def install(name, sources, requirements=[], default_build=[], usage_requirements=[]):

    requirements = requirements[:]
    # Unless the user has explicitly asked us to hardcode dll paths, add
    # <hardcode-dll-paths>false in requirements, to override default value.
    if not "<hardcode-dll-paths>true" in requirements:
        requirements.append("<hardcode-dll-paths>false")

    if any(r.startswith("<tag>") for r in requirements):
        get_manager().errors()("The <tag> property is not allowed for the 'install' rule")

    from b2.manager import get_manager

    t = get_manager().targets()

    project = get_manager().projects().current()

    return t.main_target_alternative(
        InstallTargetClass(
            name,
            project,
            t.main_target_sources(sources, name),
            t.main_target_requirements(requirements, project),
            t.main_target_default_build(default_build, project),
            t.main_target_usage_requirements(usage_requirements, project),
        )
    )

def make_test(target_type, sources, requirements, target_name=None):

    if not target_name:
        target_name = stem(os.path.basename(sources[0]))

    # Having periods (".") in the target name is problematic because the typed
    # generator will strip the suffix and use the bare name for the file
    # targets. Even though the location-prefix averts problems most times it
    # does not prevent ambiguity issues when referring to the test targets. For
    # example when using the XML log output. So we rename the target to remove
    # the periods, and provide an alias for users.
    real_name = target_name.replace(".", "~")

    project = get_manager().projects().current()
    # The <location-prefix> forces the build system for generate paths in the
    # form '$build_dir/array1.test/gcc/debug'. This is necessary to allow
    # post-processing tools to work.
    t = get_manager().targets().create_typed_target(
        type.type_from_rule_name(target_type), project, real_name, sources,
        requirements + ["<location-prefix>" + real_name + ".test"], [], [])

    # The alias to the real target, per period replacement above.
    if real_name != target_name:
        get_manager().projects().project_rules().all_names_["alias"](
            target_name, [t])

    # Remember the test (for --dump-tests). A good way would be to collect all
    # given a project. This has some technical problems: e.g. we can not call
    # this dump from a Jamfile since projects referred by 'build-project' are
    # not available until the whole Jamfile has been loaded.
    __all_tests.append(t)
    return t

def __ensure_type (targets):
    """ Ensures all 'targets' have types. If this is not so, exists with 
        error.
    """
    for t in targets:
        if not t.type ():
            get_manager().errors()("target '%s' has no type" % str (t))

    def process (self, target, matches, binding):
       
        angle = regex.transform (matches, "<(.*)>")
        quoted = regex.transform (matches, '"(.*)"')

        g = str(id(self))
        b = os.path.normpath(os.path.dirname(binding[0]))
        
        # Attach binding of including file to included targets.
        # When target is directly created from virtual target
        # this extra information is unnecessary. But in other
        # cases, it allows to distinguish between two headers of the 
        # same name included from different places.      
        # We don't need this extra information for angle includes,
        # since they should not depend on including file (we can't
        # get literal "." in include path).
        g2 = g + "#" + b

        g = "<" + g + ">"
        g2 = "<" + g2 + ">"
        angle = [g + x for x in angle]
        quoted = [g2 + x for x in quoted]

        all = angle + quoted
        bjam.call("mark-included", target, all)

        engine = get_manager().engine()
        engine.set_target_variable(angle, "SEARCH", get_value(self.includes_))
        engine.set_target_variable(quoted, "SEARCH", [b] + get_value(self.includes_))
        
        # Just propagate current scanner to includes, in a hope
        # that includes do not change scanners. 
        get_manager().scanners().propagate(self, angle + quoted)

def __validate1 (property):
    """ Exit with error if property is not valid.
    """        
    msg = None

    f = get_grist (property)
    if f:
        value = get_value (property)

        if not feature.valid (f):
            f = ungrist (get_grist (property)) # Ungrist for better error messages
            msg = "Unknown feature '%s'" % f

        elif value and not 'free' in feature.attributes (f):
            feature.validate_value_string (f, value)

        elif not value:
            f = ungrist (get_grist (property)) # Ungrist for better error messages
            msg = "No value specified for feature '%s'" % f

    else:
        f = feature.implied_feature (property)
        feature.validate_value_string (f, property)

    if msg:
        # FIXME: don't use globals like this. Import here to
        # break circular dependency.
        from b2.manager import get_manager
        get_manager().errors()("Invalid property '%s': %s" % (property, msg))

def lib(names, sources=[], requirements=[], default_build=[], usage_requirements=[]):
    """The implementation of the 'lib' rule. Beyond standard syntax that rule allows
    simplified: 'lib a b c ;'."""

    if len(names) > 1:
        if any(r.startswith('<name>') for r in requirements):
            get_manager().errors()("When several names are given to the 'lib' rule\n" +
                                   "it is not allowed to specify the <name> feature.")

