Added an unmodified copy of SCons to third_party.

scons-2.0.1/engine/SCons/SConf.py

+"""SCons.SConf
+
+Autoconf-like configuration support.
+"""
+
+#
+# Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 The SCons Foundation
+#
+# Permission is hereby granted, free of charge, to any person obtaining
+# a copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+#
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
+# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
+# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+#
+
+__revision__ = "src/engine/SCons/SConf.py 5134 2010/08/16 23:02:40 bdeegan"
+
+import SCons.compat
+
+import io
+import os
+import re
+import sys
+import traceback
+
+import SCons.Action
+import SCons.Builder
+import SCons.Errors
+import SCons.Job
+import SCons.Node.FS
+import SCons.Taskmaster
+import SCons.Util
+import SCons.Warnings
+import SCons.Conftest
+
+from SCons.Debug import Trace
+
+# Turn off the Conftest error logging
+SCons.Conftest.LogInputFiles = 0
+SCons.Conftest.LogErrorMessages = 0
+
+# Set
+build_type = None
+build_types = ['clean', 'help']
+
+def SetBuildType(type):
+    global build_type
+    build_type = type
+
+# to be set, if we are in dry-run mode
+dryrun = 0
+
+AUTO=0  # use SCons dependency scanning for up-to-date checks
+FORCE=1 # force all tests to be rebuilt
+CACHE=2 # force all tests to be taken from cache (raise an error, if necessary)
+cache_mode = AUTO
+
+def SetCacheMode(mode):
+    """Set the Configure cache mode. mode must be one of "auto", "force",
+    or "cache"."""
+    global cache_mode
+    if mode == "auto":
+        cache_mode = AUTO
+    elif mode == "force":
+        cache_mode = FORCE
+    elif mode == "cache":
+        cache_mode = CACHE
+    else:
+        raise ValueError("SCons.SConf.SetCacheMode: Unknown mode " + mode)
+
+progress_display = SCons.Util.display # will be overwritten by SCons.Script
+def SetProgressDisplay(display):
+    """Set the progress display to use (called from SCons.Script)"""
+    global progress_display
+    progress_display = display
+
+SConfFS = None
+
+_ac_build_counter = 0 # incremented, whenever TryBuild is called
+_ac_config_logs = {}  # all config.log files created in this build
+_ac_config_hs   = {}  # all config.h files created in this build
+sconf_global = None   # current sconf object
+
+def _createConfigH(target, source, env):
+    t = open(str(target[0]), "w")
+    defname = re.sub('[^A-Za-z0-9_]', '_', str(target[0]).upper())
+    t.write("""#ifndef %(DEFNAME)s_SEEN
+#define %(DEFNAME)s_SEEN
+
+""" % {'DEFNAME' : defname})
+    t.write(source[0].get_contents())
+    t.write("""
+#endif /* %(DEFNAME)s_SEEN */
+""" % {'DEFNAME' : defname})
+    t.close()
+
+def _stringConfigH(target, source, env):
+    return "scons: Configure: creating " + str(target[0])
+
+def CreateConfigHBuilder(env):
+    """Called just before the building targets phase begins."""
+    if len(_ac_config_hs) == 0:
+        return
+    action = SCons.Action.Action(_createConfigH,
+                                 _stringConfigH)
+    sconfigHBld = SCons.Builder.Builder(action=action)
+    env.Append( BUILDERS={'SConfigHBuilder':sconfigHBld} )
+    for k in _ac_config_hs.keys():
+        env.SConfigHBuilder(k, env.Value(_ac_config_hs[k]))
+    
+class SConfWarning(SCons.Warnings.Warning):
+    pass
+SCons.Warnings.enableWarningClass(SConfWarning)
+
+# some error definitions
+class SConfError(SCons.Errors.UserError):
+    def __init__(self,msg):
+        SCons.Errors.UserError.__init__(self,msg)
+
+class ConfigureDryRunError(SConfError):
+    """Raised when a file or directory needs to be updated during a Configure
+    process, but the user requested a dry-run"""
+    def __init__(self,target):
+        if not isinstance(target, SCons.Node.FS.File):
+            msg = 'Cannot create configure directory "%s" within a dry-run.' % str(target)
+        else:
+            msg = 'Cannot update configure test "%s" within a dry-run.' % str(target)
+        SConfError.__init__(self,msg)
+
+class ConfigureCacheError(SConfError):
+    """Raised when a use explicitely requested the cache feature, but the test
+    is run the first time."""
