merge upstream/master

1 files changed, 0 insertions, 1408 deletions

diff --git a/jam-files/boost-build/build/generators.jam b/jam-files/boost-build/build/generators.jam
deleted file mode 100644
index 1515525f..00000000
--- a/jam-files/boost-build/build/generators.jam
+++ /dev/null
@@ -1,1408 +0,0 @@
-# Copyright Vladimir Prus 2002.
-# Copyright Rene Rivera 2006.
-#
-# Distributed under the Boost Software License, Version 1.0.
-#    (See accompanying file LICENSE_1_0.txt or copy at
-#          http://www.boost.org/LICENSE_1_0.txt)
-
-# Manages 'generators' --- objects which can do transformation between different
-# target types and contain algorithm for finding transformation from sources to
-# targets.
-#
-# The main entry point to this module is generators.construct rule. It is given
-# a list of source targets, desired target type and a set of properties. It
-# starts by selecting 'viable generators', which have any chances of producing
-# the desired target type with the required properties. Generators are ranked
-# and a set of the most specific ones is selected.
-#
-# The most specific generators have their 'run' methods called, with the
-# properties and list of sources. Each one selects a target which can be
-# directly consumed, and tries to convert the remaining ones to the types it can
-# consume. This is done by recursively calling 'construct' with all consumable
-# types.
-#
-# If the generator has collected all the targets it needs, it creates targets
-# corresponding to result, and returns it. When all generators have been run,
-# results of one of them are selected and returned as a result.
-#
-# It is quite possible for 'construct' to return more targets that it was asked
-# for. For example, if it were asked to generate a target of type EXE, but the
-# only found generator produces both EXE and TDS (file with debug) information.
-# The extra target will be returned.
-#
-# Likewise, when generator tries to convert sources to consumable types, it can
-# get more targets that it was asked for. The question is what to do with extra
-# targets. Boost.Build attempts to convert them to requested types, and attempts
-# that as early as possible. Specifically, this is done after invoking each
-# generator. TODO: An example is needed to document the rationale for trying
-# extra target conversion at that point.
-#
-# In order for the system to be able to use a specific generator instance 'when
-# needed', the instance needs to be registered with the system using
-# generators.register() or one of its related rules. Unregistered generators may
-# only be run explicitly and will not be considered by Boost.Build when when
-# converting between given target types.
-
-import "class" : new ;
-import errors ;
-import property-set ;
-import sequence ;
-import set ;
-import type ;
-import utility ;
-import virtual-target ;
-
-
-if "--debug-generators" in [ modules.peek : ARGV ]
-{
-    .debug = true ;
-}
-
-
-# Updated cached viable source target type information as needed after a new
-# target type gets defined. This is needed because if a target type is a viable
-# source target type for some generator then all of the target type's derived
-# target types should automatically be considered as viable source target types
-# for the same generator as well. Does nothing if a non-derived target type is
-# passed to it.
-#
-rule update-cached-information-with-a-new-type ( type )
-{
-    local base-type = [ type.base $(type) ] ;
-    if $(base-type)
-    {
-        for local g in $(.vstg-cached-generators)
-        {
-            if $(base-type) in $(.vstg.$(g))
-            {
-                .vstg.$(g) += $(type) ;
-            }
-        }
-
-        for local t in $(.vst-cached-types)
-        {
-            if $(base-type) in $(.vst.$(t))
-            {
-                .vst.$(t) += $(type) ;
-            }
-        }
-    }
-}
-
-
-# Clears cached viable source target type information except for target types
-# and generators with all source types listed as viable. Should be called when
-# something invalidates those cached values by possibly causing some new source
-# types to become viable.
-#
-local rule invalidate-extendable-viable-source-target-type-cache ( )
-{
-    local generators-with-cached-source-types = $(.vstg-cached-generators) ;
-    .vstg-cached-generators = ;
-    for local g in $(generators-with-cached-source-types)
-    {
-        if $(.vstg.$(g)) = *
-        {
-            .vstg-cached-generators += $(g) ;
-        }
-        else
-        {
-            .vstg.$(g) = ;
-        }
-    }
-
-    local types-with-cached-source-types = $(.vst-cached-types) ;
-    .vst-cached-types = ;
-    for local t in $(types-with-cached-source-types)
-    {
-        if $(.vst.$(t)) = *
-        {
-            .vst-cached-types += $(t) ;
-        }
-        else
-        {
-            .vst.$(t) = ;
-        }
-    }
-}
-
-
-# Outputs a debug message if generators debugging is on. Each element of
-# 'message' is checked to see if it is a class instance. If so, instead of the
-# value, the result of 'str' call is output.
-#
-local rule generators.dout ( message * )
-{
-    if $(.debug)
-    {
-        ECHO [ sequence.transform utility.str : $(message) ] ;
-    }
-}
-
-
-local rule indent ( )
-{
-    return $(.indent:J="") ;
-}
-
-
-local rule increase-indent ( )
-{
-    .indent += "    " ;
-}
-
-
-local rule decrease-indent ( )
-{
-    .indent = $(.indent[2-]) ;
-}
-
-
-# Models a generator.
-#
-class generator
-{
-    import generators : indent increase-indent decrease-indent generators.dout ;
-    import set ;
-    import utility ;
-    import feature ;
-    import errors ;
-    import sequence ;
-    import type ;
-    import virtual-target ;
-    import "class" : new ;
-    import property ;
-    import path ;
-
-    EXPORT class@generator : indent increase-indent decrease-indent
-        generators.dout ;
-
-    rule __init__ (
-        id                          # Identifies the generator - should be name
-                                    # of the rule which sets up the build
-                                    # actions.
