Source

berlios / sconsexe / engine / SCons / SConf.py

Full commit
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
"""SCons.SConf

Autoconf-like configuration support.
"""

#
# Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007 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 2523 2007/12/12 09:37:41 knight"

import SCons.compat

import os
import re
import string
import StringIO
import sys
import traceback
import types

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_]', '_', string.upper(str(target[0])))
    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  |' +
            string.replace( source[0].get_contents(),
                            '\n', "\n  |" ) )

# python 2.2 introduces types.BooleanType
BooleanTypes = [types.IntType]
if hasattr(types, 'BooleanType'): BooleanTypes.append(types.BooleanType)

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:
    """
    'Sniffer' for a file-like writable object. Similar to the unix tool tee.
    """
    def __init__(self, orig):
        self.orig = orig
        self.s = StringIO.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.Task):
    """
    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" +
                         string.replace("  |" + str(bi.string),
                                        "\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)
            pass
        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
            apply(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()
                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:
    """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 BuildDir, not in the SourceDir)
        """
        global SConfFS
        if not SConfFS:
            SConfFS = SCons.Node.FS.default_fs or \
                      SCons.Node.FS.FS(env.fs.pathTop)
        if not sconf_global is None:
            raise (SCons.Errors.UserError,
                   "Only one SConf object may be active at one time")
        self.env = env
        if log_file != 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 = {
                 'CheckFunc'          : CheckFunc,
                 'CheckType'          : CheckType,
                 'CheckTypeSize'      : CheckTypeSize,
                 '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 not config_h is 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 BuildNodes(self, nodes):
        """
        Tries to build the given nodes immediately. Returns 1 on success,
        0 on error.
        """
        if self.logstream != 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 != 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 != 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 = str(prog)
            output = SConfFS.File(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:
        """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,
                       "Test called after sconf.Finish()")
            context = CheckContext(self.sconf)
            ret = apply(self.test, (context,) +  args, kw)
            if not self.sconf.config_h is 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 != None and not dryrun:
            # truncate logfile, if SConf.Configure is called for the first time
            # in a build
            if _ac_config_logs.has_key(self.logfile):
                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 != 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:
    """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 'ok' or
        'failed'.
        The result is only displayed when self.did_show_result is not set.
        """
        if type(res) in BooleanTypes:
            if res:
                text = "yes"
            else:
                text = "no"
        elif type(res) == types.StringType:
            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 apply(self.sconf.TryBuild, args, kw)

    def TryAction(self, *args, **kw):
        return apply(self.sconf.TryAction, args, kw)

    def TryCompile(self, *args, **kw):
        return apply(self.sconf.TryCompile, args, kw)

    def TryLink(self, *args, **kw):
        return apply(self.sconf.TryLink, args, kw)

    def TryRun(self, *args, **kw):
        return apply(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 AppendLIBS(self, lib_name_list):
        oldLIBS = self.env.get( 'LIBS', [] )
        self.env.Append(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 != 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 apply(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 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 string.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

# 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