        if sources:
            get_manager().errors()("When several names are given to the 'lib' rule\n" +
                                   "it is not allowed to specify sources.")

    project = get_manager().projects().current()
    result = []

    for name in names:
        r = requirements[:]

        # Support " lib a ; " and " lib a b c ; " syntax.
        if not sources and not any(r.startswith("<name>") for r in requirements) \
           and not any(r.startswith("<file") for r in requirements):
            r.append("<name>" + name)

        result.append(targets.create_typed_metatarget(name, "LIB", sources,
                                                      r,
                                                      default_build,
                                                      usage_requirements))
    return result

    def process(self, target, matches, binding):

        target_path = os.path.normpath(os.path.dirname(binding[0]))
        bjam.call("mark-included", target, matches)

        get_manager().engine().set_target_variable(matches, "SEARCH", [target_path] + self.includes)
        get_manager().scanners().propagate(self, matches)

def reverse(path):
    """Returns path2 such that `os.path.join(path, path2) == '.'`.
    `path` may not contain '..' or be rooted.

    Args:
        path (str): the path to reverse

    Returns:
        the string of the reversed path

    Example:

        >>> p1 = 'path/to/somewhere'
        >>> p2 = reverse('path/to/somewhere')
        >>> p2
        '../../..'
        >>> os.path.normpath(os.path.join(p1, p2))
        '.'
    """
    if is_rooted(path) or '..' in path:
        from b2.manager import get_manager
        get_manager().errors()(
            'reverse(path): path is either rooted or contains ".." in the path')
    if path == '.':
        return path
    path = os.path.normpath(path)
    # os.sep.join() is being used over os.path.join() due
    # to an extra '..' that is created by os.path.join()
    return os.sep.join('..' for t in path.split(os.sep))

    def determine_output_name(self, sources):
        """Determine the name of the produced target from the
        names of the sources."""
        assert is_iterable_typed(sources, virtual_target.VirtualTarget)

        # The simple case if when a name
        # of source has single dot. Then, we take the part before
        # dot. Several dots can be caused by:
        # - Using source file like a.host.cpp
        # - A type which suffix has a dot. Say, we can
        #   type 'host_cpp' with extension 'host.cpp'.
        # In the first case, we want to take the part till the last
        # dot. In the second case -- no sure, but for now take
        # the part till the last dot too.
        name = os.path.splitext(sources[0].name())[0]

        for s in sources[1:]:
            n2 = os.path.splitext(s.name())
            if n2 != name:
                get_manager().errors()(
                    "%s: source targets have different names: cannot determine target name"
                    % (self.id_))

        # Names of sources might include directory. We should strip it.
        return self.determine_target_name(sources[0].name())

def register(type, suffixes=[], base_type=None):
    """ Registers a target type, possibly derived from a 'base-type'.
        If 'suffixes' are provided, they list all the suffixes that mean a file is of 'type'.
        Also, the first element gives the suffix to be used when constructing and object of
        'type'.
        type: a string
        suffixes: None or a sequence of strings
        base_type: None or a string
    """
    # Type names cannot contain hyphens, because when used as
    # feature-values they will be interpreted as composite features
    # which need to be decomposed.
    if __re_hyphen.search(type):
        raise BaseException('type name "%s" contains a hyphen' % type)

    # it's possible for a type to be registered with a
    # base type that hasn't been registered yet. in the
    # check for base_type below and the following calls to setdefault()
    # the key `type` will be added to __types. When the base type
    # actually gets registered, it would fail after the simple check
    # of "type in __types"; thus the check for "'base' in __types[type]"
    if type in __types and "base" in __types[type]:
        raise BaseException('Type "%s" is already registered.' % type)

    entry = __types.setdefault(type, {})
    entry["base"] = base_type
    entry.setdefault("derived", [])
    entry.setdefault("scanner", None)

    if base_type:
        __types.setdefault(base_type, {}).setdefault("derived", []).append(type)

    if len(suffixes) > 0:
        # Generated targets of 'type' will use the first of 'suffixes'
        # (this may be overriden)
        set_generated_target_suffix(type, [], suffixes[0])

        # Specify mapping from suffixes to type
        register_suffixes(suffixes, type)

    feature.extend("target-type", [type])
    feature.extend("main-target-type", [type])
    feature.extend("base-target-type", [type])

    if base_type:
        feature.compose("<target-type>" + type, [replace_grist(base_type, "<base-target-type>")])
        feature.compose("<base-target-type>" + type, ["<base-target-type>" + base_type])

    import b2.build.generators as generators

    # Adding a new derived type affects generator selection so we need to
    # make the generator selection module update any of its cached
    # information related to a new derived type being defined.
    generators.update_cached_information_with_a_new_type(type)

