[Boost-users] hash set crashing during iteration (boost 1.35.0)

14 May 2008

      Hello,

I'm using boost 1.35.0 and found this sample code about the hash set
functionality:

http://www.boost.org/doc/libs/1_35_0/doc/html/intrusive/advanced_lookups_ins...

and modified it as shown below.  I find that when iterating through
the hash table, the thing crashes here (where the get_next function
contains an invalid value for n):

template<class VoidPointer> struct slist_node_traits
{
....
   static node_ptr get_next(const_node_ptr n)
---------->   {  return n->next_;  }
....
};

Should I use an earlier more stable version of boost or am I doing
something dreadfully wrong?

Thank you for any insights
-Julie

#include <stdio.h>
#include <string>
#include <iostream>               // for std::cout
#include <boost/foreach.hpp>
#include <boost/intrusive/unordered_set.hpp>

using namespace boost::intrusive;

struct CStringHasher
{
	std::size_t operator()(const std::string& str) const
	{
		std::size_t seed = 0;
		const char* sz = str.c_str();
		if ( ! sz )
			return seed;
		for(; *sz; ++sz)
			boost::hash_combine(seed, *sz);
		return seed;
	}
};

class CWord : public unordered_set_base_hook<>
{               //This is a derivation hook
public:
	std::string m_strWord;
	int m_nID;

	unordered_set_member_hook<> member_hook_; //This is a member hook

	CWord( const std::string& strWord, int nID ) : m_strWord( strWord ),
m_nID( nID ) {}

	friend bool operator== (const CWord& a, const CWord& b)
	{  return a.m_strWord == b.m_strWord;  }

	friend std::size_t hash_value(const CWord& value)
	{  return CStringHasher()(value.m_strWord.c_str());  }
};

class CWordHash
{
public:
	typedef unordered_set<CWord>			word_hash_set;
	typedef word_hash_set::bucket_type		word_bucket_type;
	typedef word_hash_set::bucket_traits	word_bucket_traits;
	typedef word_hash_set::iterator			word_iter;

	CWordHash() : m_hWords( word_bucket_traits( m_Buckets, s_nNumBuckets ) ) {}
	~CWordHash()
	{
		BOOST_FOREACH( CWord& w, m_hWords )
		{
			CWord* pWord = &w;
			delete pWord;
		}
	}

	struct CStrExpensiveClassEqual
	{
	   bool operator()(const std::string& str, const CWord &c) const {
return str == c.m_strWord;  }
	   bool operator()(const CWord& c, const std::string& str) const {
return str == c.m_strWord;  }
	};

	CWord* get( const std::string& str )
	{
		word_iter it = m_hWords.find( str, CStringHasher(),
CStrExpensiveClassEqual());

		if( it == m_hWords.end() )
			return NULL;

		return &*it;
	}	

	bool insert( const std::string& strKey, int nID )
	{
		word_hash_set::insert_commit_data insert_data;
		bool bSuccess = m_hWords.insert_check( strKey, CStringHasher(),
CStrExpensiveClassEqual(), insert_data).second;
		if ( bSuccess )
		{
			CWord* pWord = new CWord(strKey, nID);
			m_hWords.insert_commit(*pWord, insert_data);
		}
		return bSuccess;
	}

	static const int s_nNumBuckets = 10000;
	word_bucket_type				m_Buckets[s_nNumBuckets];
	word_hash_set					m_hWords;
};

extern int main(int argc, char *argv[])
{
	CWordHash hWords; // hash string to word id
	int nID = 1;
	std::string strWord = "hello";
	hWords.insert( strWord, nID );
	nID = 2;
	strWord = "world";
	hWords.insert( strWord, nID );

	for ( CWordHash::word_hash_set::iterator it =
hWords.m_hWords.begin(); it != hWords.m_hWords.end(); it++ )
	{
		CWord& w = *it;
		std::cout << w.m_strWord << "\t" << w.m_nID << "\n";
	}

	return 0;
}

[Boost-users] hash set crashing during iteration (boost 1.35.0)

Julie Larson