summaryrefslogtreecommitdiffstats
path: root/Source/cmComputeTargetDepends.cxx
blob: bbffd5da07525201fbf1ba0d0eb21e66b0361020 (plain)
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
/*============================================================================
  CMake - Cross Platform Makefile Generator
  Copyright 2000-2009 Kitware, Inc., Insight Software Consortium

  Distributed under the OSI-approved BSD License (the "License");
  see accompanying file Copyright.txt for details.

  This software is distributed WITHOUT ANY WARRANTY; without even the
  implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  See the License for more information.
============================================================================*/
#include "cmComputeTargetDepends.h"

#include "cmComputeComponentGraph.h"
#include "cmGlobalGenerator.h"
#include "cmLocalGenerator.h"
#include "cmMakefile.h"
#include "cmSystemTools.h"
#include "cmSourceFile.h"
#include "cmTarget.h"
#include "cmake.h"

#include <algorithm>

#include <assert.h>

/*

This class is meant to analyze inter-target dependencies globally
during the generation step.  The goal is to produce a set of direct
dependencies for each target such that no cycles are left and the
build order is safe.

For most target types cyclic dependencies are not allowed.  However
STATIC libraries may depend on each other in a cyclic fashion.  In
general the directed dependency graph forms a directed-acyclic-graph
of strongly connected components.  All strongly connected components
should consist of only STATIC_LIBRARY targets.

In order to safely break dependency cycles we must preserve all other
dependencies passing through the corresponding strongly connected component.
The approach taken by this class is as follows:

  - Collect all targets and form the original dependency graph
  - Run Tarjan's algorithm to extract the strongly connected components
    (error if any member of a non-trivial component is not STATIC)
  - The original dependencies imply a DAG on the components.
    Use the implied DAG to construct a final safe set of dependencies.

The final dependency set is constructed as follows:

  - For each connected component targets are placed in an arbitrary
    order.  Each target depends on the target following it in the order.
    The first target is designated the head and the last target the tail.
    (most components will be just 1 target anyway)

  - Original dependencies between targets in different components are
    converted to connect the depender's component tail to the
    dependee's component head.

In most cases this will reproduce the original dependencies.  However
when there are cycles of static libraries they will be broken in a
safe manner.

For example, consider targets A0, A1, A2, B0, B1, B2, and C with these
dependencies:

  A0 -> A1 -> A2 -> A0  ,  B0 -> B1 -> B2 -> B0 -> A0  ,  C -> B0

Components may be identified as

  Component 0: A0, A1, A2
  Component 1: B0, B1, B2
  Component 2: C

Intra-component dependencies are:

  0: A0 -> A1 -> A2   , head=A0, tail=A2
  1: B0 -> B1 -> B2   , head=B0, tail=B2
  2: head=C, tail=C

The inter-component dependencies are converted as:

  B0 -> A0  is component 1->0 and becomes  B2 -> A0
  C  -> B0  is component 2->1 and becomes  C  -> B0

This leads to the final target dependencies:

  C -> B0 -> B1 -> B2 -> A0 -> A1 -> A2

These produce a safe build order since C depends directly or
transitively on all the static libraries it links.

*/

//----------------------------------------------------------------------------
cmComputeTargetDepends::cmComputeTargetDepends(cmGlobalGenerator* gg)
{
  this->GlobalGenerator = gg;
  cmake* cm = this->GlobalGenerator->GetCMakeInstance();
  this->DebugMode = cm->GetPropertyAsBool("GLOBAL_DEPENDS_DEBUG_MODE");
  this->NoCycles = cm->GetPropertyAsBool("GLOBAL_DEPENDS_NO_CYCLES");
}

//----------------------------------------------------------------------------
cmComputeTargetDepends::~cmComputeTargetDepends()
{
}

//----------------------------------------------------------------------------
bool cmComputeTargetDepends::Compute()
{
  // Build the original graph.
  this->CollectTargets();
  this->CollectDepends();
  if(this->DebugMode)
    {
    this->DisplayGraph(this->InitialGraph, "initial");
    }

  // Identify components.
  cmComputeComponentGraph ccg(this->InitialGraph);
  if(this->DebugMode)
    {
    this->DisplayComponents(ccg);
    }
  if(!this->CheckComponents(ccg))
    {
    return false;
    }

