FreeTDS Development Group

[Craig Davison <cd AT securityfocus.com>]

Hi again,

I discovered a memory leak in the application I'm developing, and I think 
I may have traced the problem to either the Freetds ODBC driver or 
unixODBC. Of course, it's possible I'm not explicity freeing something 
that I should.

Sample code that compiles on my RedHat 8 (x86) machine is attached 
(change the connection parameters in main() to try it out). Here's what 
I'm doing, in pseudocode:

SQLAllocHandle(SQL_NULL_HANDLE,hEnv)
SQLAllocHandle(hEnv,hDbc)
SQLConnect(hDbc,...)
Loop:
        SQLAllocHandle(hDbc,hStmt)
        SQLBindCol(hStmt,...)
        SQLExecDirect(hStmt,...)
        SQLFetch(hStmt) . . . .
        SQLFreeStmt(hStmt)
        SQLFreeHandle(hStmt)
SQLDisconnect(hDbc)
SQLFreeHandle(hDbc)
SQLFreeHandle(hEnv)

The inner loop seems to leave 8 k unfreed ever time it is run.

To see the memory leak, run top or something alongside it and watch the 
process grow by 8 k per second.

BTW my server is SQLServer 2000, and I'm using unixODBC 2.2.2.

-- 
Craig Davison
Symantec Corporation
+1 (403) 213-3939 ext. 228
#include <stdio.h>
#include <sql.h>
#include <sqlext.h>
#include <sqltypes.h>

int TryQuery (SQLHDBC hOdbc)
{
        SQLINTEGER SQLid;
        SQLINTEGER SQLerr;
        long erg;
        SQLHSTMT hStmt;
        char pQuery[501];

        SQLAllocHandle(SQL_HANDLE_STMT, hOdbc, &hStmt);
        sprintf (pQuery, "SELECT uid FROM master..sysusers WHERE uid=0");
        printf ("query: %s\n", pQuery);
        SQLBindCol(hStmt, 1, SQL_C_SLONG, &SQLid, sizeof(SQLINTEGER), 
&SQLerr);
        erg = SQLExecDirect (hStmt, pQuery, SQL_NTS);
        if (erg != SQL_SUCCESS)
        {
                printf ("ERROR\n");
                SQLFreeHandle(SQL_HANDLE_STMT, &hStmt);
                return 0;
        }
        erg = SQLFetch (hStmt);
        while (erg == SQL_SUCCESS)
        {
                printf ("Data: %d\n", (int)SQLid);
                erg = SQLFetch (hStmt);
        }
        if (erg != SQL_NO_DATA)
        {
                printf ("ERROR\n");
                SQLFreeStmt (hStmt, SQL_CLOSE);
                SQLFreeHandle(SQL_HANDLE_STMT, &hStmt);
                return 0;
        }
        SQLFreeStmt (hStmt, SQL_CLOSE);
        SQLFreeHandle(SQL_HANDLE_STMT, &hStmt);

        return 1;
}

int main (int argc, char **argv)
{
        SQLHENV hEnv;
        SQLHDBC hOdbc;
        long erg;

        SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &hEnv);
        SQLSetEnvAttr(hEnv, SQL_ATTR_ODBC_VERSION, (void*)SQL_OV_ODBC3, 0);
        SQLAllocHandle(SQL_HANDLE_DBC, hEnv, &hOdbc);

        /* connect to the database */
        erg = SQLConnect(hOdbc, (SQLCHAR*) "server", SQL_NTS,
                        (SQLCHAR*) "user", SQL_NTS,
                        (SQLCHAR*) "pass", SQL_NTS);
        if (erg != SQL_SUCCESS)
        {
                printf ("Database Connect Error\n");
                SQLFreeHandle(SQL_HANDLE_DBC, &hOdbc);
                SQLFreeHandle(SQL_HANDLE_ENV, &hEnv);
                return 0;
        }

        while (TryQuery (hOdbc))
                sleep (1);

        SQLDisconnect(hOdbc);
        SQLFreeHandle(SQL_HANDLE_DBC, &hOdbc);
        SQLFreeHandle(SQL_HANDLE_ENV, &hEnv);

        return 0;
}