+    def __init__(self,target):
+        SConfError.__init__(self, '"%s" is not yet built and cache is forced.' % str(target))
+
+# define actions for building text files
+def _createSource( target, source, env ):
+    fd = open(str(target[0]), "w")
+    fd.write(source[0].get_contents())
+    fd.close()
+def _stringSource( target, source, env ):
+    return (str(target[0]) + ' <-\n  |' +
+            source[0].get_contents().replace( '\n', "\n  |" ) )
+
+class SConfBuildInfo(SCons.Node.FS.FileBuildInfo):
+    """
+    Special build info for targets of configure tests. Additional members
+    are result (did the builder succeed last time?) and string, which
+    contains messages of the original build phase.
+    """
+    result = None # -> 0/None -> no error, != 0 error
+    string = None # the stdout / stderr output when building the target
+
+    def set_build_result(self, result, string):
+        self.result = result
+        self.string = string
+
+
+class Streamer(object):
+    """
+    'Sniffer' for a file-like writable object. Similar to the unix tool tee.
+    """
+    def __init__(self, orig):
+        self.orig = orig
+        self.s = io.StringIO()
+
+    def write(self, str):
+        if self.orig:
+            self.orig.write(str)
+        self.s.write(str)
+
+    def writelines(self, lines):
+        for l in lines:
+            self.write(l + '\n')
+
+    def getvalue(self):
+        """
+        Return everything written to orig since the Streamer was created.
+        """
+        return self.s.getvalue()
+
+    def flush(self):
+        if self.orig:
+            self.orig.flush()
+        self.s.flush()
+        
+
+class SConfBuildTask(SCons.Taskmaster.AlwaysTask):
+    """
+    This is almost the same as SCons.Script.BuildTask. Handles SConfErrors
+    correctly and knows about the current cache_mode.
+    """
+    def display(self, message):
+        if sconf_global.logstream:
+            sconf_global.logstream.write("scons: Configure: " + message + "\n")
+
+    def display_cached_string(self, bi):
+        """
+        Logs the original builder messages, given the SConfBuildInfo instance
+        bi.
+        """
+        if not isinstance(bi, SConfBuildInfo):
+            SCons.Warnings.warn(SConfWarning,
+              "The stored build information has an unexpected class: %s" % bi.__class__)
+        else:
+            self.display("The original builder output was:\n" +
+                         ("  |" + str(bi.string)).replace("\n", "\n  |"))
+
+    def failed(self):
+        # check, if the reason was a ConfigureDryRunError or a
+        # ConfigureCacheError and if yes, reraise the exception
+        exc_type = self.exc_info()[0]
+        if issubclass(exc_type, SConfError):
+            raise
+        elif issubclass(exc_type, SCons.Errors.BuildError):
+            # we ignore Build Errors (occurs, when a test doesn't pass)
+            # Clear the exception to prevent the contained traceback
+            # to build a reference cycle.
+            self.exc_clear()
+        else:
+            self.display('Caught exception while building "%s":\n' %
+                         self.targets[0])
+            try:
+                excepthook = sys.excepthook
+            except AttributeError:
+                # Earlier versions of Python don't have sys.excepthook...
+                def excepthook(type, value, tb):
+                    traceback.print_tb(tb)
+                    print type, value
+            excepthook(*self.exc_info())
+        return SCons.Taskmaster.Task.failed(self)
+
+    def collect_node_states(self):
+        # returns (is_up_to_date, cached_error, cachable)
+        # where is_up_to_date is 1, if the node(s) are up_to_date
+        #       cached_error  is 1, if the node(s) are up_to_date, but the
+        #                           build will fail
+        #       cachable      is 0, if some nodes are not in our cache
+        T = 0
+        changed = False
+        cached_error = False
+        cachable = True
+        for t in self.targets:
+            if T: Trace('%s' % (t))
+            bi = t.get_stored_info().binfo
+            if isinstance(bi, SConfBuildInfo):
+                if T: Trace(': SConfBuildInfo')
+                if cache_mode == CACHE:
+                    t.set_state(SCons.Node.up_to_date)
+                    if T: Trace(': set_state(up_to-date)')
+                else:
+                    if T: Trace(': get_state() %s' % t.get_state())
+                    if T: Trace(': changed() %s' % t.changed())
+                    if (t.get_state() != SCons.Node.up_to_date and t.changed()):
+                        changed = True
+                    if T: Trace(': changed %s' % changed)
+                cached_error = cached_error or bi.result
+            else:
+                if T: Trace(': else')
+                # the node hasn't been built in a SConf context or doesn't
+                # exist
+                cachable = False
+                changed = ( t.get_state() != SCons.Node.up_to_date )
+                if T: Trace(': changed %s' % changed)
+        if T: Trace('\n')
+        return (not changed, cached_error, cachable)
+
+    def execute(self):
+        if not self.targets[0].has_builder():
+            return
+
+        sconf = sconf_global
+
+        is_up_to_date, cached_error, cachable = self.collect_node_states()
+
+        if cache_mode == CACHE and not cachable:
+            raise ConfigureCacheError(self.targets[0])
+        elif cache_mode == FORCE:
+            is_up_to_date = 0
+
+        if cached_error and is_up_to_date:
+            self.display("Building \"%s\" failed in a previous run and all "
+                         "its sources are up to date." % str(self.targets[0]))
+            binfo = self.targets[0].get_stored_info().binfo
+            self.display_cached_string(binfo)
+            raise SCons.Errors.BuildError # will be 'caught' in self.failed
+        elif is_up_to_date:            
+            self.display("\"%s\" is up to date." % str(self.targets[0]))
+            binfo = self.targets[0].get_stored_info().binfo
+            self.display_cached_string(binfo)
+        elif dryrun:
+            raise ConfigureDryRunError(self.targets[0])
+        else:
+            # note stdout and stderr are the same here
+            s = sys.stdout = sys.stderr = Streamer(sys.stdout)
+            try:
+                env = self.targets[0].get_build_env()
+                if cache_mode == FORCE:
+                    # Set up the Decider() to force rebuilds by saying
+                    # that every source has changed.  Note that we still
+                    # call the environment's underlying source decider so
+                    # that the correct .sconsign info will get calculated
+                    # and keep the build state consistent.
