source: downloads/boost_1_34_1/tools/build/v2/kernel/bootstrap.jam @ 69

# Copyright 2003 Dave Abrahams 
# Copyright 2003, 2005, 2006 Rene Rivera 
# Copyright 2003, 2005, 2006 Vladimir Prus 
# Distributed under the Boost Software License, Version 1.0. 
# (See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt) 

# First of all, check the jam version

if $(JAM_VERSION:J="") < 030112
{
    ECHO "error: Boost.Jam version 3.1.12 or later required" ;
    EXIT ;
}

local required-rules = GLOB-RECURSIVELY HAS_NATIVE_RULE ;

for local r in $(required-rules)
{
    if ! $(r) in [ RULENAMES ]
    {
        ECHO "error: builtin rule '$(r)' is not present" ;
        ECHO "error: your version of bjam is likely out of date" ;
        ECHO "error: please get a fresh version from CVS." ;
        EXIT ;
    }
}

local native =
    regex transform 2
    ;
while $(native)
{
    if ! [ HAS_NATIVE_RULE $(native[1]) :
                           $(native[2]) :
               $(native[3]) ]
    {
        ECHO "error: missing native rule '$(native[1]).$(native[2])'" ;
        ECHO "error: or interface version of that rule is too low" ;
        ECHO "error: your version of bjam is likely out of date" ;
        ECHO "error: please get a fresh version from CVS." ;
        EXIT ;
    }
    native = $(native[4-]) ;
}

# Check that the builtin .ENVIRON module is present. We don't have a
# builtin to check that a module is present, so we assume that the PATH
# environment variable is always set and verify that the .ENVIRON module
# has non-empty value of that variable.
module .ENVIRON
{
    local p = $(PATH) $(Path) $(path) ;
    if ! $(p)
    {
        ECHO "error: no builtin module .ENVIRON is found" ;
        ECHO "error: your version of bjam is likely out of date" ;
        ECHO "error: please get a fresh version from CVS." ;
        EXIT ;
    }
}

# Check that @() functionality is present. Similarly to modules,
# we don't have a way to test that directly. Instead we check that
# $(TMPNAME) functionality is present which was added at roughly
# the same time (more precisely it was added just before).
{
    if ! $(TMPNAME)
    {
        ECHO "error: no @() functionality found" ;
        ECHO "error: your version of bjam is likely out of date" ;
        ECHO "error: please get a fresh version from CVS." ;
        EXIT ;
    }
}



# Bootstrap the module system. Then bring the import rule into the global module.
#
SEARCH on <module@>modules.jam = $(.bootstrap-file:D) ;
module modules { include <module@>modules.jam ; }
IMPORT modules : import : : import ;

{
    # Add module subdirectories to the BOOST_BUILD_PATH, which allows
    # us to make an incremental refactoring step by moving modules to
    # the appropriate subdirectories, thereby achieving some physical
    # separation of different layers without changing all of our code
    # to specify subdirectories in import statements or use an extra
    # level of qualification on imported names.

    local subdirs =
      kernel        # only the most-intrinsic modules: modules, errors
      util          # low-level substrate: string/number handling, etc.
      build         # essential elements of the build system architecture
      tools         # toolsets for handling specific build jobs and targets.

      new           # until we get everything sorted out, there is
                    # still some code here

      .             # build-system.jam lives here

      ;
    local whereami = [ NORMALIZE_PATH $(.bootstrap-file:DT) ] ;
    BOOST_BUILD_PATH += $(whereami:D)/$(subdirs) ;

    modules.poke .ENVIRON : BOOST_BUILD_PATH : $(BOOST_BUILD_PATH) ;
}

# Reload the modules, to clean up things. The modules module can tolerate
# being included twice.
#
import modules ;

# Process option plugins first to alow them to prevent loading
# the rest of the build system.
#
import option ;
local dont-build = [ option.process ] ;

# Should we skip building, i.e. loding the build system, according
# to the options processed?
#
if ! $(dont-build)
{
    # Allow users to override the build system file from the
    # command-line (mostly for testing)
    local build-system = [ MATCH --build-system=(.*) : $(ARGV) ] ;
    build-system ?= build-system ;

    # Use last element in case of multiple command-line options
    import $(build-system[-1]) ;
}