build-system.jam

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    local test-config = [ MATCH ^--test-config=(.*)$ : $(.argv) ] ;
    local uq = [ MATCH \"(.*)\" : $(test-config) ] ;
    if $(uq)
    {
        test-config = $(uq) ;
    }
    if $(test-config)
    {
        local where =
            [ load-config test-config : $(test-config:BS) : $(test-config:D) ] ;
        if $(where)
        {
            if $(.debug-config) && ! $(.legacy-ignore-config)
            {
                ECHO "notice: Regular site and user configuration files will" ;
                ECHO "notice: be ignored due to the test configuration being"
                    "loaded." ;
            }
        }
        else
        {
            test-config = ;
        }
    }

    local user-path = [ os.home-directories ] [ os.environ BOOST_BUILD_PATH ] ;
    local site-path = /etc $(user-path) ;
    if [ os.name ] in NT CYGWIN
    {
        site-path = [ modules.peek : SystemRoot ] $(user-path) ;
    }

    if $(ignore-site-config) && !$(.legacy-ignore-config)
    {
        ECHO "notice: Site configuration files will be ignored due to the" ;
        ECHO "notice: --ignore-site-config command-line option." ;
    }

    initialize-config-module site-config ;
    if ! $(test-config) && ! $(ignore-site-config) && ! $(.legacy-ignore-config)
    {
        load-config site-config : site-config.jam : $(site-path) ;
    }

    initialize-config-module user-config ;
    if ! $(test-config) && ! $(.legacy-ignore-config)
    {
        local user-config = [ MATCH ^--user-config=(.*)$ : $(.argv) ] ;
        user-config = $(user-config[-1]) ;
        user-config ?= [ os.environ BOOST_BUILD_USER_CONFIG ] ;
        # Special handling for the case when the OS does not strip the quotes
        # around the file name, as is the case when using Cygwin bash.
        user-config = [ utility.unquote $(user-config) ] ;
        local explicitly-requested = $(user-config) ;
        user-config ?= user-config.jam ;

        if $(user-config)
        {
            if $(explicitly-requested)
            {
                # Treat explicitly entered user paths as native OS path
                # references and, if non-absolute, root them at the current
                # working directory.
                user-config = [ path.make $(user-config) ] ;
                user-config = [ path.root $(user-config) [ path.pwd ] ] ;
                user-config = [ path.native $(user-config) ] ;

                if $(.debug-config)
                {
                    ECHO "notice: Loading explicitly specified user"
                        "configuration file:" ;
                    ECHO "    $(user-config)" ;
                }

                load-config user-config : $(user-config:BS) : $(user-config:D)
                    : must-exist ;
            }
            else
            {
                load-config user-config : $(user-config) : $(user-path) ;
            }
        }
        else if $(.debug-config)
        {
            ECHO "notice: User configuration file loading explicitly disabled." ;
        }
    }
}


# Autoconfigure toolsets based on any instances of --toolset=xx,yy,...zz or
# toolset=xx,yy,...zz in the command line. May return additional properties to
# be processed as if they had been specified by the user.
#
local rule process-explicit-toolset-requests
{
    local extra-properties ;

    local option-toolsets  = [ regex.split-list [ MATCH ^--toolset=(.*)$ : $(.argv) ] : "," ] ;
    local feature-toolsets = [ regex.split-list [ MATCH   ^toolset=(.*)$ : $(.argv) ] : "," ] ;

    for local t in $(option-toolsets) $(feature-toolsets)
    {
        # Parse toolset-version/properties.
        local (t-v,t,v) = [ MATCH (([^-/]+)-?([^/]+)?)/?.* : $(t) ] ;
        local toolset-version = $((t-v,t,v)[1]) ;
        local toolset = $((t-v,t,v)[2]) ;
        local version = $((t-v,t,v)[3]) ;

        if $(.debug-config)
        {
            ECHO notice: [cmdline-cfg] Detected command-line request for
                $(toolset-version): "toolset=" $(toolset) "version="
                $(version) ;
        }

        # If the toolset is not known, configure it now.
        local known ;
        if $(toolset) in [ feature.values <toolset> ]
        {
            known = true ;
        }
        if $(known) && $(version) && ! [ feature.is-subvalue toolset
            : $(toolset) : version : $(version) ]
        {
            known = ;
        }
        # TODO: we should do 'using $(toolset)' in case no version has been
        # specified and there are no versions defined for the given toolset to
        # allow the toolset to configure its default version. For this we need
        # to know how to detect whether a given toolset has any versions
        # defined. An alternative would be to do this whenever version is not
        # specified but that would require that toolsets correctly handle the
        # case when their default version is configured multiple times which
        # should be checked for all existing toolsets first.

        if ! $(known)
        {
            if $(.debug-config)
            {
                ECHO notice: [cmdline-cfg] toolset $(toolset-version) not
                    previously configured; attempting to auto-configure now ;
            }
            toolset.using $(toolset) : $(version) ;
        }
        else
        {
            if $(.debug-config)
            {
                ECHO notice: [cmdline-cfg] toolset $(toolset-version) already
                    configured ;
            }
        }

        # Make sure we get an appropriate property into the build request in
        # case toolset has been specified using the "--toolset=..." command-line
        # option form.
        if ! $(t) in $(.argv) && ! $(t) in $(feature-toolsets)
        {
            if $(.debug-config)
            {
                ECHO notice: [cmdline-cfg] adding toolset=$(t) to the build
                    request. ;
            }
            extra-properties += toolset=$(t) ;
        }
    }

    return $(extra-properties) ;
}


# Returns 'true' if the given 'project' is equal to or is a (possibly indirect)
# child to any of the projects requested to be cleaned in this build system run.
# Returns 'false' otherwise. Expects the .project-targets list to have already
# been constructed.
#
local rule should-clean-project ( project )
{
    if ! $(.should-clean-project.$(project))
    {
        local r = false ;
        if $(project) in $(.project-targets)
        {
            r = true ;
        }
        else
        {
            local parent = [ project.attribute $(project) parent-module ] ;
            if $(parent) && $(parent) != user-config
            {
                r = [ should-clean-project $(parent) ] ;
            }
        }
        .should-clean-project.$(project) = $(r) ;
    }

    return $(.should-clean-project.$(project)) ;
}


################################################################################
#
# main()
# ------
#
################################################################################

{
    if --version in $(.argv)
    {
        version.print ;
        EXIT ;
    }


    load-configuration-files ;

    local extra-properties ;
    # Note that this causes --toolset options to be ignored if --ignore-config
    # is specified.
    if ! $(.legacy-ignore-config)
    {
        extra-properties = [ process-explicit-toolset-requests ] ;
    }


    # We always load project in "." so that 'use-project' directives have any
    # chance of being seen. Otherwise, we would not be able to refer to
    # subprojects using target ids.
    local current-project ;
    if [ project.find "." : "." ]
    {
        current-project = [ project.target [ project.load "." ] ] ;
    }


    # In case there are no toolsets currently defined makes the build run using
    # the default toolset.
    if ! $(.legacy-ignore-config) && ! [ feature.values <toolset> ]
    {
        local default-toolset = $(.default-toolset) ;
        local default-toolset-version = ;
        if $(default-toolset)
        {
            default-toolset-version = $(.default-toolset-version) ;
        }
        else
        {
            default-toolset = gcc ;
            if [ os.name ] = NT
            {
                default-toolset = msvc ;
            }
        }

        ECHO "warning: No toolsets are configured." ;
        ECHO "warning: Configuring default toolset" \"$(default-toolset)\". ;
        ECHO "warning: If the default is wrong, your build may not work correctly." ;
        ECHO "warning: Use the \"toolset=xxxxx\" option to override our guess." ;
        ECHO "warning: For more configuration options, please consult" ;
        ECHO "warning: http://boost.org/boost-build2/doc/html/bbv2/advanced/configuration.html" ;

        toolset.using $(default-toolset) : $(default-toolset-version) ;
    }


    # Parse command line for targets and properties. Note that this requires
    # that all project files already be loaded.
    local build-request = [ build-request.from-command-line $(.argv)
        $(extra-properties) ] ;
    local target-ids = [ $(build-request).get-at 1 ] ;
    local properties = [ $(build-request).get-at 2 ] ;


    # Expand properties specified on the command line into multiple property
    # sets consisting of all legal property combinations. Each expanded property
    # set will be used for a single build run. E.g. if multiple toolsets are
    # specified then requested targets will be built with each of them.
    if $(properties)
    {
        expanded = [ build-request.expand-no-defaults $(properties) ] ;
        local xexpanded ;
        for local e in $(expanded)
        {
            xexpanded += [ property-set.create [ feature.split $(e) ] ] ;
        }
        expanded = $(xexpanded) ;
    }
    else
    {
        expanded = [ property-set.empty ] ;
    }


    # Check that we actually found something to build.
    if ! $(current-project) && ! $(target-ids)
    {
        errors.user-error "error: no Jamfile in current directory found, and no"
            "target references specified." ;
        EXIT ;
    }