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Strong dependencies (created by add_dependencies) must be honored when linearizing a strongly-connected component of the target dependency graph. The initial graph edges have strong/weak labels and can contain cycles that do not consist exclusively of strong edges. The final graph never contains cycles so all edges can be strong.
523 lines
16 KiB
C++
523 lines
16 KiB
C++
/*============================================================================
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CMake - Cross Platform Makefile Generator
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Copyright 2000-2009 Kitware, Inc., Insight Software Consortium
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Distributed under the OSI-approved BSD License (the "License");
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see accompanying file Copyright.txt for details.
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This software is distributed WITHOUT ANY WARRANTY; without even the
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implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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See the License for more information.
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============================================================================*/
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#include "cmComputeTargetDepends.h"
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#include "cmComputeComponentGraph.h"
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#include "cmGlobalGenerator.h"
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#include "cmLocalGenerator.h"
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#include "cmMakefile.h"
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#include "cmSystemTools.h"
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#include "cmTarget.h"
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#include "cmake.h"
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#include <algorithm>
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#include <assert.h>
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/*
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This class is meant to analyze inter-target dependencies globally
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during the generation step. The goal is to produce a set of direct
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dependencies for each target such that no cycles are left and the
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build order is safe.
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For most target types cyclic dependencies are not allowed. However
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STATIC libraries may depend on each other in a cyclic fasion. In
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general the directed dependency graph forms a directed-acyclic-graph
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of strongly connected components. All strongly connected components
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should consist of only STATIC_LIBRARY targets.
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In order to safely break dependency cycles we must preserve all other
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dependencies passing through the corresponding strongly connected component.
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The approach taken by this class is as follows:
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- Collect all targets and form the original dependency graph
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- Run Tarjan's algorithm to extract the strongly connected components
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(error if any member of a non-trivial component is not STATIC)
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- The original dependencies imply a DAG on the components.
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Use the implied DAG to construct a final safe set of dependencies.
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The final dependency set is constructed as follows:
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- For each connected component targets are placed in an arbitrary
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order. Each target depends on the target following it in the order.
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The first target is designated the head and the last target the tail.
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(most components will be just 1 target anyway)
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- Original dependencies between targets in different components are
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converted to connect the depender's component tail to the
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dependee's component head.
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In most cases this will reproduce the original dependencies. However
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when there are cycles of static libraries they will be broken in a
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safe manner.
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For example, consider targets A0, A1, A2, B0, B1, B2, and C with these
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dependencies:
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A0 -> A1 -> A2 -> A0 , B0 -> B1 -> B2 -> B0 -> A0 , C -> B0
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Components may be identified as
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Component 0: A0, A1, A2
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Component 1: B0, B1, B2
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Component 2: C
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Intra-component dependencies are:
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0: A0 -> A1 -> A2 , head=A0, tail=A2
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1: B0 -> B1 -> B2 , head=B0, tail=B2
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2: head=C, tail=C
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The inter-component dependencies are converted as:
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B0 -> A0 is component 1->0 and becomes B2 -> A0
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C -> B0 is component 2->1 and becomes C -> B0
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This leads to the final target dependencies:
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C -> B0 -> B1 -> B2 -> A0 -> A1 -> A2
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These produce a safe build order since C depends directly or
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transitively on all the static libraries it links.
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*/
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//----------------------------------------------------------------------------
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cmComputeTargetDepends::cmComputeTargetDepends(cmGlobalGenerator* gg)
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{
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this->GlobalGenerator = gg;
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cmake* cm = this->GlobalGenerator->GetCMakeInstance();
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this->DebugMode = cm->GetPropertyAsBool("GLOBAL_DEPENDS_DEBUG_MODE");
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this->NoCycles = cm->GetPropertyAsBool("GLOBAL_DEPENDS_NO_CYCLES");
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}
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//----------------------------------------------------------------------------
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cmComputeTargetDepends::~cmComputeTargetDepends()
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{
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}
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//----------------------------------------------------------------------------
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bool cmComputeTargetDepends::Compute()
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{
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// Build the original graph.
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this->CollectTargets();
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this->CollectDepends();
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if(this->DebugMode)
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{
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this->DisplayGraph(this->InitialGraph, "initial");
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}
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// Identify components.
