targets.jam

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            ECHO [ targets.indent ] "Build request: " $(property-set) [ $(property-set).raw ] ;
            local cf = [ build-system.command-line-free-features ] ;
            ECHO [ targets.indent ] "Command line free features: " [ $(cf).raw ] ;
            ECHO [ targets.indent ] "Target requirements: " [ $(self.requirements).raw ] ;
        }

        if ! $(self.generated.$(property-set))
        {
            # Apply free features from the command line. If user said
            #   define=FOO
            # he most likely wants this define to be set for all compiles.
            property-set = [ $(property-set).refine
                [ build-system.command-line-free-features ] ] ;
            local rproperties = [ targets.common-properties $(property-set)
                $(self.requirements) ] ;

            if [ modules.peek : .debug-building ]
            {
                ECHO ;
                ECHO [ targets.indent ] "Common properties: " [ $(rproperties).raw ] ;
            }

            if ( $(rproperties[1]) != "@error" ) && ( [ $(rproperties).get
                <build> ] != no )
            {
                local source-targets ;
                local properties = [ $(rproperties).non-dependency ] ;
                local usage-requirements ;

                generate-dependencies [ $(rproperties).dependency ] :
                    $(rproperties) : properties usage-requirements ;

                generate-dependencies $(self.sources) : $(rproperties) :
                    source-targets usage-requirements ;

                if [ modules.peek : .debug-building ]
                {
                    ECHO ;
                    ECHO [ targets.indent ] "Usage requirements for"
                        $(self.name)": " $(usage-requirements) ;
                }

                rproperties = [ property-set.create $(properties)
                    $(usage-requirements) ] ;
                usage-requirements = [ property-set.create $(usage-requirements) ] ;

                if [ modules.peek : .debug-building ]
                {
                    ECHO [ targets.indent ] "Build properties: "
                        [ $(rproperties).raw ] ;
                }

                local extra = [ $(rproperties).get <source> ] ;
                source-targets += $(extra:G=) ;
                # We might get duplicate sources, for example if we link to two
                # libraries having the same <library> usage requirement.
                source-targets = [ sequence.unique $(source-targets) ] ;

                local result = [ construct $(self.name) : $(source-targets) :
                    $(rproperties) ] ;

                if $(result)
                {
                    local gur = $(result[1]) ;
                    result = $(result[2-]) ;

                    local s = [ create-subvariant $(result)
                        : [ virtual-target.recent-targets ]
                        : $(property-set) : $(source-targets)
                        : $(rproperties) : $(usage-requirements) ] ;
                    virtual-target.clear-recent-targets ;

                    local ur = [ compute-usage-requirements $(s) ] ;
                    ur = [ $(ur).add $(gur) ] ;
                    $(s).set-usage-requirements $(ur) ;
                    if [ modules.peek : .debug-building ]
                    {
                        ECHO [ targets.indent ] "Usage requirements from"
                            $(self.name)": " [ $(ur).raw ] ;
                    }

                    self.generated.$(property-set) = $(ur) $(result) ;
                }
            }
            else
            {
                if $(rproperties[1]) = "@error"
                {
                    ECHO [ targets.indent ] "Skipping build of:" [ full-name ]
                        "cannot compute common properties" ;
                }
                else if [ $(rproperties).get <build> ] = no
                {
                    ECHO [ targets.indent ] "Skipping build of: " [ full-name ]
                        " <build>no in common properties" ;
                }
                else
                {
                    ECHO [ targets.indent ] "Skipping build of: " [ full-name ]
                        " unknown reason" ;
                }

                # We are here either because there has been an error computing
                # properties or there is <build>no in properties. In the latter
                # case we do not want any diagnostic. In the former case, we
                # need diagnostics. FIXME

                # If this target fails to build, add <build>no to properties to
                # cause any parent target to fail to build. Except that it
                # - does not work now, since we check for <build>no only in
                #   common properties, but not in properties that came from
                #   dependencies
                # - it is not clear if that is a good idea anyway. The alias
                #   target, for example, should not fail to build if a
                #   dependency fails.
                self.generated.$(property-set) = [ property-set.create <build>no ] ;
            }
        }
        else
        {
            if [ modules.peek : .debug-building ]
            {
                ECHO [ targets.indent ] "Already built" ;
                local ur = $(self.generated.$(property-set)) ;
                ur = $(ur[0]) ;
                targets.increase-indent ;
                ECHO [ targets.indent ] "Usage requirements from"
                    $(self.name)": " [ $(ur).raw ] ;
                targets.decrease-indent ;
            }
        }

        targets.decrease-indent ;
        return $(self.generated.$(property-set)) ;
    }

    # Given the set of generated targets, and refined build properties,
    # determines and sets appropriate usage requirements on those targets.
    #
    rule compute-usage-requirements ( subvariant )
    {
        local rproperties = [ $(subvariant).build-properties ] ;
        xusage-requirements = [ targets.evaluate-requirements
            $(self.usage-requirements) : $(rproperties) : added ] ;

        # We generate all dependency properties and add them, as well as their
        # usage requirements, to the result.
        local extra ;
        generate-dependencies [ $(xusage-requirements).dependency ] :
            $(rproperties) : extra extra ;

        local result = [ property-set.create
            [ $(xusage-requirements).non-dependency ] $(extra) ] ;

        # Propagate usage requirements we got from sources, except for the
        # <pch-header> and <pch-file> features.
        #
        # That feature specifies which pch file to use, and should apply only to
        # direct dependents. Consider:
        #
        #   pch pch1 : ...
        #   lib lib1 : ..... pch1 ;
        #   pch pch2 :
        #   lib lib2 : pch2 lib1 ;
        #
        # Here, lib2 should not get <pch-header> property from pch1.
        #
        # Essentially, when those two features are in usage requirements, they
        # are propagated only to direct dependents. We might need a more general
        # mechanism, but for now, only those two features are special.
        #
        # TODO - Actually there are more possible candidates like for instance
        # when listing static library X as a source for another static library.
        # Then static library X will be added as a <source> property to the
        # second library's usage requirements but those requirements should last
        # only up to the first executable or shared library that actually links
        # to it.
        local raw = [ $(subvariant).sources-usage-requirements ] ;
        raw = [ $(raw).raw ] ;
        raw = [ property.change $(raw) : <pch-header> ] ;
        raw = [ property.change $(raw) : <pch-file> ] ;
        return [ $(result).add [ property-set.create $(raw) ] ] ;
    }

    # Creates new subvariant instances for 'targets'.
    # 'root-targets'  - virtual targets to be returned to dependants
    # 'all-targets'   - virtual targets created while building this main target
    # 'build-request' - property-set instance with requested build properties
    #
    local rule create-subvariant ( root-targets * : all-targets * :
        build-request : sources * : rproperties : usage-requirements )
    {
        for local e in $(root-targets)
        {
            $(e).root true ;
        }

        # Process all virtual targets that will be created if this main target
        # is created.
        local s = [ new subvariant $(__name__) : $(build-request) : $(sources) :
            $(rproperties) : $(usage-requirements) : $(all-targets) ] ;
        for local v in $(all-targets)
        {
            if ! [ $(v).creating-subvariant ]
            {
                $(v).creating-subvariant $(s) ;
            }
        }
        return $(s) ;
    }

    # Constructs virtual targets for this abstract target and the dependency
    # graph. Returns a usage-requirements property-set and a list of virtual
    # targets. Should be overriden in derived classes.
    #
    rule construct ( name : source-targets * : properties * )
    {
        errors.error "method should be defined in derived classes" ;
    }
}


class typed-target : basic-target
{
    import generators ;

    rule __init__ ( name : project : type : sources * : requirements * :
         default-build * : usage-requirements * )
    {
        basic-target.__init__ $(name) : $(project) : $(sources) :
            $(requirements) : $(default-build) : $(usage-requirements) ;

        self.type = $(type) ;
    }

    rule type ( )
    {
        return $(self.type) ;
    }

    rule construct ( name : source-targets * : property-set )
    {
        local r = [ generators.construct $(self.project) $(name:S=) : $(self.type)
            : [ property-set.create [ $(property-set).raw ]
                <main-target-type>$(self.type) ]
            : $(source-targets) ] ;
        if ! $(r)
        {
            ECHO "warn: Unable to construct" [ full-name ] ;

