown:
		# Protect user from misspelled options by reporting an error.
		# Provide a way for the user to override the check, which might
		# be necessary if the user is setting an option that is only
		# understood by older (or newer) versions of SConstruct.
		try:
			ignore_unknown_variables = int(ignore_unknown_variables)
		except ValueError:
			ignore_unknown_variables = False
		j = 'Unknown values specified on command line.%s' % \
''.join(['\n\t%s' % k for k in unknown.keys()])
		if not ignore_unknown_variables:
			raise SCons.Errors.StopError(j +
'\nRemove unknown values or set ignore_unknown_variables=1 to continue.')
		print('warning: %s\nBuild will continue, but these values have no effect.\n' % j)

main(register_program)

# Local Variables:
# tab-width: 4
# End: