C++ - SQLite3 leaks handles in multithread environment - c++

Question

I wrote a simple program that spawns 10 threads, each thread opens a database (common to all the threads), or creates it (with "Write-Ahead Log" option) if open fails, creates a table on the database and then it goes into an infinite loop in which it adds one row at the time into its table. I found out that the program leaks about 2 handles every 5 minutes, I tried a tool called Memory Verify which tells me that the leaked handles are SQLite3 file locks (line 34034 on the version 3.7.13) but I am not sure whether the bug is in SQLite or in the way I use it.
I haven't specified any compiler option to build SQLite3 so it is built as Multi-Thread and as far as I understand Multi-Thread should work fine in my case as every threads has its own SQLite connection.
To open or create a database I use the following code:
bool Create()
{
int iFlags = 0;
iFlags = iFlags | SQLITE_OPEN_READWRITE | SQLITE_OPEN_NOMUTEX | SQLITE_OPEN_CREATE;
return sqlite3_open_v2(dbName_sm.c_str(), &pHandle_m, iFlags, 0) == SQLITE_OK;
}
bool Open()
{
int iFlags = 0;
iFlags = iFlags | SQLITE_OPEN_READWRITE | SQLITE_OPEN_NOMUTEX;
return sqlite3_open_v2(dbName_sm.c_str(), &pHandle_m, iFlags, 0) == SQLITE_OK;
}
The hard loop in every thread calls ExecuteQuery which does prepare, step and finalize of an INSERT statement:
bool ExecuteQuery(const std::string& statement)
{
bool res = Prepare(statement);
if(!res)
{
return false;;
}
SQLiteStatus status = Step();
Finalize();
res = (ESuccess == status || EDatabaseDone == status);
return res;
}
bool Prepare(const std::string& statement)
{
return sqlite3_prepare_v2(pHandle_m, statement.c_str(), -1, &pStmt_m, 0) == SQLITE_OK;
}
enum SQLiteStatus { ESuccess, EDatabaseDone, EDatabaseTimeout, EDatabaseError };
SQLiteStatus Step()
{
int iRet = sqlite3_step(pStmt_m);
if (iRet == SQLITE_DONE)
{
return EDatabaseDone;
}
else if (iRet == SQLITE_BUSY)
{
return EDatabaseTimeout;
}
else if (iRet != SQLITE_ROW)
{
return EDatabaseError;
}
return ESuccess;
}
bool Finalize()
{
int iRet = sqlite3_finalize(pStmt_m);
pStmt_m = 0;
return iRet == SQLITE_OK;
}
Do you guys see any mistake in my code or is it a known issue in SQLite? I tried to google it for a couple of days but I couldn't find anything about it.
Thank you very much for your help.
Regards,
Andrea
P.S. I forgot to say that I am running my test on a WinXP 64bit PC, the compiler is VS2010, the application is compiled in 32bit, SQLite version is 3.7.13...

Answer 1

check whether you have sqlite3_reset after every sqlite3_step because this is one case that might causes leaks. after preparing a statement with sqlite3_prepare and executing it with sqlite3_step,you need to always reset it with sqlite3_reset.