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/********************* */
/** node_manager.cpp
** Original author: mdeters
** Major contributors: none
** Minor contributors (to current version): dejan, taking
** This file is part of the CVC4 prototype.
** Copyright (c) 2009, 2010 The Analysis of Computer Systems Group (ACSys)
** Courant Institute of Mathematical Sciences
** New York University
** See the file COPYING in the top-level source directory for licensing
** information.
**
** Expression manager implementation.
**
** Reviewed by Chris Conway, Apr 5 2010 (bug #65).
**/
#include "node_manager.h"
#include <ext/hash_set>
using namespace std;
using namespace CVC4::expr;
using __gnu_cxx::hash_set;
namespace CVC4 {
__thread NodeManager* NodeManager::s_current = 0;
NodeManager::NodeManager(context::Context* ctxt) :
d_attrManager(ctxt),
d_nodeUnderDeletion(NULL),
d_reclaiming(false) {
poolInsert( &expr::NodeValue::s_null );
for(unsigned i = 0; i < unsigned(kind::LAST_KIND); ++i) {
Kind k = Kind(i);
if(hasOperator(k)) {
d_operators[i] = mkConst(Kind(k));
}
}
}
NodeManager::~NodeManager() {
// have to ensure "this" is the current NodeManager during
// destruction of operators, because they get GCed.
NodeManagerScope nms(this);
for(unsigned i = 0; i < unsigned(kind::LAST_KIND); ++i) {
d_operators[i] = Node::null();
}
while(!d_zombies.empty()) {
reclaimZombies();
}
poolRemove( &expr::NodeValue::s_null );
}
/**
* This class ensures that NodeManager::d_reclaiming gets set to false
* even on exceptional exit from NodeManager::reclaimZombies().
*/
struct Reclaim {
bool& d_reclaimField;
Reclaim(bool& reclaim) :
d_reclaimField(reclaim) {
Debug("gc") << ">> setting RECLAIM field\n";
d_reclaimField = true;
}
~Reclaim() {
Debug("gc") << "<< clearing RECLAIM field\n";
d_reclaimField = false;
}
};
/**
* Similarly, ensure d_nodeUnderDeletion gets set to NULL even on
* exceptional exit from NodeManager::reclaimZombies().
*/
struct NVReclaim {
NodeValue*& d_deletionField;
NVReclaim(NodeValue*& deletionField) :
d_deletionField(deletionField) {
Debug("gc") << ">> setting NVRECLAIM field\n";
}
~NVReclaim() {
Debug("gc") << "<< clearing NVRECLAIM field\n";
d_deletionField = NULL;
}
};
void NodeManager::reclaimZombies() {
// FIXME multithreading
Debug("gc") << "reclaiming " << d_zombies.size() << " zombie(s)!\n";
// during reclamation, reclaimZombies() is never supposed to be called
Assert(! d_reclaiming, "NodeManager::reclaimZombies() not re-entrant!");
// whether exit is normal or exceptional, the Reclaim dtor is called
// and ensures that d_reclaiming is set back to false.
Reclaim r(d_reclaiming);
// We copy the set away and clear the NodeManager's set of zombies.
// This is because reclaimZombie() decrements the RC of the
// NodeValue's children, which may (recursively) reclaim them.
//
// Let's say we're reclaiming zombie NodeValue "A" and its child "B"
// then becomes a zombie (NodeManager::markForDeletion(B) is called).
//
// One way to handle B's zombification would be simply to put it
// into d_zombies. This is what we do. However, if we were to
// concurrently process d_zombies in the loop below, such addition
// may be invisible to us (B is leaked) or even invalidate our
// iterator, causing a crash. So we need to copy the set away.
vector<NodeValue*> zombies;
zombies.reserve(d_zombies.size());
std::copy(d_zombies.begin(),
d_zombies.end(),
std::back_inserter(zombies));
d_zombies.clear();
for(vector<NodeValue*>::iterator i = zombies.begin();
i != zombies.end();
++i) {
NodeValue* nv = *i;
// collect ONLY IF still zero
if(nv->d_rc == 0) {
Debug("gc") << "deleting node value " << nv
<< " [" << nv->d_id << "]: " << *nv << "\n";
// remove from the pool
if(nv->getKind() != kind::VARIABLE) {
poolRemove(nv);
}
// whether exit is normal or exceptional, the NVReclaim dtor is
// called and ensures that d_nodeUnderDeletion is set back to
// NULL.
NVReclaim rc(d_nodeUnderDeletion);
d_nodeUnderDeletion = nv;
// remove attributes
d_attrManager.deleteAllAttributes(nv);
// decr ref counts of children
nv->decrRefCounts();
free(nv);
}
}
}/* NodeManager::reclaimZombies() */
}/* CVC4 namespace */
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