MySQL C++ Connector crashes executing INSERT with BLOB

Question

I've stuck with a problem, trying to insert text as blob value, MySQL C++ connector crashed with exception: "Access violation reading location". I've seen questions like this here, but none has been answered. Here is a code sample:

 #include "mysql_connection.h"
#include <cppconn/driver.h>
#include <cppconn/exception.h>
#include <cppconn/resultset.h>
#include <cppconn/statement.h>
#include <cppconn/prepared_statement.h>

#include <string>
#include <iostream>
#include <sstream>

using namespace sql;

void main(){
    Connection  *dbConnection;
    Driver *driver;
    Connection *con;

    driver = get_driver_instance();
    con = driver->connect("localhost", "root", "");
    Statement *stmt = con->createStatement();
    try{
        stmt->execute("USE test");
        stmt->execute("DROP TABLE blob_test");
        stmt->execute("CREATE TABLE blob_test("
                        "id         INTEGER PRIMARY KEY NOT NULL AUTO_INCREMENT,"
                        "original   BLOB NOT NULL);");
        char smallBlob[32];

        for (char i = 0; i < sizeof(smallBlob); ++i)
        {
        smallBlob[i] = i;
        }
        std::istringstream str(smallBlob);
        PreparedStatement *pstmt = con->prepareStatement("INSERT INTO blob_test(id, original) VALUES (1, ?)");

        pstmt->setBlob( 1, &str);
        pstmt->executeUpdate();
    }catch(sql::SQLException &e){
        std::cerr << "# ERR: " << e.what();
        std::cerr << " (MySQL error code: " << e.getErrorCode();
        std::cerr << ", SQLState: " << e.getSQLState() << " )" << std::endl;
    }
}

Thanks in advance!

It doesn't matter, it's just a sample. And it's crashed on the line pstmt->executeUpdate(); I use VS2010 — Denis Makarskiy
– Denis Makarskiy, Commented Apr 2, 2013 at 18:49
Have a look at this example: stackoverflow.com/questions/1121142/…. I suspect that you do not really want to use istringstream as that operates on strings. E.g., your smallBlob[0] is a NULL. So, you may actually be inserting NULL data. Doesn't explain the crash, I know. — Blazes
– Blazes, Commented Apr 2, 2013 at 19:09
At which line does it crash? Did you put a breakpoint inside the catch statement? — Thomas Matthews
– Thomas Matthews, Commented Apr 2, 2013 at 19:45
@Blazes: I've seen the question you gave, I think I meet with the same problem and there was no answer. Thank you for your point that [0] element of the array is null, I've changed the line to smallBlob[i] = 50 + i; and now smallBlob contains '23456789:;<=>?@ABCDEFGHIJKLMNOPQ' according to debug info before crash. To Thomas Mattews: Catch statement haven't reached, because exception is unhandled: Unhandled exception at 0x74d3eab7 in testMySQLblob.exe: 0xC0000005: Access violation reading location 0x00000000. — Denis Makarskiy
– Denis Makarskiy, Commented Apr 2, 2013 at 19:58

Community · Accepted Answer · 2017-05-23 12:28:07Z

0

Problem solved compiling MySQL cpp connector from sources.

If you go that way read carefully this and this (specially comments in the end). I also had to changed a couple of lines in config.h to implicit cast of int to char*. Also be attentive don't mix Debug and Release, for example if you compile your application in Debug, you should link Debug version of MySQL connector and vice-a-verse.

After I linked lib that I had compiled everything launched ) You may read on dev.mysql.com forums that in most cases it's the only way force the connector to work. While compiling I met with the thing that prove this, include files in source code is different from includes in windows binary distributive.

edited May 23, 2017 at 12:28

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answered Apr 12, 2013 at 11:38

Denis Makarskiy

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