vs2012: SQLite: Access violation reading location 0x0000000C

问题

I am implementing SQLite Prepare-Statement in vs2012 using C.

I am using this link as a tutorial to capture the processes that are running in my machine every time I run my code. Everything is working fine except that the prepare-statement does not allow me to put it outside the do-while loop. if I put it inside the do-while loop then I am doing nothing actually because with every db-insertion the prepare-statement is again executed which is not practical. however, when I put the prepare-statement inside the do-while loop and run the code, it works fine(but it runs as many insertion I have to insert). and when I put outside the do-while loop it gives me a memory warning and break.

here is how I am implementing the SQLite:

BOOL GetProcessList(sqlite3 *db)
{
  HANDLE hProcessSnap;
  HANDLE hProcess;
  PROCESSENTRY32 pe32;
  DWORD dwPriorityClass;
  sqlite3_stmt* stmt;
  char *errorMessage;  
  char query[80] = "INSERT INTO Process_list VALUES (?1, ?2, ?3, ?4, ?5);";

  // Take a snapshot of all processes in the system.
  hProcessSnap = CreateToolhelp32Snapshot( TH32CS_SNAPPROCESS, 0 );

  if( hProcessSnap == INVALID_HANDLE_VALUE )
  {
    printError( TEXT("CreateToolhelp32Snapshot (of processes)") );
    return( FALSE );
  }

  // Set the size of the structure before using it.
  pe32.dwSize = sizeof( PROCESSENTRY32 );

  // Retrieve information about the first process,
  // and exit if unsuccessful
  if( !Process32First( hProcessSnap, &pe32 ) )
  {
    printError( TEXT("Process32First") ); // show cause of failure
    CloseHandle( hProcessSnap );          // clean the snapshot object
    return( FALSE );
  }

  // Now walk the snapshot of processes, and
  // display information about each process in turn

  sqlite3_exec(db, "CREATE TABLE IF NOT EXISTS Process_list("  
    "Process_ID     INT PRIMARY KEY     , " 
    "Thread_count       INT     ,   "
    "Parent_PID     INT     ,   "
    "Priority_Base      INT     ,   " 
    "Priority_class INT     );", NULL, NULL, &errorMessage);

    sqlite3_prepare_v2(db, query,strlen(query), &stmt,NULL); // can't put it here

  do
  {
    _tprintf( TEXT("\n\n=====================================================" ));
    _tprintf( TEXT("\nPROCESS NAME:  %s"), pe32.szExeFile );
    _tprintf( TEXT("\n-------------------------------------------------------" ));

    // Retrieve the priority class.
    dwPriorityClass = 0;
    hProcess = OpenProcess( PROCESS_ALL_ACCESS, FALSE, pe32.th32ProcessID );
    if( hProcess == NULL )
    {
      printError( TEXT("OpenProcess") );
    } else {
        dwPriorityClass = GetPriorityClass( hProcess );
        if( !dwPriorityClass )
        {
            printError( TEXT("GetPriorityClass") );
        }
        CloseHandle( hProcess );
    }

    _tprintf( TEXT("\n  Process ID        = 0x%08X"), pe32.th32ProcessID );
    _tprintf( TEXT("\n  Thread count      = %d"),   pe32.cntThreads );
    _tprintf( TEXT("\n  Parent process ID = 0x%08X"), pe32.th32ParentProcessID );
    _tprintf( TEXT("\n  Priority base     = %d"), pe32.pcPriClassBase );
    if( dwPriorityClass )
      _tprintf( TEXT("\n  Priority class    = %d"), dwPriorityClass );
    _tprintf( TEXT("\n"));

    //-------------------------------------------------------------------------------
    // database insertion of the process information    
    sqlite3_bind_int64(stmt,1,pe32.th32ProcessID);
    sqlite3_bind_int64(stmt,2,pe32.cntThreads);
    sqlite3_bind_int64(stmt,3,pe32.th32ParentProcessID);
    sqlite3_bind_int64(stmt,4,pe32.pcPriClassBase);
    sqlite3_bind_int64(stmt,5,dwPriorityClass); 
    if(sqlite3_step(stmt) != SQLITE_DONE)
        printf("\nPrepare statement failed!\n");
    sqlite3_reset(stmt);                        // the error appears here
    sqlite3_finalize(stmt);
    //-------------------------------------------------------------------------------

    // List the modules and threads associated with this process
    ListProcessModules( pe32.th32ProcessID,db );
    ListProcessThreads( pe32.th32ProcessID,db );

  } while( Process32Next( hProcessSnap, &pe32 ) );

  CloseHandle( hProcessSnap );
  return( TRUE );
}

so when I run the code, it shows me this:

so why is this happening and how to avoid this memory exception ? thanks

回答1:

1. You must check the return value of all functions, especially sqlite3_prepare_v2. (And if you get an error, call sqlite3_errmsg to get a usefull error message.)
2. You can use a prepared statement multiple times, and you must call sqlite3_reset before reusing it, which you are doing correctly. However, sqlite3_finalize frees the statement entirely; you must call this after the loop.

来源：https://stackoverflow.com/questions/18656053/vs2012-sqlite-access-violation-reading-location-0x0000000c