+                    def force_build(dependency, target, prev_ni,
+                                    env_decider=env.decide_source):
+                        env_decider(dependency, target, prev_ni)
+                        return True
+                    if env.decide_source.func_code is not force_build.func_code:
+                        env.Decider(force_build)
+                env['PSTDOUT'] = env['PSTDERR'] = s
+                try:
+                    sconf.cached = 0
+                    self.targets[0].build()
+                finally:
+                    sys.stdout = sys.stderr = env['PSTDOUT'] = \
+                                 env['PSTDERR'] = sconf.logstream
+            except KeyboardInterrupt:
+                raise
+            except SystemExit:
+                exc_value = sys.exc_info()[1]
+                raise SCons.Errors.ExplicitExit(self.targets[0],exc_value.code)
+            except Exception, e:
+                for t in self.targets:
+                    binfo = t.get_binfo()
+                    binfo.__class__ = SConfBuildInfo
+                    binfo.set_build_result(1, s.getvalue())
+                    sconsign_entry = SCons.SConsign.SConsignEntry()
+                    sconsign_entry.binfo = binfo
+                    #sconsign_entry.ninfo = self.get_ninfo()
+                    # We'd like to do this as follows:
+                    #    t.store_info(binfo)
+                    # However, we need to store it as an SConfBuildInfo
+                    # object, and store_info() will turn it into a
+                    # regular FileNodeInfo if the target is itself a
+                    # regular File.
+                    sconsign = t.dir.sconsign()
+                    sconsign.set_entry(t.name, sconsign_entry)
+                    sconsign.merge()
+                raise e
+            else:
+                for t in self.targets:
+                    binfo = t.get_binfo()
+                    binfo.__class__ = SConfBuildInfo
+                    binfo.set_build_result(0, s.getvalue())
+                    sconsign_entry = SCons.SConsign.SConsignEntry()
+                    sconsign_entry.binfo = binfo
+                    #sconsign_entry.ninfo = self.get_ninfo()
+                    # We'd like to do this as follows:
+                    #    t.store_info(binfo)
+                    # However, we need to store it as an SConfBuildInfo
+                    # object, and store_info() will turn it into a
+                    # regular FileNodeInfo if the target is itself a
+                    # regular File.
+                    sconsign = t.dir.sconsign()
+                    sconsign.set_entry(t.name, sconsign_entry)
+                    sconsign.merge()
+
+class SConfBase(object):
+    """This is simply a class to represent a configure context. After
+    creating a SConf object, you can call any tests. After finished with your
+    tests, be sure to call the Finish() method, which returns the modified
+    environment.
+    Some words about caching: In most cases, it is not necessary to cache
+    Test results explicitely. Instead, we use the scons dependency checking
+    mechanism. For example, if one wants to compile a test program
+    (SConf.TryLink), the compiler is only called, if the program dependencies
+    have changed. However, if the program could not be compiled in a former
+    SConf run, we need to explicitely cache this error.
+    """
+
+    def __init__(self, env, custom_tests = {}, conf_dir='$CONFIGUREDIR',
+                 log_file='$CONFIGURELOG', config_h = None, _depth = 0): 
+        """Constructor. Pass additional tests in the custom_tests-dictinary,
+        e.g. custom_tests={'CheckPrivate':MyPrivateTest}, where MyPrivateTest
+        defines a custom test.
