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      1 // gc.cc -- garbage collection of unused sections
      2 
      3 // Copyright (C) 2009-2016 Free Software Foundation, Inc.
      4 // Written by Sriraman Tallam <tmsriram (at) google.com>.
      5 
      6 // This file is part of gold.
      7 
      8 // This program is free software; you can redistribute it and/or modify
      9 // it under the terms of the GNU General Public License as published by
     10 // the Free Software Foundation; either version 3 of the License, or
     11 // (at your option) any later version.
     12 
     13 // This program is distributed in the hope that it will be useful,
     14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
     15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     16 // GNU General Public License for more details.
     17 
     18 // You should have received a copy of the GNU General Public License
     19 // along with this program; if not, write to the Free Software
     20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
     21 // MA 02110-1301, USA.
     22 
     23 
     24 #include "gold.h"
     25 #include "object.h"
     26 #include "gc.h"
     27 #include "symtab.h"
     28 
     29 namespace gold
     30 {
     31 
     32 // Garbage collection uses a worklist style algorithm to determine the
     33 // transitive closure of all referenced sections.
     34 void
     35 Garbage_collection::do_transitive_closure()
     36 {
     37   while (!this->worklist().empty())
     38     {
     39       // Add elements from the work list to the referenced list
     40       // one by one.
     41       Section_id entry = this->worklist().back();
     42       this->worklist().pop_back();
     43       if (!this->referenced_list().insert(entry).second)
     44         continue;
     45       Garbage_collection::Section_ref::iterator find_it =
     46                 this->section_reloc_map().find(entry);
     47       if (find_it == this->section_reloc_map().end())
     48           continue;
     49       const Garbage_collection::Sections_reachable &v = find_it->second;
     50       // Scan the vector of references for each work_list entry.
     51       for (Garbage_collection::Sections_reachable::const_iterator it_v =
     52                v.begin();
     53            it_v != v.end();
     54            ++it_v)
     55         {
     56           // Do not add already processed sections to the work_list.
     57           if (this->referenced_list().find(*it_v)
     58               == this->referenced_list().end())
     59             {
     60               this->worklist().push_back(*it_v);
     61             }
     62         }
     63     }
     64   this->worklist_ready();
     65 }
     66 
     67 } // End namespace gold.
     68 
     69