  // Compute the final dependency graph.
  if(!this->ComputeFinalDepends(ccg))
    {
    return false;
    }
  if(this->DebugMode)
    {
    this->DisplayGraph(this->FinalGraph, "final");
    }

  return true;
}

//----------------------------------------------------------------------------
void
cmComputeTargetDepends::GetTargetDirectDepends(cmTarget const* t,
                                               cmTargetDependSet& deps)
{
  // Lookup the index for this target.  All targets should be known by
  // this point.
  std::map<cmTarget const*, int>::const_iterator tii
                                                  = this->TargetIndex.find(t);
  assert(tii != this->TargetIndex.end());
  int i = tii->second;

  // Get its final dependencies.
  EdgeList const& nl = this->FinalGraph[i];
  for(EdgeList::const_iterator ni = nl.begin(); ni != nl.end(); ++ni)
    {
    cmTarget const* dep = this->Targets[*ni];
    cmTargetDependSet::iterator di = deps.insert(dep).first;
    di->SetType(ni->IsStrong());
    }
}

//----------------------------------------------------------------------------
void cmComputeTargetDepends::CollectTargets()
{
  // Collect all targets from all generators.
  std::vector<cmLocalGenerator*> const& lgens =
    this->GlobalGenerator->GetLocalGenerators();
  for(unsigned int i = 0; i < lgens.size(); ++i)
    {
    const cmTargets& targets = lgens[i]->GetMakefile()->GetTargets();
    for(cmTargets::const_iterator ti = targets.begin();
        ti != targets.end(); ++ti)
      {
      cmTarget const* target = &ti->second;
      int index = static_cast<int>(this->Targets.size());
      this->TargetIndex[target] = index;
      this->Targets.push_back(target);
      }
    }
}

//----------------------------------------------------------------------------
void cmComputeTargetDepends::CollectDepends()
{
  // Allocate the dependency graph adjacency lists.
  this->InitialGraph.resize(this->Targets.size());

  // Compute each dependency list.
  for(unsigned int i=0; i < this->Targets.size(); ++i)
    {
    this->CollectTargetDepends(i);
    }
}

//----------------------------------------------------------------------------
void cmComputeTargetDepends::CollectTargetDepends(int depender_index)
{
  // Get the depender.
  cmTarget const* depender = this->Targets[depender_index];
  if (depender->GetType() == cmTarget::INTERFACE_LIBRARY)
    {
    return;
    }

  // Loop over all targets linked directly in all configs.
  // We need to make targets depend on the union of all config-specific
  // dependencies in all targets, because the generated build-systems can't
  // deal with config-specific dependencies.
  {
  std::set<std::string> emitted;
  cmGeneratorTarget* gt = depender->GetMakefile()->GetLocalGenerator()
                                  ->GetGlobalGenerator()
                                  ->GetGeneratorTarget(depender);

  std::vector<std::string> configs;
  depender->GetMakefile()->GetConfigurations(configs);
  if (configs.empty())
    {
    configs.push_back("");
    }
  for (std::vector<std::string>::const_iterator it = configs.begin();
    it != configs.end(); ++it)
    {
    std::vector<cmSourceFile const*> objectFiles;
    gt->GetExternalObjects(objectFiles, *it);
    for(std::vector<cmSourceFile const*>::const_iterator
        oi = objectFiles.begin(); oi != objectFiles.end(); ++oi)
      {
      std::string objLib = (*oi)->GetObjectLibrary();
      if (!objLib.empty() && emitted.insert(objLib).second)
        {
        if(depender->GetType() != cmTarget::EXECUTABLE &&
            depender->GetType() != cmTarget::STATIC_LIBRARY &&
            depender->GetType() != cmTarget::SHARED_LIBRARY &&
            depender->GetType() != cmTarget::MODULE_LIBRARY)
          {
          this->GlobalGenerator->GetCMakeInstance()
            ->IssueMessage(cmake::FATAL_ERROR,
                            "Only executables and non-OBJECT libraries may "
                            "reference target objects.",
                            depender->GetBacktrace());
          return;
          }
        const_cast<cmTarget*>(depender)->AddUtility(objLib);
        }
      }

    cmTarget::LinkImplementation const* impl =
      depender->GetLinkImplementation(*it);

    // A target should not depend on itself.
    emitted.insert(depender->GetName());
    for(std::vector<cmLinkImplItem>::const_iterator
          lib = impl->Libraries.begin();
        lib != impl->Libraries.end(); ++lib)
      {
      // Don't emit the same library twice for this target.
      if(emitted.insert(*lib).second)
        {
        this->AddTargetDepend(depender_index, *lib, true);
        this->AddInterfaceDepends(depender_index, *lib, emitted);
        }
      }
    }
  }