+        Note also the conf_dir and log_file arguments (you may want to
+        build tests in the VariantDir, not in the SourceDir)
+        """
+        global SConfFS
+        if not SConfFS:
+            SConfFS = SCons.Node.FS.default_fs or \
+                      SCons.Node.FS.FS(env.fs.pathTop)
+        if sconf_global is not None:
+            raise SCons.Errors.UserError
+        self.env = env
+        if log_file is not None:
+            log_file = SConfFS.File(env.subst(log_file))
+        self.logfile = log_file
+        self.logstream = None
+        self.lastTarget = None
+        self.depth = _depth
+        self.cached = 0 # will be set, if all test results are cached
+
+        # add default tests
+        default_tests = {
+                 'CheckCC'            : CheckCC,
+                 'CheckCXX'           : CheckCXX,
+                 'CheckSHCC'          : CheckSHCC,
+                 'CheckSHCXX'         : CheckSHCXX,
+                 'CheckFunc'          : CheckFunc,
+                 'CheckType'          : CheckType,
+                 'CheckTypeSize'      : CheckTypeSize,
+                 'CheckDeclaration'   : CheckDeclaration,
+                 'CheckHeader'        : CheckHeader,
+                 'CheckCHeader'       : CheckCHeader,
+                 'CheckCXXHeader'     : CheckCXXHeader,
+                 'CheckLib'           : CheckLib,
+                 'CheckLibWithHeader' : CheckLibWithHeader,
+               }
+        self.AddTests(default_tests)
+        self.AddTests(custom_tests)
+        self.confdir = SConfFS.Dir(env.subst(conf_dir))
+        if config_h is not None:
+            config_h = SConfFS.File(config_h)
+        self.config_h = config_h
+        self._startup()
+
+    def Finish(self):
+        """Call this method after finished with your tests:
+                env = sconf.Finish()
+        """
+        self._shutdown()
+        return self.env
+
+    def Define(self, name, value = None, comment = None):
+        """
+        Define a pre processor symbol name, with the optional given value in the
+        current config header.
+
+        If value is None (default), then #define name is written. If value is not
+        none, then #define name value is written.
+        
+        comment is a string which will be put as a C comment in the
+        header, to explain the meaning of the value (appropriate C comments /* and
+        */ will be put automatically."""
+        lines = []
+        if comment:
+            comment_str = "/* %s */" % comment
+            lines.append(comment_str)
+
+        if value is not None:
+            define_str = "#define %s %s" % (name, value)
+        else:
+            define_str = "#define %s" % name
+        lines.append(define_str)
+        lines.append('')
+
+        self.config_h_text = self.config_h_text + '\n'.join(lines)
+
+    def BuildNodes(self, nodes):
+        """
+        Tries to build the given nodes immediately. Returns 1 on success,
+        0 on error.
+        """
+        if self.logstream is not None:
+            # override stdout / stderr to write in log file
+            oldStdout = sys.stdout
+            sys.stdout = self.logstream
+            oldStderr = sys.stderr
+            sys.stderr = self.logstream
+
+        # the engine assumes the current path is the SConstruct directory ...
+        old_fs_dir = SConfFS.getcwd()
+        old_os_dir = os.getcwd()
+        SConfFS.chdir(SConfFS.Top, change_os_dir=1)
+
+        # Because we take responsibility here for writing out our
+        # own .sconsign info (see SConfBuildTask.execute(), above),
+        # we override the store_info() method with a null place-holder
+        # so we really control how it gets written.
+        for n in nodes:
+            n.store_info = n.do_not_store_info
+
+        ret = 1
+
+        try:
+            # ToDo: use user options for calc
+            save_max_drift = SConfFS.get_max_drift()
+            SConfFS.set_max_drift(0)
+            tm = SCons.Taskmaster.Taskmaster(nodes, SConfBuildTask)
+            # we don't want to build tests in parallel
+            jobs = SCons.Job.Jobs(1, tm )
+            jobs.run()
+            for n in nodes:
+                state = n.get_state()
+                if (state != SCons.Node.executed and
+                    state != SCons.Node.up_to_date):
+                    # the node could not be built. we return 0 in this case
+                    ret = 0
+        finally:
+            SConfFS.set_max_drift(save_max_drift)
+            os.chdir(old_os_dir)
+            SConfFS.chdir(old_fs_dir, change_os_dir=0)
+            if self.logstream is not None:
+                # restore stdout / stderr
+                sys.stdout = oldStdout
+                sys.stderr = oldStderr
+        return ret
+
+    def pspawn_wrapper(self, sh, escape, cmd, args, env):
+        """Wrapper function for handling piped spawns.
+
+        This looks to the calling interface (in Action.py) like a "normal"
+        spawn, but associates the call with the PSPAWN variable from
+        the construction environment and with the streams to which we
+        want the output logged.  This gets slid into the construction
+        environment as the SPAWN variable so Action.py doesn't have to
+        know or care whether it's spawning a piped command or not.
+        """
+        return self.pspawn(sh, escape, cmd, args, env, self.logstream, self.logstream)
+
+
+    def TryBuild(self, builder, text = None, extension = ""):
+        """Low level TryBuild implementation. Normally you don't need to
+        call that - you can use TryCompile / TryLink / TryRun instead
+        """
+        global _ac_build_counter
+
+        # Make sure we have a PSPAWN value, and save the current
+        # SPAWN value.
+        try:
+            self.pspawn = self.env['PSPAWN']
+        except KeyError:
+            raise SCons.Errors.UserError('Missing PSPAWN construction variable.')
+        try:
+            save_spawn = self.env['SPAWN']
+        except KeyError:
+            raise SCons.Errors.UserError('Missing SPAWN construction variable.')
+
+        nodesToBeBuilt = []
+
+        f = "conftest_" + str(_ac_build_counter)
+        pref = self.env.subst( builder.builder.prefix )
+        suff = self.env.subst( builder.builder.suffix )
+        target = self.confdir.File(pref + f + suff)
+
+        try:
+            # Slide our wrapper into the construction environment as
+            # the SPAWN function.
+            self.env['SPAWN'] = self.pspawn_wrapper
+            sourcetext = self.env.Value(text)
+
+            if text is not None:
+                textFile = self.confdir.File(f + extension)
+                textFileNode = self.env.SConfSourceBuilder(target=textFile,
+                                                           source=sourcetext)
+                nodesToBeBuilt.extend(textFileNode)
+                source = textFileNode
+            else:
+                source = None
+
+            nodes = builder(target = target, source = source)
+            if not SCons.Util.is_List(nodes):
+                nodes = [nodes]
+            nodesToBeBuilt.extend(nodes)
+            result = self.BuildNodes(nodesToBeBuilt)
+
+        finally:
+            self.env['SPAWN'] = save_spawn
+
+        _ac_build_counter = _ac_build_counter + 1
+        if result:
+            self.lastTarget = nodes[0]
+        else:
+            self.lastTarget = None
+
+        return result
+
+    def TryAction(self, action, text = None, extension = ""):
+        """Tries to execute the given action with optional source file
+        contents <text> and optional source file extension <extension>,
+        Returns the status (0 : failed, 1 : ok) and the contents of the
+        output file.
+        """
+        builder = SCons.Builder.Builder(action=action)
+        self.env.Append( BUILDERS = {'SConfActionBuilder' : builder} )
+        ok = self.TryBuild(self.env.SConfActionBuilder, text, extension)
+        del self.env['BUILDERS']['SConfActionBuilder']
+        if ok:
+            outputStr = self.lastTarget.get_contents()
+            return (1, outputStr)
+        return (0, "")
+
+    def TryCompile( self, text, extension):
+        """Compiles the program given in text to an env.Object, using extension
+        as file extension (e.g. '.c'). Returns 1, if compilation was
+        successful, 0 otherwise. The target is saved in self.lastTarget (for
+        further processing).
+        """
+        return self.TryBuild(self.env.Object, text, extension)
+
+    def TryLink( self, text, extension ):
+        """Compiles the program given in text to an executable env.Program,
+        using extension as file extension (e.g. '.c'). Returns 1, if
+        compilation was successful, 0 otherwise. The target is saved in
+        self.lastTarget (for further processing).
+        """
+        return self.TryBuild(self.env.Program, text, extension )
+
+    def TryRun(self, text, extension ):
+        """Compiles and runs the program given in text, using extension
+        as file extension (e.g. '.c'). Returns (1, outputStr) on success,
+        (0, '') otherwise. The target (a file containing the program's stdout)
+        is saved in self.lastTarget (for further processing).
+        """
+        ok = self.TryLink(text, extension)
+        if( ok ):
+            prog = self.lastTarget
+            pname = prog.path
+            output = self.confdir.File(os.path.basename(pname)+'.out')
+            node = self.env.Command(output, prog, [ [ pname, ">", "${TARGET}"] ])
+            ok = self.BuildNodes(node)
+            if ok:
+                outputStr = output.get_contents()
+                return( 1, outputStr)
+        return (0, "")
+
+    class TestWrapper(object):
+        """A wrapper around Tests (to ensure sanity)"""
+        def __init__(self, test, sconf):
+            self.test = test
+            self.sconf = sconf
+        def __call__(self, *args, **kw):
+            if not self.sconf.active:
+                raise SCons.Errors.UserError
+            context = CheckContext(self.sconf)
+            ret = self.test(context, *args, **kw)
+            if self.sconf.config_h is not None:
+                self.sconf.config_h_text = self.sconf.config_h_text + context.config_h
+            context.Result("error: no result")
+            return ret
+
+    def AddTest(self, test_name, test_instance):
+        """Adds test_class to this SConf instance. It can be called with
+        self.test_name(...)"""