    # FIXME: resolving recursive dependency.
    from b2.manager import get_manager

    get_manager().projects().project_rules().add_rule_for_type(type)

def inherit(toolset, base):
    assert isinstance(toolset, basestring)
    assert isinstance(base, basestring)
    get_manager().projects().load_module(base, ['.']);

    inherit_generators(toolset, [], base)
    inherit_flags(toolset, base)
    inherit_rules(toolset, base)

def handle_input_files(input_files):
    if len(input_files) > 1:
        # Check that sorting made when creating property-set instance will not
        # change the ordering.
        if sorted(input_files) != input_files:
            get_manager().errors()("Names of input files must be sorted alphabetically\n" +
                                   "due to internal limitations")
    return ["<testing.input-file>" + f for f in input_files]

    def option(self, name, value):
        assert is_iterable(name) and isinstance(name[0], basestring)
        assert is_iterable(value) and isinstance(value[0], basestring)
        name = name[0]
        if not name in ["site-config", "user-config", "project-config"]:
            get_manager().errors()("The 'option' rule may be used only in site-config or user-config")

        option.set(name, value[0])

    def set_default(self, value):
        assert isinstance(value, basestring)
        for attr in ('free', 'optional'):
            if getattr(self, attr):
                get_manager().errors()('"{}" feature "<{}>" cannot have a default value.'
                                       .format(attr, self.name))

        self.default = value

def __ensure_type (targets):
    """ Ensures all 'targets' have types. If this is not so, exists with
        error.
    """
    assert is_iterable_typed(targets, virtual_target.VirtualTarget)
    for t in targets:
        if not t.type ():
            get_manager().errors()("target '%s' has no type" % str (t))

    def run(self, project, name, ps, sources):
        pass
        action_name = ps.get("action")[0]
        if action_name[0] == "@":
            action = virtual_target.Action(get_manager(), sources, action_name[1:], ps)
        else:
            action = virtual_target.Action(get_manager(), sources, "notfile.run", ps)

        return [get_manager().virtual_targets().register(virtual_target.NotFileTarget(name, project, action))]

def gcc_compile_cpp(targets, sources, properties):
    # Some extensions are compiled as C++ by default. For others, we need to
    # pass -x c++. We could always pass -x c++ but distcc does not work with it.
    extension = os.path.splitext (sources [0]) [1]
    lang = ''
    if not extension in ['.cc', '.cp', '.cxx', '.cpp', '.c++', '.C']:
        lang = '-x c++'
    get_manager().engine().set_target_variable (targets, 'LANG', lang)
    engine.add_dependency(targets, bjam.call('get-target-variable', targets, 'PCH_FILE'))

def message(name, *args):

    if type(name) == type([]):
        name = name[0]

    t = get_manager().targets()
    
    project = get_manager().projects().current()
        
    return t.main_target_alternative(MessageTargetClass(*((name, project) + args)))

def register(type, suffixes=[], base_type=None):
    """ Registers a target type, possibly derived from a 'base-type'. 
        If 'suffixes' are provided, they list all the suffixes that mean a file is of 'type'.
        Also, the first element gives the suffix to be used when constructing and object of
        'type'.
        type: a string
        suffixes: None or a sequence of strings
        base_type: None or a string
    """
    # Type names cannot contain hyphens, because when used as
    # feature-values they will be interpreted as composite features
    # which need to be decomposed.
    if __re_hyphen.search(type):
        raise BaseException('type name "%s" contains a hyphen' % type)

    if __types.has_key(type):
        raise BaseException('Type "%s" is already registered.' % type)

    entry = {}
    entry["base"] = base_type
    entry["derived"] = []
    entry["scanner"] = None
    __types[type] = entry

    if base_type:
        __types[base_type]["derived"].append(type)

    if len(suffixes) > 0:
        # Generated targets of 'type' will use the first of 'suffixes'
        # (this may be overriden)
        set_generated_target_suffix(type, [], suffixes[0])

        # Specify mapping from suffixes to type
        register_suffixes(suffixes, type)

    feature.extend("target-type", [type])
    feature.extend("main-target-type", [type])
    feature.extend("base-target-type", [type])

    if base_type:
        feature.compose("<target-type>" + type, replace_grist(base_type, "<base-target-type>"))
        feature.compose("<base-target-type>" + type, "<base-target-type>" + base_type)

    import b2.build.generators as generators

    # Adding a new derived type affects generator selection so we need to
    # make the generator selection module update any of its cached
    # information related to a new derived type being defined.
    generators.update_cached_information_with_a_new_type(type)

    # FIXME: resolving recursive dependency.
    from b2.manager import get_manager

    get_manager().projects().project_rules().add_rule_for_type(type)

def alias(name, sources=[], requirements=[], default_build=[], usage_requirements=[]):

    project = get_manager().projects().current()
    targets = get_manager().targets()

    targets.main_target_alternative(AliasTarget(
        name, project,
        targets.main_target_sources(sources, name, no_renaming=True),
        targets.main_target_requirements(requirements or [], project),
        targets.main_target_default_build(default_build, project),
        targets.main_target_usage_requirements(usage_requirements or [], project)))