            # Are there any top-level generators for this type/property set.
            if ! [ generators.find-viable-generators $(self.type)
                : $(property-set) ]
            {
                ECHO "error: no generators were found for type '$(self.type)'" ;
                ECHO "error: and the requested properties" ;
                ECHO "error: make sure you've configured the needed tools" ;
                ECHO "See http://boost.org/boost-build2/doc/html/bbv2/advanced/configuration.html" ;
                ECHO "To debug this problem, try the --debug-generators option." ;
                EXIT ;
            }
        }
        return $(r) ;
    }
}


# Return the list of sources to use, if main target rule is invoked with
# 'sources'. If there are any objects in 'sources', they are treated as main
# target instances, and the name of such targets are adjusted to be
# '<name_of_this_target>__<name_of_source_target>'. Such renaming is disabled if
# a non-empty value is passed as the 'no-renaming' parameter.
#
rule main-target-sources ( sources * : main-target-name : no-renaming ? )
{
    local result ;
    for local t in $(sources)
    {
        if [ class.is-instance $(t) ]
        {
            local name = [ $(t).name ] ;
            if ! $(no-renaming)
            {
                name = $(main-target-name)__$(name) ;
                $(t).rename $(name) ;
            }
            # Inline targets are not built by default.
            local p = [ $(t).project ] ;
            $(p).mark-target-as-explicit $(name) ;
            result += $(name) ;
        }
        else
        {
            result += $(t) ;
        }
    }
    return $(result) ;
}


# Returns the requirements to use when declaring a main target, obtained by
# translating all specified property paths and refining project requirements
# with the ones specified for the target.
#
rule main-target-requirements (
    specification *  # Properties explicitly specified for the main target.
    : project        # Project where the main target is to be declared.
)
{
    specification += [ toolset.requirements ] ;

    local requirements = [ property-set.refine-from-user-input
        [ $(project).get requirements ] : $(specification) :
        [ $(project).project-module ] : [ $(project).get location ] ] ;
    if $(requirements[1]) = "@error"
    {
        errors.error "Conflicting requirements for target:" $(requirements) ;
    }
    return $(requirements) ;
}


# Returns the usage requirements to use when declaring a main target, which are
# obtained by translating all specified property paths and adding project's
# usage requirements.
#
rule main-target-usage-requirements (
    specification *  # Use-properties explicitly specified for a main target.
    : project        # Project where the main target is to be declared.
)
{
    local project-usage-requirements = [ $(project).get usage-requirements ] ;

    # We do not use 'refine-from-user-input' because:
    # - I am not sure if removing parent's usage requirements makes sense
    # - refining usage requirements is not needed, since usage requirements are
    #   always free.
    local usage-requirements = [ property-set.create-from-user-input
        $(specification)
        : [ $(project).project-module ] [ $(project).get location ] ] ;

    return [ $(project-usage-requirements).add $(usage-requirements) ] ;
}


# Return the default build value to use when declaring a main target, which is
# obtained by using the specified value if not empty and parent's default build
# attribute otherwise.
#
rule main-target-default-build (
    specification *  # Default build explicitly specified for a main target.
    : project        # Project where the main target is to be declared.
)
{
    local result ;
    if $(specification)
    {
        result = $(specification) ;
    }
    else
    {
        result = [ $(project).get default-build ] ;
    }
    return [ property-set.create-with-validation $(result) ] ;
}


# Registers the specified target as a main target alternative and returns it.
#
rule main-target-alternative ( target )
{
    local ptarget = [ $(target).project ] ;
    $(ptarget).add-alternative $(target) ;
    return $(target) ;
}


# Creates a typed-target with the specified properties. The 'name', 'sources',
# 'requirements', 'default-build' and 'usage-requirements' are assumed to be in
# the form specified by the user in Jamfile corresponding to 'project'.
#
rule create-typed-target ( type : project : name : sources * : requirements * :
    default-build * : usage-requirements * )
{
    return [
        targets.main-target-alternative
        [ new typed-target $(name) : $(project) : $(type)
            : [ targets.main-target-sources $(sources) : $(name) ]
            : [ targets.main-target-requirements $(requirements) : $(project) ]
            : [ targets.main-target-default-build $(default-build) : $(project) ]
            : [ targets.main-target-usage-requirements $(usage-requirements) : $(project) ]
        ] ] ;
}