+        setattr(self, test_name, SConfBase.TestWrapper(test_instance, self))
+
+    def AddTests(self, tests):
+        """Adds all the tests given in the tests dictionary to this SConf
+        instance
+        """
+        for name in tests.keys():
+            self.AddTest(name, tests[name])
+
+    def _createDir( self, node ):
+        dirName = str(node)
+        if dryrun:
+            if not os.path.isdir( dirName ):
+                raise ConfigureDryRunError(dirName)
+        else:
+            if not os.path.isdir( dirName ):
+                os.makedirs( dirName )
+                node._exists = 1
+
+    def _startup(self):
+        """Private method. Set up logstream, and set the environment
+        variables necessary for a piped build
+        """
+        global _ac_config_logs
+        global sconf_global
+        global SConfFS
+        
+        self.lastEnvFs = self.env.fs
+        self.env.fs = SConfFS
+        self._createDir(self.confdir)
+        self.confdir.up().add_ignore( [self.confdir] )
+
+        if self.logfile is not None and not dryrun:
+            # truncate logfile, if SConf.Configure is called for the first time
+            # in a build
+            if self.logfile in _ac_config_logs:
+                log_mode = "a"
+            else:
+                _ac_config_logs[self.logfile] = None
+                log_mode = "w"
+            fp = open(str(self.logfile), log_mode)
+            self.logstream = SCons.Util.Unbuffered(fp)
+            # logfile may stay in a build directory, so we tell
+            # the build system not to override it with a eventually
+            # existing file with the same name in the source directory
+            self.logfile.dir.add_ignore( [self.logfile] )
+
+            tb = traceback.extract_stack()[-3-self.depth]
+            old_fs_dir = SConfFS.getcwd()
+            SConfFS.chdir(SConfFS.Top, change_os_dir=0)
+            self.logstream.write('file %s,line %d:\n\tConfigure(confdir = %s)\n' %
+                                 (tb[0], tb[1], str(self.confdir)) )
+            SConfFS.chdir(old_fs_dir)
+        else: 
+            self.logstream = None
+        # we use a special builder to create source files from TEXT
+        action = SCons.Action.Action(_createSource,
+                                     _stringSource)
+        sconfSrcBld = SCons.Builder.Builder(action=action)
+        self.env.Append( BUILDERS={'SConfSourceBuilder':sconfSrcBld} )
+        self.config_h_text = _ac_config_hs.get(self.config_h, "")
+        self.active = 1
+        # only one SConf instance should be active at a time ...
+        sconf_global = self
+
+    def _shutdown(self):
+        """Private method. Reset to non-piped spawn"""
+        global sconf_global, _ac_config_hs
+
+        if not self.active:
+            raise SCons.Errors.UserError("Finish may be called only once!")
+        if self.logstream is not None and not dryrun:
+            self.logstream.write("\n")
+            self.logstream.close()
+            self.logstream = None
+        # remove the SConfSourceBuilder from the environment
+        blds = self.env['BUILDERS']
+        del blds['SConfSourceBuilder']
+        self.env.Replace( BUILDERS=blds )
+        self.active = 0
+        sconf_global = None
+        if not self.config_h is None:
+            _ac_config_hs[self.config_h] = self.config_h_text
+        self.env.fs = self.lastEnvFs
+
+class CheckContext(object):
+    """Provides a context for configure tests. Defines how a test writes to the
+    screen and log file.
+
+    A typical test is just a callable with an instance of CheckContext as
+    first argument:
+
+    def CheckCustom(context, ...)
+    context.Message('Checking my weird test ... ')
+    ret = myWeirdTestFunction(...)
+    context.Result(ret)
+
+    Often, myWeirdTestFunction will be one of
+    context.TryCompile/context.TryLink/context.TryRun. The results of
+    those are cached, for they are only rebuild, if the dependencies have
+    changed.
+    """
+
+    def __init__(self, sconf):
+        """Constructor. Pass the corresponding SConf instance."""