-
-        composing ?                 # Whether generator processes each source
-                                    # target in turn, converting it to required
-                                    # types. Ordinary generators pass all
-                                    # sources together to the recursive
-                                    # generators.construct-types call.
-
-        : source-types *            # Types that this generator can handle. If
-                                    # empty, the generator can consume anything.
-
-        : target-types-and-names +  # Types the generator will create and,
-                                    # optionally, names for created targets.
-                                    # Each element should have the form
-                                    # type["(" name-pattern ")"], for example,
-                                    # obj(%_x). Generated target name will be
-                                    # found by replacing % with the name of
-                                    # source, provided an explicit name was not
-                                    # specified.
-
-        : requirements *
-    )
-    {
-        self.id = $(id) ;
-        self.rule-name = $(id) ;
-        self.composing = $(composing) ;
-        self.source-types = $(source-types) ;
-        self.target-types-and-names = $(target-types-and-names) ;
-        self.requirements = $(requirements) ;
-
-        for local e in $(target-types-and-names)
-        {
-            # Create three parallel lists: one with the list of target types,
-            # and two other with prefixes and postfixes to be added to target
-            # name. We use parallel lists for prefix and postfix (as opposed to
-            # mapping), because given target type might occur several times, for
-            # example "H H(%_symbols)".
-            local m = [ MATCH ([^\\(]*)(\\((.*)%(.*)\\))? : $(e) ] ;
-            self.target-types += $(m[1]) ;
-            self.name-prefix += $(m[3]:E="") ;
-            self.name-postfix += $(m[4]:E="") ;
-        }
-
-        # Note that 'transform' here, is the same as 'for_each'.
-        sequence.transform type.validate : $(self.source-types) ;
-        sequence.transform type.validate : $(self.target-types) ;
-    }
-
-    ################# End of constructor #################
-
-    rule id ( )
-    {
-        return $(self.id) ;
-    }
-
-    # Returns the list of target type the generator accepts.
-    #
-    rule source-types ( )
-    {
-        return $(self.source-types) ;
-    }
-
-    # Returns the list of target types that this generator produces. It is
-    # assumed to be always the same -- i.e. it can not change depending on some
-    # provided list of sources.
-    #
-    rule target-types ( )
-    {
-        return $(self.target-types) ;
-    }
-
-    # Returns the required properties for this generator. Properties in returned
-    # set must be present in build properties if this generator is to be used.
-    # If result has grist-only element, that build properties must include some
-    # value of that feature.
-    #
-    # XXX: remove this method?
-    #
-    rule requirements ( )
-    {
-        return $(self.requirements) ;
-    }
-    
-    rule set-rule-name ( rule-name )
-    {
-        self.rule-name = $(rule-name) ;
-    }
-    
-    rule rule-name ( )
-    {
-        return $(self.rule-name) ;
-    }
-        
-    # Returns a true value if the generator can be run with the specified
-    # properties.
-    #
-    rule match-rank ( property-set-to-match )
-    {
-        # See if generator requirements are satisfied by 'properties'. Treat a
-        # feature name in requirements (i.e. grist-only element), as matching
-        # any value of the feature.
-        local all-requirements = [ requirements ] ;
-
-        local property-requirements feature-requirements ;
-        for local r in $(all-requirements)
-        {
-            if $(r:G=)
-            {
-                property-requirements += $(r) ;
-            }
-            else
-            {
-                feature-requirements += $(r) ;
-            }
-        }
-
-        local properties-to-match = [ $(property-set-to-match).raw ] ;
-        if $(property-requirements) in $(properties-to-match) &&
-            $(feature-requirements) in $(properties-to-match:G)
-        {
-            return true ;
-        }
-        else
-        {
-            return ;
-        }
-    }
-
-    # Returns another generator which differs from $(self) in
-    #   - id
-    #   - value to <toolset> feature in properties
-    #
-    rule clone ( new-id : new-toolset-properties + )
-    {
-        local g = [ new $(__class__) $(new-id) $(self.composing) :
-            $(self.source-types) : $(self.target-types-and-names) :
-            # Note: this does not remove any subfeatures of <toolset> which
-            # might cause problems.
-            [ property.change $(self.requirements) : <toolset> ]
-            $(new-toolset-properties) ] ;       
-        return $(g) ;
-    }
-
-    # Creates another generator that is the same as $(self), except that if
-    # 'base' is in target types of $(self), 'type' will in target types of the
-    # new generator.
-    #
-    rule clone-and-change-target-type ( base : type )
-    {
-        local target-types ;
-        for local t in $(self.target-types-and-names)
-        {
-            local m = [ MATCH ([^\\(]*)(\\(.*\\))? : $(t) ] ;
-            if $(m) = $(base)
-            {
-                target-types += $(type)$(m[2]:E="") ;
-            }
-            else
-            {
-                target-types += $(t) ;
-            }
-        }
-
-        local g = [ new $(__class__) $(self.id) $(self.composing) :
-            $(self.source-types) : $(target-types) : $(self.requirements) ] ;
-        if $(self.rule-name)
-        {            
-            $(g).set-rule-name $(self.rule-name) ;
-        }        
-        return $(g) ;        
-    }
-
-    # Tries to invoke this generator on the given sources. Returns a list of
-    # generated targets (instances of 'virtual-target') and optionally a set of
-    # properties to be added to the usage-requirements for all the generated
-    # targets. Returning nothing from run indicates that the generator was
-    # unable to create the target.
-    #
-    rule run
-    (
-        project         # Project for which the targets are generated.
-        name ?          # Used when determining the 'name' attribute for all
-                        # generated targets. See the 'generated-targets' method.
-        : property-set  # Desired properties for generated targets.
-        : sources +     # Source targets.
-    )
-    {
-        generators.dout [ indent ] "  ** generator" $(self.id) ;
-        generators.dout [ indent ] "  composing:" $(self.composing) ;
-
-        if ! $(self.composing) && $(sources[2]) && $(self.source-types[2])
-        {
-            errors.error "Unsupported source/source-type combination" ;
-        }
-
-        # We do not run composing generators if no name is specified. The reason
-        # is that composing generator combines several targets, which can have
-        # different names, and it cannot decide which name to give for produced
-        # target. Therefore, the name must be passed.
-        #
-        # This in effect, means that composing generators are runnable only at
-        # the top-level of a transformation graph, or if their name is passed
-        # explicitly. Thus, we dissallow composing generators in the middle. For
-        # example, the transformation CPP -> OBJ -> STATIC_LIB -> RSP -> EXE
-        # will not be allowed as the OBJ -> STATIC_LIB generator is composing.
-        if ! $(self.composing) || $(name)
-        {
-            run-really $(project) $(name) : $(property-set) : $(sources) ;
-        }
-    }
-
-    rule run-really ( project name ? : property-set : sources + )
-    {
-        # Targets that this generator will consume directly.
-        local consumed = ;
-        # Targets that can not be consumed and will be returned as-is.
-        local bypassed = ;
-
-        if $(self.composing)
-        {
-            convert-multiple-sources-to-consumable-types $(project)
-                : $(property-set) : $(sources) : consumed bypassed ;
-        }
-        else
-        {
-            convert-to-consumable-types $(project) $(name) : $(property-set)
-                : $(sources) : : consumed bypassed ;
-        }
-
-        local result ;
-        if $(consumed)
-        {
-            result = [ construct-result $(consumed) : $(project) $(name) :
-                $(property-set) ] ;
-        }
-
-        if $(result)
-        {
-            generators.dout [ indent ] "  SUCCESS: " $(result) ;
-        }
-        else
-        {
-            generators.dout [ indent ] "  FAILURE" ;
-        }
-        generators.dout ;
-        return $(result) ;
-    }
-
-    # Constructs the dependency graph to be returned by this generator.
-    #
-    rule construct-result
-    (
-        consumed +        # Already prepared list of consumable targets.
-                          # Composing generators may receive multiple sources
-                          # all of which will have types matching those in
-                          # $(self.source-types). Non-composing generators with
-                          # multiple $(self.source-types) will receive exactly
-                          # len $(self.source-types) sources with types matching
-                          # those in $(self.source-types). And non-composing
-                          # generators with only a single source type may
-                          # receive multiple sources with all of them of the
-                          # type listed in $(self.source-types).
-        : project name ?
-        : property-set    # Properties to be used for all actions created here.
-    )
-    {
-        local result ;
-        # If this is 1->1 transformation, apply it to all consumed targets in
-        # order.
-        if ! $(self.source-types[2]) && ! $(self.composing)
-        {
-            for local r in $(consumed)
-            {
-                result += [ generated-targets $(r) : $(property-set) :
-                    $(project) $(name) ] ;
-            }
-        }
-        else if $(consumed)
-        {
-            result += [ generated-targets $(consumed) : $(property-set) :
-                $(project) $(name) ] ;
-        }
-        return $(result) ;
-    }
-
-    # Determine target name from fullname (maybe including path components)
-    # Place optional prefix and postfix around basename
-    #
-    rule determine-target-name ( fullname  : prefix ? : postfix ? )
-    {
-        # See if we need to add directory to the target name.
-        local dir  = $(fullname:D) ;            
-        local name = $(fullname:B) ; 
-        
-        name = $(prefix:E=)$(name) ;
-        name = $(name)$(postfix:E=) ;
-
-        if $(dir) && 
-          # Never append '..' to target path.
-          ! [ MATCH .*(\\.\\.).* : $(dir) ] 
-            && 
-          ! [ path.is-rooted $(dir) ]
-        {
-            # Relative path is always relative to the source
-            # directory. Retain it, so that users can have files
-            # with the same in two different subdirectories.
-            name = $(dir)/$(name) ;                
-        }            
-        return $(name) ;
-    }
-
-    # Determine the name of the produced target from the names of the sources.
-    #
-    rule determine-output-name ( sources + )
-    {
-        # 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, or
-        #   - a type whose suffix has a dot. Say, we can type 'host_cpp' with
-        #     extension 'host.cpp'.
-        # In the first case, we want to take the part up to the last dot. In the
-        # second case -- not sure, but for now take the part up to the last dot
-        # too.
-        name = [ utility.basename [ $(sources[1]).name ] ] ;
-
-        for local s in $(sources[2])
-        {
-            local n2 = [ utility.basename [ $(s).name ] ] ;
-            if $(n2) != $(name)
-            {
-                errors.error "$(self.id): source targets have different names: cannot determine target name" ;
-            }
-        }
-        name = [ determine-target-name [ $(sources[1]).name ] ] ;
-        return $(name) ;
-    }
-
-    # Constructs targets that are created after consuming 'sources'. The result
-    # will be the list of virtual-target, which has the same length as the
-    # 'target-types' attribute and with corresponding types.
-    #
-    # When 'name' is empty, all source targets must have the same 'name'
-    # attribute value, which will be used instead of the 'name' argument.
-    #
-    # The 'name' attribute value for each generated target will be equal to
-    # the 'name' parameter if there is no name pattern for this type. Otherwise,
-    # the '%' symbol in the name pattern will be replaced with the 'name'
-    # parameter to obtain the 'name' attribute.
-    #
-    # For example, if targets types are T1 and T2 (with name pattern "%_x"),
-    # suffixes for T1 and T2 are .t1 and .t2, and source is foo.z, then created
-    # files would be "foo.t1" and "foo_x.t2". The 'name' attribute actually
-    # determines the basename of a file.
-    #
-    # Note that this pattern mechanism has nothing to do with implicit patterns
-    # in make. It is a way to produce a target whose name is different than the
-    # name of its source.
-    #
-    rule generated-targets ( sources + : property-set : project name ? )
-    {
-        if ! $(name)
-        {
-            name = [ determine-output-name $(sources) ] ;
-        }
-
-        # Assign an action for each target.
-        local action = [ action-class ] ;
-        local a = [ class.new $(action) $(sources) : $(self.rule-name) :
-                    $(property-set) ] ;
-
-        # Create generated target for each target type.
-        local targets ;
-        local pre = $(self.name-prefix) ;
-        local post = $(self.name-postfix) ;
-        for local t in $(self.target-types)
-        {
-            local generated-name = $(pre[1])$(name:BS)$(post[1]) ;
-            generated-name = $(generated-name:R=$(name:D)) ;
-            pre = $(pre[2-]) ;
-            post = $(post[2-]) ;
-
-            targets += [ class.new file-target $(generated-name) : $(t) :
-                $(project) : $(a) ] ;
-        }
-
-        return [ sequence.transform virtual-target.register : $(targets) ] ;
-    }
-
-    # Attempts to convert 'sources' to targets of types that this generator can
-    # handle. The intention is to produce the set of targets that can be used
-    # when the generator is run.
-    #
-    rule convert-to-consumable-types
-    (
-        project name ?
-        : property-set
-        : sources +
-        : only-one ?    # Convert 'source' to only one of the source types. If
-                        # there is more that one possibility, report an error.
-        : consumed-var  # Name of the variable which receives all targets which
-                        # can be consumed.
-          bypassed-var  # Name of the variable which receives all targets which
-                        # can not be consumed.
-    )
-    {
-        # We are likely to be passed 'consumed' and 'bypassed' var names. Use
-        # '_' to avoid name conflicts.
-        local _consumed ;
-        local _bypassed ;
-        local missing-types ;
-
-        if $(sources[2])
-        {
-            # Do not know how to handle several sources yet. Just try to pass
-            # the request to other generator.
-            missing-types = $(self.source-types) ;
-        }
-        else
-        {
-            consume-directly $(sources) : _consumed : missing-types ;
-        }
-
-        # No need to search for transformation if some source type has consumed
-        # source and no more source types are needed.
-        if $(only-one) && $(_consumed)
-        {
-            missing-types = ;
-        }
-
-        # TODO: we should check that only one source type if create of
-        # 'only-one' is true.
-        # TODO: consider if consumed/bypassed separation should be done by
-        # 'construct-types'.
-
-        if $(missing-types)
-        {
-            local transformed = [ generators.construct-types $(project) $(name)
-                : $(missing-types) : $(property-set) : $(sources) ] ;
-
-            # Add targets of right type to 'consumed'. Add others to 'bypassed'.
-            # The 'generators.construct' rule has done its best to convert
-            # everything to the required type. There is no need to rerun it on
-            # targets of different types.
-
-            # NOTE: ignoring usage requirements.
-            for local t in $(transformed[2-])
-            {
-                if [ $(t).type ] in $(missing-types)
-                {
-                    _consumed += $(t) ;
-                }
-                else
-                {
-                    _bypassed += $(t) ;
-                }
-            }
-        }
-
-        _consumed = [ sequence.unique $(_consumed) ] ;
-        _bypassed = [ sequence.unique $(_bypassed) ] ;
-
-        # Remove elements of '_bypassed' that are in '_consumed'.
-
-        # Suppose the target type of current generator, X is produced from X_1
-        # and X_2, which are produced from Y by one generator. When creating X_1
-        # from Y, X_2 will be added to 'bypassed'. Likewise, when creating X_2
-        # from Y, X_1 will be added to 'bypassed', but they are also in
-        # 'consumed'. We have to remove them from bypassed, so that generators
-        # up the call stack do not try to convert them.
-
-        # In this particular case, X_1 instance in 'consumed' and X_1 instance
-        # in 'bypassed' will be the same: because they have the same source and
-        # action name, and 'virtual-target.register' will not allow two
-        # different instances. Therefore, it is OK to use 'set.difference'.
-
-        _bypassed = [ set.difference $(_bypassed) : $(_consumed) ] ;
-
-        $(consumed-var) += $(_consumed) ;
-        $(bypassed-var) += $(_bypassed) ;
-    }
-
-    # Converts several files to consumable types. Called for composing
-    # generators only.
-    #
-    rule convert-multiple-sources-to-consumable-types ( project : property-set :
-        sources * : consumed-var bypassed-var )
-    {
-        # We process each source one-by-one, trying to convert it to a usable
-        # type.
-        for local source in $(sources)
-        {
-            local _c ;
-            local _b ;
-            # TODO: need to check for failure on each source.
-            convert-to-consumable-types $(project) : $(property-set) : $(source)
-                : true : _c _b ;
-            if ! $(_c)
-            {
-                generators.dout [ indent ] " failed to convert " $(source) ;
-            }
-            $(consumed-var) += $(_c) ;
-            $(bypassed-var) += $(_b) ;
-        }
-    }
-
-    rule consume-directly ( source : consumed-var : missing-types-var )
-    {
-        local real-source-type = [ $(source).type ] ;
-
-        # If there are no source types, we can consume anything.
-        local source-types = $(self.source-types) ;
-        source-types ?= $(real-source-type) ;
-
-        for local st in $(source-types)
-        {
-            # The 'source' if of the right type already.
-            if $(real-source-type) = $(st) || [ type.is-derived
-                $(real-source-type) $(st) ]
-            {
-                $(consumed-var) += $(source) ;
-            }
-            else
-            {
-                $(missing-types-var) += $(st) ;
-            }
-        }
-    }
-
-    # Returns the class to be used to actions. Default implementation returns
-    # "action".
-    #
-    rule action-class ( )
-    {
-        return "action" ;
-    }
-}
-
-
-# Registers a new generator instance 'g'.
-#
-rule register ( g )
-{
-    .all-generators += $(g) ;
-        
-    # A generator can produce several targets of the same type. We want unique
-    # occurrence of that generator in .generators.$(t) in that case, otherwise,
-    # it will be tried twice and we will get a false ambiguity.
-    for local t in [ sequence.unique [ $(g).target-types ] ]
-    {
-        .generators.$(t) += $(g) ;
-    }
-
-    # Update the set of generators for toolset.
-
-    # TODO: should we check that generator with this id is not already
-    # registered. For example, the fop.jam module intentionally declared two
-    # generators with the same id, so such check will break it.
-    local id = [ $(g).id ] ;
-
-    # Some generators have multiple periods in their name, so a simple $(id:S=)
-    # will not generate the right toolset name. E.g. if id = gcc.compile.c++,
-    # then .generators-for-toolset.$(id:S=) will append to
-    # .generators-for-toolset.gcc.compile, which is a separate value from
-    # .generators-for-toolset.gcc. Correcting this makes generator inheritance
-    # work properly. See also inherit-generators in the toolset module.
-    local base = $(id) ;
-    while $(base:S)
-    {
-        base = $(base:B) ;
-    }
-    .generators-for-toolset.$(base) += $(g) ;
-
-
-    # After adding a new generator that can construct new target types, we need
-    # to clear the related cached viable source target type information for
-    # constructing a specific target type or using a specific generator. Cached
-    # viable source target type lists affected by this are those containing any
-    # of the target types constructed by the new generator or any of their base
-    # target types.
-    #
-    # A more advanced alternative to clearing that cached viable source target
-    # type information would be to expand it with additional source types or
-    # even better - mark it as needing to be expanded on next use.
-    #
-    # Also see the http://thread.gmane.org/gmane.comp.lib.boost.build/19077
-    # mailing list thread for an even more advanced idea of how we could convert
-    # Boost Build's Jamfile processing, target selection and generator selection
-    # into separate steps which would prevent these caches from ever being
-    # invalidated.
-    #
-    # For now we just clear all the cached viable source target type information
-    # that does not simply state 'all types' and may implement a more detailed
-    # algorithm later on if it becomes needed.
-
-    invalidate-extendable-viable-source-target-type-cache ;
-}
-
-
-# Creates a new non-composing 'generator' class instance and registers it.
-# Returns the created instance. Rationale: the instance is returned so that it
-# is possible to first register a generator and then call its 'run' method,
-# bypassing the whole generator selection process.
-#
-rule register-standard ( id : source-types * : target-types + : requirements * )
-{
-    local g = [ new generator $(id) : $(source-types) : $(target-types) :
-        $(requirements) ] ;
-    register $(g) ;
-    return $(g) ;
-}
-
-
-# Creates a new composing 'generator' class instance and registers it.
-#
-rule register-composing ( id : source-types * : target-types + : requirements *
-    )
-{
-    local g = [ new generator $(id) true : $(source-types) : $(target-types) :
-        $(requirements) ] ;
-    register $(g) ;
-    return $(g) ;
-}
-
-
-# Returns all generators belonging to the given 'toolset', i.e. whose ids are
-# '$(toolset).<something>'.
-#
-rule generators-for-toolset ( toolset )
-{
-    return $(.generators-for-toolset.$(toolset)) ;
-}
-
-
-# Make generator 'overrider-id' be preferred to 'overridee-id'. If, when
-# searching for generators that could produce a target of a certain type, both
-# those generators are among viable generators, the overridden generator is
-# immediately discarded.
-#
-# The overridden generators are discarded immediately after computing the list
-# of viable generators but before running any of them.
-#
-rule override ( overrider-id : overridee-id )
-{
-    .override.$(overrider-id) += $(overridee-id) ;
-}
-
-
-# Returns a list of source type which can possibly be converted to 'target-type'
-# by some chain of generator invocation.
-#
-# More formally, takes all generators for 'target-type' and returns a union of
-# source types for those generators and result of calling itself recursively on
-# source types.
-#
-# Returns '*' in case any type should be considered a viable source type for the
-# given type.
-#
-local rule viable-source-types-real ( target-type )
-{
-    local result ;
-
-    # 't0' is the initial list of target types we need to process to get a list
-    # of their viable source target types. New target types will not be added to
-    # this list.
-    local t0 = [ type.all-bases $(target-type) ] ;
-
-    # 't' is the list of target types which have not yet been processed to get a
-    # list of their viable source target types. This list will get expanded as
-    # we locate more target types to process.
-    local t = $(t0) ;
-
-    while $(t)
-    {
-        # Find all generators for the current type. Unlike
-        # 'find-viable-generators' we do not care about the property-set.
-        local generators = $(.generators.$(t[1])) ;
-        t = $(t[2-]) ;
-
-        while $(generators)
-        {
-            local g = $(generators[1]) ;
-            generators = $(generators[2-]) ;
-
-            if ! [ $(g).source-types ]
-            {
-                # Empty source types -- everything can be accepted.
-                result = * ;
-                # This will terminate this loop.
-                generators = ;
-                # This will terminate the outer loop.
-                t = ;
-            }
-
-            for local source-type in [ $(g).source-types ]
-            {
-                if ! $(source-type) in $(result)
-                {
-                    # If a generator accepts a 'source-type' it will also
-                    # happily accept any type derived from it.
-                    for local n in [ type.all-derived $(source-type) ]
-                    {
-                        if ! $(n) in $(result)
-                        {
-                            # Here there is no point in adding target types to
-                            # the list of types to process in case they are or
-                            # have already been on that list. We optimize this
-                            # check by realizing that we only need to avoid the
-                            # original target type's base types. Other target
-                            # types that are or have been on the list of target
-                            # types to process have been added to the 'result'
-                            # list as well and have thus already been eliminated
-                            # by the previous if.
-                            if ! $(n) in $(t0)
-                            {
-                                t += $(n) ;
-                            }
-                            result += $(n) ;
-                        }
-                    }
-                }
-            }
-        }
-    }
-
-    return $(result) ;
-}
-
-
-# Helper rule, caches the result of 'viable-source-types-real'.
-#
-rule viable-source-types ( target-type )
-{
-    local key = .vst.$(target-type) ;
-    if ! $($(key))
-    {
-        .vst-cached-types += $(target-type) ;
-        local v = [ viable-source-types-real $(target-type) ] ;
-        if ! $(v)
-        {
-            v = none ;
-        }
-        $(key) = $(v) ;
-    }
-
-    if $($(key)) != none
-    {
-        return $($(key)) ;
-    }
-}
-
-
-# Returns the list of source types, which, when passed to 'run' method of
-# 'generator', has some change of being eventually used (probably after
-# conversion by other generators).
-#
-# Returns '*' in case any type should be considered a viable source type for the
-# given generator.
-#
-rule viable-source-types-for-generator-real ( generator )
-{
-    local source-types = [ $(generator).source-types ] ;
-    if ! $(source-types)
-    {
-        # If generator does not specify any source types, it might be a special
-        # generator like builtin.lib-generator which just relays to other
-        # generators. Return '*' to indicate that any source type is possibly
-        # OK, since we do not know for sure.
-        return * ;
-    }
-    else
-    {
-        local result ;
-        while $(source-types)
-        {
-            local s = $(source-types[1]) ;
-            source-types = $(source-types[2-]) ;
-            local viable-sources = [ generators.viable-source-types $(s) ] ;
-            if $(viable-sources) = *
-            {
-                result = * ;
-                source-types = ;  # Terminate the loop.
-            }
-            else
-            {
-                result += [ type.all-derived $(s) ] $(viable-sources) ;
-            }
-        }
-        return [ sequence.unique $(result) ] ;
-    }
-}
-
-
-# Helper rule, caches the result of 'viable-source-types-for-generator'.
-#
-local rule viable-source-types-for-generator ( generator )
-{
-    local key = .vstg.$(generator) ;
-    if ! $($(key))
-    {
-        .vstg-cached-generators += $(generator) ;
-        local v = [ viable-source-types-for-generator-real $(generator) ] ;
-        if ! $(v)
-        {
-            v = none ;
-        }
-        $(key) = $(v) ;
-    }
-
-    if $($(key)) != none
-    {
-        return $($(key)) ;
-    }
-}
-
-
-# Returns usage requirements + list of created targets.
-#
-local rule try-one-generator-really ( project name ? : generator : target-type
-    : property-set : sources * )
-{
-    local targets =
-        [ $(generator).run $(project) $(name) : $(property-set) : $(sources) ] ;
-
-    local usage-requirements ;
-    local success ;
-
-    generators.dout [ indent ] returned $(targets) ;
-
-    if $(targets)
-    {
-        success = true ;
-
-        if  [ class.is-a $(targets[1]) : property-set ]
-        {
-            usage-requirements = $(targets[1]) ;
-            targets = $(targets[2-]) ;
-        }
-        else
-        {
-            usage-requirements = [ property-set.empty ] ;
-        }
-    }
-
-    generators.dout [ indent ] "  generator" [ $(generator).id ] " spawned " ;
-    generators.dout [ indent ] " " $(targets) ;
-    if $(usage-requirements)
-    {
-        generators.dout [ indent ] "  with usage requirements:" $(x) ;
-    }
-
-    if $(success)
-    {
-        return $(usage-requirements) $(targets) ;
-    }
-}
-
-
-# Checks if generator invocation can be pruned, because it is guaranteed to
-# fail. If so, quickly returns an empty list. Otherwise, calls
-# try-one-generator-really.
-#
-local rule try-one-generator ( project name ? : generator : target-type
-    : property-set : sources * )
-{
-    local source-types ;
-    for local s in $(sources)
-    {
-        source-types += [ $(s).type ] ;
-    }
-    local viable-source-types = [ viable-source-types-for-generator $(generator)
-        ] ;
-
-    if  $(source-types) && $(viable-source-types) != * &&
-        ! [ set.intersection $(source-types) : $(viable-source-types) ]
-    {
-        local id = [ $(generator).id ] ;
-        generators.dout [ indent ] "  ** generator '$(id)' pruned" ;
-        #generators.dout [ indent ] "source-types" '$(source-types)' ;
-        #generators.dout [ indent ] "viable-source-types" '$(viable-source-types)' ;
-    }
-    else
-    {
-        return [ try-one-generator-really $(project) $(name) : $(generator) :
-            $(target-type) : $(property-set) : $(sources) ] ;
-    }
-}
-
-
-rule construct-types ( project name ? : target-types + : property-set
-    : sources + )
-{
-    local result ;
-    local matched-types ;
-    local usage-requirements = [ property-set.empty ] ;
-    for local t in $(target-types)
-    {
-        local r = [ construct $(project) $(name) : $(t) : $(property-set) :
-            $(sources) ] ;
-        if $(r)
-        {
-            usage-requirements = [ $(usage-requirements).add $(r[1]) ] ;
-            result += $(r[2-]) ;
-            matched-types += $(t) ;
-        }
-    }
-    # TODO: have to introduce parameter controlling if several types can be
-    # matched and add appropriate checks.
-
-    # TODO: need to review the documentation for 'construct' to see if it should
-    # return $(source) even if nothing can be done with it. Currents docs seem
-    # to imply that, contrary to the behaviour.
-    if $(result)
-    {
-        return $(usage-requirements) $(result) ;
-    }
-    else
-    {
-        return $(usage-requirements) $(sources) ;
-    }
-}
-
-
-# Ensures all 'targets' have their type. If this is not so, exists with error.
-#
-local rule ensure-type ( targets * )
-{
-    for local t in $(targets)
-    {
-        if ! [ $(t).type ]
-        {
-            errors.error "target" [ $(t).str ] "has no type" ;
-        }
-    }
-}
-
-
-# Returns generators which can be used to construct target of specified type
-# with specified properties. Uses the following algorithm:
-# - iterates over requested target-type and all its bases (in the order returned
-#   by type.all-bases).
-# - for each type find all generators that generate that type and whose
-#   requirements are satisfied by properties.
-# - if the set of generators is not empty, returns that set.
-#
-# Note: this algorithm explicitly ignores generators for base classes if there
-# is at least one generator for the requested target-type.
-#
-local rule find-viable-generators-aux ( target-type : property-set )
-{
-    # Select generators that can create the required target type.
-    local viable-generators = ;
-    local generator-rank = ;
-
-    import type ;
-    local t = [ type.all-bases $(target-type) ] ;
-
-    generators.dout [ indent ] find-viable-generators target-type= $(target-type)
-        property-set= [ $(property-set).as-path ] ;
-
-    # Get the list of generators for the requested type. If no generator is
-    # registered, try base type, and so on.
-    local generators ;
-    while $(t[1])
-    {
-        generators.dout [ indent ] "trying type" $(t[1]) ;
-        if $(.generators.$(t[1]))
-        {
-            generators.dout [ indent ] "there are generators for this type" ;
-            generators = $(.generators.$(t[1])) ;
-
-            if $(t[1]) != $(target-type)
-            {
-                # We are here because there were no generators found for
-                # target-type but there are some generators for its base type.
-                # We will try to use them, but they will produce targets of
-                # base type, not of 'target-type'. So, we clone the generators
-                # and modify the list of target types.
-                local generators2 ;
-                for local g in $(generators)
-                {
-                    # generators.register adds a generator to the list of
-                    # generators for toolsets, which is a bit strange, but
-                    # should work. That list is only used when inheriting a
-                    # toolset, which should have been done before running
-                    # generators.
-                    generators2 += [ $(g).clone-and-change-target-type $(t[1]) :
-                        $(target-type) ] ;
-                    generators.register $(generators2[-1]) ;
-                }
-                generators = $(generators2) ;
-            }
-            t = ;
-        }
-        t = $(t[2-]) ;
-    }
-
-    for local g in $(generators)
-    {
-        generators.dout [ indent ] "trying generator" [ $(g).id ] "(" [ $(g).source-types ] -> [ $(g).target-types ] ")" ;
-
-        local m = [ $(g).match-rank $(property-set) ] ;
-        if $(m)
-        {
-            generators.dout [ indent ] "  is viable" ;
-            viable-generators += $(g) ;
-        }
-    }
-
-    return $(viable-generators) ;
-}
-
-
-rule find-viable-generators ( target-type : property-set )
-{
-    local key = $(target-type).$(property-set) ;
-    local l = $(.fv.$(key)) ;
-    if ! $(l)
-    {
-        l = [ find-viable-generators-aux $(target-type) : $(property-set) ] ;
-        if ! $(l)
-        {
-            l = none ;
-        }
-        .fv.$(key) = $(l) ;
-    }
-
-    if $(l) = none
-    {
-        l = ;
-    }
-
-    local viable-generators ;
-    for local g in $(l)
-    {
-        # Avoid trying the same generator twice on different levels.
-        if ! $(g) in $(.active-generators)
-        {
-            viable-generators += $(g) ;
-        }
-        else
-        {
-            generators.dout [ indent ] "   generator " [ $(g).id ] "is active, discaring" ;
-        }        
-    }
-
-    # Generators which override 'all'.
-    local all-overrides ;
-    # Generators which are overriden.
-    local overriden-ids ;
-    for local g in $(viable-generators)
-    {
-        local id = [ $(g).id ] ;
-        local this-overrides = $(.override.$(id)) ;
-        overriden-ids += $(this-overrides) ;
-        if all in $(this-overrides)
-        {
-            all-overrides += $(g) ;
-        }
-    }
-    if $(all-overrides)
-    {
-        viable-generators = $(all-overrides) ;
-    }
-    local result ;
-    for local g in $(viable-generators)
-    {
-        if ! [ $(g).id ] in $(overriden-ids)
-        {
-            result += $(g) ;
-        }
-    }
-
-    return $(result) ;
-}
-
-
-.construct-stack = ;
-
-
-# Attempts to construct a target by finding viable generators, running them and
-# selecting the dependency graph.
-#
-local rule construct-really ( project name ? : target-type : property-set :
-    sources * )
-{
-    viable-generators = [ find-viable-generators $(target-type) :
-        $(property-set) ] ;
-
-    generators.dout [ indent ] "*** " [ sequence.length $(viable-generators) ]
-        " viable generators" ;
-
-    local result ;
-    local generators-that-succeeded ;
-    for local g in $(viable-generators)
-    {
-        # This variable will be restored on exit from this scope.
-        local .active-generators = $(g) $(.active-generators) ;
-
-        local r = [ try-one-generator $(project) $(name) : $(g) : $(target-type)
-            : $(property-set) : $(sources) ] ;
-
-        if $(r)
-        {
-            generators-that-succeeded += $(g) ;
-            if $(result)
-            {
-                ECHO "Error: ambiguity found when searching for best transformation" ;
-                ECHO "Trying to produce type '$(target-type)' from: " ;
-                for local s in $(sources)
-                {
-                    ECHO " - " [ $(s).str ] ;
-                }
-                ECHO "Generators that succeeded:" ;
-                for local g in $(generators-that-succeeded)
-                {
-                    ECHO " - " [ $(g).id ] ;
-                }
-                ECHO "First generator produced: " ;
-                for local t in $(result[2-])
-                {
-                    ECHO " - " [ $(t).str ] ;
-                }
-                ECHO "Second generator produced: " ;
-                for local t in $(r[2-])
-                {
-                    ECHO " - " [ $(t).str ] ;
-                }
-                EXIT ;
-            }
-            else
-            {
-                result = $(r) ;
-            }
-        }
-    }
-
-    return $(result) ;
-}
-
-
-# Attempts to create a target of 'target-type' with 'properties' from 'sources'.
-# The 'sources' are treated as a collection of *possible* ingridients, i.e.
-# there is no obligation to consume them all.
-#
-# Returns a list of targets. When this invocation is first instance of
-# 'construct' in stack, returns only targets of requested 'target-type',
-# otherwise, returns also unused sources and additionally generated targets.
-#
-# If 'top-level' is set, does not suppress generators that are already
-# used in the stack. This may be useful in cases where a generator
-# has to build a metatargets -- for example a target corresponding to
-# built tool.
-#
-rule construct ( project name ? : target-type : property-set * : sources * : top-level ? )
-{
-    local saved-stack ;
-    if $(top-level)
-    {
-        saved-active = $(.active-generators) ;
-        .active-generators = ;
-    }
-        
-    if (.construct-stack)
-    {
-        ensure-type $(sources) ;
-    }
-
-    .construct-stack += 1 ;
-
-    increase-indent ;
-
-    if $(.debug)
-    {
-        generators.dout [ indent ] "*** construct" $(target-type) ;
-
-        for local s in $(sources)
-        {
-            generators.dout [ indent ] "    from" $(s) ;
-        }
-        generators.dout [ indent ] "    properties:" [ $(property-set).raw ] ;
-    }
-
-    local result = [ construct-really $(project) $(name) : $(target-type) :
-        $(property-set) : $(sources) ] ;
-
-    decrease-indent ;
-
-    .construct-stack = $(.construct-stack[2-]) ;
-    
-    if $(top-level)
-    {
-        .active-generators = $(saved-active) ;
-    }
-
-    return $(result) ;
-}
-
-# Given 'result', obtained from some generator or generators.construct, adds
-# 'raw-properties' as usage requirements to it. If result already contains usage
-# requirements -- that is the first element of result of an instance of the
-# property-set class, the existing usage requirements and 'raw-properties' are
-# combined.
-#
-rule add-usage-requirements ( result * : raw-properties * )
-{
-    if $(result)
-    {
-        if [ class.is-a $(result[1]) : property-set ]
-        {
-            return [ $(result[1]).add-raw $(raw-properties) ] $(result[2-]) ;
-        }
-        else
-        {
-            return [ property-set.create $(raw-properties) ] $(result) ;
-        }
-    }
-}
-
-rule dump ( )
-{
-    for local g in $(.all-generators)
-    {
-        ECHO [ $(g).id ] ":" [ $(g).source-types ] -> [ $(g).target-types ] ;            
-    }    
-}
-