  // Loop over all utility dependencies.
  {
  std::set<cmLinkItem> const& tutils = depender->GetUtilityItems();
  std::set<std::string> emitted;
  // A target should not depend on itself.
  emitted.insert(depender->GetName());
  for(std::set<cmLinkItem>::const_iterator util = tutils.begin();
      util != tutils.end(); ++util)
    {
    // Don't emit the same utility twice for this target.
    if(emitted.insert(*util).second)
      {
      this->AddTargetDepend(depender_index, *util, false);
      }
    }
  }
}

//----------------------------------------------------------------------------
void cmComputeTargetDepends::AddInterfaceDepends(int depender_index,
                                                 cmTarget const* dependee,
                                                 const std::string& config,
                                               std::set<std::string> &emitted)
{
  cmTarget const* depender = this->Targets[depender_index];
  if(cmTarget::LinkInterface const* iface =
                                dependee->GetLinkInterface(config, depender))
    {
    for(std::vector<cmLinkItem>::const_iterator
        lib = iface->Libraries.begin();
        lib != iface->Libraries.end(); ++lib)
      {
      // Don't emit the same library twice for this target.
      if(emitted.insert(*lib).second)
        {
        this->AddTargetDepend(depender_index, *lib, true);
        this->AddInterfaceDepends(depender_index, *lib, emitted);
        }
      }
    }
}

//----------------------------------------------------------------------------
void cmComputeTargetDepends::AddInterfaceDepends(int depender_index,
                                             cmLinkItem const& dependee_name,
                                             std::set<std::string> &emitted)
{
  cmTarget const* depender = this->Targets[depender_index];
  cmTarget const* dependee = dependee_name.Target;
  // Skip targets that will not really be linked.  This is probably a
  // name conflict between an external library and an executable
  // within the project.
  if(dependee &&
     dependee->GetType() == cmTarget::EXECUTABLE &&
     !dependee->IsExecutableWithExports())
    {
    dependee = 0;
    }

  if(dependee)
    {
    this->AddInterfaceDepends(depender_index, dependee, "", emitted);
    std::vector<std::string> configs;
    depender->GetMakefile()->GetConfigurations(configs);
    for (std::vector<std::string>::const_iterator it = configs.begin();
      it != configs.end(); ++it)
      {
      // A target should not depend on itself.
      emitted.insert(depender->GetName());
      this->AddInterfaceDepends(depender_index, dependee,
                                *it, emitted);
      }
    }
}

//----------------------------------------------------------------------------
void cmComputeTargetDepends::AddTargetDepend(
  int depender_index, cmLinkItem const& dependee_name,
  bool linking)
{
  // Get the depender.
  cmTarget const* depender = this->Targets[depender_index];

  // Check the target's makefile first.
  cmTarget const* dependee = dependee_name.Target;

  if(!dependee && !linking &&
    (depender->GetType() != cmTarget::GLOBAL_TARGET))
    {
    cmMakefile *makefile = depender->GetMakefile();
    cmake::MessageType messageType = cmake::AUTHOR_WARNING;
    bool issueMessage = false;
    std::ostringstream e;
    switch(depender->GetPolicyStatusCMP0046())
      {
      case cmPolicies::WARN:
        e << (makefile->GetPolicies()
          ->GetPolicyWarning(cmPolicies::CMP0046)) << "\n";
        issueMessage = true;
      case cmPolicies::OLD:
        break;
      case cmPolicies::NEW:
      case cmPolicies::REQUIRED_IF_USED:
      case cmPolicies::REQUIRED_ALWAYS:
        issueMessage = true;
        messageType = cmake::FATAL_ERROR;
      }
    if(issueMessage)
      {
      cmake* cm = this->GlobalGenerator->GetCMakeInstance();

      e << "The dependency target \"" <<  dependee_name
        << "\" of target \"" << depender->GetName() << "\" does not exist.";

      cmListFileBacktrace const* backtrace =
        depender->GetUtilityBacktrace(dependee_name);
      if(backtrace)
        {
        cm->IssueMessage(messageType, e.str(), *backtrace);
        }
      else
        {
        cm->IssueMessage(messageType, e.str());
        }

      }
    }

  // Skip targets that will not really be linked.  This is probably a
  // name conflict between an external library and an executable
  // within the project.
  if(linking && dependee &&
     dependee->GetType() == cmTarget::EXECUTABLE &&
     !dependee->IsExecutableWithExports())
    {
    dependee = 0;
    }

  if(dependee)
    {
    this->AddTargetDepend(depender_index, dependee, linking);
    }
}