+        self.sconf = sconf
+        self.did_show_result = 0
+
+        # for Conftest.py:
+        self.vardict = {}
+        self.havedict = {}
+        self.headerfilename = None
+        self.config_h = "" # config_h text will be stored here
+        # we don't regenerate the config.h file after each test. That means,
+        # that tests won't be able to include the config.h file, and so
+        # they can't do an #ifdef HAVE_XXX_H. This shouldn't be a major
+        # issue, though. If it turns out, that we need to include config.h
+        # in tests, we must ensure, that the dependencies are worked out
+        # correctly. Note that we can't use Conftest.py's support for config.h,
+        # cause we will need to specify a builder for the config.h file ...
+
+    def Message(self, text):
+        """Inform about what we are doing right now, e.g.
+        'Checking for SOMETHING ... '
+        """
+        self.Display(text)
+        self.sconf.cached = 1
+        self.did_show_result = 0
+
+    def Result(self, res):
+        """Inform about the result of the test. res may be an integer or a
+        string. In case of an integer, the written text will be 'yes' or 'no'.
+        The result is only displayed when self.did_show_result is not set.
+        """
+        if isinstance(res, (int, bool)):
+            if res:
+                text = "yes"
+            else:
+                text = "no"
+        elif isinstance(res, str):
+            text = res
+        else:
+            raise TypeError("Expected string, int or bool, got " + str(type(res)))
+
+        if self.did_show_result == 0:
+            # Didn't show result yet, do it now.
+            self.Display(text + "\n")
+            self.did_show_result = 1
+
+    def TryBuild(self, *args, **kw):
+        return self.sconf.TryBuild(*args, **kw)
+
+    def TryAction(self, *args, **kw):
+        return self.sconf.TryAction(*args, **kw)
+
+    def TryCompile(self, *args, **kw):
+        return self.sconf.TryCompile(*args, **kw)
+
+    def TryLink(self, *args, **kw):
+        return self.sconf.TryLink(*args, **kw)
+
+    def TryRun(self, *args, **kw):
+        return self.sconf.TryRun(*args, **kw)
+
+    def __getattr__( self, attr ):
+        if( attr == 'env' ):
+            return self.sconf.env
+        elif( attr == 'lastTarget' ):
+            return self.sconf.lastTarget
+        else:
+            raise AttributeError("CheckContext instance has no attribute '%s'" % attr)
+
+    #### Stuff used by Conftest.py (look there for explanations).
+
+    def BuildProg(self, text, ext):
+        self.sconf.cached = 1
+        # TODO: should use self.vardict for $CC, $CPPFLAGS, etc.
+        return not self.TryBuild(self.env.Program, text, ext)
+
+    def CompileProg(self, text, ext):
+        self.sconf.cached = 1
+        # TODO: should use self.vardict for $CC, $CPPFLAGS, etc.
+        return not self.TryBuild(self.env.Object, text, ext)
+
+    def CompileSharedObject(self, text, ext):
+        self.sconf.cached = 1
+        # TODO: should use self.vardict for $SHCC, $CPPFLAGS, etc.
+        return not self.TryBuild(self.env.SharedObject, text, ext)
+
+    def RunProg(self, text, ext):
+        self.sconf.cached = 1
+        # TODO: should use self.vardict for $CC, $CPPFLAGS, etc.
+        st, out = self.TryRun(text, ext)
+        return not st, out
+
+    def AppendLIBS(self, lib_name_list):
+        oldLIBS = self.env.get( 'LIBS', [] )
+        self.env.Append(LIBS = lib_name_list)
+        return oldLIBS
+
+    def PrependLIBS(self, lib_name_list):
+        oldLIBS = self.env.get( 'LIBS', [] )
+        self.env.Prepend(LIBS = lib_name_list)
+        return oldLIBS
+
+    def SetLIBS(self, val):
+        oldLIBS = self.env.get( 'LIBS', [] )
+        self.env.Replace(LIBS = val)
+        return oldLIBS
+
+    def Display(self, msg):
+        if self.sconf.cached:
+            # We assume that Display is called twice for each test here
+            # once for the Checking for ... message and once for the result.
+            # The self.sconf.cached flag can only be set between those calls
+            msg = "(cached) " + msg
+            self.sconf.cached = 0
+        progress_display(msg, append_newline=0)
+        self.Log("scons: Configure: " + msg + "\n")
+
+    def Log(self, msg):
+        if self.sconf.logstream is not None:
+            self.sconf.logstream.write(msg)
+
+    #### End of stuff used by Conftest.py.