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cmComputeComponentGraph ccg(this->InitialGraph);
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if(this->DebugMode)
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{
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this->DisplayComponents(ccg);
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}
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if(!this->CheckComponents(ccg))
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{
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return false;
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}
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// Compute the final dependency graph.
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if(!this->ComputeFinalDepends(ccg))
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{
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return false;
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}
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if(this->DebugMode)
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{
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this->DisplayGraph(this->FinalGraph, "final");
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}
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return true;
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}
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//----------------------------------------------------------------------------
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void
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cmComputeTargetDepends::GetTargetDirectDepends(cmTarget* t,
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std::set<cmTarget*>& deps)
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{
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// Lookup the index for this target. All targets should be known by
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// this point.
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std::map<cmTarget*, int>::const_iterator tii = this->TargetIndex.find(t);
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assert(tii != this->TargetIndex.end());
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int i = tii->second;
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// Get its final dependencies.
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EdgeList const& nl = this->FinalGraph[i];
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for(EdgeList::const_iterator ni = nl.begin(); ni != nl.end(); ++ni)
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{
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deps.insert(this->Targets[*ni]);
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}
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}
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//----------------------------------------------------------------------------
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void cmComputeTargetDepends::CollectTargets()
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{
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// Collect all targets from all generators.
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std::vector<cmLocalGenerator*> const& lgens =
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this->GlobalGenerator->GetLocalGenerators();
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for(unsigned int i = 0; i < lgens.size(); ++i)
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{
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cmTargets& targets = lgens[i]->GetMakefile()->GetTargets();
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for(cmTargets::iterator ti = targets.begin(); ti != targets.end(); ++ti)
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{
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cmTarget* target = &ti->second;
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int index = static_cast<int>(this->Targets.size());
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this->TargetIndex[target] = index;
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this->Targets.push_back(target);
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}
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}
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}
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//----------------------------------------------------------------------------
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void cmComputeTargetDepends::CollectDepends()
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{
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// Allocate the dependency graph adjacency lists.
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this->InitialGraph.resize(this->Targets.size());
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// Compute each dependency list.
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for(unsigned int i=0; i < this->Targets.size(); ++i)
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{
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this->CollectTargetDepends(i);
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}
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}
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//----------------------------------------------------------------------------
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void cmComputeTargetDepends::CollectTargetDepends(int depender_index)
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{
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// Get the depender.
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cmTarget* depender = this->Targets[depender_index];
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// Loop over all targets linked directly.
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{
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cmTarget::LinkLibraryVectorType const& tlibs =
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depender->GetOriginalLinkLibraries();
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std::set<cmStdString> emitted;
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// A target should not depend on itself.
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emitted.insert(depender->GetName());
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for(cmTarget::LinkLibraryVectorType::const_iterator lib = tlibs.begin();
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lib != tlibs.end(); ++lib)
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{
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// Don't emit the same library twice for this target.
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if(emitted.insert(lib->first).second)
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{
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this->AddTargetDepend(depender_index, lib->first.c_str(), true);
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}
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}
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}
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// Loop over all utility dependencies.
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{
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std::set<cmStdString> const& tutils = depender->GetUtilities();
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std::set<cmStdString> emitted;
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// A target should not depend on itself.
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emitted.insert(depender->GetName());
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for(std::set<cmStdString>::const_iterator util = tutils.begin();
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util != tutils.end(); ++util)
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{
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// Don't emit the same utility twice for this target.
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if(emitted.insert(*util).second)
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{
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this->AddTargetDepend(depender_index, util->c_str(), false);
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}
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}
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}
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}
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//----------------------------------------------------------------------------
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void cmComputeTargetDepends::AddTargetDepend(int depender_index,
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const char* dependee_name,
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bool linking)
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{
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// Get the depender.
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cmTarget* depender = this->Targets[depender_index];
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// Check the target's makefile first.
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cmTarget* dependee =
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depender->GetMakefile()->FindTarget(dependee_name);
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// Then search globally.
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if(!dependee)
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{
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dependee = this->GlobalGenerator->FindTarget(0, dependee_name);
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}
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// Skip targets that will not really be linked. This is probably a
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// name conflict between an external library and an executable
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// within the project.