//----------------------------------------------------------------------------
void cmComputeTargetDepends::AddTargetDepend(int depender_index,
                                             cmTarget const* dependee,
                                             bool linking)
{
  if(dependee->IsImported() ||
     dependee->GetType() == cmTarget::INTERFACE_LIBRARY)
    {
    // Skip IMPORTED and INTERFACE targets but follow their utility
    // dependencies.
    std::set<cmLinkItem> const& utils = dependee->GetUtilityItems();
    for(std::set<cmLinkItem>::const_iterator i = utils.begin();
        i != utils.end(); ++i)
      {
      if(cmTarget const* transitive_dependee = i->Target)
        {
        this->AddTargetDepend(depender_index, transitive_dependee, false);
        }
      }
    }
  else
    {
    // Lookup the index for this target.  All targets should be known by
    // this point.
    std::map<cmTarget const*, int>::const_iterator tii =
      this->TargetIndex.find(dependee);
    assert(tii != this->TargetIndex.end());
    int dependee_index = tii->second;

    // Add this entry to the dependency graph.
    this->InitialGraph[depender_index].push_back(
      cmGraphEdge(dependee_index, !linking));
    }
}

//----------------------------------------------------------------------------
void
cmComputeTargetDepends::DisplayGraph(Graph const& graph,
                                     const std::string& name)
{
  fprintf(stderr, "The %s target dependency graph is:\n", name.c_str());
  int n = static_cast<int>(graph.size());
  for(int depender_index = 0; depender_index < n; ++depender_index)
    {
    EdgeList const& nl = graph[depender_index];
    cmTarget const* depender = this->Targets[depender_index];
    fprintf(stderr, "target %d is [%s]\n",
            depender_index, depender->GetName().c_str());
    for(EdgeList::const_iterator ni = nl.begin(); ni != nl.end(); ++ni)
      {
      int dependee_index = *ni;
      cmTarget const* dependee = this->Targets[dependee_index];
      fprintf(stderr, "  depends on target %d [%s] (%s)\n", dependee_index,
              dependee->GetName().c_str(), ni->IsStrong()? "strong" : "weak");
      }
    }
  fprintf(stderr, "\n");
}

//----------------------------------------------------------------------------
void
cmComputeTargetDepends
::DisplayComponents(cmComputeComponentGraph const& ccg)
{
  fprintf(stderr, "The strongly connected components are:\n");
  std::vector<NodeList> const& components = ccg.GetComponents();
  int n = static_cast<int>(components.size());
  for(int c = 0; c < n; ++c)
    {
    NodeList const& nl = components[c];
    fprintf(stderr, "Component (%d):\n", c);
    for(NodeList::const_iterator ni = nl.begin(); ni != nl.end(); ++ni)
      {
      int i = *ni;
      fprintf(stderr, "  contains target %d [%s]\n",
              i, this->Targets[i]->GetName().c_str());
      }
    }
  fprintf(stderr, "\n");
}

//----------------------------------------------------------------------------
bool
cmComputeTargetDepends
::CheckComponents(cmComputeComponentGraph const& ccg)
{
  // All non-trivial components should consist only of static
  // libraries.
  std::vector<NodeList> const& components = ccg.GetComponents();
  int nc = static_cast<int>(components.size());
  for(int c=0; c < nc; ++c)
    {
    // Get the current component.
    NodeList const& nl = components[c];

    // Skip trivial components.
    if(nl.size() < 2)
      {
      continue;
      }

    // Immediately complain if no cycles are allowed at all.
    if(this->NoCycles)
      {
      this->ComplainAboutBadComponent(ccg, c);
      return false;
      }

    // Make sure the component is all STATIC_LIBRARY targets.
    for(NodeList::const_iterator ni = nl.begin(); ni != nl.end(); ++ni)
      {
      if(this->Targets[*ni]->GetType() != cmTarget::STATIC_LIBRARY)
        {
        this->ComplainAboutBadComponent(ccg, c);
        return false;
        }
      }
    }
  return true;
}

//----------------------------------------------------------------------------
void
cmComputeTargetDepends
::ComplainAboutBadComponent(cmComputeComponentGraph const& ccg, int c,
                            bool strong)
{
  // Construct the error message.
  std::ostringstream e;
  e << "The inter-target dependency graph contains the following "
    << "strongly connected component (cycle):\n";
  std::vector<NodeList> const& components = ccg.GetComponents();
  std::vector<int> const& cmap = ccg.GetComponentMap();
  NodeList const& cl = components[c];
  for(NodeList::const_iterator ci = cl.begin(); ci != cl.end(); ++ci)
    {
    // Get the depender.
    int i = *ci;
    cmTarget const* depender = this->Targets[i];

    // Describe the depender.
    e << "  \"" << depender->GetName() << "\" of type "
      << cmTarget::GetTargetTypeName(depender->GetType()) << "\n";

    // List its dependencies that are inside the component.
    EdgeList const& nl = this->InitialGraph[i];
    for(EdgeList::const_iterator ni = nl.begin(); ni != nl.end(); ++ni)
      {
      int j = *ni;
      if(cmap[j] == c)
        {
        cmTarget const* dependee = this->Targets[j];
        e << "    depends on \"" << dependee->GetName() << "\""
          << " (" << (ni->IsStrong()? "strong" : "weak") << ")\n";
        }
      }
    }
  if(strong)
    {
    // Custom command executable dependencies cannot occur within a
    // component of static libraries.  The cycle must appear in calls
    // to add_dependencies.
    e << "The component contains at least one cycle consisting of strong "
      << "dependencies (created by add_dependencies) that cannot be broken.";
    }
  else if(this->NoCycles)
    {
    e << "The GLOBAL_DEPENDS_NO_CYCLES global property is enabled, so "
      << "cyclic dependencies are not allowed even among static libraries.";
    }
  else
    {
    e << "At least one of these targets is not a STATIC_LIBRARY.  "
      << "Cyclic dependencies are allowed only among static libraries.";
    }
  cmSystemTools::Error(e.str().c_str());
}

//----------------------------------------------------------------------------
bool
cmComputeTargetDepends
::IntraComponent(std::vector<int> const& cmap, int c, int i, int* head,
                 std::set<int>& emitted, std::set<int>& visited)
{
  if(!visited.insert(i).second)
    {
    // Cycle in utility depends!
    return false;
    }
  if(emitted.insert(i).second)
    {
    // Honor strong intra-component edges in the final order.
    EdgeList const& el = this->InitialGraph[i];
    for(EdgeList::const_iterator ei = el.begin(); ei != el.end(); ++ei)
      {
      int j = *ei;
      if(cmap[j] == c && ei->IsStrong())
        {
        this->FinalGraph[i].push_back(cmGraphEdge(j, true));
        if(!this->IntraComponent(cmap, c, j, head, emitted, visited))
          {
          return false;
          }
        }
      }

    // Prepend to a linear linked-list of intra-component edges.
    if(*head >= 0)
      {
      this->FinalGraph[i].push_back(cmGraphEdge(*head, false));
      }
    else
      {
      this->ComponentTail[c] = i;
      }
    *head = i;
    }
  return true;
}

//----------------------------------------------------------------------------
bool
cmComputeTargetDepends
::ComputeFinalDepends(cmComputeComponentGraph const& ccg)
{
  // Get the component graph information.
  std::vector<NodeList> const& components = ccg.GetComponents();
  Graph const& cgraph = ccg.GetComponentGraph();

  // Allocate the final graph.
  this->FinalGraph.resize(0);
  this->FinalGraph.resize(this->InitialGraph.size());

  // Choose intra-component edges to linearize dependencies.
  std::vector<int> const& cmap = ccg.GetComponentMap();
  this->ComponentHead.resize(components.size());
  this->ComponentTail.resize(components.size());
  int nc = static_cast<int>(components.size());
  for(int c=0; c < nc; ++c)
    {
    int head = -1;
    std::set<int> emitted;
    NodeList const& nl = components[c];
    for(NodeList::const_reverse_iterator ni = nl.rbegin();
        ni != nl.rend(); ++ni)
      {
      std::set<int> visited;
      if(!this->IntraComponent(cmap, c, *ni, &head, emitted, visited))
        {
        // Cycle in add_dependencies within component!
        this->ComplainAboutBadComponent(ccg, c, true);
        return false;
        }
      }
    this->ComponentHead[c] = head;
    }

  // Convert inter-component edges to connect component tails to heads.
  int n = static_cast<int>(cgraph.size());
  for(int depender_component=0; depender_component < n; ++depender_component)
    {
    int depender_component_tail = this->ComponentTail[depender_component];
    EdgeList const& nl = cgraph[depender_component];
    for(EdgeList::const_iterator ni = nl.begin(); ni != nl.end(); ++ni)
      {
      int dependee_component = *ni;
      int dependee_component_head = this->ComponentHead[dependee_component];
      this->FinalGraph[depender_component_tail]
        .push_back(cmGraphEdge(dependee_component_head, ni->IsStrong()));
      }
    }
  return true;
}