+
+
+def SConf(*args, **kw):
+    if kw.get(build_type, True):
+        kw['_depth'] = kw.get('_depth', 0) + 1
+        for bt in build_types:
+            try:
+                del kw[bt]
+            except KeyError:
+                pass
+        return SConfBase(*args, **kw)
+    else:
+        return SCons.Util.Null()
+
+
+def CheckFunc(context, function_name, header = None, language = None):
+    res = SCons.Conftest.CheckFunc(context, function_name, header = header, language = language)
+    context.did_show_result = 1
+    return not res
+
+def CheckType(context, type_name, includes = "", language = None):
+    res = SCons.Conftest.CheckType(context, type_name,
+                                   header = includes, language = language)
+    context.did_show_result = 1
+    return not res
+
+def CheckTypeSize(context, type_name, includes = "", language = None, expect = None):
+    res = SCons.Conftest.CheckTypeSize(context, type_name,
+                                       header = includes, language = language, 
+                                       expect = expect)
+    context.did_show_result = 1
+    return res
+
+def CheckDeclaration(context, declaration, includes = "", language = None):
+    res = SCons.Conftest.CheckDeclaration(context, declaration,
+                                          includes = includes, 
+                                          language = language)
+    context.did_show_result = 1
+    return not res
+
+def createIncludesFromHeaders(headers, leaveLast, include_quotes = '""'):
+    # used by CheckHeader and CheckLibWithHeader to produce C - #include
+    # statements from the specified header (list)
+    if not SCons.Util.is_List(headers):
+        headers = [headers]
+    l = []
+    if leaveLast:
+        lastHeader = headers[-1]
+        headers = headers[:-1]
+    else:
+        lastHeader = None
+    for s in headers:
+        l.append("#include %s%s%s\n"
+                 % (include_quotes[0], s, include_quotes[1]))
+    return ''.join(l), lastHeader
+
+def CheckHeader(context, header, include_quotes = '<>', language = None):
+    """
+    A test for a C or C++ header file.
+    """
+    prog_prefix, hdr_to_check = \
+                 createIncludesFromHeaders(header, 1, include_quotes)
+    res = SCons.Conftest.CheckHeader(context, hdr_to_check, prog_prefix,
+                                     language = language,
+                                     include_quotes = include_quotes)
+    context.did_show_result = 1
+    return not res
+
+def CheckCC(context):
+    res = SCons.Conftest.CheckCC(context)
+    context.did_show_result = 1
+    return not res
+
+def CheckCXX(context):
+    res = SCons.Conftest.CheckCXX(context)
+    context.did_show_result = 1
+    return not res
+
+def CheckSHCC(context):
+    res = SCons.Conftest.CheckSHCC(context)
+    context.did_show_result = 1
+    return not res
+
+def CheckSHCXX(context):
+    res = SCons.Conftest.CheckSHCXX(context)
+    context.did_show_result = 1
+    return not res
+
+# Bram: Make this function obsolete?  CheckHeader() is more generic.
+
+def CheckCHeader(context, header, include_quotes = '""'):
+    """
+    A test for a C header file.
+    """
+    return CheckHeader(context, header, include_quotes, language = "C")
+
+
+# Bram: Make this function obsolete?  CheckHeader() is more generic.
+
+def CheckCXXHeader(context, header, include_quotes = '""'):
+    """
+    A test for a C++ header file.
+    """
+    return CheckHeader(context, header, include_quotes, language = "C++")
+
+
+def CheckLib(context, library = None, symbol = "main",
+             header = None, language = None, autoadd = 1):
+    """
+    A test for a library. See also CheckLibWithHeader.
+    Note that library may also be None to test whether the given symbol
+    compiles without flags.
+    """
+
+    if library == []:
+        library = [None]
+
+    if not SCons.Util.is_List(library):
+        library = [library]
+    
+    # ToDo: accept path for the library
+    res = SCons.Conftest.CheckLib(context, library, symbol, header = header,
+                                        language = language, autoadd = autoadd)
+    context.did_show_result = 1
+    return not res
+
+# XXX
+# Bram: Can only include one header and can't use #ifdef HAVE_HEADER_H.
+
+def CheckLibWithHeader(context, libs, header, language,
+                       call = None, autoadd = 1):
+    # ToDo: accept path for library. Support system header files.
+    """
+    Another (more sophisticated) test for a library.
+    Checks, if library and header is available for language (may be 'C'
+    or 'CXX'). Call maybe be a valid expression _with_ a trailing ';'.
+    As in CheckLib, we support library=None, to test if the call compiles
+    without extra link flags.
+    """
+    prog_prefix, dummy = \
+                 createIncludesFromHeaders(header, 0)
+    if libs == []:
+        libs = [None]
+
+    if not SCons.Util.is_List(libs):
+        libs = [libs]
+
+    res = SCons.Conftest.CheckLib(context, libs, None, prog_prefix,
+            call = call, language = language, autoadd = autoadd)
+    context.did_show_result = 1
+    return not res
+
+# Local Variables:
+# tab-width:4
+# indent-tabs-mode:nil
+# End:
+# vim: set expandtab tabstop=4 shiftwidth=4: