CentOS6.9 (MySql v5.7.22) use mysql C API mysql_real_query cause the memory always growing

[normga]

I test the mysql_real_query API, I just loop to execute Sql syntax ,like 'UPDATE ** SET **' there is a leak memory bug occur. when I use 'top' to check the bug, I find the system 'used memory' option will always growing until the system or process crush. but 'mysqld' and 'testsql' processes's %MEM option has not increase, System free memory look like disappear. I try to force kill the 'testsql' process but the memory still be used and can not be release. Why? Please help me.

int ThreadExeSQL(MYSQL* lpSQLConn, char * sql, int iLen)
{

if (mysql\_real\_query(lpSQLConn, sql, iLen))
{
    MYSQL\_RES\* lpGetSQLRes = mysql\_store\_result(lpSQLConn);
    mysql\_free\_result(lpGetSQLRes);
    return -1;
}

//mysql\_errno(lpSQLConn);
//mysql\_error(lpSQLConn);

MYSQL\_RES\* lpGetSQLRes = mysql\_store\_result(lpSQLConn);
mysql\_free\_result(lpGetSQLRes); // release sql memory

return 0; // success

}

void* ThreadSQL_HexWrite(void* lpGet)
{

LPThreadParam getParam = (LPThreadParam)lpGet;

MYSQL\* lpSQLConn = (MYSQL\*)&getParam->lpSQLConn;
int iThreadIdx = getParam->iThreadIdx;

printf("ID:%d\\n", iThreadIdx);

mysql\_thread\_init();

lpSQLConn = mysql\_init(NULL);


if (!mysql\_real\_connect(lpSQLConn, g\_host\_name, g\_user\_name, g\_password, g\_db\_name, g\_db\_port, NULL, 0))
{
    ThreadSQLError(lpSQLConn, NULL);
    return;
}
else
{
    printf("mysql\_real\_connect OK!\\n");
}


for (int i = 0; i < 1000000; i++)
{

    char lpCmdStr\[8192\] = "\\0";
    sprintf(lpCmdStr, "update %s set %s=0x%d where id=%d\\0", "tb\_Data", "Info", i, 1);

    if (ThreadExeSQL(lpSQLConn, (char\*)lpCmdStr, strlen(lpCmdStr)))
    {
        MySQLError getError = ThreadSQLError(lpSQLConn, NULL);
        HandleMySqlError(getError);

        continue; //erroe
    }
    else
    {
        printf("ok. ");
    }

    usleep(1000 \* 10);
}

mysql\_close(lpSQLConn);

mysql\_thread\_end();


printf("ThreadSQL\_HexWrite OK!\\n");

}

MYSQL* g_MySQLConnList[100];

void main()
{

if (mysql\_library\_init(0, NULL, NULL))
{
    printf("could not initialize MySQL client library\\n");
    exit(1);
}


int thread\_num = 1;

//while (true)
{
    pthread\_t \*pTh = new pthread\_t\[thread\_num\];


    for (int i = 0; i < thread\_num; i++)
    {

        LPThreadParam lpSetPar

[jschell]

Doesn't seem like the code is complete.

normga wrote:

MYSQL* g_MySQLConnList[100];

That is a list of uninitialized pointers. Where do those pointers get set to actually point to something?

[normga]

yes. g_MySQLConnList fill with like 'new MYSQL[100]'; In fact, in my testing environment the code always query mysql successful, but leak memory.

[jschell]

Perhaps you missed my point. You have a list of pointers. Nothing more. The pointer must be set to point to something. Where does that happen?

normga wrote:

the code always query mysql successful

That doesn't mean anything. Code can run successfully, sometimes, even with uninitialized pointers. It depends on how the memory is laid down.