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if(linking && dependee &&
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dependee->GetType() == cmTarget::EXECUTABLE &&
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!dependee->IsExecutableWithExports())
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{
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dependee = 0;
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}
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// If not found then skip then the dependee.
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if(!dependee)
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{
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return;
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}
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// No imported targets should have been found.
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assert(!dependee->IsImported());
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// Lookup the index for this target. All targets should be known by
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// this point.
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std::map<cmTarget*, int>::const_iterator tii =
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this->TargetIndex.find(dependee);
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assert(tii != this->TargetIndex.end());
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int dependee_index = tii->second;
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// Add this entry to the dependency graph.
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this->InitialGraph[depender_index].push_back(
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cmGraphEdge(dependee_index, !linking));
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}
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//----------------------------------------------------------------------------
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void
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cmComputeTargetDepends::DisplayGraph(Graph const& graph, const char* name)
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{
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fprintf(stderr, "The %s target dependency graph is:\n", name);
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int n = static_cast<int>(graph.size());
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for(int depender_index = 0; depender_index < n; ++depender_index)
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{
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EdgeList const& nl = graph[depender_index];
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cmTarget* depender = this->Targets[depender_index];
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fprintf(stderr, "target %d is [%s]\n",
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depender_index, depender->GetName());
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for(EdgeList::const_iterator ni = nl.begin(); ni != nl.end(); ++ni)
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{
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int dependee_index = *ni;
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cmTarget* dependee = this->Targets[dependee_index];
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fprintf(stderr, " depends on target %d [%s] (%s)\n", dependee_index,
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dependee->GetName(), ni->IsStrong()? "strong" : "weak");
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}
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}
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fprintf(stderr, "\n");
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}
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//----------------------------------------------------------------------------
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void
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cmComputeTargetDepends
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::DisplayComponents(cmComputeComponentGraph const& ccg)
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{
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fprintf(stderr, "The strongly connected components are:\n");
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std::vector<NodeList> const& components = ccg.GetComponents();
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int n = static_cast<int>(components.size());
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for(int c = 0; c < n; ++c)
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{
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NodeList const& nl = components[c];
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fprintf(stderr, "Component (%d):\n", c);
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for(NodeList::const_iterator ni = nl.begin(); ni != nl.end(); ++ni)
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{
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int i = *ni;
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fprintf(stderr, " contains target %d [%s]\n",
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i, this->Targets[i]->GetName());
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}
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}
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fprintf(stderr, "\n");
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}
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//----------------------------------------------------------------------------
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bool
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cmComputeTargetDepends
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::CheckComponents(cmComputeComponentGraph const& ccg)
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{
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// All non-trivial components should consist only of static
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// libraries.
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std::vector<NodeList> const& components = ccg.GetComponents();
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int nc = static_cast<int>(components.size());
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for(int c=0; c < nc; ++c)
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{
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// Get the current component.
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NodeList const& nl = components[c];
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// Skip trivial components.
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if(nl.size() < 2)
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{
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continue;
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}
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// Immediately complain if no cycles are allowed at all.
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if(this->NoCycles)
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{
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this->ComplainAboutBadComponent(ccg, c);
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return false;
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}
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// Make sure the component is all STATIC_LIBRARY targets.
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for(NodeList::const_iterator ni = nl.begin(); ni != nl.end(); ++ni)
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{
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if(this->Targets[*ni]->GetType() != cmTarget::STATIC_LIBRARY)
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{
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this->ComplainAboutBadComponent(ccg, c);
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return false;
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}
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}
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}
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return true;
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}
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//----------------------------------------------------------------------------
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void
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cmComputeTargetDepends
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::ComplainAboutBadComponent(cmComputeComponentGraph const& ccg, int c,
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bool strong)
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{
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// Construct the error message.
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cmOStringStream e;
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e << "The inter-target dependency graph contains the following "
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<< "strongly connected component (cycle):\n";
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std::vector<NodeList> const& components = ccg.GetComponents();
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std::vector<int> const& cmap = ccg.GetComponentMap();
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NodeList const& cl = components[c];
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for(NodeList::const_iterator ci = cl.begin(); ci != cl.end(); ++ci)
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{
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// Get the depender.
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int i = *ci;
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cmTarget* depender = this->Targets[i];
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// Describe the depender.
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e << " \"" << depender->GetName() << "\" of type "
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<< cmTarget::TargetTypeNames[depender->GetType()] << "\n";
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// List its dependencies that are inside the component.
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EdgeList const& nl = this->InitialGraph[i];
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for(EdgeList::const_iterator ni = nl.begin(); ni != nl.end(); ++ni)
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{
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int j = *ni;
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if(cmap[j] == c)
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{
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cmTarget* dependee = this->Targets[j];
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e << " depends on \"" << dependee->GetName() << "\""
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<< " (" << (ni->IsStrong()? "strong" : "weak") << ")\n";
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}
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}
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}
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if(strong)
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{
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// Custom command executable dependencies cannot occur within a
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// component of static libraries. The cycle must appear in calls
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// to add_dependencies.
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e << "The component contains at least one cycle consisting of strong "
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<< "dependencies (created by add_dependencies) that cannot be broken.";
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}
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else if(this->NoCycles)
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{
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e << "The GLOBAL_DEPENDS_NO_CYCLES global property is enabled, so "
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<< "cyclic dependencies are not allowed even among static libraries.";
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}
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else
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{
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e << "At least one of these targets is not a STATIC_LIBRARY. "
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<< "Cyclic dependencies are allowed only among static libraries.";
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}
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cmSystemTools::Error(e.str().c_str());
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}
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//----------------------------------------------------------------------------
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bool
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cmComputeTargetDepends
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::IntraComponent(std::vector<int> const& cmap, int c, int i, int* head,
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std::set<int>& emitted, std::set<int>& visited)
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{
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if(!visited.insert(i).second)
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{
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// Cycle in utility depends!
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return false;
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}
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if(emitted.insert(i).second)
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{
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// Honor strong intra-component edges in the final order.
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EdgeList const& el = this->InitialGraph[i];
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for(EdgeList::const_iterator ei = el.begin(); ei != el.end(); ++ei)
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{
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int j = *ei;
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if(cmap[j] == c && ei->IsStrong())
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{
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this->FinalGraph[i].push_back(j);
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if(!this->IntraComponent(cmap, c, j, head, emitted, visited))
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{
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return false;
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}
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}
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}
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// Prepend to a linear linked-list of intra-component edges.
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if(*head >= 0)
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{
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this->FinalGraph[i].push_back(*head);
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}
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else
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{
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this->ComponentTail[c] = i;
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}
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*head = i;
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}
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return true;
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}
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//----------------------------------------------------------------------------
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bool
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cmComputeTargetDepends
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::ComputeFinalDepends(cmComputeComponentGraph const& ccg)
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{
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// Get the component graph information.
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std::vector<NodeList> const& components = ccg.GetComponents();
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Graph const& cgraph = ccg.GetComponentGraph();
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// Allocate the final graph.
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this->FinalGraph.resize(0);
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this->FinalGraph.resize(this->InitialGraph.size());
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// Choose intra-component edges to linearize dependencies.
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std::vector<int> const& cmap = ccg.GetComponentMap();
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this->ComponentHead.resize(components.size());
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this->ComponentTail.resize(components.size());
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int nc = static_cast<int>(components.size());
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for(int c=0; c < nc; ++c)
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{
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int head = -1;
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std::set<int> emitted;
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NodeList const& nl = components[c];
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for(NodeList::const_reverse_iterator ni = nl.rbegin();
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ni != nl.rend(); ++ni)
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{
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std::set<int> visited;
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if(!this->IntraComponent(cmap, c, *ni, &head, emitted, visited))
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{
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// Cycle in add_dependencies within component!
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this->ComplainAboutBadComponent(ccg, c, true);
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return false;
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}
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}
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this->ComponentHead[c] = head;
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}
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// Convert inter-component edges to connect component tails to heads.
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int n = static_cast<int>(cgraph.size());
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for(int depender_component=0; depender_component < n; ++depender_component)
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{
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int depender_component_tail = this->ComponentTail[depender_component];
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EdgeList const& nl = cgraph[depender_component];
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for(EdgeList::const_iterator ni = nl.begin(); ni != nl.end(); ++ni)
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{
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int dependee_component = *ni;
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int dependee_component_head = this->ComponentHead[dependee_component];
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this->FinalGraph[depender_component_tail]
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.push_back(dependee_component_head);
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}
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}
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return true;
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}
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